Figure 1.

Discontinuation of sunitinib promotes TNBC tumor regrowth and invasion. (A) Effects of sunitinib on the tumor volume of TNBC and non-TNBC cells. There wa sno significant difference in tumor volume when the treatment started. After mice were treated with sunitinib for one week, both the TNBC MDA-MB-231 tumors and the non-TNBC MCF-7 tumors in the treatment groups were smaller than those in the control groups. The sunitinib-treated TNBC MDA-MB-231 tumors regrew after treatment discontinuation, while the discontinuation had no significant effect on the tumor volume of the non-TNBC MCF-7 tumors. (B) H&E staining indicated that the TNBC MDA-MB-231 tumor cells invaded into adipose tissue (arrows) and skeletal muscle tissue (arrow heads) after treatment discontinuation. There was no aggressive behavior in the non-TNBC MCF-7 tumors. (C) IHC for MMP2 staining shows that TNBC MDA-MB-231 tumors after treatment was stopped expressed a higher level of MMP2 than tumors during the sunitinib treatment. There was nodifferenceinMMP2 expression in the non-TNBC MCF-7 tumors between the sunitinib treatment and after sunitinib was discontinued. (D) Quantification of MMP2 expression in the different groups. The scale bar represents 100 μm, and the error bar indicates the standard deviation (SD). *P < 0.05, ** P < 0.01, *** P < 0.001.