Panoply™ Human DRD2 Over-expressing Stable Cell Line

Non-small cell lung cancer (NSCLC) is one of the most lethal cancers worldwide. Dopamine receptor D2 (DRD2) plays multiple roles in the clinical progression of NSCLC and the maintenance of cancer cell function. However, the molecular mechanisms underlying this role are poorly understood. Here, researchers elucidated whether DRD2 inhibits lung cancer progression and identified potential downstream signaling pathways. They found that DRD2 inhibits tumor cell growth. DRD2 expression in NSCLC tissues was lower than in adjacent normal lung tissue. Furthermore, DRD2 mRNA and protein levels in NSCLC were inversely correlated with tumor size, TNM status, and overall patient survival. In vitro experiments demonstrated that disruption of DRD2 promoted the proliferation of NSCLC cell lines A549 and SK-MES-1 by inhibiting the NF-κB signaling pathway. Furthermore, DRD2 overexpression not only blocked lipopolysaccharide-induced proliferation and growth of A549 and SK-MES-1 cells but also suppressed tumor formation in mouse xenograft models. These results suggest that DRD2 may represent a potential therapeutic target for patients with lung cancers in which DRD2 is overexpressed by inhibiting the NF-κB signaling pathway.

DRD2 has been reported to downregulate cAMP levels, which are required for PKA to phosphorylate p65. To elucidate the role of cAMP in regulating NF-κB signaling, researchers used knockdown and overexpression strategies and found that cellular cAMP levels were reduced by 29.7% and 17.2% in DRD2-overexpressing A549 and SK-MES-1 cells, respectively (Figure 1A). Conversely, cAMP levels were significantly elevated in DRD2-knockdown NSCLC tumor cells (Figure 1A). Furthermore, IP assays for the interaction between DRD2 and PKA demonstrated that this interaction was blocked in DRD2-overexpressing NSCLC cells (Figure 1B, top panel). Densitometric analysis showed that DRD2 reduces 30.2% and 71.3% interaction with PKA in A549 and SK-MES-1 cells. Furthermore, when DRD2 inhibited cAMP levels and the interaction between PKA and p65, p65 distribution in the NSCLC cell nuclei was reduced (Figure 1C). The ability of p65 to bind to the TNF-α promoter was reduced in A549/D2 (P = 0.002) and SK-MES-1/D2 cells (Figure 1D). Therefore, DRD2 inhibits the growth of NSCLC tumor cells by blocking the NF-κB signaling pathway through regulating the cAMP/PKA/p65 axis.

Figure 1. DRD2 abrogates the cAMP/PKA/p65 axis. (Wu X Y, et al., 2018)