Panoply™ Human APLNR Knockdown Stable Cell Line

The apoxicam receptor (APLNR) is a GPCR involved in various pathophysiological processes, yet the relevance of APLNR expression in nasopharyngeal carcinoma (NPC) remains unclear. Here, researchers found that APLNR expression was reduced in NPC tissue compared with noncancerous NPC epithelial tissue. Furthermore, positive APLNR expression in NPC was associated with a better prognosis. Ingenuity pathway analysis revealed an indirect interaction between APLNR and retinoic acid (RA) within the cancer regulatory network. Following treatment with all-trans retinoic acid (ATRA), APLNR was significantly upregulated in NPC cell lines (5-8F and HNE1), inhibiting NPC cell proliferation and cell cycle arrest at the G0/G1 phase. Conversely, knockdown of APLNR attenuated ATRA-induced growth inhibition in NPC cells. Furthermore, researchers found that APLNR plays an important role in NPC cell migration and invasion. Overexpression of APLNR reduced the migration and invasion capabilities of two NPC cell lines. Further studies showed that low APLNR expression can promote EMT of NPC cells by activating the PI3K-protein kinase B-mammalian target of rapamycin signaling pathway. These data suggest that APLNR may predict the prognosis of NPC patients and inhibit the proliferation, migration, invasion and EMT of NPC cells.

Here, researchers used APLNR knockdown 5-8F and HNE-1 cells to investigate whether APLNR plays a significant role in ATRA-induced proliferation inhibition by regulating the cell cycle (Figure 1A, B). Flow cytometry results showed that knockdown of APLNR expression in NPC cells abolished the ATRA-induced cell cycle arrest. Furthermore, even with ATRA treatment, the proportion of cells in the G0/G1 phase did not increase further (Figure 1C, D). Next, Western blot analysis was used to verify changes in cell cycle-related proteins. Compared with control cells, APLNR knockdown 5-8F and HNE-1 cells showed decreased expression of APLNR and p16. However, cyclinD1 expression was increased compared with control cells. Subsequent treatment of control and APLNR knockdown NPC cells with ATRA revealed a slight increase in APLNR and p16 expression, while APLNR and p16 expression in APLNR knockdown cells remained decreased compared with controls. CyclinD1 expression was also increased (Figure 1E). These results indicate that APLNR plays an important role in ATRA blocking cell cycle progression in NPC cells.

Figure 1. APLNR was involved in ATRA-induced cell cycle arrest. (Liu Y, et al., 2019)