Prostatic tissue testosterone and dihydrotestosterone in African-American and white men

A Literature Review of Racial Disparities in Prostate Cancer Research

BACKGROUND

Despite recent awareness of institutional racism, there are still important racial disparities in prostate cancer medical research. We investigated the historical development of research on racial disparities and bias.

METHODS

PubMed was searched for the term 'prostate cancer race' and added key terms associated with racial disparity. As an indicator of scientific interest in the topic, we analyzed whether the number of publications increased linearly as an indicator of growing interest. The linearity is expressed as R2.

RESULTS

The general search term "prostate cancer race" yielded 4507 publications. More specific search terms with ≥12 publications showing a higher scientific interest were found after 2005. The terms with the most publications when added to the general term were "genetic" (n = 1011), "PSA" (n = 995), and "detection" (n = 861). There was a linear increase in publications for "prostate cancer race" (R2 = 0.75) since 1980. Specific terms added to the general terms with a high linear increase (R2 ≥ 0.7) were "screening" (R2 = 0.82), "detection" (R2 = 0.72), "treatment access" (R2 = 0.71), and "trial underrepresentation" (R2 = 0.71). However, only a few studies have investigated its association with sexual activity. A combination with "sexual" showed 157 publications but only two years with ≥12 publications/year.

CONCLUSION

The terms "genetic", "PSA", and "detection" have been the focus of recent research on racial differences in prostate cancer. We found that old stereotypes are still being mentioned but seem to find little interest in the current literature. Further research interest was found in "treatment access". Recently, interest in socioeconomic factors has decreased.

Serum Androgen Metabolites Correlate with Clinical Variables in African and European American Men with Localized, Therapy Naïve Prostate Cancer

Dihydrotestosterone (DHT) and testosterone (T), which mediate androgen receptor nuclear translocation and target gene transcription, are crucial androgens and essential molecular triggers required for the proliferation and survival of prostate cancer cells. Therefore, androgen metabolism is commonly targeted in the treatment of prostate cancer. Using a high-pressure liquid chromatographic assay with tandem mass spectral detection, we determined the serum levels of metabolites produced during DHT/T biosynthesis in African American (AA) and European American (EA) men with localized, therapy naïve prostate cancer. Serum progesterone and related metabolites were significantly lower in AA men than in EA men, and these differences were associated with rapid disease progression. Multivariate analysis revealed significant differences between a subset of intermediate androgen metabolites between AA and EA men and between men with <=3 + 4 and >=4 + 3 Gleason score disease. AA men have a significantly higher frequency of single nucleotide polymorphisms in CYP11B1 and CYP11B2, enzymes that regulate corticosterone-aldosterone conversion. Finally, higher levels of T and pregnenolone were associated with a lower risk of progression-free survival only in AA men. This work provides new insight into androgen metabolism and racial disparities in prostate cancer by presenting evidence of dysregulated androgen biosynthesis in therapy naïve disease that correlates with clinical variables.

Testosterone Replacement Therapy in Men with Untreated or Treated Prostate Cancer: Do We Have Enough Evidences?

PURPOSE

To investigate the oncologic safety of testosterone replacement therapy (TRT) in men with untreated or treated prostate cancer.

MATERIALS AND METHODS

We systematically searched PubMed, Embase, and Cochrane library database from January 1941 to March 2019.

RESULTS

In total, 36 articles met the eligibility criteria for this systematic review. They included a total of 2,459 TRT-treated patients, with a median of 20 patients per study (range: 1-1,142). Except for four studies, all were single-armed studies with poor quality scores (median MINOR, 9 of 24). Of the 36 studies, prostate cancer was managed through active surveillance (AS), in 5 studies; radical prostatectomy, in 11 studies; radiation therapy, in 5 studies; multiple intervention modalities, in 5 studies; and systemic therapy, in 9 studies. In comparison with TRT-treated and untreated patients, the pooled risk ratio (RR) was not significantly higher than one in comparisons of risk for disease progression (pooled RR, 0.83; 95% confidence interval, 0.57-1.21). The results of systematic review implied that TRT might be harmful in men with advanced disease (progression rate: 38.5%-100.0%), who undergo AS (15.4%-57.1%), and who successfully treated but having high-risk disease (0.0%-50.0%).

CONCLUSIONS

Compared to TRT-untreated patients, TRT-treated patients may not have increased risks for disease progression in prostate cancer. However, the quality of currently available evidence is extremely poor. TRT may be harmful in men with advanced disease burden, in those with untreated prostate cancer undergoing AS, and in those with successfully treated prostate cancer but having high-risk disease.

Racial disparity in prostate cancer in the African American population with actionable ideas and novel immunotherapies

BACKGROUND

African Americans (AAs) in the United States are known to have a higher incidence and mortality for Prostate Cancer (PCa). The drivers of this epidemiological disparity are multifactorial, including socioeconomic factors leading to lifestyle and dietary issues, healthcare access problems, and potentially tumor biology.

RECENT FINDINGS

Although recent evidence suggests once access is equal, AA men have equal outcomes to Caucasian American (CA) men, differences in PCa incidence remain, and there is much to do to reverse disparities in mortality across the USA. A deeper understanding of these issues, both at the clinical and molecular level, can facilitate improved outcomes in the AA population. This review first discusses PCa oncogenesis in the context of its diverse hallmarks before benchmarking key molecular and genomic differences for PCa in AA men that have emerged in the recent literature. Studies have emphasized the importance of tumor microenvironment that contributes to both the unequal cancer burden and differences in clinical outcome between the races. Management of comorbidities like obesity, hypertension, and diabetes will provide an essential means of reducing prostate cancer incidence in AA men. Although requiring further AA specific research, several new treatment strategies such as immune checkpoint inhibitors used in combination PARP inhibitors and other emerging vaccines, including Sipuleucel-T, have demonstrated some proven efficacy.

CONCLUSION

Genomic profiling to integrate clinical and genomic data for diagnosis, prognosis, and treatment will allow physicians to plan a "Precision Medicine" approach to AA men. There is a pressing need for further research for risk stratification, which may allow early identification of AA men with higher risk disease based on their unique clinical, genomic, and immunological profiles, which can then be mapped to appropriate clinical trials. Treatment options are outlined, with a concise description of recent work in AA specific populations, detailing several targeted therapies, including immunotherapy. Also, a summary of current clinical trials involving AA men is presented, and it is important that policies are adopted to ensure that AA men are actively recruited. Although it is encouraging that many of these explore the lifestyle and educational initiatives and therapeutic interventions, there is much still work to be done to reduce incidence and mortality in AA men and equalize current racial disparities.

Host versus cell-dependent effects of β-arrestin 1 expression in prostate tumorigenesis

Prostate cancer (PCa) constitutes a serious health challenge and remains one of the main causes of cancer-related death among men. The more aggressive form of the disease has been attributed to androgen independence, resulting in a lack of response to androgen deprivation therapy and sustained activation of other growth pathways. The scaffold proteins β-arrestin 1 and 2 (βarr1 and βarr2), which are known to mediate G protein-coupled receptor desensitization and internalization, were also shown to modulate prostate tumorigenesis. βarr1 is significantly overexpressed (>4-fold) in PCa cells relative to βarr2. In this study, we investigated the effect of βarr1 overexpression in PCa development and progression using the mouse and human PCa cell xenografts, and autochthonous transgenic adenocarcinoma of the mouse prostate (TRAMP) models deficient in β-arrestin depletion of βarr1 in TRAMP mice (TRAMP/βarr1-/-) increased PCa growth and decreased overall survival relative to control TRAMP or TRAMP/βarr2-/- animals. Prostate tissues from TRAMP/βarr1-/- tumors displayed an increase in androgen receptor (AR) expression, whereas overexpression of βarr1 in TRAMP-C1 (TRAMP-C1-βarr1-GFP) which derived from TRAMP decreased AR expression, cell proliferation and tumor growth in nude mice xenografts, relative to control TRAMP-C1-GFP. Knockdown of βarr1 expression in human MDA PCa 2b cells (MDA PCa 2b-βarr1-/-) also decreased AR expression cell proliferation and tumor growth relative to control (MDA PCa 2b-Sham) cells. Interestingly, both TRAMP-C1-βarr1-GFP and MDA PCa 2b-βarr1-/- xenografts showed a decrease in AKT phosphorylation but an increase in MAPK activation. Altogether, the data indicate that the effect of βarr1 in modulating AR signaling to regulate PCa aggressiveness is cell and host autonomous.

Proteomic-coupled-network analysis of T877A-androgen receptor interactomes can predict clinical prostate cancer outcomes between White (non-Hispanic) and African-American groups

The androgen receptor (AR) remains an important contributor to the neoplastic evolution of prostate cancer (CaP). CaP progression is linked to several somatic AR mutational changes that endow upon the AR dramatic gain-of-function properties. One of the most common somatic mutations identified is Thr877-to-Ala (T877A), located in the ligand-binding domain, that results in a receptor capable of promiscuous binding and activation by a variety of steroid hormones and ligands including estrogens, progestins, glucocorticoids, and several anti-androgens. In an attempt to further define somatic mutated AR gain-of-function properties, as a consequence of its promiscuous ligand binding, we undertook a proteomic/network analysis approach to characterize the protein interactome of the mutant T877A-AR in LNCaP cells under eight different ligand-specific treatments (dihydrotestosterone, mibolerone, R1881, testosterone, estradiol, progesterone, dexamethasone, and cyproterone acetate). In extending the analysis of our multi-ligand complexes of the mutant T877A-AR we observed significant enrichment of specific complexes between normal and primary prostatic tumors, which were furthermore correlated with known clinical outcomes. Further analysis of certain mutant T877A-AR complexes showed specific population preferences distinguishing primary prostatic disease between white (non-Hispanic) vs. African-American males. Moreover, these cancer-related AR-protein complexes demonstrated predictive survival outcomes specific to CaP, and not for breast, lung, lymphoma or medulloblastoma cancers. Our study, by coupling data generated by our proteomics to network analysis of clinical samples, has helped to define real and novel biological pathways in complicated gain-of-function AR complex systems.

Sarcopenia and Androgens: A Link between Pathology and Treatment

Sarcopenia, the age-related loss of skeletal muscle mass and function, is becoming more prevalent as the lifespan continues to increase in most populations. As sarcopenia is highly disabling, being associated with increased risk of dependence, falls, fractures, weakness, disability, and death, development of approaches to its prevention and treatment are required. Androgens are the main physiologic anabolic steroid hormones and normal testosterone levels are necessary for a range of developmental and biological processes, including maintenance of muscle mass. Testosterone concentrations decline as age increase, suggesting that low plasma testosterone levels can cause or accelerate muscle- and age-related diseases, as sarcopenia. Currently, there is increasing interest on the anabolic properties of testosterone for therapeutic use in muscle diseases including sarcopenia. However, the pathophysiological mechanisms underlying this muscle syndrome and its relationship with plasma level of androgens are not completely understood. This review discusses the recent findings regarding sarcopenia, the intrinsic, and extrinsic mechanisms involved in the onset and progression of this disease and the treatment approaches that have been developed based on testosterone deficiency and their implications.

Genetic and molecular differences in prostate carcinogenesis between African American and Caucasian American men

Prostate cancer is the most common non-skin cancer and the second leading cause of cancer-related death for men in the United States. Prostate cancer incidence and associated mortality are highest in African American men in comparison to other races. The observed differences in incidence and disease aggressiveness at presentation support a potential role for different pathways of prostate carcinogenesis between African American and Caucasian men. This review focuses on some of the recent molecular biology discoveries, which have been investigated in prostate carcinogenesis and their likely contribution to the known discrepancies across race and ethnicity. Key discussion points include the androgen receptor gene structure and function, genome-wide association studies and epigenetics. The new observations of the ethnic differences of the ERG oncogene, the most common prostate cancer gene, are providing new insights into ERG based stratification of prostate cancers in the context of ethnically diverse patient populations. This rapidly advancing knowledge has the likely potential to benefit clinical practice. Current and future work will improve the ability to sub-type prostate cancers by molecular alterations and lead to targeted therapy against this common malignancy.

Testosterone replacement and prostate cancer

This article is intended as a review of the available clinical data outlining the risks and benefits of testosterone (androgen) replacement therapy, specifically addressing the issue of the relationship between exogenous androgen administration and prostate cancer risk. There is controversy over whether androgen replacement is a risk factor for incident prostate cancer. Our review of current clinical information revealed that to date, no study or review has definitively shown that androgen replacement therapy is an independent risk factor for development of prostate cancer. Androgen administration seems to be beneficial in decreasing fatal cardiovascular events, body fat mass, and insulin resistance. Overall, the current clinical data seems to suggest that androgen replacement is an appropriate therapeutic option for men with symptomatic hypogonadism provided that patients continue to receive regular prostate screenings.

Interactions among genes, tumor biology and the environment in cancer health disparities: examining the evidence on a national and global scale

Cancer incidence and mortality rates show great variations across nations and between population groups. These variations are largely explained by differences in age distribution, diet and lifestyle, access to health care, cultural barriers and exposure to carcinogens and pathogens. Cancers caused by infections are significantly more common in developing than developed countries, and they overproportionally affect immigrant populations in the USA and other countries. The global pattern of cancer is not stagnant. Instead, it is dynamic because of fluctuations in the age distribution of populations, improvements in cancer prevention and early detection in affluent countries and rapid changes in diet and lifestyle in parts of the world. For example, increased smoking rates have caused tobacco-induced cancers to rise in various Asian countries, whereas reduced smoking rates have caused these cancers to plateau or even begin to decline in Western Europe and North America. Some population groups experience a disproportionally high cancer burden. In the USA and the Caribbean, cancer incidence and mortality rates are excessively high in populations of African ancestry when compared with other population groups. The causes of this disparity are multifaceted and may include tumor biological and genetic factors and their interaction with the environment. In this review, we will discuss the magnitude and causes of global cancer health disparities and will, with a focus on African-Americans and selected cancer sites, evaluate the evidence that genetic and tumor biological factors contribute to existing cancer incidence and outcome differences among population groups in the USA.

Second to fourth digit ratio: a predictor of prostate-specific antigen level and the presence of prostate cancer

OBJECTIVE

To investigate the relationships between the 2nd to 4th digit ratio (digit ratio) and prostate volume, prostate-specific antigen (PSA) level, and the presence of prostate cancer.

PATIENTS AND METHODS

Of the men that presented with lower urinary tract symptoms (LUTS) at a single tertiary academic center, 366 men aged 40 or older with a PSA level ≤ 40 ng/mL were prospectively enrolled. Right-hand 2nd and 4th digit lengths were measured prior to the PSA determinations and transrectal ultrasonography (TRUS). Prostate volumes were measured by TRUS without information about digit length. Patients with a PSA level ≥ 3 ng/mL underwent prostate biopsy.

RESULTS

No relationship was found between prostate volume and digit ratio [correlation coefficient (r) = -0.038, P = 0.466]. But, significant negative correlations were found between digit ratio and PSA (r = -0.140, P = 0.007). When the patients were divided into two groups (Group A: digit ratio < 0.95, n = 184; Group B: digit ratio ≥ 0.95, n = 182), Group A had a higher mean PSA level than Group B (3.26 ± 5.54 ng/mL vs 1.89 ± 2.24 ng/mL, P = 0.002) and had significantly higher risks of prostate biopsy [odds ratio (OR) = 1.75, 95% CI = 1.07-2.84] and prostate cancer (OR = 3.22, 95% CI = 1.33-7.78).

CONCLUSIONS

Patients with a lower digit ratio have higher risks of prostate biopsy and prostate cancer.

Prostate tissue androgens: history and current clinical relevance

Direct determination of androgen levels in prostate tissue provides a perspective on the organ that is not available via androgen serum levels. The principle prostatic androgens, primarily dihydrotestosterone (DHT) and secondarily testosterone, can be readily assayed in quick-frozen prostate biopsy cores or surgical specimens. Such assays have proved important in establishing (1) that DHT is a permissive factor in BPH pathogenesis, (2) a mechanism for the treatment of BPH, (3) an understanding of prostate cancer chemoprevention, (4) an explanation for the 'escape' of prostate cancer from castration therapy, (5) prostate safety of testosterone replacement therapy, and (6) insights into the cause of racial differences of prostate cancer. Future opportunities include clarification of new drug mechanisms for BPH and prostate cancer, as well as a better understanding of the pathogenesis of both, and as an aid in individual patient management. Determination of prostate tissue androgens may soon transition from research tool to clinical test.

Tissue and serum levels of principal androgens in benign prostatic hyperplasia and prostate cancer

Androgens are considered to play a substantial role in pathogenesis of both benign prostatic hyperplasia (BPH) and prostate cancer. The importance of determination of androgen levels in tissue and serum for cancer progression and prognosis has been poorly understood. The aim of study was to find out hormonal differences in both diseases, their correlations between intraprostatic and serum levels and predicted value of their investigation. Testosterone, dihydrotestosterone, androstenedione and also epitestosterone were determined in prostate tissue from 57 patients who underwent transvesical prostatectomy for BPH and 121 patients after radical prostatectomy for prostate cancer. In 75 subjects with cancer and 51 with BPH the serum samples were analyzed for testosterone, dihydrotestosterone and SHBG. Significantly higher intraprostatic androgen concentrations, i.e. 8.85+/-6.77 versus 6.44+/-6.43 pmol/g, p<0.01 for dihydrotestosterone, and 4.61+/-7.02 versus 3.44+/-4.53 pmol/g, p<0.05 for testosterone, respectively, were found in patients with prostate cancer than in BPH. Higher levels in cancer tissue were found also for epitestosterone. However, no differences were found in serum levels. Highly significant correlations occurred between all pairs of intraprostatic androgens and also epitestosterone as well as between serum testosterone and dihydrotestosterone (p<0.001) in both BPH and cancer groups. Correlation was not found between corresponding tissue and serum testosterone and dihydrotestosterone, either in benign or cancer samples. The results point to importance of intraprostatic hormone levels for evaluation of androgen status of patients, contrasting to a low value of serum hormone measurement.