Mast cells as a tumor microenvironment factor associated with the aggressiveness of prostate cancer

We aimed to investigate the relationship between the degree of mast cells' (MCs) infiltration and clinicopathological features of prostate cancer (PCa) malignancy and to find out the possible mechanisms of the involvement of these cells in the formation of the aggressive course of the PCa development. The study was conducted on the clinical material of 60 patients with PCa of stages II-III. MCs in the PCa tissue were determined by a histochemical method using toluidine blue. The expression of osteopontin (OPN) was studied by the immunohistochemical method. The expression of miRNA-21, -126, -146a, -181a, and -221 was investigated by quantitative real-time PCR. Statistical processing of the results was performed using the GraphPad Prism 8 program. Our results demonstrated that the increased level of infiltration and degranulation of MCs in the PCa tissue was associated with such indices of the malignancy of the tumor process as the Gleason score and the preoperative PSA level in the blood serum of patients. A high level of MCs infiltration of the PCa tissue was associated with a significant decrease in the two-year recurrence-free survival rates of the patients by 23.3% (р=0.0455). A high degree of MCs infiltration of the PCa tissue was associated with 1.2 times (p=0.0347) higher level of OPN expression and 1.7 (p=0.0051) and 1.65 (p=0.0087) times lower levels of miR-126 and miR-181a expression, respectively. The obtained results indicate the participation of MCs as a factor of the tumor microenvironment in the PCa progression.