Fig. 5

Prosaposin (PSAP) increases cell motility and invasiveness of letrozole-resistant (LetR) breast cancer cells with negligible impact on the function of endocrine-sensitive cells. a (i) In vitro scratch assays were used to evaluate the impact of recombinant human PSAP (rhPSAP) on cell migration. Cell migration was significantly enhanced in LetR cells exposed to increasing doses of rhPSAP with maximal impact observed with 10 ng/ml PSAP treatment (p <0.0001) (ii), conversely, there were no changes in cell migration observed in MCF7 cells (not significant (n.s.). Error bars are representative of mean ± standard error of the mean (SEM) of three separate experiments. b (i-ii) Using matrigel invasion chambers it was determined that the invasive potential of LetR cells was greatly amplified when cells were cultured in the presence of rhPSAP (10 ng/ml) (40 hours) compared to their endocrine-sensitive counterparts, MCF7 which were unresponsive to treatment (iii-iv). b (v) Bar-chart representing data from rhPSAP invasion assay in LetR and MCF7. Error bars are representative of mean ± SEM of three separate experiments. c Transfection of LetR cells with siRNA-HOXC11 significantly inhibits cell migration (i-ii), furthermore, treatment of cells with rhPSAP (10 ng/ml) (60 hours) does not stimulate cell invasion when HOXC11 is knocked down (iii-iv). c (v) Data from rhPSAP invasion assay in LetR +/− rhPSAP. Error bars are representative of mean ± SEM from four separate experiments: *p <0.05, **p <0.001, ***p <0.0001. Scram veh scrambled vehicle