Increased Number of Plasma Cells Found in Black Men with Prostate Cancer, Associated With Improved Recurrence-Free Survival

The increased proportion of plasma cell infiltrate and augmented markers of natural killer (NK)–cell activity and IgG expression in tumors of Black compared with White men is associated with improved recurrence-free survival following surgery, according to data published in Nature Communications.¹

Although Black men experience higher mortality rates from prostate cancer than White men, these findings suggest that Black men derive greater survival benefits from immunotherapy treatment with sipuleucel-T (Provenge), suggesting plasma cells could be potential drivers of prostate cancer immune responsiveness.

“If a man’s prostate cancer has numerous plasma cells, we found he had improved cancer survival,” Edward Schaeffer, MD, senior author of the study and urologist at Northwestern Medicine, said in a press release.² “Our study suggests plasma cells are important in the body’s response to cancer.”

The research team analyzed the genomics of over 1300 tumor samples, finding more plasma cells in the samples of Black men versus samples of White men, on average. The sample included 2 cohorts with 452 tumors from self-identified Black men.

These prostate cancer samples possessed increased quantities of plasma cells and IgG expression. The tumors also demonstrated an increased level of NK-cell activity, suggesting that plasma cells may augment antibody-dependent cellular cytotoxicity within the tumor microenvironment.

More, while a majority of patients who had increased proportion of plasma cell infiltrate were Black men, the findings were not limited to this patient population. All men with elevated plasma cell levels saw improved cancer-free survival following surgery.

“The finding comes at a time as researchers are discovering plasma cells may play a greater role in cancer immunotherapy than previously thought,” Adam Weiner, MD, first author of the study and a Northwestern Medicine urology resident, said in a press release. “Testing for plasma cells in prostate cancer may help identify men who will benefit from immune-based treatments.”

The research team emphasized that this mechanism warrants further investigation to validate the role these cells play in prostate cancer tumor immune responses. Since these plasma cells were enriched in self-identified Black men, the research team explains that leveraging these findings could play an integral part in reducing racial disparities in outcomes for patients with prostate cancer.

The investigators suggest future work is necessary to determine how to measure and select a clinically relevant cutoff point for plasma cell content. More, the team suggests it will be difficult to generalize these findings to metastatic castrate-resistant prostate cancer because of the limited number of patients self-identifying with this disease.

“Our data suggest the prognostic value of plasma cell content in the TME [tumor microenvironment] may be defined by the context of inflammatory cytokine milieu,” wrote the investigators. “These observations warrant experimental designs to identify and potentially induce the TME context needed to optimize any plasma cell antitumorgenic effects.”

References:

1. Weiner AB, Vidotto T, Liu Y, et al. Plasma cells are enriched in localized prostate cancer in Black men and are associated with improved outcomes. Nat Comm. 2021;12(1):935. doi.org/10.1038/s41467-021-21245-w

2. Why Black Men’s Prostate Cancer May be More Responsive to Immunotherapy. News release. Northwestern University. February 10, 2021. Accessed February 18, 2021. https://news.feinberg.northwestern.edu/2021/02/why-black-mens-prostate-cancer-may-be-more-responsive-to-immunotherapy/