Association of PD-L1 immunoexpression with tumor grade in colorectal adenocarcinoma

Globally, colorectal cancer (CRC) is the primary cause of cancer-related deaths, and in emerging countries, its prevalence is continuously increasing. With all the advancements in surgery and treatment, the outlook for CRC patients is still not good. Even with the use of standard prognostic markers, there are presently no effective prognostic techniques for colorectal cancer. The long-term survival of many malignancies has been significantly enhanced by immune checkpoint blockades (ICB), suggesting that the immune checkpoint mechanism is crucial in inhibiting tumor-specific immune responses in the tumor microenvironment. By inhibiting T effector cell activity, the "PD-1 (programmed cell death-1)"/PD-L1 (programmed cell death-ligand 1) axis contributes significantly to immune suppression control and allows tumor cells to evade the host's anti-tumor immune surveillance. While early study suggested that immunotherapy was not relevant for patients with colorectal cancer, more recent studies have demonstrated that immunotherapy was beneficial for a certain subset of patients. This suggests that the prognosis prediction of colorectal cancer may benefit from a thorough evaluation of the local immune response. This study set out to assess the association between PD-L1 immunoexpression and tumor grade in CRC. : This was a cross-sectional observational study. Paraffin blocks of total 64 cases were selected from the patients who were diagnosed as adenocarcinoma from resected samples received in the department of pathology at BSMMU from July 2021 to June 2023. Immuno-histochemical staining for PD-L1 was performed using 28-8 clone along with appropriate positive control. In this study, PD-L1 immuno-expression was found in 14(21.9%) out of 64 cases. However, no expression was found in rest of the 50 (78.1%) cases. This study showed association of PD-L1 expression with high grade (Grade-3) tumors. : Evaluation of expression of PD-L1 may emerge as a new marker and target for the immunotherapy of colorectal cancer.