Evaluation and Functional Analysis of Cancer Susceptibility Gene Products
In the post-genomic era, a myriad of genes and genetic loci are being implicated in the processes of tumor initiation, promotion and metastasis. This deluge of potential new cancer genes necessitates a systematic delineation of true cancer susceptibility genes and their mechanism of action. My primary research focus is to identify genes that contribute to cancer susceptibility and determine their mechanism of action through in-vitro and in-vivo approaches. The application of murine modeling, cell biology and molecular biology techniques has allowed us to elucidate roles for the 6q gene, RGS17, in lung tumorigenesis through the cAMP/PKA/CREB signaling axis; for cis-regulated Xrn2 in proliferation and differentiation processes in human lung epithelial cells; and for other gene products modifying tumor risk. Newly elucidated targets and signaling pathways ideally guide cancer therapy and chemoprevention. We apply in-vitro observations to models of tumorigenesis, chemoprevention and bioavailability. In the ongoing study of the functional roles of lung tumor susceptibility gene products, we are utilizing a conditional, viral induced K-Ras lung tumor model in concert with modulation of expression of genes of interest in induced cells.
Modulation of Genotoxic Apoptosis as a Mechanism for Promotion of Tumorigenesis by CLPTM1L
Cleft lip and palate transmembrane protein 1 (CLPTM1L) resides in a region of chromosome 5 for which copy number gain has been found to be the most frequent genetic event in the early stages of non-small cell lung cancer (NSCLC) (Kang et al., 2008) and has been found by multiple genome wide association studies to be associated with lung cancer in both smokers and non-smokers. Furthermore, polymorphism within the CLPTM1L gene has also been found to be associated with a higher accumulation of DNA damage (Zienolddiny et al., 2009). We have found CLPTM1L expression to be increased in over 80% of lung tumors compared to normal lung tissues and to protect lung tumor cells from DNA damage induced apoptosis through regulation of Bcl-xL.
Current directions include evaluating the direct effect of CLPTM1L on the development of lung tumors through these mechanisms. This will be partially accomplished by modulating CLPTM1L expression in a viral induced K-Ras lung tumor model in mice. Continued sequencing efforts to determine if coding variants affecting lung cancer susceptibility exist and evaluation of association of significant SNPs with expression of CLPTM1L are important next steps in delineating a causal relationship of CLPTM1L with lung tumor susceptibility. Targeting CLPTM1L as well as Bcl-xL may prove useful in chemopreventive and therapeutic capacities. Targeting these anti-apoptotic proteins may also have potential for sensitization to traditional chemotherapeutic agents.
Molecular Mechanisms of Chemoprevention
Environmental exposure to carcinogens, genetic risk and pre-neoplastic lesions identify individuals at risk for the development of lung cancer. Chemopreventive measures are an attractive means of impacting the high rates of lung cancer morbidity and mortality. There exists a lack of clear molecular targets and mechanisms of currently studied potential chemopreventive agents. We have published studies investigating the nature of the chemopreventive properties of agents such as berberine and pioglitazone. We continue to study these mechanisms in more depth and for other agents. It is our goal to reveal new molecular targets for chemoprevention and therapy through the investigation of the mechanisms of anti-tumorigenesis by these agents.
James MA, Wen W, You M. CLPTM1L is Overexpressed in Non-Small Cell Lung Tumors and Confers Resistance to Cisplatin Induced Apoptosis in NSCLC Cells through Regulation of Bcl-xL. (under review at Cancer Research)
Wang Y, James MA, Wen W, He J, Lu Y, Szabo E, Lubet R, and You M. Chemopreventive Effects of Pioglitazone on Chemically Induced Lung Carcinogenesis in Mice. (under review at Molecular Cancer Therapeutics)
Fu H, Liu Y, Chen D, and You M. Dietary Administration of Berberine Alone or in Phellodendron amurense Extract is Equally Effective in the Inhibition of Lung Tumorigenesis. (In Press at Molecular Carcinogenesis)
Lu Y, Liu PY, James MA, Vikis H, Liu H, Wen W, Franklin A and You M. Genetic Variants Cis-regulating Xrn2 Expression Contribute to the Risk of Spontaneous Lung Cancer. Oncogene. 28(45) 2009
Liu PY, Vikis H, James MA, Lu Y, Wang DL, Liu HB, Wen WD, Wang Y, You M. Haplotype and cell proliferation analyses of candidate lung cancer susceptibility genes on chromosome 15q24-25.1. Cancer Res. 69(19):7844-50 2009
Liu Y, Vikis H, James MA, Lu Y, Wang DL, Liu HB, Wen W, Wang Y, You M. Identification of Las2, a Major Modifier Gene Affecting the Pas1 Mouse Lung Tumor Susceptibility Locus. Cancer Res. 69(15):6290-8 2009
You M, Wang D, Liu P, Vikis H, James MA, Lu Y, Wang Y, et al. Fine mapping of chromosome 6q23-25 region in familial lung cancer families reveals RGS17 as a likely candidate gene. Clin. Can. Res. 15(8):2666-74 2009
James MA, Lu Y, Liu Y, Vikis HG, You M. RGS17, an Overexpressed Gene in Human Lung and Prostate Cancer, Induces Tumor Cell Proliferation Through the cAMP-PKA-CREB Pathway. Cancer Res. 69(5):2108-16 2009
Lu Y, Yi Y, Liu P, Wen W, James MA, Wang D, You M. Common human cancer genes discovered by integrated gene-expression analysis. PLoS ONE. 2007 Nov 7;2(11):e1149.
Vikis H, Sato M, James MA, Wang D, Wang Y, Wang M, Jia D, Liu Y, Bailey-Wilson JE, Amos CI, Pinney SM, Petersen GM, de Andrade M, Yang P, Wiest JS, Fain PR, Schwartz AG, Gazdar A, Gaba C, Rothschild H, Mandal D, Kupert E, Seminara D, Viswanathan A, Govindan R, Minna J, Anderson MW, You M.EGFR-T790M is a rare lung cancer susceptibility allele with enhanced kinase activity. Cancer Res. 2007 May 15;67(10):4665-70.
James MA, Lee JH, Klingelhutz AJ. HPV16-E6 associated hTERT promoter acetylation is E6AP dependent, increased in later passage cells and enhanced by loss of p300. Int J Cancer. 2006 Oct 15;119(8):1878-85.
James MA, Lee JH, Klingelhutz AJ. Human papillomavirus type 16 E6 activates NF-kappaB, induces cIAP-2 expression, and protects against apoptosis in a PDZ binding motif-dependent manner. J Virol. 2006 Jun;80(11):5301-7.