Octreotide induces caspase activation and apoptosis in human hepatoma HepG2 cells.

AIM: To investigate the role of octreotide on cellular proliferation and apoptosis of human hepatoma (HepG2) cells. METHODS: We studied cellular proliferation, apoptosis and the possible internal caspase-mediated apoptosis pathway involved, after treatment of HepG2 carcinoma cells with octreotide in comparison with the apoptosis caused by tumor necrosis factor-α (TNF-α). Activities of caspase-3, caspase-9, caspase-8 and caspase-2 were studied, while apoptosis was investigated through detection of DNA fragmentation and through identification of apoptotic cells with the annexin-V/propidium iodide flow cytometric method. RESULTS: After an initial increase in HepG2 cellular proliferation, a significant inhibition was observed with 10⁻8 mol/L octreotide, while TNF-α dose-dependently decreased proliferation. Early and late apoptosis was significantly increased with both substances. Octreotide significantly increased caspase-3, caspase-8 and caspase-2 activity. TNF-α significantly increased only caspase-2. Cellular proliferation was decreased after treatment with octreotide or TNF-α alone but, in contrast to TNF-α, octreotide decreased proliferation only at concentrations of 10⁻8 mol/L, while lower concentrations increased proliferation. CONCLUSION: Our findings are suggestive of caspase-mediated signaling pathways of octreotide antitumor activity in HepG2 cells, and indicate that measurements of serum octreotide levels may be important, at least in clinical trials, to verify optimal therapeutic drug concentrations.

A concentration-dependent effect of ursodeoxycholate on apoptosis and caspases activities of HepG2 hepatocellular carcinoma cells.

Clinical observations suggest that ursodeoxycholate (UDCA) may protect from hepatocellular carcinoma in cirrhotic patients. Increased apoptosis of malignant cells is a candidate mechanism. Decreased apoptosis of cholangiocytes is proposed as a mechanism for the favourable effect of UDCA in primary biliary cirrhosis. We therefore studied the effects of different concentrations of UDCA on HepG2 cell proliferation, apoptosis and caspases activities. Apoptotic features and activities of the effector or initiator caspases-8, -9, -3 and -2 after treatment of HepG2 cells with different concentrations of UDCA alone or in combination with TNF-alpha were examined. Apoptosis was detected by DNA fragmentation and flow cytometric determination of apoptotic cells with Annexin-V/PI. UDCA significantly inhibits cell proliferation only at high concentrations, but increases apoptosis at low concentrations and protects from apoptosis at higher concentrations. TNF-alpha induced DNA fragmentation is potentiated by UDCA, but flow cytometry indicates protection from early apoptosis and increase in cell survival by low and intermediate UDCA concentrations. UDCA differentially activates initiator and effector caspases in different concentrations. These data demonstrate that the effect of UDCA on caspase activation and apoptosis of HepG2 cells is concentration-dependent and activation of the caspase cascade is not always translated into increased apoptosis. Serum levels of UDCA should be possibly monitored and dosage of the drug adjusted according to the required effect.