MicroRNA miR‐196a controls melanoma‐associated genes by regulating HOX‐C8 expression

Abstract

Resulting from a screening for microRNAs differentially regulated in melanocytes and melanoma cells, we found expression of miR-196a to be significantly down-regulated in malignant melanoma cell lines and tissue samples. As it was stated before that miR-196a might negatively regulate expression of the transcription factor HOX-C8, we analyzed HOX-C8 levels in NHEMs and melanoma cells and found a strong up-regulation of HOX-C8 expression in malignant melanoma cell lines and tissue samples compared with melanocytes. Several HOX-C8 target genes are known to be involved in processes such as oncogenesis, cell adhesion, proliferation and apoptosis. We, therefore, aimed to further investigate a potential ''miR-196a fi HOX-C8 fi HOX-C8 target gene'' relationship. Stable transfection with an miR-196a expression plasmid led to strong downregulation of HOX-C8 expression in melanoma cells. Luciferase assays using reporter plasmids containing different fragments of the HOX-C8 3 0 UTR confirmed direct interactions of miR-196a with the HOX-C8 mRNA. Focusing on target genes of HOX-C8, which might play an important role in melanomagenesis, we identified three genes (cadherin-11, calponin-1 and osteopontin) that are up-or down-regulated, respectively, by altered HOX-C8 expression in miR-196a expressing cell clones and are thus indirectly regulated by this microRNA. As those target genes are closely related to important cellular mechanisms such as cell adhesion, cytoskeleton remodeling, tumor formation and invasive behavior of tumor cells, altered miR-196a expression exerts strong effects contributing to tumor cell transformation and formation and progression of malignant melanoma. This fact is underlined by a strongly reduced invasive behavior of melanoma cells re-expressing miR-196a in vitro.MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate gene expression on post-transcriptional level.

Long non-coding RNAs drive metastatic progression in melanoma (Review)

“…compiling data from several groups has enabled the coupling of differential miRNA expression in MM to specific target protein modulation and critically downstream functional consequence for disease (16)(17)(18)(19)(20)(21)(22)(23)(24). Such studies represent an emerging area of research, indeed, the prevalence of mirnas in the human transcriptome continues to expand as deep-sequencing technologies improve, with current estimates identifying ~9,000 small non-coding rnas, ~1,100 of which are potentially functional mirna transcripts (5).…”

Predictive Capacity and Functional Significance of MicroRNA in Human Melanoma

“…Notably, the micropthalmia-associated transcription factor (MITF), which is important for melanocyte development and function, is needed for high TRPM1 expression 31 , and thus, MITF contributes to miR-211 expression, suggesting that the tumor-suppressor activities of MITF may at least be partially executed through miR-211's tumor suppressing effect. MiR-196a is another documented tumor suppressor in melanoma by Dr.Bosserhoff's group 33,34 . First, they found that miR-196a was significantly down-regulated in malignant melanoma cell lines and tissue samples when screening differential miRNAs.…”

“…Re-expressing miR-196a in vitro can dramatically reduce the invasive behavior of melanoma cells, which is partially believed to account for the negative regulating expression of the transcription factor HOX-C8, which is a member belonging to the homeobox genes family. By investigating a potential "miR-196a → HOX-C8 → target gene" model, they further identified cadherin-11, calponin-1, and osteopontin as the downstream targets of miR196a 34 . Additionally, they elucidated that down-regulated miR-196a in melanoma cells leads to enhanced HOX-B7 mRNA and protein levels, another member of the homeobox genes family, which subsequently raise Ets-1 activity, another transcription factor, by inducing basic fibroblast growth factor (bFGF).…”

MicroRNAs in autophagy and their emerging roles in crosstalk with apoptosis

“…For example, MIR196 can repress several transcription factors and play a regulatory role in melanoma and acute leukemia. 67,68 Indeed, a number of genetic polymorphisms in the precursor or mature MIR196 have been © 2012 Landes Bioscience.…”