MCM7 and its hosted miR-25, 93 and 106b cluster elicit YAP/TAZ oncogenic activity in lung cancer

Lung cancer is the first cause of cancer death worldwide and the Hippo pathway transcriptional coactivators YAP/TAZ have a pro-oncogenic role in this context. In order to understand the mechanisms through which YAP/TAZ elicit their oncogenic role in different systems, many studies are focused on YAP/TAZ target genes involved in the regulation of cell proliferation/survival and migration. However, there is scarce evidence on the role of YAP/TAZ in microRNA regulation while there is increasing evidence supporting the role of microRNAs in the main oncogenic processes. Here, we showed that YAP/TAZ were able to regulate several microRNAs in non-small cell lung cancer (NSCLC) cell lines. In detail, we focused on a cluster of three oncogenic microRNAs (miR-25, 93 and 106b) hosted in the MCM7 gene that were overexpressed in lung tumors compared to normal tissues. In addition, similar behaviour was observed in breast cancer and head and neck tumor casuistries, where they showed a prognostic role. In NSCLC cells, YAP/TAZ induced the transcription of the MCM7 gene and its hosted miRs, thereby promoting cell proliferation through the post-transcriptional inhibition of the p21 cell cycle regulator. Accordingly, p21 was maintained at low levels in lung tumors compared to normal tissues. Conversely, its expression was restored in NSCLC cells upon YAP/TAZ interference or upon treatment with the statin cerivastatin. In summary, we provide evidence for a novel mechanism of modulation supporting the protumorigenic functions of the YAP/TAZ factors through the modulation of a bi-oncogenic locus consisting of one gene and three hosted microRNAs.