Selenite is frequently used in combination with
cancer chemotherapeutic agents to reduce side effects. However, the cytoprotective activity of
selenite may also reduce the efficacy of chemotherapeutic drugs on
tumor cells. This study was designed to examine the effects of
selenite combined with
cytotoxic agents used in clinical protocols [e.g., doxorubicine,
docetaxel,
5-fluorouracil (5-FU),
methotrexate (MTX), mafosphamide,
mitomycin C,
gemcitabine,
etoposide,
cisplatin,
irinotecan, and
oxaliplatin] on the proliferation of various
carcinoma cell types. The data demonstrated that
selenite had no marked effects on the antiproliferative activity of
docetaxel, doxorubicine,
5-FU, MTX, and mafosphamide in MDA-MB-231
breast cancer cells. Likewise, no consistent changes were observed in A549
lung cancer cell proliferation when
selenite was combined with
cisplatin,
etoposide,
gemcitabine, or
mitomycin C. On the other hand,
selenite potentiated the cytotoxicity of
5-FU,
oxaliplatin, and
irinotecan in HCT116
colon cancer cells by approx 1.1-fold, 2.7-fold, and 2.6-fold, respectively. In SW620
colon cancer cells,
selenite induced a 1.5-fold and 4.3-fold increase of the antiproliferative activity of
5-FU and
oxaliplatin, respectively. Whereas
irinotecan showed no effects on SW620 cell growth, a combination with
selenite resulted in 23% inhibition. Our results indicate that
selenite did not reduce the antiproliferative activity of chemotherapeutic agents in vitro. In addition,
selenite was able to increase the inhibitory activity of
docetaxel in A549
lung cancer cells, and of
5-FU,
oxaliplatin, and
irinotecan in HCT116 and SW620
colon cancer cells implying
selenite is potentially useful as an adjuvant chemotherapeutic agent.