Rlip (RLIP76, RALBP1) is a stress-responsive glutathione-electrophile conjugate (GS-E) transporter which is overexpressed in a number of types of cancers (lung, ovary, prostate, skin), but not in all types (breast, liver). Rlip appears to be necessary for cancer cell survival because both in-vitro cell culture and animal tumor studies show that depletion or inhibition of Rlip causes selective toxicity in malignant cells. Additional studies during the funded proposal have shown that differential sensitivity of SCLC to DOX as compared with NSCLC is related to lack of phosphorylation of Rlip by PKC alpha at T297, and that Rlip is required for the DOX-protective effects of PKC alpha. Experimental evidence by others investigators has provided direct links between Rlip and ral, cdc42, clathrin-adapter AP-2, POB1, epsin, grb2/nck, src, insulin, EGF-R, TGF beta, hsf-1 and heat shock proteins. These proteins are key elements of cell membrane plasticity, actin-cytoskeletal regulation and cell migration (cancer cell invasion and metastasis), receptor-ligand-pair endocytosis for signal termination, radiant and oxidant stress-responses, and apoptosis. Our preliminary studies show that Rlip represents an important rate-determining step for termination of EGF or insulin-signaling by endocytosis. The constellation of findings lead us to hypothesized that glutathione-conjugate efflux is a common effector mechanism utilized by membrane-signaling and stress-response pathways necessary for survival of cancer cells. In support of this hypothesis, we have shown regression of established tumors upon Rlip-depletion or inhibition in syngeneic mouse melanoma (Cancer Res. 66:2354, 2006), as well as lung cancer xenografts. We propose specific aims to test hypotheses in the following three areas: 1) In-vivo studies of efficacy, target specificity, and toxicity, 2) Regulation of Rlip by PKC alpha and tyrosine kinases, and 3) Regulation by signaling proteins including POB1 and cdc2 involved in endocytosis.

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National Cancer Institute (NCI)
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Basic Mechanisms of Cancer Therapeutics Study Section (BMCT)
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Forry, Suzanne L
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City of Hope/Beckman Research Institute
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Awasthi, Sanjay; Tompkins, Joshua; Singhal, Jyotsana et al. (2018) Rlip depletion prevents spontaneous neoplasia in TP53 null mice. Proc Natl Acad Sci U S A 115:3918-3923
Wurtzel, Jeremy G T; Lee, Seunghyung; Singhal, Sharad S et al. (2015) RLIP76 regulates Arf6-dependent cell spreading and migration by linking ARNO with activated R-Ras at recycling endosomes. Biochem Biophys Res Commun 467:785-91
Singhal, Sharad S; Singhal, Jyotsana; Figarola, James et al. (2015) RLIP76 Targeted Therapy for Kidney Cancer. Pharm Res 32:3123-36
Singhal, Sharad S; Singhal, Jyotsana; Figarola, James L et al. (2015) 2'-Hydroxyflavanone: A promising molecule for kidney cancer prevention. Biochem Pharmacol 96:151-8
Singhal, Sharad S; Singh, Sharda P; Singhal, Preeti et al. (2015) Antioxidant role of glutathione S-transferases: 4-Hydroxynonenal, a key molecule in stress-mediated signaling. Toxicol Appl Pharmacol 289:361-70
Figarola, James L; Singhal, Jyotsana; Rahbar, Samuel et al. (2014) LR-90 prevents methylglyoxal-induced oxidative stress and apoptosis in human endothelial cells. Apoptosis 19:776-88
Sahu, Mukesh; Sharma, Rajendra; Yadav, Sushma et al. (2014) Lens specific RLIP76 transgenic mice show a phenotype similar to microphthalmia. Exp Eye Res 118:125-34
Figarola, James Lester; Singhal, Preeti; Rahbar, Samuel et al. (2013) COH-SR4 reduces body weight, improves glycemic control and prevents hepatic steatosis in high fat diet-induced obese mice. PLoS One 8:e83801
Nagaprashantha, Lokesh Dalasanur; Talamantes, Tatjana; Singhal, Jyotsana et al. (2013) Proteomic analysis of signaling network regulation in renal cell carcinomas with differential hypoxia-inducible factor-2? expression. PLoS One 8:e71654
Yadav, Sushma; Sehrawat, Archana; Eroglu, Zeynep et al. (2013) Role of SMC1 in overcoming drug resistance in triple negative breast cancer. PLoS One 8:e64338

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