Targeting CDC7 sensitizes resistance melanoma cells to BRAFV600E-specific inhibitor by blocking the CDC7/MCM2-7 pathway (original) (raw)

Although the utilization of selective BRAF V600E inhibitors is associated with improved overall survival in patients with metastatic melanoma, a growing challenge of drug resistance has emerged. CDC7 has been shown to be overexpressed and associated with poor prognosis in various cancers including melanoma. Thus, we aimed to elucidate the biological role of CDC7 in promoting Vemurafenib resistance and the anticipated benefits of dual targeting of BRAF V600E and CDC7 in melanoma cells. We performed exosomes-associated microRNA profiling and functional assays to determine the role of CDC7 in drug resistance using Vemurafenib-sensitive and resistant melanoma cells. Our results demonstrated that Vemurafenib-resistant cells exhibited a persistent expression of CDC7 in addition to prolonged activity of MCM2 compared to drug-sensitive cells. Reconstitution of miR-3613-3p in resistant cells downregulated CDC7 expression and reduced the number of colonies. Treatment of cells with low concentrations of CDC7 inhibitor TAK-931 sensitized resistant cells to Vemurafenib and reduced the number of cell colonies. Taken together, CDC7 overexpression and downregulation of miR-3613-3p were associated with Vemurafenib resistance in BRAF V600E-bearing melanoma cells. Dual targeting of CDC7 and BRAF V600E reduced the development of resistance against Vemurafenib. Further studies are warranted to investigate the clinical effect of targeting CDC7 in metastatic melanoma. BRAF is a driver oncogene in various human cancers including melanoma, and was the first described oncoprotein with serine/threonine kinase activity 1,2. Among all identified BRAF missense mutations, BRAF V600E with a single nucleotide transversion from valine to glutamate at position 600 is the most clinically prevalent mutation 3,4. The mutational activation of BRAF V600E increases BRAF kinase activity extremely higher than the wild-type BRAF, leading to a subsequent 4.6-fold persistent activation of ERK1/2 signaling cascade 5,6. The mutant BRAF V600E was identified as the bona fide transforming oncogene in malignant melanoma, contributing to 70% of melanoma cases 3. Due to the potential contribution of mutationally dysregulated kinases in melanomagenesis and progression, BRAF V600E was identified as a promising target for clinically effective therapeutics, including Vemurafenib 7. Vemurafenib (Zelboraf ® , PLX4032), is a potent specific inhibitor of BRAF V600E , which was the first FDA approved drug against BRAF-mutated metastatic melanoma in 2011 8. Vemurafenib effectively blocks cell growth, angiogenesis, invasion and metastasis and induce tumor cell death in BRAF V600E-associated melanomas 7,9-11. Despite the remarkable clinical benefits associated with the selective BRAF V600E inhibition by Vemurafenib, emergence of drug resistance hampered the treatment of metastatic melanoma. Approximately