API5 induces cisplatin resistance through FGFR signaling in human cancer cells

Most tumors frequently undergo initial treatment with a chemotherapeutic agent but ultimately develop resistance, which limits the success of chemotherapies. As cisplatin exerts a high therapeutic effect in a variety of cancer types, it is often used in diverse strategies, such as neoadjuvant, adjuvant and combination chemotherapies. However, cisplatin resistance has often manifested regardless of cancer type, and it represents an unmet clinical need. Since we found that API5 expression was positively correlated with chemotherapy resistance in several specimens from patients with cervical cancer, we decided to investigate whether API5 is involved in the development of resistance after chemotherapy and to explore whether targeting API5 or its downstream effectors can reverse chemo-resistance. For this purpose, cisplatin-resistant cells (CaSki P3 CR) were established using three rounds of in vivo selection with cisplatin in a xenografted mouse. In the CaSki P3 CR cells, we observed that API5 acted as a chemo-resistant factor by rendering cancer cells resistant to cisplatin-induced apoptosis. Mechanistic investigations revealed that API5 mediated chemo-resistance by activating FGFR1 signaling, which led to Bim degradation. Importantly, FGFR1 inhibition using either an siRNA or a specific inhibitor disrupted cisplatin resistance in various types of API5(high) cancer cells in an in vitro cell culture system as well as in an in vivo xenograft model. Thus, our results demonstrated that API5 promotes chemo-resistance and that targeting either API5 or its downstream FGFR1 effectors can sensitize chemo-refractory cancers.

Manganese-induced Oxidative Stress in the Corpus Striatum of the Rat Brain / 대한산업의학회지

OBJECTIVES: This study was undertaken to identify the effect of oxidative stress on the pathology of manganese intoxication through an analysis of manganese concentrations, superoxide dismutase (SOD) activities, malondialdehyde (MDA) concentrations, and the compositional changes of fatty acids from the corpus striatum of the rat brain. METHODS: Ten Sprague-Dawley rats were equally divided into two groups. Five rats in the experimental group were administered MnCl2 intraperitoneally for 4 weeks (4 mg/kg once daily, 5 days per week) and another five rats from the control group were given normal saline. Twenty-four hours after the last injection, the rats were decapitated and, the corpus striatum was isolated from the brain. RESULTS: In the corpus striatums of the experimental group, manganese concentrations increased significantly by 139 % (p<0.01). The SOD activities decreased significantly by 81 % (p<0.01) and the MDA concentrations increased significantly by 138 % (p<0.01) as compared to the control group. Among fatty acids, total n-6 polyunsaturated fatty acids (PUFAs) increased significantly by 325 % (p<0.01) as compared with the control group. Arachidonic acids (AA) increased by 341 % (p<0.01), and these increases were composed mostly of n-6 polyunsaturated fatty acids (PUFA). Among n-3 PUFAs, with the exception of linolenic acids, eicosapentanoic acid (EPA) decreased significantly by 72 % (p<0.05) and docosahexanoic acids (DHA) decreased by 67 % (p<0.05) as compared with the control group. CONCLUSIONS: Our results suggest that the oxygen free radicals produced by manganese may cause compositional changes of fatty acids in the corpus striatum of the rat brain. The characteristics of the fatty acids'compositional changes by manganese were a decrease of EPAs and DHAs (n-3 PUFAs), and an increase of AAs (n-6 PUFAs). These changes coupled with the decrease of SOD activity and the increase of MDA, suggest that manganese neurotoxicity is caused by lipid peroxidation mediated with oxygen free radicals, particularly superoxide radicals.