Apatinib exerts anti-tumor activity to non-Hodgkin lymphoma by inhibition of the Ras pathway

Apatinib is a tyrosine kinase inhibitor that selectively targets vascular endothelial growth factor receptor-2 (VEGFR-2). Although apatinib has shown promising anti-tumor activity against several types of tumor, its role and underlying mechanism against non-Hodgkin lymphoma (NHL) remain to be explored. Here, we report that apatinib dramatically inhibited in vitro the proliferation of various human NHL cell lines, including Burkitt lymphoma (BL), mantle cell lymphoma (MCL), and diffuse large B-cell lymphoma (DLBCL), in a dose-dependent manner. Moreover, administration of apatinib markedly delayed tumor growth in vivo in a xenograft mouse model derived from human DLBCL OCI-ly3 cells, in association with significantly prolonged survival of tumor-bearing mice. Mechanistically, apatinib suppressed activation of VEGFR2 (manifested by reduced VEGFR2 phosphorylation), accompanied by inhibition of the Ras pathway (reflected by down-regulation Ras, Raf, pMEK1/2, pERK1/2) in OCI-ly1 (GCB subtype of DLBCL) and SU-DHL2 (ABC subtype of DLBCL) cells. Of note, apatinib sharply impaired angiogenesis in vivo in tumor tissues. Together, these results indicate that apatinib displays a marked cytotoxic activity against various types of NHL cells (including BL, MCL, and GCB- or ABC-DLBCL) both in vitro and in vivo. They also suggest that anti-NHL activity of apatinib might be associated with inhibition of tumor cell growth and induction of apoptosis as well as anti-angiogenesis by targeting VEGFR2 and its downstream Ras/Raf/MEK/ERK pathway.