Fig. 2.

Low ATIP3 levels are associated with sensitivity to taxanes in patient-derived xenografts and breast cancer MCSs. (A, Left) Immunohistochemistry performed on human breast cancer xenograft sections of a tissue microrarray using anti-MTUS1 monoclonal antibody. Shown are representative photographs of tumors expressing low (Left) or high (Right) levels of ATIP3. (Scale bar, 500 µm.) Close-ups are shown in the bottom. (Scale bar, 50 µm.) (A, Right) Correlation between ATIP3a mRNA expression level (by qPCR) and IHC score. (B) Scattered dot plot of ATIP3 (qPCR) mRNA expression level in HBCx treated with DTX (Left) or with (Right). Tumors are classified according to their response to drug treatment. R indicates resistance, and S indicates sensitivity. Numbers of samples are in brackets. *P < 0.05. (C) Percentage of responsive HBCx according to ATIP3 level. Tumors were subdivided into groups expressing high ATIP3 versus low ATIP3 levels based on the median value of ATIP3 measured by real-time RT-PCR. *P < 0.05. (D) Dose–response curves of SUM52PE spheroids (MCSs) expressing (shCtrl) or not expressing (shATIP3) ATIP3 and treated with increasing concentrations of PTX. (E) SUM52PE MCSs as in D were treated for 6 d with 50 nM PTX or 100 nM doxorubicin (DOXO) and photographed. The picture represents one MCS of the quadruplicate. Measures of spheroid area are plotted in the histogram on the Right. ****P < 0.0001. (F) Representative photographs of SUM52PE MCSs as in D treated with 50 nM of PTX for 72 h prior to staining with TUNEL reagent (green) and DAPI (blue). Quantification of apoptosis, measured as percent of TUNEL-positive cells, is shown on the Right. (Magnification, 20×.) (Scale bar, 100 µm.) **P < 0.01. (G) Western blot analysis of PARP cleavage in SUM52PE MCSs as in D treated for 72 h with increasing concentrations of PTX. Vinculin (Vinc) is used as the internal loading control. Quantification is shown below.