Efficacy of the MEK Inhibitor Cobimetinib and its Potential Application to Colorectal Cancer Cells.
BACKGROUND/AIMS
Mutations in the Ras/Raf/MEK/ERK pathway are detected in 50% of colorectal cancer cases and play a crucial role in cancer development and progression. Cobimetinib is a MEK inhibitor approved for the treatment of advanced melanoma and inhibits the cell viability of other types of cancer cells.


METHODS
HCT116 colorectal cancer cells were treated with cobimetinib, and MTT assay, colony formation assay, and flow cytometry were used to evaluate cell viability, cell cycle, and apoptosis, respectively. The expression of genes associated with the cell cycle and apoptosis were evaluated by quantitative real-time PCR and western blotting. To explore use of cobimetinib in colorectal cancer treatment and further understand its mechanisms, RNA-seq technology was used to identify differentially expressed genes (DEGs) between cobimetinib-treated and untreated HCT116 cells. Furthermore, we compared these DEGs with Gene Expression Omnibus data from colorectal cancer tissues and normal colonic epithelial tissues.


RESULTS
We found that cobimetinib not only inhibited cell proliferation but also induced G1 phase arrest and apoptosis in HCT116 colorectal cancer cells, suggesting that cobimetinib may useful in colorectal cancer therapy. After cobimetinib treatment, 3,495 DEGs were obtained, including 2,089 upregulated genes and 1,406 downregulated genes, and most of these DEGs were enriched in the cell cycle, DNA replication, and DNA damage repair pathways. Our results revealed that some genes with high expression in colorectal cancer tissues were downregulated by cobimetinib in HCT116 cells, including CCND1, E2F1, CDC25C, CCNE2, MYC, and PCNA. These genes have vital roles in DNA replication and the cell cycle. Furthermore, genes with low expression in colorectal cancer tissues were upregulated by cobimetinib, including PRKCA, PI3K, RTK, and PKC. Based on our results, the PKC and PI3K pathways were activated after cobimetinib treatment, and inhibition of these two pathways can increase the cytotoxicity of cobimetinib in HCT116 cells. Notably, cobimetinib appeared to enhance the efficacy of 5-fluorouracil (5-FU) by decreasing TYMS expression, high expression of which is responsible for 5-FU resistance in colorectal cancer.


CONCLUSIONS
Our results suggest the potential use of cobimetinib in colorectal cancer therapy.
['Gong|Shu|S|', 'Xu|Dongsheng|D|', 'Zhu|Jialin|J|', 'Zou|Fangdong|F|', 'Peng|Rui|R|']
D017209:Apoptosis D001384:Azetidines D045744:Cell Line, Tumor D015179:Colorectal Neoplasms D019938:Cyclin D1 D050759:Cyclin-Dependent Kinase Inhibitor p21 D015536:Down-Regulation D019008:Drug Resistance, Neoplasm D005472:Fluorouracil D059585:G1 Phase Cell Cycle Checkpoints D045325:HCT116 Cells D006801:Humans D020930:MAP Kinase Kinase Kinases D019869:Phosphatidylinositol 3-Kinases D010880:Piperidines D047428:Protein Kinase Inhibitors D013940:Thymidylate Synthase D016159:Tumor Suppressor Protein p53 D015854:Up-Regulation
Cobimetinib Colorectal Cancer Cancer therapy Thymidylate synthetase