Six characteristic di-acetylated lactonic sophorolipids with C16:1, C16:0, C18:0, C18:1, C18:2, and C18:3 fatty acid were obtained from Starmerella bombicola CGMCC 1576. In order to confirm their anticancer activity against human cervical cancer cells and reveal the structure-activity relationships, their anti-proliferation effects on HeLa and CaSki cells were estimated. The cytotoxicity of sophorolipid molecules with different degrees of unsaturation was proved to be influenced by carbon chain length of sophorolipids. The longer the carbon chain length, the stronger the cytotoxicity of sophorolipids. The inhibitory mechanism of a di-acetylated lactonic C18:1 sophorolipid on HeLa cells was investigated. The cells developed many features of apoptosis and cell cycle was blocked at G0 phase and partly at G2 phase. The expression of CHOP and Bip/GRP78 was induced. Caspase-12 and caspase-3 were both activated. However, mitochondrial membrane potential and concentration of cytosolic cytochrome C did not change. The induced apoptosis of HeLa cells was probably triggered through endoplasmic reticulum signaling pathway without involvement of mitochondria. In vivo, 5, 50, and 500 mg/kg lactonic sophorolipids showed 29.90, 41.24, and 52.06 % of inhibition without significant toxicity to tumor-bearing mice, respectively. Our findings may suggest a potential use of sophorolipids in human cervical cancer treatment.
Keywords: Anticancer activity; Human cervical cancer; In vitro; In vivo; Sophorolipids.