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 (As(2)O(3)) 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 As(2)O(3) in human cervical adenocarcinoma cell lines. Our results shown both As(2)O(3) 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 As(2)O(3) in HeLa and SiHa cells, which reduced the LC(50) about 57.62 or 73.52% (300μg HA/mL) to 83.67 or 79.03% (500μg HA/mL), respectively. This study is relevant to the development of chemotherapeutic approaches using As(2)O(3) in treating human cervical cancer.