Preclinical Studies of Chiauranib Inhibit Follicular Lymphoma through VEGFR2/ERK/STAT3 Signaling Pathway

Abstract

Follicular lymphoma (FL) is the most common indolent non-Hodgkin's lymphoma. In the vast majority of patients, FL is an incurable and transformative challenging disease. Recently, novel antibodies and new agents targeting carcinogenic pathways, such as B-cell receptor signaling or inhibition of Bcl-2, have generated highly attractive therapeutic options. But the disease still cannot be cured by conventional methods. Therefore, the development of new and more powerful drugs targeting different pathways in disease pathogenesis is critical for improving patient outcomes. Chiauranib (CS2164) is a novel inhibitor that targets the tumor microenvironment and mainly exerts anti-tumor effects by inhibiting pathways such as VEGFR2, Aurora B, and CSF1R. Previous studies have shown that it has a lethal effect on a variety of solid tumors and the results of Phase I clinical trials show good tolerance and small toxic side effects (Yongkun Sun, 2019), while the application of Chiauranib in FL has not been reported. In this study, we treated FL cell lines containing DOHH2, RL, SU-DHL-4, and Karpas422 cells with different concentrations of Chiauranib, and the cell proliferation was gradually reduced along with the increase of concentration by 5-ethynyl-2'-deoxyuridine (EDU) staining and CCK-8 assay. Besides, apoptosis was also found to increase under the chiauranib treatment conditions and the cell cycle was shown arrested in the G2/M phase. Chiauranib was also determined to have a significant inhibitory effect on follicular lymphoma in vivo. Surprisingly, we revealed that angiogenesis was significantly reduced in tumors in the chiauranib group, which was validated by immunohistochemical staining of VEGFA. Consistently, we confirmed that cell migration was slowed by migration chamber assay and scratch assay. To investigate the expression level of STAT3, which plays an important role in the regulation of angiogenesis, we used immunofluorescence and western blotting and uncovered the phosphorylation level of STAT3 was significantly reduced, and related target genes downstream of STAT3 also changed. Finally, we found that the VEGFR2/ERK/STAT3 signaling pathway is closely related to an inhibitory effect of Chiauranib. In conclusion, by acting on VEGFR2, chiauranib is acting on the VEGFR2/ERK/STAT3 signaling pathway, thereby altering the expression level of STAT3 target genes, ultimately leading to decreased cell proliferation, increased apoptosis, slowed migration, and decreased angiogenesis. These findings provide a basis for further clinical exploration of chiauranib as a promising treatment for follicular lymphoma.