We found that the 2nd xenograft tumor cells originating from the 1st EGFP+ MDA-MB-231 cells showed robust AKT S473 phosphorylation in response to serum stimulation, compared to the 2nd xenograft tumor cells originating from the 1st EGFP− cells (Additional file 6, panel A). This evidence concerns the gene AKT1 and neoplasm.