Exploring the mechanism of miR320a in regulating PDL1 upon lung cancer pathogenesis.

Abstract

The tumour suppressive role of miRNA320a is observed in many cancer types like in colon, lung, breast, and osteosarcoma but it is inversely reported in prostate cancer and in MPM cell lines. miRNA320a targets programmed death ligand 1 (PDL1) negatively in many cancer types and recently in Malignant pleural mesothelioma. In this background it is important to understand the regulatory mechanism of miRNA320a in determining PDL1 expression in different pathological stages of lung cancer. Histology was used to grade the initial and advanced stage of lung cancer following carcinogenic injection. Immunohistochemistry and Western blotting technique were used to analyse PDL1 protein expression. In-situ hybridization was used to determine miRNA320a signals. Initially, using the chemical carcinogen Diethylnitrosamine (25 μg/g), we successfully initiate initial and advanced stage of lung cancer following 6 months and 9 months of carcinogenic injection. The formation of initial and advanced stage of lung cancer is confirmed through histopathological changes which show neoplastic appearance in initial lung cancer and appearance of more mitotic cells along with tissue hardness in the advanced lung cancer stages. In miRNA320a blocked tissue the cancer condition becomes worse with decreased tissue elasticity along with more proliferative cells. Immunohistochemistry and Western blotting studies show that PDL1 is overexpressed in the advanced stages rather than in initial lung cancer because the expression of miRNA320a is overexpressed in initial stages but restricted in advanced stages of lung cancer. miRNA32a blocking studies confirm that miRNA320a expression act as a tumour suppressor that directly controls PDL1 expression that lack of miRNA320a enhances PDL1 expression as well as it triggers lung cancer advances. In summary, miRNA320a possess tumour suppressor function that limits PDL1 expression in initial lung cancer but its control over PDL1 suppression is lost once miRNA320a is downregulated in advanced stage of lung cancer.