This application focuses on identifying molecular mechanisms by which an emerging tumor suppressor sphingolipid ceramide regulates the expression of human telomerase reverse transcriptase (hTERT), a catalytic subunit of telomerase that maintains/elongates telomeres at the end of chromosomes, and plays important roles in the pathogenesis of lung and other cancers. On the other hand, ceramide is an established bio-effector sphingolipid, which mediates anti-proliferative biological responses, such as senescence, growth arrest, or apoptosis. Recent studies suggest that hTERT is important in the regulation of cancer cell growth and/or survival, independently of its function in the maintenance of telomeres without affecting net telomere length. Therefore, determining mechanisms that regulate hTERT expression is very important for both cancer research and therapy. In parallel with these data, our studies have revealed that ceramide is one of the upstream regulators of telomerase mediating the inhibition of hTERT expression in human lung cancer cells. The data showed that modulation of hTERT expression by ceramide is mechanistically linked to inactivation of its promoter via Sp3- and c-Myc-dependent pathways, involving their deacetylation or ubiquitination, respectively. Collectively, experimental evidence suggested a central hypothesis that ceramide mediates the inhibition of the hTERT transcription by Sp3- and c-Myc-dependent mechanisms, via their deacetylation and dephosphorylation-ubiquitination, coupled to the regulation of histone deacetylase 1 (HDAC1) and protein phosphatase 2A (PP2A), respectively. To test this hypothesis, two Specific Aims are proposed:
Specific Aim 1. Determine the role and mechanism of action of ceramide in Sp3-mediated regulation of hTERT expression;
and Specific Aim 2. Define the mechanisms by which ceramide prevents c-Myc-dependent activation of hTERT expression via regulation of its ubiquitination/degradation. These studies will define the mechanisms of ceramide-mediated repression of hTERT expression in the context of HDAC1 function, Sp3-acetylation, and the hTERT promoter network. In addition, they will help understand how ceramide regulates the function of PP2A directly, and will help dissect ceramide-mediated signaling that controls the hTERT promoter by c-Myc in human lung cancer compared to non-cancerous lung fibroblasts and normal bronchial epithelial cells. In the long-term, studies proposed in this application will help develop mechanism-based therapeutic strategies for the treatment of human lung cancer, which is the leading cause of cancer-related deaths in South Carolina and in the United States.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA088932-09
Application #
7893611
Study Section
Basic Mechanisms of Cancer Therapeutics Study Section (BMCT)
Program Officer
Arya, Suresh
Project Start
2000-12-01
Project End
2012-07-31
Budget Start
2010-08-01
Budget End
2011-07-31
Support Year
9
Fiscal Year
2010
Total Cost
$207,232
Indirect Cost
Name
Medical University of South Carolina
Department
Biochemistry
Type
Schools of Medicine
DUNS #
183710748
City
Charleston
State
SC
Country
United States
Zip Code
29425
Panneer Selvam, Shanmugam; Roth, Braden M; Nganga, Rose et al. (2018) Balance between senescence and apoptosis is regulated by telomere damage-induced association between p16 and caspase-3. J Biol Chem 293:9784-9800
Lv, Zongyang; Rickman, Kimberly A; Yuan, Lingmin et al. (2017) S. pombe Uba1-Ubc15 Structure Reveals a Novel Regulatory Mechanism of Ubiquitin E2 Activity. Mol Cell 65:699-714.e6
Thomas, Raquela J; Oleinik, Natalia; Panneer Selvam, Shanmugam et al. (2017) HPV/E7 induces chemotherapy-mediated tumor suppression by ceramide-dependent mitophagy. EMBO Mol Med 9:1030-1051
Lv, Zongyang; Yuan, Lingmin; Atkison, James H et al. (2017) Domain alternation and active site remodeling are conserved structural features of ubiquitin E1. J Biol Chem 292:12089-12099
Gencer, Salih; Oleinik, Natalia; Kim, Jisun et al. (2017) TGF-? receptor I/II trafficking and signaling at primary cilia are inhibited by ceramide to attenuate cell migration and tumor metastasis. Sci Signal 10:
Dany, Mohammed; Gencer, Salih; Nganga, Rose et al. (2016) Targeting FLT3-ITD signaling mediates ceramide-dependent mitophagy and attenuates drug resistance in AML. Blood 128:1944-1958
Dany, Mohammed; Ogretmen, Besim (2015) Ceramide induced mitophagy and tumor suppression. Biochim Biophys Acta 1853:2834-45
Panneer Selvam, Shanmugam; De Palma, Ryan M; Oaks, Joshua J et al. (2015) Binding of the sphingolipid S1P to hTERT stabilizes telomerase at the nuclear periphery by allosterically mimicking protein phosphorylation. Sci Signal 8:ra58
Jiang, Wenhui; Ogretmen, Besim (2014) Autophagy paradox and ceramide. Biochim Biophys Acta 1841:783-92
Qin, Zhiqiang; Dai, Lu; Trillo-Tinoco, Jimena et al. (2014) Targeting sphingosine kinase induces apoptosis and tumor regression for KSHV-associated primary effusion lymphoma. Mol Cancer Ther 13:154-64

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