Background
The inhibitory effect of arsenic trioxide (As
2
O
3
) on lung cancer has been reported in some preclinical studies. However, its effect on small cell lung cancer (SCLC) has been poorly explored. Calcineurin and its substrate, nuclear factor of activated T cells (NFAT), mediate the downstream signaling of VEGF, and is critical in the process endothelium activation and tumor metastasis. In this study, we aimed to evaluate whether As
2
O
3
had inhibitory effects on endothelial cells activation and the metastasis of SCLC, and to explore the possible mechanisms.
Material/Methods
In vitro
, human umbilical vein endothelial cells (HUVECs) were used. Cell Counting Kit-8 assay and cell migration assay were performed to determine the effect of As
2
O
3
on HUVECs proliferation and migration. The level of calcineurin, NFAT, downstream factors for Down syndrome candidate region 1 (DSCR1), and the endogenous inhibitor of calcineurin, were evaluated by quantitative PCR and western blotting.
In vivo
, SCLC metastasis models were established by injecting NCI-H446 cells into tail veins of nude mice. Tumor-bearing mice were treated with As
2
O
3
or calcineurin inhibitor for 10 days, after which tumor metastasis in target organs was evaluated.
Results
As
2
O
3
significantly inhibited the proliferation and migration of endothelial cells. Also, As
2
O
3
inhibited the expression levels of calcineurin, NFAT, and the downstream target genes CXCR7 and RND1, while it upregulated the level of DSCR1. Both As
2
O
3
and calcineurin inhibitor exhibited notable inhibitory effect on the metastasis of SCLC, without obvious side effects.
Conclusions
These findings suggested that As
2
O
3
had remarkable inhibitory effects on the endothelial cell activation and SCLC metastasis, and the mechanism might be related to the blocking of calcineurin-NFAT signaling by upregulating DSCR1.