J Cancer 2020; 11(6):1446-1456. doi:10.7150/jca.33831 This issue
1. Department of Obstetrics and Gynecology, Medical University of Innsbruck, Innsbruck, Tyrol, 6020, Austria
2. Division of Human Genetics, Medical University of Innsbruck, Innsbruck, Tyrol, 6020, Austria.
3. Institute of Pathology, Medical University of Innsbruck, Innsbruck, Tyrol, 6020, Austria.
4. Biocenter, Division of Bioinformatics, Medical University of Innsbruck, Innsbruck, Tyrol, 6020, Austria.
#Present address: Novartis - Global Drug Development Regulatory Affairs CMC, Sandoz GmbH, Langkampfen, Tyrol, 6336, Austria.
* These authors contributed equally to this work
The tumor suppressor miR-34 family is transcriptionally induced by p53. Clinical significance of the various miR-34 family members has not been studied in ovarian cancer. In 228 ovarian cancers and in 19 non-neoplastic fallopian tube samples we analysed miR-34 a/b/c expression in relation to clinicopathological characteristics and clinical outcome. We found significantly lower levels of miR-34 a/b/c in ovarian cancers as compared to control-tissues (P=0.002, P<0.001, P<0.001, respectively). Expression of miR-34 b/c revealed an inverse correlation with BRCA1/2 mRNA-expression (BRCA1: miR34 b/c P=0.002 each; BRCA2: miR-34 b/c P<0.001 each), the same was true for miR-34a and BRCA2 mRNA-expression (P<0.001). The miR-34 family expression was found to be significantly lower in type 2 in comparison to type 1 cancers (P<0.001) and in TP53-mutated compared with TP53-wild-type ovarian cancers (P<0.001, P=0.002, P=0.004, respectively). When low grade serous ovarian cancers were compared with high grade serous cancers the respective miR-34 a/b/c expression was 2.6-, 40.8- and 32.3-fold higher. The expression of each of the miR-34 family members was revealed to be of independent prognostic relevance regarding progression free survival (PFS); miR-34a: HR 0.6, P=0.033; miR-34b: HR 0.2, P=0.001 and miR-34c: HR 0.3, P=0.002, respectively). For overall survival (OS) independency of the prognostic value was confined to miR-34b (HR 0.4, P=0.016) and miR-34c (HR 0.6, P=0.049). The independency of the prognostic value of our identified thresholds was confirmed for PFS for miR-34c in a publicly available dataset (NCBI Gene Expression Omnibus GSE73582). Our findings suggest that downregulation of miR-34 family is a crucial part in ovarian cancer development. Low miR-34 levels are linked to a worse overall survival and progression free survival and may indicate a more aggressive disease.
Keywords: ovarian cancer, miR-34, p53, survival, carcinogenesis