The G Protein-Coupled Estrogen Receptor (GPER): A Critical Therapeutic Target for Cancer

Estrogens have been implicated in the pathogenesis of various cancers, with increasing concern regarding the overall rising incidence of disease and exposure to environmental estrogens. Estrogens, both endogenous and environmental, manifest their actions through intracellular and plasma membrane receptors, named ERα, ERβ, and GPER. Collectively, they act to promote a broad transcriptional response that is mediated through multiple regulatory enhancers, including estrogen response elements (EREs), serum response elements (SREs), and cyclic AMP response elements (CREs). Yet, the design and rational assignment of antiestrogen therapy for breast cancer has strictly relied upon an endogenous estrogen-ER binary rubric that does not account for environmental estrogens or GPER. New endocrine therapies have focused on the development of drugs that degrade ER via ER complex destabilization or direct enzymatic ubiquitination. However, these new approaches do not broadly treat all cancer-involved receptors, including GPER. The latter is concerning since GPER is directly associated with tumor size, distant metastases, cancer stem cell activity, and endocrine resistance, indicating the importance of targeting this receptor to achieve a more complete therapeutic response. This review focuses on the critical importance and value of GPER-targeted therapeutics as part of a more holistic approach to the treatment of estrogen-driven malignancies.

Findings of Gynecomastia That Developed in Follow-up Secondary to Bicalutamide Treatment on Bone Scan

Prostate cancer is a common neoplastic disease especially in elder patients. Metastatic prostate disease has low five-year survival rate. Bicalutamide is an androgen receptor antagonist that acts as an inhibitor by competizing androgen receptors in the target tissue and used as a treatment option in prostate cancer. Bone scan was performed on a 79-year-old male with prostate cancer in our department. Blood pool images showed bilateral hyperemia in the breast regions which was not present on the previous scan one year ago. On physical examination, there was bilateral painful gynecomastia. It was learned that the patient was given Bicalutamide therapy after the first bone scan. Blood pool images may detect this side effect and should be evaluated with physical examination in case of clinical doubt.

Androgen receptor is a potential novel prognostic marker and oncogenic target in osteosarcoma with dependence on CDK11

Osteosarcoma is the most common bone cancer in children and adolescents. Previously, we have found that cyclin-dependent kinase 11 (CDK11) signaling was essential for osteosarcoma cell growth and survival. Subsequently, CDK11 siRNA gene targeting, expression profiling, and network reconstruction of differentially expressed genes were performed between CDK11 knock down and wild type osteosarcoma cells. Reconstructed network of the differentially expressed genes pointed to the AR as key to CDK11 signaling in osteosarcoma. CDK11 increased transcriptional activation of AR gene in osteosarcoma cell lines. AR protein was highly expressed in various osteosarcoma cell lines and patient tumor tissues. Tissue microarray analysis showed that the disease-free survival rate for patients with high-expression of AR was significantly shorter than for patients with low-expression of AR. In addition, AR gene expression knockdown via siRNA greatly inhibited cell growth and viability. Similar results were found in osteosarcoma cells treated with AR inhibitor. These findings suggest that CDK11 is involved in the regulation of AR pathway and AR can be a potential novel prognostic marker and therapeutic target for osteosarcoma treatment.

Long Term Progression-Free Survival in a Patient with Locally Advanced Prostate Cancer under Low Dose Intermittent Androgen Deprivation Therapy with Bicalutamide Only

Androgen deprivation is a common treatment option in patients with locally advanced or metastatic prostate cancer. No case of long term treatment with an intermittent approach with only low dose bicalutamide (50 mg daily) has been described yet. We report a 60-year-old patient, initially presenting with a PSA elevation of 19.2 ng/mL in 1996. After diagnosis of well to moderately differentiated prostate cancer by transrectal biopsy, the patient underwent an open radical prostatectomy. Final diagnosis was adenocarcinoma of the prostate, classified as pT3a, pR1, pV0, and pL1. Adjuvant intermittent androgen deprivation therapy with flutamide 250 mg was applied, which was changed to bicalutamide 50 mg once daily when it became available in 2001. Six on-phases were performed and PSA values never exceeded 20 ng/mL. The patient did not experience any serious side effects. To date, there are no clinical or radiological signs of progression. Current PSA value is 3.5 ng/mL.

Androgen deprivation therapy impact on quality of life and cardiovascular health, monitoring therapeutic replacement

INTRODUCTION

Androgen deprivation therapy (ADT) is commonly utilized in the management of both localized and advanced adenocarcinoma of the prostate. The use of ADT is associated with several adverse events, physical changes, and development of medical comorbidities/mortality.

AIM

The current article reviews known adverse events associated with ADT as well as treatment options, where available. Current recommendations and guidelines are cited for ongoing monitoring of patients receiving ADT.

METHODS

A PubMed search of topics relating to ADT and adverse outcomes was performed, with select articles highlighted and reviewed based on level of evidence and overall contribution.

MAIN OUTCOME MEASURES

Reported outcomes of studies detailing adverse effects of ADT were reviewed and discussed. Where available, randomized trials and meta-analyses were reported.

RESULTS

ADT may result in several adverse events including decreased libido, erectile dysfunction, vasomotor symptoms, cognitive, psychological and quality of life impairments, weight gain, sarcopenia, increased adiposity, gynecomastia, reduced penile/testicular size, hair changes, periodontal disease, osteoporosis, increased fracture risk, diabetes and insulin resistance, hyperlipidemia, and anemia. The definitive impact of ADT on lipid profiles, cardiovascular morbidity/mortality, and all-cause mortality is currently unknown with available data. Treatment options to reduce ADT-related adverse events include changing to an intermittent treatment schedule, biophysical therapy, counseling, and pharmacotherapy.

CONCLUSIONS

Patients treated with ADT are at increased risk of several adverse events and should be routinely monitored for the development of potentially significant morbidity/mortality. Where appropriate, physicians should reduce known risk factors and counsel patients as to known risks and benefits of therapy.

Optimal prophylactic and definitive therapy for bicalutamide-induced gynecomastia: results of a meta-analysis

OBJECTIVE

Bicalutamide is approved as an adjuvant to primary treatments (radical prostatectomy or radiotherapy) or as monotherapy in men with locally advanced, nonmetastatic prostate cancer (pca). However, this treatment induces gynecomastia in most patients, which often results in treatment discontinuation. Optimal therapy for these breast events is not known so far. We undertook a meta-analysis to assess the efficacy of various treatment options for bicalutamide-induced gynecomastia.

METHODS

The medline, cancerlit, and Cochrane library databases were searched and the Google search engine was used to identify prospective and retrospective controlled studies published in English from January 2000 to December 2010 comparing prophylactic or curative treatment options with a control group (no treatment) for pca patients who developed bicalutamide-induced gynecomastia. Radiotherapy-induced cardiotoxicity was also evaluated.

RESULTS

The search identified nine controlled trials with a total patient population of 1573. Pooled results from prophylactic trials showed a significant reduction of gynecomastia in pca patients treated with prophylactic tamoxifen 20 mg daily (odds ratio: 0.06; 95% confidence interval: 0.05 to 0.09; p = 0.09), and pooled results from treatment trials showed a significant response of gynecomastia to definitive radiotherapy (odds ratio: 0.06; 95% confidence interval: 0.01 to 0.24; p < 0.0001). Aromatase inhibitors and weekly tamoxifen were not found to be effective as prophylactic and curative options. For the radiotherapy, skin-to-heart distance was found to be an important risk factor for cardiotoxicity (p = 0.006). A funnel plot of the meta-analysis showed significant heterogeneity (Egger test p < 0.00001) because of low sample size.

CONCLUSIONS

Our meta-analysis suggests using prophylactic tamoxifen 20 mg daily as the first-line preventive measure and radiotherapy as the first-line treatment option for bicalutamide-induced gynecomastia. Aromatase inhibitors and weekly tamoxifen are not recommended.

Quality of life issues in men undergoing androgen deprivation therapy: a review

Androgen deprivation therapy (ADT) has been an essential treatment option for treating prostate cancer (PCa). The role for hormonal treatment initially was restricted to men with metastatic and inoperable, locally advanced disease. Now it has been extended to neoadjuvant or adjuvant therapy for surgery and radiotherapy, for biochemical relapse after surgery or radiation, and even as primary therapy for non-metastatic disease. Fifty percent of PCa patients treated will receive ADT at some point. There is growing concern about the adverse effects and costs associated with more widespread ADT use. The adverse effects on quality of life (QoL), including physical, social and psychological well-being when men are androgen-deprived, may be considerable. This review examines the QoL issues in the following areas: body feminisation, sexual changes, relationship changes, cognitive and affective symptoms, fatigue, sleep disturbance, depression and physical effects. Further suggestions for therapeutic approaches to reduce these alterations are suggested.

Discovery and mechanistic characterization of a novel selective nuclear androgen receptor exporter for the treatment of prostate cancer

Despite the success of medical strategies to reduce androgen levels in the treatment of prostate cancer, this disease invariably relapses to a castrate-resistant state that is generally fatal. Although it had been thought that androgen-insensitive cancers no longer relied on the androgen receptor (AR) for growth and survival, it is now clear that this is not the case. Because relapses are known to occur by many mechanisms that keep the AR functionally active, strategies to block AR accumulation in the nucleus may be therapeutically useful. Here, we report the discovery of a selective nuclear androgen receptor exporter (SNARE) that functions to exclude AR from the nucleus. SNARE-1 binds wild-type and mutant ARs and efficiently inhibits their transactivation activity and ability to induce PSA gene expression. SNARE-1 inhibits the androgen-sensitive growth of LNCaP cells and tumor xenografts. Quantitative subcellular localization studies suggest that SNARE-1 inhibits nuclear translocation of AR, but also facilitates export of nuclear AR that has been translocated by an agonist. Mechanistic studies indicate that SNARE-1 rapidly phosphorylates p38 mitogen-activated protein kinase (MAPK) and Ser(650) of the AR. Additionally, SNARE-1 was found to promote ubiquitination of AR in LNCaP cells. Lastly, SNARE-1 functions as a tissue-selective AR inhibitor, as it fails to phosphorylate p38 MAPK in U2OS bone cells that are stably transfected with AR. In summary, SNARE-1 inhibits AR function by a mechanism that is distinct from clinically available antiandrogens, such that it might inform novel methods to block AR function in androgen-independent prostate cancer.

The social context for psychological distress from iatrogenic gynecomastia with suggestions for its management

INTRODUCTION

Gynecomastia (breast development in males) is a side effect of androgen deprivation therapy (ADT) for prostate cancer (PCa). Medical interventions to prevent or treat gynecomastia carry risk of additional detrimental side effects. However, untreated gynecomastia can be physically uncomfortable and psychologically distressing. Shame from gynecomastia can lead patients to stop otherwise beneficial exercise.

AIMS

Our first aim is to explore the social context for gynecomastia and how it is interpreted by men with the condition, as well as by others, both male and female. Subsequently, we use our understanding of why gynecomastia is psychologically distressing to propose psychosocial interventions that could help men accept this side effect of ADT.

METHODS

We draw on academic literature, media accounts, and web-based testimonials from men with gynecomastia, to understand how gynecomastia is perceived by both patients and the medical community. We examine these resources in light of gynecomastia's impact on sex roles, sexuality, and gender identity issues.

MAIN OUTCOME MEASURES

By exploring what breasts in a male mean to the individual, we produce an understanding of the social context for distress from gynecomastia. From this understanding, we derive hypotheses about who might be most distressed from gynecomastia and strategies for alleviating this distress.

RESULTS

The shame and stigma of gynecomastia is linked to the objectification of women. We suggest that men fear that their breasts will marginalize and subordinate them within gender hierarchies. There is little evidence that breasts on a male erotically attract either men or women. Novel options for living with gynecomastia are contrasted with medicalized strategies including mastectomy.

CONCLUSION

Assessment instruments need to be developed to identify patients most likely to experience distress from gynecomastia and seek out medical interventions. Surgical, radiological, or pharmacological interventions may not be universally necessary if greater acceptance of gynecomastia is made available through psychosocial support programs. For example, PCa patients may learn to accept gynecomastia through reconceptualizing their breasts as autoerotic. Support programs modeled on those of the breast cancer community, including Encore and dragon boat racing, may also help to build communities to serve patients with gynecomastia while defending individuals against shame, isolation, and loss of self-esteem.