miREIA - an immunoassay method for the assessment of microRNA levels in tumor tissue - a pilot study. The impact of miR-93-5p, miR-142-5p, and IFN. on PD-L1 level in colorectal cancer

Colorectal cancer (CRC) is the second and third most common cancer in females and males, respectively. The PD-L1/PD- 1 immune checkpoint is an important source of immunosuppression in the tumor microenvironment and is associated with IFN gamma. Recent studies revealed that a significant number of tumor-suppressive miRNAs can regulate the expression of PD-L1. The objective quantification of selected microRNAs using the miREIA method in CRC tissue was performed. We investigated the role of miR-93-5p and miR-142-5p expression and the levels of IFN gamma in regulating the expression of PD-L1 in tumor and margin tissues of CRC in relation to the histological grade, TNM classification, and tumor localization. 37 samples of tumor and margin tissues from CRC patients were evaluated. MiR-93-5p and miR-142-5p levels were measured using a novel method for the quantitative measurement of human microRNA (miREIA). The concentrations of PD-L1 and IFN gamma were determined using ELISA kits. We found higher concentrations of miR-93-5p, PD-L1, and IFN gamma in tumor samples compared to the tumor margin samples. A significant correlation was found between PD-L1 and IFN gamma levels in tumor and margin specimens; between miR-142-5p and miR-93-5p levels in tumor and margin specimens. A higher level of miR-93-5p was found in tumor margin tissues on the left side of the colon. Patients with distant metastases were characterized by higher miR-93-5p concentration compared to patients without metastases. CRC is an important source of PD- L1, IFN gamma, and miR-93-5p expression. Understanding the mechanisms underlying intratumoral PD-L1 expression may create new opportunities for targeted immunotherapy of colorectal cancer.