A new study has reported that 3,3'-diindolylmethane (DIM) enhances the therapeutic efficacy of the chemotherapy drug Taxotere (docetaxel) in breast cancer cells. The study was designed to investigate the effect of DIM alone and in combination with Taxotere on the growth of various breast cancer cell lines. There is growing evidence that elevated expression of the transcription factor Forkhead Box M1 (FoxM1) is associated with some aggressive cancers, including breast cancer. DIM is a compound that has been found to have chemopreventive effects in various tumors. The inhibition of FoXM1 sensitizes breast cancer cells to conventional chemotherapy. Hence the authors decided to investigated the effect of DIM alone and in combination with Taxotere on the expression of FoXM1.

Using a variety of investigative methods, the authors demonstrated that DIM enhanced Taxotere-induced apoptosis (i.e., it activated internal cell programs for cell suicide) in breast cancer cells. These cell death-enhancing effects were found to be associated with down-regulation of FoxM1. DIM also inhibited breast cancer cell growth and reduced migration and invasion of the cells. Combined treatment with DIM and Taxotere significantly inhibited tumor growth, and the degree of inhibition was related to the level of down-regulation of FoXM1. The authors conclude that DIM enhances the therapeutic efficacy of Taxotere in breast cancer cells by inactivating FoxM1 and its target genes, making it a possible candidate for treatment and/or prevention of aggressive breast cancer.

Foods sources of DIM

DIM is a metabolic product of indole-3-carbinol (I3C), which is found in cruciferous (or brassica) vegetables. Although both DIM and I3C are available in supplement form, we do not recommend taking these supplements. Foods such as broccoli, bok choy and collard greens that contain I3C also contain other chemopreventive compounds such as sulforaphane. Also, the anticancer properties of such vegetables are likely to be the result of synergistic interaction of their various chemical components - isolated components have successfully inhibited proliferation in the laboratory, but their efficacy and safety in humans needs to be evaluated in large scale clinical trials. There is some evidence that high levels of concentrated cruciferous vegetable extracts can increase aromatase activity (in which androgens are converted to estrogens in the body), thereby promoting breast cancer cell proliferation. Levels of DIM adequate for breast cancer chemoprevention can readily be obtained by eating cruciferous vegetables and condiments made from them:

Arugula
Bok choy
Broccoli
Brussels sprouts
Cabbage
Cauliflower
Collard greens
Horseradish
Kale
Kohlrabi
Mustard
Mustard greens
Radish
Rutabaga
Sauerkraut
Turnips
Wasabi
Watercress

Please see our article on what to eat during Taxol chemotherapy for more information on how to optimize treatment with a taxane.