Rgnef promotes ovarian tumor progression and confers protection from oxidative stress

Abstract

Ovarian cancer is the fifth-leading cause of cancer death among women. The dissemination of ovarian tumors and growth as spheroids accompanies late stage disease. In cell culture, ovarian tumor cell spheroids can exhibit elevated resistance to environmental stressors such as reactive oxygen species. Homeostatic balance of the antioxidant response is a protective mechanism that prevents anoikis, a form of programmed cell death. Signaling pathways activated by integrin receptors suppress anoikis. Rgnef (ARHGEF28/p190RhoGEF) is a guanine nucleotide exchange factor that is activated downstream of integrins. We find that Rgnef protein levels are elevated in late-stage serous ovarian cancer, high Rgnef mRNA levels are associated with decreased progression-free and overall survival, and genomic ARHGEF28 loss is associated with increased patient survival. Using transgenic and transplantable Rgnef knockout mouse models, we find that Rgnef is essential for supporting three-dimensional ovarian spheroid formation in vitro and tumor growth in mice. Using RNA-sequencing and bioinformatic analyses, we identify a conserved Rgnef-supported anti-oxidant gene signature including GPX4, Nqo1, and Gsta4; common targets of the NF-kB transcription factor. Antioxidant treatment enhanced growth of Rgnef-knockout spheroids and Rgnef re-expression facilitated NF-κB-dependent tumorsphere survival. These studies reveal a new role for Rgnef in ovarian cancer to facilitate NF-κB-mediated gene expression protecting cells from oxidative stress.

FAK activity sustains intrinsic and acquired ovarian cancer resistance to platinum chemotherapy

“…This may be due to weak oncogenic activity of the β-catenin ΔGSK construct (Barth et al, 1999) or due to a supporting requirement for FAK. Additionally, the FAK-associated protein Rgnef is also essential for KMF tumorsphere growth and protection from oxidative stress (Kleinschmidt et al, 2019). We show that FAK expression and intrinsic activity are essential for KMF tumor growth and that elevated FAK activity and Y397 phosphorylation is an acquired and targetable cellular adaptation of cisplatin resistance in HGSOC.…”

Drugs Targeting Tumor-Initiating Cells Prolong Survival in a Post-Surgery, Post-Chemotherapy Ovarian Cancer Relapse Model

“…OC TICs may prefer oxidative phosphorylation rather than glycolysis in cellular stress in order to maintain stemness [ 27 ]. The OC tumor microenvironment also contributes to the growth of resilient TICs that adapt to oxidative stress and excessive reactive oxygen species (ROS) generated by de-adhesion, chemotherapeutic agents and hypoxia [ 28 , 29 ]. OC TICs may also have enhanced drug metabolism [ 15 ], anoikis resistance [ 29 ] and metabolic plasticity [ 30 ].…”

“…The OC tumor microenvironment also contributes to the growth of resilient TICs that adapt to oxidative stress and excessive reactive oxygen species (ROS) generated by de-adhesion, chemotherapeutic agents and hypoxia [ 28 , 29 ]. OC TICs may also have enhanced drug metabolism [ 15 ], anoikis resistance [ 29 ] and metabolic plasticity [ 30 ]. In environments of elevated ROS and oxidative stress, enhanced antioxidant and drug metabolism responses provide a survival advantage for TICs, but also point to a potential vulnerability [ 27 ].…”

Inclusion Formation and Toxicity of the ALS Protein RGNEF and Its Association with the Microtubule Network

“…RGNEF is a multidomain protein with a combination of a GEF and RNA binding domain that is unique within the human proteome, together with many other functional domains, yet its basic biological function is just starting to be clarified [ 20 ]. It has been implicated in a number of diseases, including cancer and neurodegenerative diseases, particularly in ALS [ 16 , 17 , 19 , 23 , 24 , 26 , 40 , 41 , 42 ]. RGNEF is similar to some of the other common ALS-associated proteins, such as TDP-43 and FUS, as it binds RNA and localizes to pathological NCIs [ 15 , 16 , 17 , 26 ].…”

“…RGNEF belongs to the family of diffuse B-cell lymphoma (Dbl) GEFs and contains a leucine-rich region at its amino-terminus, a Plekstrin homology domain (PH), a cysteine-rich Zink-finger domain, FAK (focal adhesion kinase) binding domain, microtubule binding domain, and an nuclear localization signal (NLS, [ 18 ]. The normal cellular function of RGNEF is not well understood; however, it has been linked to multiple disorders in addition to ALS, including cancer, e.g., colorectal and ovarian cancer [ 19 , 20 , 21 , 22 , 23 ].…”