Plaque assay analysis using the NDV-infected MCF7 and MCF7-CR cell culture media. At 12, 24, 48 and 96 hours post-infection, 100 μl of the infected cell culture media were removed and subjected to the plaque assay as described in Methods section. The resulting plaques were calculated and a graph was plotted. Values are presented as means ± SD of triplicate experiments. *p < 0.05.