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ARL4C remarkably promotes the tumorigenesis of Uveal Melanoma and may represent a potential therapeutic target

ABSTRACT: Uveal melanoma is the most common primary intraocular neoplasm, arising from melanocytes of the choroid plexus, ciliary body, and iris of the eye. The mechanism of tumorigenesis in uveal melanoma still remains unclear, resulting in poor outcomes of systemic therapies available for the treatment of uveal melanoma. Currently, ADP-ribosylation factor-like 4C (ARL4C), an ARF-Like small GTP-binding protein, has been confirmed to be closely involved in the occurrence of various tumors, including colorectal, lung, liver, gastric and ovarian cancers as well as glioblastoma. Here, we found that ARL4C was strongly expressed in uveal melanoma cells and widely distributed in the cytosol and nucleus. The proliferation and metastasis capabilities of OCM-1 and 92-1 uveal melanoma cells were significantly decreased after ARL4C knockdown both in vitro and in vivo. Furthermore, over-expression of ARL4C in ARL4C-depleted cells can significantly rescue the abilities of proliferation and metastasis in above both cells. In addition, direct injection of ARL4C small interfering RNA (siRNA) into OCM-1 cell-derived tumors inhibited tumor growth in immunodeficient mice. Therefore, ARL4C tightly participates in tumorigenesis and might represent a novel therapeutic target to uveal melanoma. We believe that small molecule drugs targeting ARL4C could be explored and further applied to clinical therapy of uveal melanoma in years or decades to come.

ORGANISM(S): Homo sapiens

PROVIDER: GSE182942 | GEO | 2024/07/10

REPOSITORIES: GEO

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Project description:Murine tooth germ development proceeds in continuous and sequential steps with reciprocal interactions between the odontogenic epithelium and the adjacent mesenchyme, and several growth factor signaling and their activation are required for tooth germ development. The expression of ADP-ribosylation factor (Arf)-like 4c (Arl4c) has been shown to induce cell proliferation, thereby involving in epithelial morphogenesis and tumorigenesis. However, other functions of Arl4c except for cellular growth are largely unknown. Although we recently demonstrated the involvement of the upregulated expression of Arl4c in cell proliferation of ameloblastoma, which has the same origin as odontogenic epithelium, its effect on tooth germ development remains unclear. Herein, single-cell RNA sequencing (scRNA-seq) analysis revealed that the expression of Arl4c, among 17 members of the Arf-family members, was specifically detected in odontogenic epithelial cells, such as stratum intermedium, stella reticulum and outer enamel epithelium, of postnatal day 1 (P1) mouse molar. In addition, scRNA-seq analysis showed higher expression of Arl4c in non-ameloblast and inner enamel epithelium, which include immature cells. In the mouse tooth germ rudiments culture, treatment with SecinH3 (an inhibitor of ARNO/Arf6 pathway) reduced the size, width and cusp height and the thickness of eosinophilic layer, which would involve the synthesis of dentin and enamel matrix organization. In addition, loss-of-function experiments using siRNAs and shRNA revealed that Arl4c expression was involved in cell proliferation and osteoblastic cytodifferentiation in odontogenic epithelial cells. Finally, RNA-seq analysis with gene set enrichment analyses (GSEA) and Gene Ontology (GO) analysis showed that osteoblastic differentiation-related gene set and/or GO terms were downregulated in shArl4c expressing odontogenic epithelial cells. These results suggest that the Arl4c-ARNO/Arf6 pathway axis contributes to tooth germ development through osteoblastic differentiation.

Project description:Analysis of DNA from fixed tissues specimens of 58 primary uveal melanomas, with known clinical outcome, to determine gene copy number variations that were associated with survival. Abstract: Uveal melanomas can be stratified into subgroups with high or low risk of metastatic death, according to the presence of gross chromosomal abnormalities. Where a monosomy 3 uveal melanoma is detected, patient survival at three years is reduced to 50%. However, approximately 5% of patients with a disomy 3 tumour ultimately develop metastasis, and a further 5% of monosomy 3 uveal melanoma patients’ exhibit disease-free survival for more than five years. Despite extensive knowledge of the chromosomal abnormalities occurring in uveal melanoma, the genes driving metastasis are not well defined. Gene copy number variations occurring in a well-characterised cohort of 58 formalin-fixed, paraffin-embedded uveal melanoma samples were identified using the Affymetrix SNP 6.0 whole genome microarray. Four genetic sub-groups of primary uveal melanoma were represented in the patient cohort: 1) disomy 3 with long-term survival; 2) metastasizing disomy 3; 3) metastasizing monosomy 3; and 4) monosomy 3 with long-term survival. Cox regression and Kaplan-Meier survival analysis identified three genes that were associated with differences in patient survival. Patients with an amplification of CNKSR3 (6q) or RIPK1 (6p) demonstrated longer survival than those with gene deletions or no copy number change (log rank, p=0.022 and p<0.001, respectively). Conversely, those patients with an amplification of PENK (8q) showed reduced survival (log rank p<0.001). CNKSR3, RIPK1 and PENK are novel candidate metastasis regulatory genes in uveal melanoma. This is the first report of amplification of a specific gene on 6p that is associated with improved uveal melanoma patient survival and suggests that the development of uveal melanomas with a propensity to metastasise may be limited by genes on 6p. 58 samples in total. Ten disomy 3 with long-term survival. Fifteen disomy 3 with metastasising. Seventeen monosomy 3 with long-term survival. Sixteen monosomy 3 metastasising.

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ARL4C remarkably promotes the tumorigenesis of Uveal Melanoma and may represent a potential therapeutic target

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