The most frequently used opioid in cancer pain management is morphine which remains a cornerstone for the management of cancer pain, due to the largest experience existing among physicians and widely availability in a variety of formulation. Considering that analgesics on cancer pain is often under the condition of chemotherapy and 5-Fluorouracil (5-FU) is widely used today as a potent drug for the treatment of advanced cancers, whether analgesics such as morphine, interferes the chemotherapy such as 5-FU, arose as a considerable problem.

In this study, the MCF-7 breast cancer cells were used to determine the antitumor effects of the 5-FU in combination with morphine. The cell proliferation was determined by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and the apoptosis was determined by the Annexin V/PI staining and flow cytometry. The immunocytochemistry and western blot was used to determine the Bcl-2 and Bax expression.

It was shown that in MCF-7 cells, the proliferation was inhibited, the apoptosis was promoted, the Bcl-2 expression was suppressed and the Bax expression was promoted by both 5-FU alone and morphine alone, while the superior effects were achieved in combination with the two drugs.

These results suggest that the morphine may have the beneficial effects on the antitumor chemotherapy with 5-FU, in stead of interferential effects.