miR-7 expression in serous ovarian carcinomas

Abstract

Background/aim: miR-7 has recently been linked to cancer. Some miR-7 targets, including B-cell lymphoma 2 (BCL2) and epidermal growth factor receptor (EGFR), are involved in ovarian cancer (OC) pathogenesis. The majority of OCs display TP53 mutations, which are critically important for OC development. We aimed to study the expression level of miR-7 and of two of its postulated target genes, BCL2 and EGFR, in serous ovarian carcinomas of different TP53 status and tumour grade.

Materials and methods: Gene and miR expression was assessed by real-time reverse transcription polymerase chain reaction in 45 clinical samples of low- (G1+G2) and high- (G3) grade primary serous OC with wild-type (wt) or mutated TP53, as well as in three OC cell lines, each representing a different TP53 status. The results obtained in patients with OC were analysed against their disease-free survival (DFS).

Results: In high-grade OC with TP53 mutations, the level of miR-7 expression significantly exceeded (by several fold) that in wtTP53 cancer (p<0.01). Within the wtTP53 tumour series, the level of miR-7 expression was significantly higher (by over 10-fold) in high-grade than in low-grade OC (p<0.01). miR-7 expression was not found to influence DFS. The differences in miR-7 expression depending on TP53 status found in clinical OC samples were not observed in OC cell lines. miR-7 overexpression correlated with diminished BCL2 expression, but there was no relationship between miR-7 and EGFR expression, neither in tumour samples nor in the cell lines.

Conclusion: There is a link between miR-7 expression and TP53 status and tumour grade in serous OC. Molecular mechanisms of these relationships need to be elucidated. Of the two postulated miR-7 target genes we examined, BCL2, but not EGFR, seems to be a possible miR-7 target in OC.

Keywords: BCL2; EGFR; TP53 status; miR-7; ovarian cancer; tumour grade.