Humic acid enhances the cytotoxic effects of arsenic trioxide on human cervical cancer cells

Cervical cancer is the second leading cancer affecting women, and recent studies have demonstrated arsenic trioxide (As2O3) has therapeutic effects on cervical cancer by promoting apoptosis and inhibiting metastasis in vitro and in vivo. Humic acid (HA) possesses various pharmacologic properties, including anti-inflammatory, anti-neoplastic, and anti-proliferative effects by inducing apoptosis. We examined the growth inhibition properties and the combined effects of HA and As2O3 in human cervical adenocarcinoma cell lines. Our results shown both As2O3 and HA-induced inhibition of cell growth, most likely by ROS-mediated cell damage and activation of the apoptosis pathway, and HA enhanced the anti-proliferative action of As2O3 in HeLa and SiHa cells, which reduced the LC50 about 57.62 or 73.52% (300 μg HA/mL) to 83.67 or 79.03% (500 μg HA/mL), respectively. This study is relevant to the development of chemotherapeutic approaches using As2O3 in treating human cervical cancer.