Breast cancer is the most prevalent cancer in women and an important cause of both morbidity and mortality. Although long-term disease-free survival is offered to women with early stage disease by current treatment modality, some, 30-40% of patients will have metastatic disease. Treatment of patients with metastatic disease is a great challenge for oncologists. Therefore, new drugs and therapeutic options for women with metastatic breast cancer are urgently required. Arsenical compounds have cytotoxic effects on several cancer cell lines including promyelocytic leukemia, esophageal carcinoma, megakaryocytic leukemia, and malignant lymphocytic cell lines. In addition, recent studies showed that arsenic trioxide (As2O3) can induce a clinical remission in patients with acute promyelocytic leukemia. In this study, we evaluated the cytotoxic effects of arsenic trioxide (As2O3) alone and combined with Taxane compounds (paclitaxel and docetaxel) on human breast carcinoma cell line MCF-7. It is clearly demonstrated that As2O3 has a significant cytotoxic effect on breast carcinoma cells. IC50 for As2O3 was 5 x 10-6 M after 72 h. Apoptosis of carcinoma cells was responsible for the cytotoxicity of As2O3. The additive effects of taxane compounds with As2O3 were shown. These in vitro results may suggest that As2O3 is a potential new cytotoxic agent for the treatment of breast cancer.

Breast cancer is the most prevalent cancer in women and an important cause of both morbidity and mortality. Although long-term disease-free survival is offered to women with early stage disease by current treatment modality, some, 30-40% of patients will have metastatic disease. Treatment of patients with metastatic disease is a great challenge for oncologists. Therefore, new drugs and therapeutic options for women with metastatic breast cancer are urgently required. Arsenical compounds have cytotoxic effects on several cancer cell lines including promyelocytic leukemia, esophageal carcinoma, megakaryocytic leukemia, and malignant lymphocytic cell lines. In addition, recent studies showed that arsenic trioxide (As2O3) can induce a clinical remission in patients with acute promyelocytic leukemia. In this study, we evaluated the cytotoxic effects of arsenic trioxide (As2O3) alone and combined with Taxane compounds (paclitaxel and docetaxel) on human breast carcinoma cell line MCF-7. It is clearly demonstrated that As2O3 has a significant cytotoxic effect on breast carcinoma cells. IC50 for As2O3 was 5 x 10-6 M after 72 h. Apoptosis of carcinoma cells was responsible for the cytotoxicity of As2O3. The additive effects of taxane compounds with As2O3 were shown. These in vitro results may suggest that As2O3 is a potential new cytotoxic agent for the treatment of breast cancer.