Immune checkpoint molecule expression measured using circulating cell-free RNA isolated from the blood of metastatic prostate cancer patients.

380Background: Recent studies have identified panels of immune-related genes linked to progression and survival. Expressions usually are measured using RNA from tissue samples. The aim of the present study was to utilize circulating RNA (cfRNA) isolated from hormone-naive (HN) and castrate-resistant prostate cancer (CRPC) patients to measure gene expressions of PD-L1, cytotoxic T-lymphocyte associated protein 4 (CTLA-4), T-cell immunoglobulin and mucin domain 3 (TIM-3) and lymphocyte activated gene 3 (LAG-3). Androgen receptor (AR) and AR-variant 7 (AR-v7) expressions were also measured in these samples to test for any possible relationships with the immune checkpoint genes. Methods: Blood samples were collected from 53 metastatic prostate cancer patients. cfRNA was extracted from patients’ plasma and reverse transcribed into complementary DNA. The gene expressions (mRNA levels) of the above genes were determined by quantitative reverse transcription-PCR. Beta-actin was used to normalize gene expressions ...