Apoptosis of human hepatocellular carcinoma cell (HepG2) induced by cardiotoxin III through S-phase arrest

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Cytotoxin III (CTX III), a polypeptide from Naja naja atra venom, has potential in tumor therapy.
• Its efficacy in solid tumors, particularly hepatocellular carcinoma, remains largely unexplored.

Purpose of the Study:

• To investigate the effects of CTX III on hepatocellular carcinoma cell (HepG2) growth and cell cycle progression.
• To elucidate the molecular mechanisms underlying CTX III-induced apoptosis in HepG2 cells.

Main Methods:

• HepG2 cells were treated with varying doses and times of CTX III.
• Cell proliferation was assessed using IC50 determination.
• Flow cytometry and annexin V labeling were employed to analyze apoptosis and cell cycle distribution.
• Semi-quantitative RT-PCR and Western blot were used to examine gene and protein expression levels of key apoptosis and cell cycle regulators.

Main Results:

• CTX III inhibited HepG2 cell proliferation in a time- and dose-dependent manner (IC50 = 2.58 μg/mL at 24h).
• CTX III induced S-phase cell cycle arrest and increased apoptosis.
• Down-regulation of cyclins D1, A, and E at both transcriptional and translational levels was observed.
• Activation of caspase-8, -9, and -3, truncated Bid generation, cytochrome c release, and altered Bcl-2/Bax ratio were confirmed.

Conclusions:

• CTX III effectively inhibits hepatocellular carcinoma cell growth by inducing apoptosis.
• Down-regulation of cyclins, activation of caspases, and modulation of Bcl-2/Bax ratio are key mechanisms in CTX III-induced HepG2 cell apoptosis.
• CTX III demonstrates therapeutic potential for hepatocellular carcinoma treatment.