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

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.

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.

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).

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.