Arsenic disulfide‑induced apoptosis and its potential mechanism in two‑ and three‑dimensionally cultured human breast cancer MCF‑7 cells.

In China, arsenic disulfide (As2S2) has been used for the treatment of hematological malignancies. The present study aimed to evaluate the effects of As2S2 on the human breast cancer MCF‑7 cell line cultured in both two‑dimensional (2D) monolayers and three‑dimensional (3D) spheroids to explore its therapeutic potential in breast cancer treatment. Cellular viability and the induction of apoptosis were examined with a cell counting kit‑8 (CCK‑8) assay and flow cytometric analysis, respectively. Alterations in the expression levels of apoptosis‑associated proteins, including Bcl‑2‑associated X protein (Bax), B‑cell lymphoma 2 (Bcl‑2), p53, and caspase‑7, as well as the cell survival‑associated proteins, phosphatidylinositol 3‑kinase (PI3K), Akt, and mammalian target of rapamycin (mTOR), were assessed by western blotting. Although a dose‑dependent reduction in cell viability, which occurred in association with the induction of apoptosis triggered by the addition of 2‑24 µM As2S2, was observed in both 2D‑ and 3D‑culture systems, 3D spheroids were less sensitive to the cytotoxic effect of As2S2 compared with the 2D cultured cells. A significant increase in the expression levels of Bax, p53, and caspase‑7 was observed in treated 2D‑cultured cells, whereas a similar increase in the expression levels of Bax was only confirmed in treated 3D spheroids, although there was a trend towards the increased expression of p53 and caspase‑7 in the 3D spheroids. These results suggested that these molecules are closely associated with As2S2‑mediated cytotoxicity in the two culture systems, and further suggested that the difference in the sensitivity to As2S2 between 2D monolayers and 3D spheroids may be attributed to the differential alterations in the expression levels of proteins associated with cell mortality. Significant downregulation of the expression levels of Bcl‑2, PI3K, Akt and mTOR was observed in the two culture systems. Taken together, the results of the present study demonstrated that As2S2 inhibits cell viability and induces apoptosis in both 2D‑ and 3D‑ cultured MCF‑7 cells, which may be associated with activation of the pro‑apoptotic pathway and the inhibition of pro‑survival signaling. These results have provided novel insights into clinical applications of As2S2 in the treatment of patients with breast cancer.