SNAIL is a key regulator of alveolar rhabdomyosarcoma tumor growth and differentiation through repression of MYF5 and MYOD function

Abstract

Rhabdomyosarcoma (RMS) is a mesenchymal tumor of soft tissue in children that originates from a myogenic differentiation defect. Expression of SNAIL transcription factor is elevated in the alveolar subtype of RMS (ARMS), characterized by a low myogenic differentiation status and high aggressiveness. In RMS patients SNAIL level increases with higher stage. Moreover, SNAIL level negatively correlates with MYF5 expression. The differentiation of human ARMS cells diminishes SNAIL level. SNAIL silencing in ARMS cells inhibits proliferation and induces differentiation in vitro, and thereby completely abolishes the growth of human ARMS xenotransplants in vivo. SNAIL silencing induces myogenic differentiation by upregulation of myogenic factors and muscle-specific microRNAs, such as miR-206. SNAIL binds to the MYF5 promoter suppressing its expression. SNAIL displaces MYOD from E-box sequences (CANNTG) that are associated with genes expressed during differentiation and G/C rich in their central dinucleotides. SNAIL silencing allows the re-expression of MYF5 and canonical MYOD binding, promoting ARMS cell myogenic differentiation. In differentiating ARMS cells SNAIL forms repressive complex with histone deacetylates 1 and 2 (HDAC1/2) and regulates their expression. Accordingly, in human myoblasts SNAIL silencing induces differentiation by upregulation of myogenic factors. Our data clearly point to SNAIL as a key regulator of myogenic differentiation and a new promising target for future ARMS therapies.

Interplay among SNAIL Transcription Factor, MicroRNAs, Long Non-Coding RNAs, and Circular RNAs in the Regulation of Tumor Growth and Metastasis

“…SNAIL turned out to be also a direct regulator of not only EMT in tumor progression, but also of myogenic differentiation. The binding of SNAIL to E-box sequences in the myogenic factor 5 (MYF5) promoter and recruiting histone deacetylases (HDACs) was described in the regulation of rhabdomyosarcoma development [14]. Another example of the non-canonical actions of SNAIL is the regulation of myoblast determination protein 1 (MyoD) function in myogenic differentiation by the competitive binding of SNAIL to its regulatory sequences [15].…”

“…Members of this family target the 3 UTR of SNAIL mRNA in non-small cell lung carcinoma [62], breast cancer [63], pancreatic cancer stem cells [64], melanoma [65], esophageal squamous cell carcinoma [66], rhabdomyosarcoma [14], or in hepatocytes [67,68]. This inhibition usually regulates EMT in epithelial tumor types, but in mesenchymal tumors, such as rhabdomyosarcoma, it may be responsible for non-canonical SNAIL action [14]; it might also be important in different processes, such as atherosclerosis [69]. Moreover, miR-30a was also shown to regulate not only SNAIL but also SLUG in breast cancer to suppress EMT and metastasis [70].…”

“…The results described above are summarized in Table 1. bladder cancer [82] melanoma [83] gastric cancer [84] miR-30 family non-small cell lung carcinoma [62] breast cancer [63] pancreatic cancer [64] melanoma [65] esophageal squamous cell carcinoma [66] rhabdomyosarcoma [14] hepatocytes [67,68] breast carcinoma [71] lung carcinoma [71] ovarian cancer [72] pancreatic cancer [74] miR-122 hepatocellular carcinoma [95] miR-125b breast cancer [85] miR-130b diabetic nephropathy [100] miR-133 fibroblasts [99] miR-137 ovarian cancer [72] miR-153…”

“…As indicated previously, SNAIL is a regulator of not only EMT and cancer stem cells, but also of myogenic differentiation. In rhabdomyosarcoma, SNAIL regulates the expression of myogenic-associated miRNAs, such as miR-1, miR-206, and miR-378 [14]. What is more, the SNAIL/miR-199a-5p axis promotes the differentiation of fibroblasts into myofibroblasts by the induction of endothelial-mesenchymal transition [162].…”

“…Subsequently, those RNAs target plenty of genes to regulate tumor progression. [154] prostate cancer [157] gastric cancer [156] miR-137 SLUG binding to promoter lung cancer [167] miR-145 SNAIL binding to promoter colorectal cancer [151] SLUG binding to promoter colorectal cancer [166] miR-146a SNAIL-induced β-catenin-TCF4 complex colorectal cancer stem cells [161] miR-182 SNAIL binding to promoter breast cancer [88] miR-200 SNAIL involved in CpG DNA methylation human kidney cells [158] SLUG binding to promoter prostate cancer [168] miR-203 SNAIL binding to promoter breast cancer [86] SLUG binding to promoter breast cancer [124] miR-206 regulation by SNAIL (unknown mechanism) rhabdomyosarcoma [14] miR-221 transcriptional control by SLUG breast cancer [169] miR-375 SNAIL binding to promoter gastric cancer [152] miR-378 regulation by SNAIL (unknown mechanism) rhabdomyosarcoma [14] miR-493 SNAIL binding to promoter head and neck cancer [150] lncRNA PCA3 SNAIL binding to promoter prostate cancer [163] lncRNA TERRA transcriptional control by SNAIL mesenchymal stem cells and mammary cells [164] lncRNA HOTAIR interaction of SNAIL with HOTAIR and EZH2 hepatocytes [165] circ-ZNF652 SNAIL binding to promoter hepatocellular carcinoma [96]…”