P53 ABNORMAL ENDOMETRIAL CANCERS – ANALYSIS OF PD-1 CO-EXPRESSION BY CD4 HELPER AND CD8 CYTOTOXIC T-CELL SUBTYPES IN THE TUMOR MICROENVIRONMENT

Abstract

Abstract Introduction/Objective Endometrial cancer is classified into four molecular subtypes of which the p53 abnormal variant is biologically aggressive. Programmed cell death protein 1 (PD-1) is a cell surface receptor and a vital inhibitor of the immune response. Programmed death ligand 1 (PD-L1) is a trans-membrane co-inhibitory factor of the immune response. PD-1 / PDL-1 interaction inhibits the activation and survival of T cells and decreases cytokine secretion. Some cancer cells express PD-L1, which then bind to PD-1 expressed on tumor specific T cells, and escape destruction by the T cells. The CD4/CD8 T cell immune response in the p53 abnormal variant has not been adequately evaluated with respect to the PD-1/PD-L1 pathway. Understanding this immune microenvironment is important to assess the potential use of anti-PD-1 targeted tumor therapy. Methods/Case Report Twenty cases of p53 abnormal endometrial cancers were obtained. All cases were PDL-1 +ve by immunohistochemistry. Two dual stains were performed - PD-1/CD4 and PD-1/CD8 antibodies. Six high-power fields (40x objective) with the greatest concentration of lymphocytes were counted. The total number of CD4 or CD8-only cells was recorded for each of the two stained slides for each case. The total number of PD- 1/CD4 and PD-1/CD8 positive cells were counted and recorded. The results were tabulated, and a paired t-test statistical analysis was performed to compare the total number of CD4 and CD8 cells and the percentage of PD-1/CD4 cells with the percentage of PD-1/CD8 positive cells. Results (if a Case Study enter NA) A statistically significant increase in the number of CD8 (Mean = 383) compared to CD4 cells (Mean = 317) was seen in the tumor microenvironment (p-value=0.0023). Evaluating PD-1 expression, the converse was true, and the percentage of PD-1/CD4 cells (Mean = 13.035%) was increased compared to the percentage of PD-1/CD8 cells (Mean = 9.205%), achieving statistical significance (p-value=0.0116). Conclusion The statistically significant increase in CD8 cells in the tumor and its stroma suggests that a robust cytotoxic response is being mounted to this high-risk molecular variant. The concurrent increase in CD4/PD-1 positive lymphocytes provides an appropriate microenvironment for the use of anti-PD-1 immunotherapy, since blockade of PD-1 on CD4 helper T cells may augment the tumor ablative cytotoxic properties of the CD8 positive lymphocytes. This includes reinvigoration of exhausted CD8+ T cells. Anti-PD-1 may also prevent the inhibition of PD-1 positive CD8 cells.