The fucose‐specific lectin ANL from Aspergillus niger possesses anti‐cancer activity by inducing the intrinsic apoptosis pathway in hepatocellular and colon cancer cells

Abstract

The L‐fucose‐specific lectin from Aspergillus niger (ANL), isolated from the corneal smears of a keratitis patient was reported earlier. Here, we examined the interaction of ANL with human hepatocellular and colon cancer cells, evaluated its anti‐cancer activity and diagnostic potential to detect aberrantly glycosylated tumour‐associated serum glycoproteins such as alpha‐fetoprotein (AFP). We observed that ANL strongly bound to both HepG2 and HT‐29 cell‐lines and this interaction was effectively blocked with L‐fucose and mucin in a dose and time‐dependent manner with an IC50 of 1.25 and 5 μg/mL for HepG2 and HT‐29 cells respectively at 48 hours. ANL treatment increased hypodiploidy and decreased the number of HepG2 cell in G0‐G1 phase at both 24 and 48 hours. Furthermore, ANL increased the level of apoptosis in both HepG2 and HT‐29 cells in a time‐dependent manner via enhanced production of reactive oxygen species and altered mitochondrial membrane potential, indicative of intrinsic apoptotis pathway activation. Immunoblot analysis confirmed the time‐dependent elevation of levels of cytochrome c, initiator caspase‐9 and activation of caspase‐3. ANL immunohistochemistry on colon cancer tissue and quantification of AFP in HCC patient serum samples by developing an ANL‐anti‐AFP antibody sandwich enzyme‐linked immunosorbent assay confirmed the diagnostic potential of ANL. Here, interaction of ANL with AFP could be effectively blocked in the presence of competing fucose‐bearing glycans. We found ANL to be more sensitive than Lens culinaris lectin, a well‐known fucose‐specific lectin and currently used diagnostic agent. ANL can be further explored as a diagnostic and anti‐cancer agent.