Trial watch: beta-blockers in cancer therapy

ABSTRACT Compelling evidence supports the hypothesis that stress negatively impacts cancer development and prognosis. Irrespective of its physical, biological or psychological source, stress triggers a physiological response that is mediated by the hypothalamic-pituitary-adrenal axis and the sympathetic adrenal medullary axis. The resulting release of glucocorticoids and catecholamines into the systemic circulation leads to neuroendocrine and metabolic adaptations that can affect immune homeostasis and immunosurveillance, thus impairing the detection and eradication of malignant cells. Moreover, catecholamines directly act on β-adrenoreceptors present on tumor cells, thereby stimulating survival, proliferation, and migration of nascent neoplasms. Numerous preclinical studies have shown that blocking adrenergic receptors slows tumor growth, suggesting potential clinical benefits of using β-blockers in cancer therapy. Much of these positive effects of β-blockade are mediated by improved immunosurveillance. The present trial watch summarizes current knowledge from preclinical and clinical studies investigating the anticancer effects of β-blockers either as standalone agents or in combination with conventional antineoplastic treatments or immunotherapy.


Introduction
Stress typically leads to the co-activation of the hypothalamicpituitary-adrenal (HPA) axis and the sympathetic adrenal medullary (SAM) axis, resulting in the systemic elevation of stress hormones, namely glucocorticoids produced by the adrenal cortex and catecholamines (including epinephrine and norepinephrine) that are released from the adrenal medulla into the circulation. 1,2Catecholamines act on adrenergic receptors (ARs), thus increasing heart rate and blood pressure to prepare the organism for a fight-or-flight response. 3ARs belong to the G-protein-coupled receptor super-family and are categorized into α-and β-ARs based on their location and function.α-ARs are divided into two classes: α1-AR, predominantly found on blood vessels, which increase blood pressure upon activation, and α2-AR, mainly located within solid organs such as the pancreas, where they control insulin synthesis.β-receptors can be further classified into three types: β1-AR (found in the heart, blood vessels, kidney, and ciliary muscle), β2-AR (located in the lungs and ciliary muscle), and β3-AR (present only in smooth muscle tissue).β-ARs play a major role in stimulating cardiovascular functions and promoting the relaxation of the smooth muscles in bronchi and blood vessels.Table 1 β-blockers are specific antagonists targeting β-ARs.The first synthetic molecules dichloroisoprenaline and pronethalol were derived from epinephrine in the late 1950s, but were withdrawn from clinical use several years later due to severe cardiotoxic side effects. 4However, in 1962, propranolol, a non-cardioselective agent that targets both β1 and β2 receptors, was found to promote negative chronotropic, bathmotropic, inotropic, and dromotropic cardiac effects and a decrease in kidney renin production (resulting in decreased blood pressure), thus providing safe clinical use. 5 Subsequently, cardioselective agents including acebutolol, atenolol, bisoprolol, and nebivolol were introduced.These agents specifically target β1-ARs, thus limiting side effects such as vaso-and bronchoconstriction.Currently, β-blockers are broadly used in clinical practice, primarily for regulating dysrhythmia, and arterial hypertension, preventing heart attacks and migraines, as well as for treating glaucoma.However, misuse of these agents can cause severe hypotension, bradycardia, asthenia, asthma or Raynaud's syndrome, and contraindications, such as cardiac conduction disturbances or chronic obstructive pulmonary disease have to be respected.Table 1 β-blockers can be subdivided into two pharmacological classes: phenylethanolamines and aryloxypropanolamines.Phenylethanolamines are composed of an aromatic group linked to an ethylamine substituted by a hydroxyl on position 1. β -blockers of this class such as sotalol or labetalol are noncardioselective and act on-target on β1 receptors while often causing off-target β2 receptor-mediated side effects.Compounds from the group of aryloxypropanolamines including carvedilol, nebivolol and propafenone possess an aromatic group linked to a propylamine substituted by a hydroxyl on Table 1.Adrenergic receptors and their main agonists and antagonists in clinic use (non-exhaustive list).position 2 and have an additional methyl group on the amine chain, which increases their activity and selectivity.Of note, the size of the aromatic group of a β-blocker determines its ability to activate adrenergic receptors.Thus, a small aromatic group as the one of epinephrine allows activation of adrenergic receptors, whereas a voluminous group such as the one of pronethalol induces an antagonistic effect.Moreover, a β-blocker becomes cardioselective if its activity on β1 receptors is higher than that on β2 receptors.Agonistic activity on β1 receptor allows vasodilatation that decreases blood pressure, while activating β2 promotes side effects such as bronchoconstriction.This selectivity is due to a hydrogen group inducing a preferential interaction with the β1 receptor.Cardioselective β-blockers include acebutolol, atenolol, bisoprolol, and nebivolol, while the most employed non-cardioselective β-blockers are propranolol, sotalol and timolol.(Figure 1) Surgical removal of the primary tumor plays a crucial role in improving the overall survival of cancer patients.However, the physical excision of the tumor by the surgeon can release circulating tumor cells, which can spread micrometastases to distant organs.Additionally, surgical procedures can cause stress such as pain, nociception, inflammation, and tissue damage, which in turn trigger a cascade of local and systemic signaling pathways, activating corticotropic signaling.This results in the secretion of adrenocorticotropic hormone (ACTH), catecholamines, and cortisol, proportional to the stress caused during surgery, leading to critical neuroendocrine and metabolic changes known as 'glucocorticoid stress'. 6,7oreover, stress hormones released into the systemic circulation can negatively impact both humoral and cellular immunity. 8,92][13] Moreover, glucocorticoid stress can impact type I interferon (IFN) production by dendritic cells, as well as the release of IFN-γ by cytotoxic T lymphocytes (CTLs), thus broadly compromising adaptive antitumor immune responses. 14,15Studies in a rat mammary adenocarcinoma model also showed that injection of catecholamines inhibited NK cell-mediated tumor lysis and suppressed resistance to NKsensitive metastasis. 16Furthermore, endogenous stress hormones have been shown to activate β2-ARs and downstream cAMP-PKA signaling pathways that increased the activity of matrix metalloproteinases (MMP), further promoting the dissemination of malignant cells.8][19][20] In a murine model of pancreatic cancer, chronic stress increased levels of circulating steroids and adrenal tyrosine resulting in impaired immune responses, with a decreased response of ex vivo splenocytes to lipopolysaccharide, a decrease in cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expression in CD4 + cells, and an increase in regulatory T cells in the tumor bed, altogether stimulating tumor growth and impacting on overall survival. 21In yet another study using a murine model of MDA-MB-231 breast cancer, stress-induced epinephrine production was found to promote tumor growth in a time-and concentration-dependent manner. 22Additionally, in an observational retrospective trial, Cox regression analysis revealed low serum epinephrine as a predictor of positive prognosis.Thus, breast cancer patients with low serum epinephrine levels had a significantly better overall (OS) and disease-free survival (DFS) compared to patients with high epinephrine levels. 22urprisingly, colon cancer cells are also able to produce immunoregulatory glucocorticoids to suppress the activation of immune cells.Finally, many data support that both endogenous as well as exogenous corticoids might diminish therapiesinduced anti-tumor response.In summary, while oncological interventions are crucial for achieving remission in clinical routine, they paradoxically decrease the immunosurveillance necessary to avoid immune escape thus promoting the development of secondary lesions due to 'glucocorticoid stress'. 14,23,24sychosocial stress has been suggested as a putative cause of cancer incidence and mortality for a long time, however, determining a cause-effect relationship has been challenging and was not firmly established. 25The influence of persistent corticotropic signaling on major antitumor immunological effectors, such as NK cells, dendritic cells (DC), and T-lymphocytes, has been explored through various approaches. 26T lymphocytes obtained from the serum of stressed individuals exhibited a shift in phenotype from Th1 to Th2, potentially affecting immune signaling pathways. 27Moreover, in both animal models and human studies, psychosocial stress was found to negatively impact NK cell activity and promote tumor growth.In a murine colon carcinoma model, social isolation stress decreased splenic NK cell activity while increasing angiogenesis leading to the formation of secondary tumors. 28,29Conversely, NK cells from ovarian cancer patients became more efficient at lysing tumor cells after receiving psychosocial support during the perioperative period. 30Furthermore, preclinical data suggest that psychosocial stress activates β-adrenergic signaling and promotes tumor progression.Thus, in a murine hepatocellular carcinoma model, restraint stress promoted tumor growth and increased norepinephrine levels through β-adrenergic signaling. 31In an orthotopic ovarian carcinoma model, mice subjected to restraint stress experienced increased tumor growth and VEGF-mediated vascularization, which correlated with the level of circulating stress hormones.However, premedication with propranolol, a β-blocker with anxiolytic properties, reversed the tumor-promoting effects. 11imilar results were observed in mice exposed to psychosocial stress through crowded or isolated housing conditions where stress-enhanced melanoma and fibrosarcoma growth was decreased by the oral administration of propranolol. 32In a social defeat model in mice; we observed stress-elevated plasma corticosterone levels and an increase in the expression of glucocorticoid-inducible factor Tsc22d3 that blocked type I Interferon (IFN) responses in dendritic cells (DC) and T cells, thus dampening therapeutic responses against carcinogen-induced and transplantable tumors.In this setting, the administration of a glucocorticoid receptor antagonist reversed the negative impact of psychosocial stress on therapeutic outcomes. 14Taken together, these findings suggest that effectively preventing or managing psychological stress by pharmacological strategies could significantly improve oncological prognosis.2][43] These stress mediators also cause intracellular hypermetabolism, as evidenced by the accumulation of lipid droplets in MCF-7 breast cancer cells treated with AR agonists in vitro. 44,45Several downstream molecular mediators have been identified as responsible for pro-tumorigenic β-AR signaling, including the intracellular second messengers cAMP and PKA, which transactivates epidermal growth factor receptor (EGFR) 46 and triggers the initiation of the mitogen-activated protein kinase 1 (MAP2K1 better known as MEK1)/mitogenactivated protein kinase 1(MAPK1) and MAPK3 (better known as ERK1/2) cascade 47 thus stimulating cyclin D1, cyclin E2, and cyclin-dependent kinases CDK 4/6 to promote proliferation. 179][50] PKA also upregulates transcription factors including nuclear factor kappa B (NF-kB), activator protein 1 (AP1), and cAMP response element-binding protein (CREB) in the context of lung and pancreatic adenocarcinoma development. 51Additionally, β-AR activation results in enhanced retinoblastoma protein phosphorylation and suppresses Rap1B prenylation, leading to reduced cell-cell adhesion and a migratory phenotype. 35,38,42,46,52Interestingly, the autocrine secretion of epinephrine by certain cancer cells can stimulate β-AR, and this effect is further increased by oncogenic factors such as nicotine. 53,54Altogether these observations support the hypothesis that β-AR antagonists have clinical potential by halting malignant disease and decreasing the incidence of recurrences as suggested by the inverse correlation between the incidence of prostate adenocarcinoma and the use of antihypertensive drugs including β-blockers (n = 2442, HR = 0.7, 95% [0.5-0.9]). 55he exploration of different types of β-AR has been subject to extensive research.However, among cardioselective βblockers, the nonselective propranolol appears to be particularly effective. 56Propranolol acts on both β1 and β2 receptors and showed the capacity to effectively mitigate oxidative stress as well as pro-tumorigenic inflammatory response such as IL-6 and TNF-α production. 57,589]41,52,62,63 Thus, by blocking β-adrenergic signaling and counteracting the metastatic potential of epinephrine and norepinephrine, propranolol inhibits the invasion of malignant cells and reduces their metastatic spread to distant organs. 649][70][71][72][73][74][75][76] AR antagonists also exhibit antiangiogenic properties by decreasing the expression and activity of vascular endothelial growth factor (VEGF) thus further impacting cancer progression. 66,77,78f note β-blockers can induce distinct types of cellular stress including autophagy, 79,80 endoplasmic reticulum (ER) stress and mitochondrial dysfunction resulting in the production of reactive oxygen species (ROS) and affecting glucose metabolism, 81,82 altogether triggering apoptotic or necro(pto)tic cell death [83][84][85][86][87][88][89][90] of cancer cells.3][94] AR antagonists also exert trans-inhibitory effects on certain signaling pathways and transcription factors involved in carcinogenesis.Epidermal growth factor receptor (EGFR) is frequently overexpressed in epithelial tumors, resulting in elevated levels of intracellular cAMP and PKA, which promotes angiogenesis, invasiveness, and renders cells resistant to apoptosis.Both propranolol and atenolol can prevent the development and progression of tumors by competitively decreasing intracellular cAMP and PKA levels. 18,957][98][99] Finally, β-AR antagonists have been shown to reverse nicotine-induced mitogenic and protooncogenic factors such as COX-2, ERK1/2, PGE2, PKC, and VEGF in colon, gastric, and lung cancer cells in a dose-dependent manner. 54,100,101arvedilol, yet another β-and β-AR antagonist, exerts cytotoxic effects on many human hematopoietic and solid tumor cell lines. 102Compared with other adrenergic agents, carvedilol exhibits a unique Ca 2+ mobilization capacity by exerting control over extracellular Ca 2+ influx and the release of Ca 2+ from ER stores.The carvedilol-orchestrated increases in cytosolic Ca 2+ movement triggers cytotoxicity and inhibits the migratory capacity of human osteosarcoma, hepatoma and oral cancer cells in a concentration-dependent manner. 85,87,103arvedilol inhibits signaling pathways promoting invasiveness, including the cAMP, PKA/SCR, PKCs/Src pathways. 104oreover, carvedilol inhibits EGF-mediated malignant skin transformation in a dose-dependent manner by impairing AP-1 activation. 105Conversely, atenolol, another β1-AR specific antagonist, failed to prevent neoplastic transformation after application to mouse epidermal cells JB6 P. +105 Until now β3-AR blockade was less investigated.However, an increased expression of β3-AR was reported for neuroblastoma and melanoma. 86Moreover, β3-ARs favor the recruitment of tumor-associated pro-inflammatory and pro-tumor effectors such as fibroblasts and M2 macrophages.The use of β3-AR antagonists, such as SR59230A and L-748 337, reportedly impacts tumor vasculature and reduces the growth of melanoma. 86,106SR59230A induces a significant reduction of mitochondrial activity, halting ATP synthesis and triggering the generation of reactive oxygen species, resulting in tumor cell death. 107Moreover, the inhibition of β3-AR reduces the proliferation of neuroblastoma by dysregulation of bioactive lipid sphingosine kinase 2/sphingosine 1-phosphate metabolism, which is implicated in various cancers and anticancer therapy resistance. 108Furthermore, β3-AR antagonists were shown to reduce the phosphorylation of the mTOR/p70S6K pathway, thus reducing malignant growth. 109AR antagonists have shown a significant potential in mitigating the immunosuppressive effect of chronic stress, thereby improving immunosurveillance.Thus, propranolol was shown to suppress stress-induced lung metastases in a preclinical model of murine breast cancer, while nadolol decreased the incidence of metastases promoted by surgical stress by 50%. 61,110,111In various models of subcutaneous cancers, propranolol prevented a stress-induced ileopathy that led to immunosuppressive dysbiosis. 112Propranolol also suppresses the progression of hematopoietic cancers such as acute lymphoblastic leukemia by impairing α-adrenergic signaling activated during psychological stress. 113urthermore, α-blockers decrease the number of myeloidderived suppressor cells (MDSCs).][116][117][118] β-adrenergic receptors play an important role in shaping the immune orientation of the tumor microenvironment. 119,120hus, decreasing adrenergic stress by different approaches including physiological manipulation such as placement of mice in a thermoneutral environment, genetic interventions such as the knockout of β-AR or pharmacological β-blockade, increases glycolysis and oxidative phosphorylation in tumorinfiltrating lymphocytes.Reduction of adrenergic stress upregulates the expression of the costimulatory molecule CD28, stimulates cytokine release 121 and enhances the ration of cytotoxic over regulatory T cells.It also increases the secretion of granzyme B and IFN-γ contributing to immune-mediated anticancer responses in mice. 96,99,122Additionally, SR59230A promotes the differentiation of stromal cells and increases the abundance of lymphoid, myeloid, and NK progenitor cells in the tumor microenvironment.Altogether, these effects may inhibit tumor progression, inflammation and angiogenesis. 123ropranolol has demonstrated a remarkable synergism with current antineoplastic therapies.Specifically, it enhances radiosensitivity, thereby increasing radiotherapy-induced abscopal antitumor effect and exerts T cell-dependent immune response that effectively slows tumor growth.9][130][131][132][133][134] β-blocking agents also boosted the anticancer effect in combination with targeted therapies such as U0126 (a MAPK inhibitor), 79 sorafenib (a multikinase inhibitor), 80 vemurafenib (a B-Raf gene inhibitor), 135 and sunitinib (an inhibitor of tyrosine kinase). 136][139][140][141][142] If combined with the antitumor vaccine STxBE7, propranolol strongly enhanced the amount of tumor infiltrating CD8 + T cells, although without improving their activity. 143ven agents without any direct antitumor activity have been found to potentiate the cytotoxic effects of β-blockers.Thus, the combination of propranolol with metformin, an oral antidiabetic agent, revealed an unexpected synergistic inhibitory effect on proliferation, invasion, and migration in vitro and reduced tumor growth and metastasis in vivo. 144,1457][148] In conjunction with 2-deoxy-D-glucose (2DG), propranolol significantly reduced glucose metabolism associated with alterations in mitochondrial morphology and the subsequent activation of endoplasmic reticulum stress, autophagy, proliferative arrest ultimately resulting in apoptosis. 149Altogether, this underscores the potential of AR blocking agents alone or in combination with additional medication as novel anticancer (immuno)therapies.Table 2, Figure 2.

Published clinical trials
The aforementioned preclinical findings spurred the initiation of numerous clinical trials most of which are observational (12 retrospective trials, 1 prospective trial and 6 meta-analyses).Retrospective studies come from cohorts of oncological patients treated with β-blockers for a history of cardiovascular disease or arterial hypertension or from data extracted of prospective trials with incidental use of β-blockers.Most of the results concluded to a positive impact of β-blockers on oncological outcomes.βblockers significantly decreased tumor growth and the risk of metastasis into distant organs.1][152][153][154][155][156][157][158][159][160][161] These positive and encouraging results need to be confirmed in prospective randomized controlled trials.Indeed, these studies involved many sources of bias such as combination of antihypertensive drugs (β-blockers plus angiotensin-II-receptor inhibitor or angiotensin-converting enzyme inhibitors) and positive effects of β-blockers on cardiovascular mortality.Only three trials failed to report prognostic effects of β-blockers [162][163][164] except a better response to pembrolizumab in the treatment of stage III melanoma. 162Only one study reported negative effects of β-blockers in a cohort of HER2 + breast cancer patients treated with trastuzumab, where β-blocker appeared to decrease survival (PFS adjusted HR = 2.21, 95%[1.56-3.12];p < 0.001 and OS adjusted HR = 2.46, 95% [1.69-3.57];p < 0.001) 165 .However, the higher rate of mortality observed in this trial might involve cardiovascular mortality or immune toxicity.Table 3 Nine prospective interventional or randomized controlled trials have been published.One study enrolled 25 participants with multiple myeloma to receive either propranolol in titrated doses or placebo for 5 weeks.This trial concluded on the tolerability and the efficacy of propranolol to minimize βadrenergic stress during hematopoietic cell transplantation.It also showed successful engraftment and effective response against myeloma when propranolol was administered. 166afety and efficacy of β-blockers on adrenergic stress during the treatment of 26 ovary cancers were also confirmed. 167Used as a standalone agent during breast cancer and melanoma care, propranolol increases immune cell infiltration into the tumor bed and significantly reduces the risk of recurrence. 168,169hen associated with conventional antineoplastic treatments such as taxanes or anthracyclines, β-blockers are also perfectly tolerable and safe. 170Moreover, propranolol potentiates the immune effects of pembrolizumab against melanoma. 171][174][175] Finally, a few prospective studies all reported promising oncological outcomes.Thus, the study of Ramondetta et al. showed that patients with ovary cancer treated with propranolol had 55.5% complete response, 33.3% partial response, 5.6% stable response, and only 5.6% progressive disease 165 .In the randomized controlled trial by De Giorgi et al. the administration of β-blocker to patients with melanoma decreased the risk of recurrence (80%, HR = 0.18, 95% CI [0.04-0.89],p = 0.03) with a DFS 89% vs 64% (p = 0.04).Treatment with β-blocker also decreased the rate of progressive disease (15.8% vs 41.2%) and death (10.5% vs 17.7%). 167Associated with pembrolizumab, β-blockers allowed to achieve 7 partial responses and 1 stable disease in a cohort of 9 metastatic melanoma patients. 169f note, four studies notified cardiovascular events such as hypotension and bradycardia due to the consumption of β-blockers without major consequences. 164,166,168,169

Completed clinical trials
The primary focus of these trials was to study the effect of βblockers as standalone agents.Among these trials, NCT01544959 evaluated the possibility of substituting fentanyl with esmolol for anesthesia induction, followed by metoprolol during mastectomy, with the aim to manage hemodynamic, perioperative pain and postoperative nausea and vomiting.NCT02596867, a non-randomized phase II trial, studied the effect of β-adrenergic blockade with 0.75 mg/kg propranolol, administered twice daily for 3 weeks, prior to surgical resection of breast cancer.The trial assessed the tumor proliferative index using Ki-67 before and 3 weeks after propranolol administration and assessed the capacity of propranolol to decrease tumor proliferation in breast cancer.Similarly, the early phase I study NCT02013492 evaluated the potential of propranolol administered for 4 weeks in patients with locally-recurrent or metastatic solid tumors to decrease tumor growth by inhibiting the effects of adrenergic hormones on the tumor cells.Furthermore, the study NCT03861598 aimed at establishing a correlation between circulating tumor cells and favorable magnetic resonance imaging (MRI) results in patients with grade IV glioblastoma receiving chemotherapy with a combination of escalated doses of carvedilol.Further trials investigated whether the synergistic effects observed between β-blockers and conventional chemotherapies observed in preclinical studies were assessable in clinical practice.Both NCT01308944 and NCT01504126 aimed at confirming

Ongoing clinical trials
Most registered currently ongoing studies aim at evaluating the clinical impact, in particular overall survival and disease-free survival, after administration of β-blockers during the management of various solid tumors and hematological malignancies.Some of these trials also investigate potential advantages arising from the combination of β-blockers with additional anticancer or non-anticancer agents.

β-blockers as single agents
The randomized placebo-controlled clinical trial MELABLOCK (NCT02962947) is designed to evaluate the efficacy and safety of a daily dose of 80 mg propranolol in patients with stage II/IIIA melanoma.NCT04518124 consists of a single arm propranolol administered in a dose of 40-80 mg 2-3 times per day immediately after diagnosis of cutaneous angiosarcoma extending over a period of 3-6 weeks.Clinical and histological responses defined as a decrease in Ki-67 index will be measured until study completion.The early phase I interventional trial NCT03245554 intends to enroll in total 80 patients with gastric adenocarcinoma or non-metastasized colon cancer without any prior treatment.Propranolol will be administered for 1 week as a neoadjuvant treatment during the preoperative period and CT-scan and Ki-67 index will be used to evaluate tumor growth.NCT02944201 aims to investigate whether β-blockers administered to prostate cancer patients from the point of diagnosis until prostatectomy can decrease tumor growth measured by Ki-67 index and TUNEL assay performed on prostatectomy tissues.Notably, the phase II study NCT05679193 presents as a large randomized controlled trial that aims to assess the potential of a 3 weeks propranolol regimen in reducing recurrences after robot-assisted laparoscopic prostatectomy, a surgical procedure significantly less inflammatory and stressful as compared to conventional laparotomy.The study will assess changes in catecholamines and PSA levels during the perioperative period, the bioavailability of propranolol as well as the impact on anesthesiological and surgical strategies including the use of vasopressors, and the occurrence of complications.Finally, NCT05312255 focuses on the evaluation of immune effects, stress reduction and quality of life in non-chemotherapeutic interventions such as physical activity, specific nutritional regimen and propranolol treatment in patients with multiple myeloma.

β-blockers combined with conventional anticancer therapies
Four interventional clinical trials are planned to examine safety and efficacy of propranolol administered in combination with conventional chemotherapy to potentiate antitumor responses.NCT04005365 aims at incorporating propranolol into neoadjuvant chemotherapy in gastric cancer patients with the aim to improve overall response.NCT02641314 aims at administering a combination of propranolol with NSAID (celecoxib) antineuroblastic drugs (cyclophosphamide, etoposide and vinblastine) in children and adolescents with recurrent or progressive neuroblastoma.The primary objective is to demonstrate the non-inferiority in survival compared with controls, while as secondary outcomes safety, tolerance, and disease response rate will be assessed.NCT03108300 aims at assessing overall and progression-free survival in patients with metastatic soft tissue sarcoma co-administered propranolol 40 mg twice daily and doxorubicin.NCT02897986 is a dose escalation trial to determine the maximal tolerated dose of vinorelbine administered in combination with daily oral propranolol in children and teenagers with refractory solid tumors.NCT04682158 aims to determine the safety and efficacy of propranolol combined with standard neoadjuvant chemoradiation, as well as an impact on overall survival and pathologic response rate in patients undergoing esophageal cancer resection.The randomized phase II clinical trial NCT04493489 focuses on safety and efficacy of propranolol in adjuvant BCG therapy after the transurethral resection of bladder cancer and evaluates the capacity of the combination treatment to decrease relapses over a 2-year period.Table 6  Abbreviations: CI, confidence interval; DMFS, distant metastasis free survival; HR, hazard ratio; IV, intravenous; IP, intraperitoneal; NSAIDs, non-steroidal anti-inflammatory drugs; OS, overall survival; PFS, progression free-survival; RFS, recurrence free-survival.

β-blockers combined with immunotherapy
Five interventional trials (NCT05651594, NCT05451043, NCT03384836, NCT04848519, NCT01265576, NCT05968690) aim at exploring the addition of β-AR antagonists to immunotherapy (with pembrolizumab, durvalumab, tremelimumab, ipilimumab or nivolumab) alone or together with standard chemotherapy in the treatment of unresectable advanced and/ or metastatic digestive adenocarcinoma, stage III/IV melanoma and urothelial cancers.The primary objective is to evaluate the efficacy of β-blockade in boosting immunotherapy as measured by response evaluation criteria in solid tumors (RECIST).Secondary explorative objectives encompass correlations of biomarkers (such as immune effectors, circulating cytokines and stress) with efficacy, progression-free survival and overall survival.NCT04082910 will test the β1 adrenergic receptor blocker metropolol for its ability to control and prevent of cytokine release syndrome (CRS) in patients with lymphoma and leukemia enrolled for chimeric antigen receptor (CAR)-T cell infusion.Safety and tolerability of metropolol will be confirmed by evaluating heart rate and blood pressure, while the efficacy in the control of CRS will be assessed by monitoring body temperature and serum IL-6 levels.

β-blockers combined with other agents
Four prospective trials (NCT00502684, NCT03919461, NCT00888797, NCT03838029) aim at combining β-blockers with COX-2 inhibitors before, during, and after breast or colorectal cancer surgery to evaluate the impact on immune effector activity and tumor-infiltrating leucocytes.Moreover, cytokine secretion and serum levels of cortisol and VEGF will be assessed alongside psychological examinations.Oncological outcomes such as morbidity and mortality will be assessed in a 5-year follow up.Lastly, the monocentric observational prospective study NCT04245644 will evaluate if the combination of β-blockers with four chemopreventive agents (angiotensin converting enzyme inhibitors, aspirin, metformin, and statin) can improve the overall and disease-free survival in 800 patients with pancreatic ductal adenocarcinoma.

Discussion
Stress-related hormones and signaling via β-adrenergic receptors impact oncogenesis.Preclinical researches and pilot clinical trials support the hypothesis that β-blockers administered at clinically relevant concentrations during anticancer therapy extend the lifespan of individuals with malignant disease.Whether this effect is due to the direct blockage of β-AR and/ or due to an indirect systemic effect via the reduction of stress and corticotropic activity is still under discussion.Indeed, upon physical, biological, and psychological stress, the corticotropic HPA axis is activated releasing substantial amounts of immunosuppressive catecholamines and cortisol.Catecholamines are ligands of β-AR located at the plasma membrane of cytolytic immune effectors, negatively impacting mobility and activity, but also on β-AR present on cancer cells where they can stimulate proliferation, invasion, and migration.Of note, different β-AR subtypes are present with a strong predominance of the β2 sub-group. 18ICI 118 551, the most selective β2-AR antagonist, demonstrated consistent antitumor activity while no or partial effects were observed with the β1-specific blocker atenolol. 41,105he implication of β1-receptors is still uncertain, and further investigation is required to understand the contribution of each type of receptor in tumor development.Selective β3-AR antagonists have been even less studied, however, preclinical data noticed antiproliferative and apoptotic effects, suggesting β3-AR could be a target for anticancer therapy.
At present, in the field of oncology, preference is giving to nonspecific β-blockers such as propranolol, which targets both β1/2 ARs.However, it is important to consider potential side effects arising from dual β1/2 blocking.Due to the expression of β-ARs at the tumor cell surface, some research has explored the use of carvedilol, a α-blocker, with alpha-blocking property and has demonstrated an anti-tumor effect.Thus, reduced tumor cell proliferation was observed following the use of α2-AR agonists such as clonidine, a common anti-hypertensive agent. 176This might indicate a crosstalk between α2-and β2-ARs in stimulating cancer cell growth.Further research is needed to elucidate the pro-or anti-tumor profiles of α-ARs.
An interesting aspect was advanced with clinical trial NCT01544959 in which authors hypothesized that fentanyl, an opioid used to control acute pain during induction and maintenance of anesthesia, could be replaced by β-blockers.8][179] Alternative techniques such as "opioid-free-anesthesia", a specific protocol mixing local anesthetics, ketamine, magnesium and dexmedetomidine, are emerging for the management of acute pain during the peroperative period.In this setting, due to their anti-tumor effect and immunostimulatory properties, β-blockers appear as an appealing option for opioid replacement.Reportedly, β-adrenergic stimulation inhibits the primary phase of CD8 + T lymphocytes activation, thus providing a rationale for the administration of β-blockers together with T cell targeted immunotherapies. 122urgical glucocorticoid stress is significantly activated by local and systemic inflammatory pain that can be caused by surgical tissue damage and is mediated by pro-tumorigenic COX-2.Several randomized controlled trials advanced the possibility to potentiate antitumor effects by blocking sympathetic signaling and managing pain with a combination of β-AR antagonists and COX-2 inhibitors (NCT00502584; NCT03919461; NCT00888797; NCT03838029).COX-2 inhibitors belong to the family of non-steroidal anti-inflammatory drugs (NSAIDs) and previous observational clinical trials supported the notion that NSAIDs might improve oncological outcomes.Thus, Desmedt et al. observed that intraoperative administration of ketorolac, a COX-1 and COX-2 inhibitor, significantly reduced the incidence of distant recurrences after breast cancer surgery. 180In a study involving 327 women undergoing mastectomy, Forget et al. reported a significantly lower recurrence rate (p = 0.019) after administration of ketorolac prior to surgery, while other analgesics, such as sufentanil, ketamine and clonidine, showed no effect. 181A retrospective analysis in a cohort of 720 breast cancer patients revealed that injection of the NSAIDs ketorolac and diclofenac during conservative breast cancer surgery correlated with improved disease-free (HR = 0.57, p = 0.01) and overall survival (HR = 0.35, p = 0.03). 182Finally, in a propensity score matching study involving 2502 patients with non-small cell lung cancer, immunotherapy combined with the administration of NSAIDs was associated with a better overall survival (HR = 0.85, p < 0.001). 183In vitro, ketorolac was found to decrease proliferation, migration and angiogenesis, and to enhance the sensitivity of renal cancer to apoptosis.In mice, ketorolac caused tumor growth inhibition when used as a standalone agent or combined with sunitinib. 184In a model of head and neck squamous cell carcinoma, COX-2 inhibition showed additive and synergistic effects with EGFR inhibitors enhancing tumor cell death both in vitro and in vivo, especially in PIK3CAmutated cancers. 99Altogether, the combination of COX-2 inhibitors with β-blockers seems to be a promising option to potentiate antitumor responses.
In addition, activation of β-ARs in response to surgical stress promotes the survival of circulating tumor cells and increases the incidence of metastases.Surgical glucocorticoid stress can be optimally managed by spinal anesthesia or epidural anesthesia during the perioperative period. 185y controlling stress and inflammatory pain, medullar anesthesia also positively impacted oncological outcome by decreasing the incidence of recurrence.However, these analgesic procedures are contraindicated in bleeding disorders, infection, backbone osteosynthesis or upon patient refusal, necessitating alternative analgesia techniques.In this case, anxiolytic premedication (the day before and 2 h before surgery), for instance with benzodiazepines, can control surgical stress.Premedication has four main objectives: i) decreasing the level of anxiety and its physical consequences such as tachycardia, perspiration and polypnea; ii) minimizing the intensity of biochemical reactions and metabolic activity; iii) enhancing the analgesic potency of anesthetics; and iv) blocking parasympathetic effects induced by anesthesia and surgery such as salivary hypersecretion, nausea, vomiting, laryngeal spasms, and dysrhythmia.Here, β-blockers offer an appealing premedication option because they address all the aforementioned objectives without the known side effects of benzodiazepines such as sleepiness, confusion, and balance disorder.In contrast to other cardiologic agents targeting the angiotensin system, β-blockers are not contraindicated prior to anesthetic procedures.To reverse or inhibit the surgical glucocorticoid stress-induced immune system suppression, β-blockers used at a dose not triggering hypotension, could be considered for cancer patients, especially in the case of contraindication for medullar anesthesia.So far, specific guidelines for the use of β-blockers during the preoperative period are still lacking, and the efficacy of such premedications still requires further demonstration.

Conclusion
All forms of stress, be they physical, biological, or of psychological origin, can activate sympathetic signaling pathways promoting the release of catecholamines and other stress mediators into the systemic circulation.Catecholamines promote the proliferation, migration, and invasion of tumor cells, while suppressing the cytolytic function of immune effectors, through direct interaction with β-AR located on their plasma membrane.β-blockers can counteract such deleterious effects by competitively interfering with the binding of catecholamines to AR. Promising results from preclinical and clinical pilot studies suggesting that β-blockade can improve the outcome of cancer treatments now await confirmation in ongoing prospective randomized controlled trials.The facts that β-blockers are already approved and widely used for cardiovascular indications may accelerate their deployment in oncological practice.
193 Neuroblastoma Propranolol Human neuroblastoma KELLY, CHLA-20, LAN-5, IMR-32, SK-N-BE1, SK-N-BE 2 , SK-N-BE 2 c, SK-N-SH, SK-N-AS, LAN-6, SH-EP, CHLA-15, CHLA-90, SK-N-FI cells Inhibition of growth and proliferation; apoptosis via activation of p53 and p73; synergistic effect with SN-38 (topoisomerase I inhibitor)feasibility of administering β-blockers before, during and after surgical ovarian cancer debulking until completion of chemotherapy to mitigate depression and anxiety and to evaluate an impact on immune response and survival.The randomized multicenter phase 2 study NCT01857817 was designed to evaluate clinical benefits and changes in circulating prostate-
143specific antigen (PSA) of the VT-122 protocol consisting of a co-administration of 22 mg propranolol plus etodolac 340 mg in clinically progressive prostate cancer.Table5

Table 3 .
Published observational studies (prospective, retrospective, and meta-analyses) investigating the inhibition of adrenergic signaling pathway in cancer patients.

Table 4 .
Published interventional and randomized controlled trials investigating the inhibition of adrenergic signaling pathway in cancer patients.

Table 5 .
Completed and terminated clinical trials investigating the inhibition of adrenergic signaling pathway in cancer patients (not yet published).

Table 6 .
Ongoing clinical trials investigating the inhibition of adrenergic signaling pathway in cancer patients.