Figure 4C shows again that exosomes from PTX-treated cells are far better at preventing the death of serum-starved NIH-3T3 fibroblasts compared to exosomes from DMSO-treated control cells (compare bars 1 and 2). However, this benefit was lost when Survivin expression was depleted from these exosomes by siRNA (compare bars 2 and 4). Similar results were obtained when the same cell survival experiment was performed using the less aggressive SKBR3 breast cancer cell line as the recipient cells (Figure 4D). This evidence concerns the gene BIRC5 and breast cancer.