Purpose: Highly aggressive adult soft tissue sarcomas (STS), i.e., leiomyosarcomas (LMS) and undifferentiated pleomorphic sarcomas (UPS), present complex genomic anomalies and overall 5-year survival rates of 20 to 40%. Here, we aimed to identify new biomarkers that may be employed to improve the treatment of non-translocation STS patients. We validated 12 miRNAs implicated in tumor development using primary STS samples and selected miR-152 for further analysis in STS-derived cell lines.
Methods: 59 primary STS samples (27 LMS and 32 UPS) and 10 matched normal control tissues were included in the study, as well as 3 STS-derived cell lines (HT1080, SW872 and SKLMS1) and a normal control mesenchymal cell line (hMSC). miRNA expression analyses were performed using a TaqMan microRNA Array platform and qRT-PCR (miR-152), respectively. The expression levels of the putative miR-152 targets MET and KIT were assessed using qRT-PCR and immunohistochemistry on tissue microarrays, respectively. In addition, various functional analyses were performed before and after miR-152 transfection into SKLMS1 cells.
Results: We found that 12 pre-selected miRNAs were down-regulated in primary STS tumor samples compared to its normal control samples. A statistically significant miR-152 down-regulation was found to be accompanied by high MET and KIT mRNA levels in both the primary samples and the STS-derived cell lines tested. miR-152 transfection in SKLMS1 cells led to a reduction in KIT and MET mRNA and protein levels which, in turn, was associated with a transient down-regulation of the PI3K/AKT pathway, a transient decrease in cell growth, and a transient increase in both apoptotic and S-phase cells.
Conclusions: Our data indicate that over-expression of MET and KIT in primary STS samples and its derived cell lines is associated with miR-152 down-regulation. This shift may play a role in STS development and, thus, may be used to identify patients at risk. The effect of MET down-regulation on downstream signaling pathways, such as the PI3K/AKT pathway, may provide a basis for the future design of novel STS treatment strategies.
Keywords: Met; New targets; Soft tissue sarcoma; miR-152.