The Regulation of miRNA-211 Expression and Its Role in Melanoma Cell Invasiveness

Abstract

The immediate molecular mechanisms behind invasive melanoma are poorly understood. Recent studies implicate microRNAs (miRNAs) as important agents in melanoma and other cancers. To investigate the role of miRNAs in melanoma, we subjected human melanoma cell lines to miRNA expression profiling, and report a range of variations in several miRNAs. Specifically, compared with expression levels in melanocytes, levels of miR-211 were consistently reduced in all eight non-pigmented melanoma cell lines we examined; they were also reduced in 21 out of 30 distinct melanoma samples from patients, classified as primary in situ, regional metastatic, distant metastatic, and nodal metastatic. The levels of several predicted target mRNAs of miR-211 were reduced in melanoma cell lines that ectopically expressed miR-211. In vivo target cleavage assays confirmed one such target mRNA encoded by KCNMA1. Mutating the miR-211 binding site seed sequences at the KCNMA1 3′-UTR abolished target cleavage. KCNMA1 mRNA and protein expression levels varied inversely with miR-211 levels. Two different melanoma cell lines ectopically expressing miR-211 exhibited significant growth inhibition and reduced invasiveness compared with the respective parental melanoma cell lines. An shRNA against KCNMA1 mRNA also demonstrated similar effects on melanoma cells. miR-211 is encoded within the sixth intron of TRPM1, a candidate suppressor of melanoma metastasis. The transcription factor MITF, important for melanocyte development and function, is needed for high TRPM1 expression. MITF is also needed for miR-211 expression, suggesting that the tumor-suppressor activities of MITF and/or TRPM1 may at least partially be due to miR-211's negative post transcriptional effects on the KCNMA1 transcript. Given previous reports of high KCNMA1 levels in metastasizing melanoma, prostate cancer and glioma, our findings that miR-211 is a direct posttranscriptional regulator of KCNMA1 expression as well as the dependence of this miRNA's expression on MITF activity, establishes miR-211 as an important regulatory agent in human melanoma.

BRAF V600 inhibition alters the microRNA cargo in the vesicular secretome of malignant melanoma cells

“…5B). Furthermore, it has been shown that MITF regulates TRPM1 gene expression as well as the expression of miR-211-5p, as it resides in the sixth intronic region of TRPM1 (21,22). A significant up-regulation of TRPM1 was confirmed by qPCR (Fig.…”

Identification of microRNAs associated with invasive and aggressive phenotype in cutaneous melanoma by next-generation sequencing

“…18 miR-211 functions as a metabolic switch 19 and as a potent tumor suppressor in vitro influencing gene pathways involved in cell invasion. [20][21][22] It is located within the noncoding sequence (intron 6) of Melastatin-1 (MLSN-1) gene, 20 which is expressed at high levels in melanocytic nevi but significantly reduced in metastatic melanomas with variable expression in primary lesions. 23 Loss of MLSN-1 mRNA is predictive of significantly reduced disease-free survival of melanoma patients.…”

Signaling Pathways Altered During the Metastatic Progression of Melanoma

“…In comparison with miRNAs that are overexpressed in melanoma, little is known about miRNAs that are diminished during melanoma progression [127], so even less is known about miRNAs downregulated in melanoma metastasis. Fortunately, there is some information in this area and we will present it here.…”