Recombinant fusion proteins FPTD-Grb2-SH2 and FPTD-Grb2-SH2M inhibit the proliferation of breast cancer cells in vitro.

Growth factor receptor bound protein 2 (Grb2) is a key adaptor performing a principal role in the oncogenic Ras signaling pathway. In the present study, we generated two fusion proteins. One contained an Src homology 2 (SH2) domain of Grb2, a signal peptide sequence, FLAG-tag sequence, PTD region and we named it FPTD-Grb2-SH2, while the other contained one mutant SH2 domain, added to a signal peptide sequence, FLAG-tag sequence, PTD region and we named it FPTD-Grb2-SH2M. Western blot analysis and immunofluorescence assay were used to investigate the expression and location of the fusion proteins in breast cancer cells. The proliferation and migration of the cells were estimated by MTT and Transwell cell migration assays, respectively. Flow cytometric analysis was performed to evaluate the apoptosis of the breast cancer cells. The recombinant proteins FPTD-Grb2-SH2 and FPTD-Grb2-SH2M were successfully expressed in the breast cancer cell lines regardless of HER2-phenotype, and they suppressed breast cancer cell growth and migration as expected from the lack of SH3 domain. Both FPTD-Grb2-SH2 and FPTD-Grb2-SH2M exhibited significant toxicity to breast cancer cells. The present study demonstrated that the recombinant proteins FPTD-Grb2-SH2 and FPTD-Grb2-SH2M may be used for anticancer drug development.