SPHINX31 suppresses splicing factor phosphorylation and inhibits melanoma cell growth and aggressiveness

Jesadagorn Siriwath; Natsupa Wiriyakulsit; Patcharee Klomkleang; Chaturong Inpad; Sittiruk Roytrakul; Worasak Kaewkong

Authors

Jesadagorn Siriwath Department of Biochemistry, Faculty of Medical Sciences, Naresuan University, Phitsanulok 65000, Thailand
Natsupa Wiriyakulsit Department of Biochemistry, Faculty of Medical Sciences, Naresuan University, Phitsanulok 65000, Thailand
Patcharee Klomkleang Department of Biochemistry, Faculty of Medical Sciences, Naresuan University, Phitsanulok 65000, Thailand
Chaturong Inpad Department of Biochemistry, Faculty of Medical Sciences, Naresuan University, Phitsanulok 65000, Thailand
Sittiruk Roytrakul National Center for Genetic Engineering and Biotechnology (BIOTEC), Klong Luang, Pathumthani 12120, Thailand
Worasak Kaewkong Department of Biochemistry, Faculty of Medical Sciences, Naresuan University, Phitsanulok 65000, Thailand

Keywords:

alternative splicing, cancer phenotype, melanoma, phosphorylation, splicing factor, SRPK1

Abstract

Melanoma is a tumor resulting from the malignant transformation of skin or ocular melanocytes, and a serious health problem in countries with high UV exposure. The late detection, high invasive and metastatic potential of melanoma cells, and lack of effective treatments have led to poor prognosis and a high mortality rate among melanoma patients. The aberrant mRNA transcripts derived from alternative splicing have contributed to the progression of various types of cancer. Serine/Arginine-rich Splicing Factors (SRSFs) are responsible for mRNA splicing under the specific regulation of Serine-Arginine Protein Kinases (SRPKs). This study investigates the effects of the SRPK1-specific inhibitor SPHINX31. Cell viability was determined in A375 (cutaneous melanoma cell) in comparison to 92-1 (ocular melanoma cell) by MTT viability assays. The inhibitory effect of SPHINX31 on melanoma cell viability is presented in a dose- and time-dependent manner, with western blot analysis then performed to observe the suppression of kinase activity by SPHINX31. A decrease in phosphorylated SRSFs (pSRSFs) was demonstrated by both cells. The growth inhibition of SPHINX31 was examined by clonogenic assay, with the size and number of both A375 and 92-1 cell colonies decreasing. Remarkably, the results of SPHINX31 in other cancer phenotypes studies on A375 cells showed a significant effect on growth inhibition. The findings of this study reveal that SPHINX31 reduces the dead-evasion and migration abilities of the A375 cell. The collected data should serve as a strong foundation for developing new alternative therapeutic strategies for melanoma treatment by targeting SRPK1 activation.

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