Racial Differences in Stage IV Colorectal Cancer Molecular Profiling and Mutation Rates.

INTRODUCTION: Despite advances in colorectal cancer (CRC) treatment, racial disparities persist. The primary aims of the study were to: evaluate differences in molecular testing rates over time by race; and measure the incidence of tumor mutations by race in patients with metastatic CRC. METHODS: A retrospective cohort study was performed of all adult patients with stage IV CRC (2008-2018) identified within the cancer registry of a large regional health system. Demographic/clinical characteristics were collected through primary data abstraction of the electronic health record. Molecular profiling results were obtained directly from Caris Molecular Intelligence and electronic health record. RESULTS: Three hundred eighty-three patients were included: 40.5% (n = 155) were Black and 59.5% (n = 228) were White. Significant increases were observed in microsatellite instability (MSI), KRAS, and BRAF testing rates during the study period (P < 0.0001). The odds of testing over time increased more significantly in Black compared to White patients for MSI testing (White: odds ratio [OR] 1.26 [95% confidence interval [CI] 1.12-1.41], Black: OR 1.69 [95% CI 1.41-2.02], P = 0.005) and BRAF testing (White: OR 1.42 [95% CI 1.26-1.62], Black: OR 1.89 [95% CI 1.51-2.36], P = 0.027). An increase in KRAS testing over time was observed for both cohorts and was independent of race (P = 0.58). Mutation rates did not differ by race: KRAS (Black 55.8% versus White 45.6%, P = 0.13) and BRAF (Black 4.8% versus White 10.0%, P = 0.33). CONCLUSIONS: Within a large regional health system, molecular testing rates in patients with metastatic CRC increased significantly following National Comprehensive Cancer Network guideline changes for both Black and White patients. Black and White patients who underwent molecular testing had similar rates of MSI, KRAS, and BRAF mutations.

RGS2 modulates the activity and internalization of dopamine D2 receptors in neuroblastoma N2A cells.

Dysregulated expression and function of dopamine D2 receptors (D2Rs) are implicated in drug addiction, Parkinson's disease and schizophrenia. In the current study, we examined whether D2Rs are modulated by regulator of G protein signaling 2 (RGS2), a member of the RGS family that regulates G protein signaling via acceleration of GTPase activity. Using neuroblastoma 2a (N2A) cells, we found that RGS2 was immunoprecipitated by aluminum fluoride-activated Gαi2 proteins. RGS2 siRNA knockdown enhanced membrane [(35)S] GTPγS binding to activated Gαi/o proteins, augmented inhibition of cAMP accumulation and increased ERK phosphorylation in the presence of a D2/D3R agonist quinpirole when compared to scrambled siRNA treatment. These data suggest that RGS2 is a negative modulator of D2R-mediated Gαi/o signaling. Moreover, RGS2 knockdown slightly increased constitutive D2R internalization and markedly abolished quinpirole-induced D2R internalization assessed by immunocytochemistry. RGS2 knockdown did not compromise agonist-induced ß-arrestin membrane recruitment; however, it prevents ß-arrestin dissociation from the membrane after prolonged quinpirole treatment during which time ß-arrestin moved away from the membrane in control cells. Additionally, confocal microscopy analysis of ß-arrestin post-endocytic fate revealed that quinpirole treatment caused ß-arrestin to translocate to the early and the recycling endosome in a time-dependent manner in control cells whereas translocation of ß-arrestin to these endosomes did not occur in RGS2 knockdown cells. The impaired ß-arrestin translocation likely contributed to the abolishment of quinpirole-stimulated D2R internalization in RGS2 knockdown cells. Thus, RGS2 is integral for ß-arrestin-mediated D2R internalization. The current study revealed a novel regulation of D2R signaling and internalization by RGS2 proteins.