FBXO38 regulates ocular melanoma proliferation through the PI3K-Akt signaling pathway

Abstract

Objective·To investigate the effect of F-box only protein 38 (FBXO38) on the ocular melanoma proliferation and the potential regulatory pathway.Methods·Human skin cutaneous melanoma A375 and human uveal melanoma OMM2.3 cell lines with FBXO38 knockdown and overexpression were constructed by FBXO38 short hairpin RNA (shRNA) and FBXO38 overexpression plasmids respectively. Knockdown and overexpression efficiency of FBXO38 at transcription and protein levels were verified by using quantitative real-time PCR (qRT-PCR) and Western blotting. The effects of FBXO38 on melanoma cell proliferation were detected through clonal formation assay, BrdU immunofluorescence staining and CCK8 cell proliferation assay. By using The Cancer Genome Atlas (TCGA) database, differentially expressed genes were analyzed in the high and low expression groups of FBXO38. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment was performed to reveal the signaling pathways associated with FBXO38. CCK8 cell proliferation assay was used to detect the inhibition rates of the signaling pathway inhibitors on cells with different FBXO38 expression levels. qRT-PCR and Western blotting were used to detect whether the signaling pathway was activated after knocking down FBXO38.Results·qRT-PCR and Western blotting verified that mRNA and protein expression levels of FBXO38 in FBXO38 knockdown A375 and OMM2.3 cell lines decreased compared with the control group, while the expression levels of FBXO38 in the overexpression cell lines increased compared with wild type group (P<0.05). Clonal formation assay, BrdU immunofluorescence staining and CCK8 cell proliferation assay showed that FBXO38 knockdown significantly enhanced the proliferation of A375 and OMM2.3 cells (P<0.05), while overexpression of FBXO38 inhibited melanoma cell proliferation (P<0.05). Enrichment analysis showed that in skin cutaneous melanoma and uveal melanoma, FBXO38 expression influenced the phosphoinositide 3-kinase/protein kinase B (PI3K-Akt) pathway activation. Compared with those in the control group, the inhibition rates of PI3K inhibitor LY294002 and mTOR1 inhibitor Everolimus in the FBXO38 knockdown group significantly improved (P<0.05), while their inhibition rates of the overexpression group significantly decreased compared with those of control cells (P<0.05). Western blotting results showed that after knocking down FBXO38, expression levels of PTEN, P21 and P53 proteins decreased, while expression level of MDM2 protein increased. The qRT-PCR results showed a significant decrease in P53 transcription level (P<0.05) and a significant increase in MDM2 transcription level in FBXO38 knockdown cells (P<0.05).Conclusion·FBXO38 plays a role in regulating the proliferation of ocular melanoma, and this regulatory effect is related to the PI3K-Akt signaling pathway.

Keywords

• f-box only protein 38 (fbxo38)
• ocular melanoma
• pi3k-akt signaling pathway
• tumor proliferation