PhD Scientific Days 2021

PO_I_P: Pathology and Oncology I. Posters

miR-455-3p Contributes to the Downregulation of Claudin-3 Expression in the Carcinogenesis and Metastasis of Colorectal Adenocarcinomas

Text of the abstract

Introduction: Carcinogenesis and tumor progression in colorectal cancer (CRC) are associated with altered expression of claudin (CLDN) proteins and regulatory microRNAs (miRs). However, the mechanism and the role of miRs have not been fully explored yet, requiring further studies.
Aims: Our aims were to analyze the expression of claudin-1, -3, -4 and -7 and their selected potential regulatory miRNAs in primary and metastatic colorectal cancer.
Methods: Matched non-tumorous colorectal mucosa (NTM), primary CRCs and their corresponding colorectal liver metastases (CRLM) of 45 patients were included in this study. Expression of CLDN-1, -3, -4 and -7 was evaluated by immunohistochemistry and digital image analysis. Relative expression of 12 selected miRNAs was determined using TaqMan MicroRNA Assays. Target validation was performed on SW1417, DLD1 and HT29 CRC cell lines using miRCURY LNA miRNA Power Inhibitor and Western Blot analysis. Statistical analyses were performed using GraphPad Prism 5.0.
Results: Significant reduction of CLDN-1, -3 and -7 expression was observed in CRCs and CRLMs when compared with associated NTMs (p < 0.001). In addition, CLDN-1 was also decreased in CRLMs in comparison to corresponding CRCs (p < 0.05). CRCs of high histological grade exhibited lower CLDN-7 expression when compared with those of lower grade (p < 0.05). Relative expression of miR-455-3p, one of the putative regulators of CLDN-3, was elevated in CRCs and CRLMs when compared with NTMs (p < 0.001) suggesting that miRNA-455-3p might be a negative regulator of CLDN-3 expression. Inhibition of miR-455-3p in SW1417 and DLD1 cell lines resulted in increased CLDN-3 protein levels (p < 0.05). None of the observed changes of CLDN or miRNAs expression showed correlation with overall survival. Low expression of CLDN-7 in CRLM samples was associated with shorter 1-year recurrence-free survival (p < 0.05).
Conclusion: Based on our findings, the expression of CLDN-1, -3 and -7 was markedly decreased in CRCs and associated CRLMs. In addition, miR-455-3p may contribute to the downregulation of CLDN-3 expression in colorectal cancer.
Funding: This presentation was supported by grants K128881 by the National Research, Development, and Innovation Office, and EFOP-3.6.3-VEKOP-16-2017-00009 („Development of Scientific Workshops of Medical, Health Sciences and Pharmaceutical Education”).

University and Doctoral School

Semmelweis University, Doctoral School of Pathological Sciences