Comparison of diarsenic oxide and tetraarsenic oxide on anticancer effects: relation to the apoptosis molecular pathway.

As2O3 has been reported to induce apoptosis and inhibit the proliferation of various human cancer cells. We evaluated the ability of a novel arsenic compound, As4O6, along with As2O3 in vitro and in vivo. To examine the levels of apoptosis of HPV 16-positive SiHa cervical cancer cell, flow cytometry and Western blotting were employed at various time intervals after two arsenic compound treatments. Ingenuity Pathway Analysis (IPA) was applied to investigate the differential cell death pathway of As4O6 and As2O3. The results showed that As4O6 was more effective in suppressing SiHa cell growth in vitro and in vivo compared to As2O3. In addition, the cell cycle was arrested at the sub-G1 phase by As4O6. Western blot analysis showed that the proliferating cell nuclear antigen (PCNA) and Bcl-XL with sequence homology to Bcl-2 were significantly suppressed by As4O6. However, the apoptosis-related proteins such as p21 and Bax were overexpressed by As4O6. IPA suggested that there is a significant difference between As2O3- and As4O6-induced cell death pathways. Taken together, As4O6 has a specific cell death pathway and possesses more potent anti-tumor effects on human cervical cancer cells in vitro and in vivo.

Tetraarsenic oxide-mediated apoptosis in a cervical cancer cell line, SiHa.

PURPOSE: Diarsenic oxide, As(2)O(3), has been reported to be effective in treating acute leukemia, and induce apoptosis in many tumor cells. In this study, the ability of a novel arsenical compound, As(4)O(6) (tetraarsenic oxide), along with As(2)O(3), for its ability to induce cell growth inhibition, as well as apoptosis, in human cervical cancer cells, SiHa cells, were evaluated in vitro. MATERIALS AND METHODS: To examine the levels of apoptosis, SiHa cells were given two sensitive doses, 0.5 and 1 microM, of arsenical compounds, and a DNA fragmentation assay and FACS analysis were then conducted. In addition, a Western blotting assay was performed to identify target molecules for apoptosis. RESULTS: Both As(2)O(3) and As(4)O(6) induced dosedependent inhibition of SiHa cell proliferation. In particular, As(4)O(6) was more effective at suppressing SiHa cell growth than As(2)O(3). In parallel with the inhibition of cell proliferation, As(4)O(6) caused a significantly greater increase in the sub-G1 cell population than As(2)O(3), as determined by propidium iodide DNA staining. This was confirmed by a DNA fragmentation assay and annexin V staining. The Western blotting analysis also showed that the expression of proliferating cell nuclear antigen (PCNA) was suppressed to a significantly greater extent by As(4)O(6) than As(2)O(3) at a dose of 0.5 microM. However, the apoptosis-related protein, Bax, was expressed to a significantly greater extent due to As(4)O(6) than As(2)O(3). CONCLUSION: Taken together, these findings suggest that a novel arsenic compound, As(4)O(6), possesses more potent anti-proliferative effects on human cervical cancer cells, with the induction of apoptosis also, at least via the activation of Bax protein in vitro.