Our work focuses on the role of Transforming Growth Factor Beta (TGF-ß) in cancer development and progression. TGF-ß is one of the most potent inhibitor of normal cell growth. TGF-ß signaling and growth-inhibition are mediated by the type I TGF-ß receptor (TGFBR1). In a search for mutations of this receptor we have identified a common variant, TGFBR1*6A. TGFBR1*6A has a deletion of three GCG triplets coding for alanine within a nine alanine (9A) repeat of TGFBR1 exon 1 resulting in six alanines (6A) repeats. In normal epithelial cells TGFBR1*6A (*6A) mediates TGF-ß growth inhibitory signals less effectively than TGFBR1 (*9A). In cancer cells *6A is capable of switching TGF-ß growth inhibitory signals into growth stimulatory signals. This appears to be mediated by *6A signal sequence. Our laboratory has shown that *6A is somatically acquired in a large proportion of liver metastases from colon cancer. *6A is a candidate tumor susceptibility allele that has been associated with an increased incidence of various types of cancer. TGFBR1*6A carriers have a significantly increased risk of cancer as compared with non-carriers. We have shown that overall cancer risk is increased by 13% among TGFBR1*6A heterozygotes and 104% among TGFBR1*6A homozygotes, which is indicative of an allelic dosing effect. Analysis of various types of tumors shows that TGFBR1*6A homozygotes have an increased risk of developing breast (169%), colon (102%), ovarian (107%) and prostate cancer (200%). More than one in seven healthy individuals and one in six patients with cancer is a *6A carrier. This sets a new paradigm and establishes *6A as the first high-frequency, low-penetrance tumor susceptibility allele. There is substantial epidemiologic, functional as well as genetic evidence pointing towards a significant *6A role in cancer development. However, little is known about its function. Our laboratory has the following ongoing projects:
1) Mouse model of TGFBR1*6A: We have established knock-in mouse models representative of the three most common human genotypes, hTGFBR1/hTGFBR1, hTGFBR1/hTGFBR1*6A and hTGFBR1*6A/hTGFBR1*6A. We have also generated a Tgfbr1 knockout strain to allow for the study of hTGFBR1/- and hTGFBR1*6A/- haploinsufficiency. We are in the process of determining each strain’s susceptibility to spontaneous tumor development as well as tumor development upon challenge to experimental carcinogenesis. We will determine the impact of hTGFBR1*6A as a modifier of cancer development. We will cross hTGFBR1*6A/hTGFBR1*6A as well as hTGFBR1/hTGFBR1 strains with mouse models of breast and colon cancer.
2) Molecular characterization of TGFBR1*6A: The 9-bp deletion that differentiates TGFBR1*6A from TGFBR1 is located within the predicted signal peptide cleavage site of TGFBR1. We have determined the cleavage site of *6A and *9A signal sequences and we are in the process of assessing their affinity for the signal recognition peptide. There is epidemiologic evidence that TGFBR1*6A may act as a dominant negative allele. Other mechanisms, either TGF-ß signaling-dependent or TGF-ß-signaling independent may account for TGFBR1*6A tumor susceptibility effects. Using mink lung epithelial cell lines stably transfected either with TGFBR1 or TGFBR1*6A as well as cancer cell lines we are analyzing the differential gene responses between TGFBR1 and TGFBR1*6A. We will use microarrays to analyze the gene expression profile of untreated cells, cells treated for two hours with TGF-b and cell treated for 24 hours with TGF-ß. We will further characterize the differentially expressed genes of interest by overexpression in epithelial cells lines in order to identify a phenotype associated with the differentially expressed genes.
3) Epidemiologic studies: there is growing evidence that TGFBR1*6A may predispose to the development of several malignancies. There is also evidence that other naturally-occurring variants of the TGF-ß signaling pathway such as TGFB1 T29C may modify cancer risk. Furthermore, we have recently shown that gene-gene interactions between TGFB1 T29C and TGFBR1*6A may predict breast cancer risk in up to 30% of the general population. We will validate the association between TGFB1 T29C, TGFBR1*6A, and colorectal as well as breast cancer through a discordant sibling case control association study, which will use all available sibling pairs from the NCI-sponsored familial cancer registries. We will identify and genotype cases and their control siblings.
Our work is funded by National Cancer Institute and the Walter Mander Foundation in Chicago.
Publications:
Kaklamani, V, Hou, N, Bian, Y, Reich, J, Offit, K, Michel, L, Rubinstein, WS, Rademaker, A, Pasche, B. TGFBR1*6A and cancer risk: is a high frequency, low penetrance tumor susceptibility allele AA meta-analysis of seven case-control studies. Journal of Clinical Oncology, 21:3236-3243, 2003
Pasche, B, Kaklamani, V, Hou, N, Young, T, Rademaker, A, Peterlongo, P, Ellis, N, Offit, K, Caldes, T, Reiss, M, Zheng, T. TGFBR1*6A and cancer: a meta-analysis of twelve case control studies. Journal of Clinical Oncology, 22:756-758, 2004
Bian, Y., Caldes, T., Wijnen, J., Franken, P., Vasen, H., Kaklamani, V., Nafa, K., Peterlongo, P., Ellis, N., Baron, J.A., Burn, J., Moeslein, G. Morrison, P.J., Chen, Y., Ahsan, H., Watson, P., Lynch, H.T., de la Chapelle, A, Fodde, R, Pasche, B. TGFBR1*6A may contribute to hereditary colorectal cancer. Journal of Clinical Oncology, 23:3074-3078, 2005
Kaklamani, V., Baddi, L., Liu, J., Rosman, D., Bradley, C., Hegarty, C., McDaniel, B., Rademaker, A., Oddoux, C., Ostrer, H., Michel, L., Chen, Y., Ahsan, H., Offit, K., Pasche, B. Combined genetic assessment of common TGF-ß signaling pathway variants may predict breast cancer risk. Cancer Research, 65:3454-3461, 2005
Pasche, B., Knobloch, T.J., Bian, Y, Liu, J., Phukan, S., Rosman, D., Kaklamani, V., Baddi, L., Siddiqui, F.S., Frankel, W.L., Prior, T.W., Schuller, D.E., Agrawal, A., Lang, J., Dolan, E., Vokes, E.E., Lane, W.S., Huang, C.-C., Caldes, T., Di Cristofano, A., Hampel, H., Nilsson, I., von Heijne, G., Fodde, R., Murty, V.V.V.S., de la Chapelle, A., Weghorst, C.W. Somatic acquisition and signaling of TGFBR1*6A in cancer. Journal of the American Medical Association, 294:1634-1646, 2005
Pasche, B. A New Strategy in the War on Renal Cell Cancer: Hitting Multiple Targets With Limited Collateral Damage
Journal of the American Medical Association, 295:2537-2538, 2006
Pennison M, Pasche B. Targeting transforming growth factor-beta signaling. Curr Opin Oncol. 2007 Nov;19(6):579-85.
Xu Y, Pasche B. TGF-beta signaling alterations and susceptibility to colorectal cancer. Hum Mol Genet. 2007 Apr 15;16 Spec No 1:R14-20.
Bian Y, Knobloch TJ, Sadim M, Kaklamani V, Raji A, Yang GY, Weghorst CM, Pasche B. Somatic acquisition of TGFBR1*6A by epithelial and stromal cells during head and neck and colon cancer development.
Hum Mol Genet. 2007 Sep 21; [Epub ahead of print]
Rosman DS, Kaklamani V, Pasche B. New insights into breast cancer genetics and impact on patient management.
Curr Treat Options Oncol. 2007 Feb;8(1):61-73.
Rosman, D., Phukan S., Huang, C.-C., Pasche, B. TGFBR1*6A enhances migration and invasion of MCF-7 breast cancer cells through RhoA activationCancer Research 2008, 68:1319-1328
Kaklamani, V., Sadim, M., Hsi, A., Offit, K., Oddoux, C., Ostrer, H., Ahsan, H., Pasche, B., Mantzoros, C. Breast cancer risk and variants of the Adiponectin and Adiponectin 1 receptor genes. Cancer Research 2008, 68:3178-3184
