Silencing of SiX-4 enhances the chemosensitivity of melanoma cells to Cisplatin.

Melanoma is the riskiest type of skin cancer. Its prevalence has been rapidly increased over the last three decades. SIX1, SIX2, SIX3, SIX4, SIX5, and SIX6 are members of the sine oculis homeobox (SIX) homolog family. It is imperative to identify new melanoma biomarkers to improve the predictive value for melanoma prognosis, which could enhance our understanding of carcinogenesis and tumor progression. In this study, we investigated whether silencing of SIX4 in a melanoma cell line (A375 cells) in combination with Cisplatin can affect the apoptosis and suppression of cell cycle progression, migration of the melanoma cells. MTT test and colony formation assay was applied to determine the IC50 of Cisplatin and the combined effect of SIX4 siRNA and Cisplatin on the viability and clonogenesis of the A-375 cells. qRT-PCR was performed to determine the c-myc, BCL-2, BAX, MMP-9, CXCR4, and Rock genes expression. Furthermore, flow cytometry was applied to evaluate apoptosis, autophagy, and the cell cycle status in different groups. Finally, wound healing assay was employed to evaluate the effect of this combination therapy on migratory capacity. SIX4 suppression increased the chemosensitivity of A-375 cells to Cisplatin and decreased its efficient dose. Furthermore, SIX4 suppression alongside Cisplatin reduced cell migration rate, arrested the cell cycle at the G1 phase, induced apoptosis by modulating the expression of apoptotic target genes, induced autophagy, and also significantly inhibits clonogenesis of A-375 cells. SIX4 plays a significant role in the chemosensitivity and pathogenesis of melanoma. Therefore, SIX4 suppression, in combination with Cisplatin, may be a promising therapeutic approach in treating melanoma.

hsa-miR-34a-5p potentiates cytarabine-mediated cell cycle arrest in MDA-MB-231 cells: a novel combination therapy.

Dysregulated cell cycle progression has been implicated in cancer development. Cytarabine can interfere with the S phase of the cell cycle; however, tumoral cells can develop chemoresistance. Specific tumor-suppressive microRNAs (miRs) replacement can arrest the cell cycle and enhance chemosensitivity. Herein, we investigated the effect of hsa-miR-34a-5p replacement and cytarabine on the cell cycle, chemosensitivity, and migration of MDA-MB-231 cells. Our in-silico results have shown that hsa-miR-34a-5p has considerable interactions with ß-catenin, CDK4, CDK6, and cyclin-D1; therefore, hsa-miR-34a-5p replacement could arrest cell cycle at the sub-G1 phase. Our in vitro results have indicated that monotherapies with hsa-miR-34a-5p replacement and cytarabine can substantially arrest the cell cycle at the sub-G1 phase; however, the maximal cell cycle arrest has been observed with the combined therapy. Ectopic overexpression of hsa-miR-34a-5p has remarkably enhanced the chemosensitivity of MDA-MB-231 cells. Also, the combined therapy has considerably suppressed the migration of MDA-MB-231 cells compared to the monotherapies. Although the combination therapy has not remarkably decreased the expression of CDK4, CDK6, and cyclin-D1 compared to monotherapy with cytarabine, the combination therapy has substantially downregulated ß-catenin expression compared to monotherapy with cytarabine. Overall, this combination therapy is a promising approach to arresting the cell cycle and migration of MDA-MB-231 cells.