Mhaidat Nizar M, Bouklihacene Mohammed, Thorne Rick F
Department of Clinical Pharmacy, Jordan University of Science and Technology, Irbid 22110, Jordan.
Department of Cancer Research Unit, Newcastle University, Newcastle, NSW 2300, Australia.
Oncol Lett. 2014 Aug;8(2):699-704. doi: 10.3892/ol.2014.2211. Epub 2014 Jun 2.
Elucidation of the molecular mechanisms by which 5-fluorouracil (5-FU) induces apoptosis is required in order to understand the resistance of colorectal cancer (CRC) cells to 5-FU. In the current study, 5-FU-induced apoptosis was assessed using the propidium iodide method. Involvement of protein kinase C (PKC) was assessed by evaluating the extent of their activation in CRC, following treatment with 5-FU, using biochemical inhibitors and western blot analysis. The results revealed that 5-FU induces varying degrees of apoptosis in CRC cells; HCT116 cells were identified to be the most sensitive cells and SW480 were the least sensitive. In addition, 5-FU-induced apoptosis was caspase-dependent as it appeared to be initiated by caspase-9. Furthermore, PKCɛ was marginally expressed in CRC cells and no changes were observed in the levels of cleavage or phosphorylation following treatment with 5-FU. The treatment of HCT116 cells with 5-FU increased the expression, phosphorylation and cleavage of PKCδ. The inhibition of PKCδ was found to significantly inhibit 5-FU-induced apoptosis. These results indicated that 5-FU induces apoptosis in CRC by the activation of PKCδ and caspase-9. In addition, the levels of PKCδ activation may determine the sensitivity of CRC to 5-FU.
为了理解结直肠癌（CRC）细胞对5-氟尿嘧啶（5-FU）的耐药性，需要阐明5-FU诱导细胞凋亡的分子机制。在本研究中，使用碘化丙啶法评估5-FU诱导的细胞凋亡。通过使用生化抑制剂和蛋白质印迹分析，评估5-FU处理后CRC中蛋白激酶C（PKC）的激活程度，以确定其参与情况。结果显示，5-FU在CRC细胞中诱导不同程度的细胞凋亡；HCT116细胞被确定为最敏感的细胞，而SW480细胞最不敏感。此外，5-FU诱导的细胞凋亡是半胱天冬酶依赖性的，因为它似乎是由半胱天冬酶-9启动的。此外，PKCɛ在CRC细胞中表达极少，5-FU处理后其切割或磷酸化水平未观察到变化。用5-FU处理HCT116细胞可增加PKCδ的表达、磷酸化和切割。发现抑制PKCδ可显著抑制5-FU诱导的细胞凋亡。这些结果表明，5-FU通过激活PKCδ和半胱天冬酶-9在CRC中诱导细胞凋亡。此外，PKCδ的激活水平可能决定CRC对5-FU的敏感性。
