Studies On Synergetic Anti-Cancer Effects And Mechenisms With Arsenic Trioxide And Octreotide

Objective: To investigate the synergetic effect of arsenic trioxide combined with octreotide on hepatocellular carcinoma and lay the foundation in clinical apply with arsenic trioxide and octreotide.Methods: 1. The MTT was used to estimate the effect of arsenic trioxide and octreotide separately and together on cultured SMMC-7721 cell in vitre. The lente concentration and combination index after 72 hours of using two drugs separately or together was calculated by Median-effect principle. 2. Cell cycle and the apoptosis index were determined by flow cytometry 3. The morphological and ultra structural changes were observed by transmission electron microscope.4. The effect of arsenic trioxide and octreotide on hepatocellular carcinoma protein expression of cyclinA, cyclin D1, p21, bcl-2 and bax was detected by immunohistochemistry. Results:Arsenic trioxide and octreotide used separately and together could inhibit the growth of SMMC-7721 cell in a time and dose dependent fashion. The lente concentrations 72 hours after using two drugs together was 2.022μmol/Land 8.088μmol/l that was lower than usage of arsenic trioxide alone (3.707μmol/l) and octreotide alone(22.637μmol/l). The combination of two drugs had a synergistic effect and the combination index was less than 1 when the response effect was more than 0.35. SMMC-7721 cell cycle was arrested in G0/G1 and S phase by arsenic trioxide(2μmol/l) and the rate of apoptosis is 11.47％.The cell cycle was stopped in S phase by octreotide(10μmol/l) and obviously arrested in G0/G1,S phase by arsenic trioxide combined with octreotide (1μmol/l arsenic trioxide plus 4μmol/l octreotide) and the rate of apoptosis is 31.94％.3. Arsenic trioxide has a down-regulation of the expression of cyclinA, cyclinD1,bcl-2 and up-regulation of the expression of p21. Octreotide has a down-regulation of the expression of cyclinA and up-regulation of the expression of p21 and bax. The down-regulation of the expression of cyclinA, cyclinD１, bcl-2 and up-regulation of the expression of p21and bax were observed in the combining usage of the two drugs. Conclusion:1. Arsenic trioxide and octreotide could inhibit the proliferation of liver cancer cells. The inhibition of HCC by usage of one drug could be markedly improved by usage of two drugs together. The combination of the two drugs have better synergistic effect. 2. Arsenic trioxide combination with octreotide could disturb cell cycle progression and arrest cell cycle in G0/G1 and S phase through down-regulation of the expression of cyclinA,cyclinD1 and up-regulation of the expression of p21.3. Arsenic trioxide can induce HCC apoptosis. Although octreotide of effect induction of apoptosis was not found, the induction effect of apoptosis was enhanced when combining with arsenic trioxide. The synergistic mechanisms on inducting apoptosis of HCC by arsenic trioxide combined with octreotide might be down-regulation the expressions of bcl-2 and up-regulation expression of bax.