Fig. 2.

Dox upregulated the expression of PTN and its receptor PTPRZ1 in breast cancer cells. a, b RT-PCR analyses of the expression of PTN and PTPRZ1 in the MCF-7/ADR, MCF-7, MDA-MB-231, HCC-1937, and MDA-MB-453 cell lines. The data are shown as the mean ± s.e.m., n = 5, **p < 0.01, Student’s t-test. Immunoblot analyses of the expression of PTN and PTPRZ1 in MDA-MB-231 cells treated with different concentrations of Dox (c), rhPTN (d), scrambled siRNA (siCtrl) or empty vector plasmid (vector) (e), and PTPRZ1 knockdown (siRNA) or overexpression (PTPRZ1) were performed. (f). The representative blots are shown in the upper panel, and the summary densitometry measurements are shown in the lower panel. Data are shown as the mean ± s.e.m., n = 5, *p < 0.05, ***p < 0.001, Student’s t-test. g The chemotherapy-driven increases in PTN and PTPRZ1 expression levels create a positive feedback loop. h Immunofluorescent staining for PTPRZ1 (in red) in MDA-MB-231 cells treated with Dox, rhPTN or Dox + rhPTN is shown