Tumor suppressive microRNA-133a regulates novel molecular networks in lung squamous cell carcinoma

Analysis of the microRNA (miRNA) expression signature of lung squamous cell carcinoma (lung-SCC) revealed that the expression levels of miR-133a were significantly reduced in cancer tissues compared with normal tissues. In this study, we focused on the functional significance of miR-133a in cancer cell lines derived from lung-SCC and the identification of miR-133a-regulated novel cancer networks in lung-SCC. Restoration of miR-133a expression in PC10 and H157 cell lines resulted in significant inhibition of cell proliferation, suggesting that miR-133a functions as a tumor suppressor. We used genome-wide gene expression analysis to identify the molecular targets of miR-133a regulation. Gene expression data and web-based searching revealed several candidate genes, including transgelin 2 (TAGLN2), actin-related protein2/3 complex, subunit 5, 16kDa (ARPC5), LAG1 homolog, ceramide synthase 2 (LASS2) and glutathione S-transferase pi 1 (GSTP1). ARPC5 and GSTP1 likely represent bona fide targets as their expression is elevated in lung-SCC clinical specimens. Furthermore, transient transfection of miR-133a, repressed ARPC5 and GSTP1 mRNA and protein levels. As cell proliferation was significantly inhibited in lung-SCC cells following RNAi knock down of either gene, ARPC5 and GSTP1 may function as oncogenes in the development of lung-SCC. The identification of a tumor suppressive miRNA and the novel cancer pathways it regulates could provide new insights into potential molecular mechanisms of lung-SCC carcinogenesis.     

Tumour suppressive microRNA-874 regulates novel cancer networks in maxillary sinus squamous cell carcinoma

Background:

On the basis of the microRNA (miRNA) expression signature of maxillary sinus squamous cell carcinoma (MSSCC), we found that miR-874 was significantly reduced in cancer cells. We focused on the functional significance of miR-874 in cancer cells and identification of miR-874-regulated novel cancer networks in MSSCC.

Methods:

We used PCR-based methods to investigate the downregulated miRNAs in clinical specimens of MSSCC. Our signature analyses identified 23 miRNAs that were significantly reduced in cancer cells, such as miR-874, miR-133a, miR-375, miR-204, and miR-1. We focused on miR-874 as the most downregulated novel miRNA in our analysis.

Results:

We found potential tumour suppressive functions such as inhibition of cancer cell proliferation and invasion. A molecular target search of miR-874 revealed that PPP1CA was directly regulated by miR-874. Overexpression of PPP1CA was observed in MSSCC clinical specimens. Silencing of the PPP1CA gene significantly inhibited cancer cell proliferation and invasion.

Conclusion:

The downregulation of miR-874 was a frequent event in MSSCC, which suggests that miR-874 functions as a tumour suppressive miRNA, directly regulating PPP1CA that has a potential role of an oncogene. The identification of novel miR-874-regulated cancer pathways could provide new insights into potential molecular mechanisms of MSSCC oncogenesis.