Determination of PD-L1 expression in renal cell carcinoma using immunohistochemical and PCR (Polymerase chain reaction) methods

Determination of PD-L1 Expression in Renal Cell Carcinoma Using Immunohistochemical and PCR (Polymerase Chain Reaction) methods. Renal cell carcinoma is an immunogenic tumor which characteristically involves many tumor-infiltrating lymphocytes. In the studies, renal cell carcinoma is revealed to have many features that suppress the host antitumor immunity. This made metastatic renal cell carcinomas which are unresponsive to conventional therapies, probable targets to the treatment with PD1/PD-L1 inhibitors. In our study, we determined PD-L1 expressions of 81 patients who underwent radical nephrectomy between 2008-2013 by using immunohistochemical (Anti PD-L1 antibody [28-8, ab205921], RabMAb, abcam) and quantitative real time PCR methods. We aimed to investigate the correlation between PD-L1 expression and prognostic features such as metastasis, stage and survival to contribute to the literature. Also, we aimed to evaluate convenient methods to guide patient selection for PD1/PD-L1 inhibitors treatment. Our patient group consists of clear cell, chromophobe cell and papillary subtypes and PD-L1 expression rate is %19,75. We found a borderline statistic correlation between PD-L1 expression and metastasis (p=0,054). There was no significant relationship between PD-L1 and other clinical and prognostic parameters such as gender, age, mortality rates, histologic subtype, clinical stage, nuclear grade, sarcomatoid/rhabdoid differentiation, necrosis, tumor infiltration in kidney capsule, invasion into renal pelvis and hilar fat tissue, tumor size and survival. When we compared immunohistochemical testing with quantitative real time PCR method in determining the expression of PD-L1, we found that the sensitivity of immunohistochemistry is weak. In our results, we found no statistically significant relationship between PD-L1 and prognostic parameters but we think PD-L1 expression can be used as a complementary diagnostic test in selecting patients for PD1/PD-L1 inhibitor treatment. Also in determining PD-L1 expression, we recommend using immunohistochemical and PCR methods together to eliminate the variations in the literatüre about staining and scoring interpretations for standardization. Key Words: Renal cell carcinoma, PD-L1, immunohistochemistry, PCR