Jian-Zhen Shan1, Yan-Yan Xuan2, Qi Zhang3, Jian-Jin Huang1. 1. Department of Medical Oncology, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China. 2. Cancer Institute of Zhejiang University, Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education, Hangzhou 310009, China. 3. Department of General Surgery, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China.
Abstract
OBJECTIVE: To explore the efficacy of ursolic acid in sensitizing colon cancer cells to chemotherapy under hypoxia and its underlying mechanisms. METHODS: Three colon cancer cell lines (RKO, LoVo, and SW480) were used as in vitro models. 5-Fluorouracil (5-FU) and oxaliplatin were used as chemotherapeutic drugs. Cell viability and apoptosis were tested to evaluate the sensitivity of colon cancer cells to chemotherapy. The transcription and expression levels of hypoxia-inducible factor-1α (HIF-1α), multidrug resistance gene 1 (MDR1), and vascular endothelial growth factors (VEGF) were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) and immunoblotting. Cycloheximide and MG132 were used to inhibit protein synthesis and degradation, respectively. In vitro tube formation assay was used to evaluate angiogenesis. RESULTS: We demonstrated the chemosensitizing effects of ursolic acid with 5-FU and oxaliplatin in three colon cancer cell lines under hypoxia. This effect was correlated to its inhibition of MDR1 through HIF-1α. Moreover, ursolic acid was capable of inhibiting HIF-1α accumulation with little effects on its constitutional expression in normoxia. In addition, ursolic acid also down-regulated VEGF and inhibited tumor angiogenesis. CONCLUSIONS: Ursolic acid exerted chemosensitizing effects in colon cancer cells under hypoxia by inhibiting HIF-1α accumulation and the subsequent expression of the MDR1 and VEGF.
OBJECTIVE: To explore the efficacy of ursolic acid in sensitizing colon cancer cells to chemotherapy under hypoxia and its underlying mechanisms. METHODS: Three colon cancer cell lines (RKO, LoVo, and SW480) were used as in vitro models. 5-Fluorouracil (5-FU) and oxaliplatin were used as chemotherapeutic drugs. Cell viability and apoptosis were tested to evaluate the sensitivity of colon cancer cells to chemotherapy. The transcription and expression levels of hypoxia-inducible factor-1α (HIF-1α), multidrug resistance gene 1 (MDR1), and vascular endothelial growth factors (VEGF) were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) and immunoblotting. Cycloheximide and MG132 were used to inhibit protein synthesis and degradation, respectively. In vitro tube formation assay was used to evaluate angiogenesis. RESULTS: We demonstrated the chemosensitizing effects of ursolic acid with 5-FU and oxaliplatin in three colon cancer cell lines under hypoxia. This effect was correlated to its inhibition of MDR1 through HIF-1α. Moreover, ursolic acid was capable of inhibiting HIF-1α accumulation with little effects on its constitutional expression in normoxia. In addition, ursolic acid also down-regulated VEGF and inhibited tumor angiogenesis. CONCLUSIONS:Ursolic acid exerted chemosensitizing effects in colon cancer cells under hypoxia by inhibiting HIF-1α accumulation and the subsequent expression of the MDR1 and VEGF.