Regulation of Cancer Aggressive Features in Melanoma Cells by MicroRNAs

MicroRNAs (miRNAs) are small non-coding RNAs with regulatory roles, which are involved in a broad spectrum of physiological and pathological processes, including cancer. A common strategy for identification of miRNAs involved in cell transformation is to compare malignant cells to normal cells. Here we focus on identification of miRNAs that regulate the aggressive phenotype of melanoma cells. To avoid differences due to genetic background, a comparative high-throughput miRNA profiling was performed on two isogenic human melanoma cell lines that display major differences in their net proliferation, invasion and tube formation activities. This screening revealed two major cohorts of differentially expressed miRNAs. We speculated that miRNAs up-regulated in the more-aggressive cell line contribute oncogenic features, while the down-regulated miRNAs are tumor suppressive. This assumption was further tested experimentally on five candidate tumor suppressive miRNAs (miR-31, -34a, -184, -185 and -204) and on one candidate oncogenic miRNA (miR-17-5p), all of which have never been reported before in cutaneous melanoma. Remarkably, all candidate Suppressive-miRNAs inhibited net proliferation, invasion or tube formation, while miR-17-5p enhanced cell proliferation. miR-34a and miR-185 were further shown to inhibit the growth of melanoma xenografts when implanted in SCID-NOD mice. Finally, all six candidate miRNAs were detected in 15 different metastatic melanoma specimens, attesting for the physiological relevance of our findings. Collectively, these findings may prove instrumental for understanding mechanisms of disease and for development of novel therapeutic and staging technologies for melanoma.

微小RNA（miRNAs）是一类具备调控功能的小型非编码RNA，广泛参与包括癌症在内的多种生理与病理过程。鉴定参与细胞转化的miRNA的常用策略，是将恶性细胞与正常细胞进行比对分析。本研究聚焦于调控黑色素瘤细胞侵袭表型的miRNA鉴定工作。为规避遗传背景差异带来的实验误差，本研究针对两株在净增殖、侵袭及管形成活性上存在显著差异的同基因人黑色素瘤细胞系，开展了高通量miRNA表达谱比对分析。此次筛选鉴定出两大组差异表达的miRNA。我们推测，在侵袭性更强的细胞系中上调的miRNA可赋予细胞致癌特性，而下调的miRNA则发挥肿瘤抑制作用。针对5个候选肿瘤抑制性miRNA（miR-31、-34a、-184、-185及-204）与1个候选致癌性miRNA（miR-17-5p）开展了实验验证，上述6个miRNA此前均未在皮肤黑色素瘤中被报道过。值得注意的是，所有候选肿瘤抑制性miRNA均能抑制细胞净增殖、侵袭或管形成能力，而miR-17-5p则可促进细胞增殖。进一步实验显示，miR-34a与miR-185可抑制植入SCID-NOD小鼠体内的黑色素瘤异种移植瘤生长。最终，我们在15份不同的转移性黑色素瘤组织标本中均检测到了这6个候选miRNA，证实了本研究发现的生理相关性。综上，本研究结果可为阐明黑色素瘤的发病机制，以及开发新型黑色素瘤治疗与分期技术提供重要依据。