Genome-wide shRNA screen revealed integrated mitogenic signaling between dopamine receptor D2 (DRD2) and epidermal growth factor receptor (EGFR) in glioblastoma

Abstract

Glioblastoma remains one of the deadliest of human cancers, with most patients succumbing to the disease within two years of diagnosis. The available data suggest that simultaneous inactivation of critical nodes within the glioblastoma molecular circuitry will be required for meaningful clinical efficacy. We conducted parallel genome-wide shRNA screens to identify such nodes and uncovered a number of G-Protein Coupled Receptor (GPCR) neurotransmitter pathways, including the Dopamine Receptor D2 (DRD2) signaling pathway. Supporting the importance of DRD2 in glioblastoma, DRD2 mRNA and protein expression were elevated in clinical glioblastoma specimens relative to matched non-neoplastic cerebrum. Treatment with independent si-/shRNAs against DRD2 or with DRD2 antagonists suppressed the growth of patient-derived glioblastoma lines both in vitro and in vivo. Importantly, glioblastoma lines derived from independent genetically engineered mouse models (GEMMs) were more sensitive to haloperidol, an FDA approved DRD2 antagonist, than the premalignant astrocyte lines by approximately an order of magnitude. The pro-proliferative effect of DRD2 was, in part, mediated through a GNAI2/Rap1/Ras/ERK signaling axis. Combined inhibition of DRD2 and Epidermal Growth Factor Receptor (EGFR) led to synergistic tumoricidal activity as well as ERK suppression in independent in vivo and in vitro glioblastoma models. Our results suggest combined EGFR and DRD2 inhibition as a promising strategy for glioblastoma treatment.

USP9X inhibition promotes radiation-induced apoptosis in non-small cell lung cancer cells expressing mid-to-high MCL1

“…15 The whole genome Hannon-Elledge pooled retroviral shRNA library contains 74,705 distinct shRNA sequences and targets nearly 18,000 known genes. 16 After transduction and antibiotic selection, cells were propagated with or without treatment with 1 Gy daily Monday-Friday. The IR schedule was selected to mimic clinical treatment, while a daily dose was selected that showed cytotoxicity yet maintained a sufficient number of cells for repeated culturing.…”

Dynamic epigenetic regulation of glioblastoma tumorigenicity through LSD1 modulation of MYC expression

“…S5B). Moreover, the expression levels of MYC, OLIG2, SOX2, and POU3F2 were elevated in a tumorigenic murine Cdkn2a (Ink4a/Arf), Pdgfb+ glioblastoma line (27,28) relative to its nontumorigenic precursor Cdkn2a (Ink4a/Arf) astrocyte line (Fig. 3D).…”

“…2I). Exogenous expression of platelet-derived growth factor beta (PDGFB) in the NSC/NPC line increased its tumorigenicity (27,28) (Fig. S4B).…”

Neuronal activity in the glioma microenvironment

“…Low-grade glioma-bearing mice treated with the tricyclic antidepressant imipramine exhibited prolonged survival, with decreased rate of tumor cell proliferation and reduced progression to high grade lesions; the mechanism of action appears to involve induction of autophagy, leading to apoptosis (Shchors et al, 2015). Glioblastoma cells express dopamine receptors (Dolma et al, 2016; Li et al, 2014), and in a proliferation screen performed on three patient-derived glioma cell cultures exposed to a panel of neurotransmitter agonists, antagonists, and reuptake inhibitors, pharmacologic blockade of dopamine receptor D4 emerged as an effective and selective inhibitor of glioma cell proliferation via disruption of autophagy and downstream induction of apoptosis (Dolma et al, 2016). Glioma cells also express functional serotonin receptors (Mahe et al, 2004), but whether serotonergic signaling influences glioma growth or progression is less clear, as increased serotonin levels as a result of selective serotonin reuptake inhibitor (SSRI) therapy have not been shown to have a survival benefit in retrospective studies of patients with glioblastoma and comorbid depression (Caudill et al, 2011).…”