Effects and Mechanism of Chloramphenicol on the Hypoxia-inducible Factor 1α Expression in Cancer Cells

• Main Authors: Chien-Hua Wu, 吳芊樺
• Other Authors: 康照洲
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/86889488105947286511

碩士 === 臺灣大學 === 毒理學研究所 === 95 === Chloramphenicol (CAP) is a potent, broad-spectrum, bacteriostatic antibiotic agent. It is suggested that CAP is reasonably anticipated to be a human carcinogen. Although it has been doubted to be a carcinogen for decades, there still have very limited evidence to prove the carcinogenic hypothesis. Hypoxia-inducible factor 1α(HIF-1α) is a hypoxia-sensitive transcription factor, regulating many genes that code for proteins involved in cancer progression. Overexpression of HIF-1α was associated with poor prognosis of cancer patients. Its expression was regulated via PI3K (phosphatidylinositol 3-kinase), and MAPK (mitogen-activated protein kinase) pathways. Because previous studies of our labortory showed that CAP activated PI3K and MAPK pathway, and enhanced invasion and antiapoptosis abilities of cancer cells, we further investigated whether CAP could affect HIF-1αprotein level. We used SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) and western blotting analysis for the investigation. In normoxia, the HIF-1α protein level in CAP-treated (1-100 µg/ml, 1-12hours) H1299 and A549 cells were unaffected. Interestingly, when we pretreated H1299, A549 and MCF-7 cells with CAP (1-100 µg/ml, 1 hour) and used CoCl2（cobalt chloride） as a hypoxia-mimetic agent, CAP inhibited the CoCl2-induced HIF-1α accumulation in cells. Besides, the inhibitory effect was also happened in hypoxia (0.5% O2). Short term treatment of CAP had no significant cytotoxicity on H1299 cells. The inhibitory effect of CoCl2-induced HIF-1α expression by CAP might be due to acceleration of HIF-1α degradation rate, and interfering with activation of PI3K / AKT / mTOR signaling induced by CoCl2, but not ERK1/2 signaling in H1299 cells. Both CAP and CoCl2 treatment had no obvious effect on HIF-1α mRNA expression in H1299 cells. In addition, CAP could also reduced the CoCl2-induced mRNA level elevation of VEGF (vescular endothelial growth factor) and p21, both were downstream genes regulated via HIF-1α. And it could also inhibited the CoCl2-induced VEGF165 secretion. As a whole, although CAP has been thought to be a reasonable carcinogen in the past, we proposed a possible good effect of short term treatment of CAP in cancer therapy, especially with low dose. However, we need more investigations to further confirm the benefits and toxicities of CAP.