Inhibition of Janus Kinase 2/Signal Transducer and Activator of Transcription 3 Pathway Sensitization of LoVo Cells After 5-Chloro-2,4-Dihydroxypyridine Based 5-Fluorouracil Treatment

Gimeracil and oteracil potassium capsules (S-1) is a novel oral fluoropyrimidine derivative, 5-fluorouracil (5-FU) and 5-chloro-2,4-dihydroxypyridine (CDHP) are its main components to prevent tumor growth. The purpose of current research was to investigate the effects of combined 5-FU and CDHP treatment of colon cancer cells and assess roles of Janus Kinase 2 (JAK2)/Signal transducer and activator of transcription 3 (STAT3) signaling pathway during the therapy. Tyrphostin B42 (AG490) was used to suppress the JAK2/STAT3 signaling pathway in LoVo cells. Expression of JAK2, p-JAK2, STAT3, p-STAT3, Bcl-XL and Survivin were measured using Western blotting and qPCR. Cell cytotoxicity assay was studied by cell counting kit-8 assay. The capacity of cell proliferation and migration was investigated by clonogenic and invasion assay. Analysis of apoptosis and cell cycle was detected by flow cytometry. The results showed that 5-FU treatment with CDHP can partly prevent STAT3 phosphorylation and reduce the expression of STAT3-targeted genes Bcl-XL and Survivin, the JAK2/STAT3 signaling pathway was inhibited by AG490, which sensitized the effect of growth inhibition, migration reduction and apoptosis in LoVo cells based on 5-FU treatment with CDHP. These findings suggested that the inhibition of JAK2/STAT3 signaling pathway suppressed the malignant phenotype and increased apoptosis of colorectal cancer cells after combined CDHP and 5-FU treatment. Combining JAK2/STAT3 inhibitors with chemotherapy is a rational approach for future drug development for treatment of colorectal cancer.