Loss of miR-125b-1 contributes to head and neck cancer development by dysregulating TACSTD2 and MAPK pathway.

MicroRNAs (miRNAs) have important roles in the initiation and progression of human cancer, but their role in head and neck cancer development and progression is not well defined. We aimed to determine whether specific miRNAs and their target mRNAs contribute to head and neck cancer pathogenesis and progression. To identify miRNAs associated with head and neck squamous cell carcinomas (HNSCCs), we analyzed HNSCC cell lines, normal head and neck tissues and normal keratinocytes by miRNA profiling; a group of differentially expressed miRNAs was identified, which includes miR-125b. Decreased expression of miR-125b is known to occur in epithelial cancers and many target mRNAs for this miR have been reported. We found decreased expression of miR-125b-1 and hypermethylation of its promoter in HNSCC compared with its non-malignant counterpart. The TACSTD2 (also known as TROP2) gene was identified and validated as a direct target of miR-125b-1. Abnormal expression of TACSTD2 cell-surface glycoprotein has been reported in most epithelial tumors, and the overexpressions of this mRNA and protein product has been considered a useful tumor marker. We report that miR-125b-1 causes mitogen-activated protein kinase pathway dysfunction through regulation of TACSTD2 expression. Thus, loss of miR-125b-1 may have a key role in the pathogenesis and progression of squamous cell carcinomas of head and neck and possibly of other tumors.

The different epidemiologic subtypes of Burkitt lymphoma share a homogenous micro RNA profile distinct from diffuse large B-cell lymphoma.

Sporadic Burkitt lymphoma (sBL) can be delineated from diffuse large B-cell lymphoma (DLBCL) by a very homogeneous mRNA expression signature. However, it remained unclear whether all three BL variants-sBL, endemic BL (eBL) and human immunodeficiency virus-associated BL (HIV-BL)-represent a uniform biological entity despite their differences in geographical occurrence, association with immunodeficiency and/or incidence of Epstein-Barr virus (EBV) infection. To address this issue, we generated micro RNA (miRNA) profiles from 18 eBL, 31 sBL and 15 HIV-BL cases. In addition, we analyzed the miRNA expression of 86 DLBCL to determine whether miRNA profiles recapitulate the molecular differences between BL and DLBCL evidenced by mRNA profiling. A signature of 38 miRNAs containing MYC regulated and nuclear factor-kB pathway-associated miRNAs was obtained that differentiated BL from DLBCL. The miRNA profiles of sBL and eBL displayed only six differentially expressed miRNAs, whereas HIV and EBV infection had no impact on the miRNA profile of BL. In conclusion, miRNA profiling confirms that BL and DLBCL represent distinct lymphoma categories and demonstrates that the three BL variants are representatives of the same biological entity with only marginal miRNA expression differences between eBL and sBL.

Onconase mediated NFKß downregulation in malignant pleural mesothelioma.

Treatment of malignant pleural mesothelioma (MPM) with Ranpirnase (Onconase) results in disruption of protein translation and cell apoptosis. We hypothesize that Onconase exerts an effect via downregulation of nuclear factor kappa B (NFKß) by specific microRNAs (miRNAs) and that interference of this pathway could have implications for MPM resistance to chemotherapy. Three immortalized MPM cell lines (H2959, H2373 and H2591) were exposed to Onconase at 0-20 µg/ml. Cell counts were measured at 48 and 72 h. Gene expression in miRNA-enriched RNA was validated by reverse transcription-PCR (RT-PCR). The functional implications of miRNA expression were evaluated by transfecting miRNA mimics or inhibitors into MPM cell lines, and performing Matrigel invasion, cell proliferation, soft agar colony formation and scratch closure assays. Effects on NFKß expression and downstream targets including ABC transporters, BCL-xl and IAP were assessed by RT-PCR and western blotting. Treatment with 20 µg/ml of Onconase significantly decreased cell count and invasion. Hsa-miR-17* was significantly upregulated and hsa-miR-30c was significantly downregulated by Onconase treatment in all cell lines. Forced expression of hsa-miR-17* mimic and hsa-miR-30c inhibitor each significantly decreased functional activity of Onconase in all assays. NFKB1 (p50) expression and downstream targets were also decreased with Onconase treatment, as well as with forced expression of miRNA mimic and inhibitors. Onconase treatment caused a significant decrease in cell proliferation, invasion and in expression of certain miRNAs. Recapitulation of the resultant miRNA expression pattern with hsa-miR-17* mimic and hsa-miR-30c inhibitor resulted in downregulation of NFKB1 and reduced malignant behavior in functional assays. Thus, Onconase likely exerts its antitumor effect through these miRNAs.