Combination of arsenic trioxide and apatinib synergistically inhibits small cell lung cancer by down-regulating VEGFR2/mTOR and Akt/c-Myc signaling pathway via GRB10.

Background: Small cell lung carcinoma (SCLC) is characterized by -poor prognosis, -high predilection for -metastasis, -proliferation, and -absence of newer therapeutic options. Elucidation of newer pathways characterizing the disease may allow for development of targeted therapies and consequently favorable outcomes.

Methods: The current study explored the combinatorial action of arsenic trioxide (ATO) and apatinib (APA) in vitro and in vivo. In vitro models were tested using -H446 and -H196 SCLC cell lines. The ability of drugs to reduce -metastasis, -cell proliferation, and -migration were assessed. Using bioinformatic analysis, differentially expressed genes were determined. Gene regulation was assessed using gene knock down models and confirmed using Western blots. The in vivo models were used to confirm the resolution of pathognomic features in the presence of the drugs. Growth factor receptor bound protein (GRB) 10 expression levels of human small cell lung cancer tissues and adjacent tissues were detected by IHC.

Results: In combination, ATO and APA were found to significantly reduce -cell proliferation, -migration, and -metastasis in both the cell lines. Cell proliferation was found to be inhibited by activation of Caspase-3, -7 pathway. In the presence of drugs, it was found that expression of GRB10 was stabilized. The silencing of GRB10 was found to negatively regulate the VEGFR2/Akt/mTOR and Akt/GSK-3β/c-Myc signaling pathway. Concurrently, absence of metastasis and reduction of tumor volume were confirmed in vivo. The immunohistochemical results confirmed that the expression level of GRB10 in adjacent tissues was significantly higher than that in human small cell lung cancer tissues.

Conclusions: Synergistically, ATO and APA have a more significant impact on inhibiting cell proliferation than each drug independently. ATO and APA may be mediating its action through the stabilization of GRB10 thus acting as a tumor suppressor. We thus, preliminarily report the impact of GRB10 stability as a target for SCLC treatment.