Figure 13. Effect of various pre-treatments on the efficacy of the DAV triple combination. Briefly, MCF7 cells, grown as monolayer cultures, were first pre-treated with either Vitamin C alone (250 μM), or Doxycycline Plus Azithromycin (D + A; 1 μM each), for a period of 7 days. Then, MCF7 cells were harvested with trypsin and re-plated under anchorage-independent growth conditions, in the presence of various combinations of Vitamin C, Doxycycline and Azithromycin. Note that 7 days of pre-treatment with either Vitamin C alone or Doxycycline Plus Azithromycin (D + A), rendered the DAV triple combination significantly less effective. Therefore, to achieve maximal impact, we conclude that all three components of the DAV combination of Doxycycline (1 μM), Azithromycin (1 μM) and Vitamin C (250 μM), should be administered together at the same time. MFE, mammosphere formation.