Role of lymphotoxin-a and interleukin-17A in human prostate cancer.

Abstract

212 Background: Infiltrating immune cells have been implicated in prostate carcinogenesis. Murine studies suggest that B-cell-derived lymphotoxin (LT)a may be a key effector in the evolution to castrate-resistant prostate cancer (CRPC) (Ammirante et al, Nature 2011). Lymphotoxin a has also been implicated in the progression of murine fibrosarcoma, where it complements interleukin (IL)-17A, to synergistically enhance NFkB signaling. This interaction may also apply to human prostate cancer since IL-17-producing Th17 cells are abundant in these tumors. However, the role of LTα in human as distinct from murine prostate cancer remains unclear. Clinical validation is vital since murine models poorly recapitulate the behavior of prostate cancer in man. Methods: Serum levels of LTα and IL-17A were measured by ELISA in patients with benign (n=22) and malignant prostate disease (n=87). Samples were from 29 early prostate cancer patients (amenable to radical therapy), 28 with androgen-sensitive (AS) disease and 30 with CRPC. Data were not normally distributed and thus were analyzed by Mann-Whitney U test. Results: Serum LTαand IL-17A were significantly elevated in patients with both CRPC and early stage prostate cancer, compared to those with benign disease. LTαwas significantly raised in CRPC compared to AS disease. IL-17A was significantly higher in the early stage disease compared to AS prostate cancer. Conclusions: Based upon these data, we hypothesize that B-cell derived LTα synergises with Th17 derived IL-17A from the earliest stage of primary tumor development. In support of this, blockade of LTα in prostate cancer-prone (TRAMP) mice delays primary tumor onset and inhibits metastasis. Furthermore, NSAIDs protect more strongly against lifetime risk of prostate cancer in those individuals with an LTα over-producer polymorphism. Prostate cancer preferentially metastasizes to local lymph nodes and bone – sites at which mature B-cells are plentiful. Consequently, tumor-trophic effects of LTα would become increasingly efficient with disease progression. Our data are incompatible with and thus refute the clinical relevance of a role for androgen ablation in promoting LTα-driven CRPC.