β-(1 → 3) Linked Sulfated Polygalactan from a Seaweed-associated Bacillus velezensis MTCC 13097: A Potential Lead Against Human Hepatocellular Adenocarcinoma

Abstract

Among tumors, liver cancer has an inferior prognosis. Therefore, exploring alternative strategies to improve the effectiveness of treatment for this ailment is of utmost urgency. In this study, we focused on analyzing the anti-cancer properties of bacterial exopolysaccharide from Bacillus velezensis associated with the seaweed Sargassum wightii against hepatocellular adenocarcinoma. A culture-dependent method was used to isolate heterotrophic B. velezensis, which was then evaluated for its antioxidant and anti-cancer properties. A β-(1 → 3) linked sulfated polygalactan exopolysaccharide (BVEP-2) was isolated from the bacterial extract and characterized by spectroscopic analysis. The anti-cancer property was analyzed through assays involving 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), neutral red uptake (NRU), and apoptosis (by annexin V-FITC/PI staining) against the human hepatocellular adenocarcinoma cell line (HepG2). BVEP-2 demonstrated potential cytotoxicity in the MTT assay (IC₅₀ 65.05 μg/mL) and 23.02% cell viability in the NRU assay at a 100 µg/mL concentration of BVEP-2 against HepG2, compared to the standard doxorubicin. Potential antioxidant properties of BVEP-2 (IC₅₀ 112–117 µg/mL) corroborated the anti-cancer activities, and the attenuation of free radicals could play a significant role in its anti-cancer potential. BVEP-2 induced approximately 9% early apoptosis and 39% late apoptosis in the HepG2 cell line, whereas the standard drug resulted in around 38% early apoptosis and 37% late apoptosis, along with 6% necrotic cells. The β-(1 → 3) linked sulfated polygalactan exopolysaccharide (BVEP-2) of B. velezensis MTCC13097 showed potential antioxidant and anti-cancer activities, and thus, could be developed as a promising pharmacophore lead against human hepatocellular adenocarcinoma.

Graphical Abstract