Antitumoral Activity of Indole-3-carbinol Cyclic tri- and Tetrameric Derivatives Mixture in Human Breast Cancer Cells: In Vitro and In Vivo Studies

Indole-3-carbinol (I3C) and its oligomeric derivatives have been widely studied for their chemopreventive and chemotherapeutic properties. We have previously shown that the I3C cyclic tetrameric derivative CTet inhibits breast cancer cell proliferation in vitro and in xenotrasplanted tumor. Here we report the antitumoral activity of a mixture of tri- and tetrameric cyclic I3C derivatives (CTr/CTet) both in vitro (MCF-7 and MDA-MB-231 breast cancer cell lines) and in vivo in a tumor xenograft model. CTr/CTet mixture avoids the low solubility drawbacks of CTet, thus favouring its solubilization, and reducing purification process, time and costs. CTr/CTet mixture has been shown to inhibit breast cancer cell proliferation (IC50 = 1.3 and 1.6 μg/ml in MCF-7 and MDAMB- 231, respectively) inducing the G0/1 cell cycle phase accumulation. The main molecular events related to CTr/CTet activity are the overexpression of p21, p27 and GADD45A, nuclear translocation of FOXO3a, inhibition of Akt activity and downregulation of estrogen receptor. In vivo, the growth of xenotransplanted tumor has been inhibited and the pro-tumoral low molecular weight cyclin E downregulation has been detected. Our data indicate that CTr/CTet is a potential anticancer combination agent for both hormoneresponsive and triple-negative breast tumors.