Expression of PDL-1 Receptors in Prostate Cancer Patients and its Association with Tumour Aggressiveness: A Cross-sectional Study

Introduction: Prostate cancers are infiltrated with Programmed Death-1 (PD-1) expressing Cluster of Differentiation (CD)8+ T-cells which interact with Programmed cell Death Ligand-1 (PDL-1) receptors on Tumour Cells (TC). However, in many studies, male with prostate cancer did not respond to monotherapy (PDL blockade). This unresponsiveness could be due to the fact that prostate cancer usually does not express PDL-1. The PDL-1 expression has demonstrated a significant correlation with increased risk of disease progression in various tumours but data regarding its role in prostate cancer is conflicting.

Aim: To study the occurrence rate of PDL-1 expression and its association with tumour aggressiveness in prostate cancer.

Materials and Methods: This cross-sectional observational study was conducted at ABVIMS and Dr. Ram Manohar Hospital, New Delhi, India, from October 1st, 2018 to April 30th, 2020. A total of 120 males with prostate cancer who had their diagnosis established by a prostate biopsy were included. Histopathology reports were analysed and PDL-1 immunohistochemical staining was carried out with PDL-1 monoclonal antibodies. PDL-1 expression on TCs was defined by the percentage of PDL-1 positive TCs (<1%=0 or negative, 1 to 5%=+1, ≥5%=+2). The relationship between PDL-1 expression in prostate cancer cells and clinicopathological factors like Gleason grade, lymph node positivity, perineural invasion, lymphovascular invasion, distant metastasis and Prostate Specific Antigen (PSA) level was investigated using univariate tests and multivariate logistic regression analyses.

Results: Overall, high PDL-1 expression was observed in 21.7% of patients. PDL-1 positivity 1+ and 2+ was found among 11.67% and 10% cases, respectively. Significantly higher expression (p-value <0.05) of PDL-1 was noted in cases with higher preoperative PSA levels (>40), high Gleason score (≥7), distant metastasis and cases with lymphovascular invasion.

Conclusion: Present study suggests that PDL-1 is associated with the tumour aggressiveness in prostate cancer patients and can be used for the identification of more aggressive diseases.