Vitamin D, tamoxifen and β-estradiol modulate breast cancer cell growth and interleukin-6 and metalloproteinase-2 production in three-dimensional co-cultures of tumor cell spheroids with endothelium

Reciprocal interactions between tumor cells and endothelial cells constitute the most important stage of tumor metastasis. There is growing evidence suggesting that beta-estradiol and vitamin D modulate the progression of steroid-sensitive breast cancers. In keeping with those results, the purpose of the study reported here was to determine the cytotoxic and antiproliferative activity of tamoxifen (TAM) in the T47D human breast cancer cell line depending on the cell culture model (three-dimensional (3D, spheroid) or two-dimensional (2D, monolayer)) and to estimate the antiproliferative activity of vitamin D in balanced TAM/beta-estradiol conditions. The study was also designed to investigate whether vitamin D might influence interleukin-6 (IL-6) and metalloproteinase-2 (MMP-2) production in a co-culture of T47D cell spheroids with an endothelial cell monolayer in the presence of beta-estradiol and TAM. Spectrophotometric analysis with MTT revealed that the cytotoxic and antiproliferative activity of TAM was dependent on the culture model, the density of cell culture, and culture medium supplements. In balanced TAM/beta-estradiol medium, vitamin D only slightly inhibited T47D cell proliferation in both 2D and 3D cultures. Direct contact of tumor cell spheroids with the endothelium induced production of MMP-2 and IL-6, which was significantly inhibited in TAM/beta-estradiol balanced medium. Addition of vitamin D further inhibited MMP-2 production, but enhanced the production of IL-6 as was shown by ELISA assay. Our co-culture model in TAM/beta-estradiol balanced medium proved to be useful for examining direct and paracrine interactions of tumor cells with the endothelium in conditions that were closer to in vivo conditions than in the standard 2D model.