Role of miR-944/MMP10/AXL- axis in lymph node metastasis in tongue cancer.

Occult lymph-node metastasis is a crucial predictor of tongue cancer mortality, with an unmet need to understand the underlying mechanism. Our immunohistochemical and real-time PCR analysis of 208 tongue tumors show overexpression of Matrix Metalloproteinase, MMP10, in 86% of node-positive tongue tumors (n = 79; p < 0.00001). Additionally, global profiling for non-coding RNAs associated with node-positive tumors reveals that of the 11 significantly de-regulated miRNAs, miR-944 negatively regulates MMP10 by targeting its 3'-UTR. We demonstrate that proliferation, migration, and invasion of tongue cancer cells are suppressed by MMP10 knockdown or miR-944 overexpression. Further, we show that depletion of MMP10 prevents nodal metastases using an orthotopic tongue cancer mice model. In contrast, overexpression of MMP10 leads to opposite effects upregulating epithelial-mesenchymal-transition, mediated by a tyrosine kinase gene, AXL, to promote nodal and distant metastasis in vivo. Strikingly, AXL expression is essential and sufficient to mediate the functional consequence of MMP10 overexpression. Consistent with our findings, TCGA-HNSC data suggests overexpression of MMP10 or AXL positively correlates with poor survival of the patients. In conclusion, our results establish that the miR-944/MMP10/AXL- axis underlies lymph node metastases with potential therapeutic intervention and prediction of nodal metastases in tongue cancer patients.

The Hox gene Abdominal-B uses DoublesexF as a cofactor to promote neuroblast apoptosis in the Drosophila central nervous system.

Highly conserved DM domain-containing transcription factors (Doublesex/MAB-3/DMRT1) are responsible for generating sexually dimorphic features. In the Drosophila central nervous system, a set of Doublesex (Dsx)-expressing neuroblasts undergo apoptosis in females whereas their male counterparts proliferate and give rise to serotonergic neurons crucial for adult mating behaviour. Our study demonstrates that the female-specific isoform of Dsx collaborates with Hox gene Abdominal-B (Abd-B) to bring about this apoptosis. Biochemical results suggest that proteins AbdB and Dsx interact through their highly conserved homeodomain and DM domain, respectively. This interaction is translated into a cooperative binding of the two proteins on the apoptotic enhancer in the case of females but not in the case of males, resulting in female-specific activation of apoptotic genes. The capacity of AbdB to use the sex-specific isoform of Dsx as a cofactor underlines the possibility that these two classes of protein are capable of cooperating in selection and regulation of target genes in a tissue- and sex-specific manner. We propose that this interaction could be a common theme in generating sexual dimorphism in different tissues across different species.

Combinatorial action of Grainyhead, Extradenticle and Notch in regulating Hox mediated apoptosis in Drosophila larval CNS.

Hox mediated neuroblast apoptosis is a prevalent way to pattern larval central nervous system (CNS) by different Hox genes, but the mechanism of this apoptosis is not understood. Our studies with Abdominal-A (Abd-A) mediated larval neuroblast (pNB) apoptosis suggests that AbdA, its cofactor Extradenticle (Exd), a helix-loop-helix transcription factor Grainyhead (Grh), and Notch signaling transcriptionally contribute to expression of RHG family of apoptotic genes. We find that Grh, AbdA, and Exd function together at multiple motifs on the apoptotic enhancer. In vivo mutagenesis of these motifs suggest that they are important for the maintenance of the activity of the enhancer rather than its initiation. We also find that Exd function is independent of its known partner homothorax in this apoptosis. We extend some of our findings to Deformed expressing region of sub-esophageal ganglia where pNBs undergo a similar Hox dependent apoptosis. We propose a mechanism where common players like Exd-Grh-Notch work with different Hox genes through region specific enhancers to pattern respective segments of larval central nervous system.