Abstract 220: SR4 uncouples mitochondrial oxidative-phosphorylation, modulates AMPK-mTOR signaling, and inhibits proliferation of HepG2 hepatocarcinoma cells

Mitochondrial oxidative phosphorylation produces most of the energy in aerobic cells by coupling respiration with the production of ATP. Mitochondrial uncouplers, which reduce the proton gradient across the mitochondrial inner membrane, create a futile cycle of nutrient oxidation without generating ATP. Regulation of mitochondrial dysfunction and associated cellular bioenergetics has been recently identified as promising targets for anticancer therapy. Here, we show that SR4 is a novel mitochondrial uncoupler that causes dose-dependent increase in mitochondrial respiration and dissipation of mitochondrial membrane potential (MMP) in HepG2 hepatocarcinoma cells. These effects were reversed by the recoupling agent 6-ketocholestanol, but not cyclosporin A, and were non-existent in mitochondria-DNA depleted HepG2 (po) cells. In isolated mouse liver mitochondria, SR4 similarly increased oxygen consumption independent of adenine nucleotide translocase (ANT) and uncoupling proteins, decreases MMP, and promotes swelling of valinomycin-treated mitochondria in potassium acetate media. Mitochondrial uncoupling in HepG2 cells by SR4 results in the reduction of cellular ATP production, increased ROS production, activation of the energy-sensing enzyme AMPK, and inhibition of acetyl-CoA carboxylase and mammalian target of rapamycin (mTOR) signaling pathways, leading to cell cycle arrest and apoptosis. Global analysis of SR4-associated differential gene expression confirms these observations, including significant induction of apoptotic genes and down regulation of cell cycle, mitochondrial and oxidative-phosphorylation pathway transcripts at 24 h post treatment. Collectively, our studies demonstrate that SR4's previously reported indirect activation of AMPK and in-vitro anticancer properties, as well as its beneficial effects in both animal xenograft and obese mice models could be a direct consequence of its mitochondrial uncoupling activity (Supported by NIH grant CA 77495 and Beckman Research Institute of the City of Hope).

Citation Format: Sharad S. Singhal, James Figarola, Jyotsana Singhal, Joshua Tompkins, David Horne, Sanjay Awasthi, Arthur Riggs. SR4 uncouples mitochondrial oxidative-phosphorylation, modulates AMPK-mTOR signaling, and inhibits proliferation of HepG2 hepatocarcinoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 220.

Abstract 2816: 2′-Hydroxyflavanone inhibits lung cancer growth by inhibiting tumor cell proliferation and angiogenesis

Lung cancer remains the number one cause of cancer mortality in the US. Although systemic chemotherapy and novel biologic agents have been shown to improve survival, toxicities are often severe and effective preventive therapy has not been defined. Intake of flavonoids from citrus fruits has been shown to decrease the risk of lung cancer in large scale epidemiologic studies. Hence, we studied the biologic anti-lung cancer effects of 2HF, a naturally occurring compound in citrus fruits. Our in-vitro investigations revealed that 2HF inhibits the growth of bronchogenic adeno-, squamous and small cell lung carcinoma. This was associated with G2/M arrest, collapse in mitochondrial membrane potential (Δψm), and apoptosis. We demonstrated a down-regulation of fibronectin and key signaling proteins of the PI3K pathway. RLIP76 expression was significantly reduced by 2HF, and the survival as well as 14C-DOX transport on purified reconstituted-proteoliposomes prepared from H1618 and H358 cells was significantly inhibited, an effect which was synergistic with anti-RLIP76 IgG. Our in-vivo studies in mice xenografts confirmed our in-vitro results by marked reduction of tumor growth, which was paralleled by a reduction in Ki67 and CD31, as proliferative and angiogenic markers, respectively. Importantly, 2HF also reduced the level of vimentin and increased E-cadherin, reversing the phenotype of epithelial-to-mesenchymal transition. In summary, 2HF demonstrated strong anti-proliferative, anti-angiogenic and pro-differentiation effects on in-vitro and in-vivo lung cancer models, whilst sparing normal cells. This holds not only great promise for therapeutic use but also suggests a role for 2HF in the prevention of lung cancer (Supported by NIH grant CA 77495 and Beckman Research Institute of the City of Hope).

Citation Format: Sharad S. Singhal, James Figarola, Jyotsana Singhal, Lokesh Nagaprashantha, Sanjay Awasthi. 2′-Hydroxyflavanone inhibits lung cancer growth by inhibiting tumor cell proliferation and angiogenesis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2816. doi:10.1158/1538-7445.AM2015-2816

Abstract 2149: Novel compound 1, 3-bis (3, 5-dichlorophenyl) urea inhibits lung cancer progression

The successful clinical management of lung cancer is limited by frequent loss-of-function mutations in p53 which cooperates with chronic oxidant-stress induced adaptations in mercapturic acid pathway (MAP) which in turn regulates critical intracellular signaling cascades that determine therapeutic refractoriness. Hence, we investigated the anti-cancer effects and mechanisms of action of a novel compound called 1, 3 bis (3, 5-dichlorophenyl) urea (COH-SR4) in lung cancer. Treatment with COH-SR4 effectively inhibited the survival and clonogenic potential along with inducing apoptosis in lung cancer cells. COH-SR4 treatment caused the inhibition of GST activity and G0/G1 cell cycle arrest and inhibited the expression of cell cycle regulatory proteins CDK2, CDK4, cyclin A, cyclin B1, cyclin E1, and p27. The COH-SR4 activated AMPK pathway and knock-down of AMPK partially reversed the cytotoxic effects of COH-SR4 in lung cancer. COH-SR4 treatment lead to regression of established xenografts of H358 lung cancer cells without any overt toxicity. The histopathology of resected tumor sections revealed an increase in pAMPK, a decrease in the nuclear proliferative marker Ki67 and angiogenesis marker CD31. Western-blot analyses of resected tumor lysates revealed a decrease in pAkt and anti-apoptotic protein Bcl2 along with an increase in pAMPK, pro-apoptotic protein Bax and cleaved PARP levels. Importantly, COH-SR4 lead to decrease in the mesenchymal marker vimentin and increase in the normal epithelial marker E-cadherin. The results from our in-vitro and in-vivo studies reveal that COH-SR4 represents a novel candidate with strong mechanistic relevance to target aggressive and drug-resistant lung tumors (Supported by NIH grant CA 77495 and Beckman Research Institute of the City of Hope).

Note: This abstract was not presented at the meeting.

Citation Format: Sharad S. Singhal, James Figarola, Jyotsana Singhal, Lokesh Nagaprashantha, David Berz, Samuel Rahbar, Sanjay Awasthi. Novel compound 1, 3-bis (3, 5-dichlorophenyl) urea inhibits lung cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2149. doi:10.1158/1538-7445.AM2014-2149

Novel compound 1,3-bis (3,5-dichlorophenyl) urea inhibits lung cancer progression

The successful clinical management of lung cancer is limited by frequent loss-of-function mutations in p53 which cooperates with chronic oxidant-stress induced adaptations in mercapturic acid pathway (MAP) which in turn regulates critical intracellular signaling cascades that determine therapeutic refractoriness. Hence, we investigated the anti-cancer effects and mechanisms of action of a novel compound called 1,3-bis(3,5-dichlorophenyl) urea (COH-SR4) in lung cancer. Treatment with COH-SR4 effectively inhibited the survival and clonogenic potential along with inducing apoptosis in lung cancer cells. COH-SR4 treatment caused the inhibition of GST activity and G0/G1 cell cycle arrest and inhibited the expression of cell cycle regulatory proteins CDK2, CDK4, cyclin A, cyclin B1, cyclin E1, and p27. The COH-SR4 activated AMPK pathway and knock-down of AMPK partially reversed the cytotoxic effects of COH-SR4 in lung cancer. COH-SR4 treatment lead to regression of established xenografts of H358 lung cancer cells without any overt toxicity. The histopathology of resected tumor sections revealed an increase in pAMPK, a decrease in the nuclear proliferative marker Ki67 and angiogenesis marker CD31. Western-blot analyses of resected tumor lysates revealed a decrease in pAkt and anti-apoptotic protein Bcl2 along with an increase in pAMPK, pro-apoptotic protein Bax and cleaved PARP levels. Importantly, COH-SR4 lead to decrease in the mesenchymal marker vimentin and increase in the normal epithelial marker E-cadherin. The results from our in-vitro and in-vivo studies reveal that COH-SR4 represents a novel candidate with strong mechanistic relevance to target aggressive and drug-resistant lung tumors.

RLIP76 protein knockdown attenuates obesity due to a high-fat diet

Feeding a Western high-fat diet (HFD) to C57BL/6 mice induces obesity, associated with a chronic inflammatory state, lipid transport, and metabolic derangements, and organ system effects that particularly prominent in the kidneys. Here, we report that RLIP76 homozygous knock-out (RLIP76(-/-)) mice are highly resistant to obesity as well as these other features of metabolic syndrome caused by HFD. The normal increase in pro-inflammatory and fibrotic markers associated with HFD induced obesity in wild-type C57B mice was broadly and nearly completely abrogated in RLIP76(-/-) mice. This is a particularly striking finding because chemical markers of oxidative stress including lipid hydroperoxides and alkenals were significantly higher in RLIP76(-/-) mice. Whereas HFD caused marked suppression of AMPK in wild-type C57B mice, RLIP76(-/-) mice had baseline activation of AMP-activated protein kinase, which was not further affected by HFD. The baseline renal function was reduced in RLIP76(-/-) mice as compared with wild-type, but was unaffected by HFD, in marked contrast to severe renal impairment and glomerulopathy in the wild-type mice given HFD. Our findings confirm a fundamental role of RLIP76 in regulating the function of obesity-promoting pro-inflammatory cytokines, and provide a novel mechanism for targeted therapy of obesity and metabolic syndrome.

Abstract 5518: A novel 1,3-bis(3,5-dichlorophenyl) urea compound ‘COH-SR4’ for targeting melanoma

The current clinical modalities in the management of malignant melanomas are met with limited response. The molecular events that regulate oncogenic transformation, invasive progression and resistance to therapy in melanomas are determined by an interplay between various complex signaling networks. In the context of evident demographic risk, limited response to current clinical interventions and molecular complexity of melanomas, novel candidate molecules capable of effectively inducing tumor inhibition along with targeting critical nodes of melanoma signaling assume translational significance. In this regard, we investigated the anti-cancer effects of a novel dichlorophenyl urea compound called SR4 in melanoma. The SR4 treatment decreased the survival and inhibited the clonogenic potential along with inducing apoptosis in vitro cultures of melanoma. SR4 treatments lead to inhibition of GST activity along with inducing G2/M phase cell cycle arrest. Oral administration of 4 mg/kg b.w. SR4 leads to effective inhibition of tumor burdens in both syngeneic and nude mouse models of melanoma. The SR4 treatment was well tolerated and no overt toxicity was observed. The histopathological examination of resected tumor sections reflected decreased blood vessels, decrease in the levels of angiogenesis marker, CD31, and proliferation marker, Ki67, along with an increase in pAMPK levels. Western blot analyses of resected tumor lysates revealed increased PARP cleavage, Bim, pAMPK along with decreased pAkt, vimentin, fibronectin, CDK4 and cyclin B1. Thus, SR4 represents a highly effective candidate for the further development of single agent and combinatorial therapies to effectively target aggressive and clinically resistant melanomas (Supported by NIH grant CA 77495).

Citation Format: Lokesh Prasad Gowda Dalasanur Nagaprashantha, James Figarola, Jyotsana Singhal, David Horne, Richard Jove, Samuel Rahbar, Sanjay Awasthi, Sharad S Singhal. A novel 1,3-bis(3,5-dichlorophenyl) urea compound ‘COH-SR4’ for targeting melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5518. doi:10.1158/1538-7445.AM2013-5518