Aberrant
fibroblast growth factor (FGF) and
FGF receptor (FGFR) system have been associated with
breast cancer. The objectives of our study were to investigate the effects and mechanisms of FGFR inhibition on
tumor growth and
metastasis on
breast cancer. Our studies showed that the FGFR inhibitor
PD173074 decreased the viability of several human
breast cancer cells, as well as 4T1 murine mammary
tumor cells. Therefore, we chose 4T1 cells to study
PD173074's antitumor mechanism. Flow cytometry showed that
PD173074 induced 4T1 cell apoptosis in a concentration-dependent manner. Western blot demonstrated that PD173074-induced apoptosis was correlated with the inhibition of Mcl-1 and
survivin. Moreover,
PD173074 also significantly increased the ratio of Bax/Bcl-2.
PD173074 could also block 4T1 cell migration and invasion in vitro. In 4T1
tumor-bearing mice,
PD173074 significantly inhibited
tumor growth without obvious side effects. Meanwhile,
PD173074 functionally reduced microvessel density and proliferation index and induced
tumor apoptosis. Importantly, we found that FGFR inhibition by
PD173074 reduced myeloid-derived suppressor cells (MDSCs) in the blood, spleens and
tumors, accompanied by the increased infiltration of CD4(+) and CD8(+) T cells in the spleens and
tumors. Furthermore,
PD173074 significantly inhibited
breast tumor metastasis to the lung of inoculated 4T1
breast cancer cells, which was accompanied by a reduction in MDSCs. Our findings suggested that FGFR inhibition could delay
breast tumor progression, impair lung
metastasis and break immunosuppression by effecting on tumor microenvironment, which may provide a promising therapeutic approach for
breast cancer patient.