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

Colorectal cancer 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 IFNγ. Recent studies have 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 roles of miR-93-5p and miR-142-5p expression and the levels of IFNγ 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 by a method for quantitative measurement of human microRNA (miREIA). The concentrations of PD-L1 and IFNγ were determined by the ELISA kit. We found higher concentrations of miR-93-5p, PD-L1 and IFNγ in tumor samples compared to tumor margin samples. A significant correlation was found between PD-L1 and IFNγ 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, IFNγ and miR-93-5p expression. Understanding the mechanisms underlying intratumoral PD-L1 expression may open new opportunities for targeted immunotherapy for colorectal cancer.