Overexpression of miR-26a-2 in human liposarcoma is correlated with poor patient survival

Approximately 90% of well-differentiated/de-differentiated liposarcomas (WDLPS/DDLPS), the most common LPS subtype, have chromosomal amplification at 12q13-q22. Many protein-coding genes in the region, such as MDM2 and, have been studied as potential therapeutic targets for LPS treatment, with minimal success. In the amplified region near the MDM2 gene, our single nucleotide polymorphism (SNP) array analysis of 75 LPS samples identified frequent amplification of miR-26a-2. Besides being in the amplicon, miR-26a-2 was overexpressed significantly in WDLPS/DDLPS (P < 0.001), as well as in myxoid/round cell LPS (MRC) (P < 0.05). Furthermore, Kaplan-Meier survival analysis showed that overexpression of miR-26a-2 significantly correlated with poor patient survival in both types of LPS (P < 0.05 for WDLPS/DDLPS; P < 0.001 for MRC). Based on these findings, we hypothesized that miR-26a-2 has an important role in LPS tumorigenesis, regardless of LPS subtypes. Overexpression of miR-26a-2 in three LPS cell lines (SW872, LPS141 and LP6) enhanced the growth and survival of these cells, including faster cell proliferation and migration, enhanced clonogenicity, suppressed adipocyte differentiation and/or resistance to apoptosis. Inhibition of miR-26a-2 in LPS cells using anti-miR-26a-2 resulted in the opposite responses. To explain further the effect of miR-26a-2 overexpression in LPS cells, we performed in silico analysis and identified 93 candidate targets of miR-26a-2. Among these genes, RCBTB1 (regulator of chromosome condensation and BTB domain-containing protein 1) is located at 13q12.3-q14.3, a region of recurrent loss of heterozygosity (LOH) in LPS. Indeed, either overexpression or inhibition of RCBTB1 made LPS cells more susceptible or resistant to apoptosis, respectively. In conclusion, our study for the first time reveals the contribution of miR-26a-2 to LPS tumorigenesis, partly through inhibiting RCBTB1, suggesting that miR-26a-2 is a novel therapeutic target for human LPS.