Minireview: the molecular and genomic basis for prostate cancer health disparities

The feasibility of epidemiological research on prostate cancer in African men in Ibadan, Nigeria

BACKGROUND

Men of African descent have the highest incidence and mortality rates of prostate cancer (PrCa) worldwide. Notably, PrCa is increasing in Africa with Nigerian men being mostly affected. Thus, it is important to understand risk factors for PrCa in Nigeria and build capacity for cancer research. The goals of this study were to determine the feasibility of conducting an epidemiological study of PrCa and to obtain preliminary data on risk factors for PrCa in Nigeria.

METHODS

A case-control study (50 cases/50 controls) was conducted at the University College Hospital (UCH) in Ibadan, Nigeria, between October 2011 and December 2012. Men aged 40 to 80 years were approached for the study and asked to provide informed consent and complete the research protocol. Logistic regression models were used to examine associations between demographic, social and lifestyle characteristics and risk of PrCa.

RESULTS

The participation rate among cases and controls was 98% and 93%, respectively. All participants completed a questionnaire and 99% (50 cases/49 controls) provided blood samples. Cases had a median serum diagnostic PSA of 73 ng/ml, and 38% had a Gleason score 8-10 tumor. Family history of PrCa was associated with a 4.9-fold increased risk of PrCa (95% CI 1.0 - 24.8). There were statistically significant inverse associations between PrCa and height, weight and waist circumference, but there was no association with body mass index (kg/m(2)). There were no associations between other socio-demographic and lifestyle characteristics and PrCa risk.

CONCLUSION

This feasibility study demonstrated the ability to ascertain and recruit participants at UCH and collect epidemiological, clinical and biospecimen data. Our results highlighted the advanced clinical characteristics of PrCa in Nigerian men, and that family history of PrCa and some anthropometric factors were associated with PrCa risk in this population. However, larger studies are needed to better understand the epidemiological risk factors of PrCa in Nigeria.

Impact of race on selecting appropriate patients for active surveillance with seemingly low-risk prostate cancer

OBJECTIVE

To evaluate active surveillance (AS) criteria on their ability to predict favorable pathology at prostatectomy within a low-risk African American (AA) cohort.

METHODS

The sensitivity, specificity, positive predictive value, receiver operator curve, and area under the curve (AUC) were compared for 6 published AS criteria (National Comprehensive Cancer Network; Memorial Sloan-Kettering Cancer Center; Prostate Cancer Research International: Active Surveillance Study; Johns Hopkins-Epstein; University of California at San Francisco; and University of Miami) to predict organ-confined Gleason score 6 disease at prostatectomy in AAs and white Americans (WAs) with low-risk cancer. We also compared clinical parameters for AAs with favorable prostatectomy pathology with those for AAs with unfavorable pathology, and then used preoperative variables associated with unfavorable pathology as an additional exclusion criteria for AS.

RESULTS

Of 468 patients with low-risk disease, 308 of 402 (76.6%) WAs and 55 of 66 (83.3%) AAs were eligible for AS by one or more criteria (P = .23). For WAs, Prostate Cancer Research International: Active Surveillance Study criteria had the highest rate of favorable pathology (81.7%) and the best performance (AUC = 0.70) in determining appropriate candidates for AS. However, all 6 AS criteria performed poorly for AA patients, with all AUCs ≤0.52. When comparing AAs with favorable pathology with AAs with unfavorable pathology, only family history of prostate cancer was statistically significant (11 of 25 [47.8%] vs. 8 of 41 [22.2%]; P = .04). When adjusting AS criteria in AAs to exclude those with a positive family history, the AUC increased most for the University of California at San Francisco (from 0.52 to 0.6) and Memorial Sloan-Kettering Cancer Center criteria (from 0.50 to 0.58).

CONCLUSION

Current criteria underperform in appropriately selecting AAs for AS. AAs considering AS should be counseled about their increased risk for occult adverse pathology, particularly if a family history of prostate cancer is present.

ROBO1, a tumor suppressor and critical molecular barrier for localized tumor cells to acquire invasive phenotype: study in African-American and Caucasian prostate cancer models

High-risk populations exhibit early transformation of localized prostate cancer (CaP) disease to metastasis which results in the mortality of such patients. The paucity of knowledge about the molecular mechanism involved in acquiring of metastatic behavior by primary tumor cells and non-availability of reliable phenotype-discriminating biomarkers are stumbling blocks in the management of CaP disease. Here, we determine the role and translational relevance of ROBO1 (an organogenesis-associated gene) in human CaP. Employing CaP-progression models and prostatic tissues of Caucasian and African-American patients, we show that ROBO1 expression is localized to cell-membrane and significantly lost in primary and metastatic tumors. While Caucasians exhibited similar ROBO1 levels in primary and metastatic phenotype, a significant difference was observed between tumor phenotypes in African-Americans. Epigenetic assays identified promoter methylation of ROBO1 specific to African-American metastatic CaP cells. Using African-American CaP models for further studies, we show that ROBO1 negatively regulates motility and invasiveness of primary CaP cells, and its loss causes these cells to acquire invasive trait. To understand the underlying mechanism, we employed ROBO1-expressing/ROBO1-C2C3-mutant constructs, immunoprecipitation, confocal-microscopy and luciferase-reporter techniques. We show that ROBO1 through its interaction with DOCK1 (at SH3-SH2-domain) controls the Rac-activation. However, loss of ROBO1 results in Rac1-activation which in turn causes E-Cadherin/β-catenin cytoskeleton destabilization and induction of cell migration. We suggest that ROBO1 is a predictive biomarker that has potential to discriminate among CaP types, and could be exploited as a molecular target to inhibit the progression of disease as well as treat metastasis in high-risk populations such as African-Americans.

Inhibition of prostatic cancer growth by ginsenoside Rh2

Ginsenoside Rh2 (GRh2) has been reported to have therapeutic effects on some types of cancer, but its effect on prostatic cancer has not been extensively evaluated. Here, we show that GRh2 can substantially inhibit the growth of prostatic cancer in vivo and in vitro. Moreover, the inhibition of the tumor growth appeared to result from a combined inhibitory effect on tumor cell proliferation and tumor cell invasiveness. Further analyses suggest that GRh2 seemed to activate transforming growth factor β (TGFβ) receptor signaling in prostatic cancer cells, which subsequently inhibits cell proliferation and invasion through regulating cell-cycle controllers and (MMPs), respectively. Taken together, our data reveal an essential anti-prostatic cancer effect of GRh2 and demonstrate that this effect is through augment of TGFβ receptor signaling in the prostatic cancer cells. GRh2 thus appears to be a promising therapy for prostatic cancer.

Metabolic syndrome-like components and prostate cancer risk: results from the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) study

OBJECTIVE

To evaluate the relationship between number of metabolic syndrome (MetS)-like components and prostate cancer diagnosis in a group of men where nearly all biopsies were taken independent of prostate-specific antigen (PSA) level, thus minimising any confounding from how the various MetS-like components may influence PSA levels.

SUBJECTS/PATIENTS AND METHODS

We analysed data from 6426 men in the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) study with at least one on-study biopsy. REDUCE compared dutasteride vs placebo on prostate cancer risk among men with an elevated PSA level and negative pre-study biopsy and included two on-study biopsies regardless of PSA level at 2 and 4 years. Available data for MetS-like components included data on diabetes, hypertension, hypercholesterolaemia, and body mass index. The association between number of these MetS-like components and prostate cancer risk and low-grade (Gleason sum <7) or high-grade (Gleason sum >7) vs no prostate cancer was evaluated using logistic regression.

RESULTS

In all, 2171 men (34%) had one MetS-like component, 724 (11%) had two, and 163 (3%) had three or four. Men with more MetS-like components had lower PSA levels (P = 0.029). One vs no MetS-like components was protective for overall prostate cancer (P = 0.041) and low-grade prostate cancer (P = 0.010). Two (P = 0.69) or three to four (P = 0.15) MetS-like components were not significantly related to prostate cancer. While one MetS-like component was unrelated to high-grade prostate cancer (P = 0.97), two (P = 0.059) or three to four MetS-like components (P = 0.02) were associated with increased high-grade prostate cancer risk, although only the latter was significant.

CONCLUSION

When biopsies are largely PSA level independent, men with an initial elevated PSA level and a previous negative biopsy, and multiple MetS-like components were at an increased risk of high-grade prostate cancer, suggesting the link between MetS-like components and high-grade prostate cancer is unrelated to a lowered PSA level.

Italianity is associated with lower risk of prostate cancer mortality in Switzerland

PURPOSE

Different prostate cancer mortality rates observed in European countries may depend on cultural background. We aimed at exploring variation in prostate cancer mortality in the language regions of Switzerland as a function of "Italianity", a proxy for adherence to an Italian lifestyle.

METHODS

We used data of the Swiss National Cohort, a census-based record linkage study, consisting of census (1990 and 2000) and mortality (until 2008) data. 1,163,271 Swiss and Italian nationals 40+-year old were included. Multivariate age-standardized prostate cancer mortality rates and hazard ratios (HR) from Cox proportional hazards regression analysis were performed. Italianity was defined by an individual's nationality, place of birth and principal language, resulting in a score of 0-3 points.

RESULTS

Age-standardized prostate cancer mortality rates (per 100,000 person-years) were lowest in the Italian-speaking region of Switzerland (66.7 vs. 87.3 in the German-speaking region). Both Italian nationality and/or place of birth were significantly associated with lower mortality. There was a graded inverse association between mortality rates and increasing Italianity score. Individuals with the highest level of Italianity had a HR of 0.67 (95 % CI 0.59-0.76) compared to those with an Italianity score of zero. Results were similar when looking at language regions separately.

CONCLUSIONS

The strong and consistent association between Italianity and prostate cancer mortality suggests protective properties of an Italian lifestyle. Further research is required in order to determine which factors specific for Italian culture are responsible for the lower prostate cancer mortality.

Targeting SMAD3 for inhibiting prostate cancer metastasis

Although SMAD3 signaling has been suggested to play a role in the metastasis of various cancers, its possible involvement as well as the underlying mechanism in the pathogenesis in prostate cancer remains unclear. Here, we found that the MMP9 level, an indicator of the invasiveness of cancer cells, negatively correlates with the activity of phosphorylated SMAD3 levels in the prostate cancer patients. Moreover, the phosphorylated SMAD3 also appeared to regulate the MMP9 level in a prostate cancer cell line, PC3. Augmented phosphorylated SMAD3 inhibited MMP9 and invasiveness of PC3 cells, while inhibition of phosphorylated SMAD3 activated MMP9 and promoted PC3 cell invasiveness. Furthermore, forced MMP9 inhibition abolished the effect of phosphorylated SMAD3 on the invasiveness of PC3 cells, while forced MMP9 activation abolished the effect of phosphorylated SMAD3 on the invasiveness of PC3 cells. Taken together, our data suggest the possibility of the existence of a unique signaling cascade in which SMAD3 signaling regulates MMP9 during cancer metastasis.

AGE metabolites: a biomarker linked to cancer disparity?

Socioeconomic and environmental influences are established factors promoting cancer disparity, but the contribution of biologic factors is not clear. We report a mechanistic link between carbohydrate-derived metabolites and cancer that may provide a biologic consequence of established factors of cancer disparity. Glycation is the nonenzymatic glycosylation of carbohydrates to macromolecules, which produces reactive metabolites called advanced glycation end products (AGE). A sedentary lifestyle and poor diet all promote disease and the AGE accumulation pool in our bodies and also increase cancer risk. We examined AGE metabolites in clinical specimens of African American and European American patients with prostate cancer and found a higher AGE concentration in these specimens among African American patients when compared with European American patients. Elevated AGE levels corresponded with expression of the receptor for AGE (RAGE or AGER). We show that AGE-mediated increases in cancer-associated processes are dependent upon RAGE. Aberrant AGE accumulation may represent a metabolic susceptibility difference that contributes to cancer disparity.

Considering race and the potential for ERG expression as a biomarker for prostate cancer

Genomic rearrangement and overexpression of the ERG oncogene (also known as v-ets avian erythroblastosis virus E26 oncogene homolog) is estimated to occur at a rate of 40-50% in prostate cancer. Early evidence suggests that ERG overexpression may be associated with disease progression, and the utilization of ERG levels as a biomarker for prostate cancer is being strongly considered. However, the evidence is incomplete because it relies on studies that primarily focused on men of European ancestry, giving little consideration to African-American men even though African-American men bear a greater disease burden in the form of significantly greater incidence and worse outcomes. In this perspective article we bring to light the issue that the potential use of ERG expression as a biomarker is yet to be solidly established and may have limited utility or varied applicably for African-American men as compared with European-American men.