Additional file 4 of Histamine N-methyltransferase (HNMT) as a potential auxiliary biomarker for predicting adaptability to anti-HER2 drug treatment in breast cancer patients

Additional file 4: Fig. S4 HNMT expression affected the binding affinity of TNBC tumor cells for trastuzumab. (A) Western blot analysis of HNMT and HER2 protein expression in SKBR3 cells transfected with the vector or with the HNMT siRNA alone, the HER2 siRNA alone, or the combined HNMT/HER2 siRNA. (B) Schematic diagram of the timeline for DOX (5 μg/mL)-induced HNMT expression via the T-RExTM system (pcDNA5/TO-HNMT and pcDNA6/TR vectors) at time-dependent manner (0, 24, and 48 h). (C-D) Western blotting (C) and flow cytometric analysis (D) are shown. (E) Western blotting confirmed the protein expression of HNMT and HER2 in TNBC cells harboring the vector or overexpressing HNMT. (F) In the above cells (E), flow cytometry was used to detect the binding affinity of trastuzumab (0.1, 0.5, 1 μg/mL) for the HER2 protein. n = 3 biologically independent experiments. The data are presented as the means ± SEs. Statistical analysis was performed using a two-tailed unpaired Student's t-test. *P < 0.05, **P < 0.01, and ***P < 0.001.