Non-coding RNAs and Extracellular Vesicles in Cutaneous Squamous Cell Carcinoma

Abstract: Cutaneous squamous cell carcinoma (cSCC) ranks among the most widespread malignancies with metastatic potential. Investigating the molecular mechanism of tumorigenesis will enhance our understanding of cSCC. Aberrant expression of non-coding RNAs has been extensively reported in human cancers. Here, we summarize our work exploring the role of a microRNA (miRNA) (Paper I) and a long non-coding RNA (lncRNA) (Paper II and III) in cSCC. Additionally, we discuss the role of cSCC-derived extracellular vesicles (EVs) in tumor formation (Paper IV).In Paper I, we explored the function of miR-130a in cSCC. We reported that miR-130a expression was downregulated in cSCC under the regulation of the MAPK pathway. We demonstrated a tumor suppressor role of miR-130a in cSCC: ectopic overexpression of miR-130a suppressed malignant behaviors of human cSCC cells and inhibited primary tumor growth in cSCC xenograft models. Mechanistically, we revealed a link between MAPK and BMP/SMAD signaling pathways, which was mediated by the direct target of miR-130a, ACVR1. In Paper II, we investigated the role of lncRNA PVT1 in cSCC. Elevated PVT1 expression in cSCC, under MYC regulation, suggested it may contribute to keratinocyte transformation. Subsequently, we revealed that PVT1 exerted an oncogenic role in cSCC through regulating CDKN1A/p21 expression and preventing cellular senescence. We identified exon 2 as a crucial element for maintaining PVT1's oncogenic role. In Paper III, we further investigated the underlying mechanism for the oncogenic role of PVT1 in cSCC. Our data revealed that PVT1 is mainly distributed in the nuclei of cSCC cells and the exon 2 is essential for nuclear localization of PVT1. Furthermore, we identified several subunits of the transcription-export (TREX) complex as interacting partners of PVT1 and demonstrated that PVT1 modulated the function of the TREX complex in nuclear export of poly (A)+ RNAs.In Paper IV, we found that cSCC cells secreted more EVs than primary keratinocytes. Blocking cSCC EV production suppressed xenograft growth, indicating a crucial role of cSCC cell-derived EVs in tumor development. Transcriptome analysis on xenograft tissues suggested that cSCC cell-derived EVs contribute to extracellular matrix organization. Further experiments indicated that metastatic cSCC cell-derived EVs efficiently educated dermal fibroblasts into cancer-associated fibroblasts. Additionally, metastatic cSCC cell-derived EVs activated the TGFβ signaling pathway in dermal fibroblasts. Collectively, our study suggested that cSCC cell-derived EVs play a key role in regulating cSCC development through modulating cancer-stroma communication.