The aim of the study was to detect PPA1 expression in various tumors and to investigate the relationship between PPA1 expression and clinicopathological parameters to further analyze its clinical significance. Immunohistochemical staining detected PPA1 expression in 305 noncancerous tissues and 675 tumor tissues, which included 12 different tumor types. QPCR and western blot examined PPA1 expression in tumor‐derived cell lines including those derived from liver, breast, lung, and ovarian cancers. Cell proliferation and apoptosis assays were used to investigate PPA1‐regulated cell growth in tumor cells. Finally, a bioinformatics analysis was used to verify the role of PPA1 in carcinogenesis. Among the 12 types of tumors, PPA1 expression was significantly higher in lung and ovarian cancers (P < 0.001). In lung cancer, PPA1 expression was associated with tumor size, patients’ age, and smoking status, whereas in ovarian cancer, PPA1 expression was associated with pathological grade (P < 0.05). Moreover, we found that PPA1 expression was up‐regulated in lung and ovarian cancer cell lines compared with nontumor cells. In addition, suppression of PPA1 expression by RNA interference in lung and ovarian cancer cells showed increased cell apoptosis and decreased cell proliferation, which was mediated by TP53 and p21 signaling. Notably, a bioinformatics analysis was used to verify the function of PPA1 in the development and progression of tumors. PPA1 expression is significantly higher in many tumors, especially those of lung and ovarian origin, which suggests that PPA1 plays an important role in carcinogenesis and in the development of some tumors.

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Inorganic pyrophosphatase (PPA1) promotes tumor progression in several tumor types. However, the underlying mechanism remains elusive. Here, we disclosed that PPA1 expression is markedly upregulated in lung carcinoma tissue versus normal lung tissue. We also found that the non-small cell lung cancer (NSCLC) cell lines show increased PPA1 expression levels versus normal lung cell line control. Moreover, the knockdown of PPA1 promotes cell apoptosis and inhibits cell proliferation. Whereas, the ectopic expression of PPA1 reduces cell apoptosis and enhances cell proliferation. Most interestingly, the expression of mutant PPA1 (D117A) significantly abolishes PPA1-mediated effect on cell apoptosis and proliferation. The underlying mechanism demonstrated that TP53 expression deficiency or JNK inhibitor treatment could abolish PPA1-mediated NSCLC progression. In summary, the aforementioned findings in this study suggest a new pathway the PPA1 mediates NSCLC progression either via TP53 or JNK. Most important, the pyrophosphatase activity is indispensible for PPA1-mediated NSCLC progression. This may provide a promising target for NSCLC therapy.

Arsenic trioxide (AsO) induces cell apoptosis and reduces the invasive and metastatic activities in various cancer types. However, the role of AsO in ovarian cancer angiogenesis remains unclear. In this study, we investigated the role of AsO in ovarian cancer angiogenesis and found that a low concentration of AsO causes no effects on epithelial ovarian cancer cell viability or apoptosis. Moreover, we found that AsO-treated epithelial ovarian cancer cells demonstrate a reduced tube formation of endothelial cells in Matrigel. In addition, AsO-treated epithelial ovarian cancer cells show a decreased VEGFA, VEGFR2 and CD31 mRNA expression. As per the underlying mechanisms involved in AsO treatment, we found that AsO inhibits VEGFA and VEGFR2 expression that thereby inhibits the VEGFA-VEGFR2-PI3K/ERK signaling pathway. This leads to a suppression in both VEGFA synthesis and angiogenesis-related gene expression. A decreased VEGFA synthesis and secretion also inhibits the VEGFA-VEGFR2-PI3K/ERK signaling pathway in human umbilical vein endothelial cells (HUVECs). In summary, our results may provide strategies for the use of AsO in the prevention of tumor angiogenesis.