Arsenic trioxide induces cell cycle arrest and affects Trk receptor expression in human neuroblastoma SK-N-SH cells

BACKGROUND: Arsenic trioxide (As(2)O(3)), a drug that has been used in China for approximately two thousand years, induces cell death in a variety of cancer cell types, including neuroblastoma (NB). The tyrosine kinase receptor (Trk) family comprises three members, namely TrkA, TrkB and TrkC. Various studies have confirmed that TrkA and TrkC expression is associated with a good prognosis in NB, while TrkB overexpression can lead to tumor cell growth and invasive metastasis. Previous studies have shown that As(2)O(3) can inhibit the growth and proliferation of a human NB cell line and can also affect the N-Myc mRNA expression. It remains unclear whether As(2)O(3) regulates Trks for the purposes of treating NB. METHODS: The aim of the present study was to investigate the effect of As(2)O(3) on Trk expression in NB cell lines and its potential therapeutic efficacy. SK-N-SH cells were grown with increasing doses of As(2)O(3) at different time points. We cultured SK-N-SH cells, which were treated with increasing doses of As(2)O(3) at different time points. Trk expression in the NB samples was quantified by immunohistochemistry, and the cell cycle was analyzed by flow cytometry. TrkA, TrkB and TrkC mRNA expression was evaluated by real-time PCR analysis. RESULTS: Immunohistochemical and real-time PCR analyses indicated that TrkA and TrkC were over-expressed in NB, and specifically during stages 1, 2 and 4S of the disease progression. TrkB expression was increased in stage 3 and 4 NB. As(2)O(3) significantly arrested SK-N-SH cells in the G2/M phase. In addition, TrkA, TrkB and TrkC expression levels were significantly upregulated by higher concentrations of As(2)O(3) treatment, notably in the 48-h treatment period. Our findings suggested that to achieve the maximum effect and appropriate regulation of Trk expression in NB stages 1, 2 and 4S, As(2)O(3) treatment should be at relatively higher concentrations for longer delivery times;however, for NB stages 3 and 4, an appropriate concentration and infusion time for As(2)O(3) must be carefully determined. CONCLUSION: The present findings suggested that As(2)O(3) induced Trk expression in SK-N-SH cells to varying degrees and may be a promising adjuvant to current treatments for NB due to its apoptotic effects.