Inappropriate activation/inactivation of key signals that control cell survival after genotoxic insult can contribute to autonomous growth and neoplastic transformation. An initial consequence of genotoxic injury is cell cycle checkpoint arrest but genotoxicity may also activate cell death pathways of apoptosis or terminal growth arrest. Cellular survival responses to genotoxic insult may produce intrinsic death-resistance; such a selective growth advantage may allow for emergence of a transformed phenotype. Certain forms of hexavalent chromium [(Cr(VI)] are known human respiratory carcinogens that can be employed as useful genotoxic tools with relevant toxicological importance. Our preliminary studies suggest that maintenance of protein tyrosine phosphorylation, which is coincident with AKT activation, overrides Cr-induced growth arrest and enhances clonogenic survival. Constitutive AKT activation is known to play an important role in carcinogenesis. Therefore, the overall objective of this proposal is to elucidate the coordinate signaling events that mediate cell fate determination and survival after genotoxic insult. The dual overarching hypotheses of the proposed studies are that: 1) AKT activation shifts the balance of cell fates, toward survival, after Cr(Vl) genotoxic insult; and 2) AKT activation in the face of Cr(Vl) genotoxic insult increases genomic instability. To test these hypotheses, we will employ molecular, pharmacological and genetic approaches, by using relevant model systems of human diploid lung fibroblasts (HLF), and human large airway epithelial cells (HLAE) and studying the involvement of key signaling components of the AKT pathway. The molecular circuitry of the AKT effect will be delineated in Aim 1, and the consequences of an AKT-induced """"""""override"""""""" of the genotoxin-elicited program of cell death will be investigated in Aim 2.
Aim 3 will identify the role of AKT in resistance to Cr(Vl)-induced clonogenic lethality in a subclonal population of cells with acquired resistance to Cr- induced clonogenic death. We will use soluble Na2CrO4 at a range of concentrations relevant to human exposure, and for which the DNA adduct frequencies and genotoxic lesions are well documented. Results of the proposed studies will identify molecular mechanism(s) that confer a growth advantage to cells after genotoxic insult, and add new insights to the understanding of Cr(Vl)-induced lung carcinogenesis, while addressing a need for sensitive and specific molecular indices that can be correlated with exposure to carcinogenic agents, as well as with their cancer incidence. Delineation of the molecular circuitry involved in AKT survival signaling may have the added benefit of identifying molecular targets for rational drug design in anti-cancer therapy.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
3R01CA107972-04S1
Application #
7545032
Study Section
Cancer Etiology Study Section (CE)
Program Officer
Ogunbiyi, Peter
Project Start
2005-01-01
Project End
2009-12-31
Budget Start
2008-01-01
Budget End
2008-12-31
Support Year
4
Fiscal Year
2008
Total Cost
$54,309
Indirect Cost
Name
George Washington University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
043990498
City
Washington
State
DC
Country
United States
Zip Code
20052
Nickens, Kristen P; Wikstrom, Jakob D; Shirihai, Orian S et al. (2013) A bioenergetic profile of non-transformed fibroblasts uncovers a link between death-resistance and enhanced spare respiratory capacity. Mitochondrion 13:662-7
Kost, Gina Chun; Patierno, Steven R; Wise, Sandra S et al. (2012) Protein tyrosine phosphatase (PTP) inhibition enhances chromosomal stability after genotoxic stress: decreased chromosomal instability (CIN) at the expense of enhanced genomic instability (GIN)? Mutat Res 735:51-5
Nickens, Kristen P; Han, Ying; Shandilya, Harini et al. (2012) Acquisition of mitochondrial dysregulation and resistance to mitochondrial-mediated apoptosis after genotoxic insult in normal human fibroblasts: a possible model for early stage carcinogenesis. Biochim Biophys Acta 1823:264-72
Chun, Gina; Bae, Dongsoon; Nickens, Kristen et al. (2010) Polo-like kinase 1 enhances survival and mutagenesis after genotoxic stress in normal cells through cell cycle checkpoint bypass. Carcinogenesis 31:785-93
Nickens, Kristen P; Patierno, Steven R; Ceryak, Susan (2010) Chromium genotoxicity: A double-edged sword. Chem Biol Interact 188:276-88
Lal, Madhu A; Bae, Dongsoon; Camilli, Tura C et al. (2009) AKT1 mediates bypass of the G1/S checkpoint after genotoxic stress in normal human cells. Cell Cycle 8:1589-602
Bae, Dongsoon; Camilli, Tura C; Chun, Gina et al. (2009) Bypass of hexavalent chromium-induced growth arrest by a protein tyrosine phosphatase inhibitor: enhanced survival and mutagenesis. Mutat Res 660:40-6
Beaver, Laura M; Stemmy, Erik J; Constant, Stephanie L et al. (2009) Lung injury, inflammation and Akt signaling following inhalation of particulate hexavalent chromium. Toxicol Appl Pharmacol 235:47-56
Beaver, Laura M; Stemmy, Erik J; Schwartz, Arnold M et al. (2009) Lung inflammation, injury, and proliferative response after repetitive particulate hexavalent chromium exposure. Environ Health Perspect 117:1896-902
Bae, Dongsoon; Ceryak, Susan (2009) Raf-independent, PP2A-dependent MEK activation in response to ERK silencing. Biochem Biophys Res Commun 385:523-7

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