RMEL3, a novel BRAFV600E-associated long noncoding RNA, is required for MAPK and PI3K signaling in melanoma

Abstract

Previous work identified RMEL3 as a lncRNA with enriched expression in melanoma. Analysis of The Cancer Genome Atlas (TCGA) data confirmed RMEL3 enriched expression in melanoma and demonstrated its association with the presence of BRAFV600E. RMEL3 siRNA-mediated silencing markedly reduced (95%) colony formation in different BRAFV600E melanoma cell lines. Multiple genes of the MAPK and PI3K pathways found to be correlated with RMEL3 in TCGA samples were experimentally confirmed. RMEL3 knockdown led to downregulation of activators or effectors of these pathways, including FGF2, FGF3, DUSP6, ITGB3 and GNG2. RMEL3 knockdown induces gain of protein levels of tumor suppressor PTEN and the G1/S cyclin-Cdk inhibitors p21 and p27, as well as a decrease of pAKT (T308), BRAF, pRB (S807, S811) and cyclin B1. Consistently, knockdown resulted in an accumulation of cells in G1 phase and subG0/G1 in an asynchronously growing population. Thus, TCGA data and functional experiments demonstrate that RMEL3 is required for MAPK and PI3K signaling, and its knockdown decrease BRAFV600E melanoma cell survival and proliferation.

The lncRNA RMEL3 protects immortalized cells from serum withdrawal‐induced growth arrest and promotes melanoma cell proliferation and tumor growth

“…Low levels were also observed in triple wild‐type cells (Sk‐mel147 and Mewo) and in one NF1 mutant (COLO792). These results extend previous studies by Sousa et al (), and Goedert et al () and are in agreement with them. Analysis of RMEL3 expression across melanoma specimens from 38 patients, who were attended in the Barretos Cancer Hospital (Brazil), showed a significant association of high expression of RMEL3 to extensive superficial or nodular cutaneous (16 of 31) in contrast to acral and mucosal (0 of 7) melanomas (Figure b; p = 0.014—Fisher exact test).…”

“…Most strikingly, expression mediated by a Dox‐inducible vector system caused a strong increase in clonogenic ability and also promoted tumor growth in nude mice. These data are fully consistent with the phenotype shown previously for RMEL3 knockdown (Goedert et al, ).…”

“…Previous work from our laboratory has shown that RMEL3 lncRNA is highly enriched in melanoma, particularly in tumors harboring the oncogenic BRAFV600E (Goedert et al, ; Sousa et al, ). These studies have provided first evidence of the functional relevance of this lncRNA in melanoma owning to demonstration of its restricted expression pattern and the fact that its knockdown causes cell cycle arrest and dramatic decay of melanoma cell replicative survival, especially in BRAFV600E mutant cells, while treatment with the same siRNA preserves viability of cells that do not express detectable amounts of RMEL3.…”

Oncogenic RAS Regulates Long Noncoding RNA Orilnc1 in Human Cancer

“…For example, SPRY4-IT1 (31, 32), BANCR (33), DRAIC/PCAT29 (34), CASC15 (35), MIR31HG (36), SPRIGHTLY (37), RMEL3 (38), SLNCR1 (39) and SAMMSON (40) have been proposed to serve as novel oncogenes or tumor suppressor genes in melanoma. The discovery of lncRNA cancer driver will contribute to cancer diagnosis and treatment.…”

Long non-coding RNAs in cutaneous melanoma: clinical perspectives

“…[50, 51] A positive correlation between RMEL3 expression and the presence of the BRAF V600E mutation was reported. [50] RMEL3 knockdown in melanoma cells of the A375-SM cell line resulted in the inactivation of the critical MAPK and PI3K signaling pathways.…”