Enriching gene expression profiles will help personalize prostate cancer management for African-Americans: A perspective

Immunologic disparities in prostate cancer between American men of African and European descent

Health disparities between American men of African and European descent (AA and EA, respectively) can be attributed to multiple factors, including disparities in socioeconomic status, access to healthcare, lifestyle, ancestry, and molecular aberrations. Numerous clinical trials and research studies are being performed to identify new and better therapeutic approaches to detect and treat prostate cancer. Of potential concern is the fact that the majority of the patients enrolled on these trials are EA. This disproportionate enrollment of EA could have implications when disease management recommendations are proposed without regard to the existing disparities in prostate cancer between races. With increasing advancements in immunotherapies, the immunological disparities between men of diverse ethnicities will need to be fully explored to develop novel and effective therapeutic approaches for prostate cancer patients globally. To help address this need, this review fully describes inequalities in prostate cancer at the immunological level between AA and EA.

A 17-Gene Panel Genomic Prostate Score Has Similar Predictive Accuracy for Adverse Pathology at Radical Prostatectomy in African American and European American Men

OBJECTIVE

To validate the 17-gene Oncotype DX Genomic Prostate Score (GPS) as a predictor of adverse pathology (AP) in African American (AA) men and to assess the distribution of GPS in AA and European American (EA) men with localized prostate cancer.

METHODS

The study populations were derived from 2 multi-institutional observational studies. Between February 2009 and September 2014, AA and EA men who elected immediate radical prostatectomy after a ≥10-core transrectal ultrasound biopsy were included in the study. Logistic regressions, area under the receiver operating characteristics curves (AUC), calibration curves, and predictive values were used to compare the accuracy of GPS. AP was defined as primary Gleason grade 4, presence of any Gleason pattern 5, and/or non-organ-confined disease (≥pT3aN0M0) at radical prostatectomy.

RESULTS

Overall, 96 AA and 76 EA men were selected and 46 (26.7%) had AP. GPS result was a significant predictor of AP (odds ratio per 20 GPS units [OR/20 units] in AA: 4.58; 95% confidence interval (CI) 1.8-11.5, P = .001; and EA: 4.88; 95% CI 1.8-13.5, P = .002). On multivariate analysis, there was no significant interaction between GPS and race (P >.10). GPS remained significant in models adjusted for either National Comprehensive Cancer Network (NCCN) risk group or Cancer of the Prostate Risk Assessment (CAPRA) score. In race-stratified models, area under the receiver operating characteristics curves for GPS/20 units was 0.69 for AAs vs 0.74 for EAs (P = .79). The GPS distributions were not statistically different by race (all P >.05).

CONCLUSION

In this clinical validation study, the Oncotype DX GPS is an independent predictor of AP at prostatectomy in AA and EA men with similar predictive accuracy and distributions.

Validation of a genomic classifier for prediction of metastasis and prostate cancer-specific mortality in African-American men following radical prostatectomy in an equal access healthcare setting

BACKGROUND

The Decipher 22-gene genomic classifier (GC) may help in post-radical prostatectomy (RP) decision making given its superior prognostic performance over clinicopathologic variables alone. However, most studies evaluating the GC have had a modest representation of African-American men (AAM). We evaluated the GC within a large Veteran Affairs cohort and compared its performance to CAPRA-S for predicting outcomes in AAM and non-AAM after RP.

METHODS

GC scores were generated for 548 prostate cancer (PC) patients, who underwent RP at the Durham Veteran Affairs Medical Center between 1989 and 2016. This was a clinically high-risk cohort and was selected to have either pT3a, positive margins, seminal vesicle invasion, or received post-RP radiotherapy. Multivariable Cox models and survival C-indices were used to compare the performance of GC and CAPRA-S for predicting the risk of metastasis and PC-specific mortality (PCSM).

RESULTS

Median follow-up was 9 years, during which 37 developed metastasis and 20 died from PC. Overall, 55% (n = 301) of patients were AAM. In multivariable analyses, GC (high vs. intermediate and intermediate vs. low) was a significant predictor of metastasis in all men (all p < 0.001). Consistent with prior studies, relative to CAPRA-S, GC had a higher C-index for 5-year metastasis (0.78 vs. 0.72) and 10-year PCSM (0.85 vs. 0.81). There was a suggestion GC was a stronger predictor in AAM than non-AAM. Specifically, the 5-year metastasis risk C-index was 0.86 in AAM vs. 0.69 in non-AAM and the 10-year PCSM risk C-index was 0.91 in AAM vs. 0.78 in non-AAM. However, the test for interaction of race and the performance of the GC in the Cox model was not significant for either metastasis or PCSM (both p ≥ 0.3).

CONCLUSIONS

GC was a very strong predictor of poor outcome and performed well in both AAM and non-AAM. Our data support the use of GC for risk stratification in AAM post-RP. While our data suggest that GC may actually work better in AAM, given the limited number of events, further validation is needed.

Race-associated expression of MHC class I polypeptide-related sequence A (MICA) in prostate cancer

Despite the lack of a complete understanding of the disparities involved, prostate cancer (PCa) has both higher incidence and death rates in African American Men (AAM) relative to those of Caucasian American Men (CAM). MHC class I polypeptide related sequence A (MICA) is an innate immunity protein involved in tumor immunoevasion. Due to a lack of reports of race-specific expression of MICA in PCa, we evaluated MICA expression in patients' tumors and in cell lines from a racially diverse origin. Immunohistochemistry was done on a tissue microarray (TMA) with antibodies against MICA. Tumor MICA mRNA was assessed by data mining using Oncomine and PROGeneV2. Surface MICA and release rate of soluble (s) MICA was evaluated in PCa cell lines originally derived from African American (MDA-PCa-2b) or Caucasian (LNCaP and DU-145) PCa patients. Prostate tumor tissue had a 1.7-fold higher MICA expression relative to normal tissue (p < .0001). MICA immunoreactivity in PCa tissue from AAM was 24% lower (p = .002) compared to CAM. Survival analysis revealed a marginal association of low MICA with poor overall survival (OS) (p = .058). By data mining analysis, a 2.9-fold higher level of MICA mRNA was evidenced in tumor compared to normal tissue (p < .0001). Tumors from AAM had 24% lower levels of MICA mRNA compared to tumors from CAM (p = .038), and poor prognosis was found for patients with lower MICA mRNA (p = .028). By flow cytometry analysis, cell fraction positive for surface MICA was of 3% in MDA-PCa-2b cells, 54% in DU-145 cells, and 67% in LNCaP cells (p < .0001). sMICA was detected in DU-145 and LNCaP cells, but was not detected in MDA-PCa-2b cells. Both LNCaP and DU-145 cells were sensitive to cytolysis mediated by Natural killer (NK) cells. MDA-PCa-2b cells, however were between 1.3-fold at 10:1 Effector:Target (E:T) ratio (p < .0001) and 2-fold at 50:1 E:T ratio (p < .0001) more resistant to NK-mediated cytolysis relative to cells from Caucasian origin. These results suggest that MICA expression may be related to the aggressive nature of PCa. Our findings also demonstrate for the first time that there are variations in MICA expression in the context of racial differences. This study establishes a rationale for further investigation of MICA as a potential race-specific prognostic marker in PCa.

Epigenetic analysis identifies factors driving racial disparity in prostate cancer

BACKGROUND

Prostate cancer (PCa) is the second most leading cause of death in men worldwide. African-American men (AA) represent more aggressive form of the disease compared to Caucasian (CA) counterparts. Several lines of evidences suggest that biological factors are responsible for the observed racial disparity.

AIM

This study was aimed at identifying the epigenetic variation among AA and CA PCa patients and whether DNA methylation differences have an association with clinical outcomes in the two races.

METHODS AND RESULTS

The cancer genome atlas (TCGA) dataset (2015) was used to identify existing epigenetic variation in AA and CA PCa patients. Reduced Representation Bisulfite Sequencing (RRBS) was performed to identify global DNA methylation changes in a small cohort of AA and CA PCa patients. The RRBS data were then used to identify survival and recurrence outcomes in AA and CA PCa patients using publicly available datasets. The TCGA data analysis revealed epigenetic heterogeneity, which could be categorized into four classes. AA associated primarily to methylation cluster 1 (p = 0.048), and CA associated to methylation cluster 3 (p = 0.000146). Enrichment of the Wnt signaling pathway was identified in both the races; however, they were differentially activated in terms of canonical and non-canonical Wnt signaling. This was further validated using the Decipher Genomics Resource Information Database (GRID). The RRBS data also identified discrete methylation patterns in AA compared with CA and, in part, validated our TCGA findings. Survival analysis using the RRBS data suggested hypomethylated genes to be significantly associated with recurrence of PCa in CA (p = 6.07 × 10-6) as well as in AA (p = 0.0077).

CONCLUSION

Overall, we observed epigenetic-based racial disparity in PCa which could affect survival and should be considered during prognosis and treatment.

The Pathologic Role of Toll-Like Receptor 4 in Prostate Cancer

Toll-like receptor (TLR) 4 is expressed on normal and malignant prostate epithelial cells. The TLR4 and its downstream signaling pathways mediate innate immune responses in the host against invading pathogens. However, multiple lines of evidence shows that TLR4 expression is increased in prostate tissues from prostate cancer patients, and altered TLR4 signals may promote cancer development, as well as antitumor effects. In this review, we have summarized key features of the TLR4 signaling pathway and its associated immune responses and focused on the pathologic role of TLR4 in prostate carcinogenesis and tumor progression.