Figure 4

MIF augments the proliferation rate of breast cancer cells. (a) Proliferation of unstimulated breast epithelial and breast carcinoma cell lines. Proliferation was measured by BrdU assay and is represented as percent of the baseline proliferation rate of MCF-12A. Proliferation rates of MDA-MB-231 and -468 are markedly and significantly (p values indicated) higher than that of MCF-12A. (b) Exogenous rMIF slightly but significantly enhances the proliferation rate of normal breast epithelial and breast carcinoma cell lines. As in (a) except that rMIF at indicated concentrations was added to cells for 24 h. Control cells (0 ng/ml) received control buffer (final dialysis refolding buffer). Asterisks indicate statistically significant differences compared to the corresponding control incubations: *, p < 0.05; **, p < 0.01. (c) Endogenous MIF supports proliferation of breast cancer cells by an autocrine loop and inhibition of proliferation by anti-MIF and anti-CD74 antibodies. Unstimulated proliferation of breast cancer cells as in (a) was compared to that of MCF-12A in the presence versus absence of neutralising anti-MIF and anti-CD74 antibodies. Control cells were incubated with equivalent amounts of PBS and isotype IgG had no effect (data not shown). Statistically significant differences (in comparison to cells not treated with antibody) are indicated by asterisks: *, p < 0.05; **, p < 0.01. Proliferation rates are means ± SD of two (b) or three (a, c) independent experiments with two (a) or three (b, c) determinations.