Inhibitory effect of a gamma-oryzanol-rich fraction from purple rice extract on lipopolysaccharide-induced metastasis in human colon cancer cells.

The incidence of colon cancer recurrence and metastasis is known to increase as an adverse effect related to postoperative infection. Lipopolysaccharide or LPS, which is derived from gram-negative bacteria, is a key inducer of inflammatory-related tumor metastasis. Although there are numerous known biological effects of purple rice extract (PRE), its protective effect on colon metastasis was unknown. This study first evaluated the effects of hexane soluble fraction (HSF) or γ-oryzanol-rich fraction of PRE on LPS-induced colon cancer adhesion and invasion, which was accomplished using adhesive and invasive assay. Gelatin zymography was also utilized for gelatinase activity and secretion. Its chelating activity was also further analyzed by reverse gelatin zymography with zinc chloride. The study findings support the synergistic effect of HSF in protection against adverse events from LPS-induced colon cancer metastasis, as shown by effects on adhesive and invasive ability as well as matrix metalloproteinase-2 secretion and activity. PRACTICAL APPLICATIONS: Bacterial infection is still one of the main adverse events following abdominal cancer surgery and is associated with an increased incidence of colon cancer metastasis. Lipopolysaccharide (LPS) is a major component of this pathogen-mediated response. This first study investigated the efficiency of a gamma-oryzanol (OR) rich fraction, collected from purple rice extract (PRE), against LPS-induced colon cancer metastasis that occurs via three main steps; adhesion to the extracellular matrix, the secretion, and activity of gelatinase and further tissue invasion. The acquired data supported the role of an OR-rich fraction from PRE as a potential inhibitor to LPS-induced colon cancer progression. This finding, related to PRE, could be further developed to create a new adjunctive treatment to reduce operative complications related to bowel cancer surgery as well as increasing the value of this crop in Thailand.