Knockdown of NPAS2 Inhibits the Progression of Endometrial Cancer through ZHX3

Background & Purpose: Neuronal PAS domain protein 2 (NPAS2) is a biological rhythm gene involved in cancer progression. This study explored the function of NPAS2 on endometrial cancer (EC), as well as the potential mechanisms involving NPAS2-zinc fingers and homeoboxes-3 (ZHX3) axis. Methods: Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot were used to measure the level of NPAS2 and ZHX3 in EC cells. Cell proliferation was analyzed using 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) and colony formation assays. Flow cytometry was used to test cell cycle and apoptosis. The effect of NPAS2 on tumor growth was measured using a mouse xenograft model. The interaction between NPAS2 and ZHX3 was further confirmed by feedback experiments in vitro. Results: NPAS2 expression was higher in EC cell lines. Knockdown of NPAS2 repressed proliferation, induced gap (G1)/ synthesis (S) arrest, and promoted apoptosis in EC cells. NPAS2 knockdown also suppressed tumor growth. Furthermore, NPAS2 was significantly positively correlated with ZHX3. Overexpression of ZHX3 reverses the anti-tumor effects of NPAS2 silencing on EC cells. Conclusions: Lower expression of the NPAS2-ZHX3 axis could inhibit cell proliferation and induce apoptosis, thereby attenuating the development of EC.