Akhurst Lab

Full Biosketch: Rosemary J. Akhurst, PhD

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(415) 514-0215 (direct)
(415) 502-4180 (admin. asst.)
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1450 3rd St., MC 0128; PO Box 589001
San Francisco, CA 94158-9001

deliveries: 1450 3rd Street, HD-320; San Francisco, CA 94158

The goal of our research program is to dissect the molecular mechanisms that regulate critical functions of TGF-beta1 during tumorigenesis and in vascular biology in vivo, and to relate this to therapeutics and the assessment of risk for human disease, particularly cancer and cardiovascular disease.

Over the last decade it has become increasingly apparent that the TGF-beta pathway is a central player in several human diseases, including cancer and cardiovascular disease, when its expression is often elevated in the pathological state (1, 2). The importance of TGF-beta1 in driving tumor progression and metastasis is now widely recognized, and pharmaceutical companies have developed a panel of TGF-beta inhibitory drugs for cancer treatment, some of which have already entered the clinic (3, 4). Despite these developments, the exact mechanism of action of these drugs is not known (e.g. predominant cellular target for each tumor type, systemic or localized effects etc.). TGF-beta action is highly context-dependent (2), and thus expected outcome in terms of tumor responses and potential side-effects will be difficult to predict.

In addition to its central role in cancer, several congenital vasculopathies have been shown to be caused by mutations in genes encoding components of the TGF-beta signaling pathway, or genes that alter TGF-beta signaling (1, 5, 6). Thus, chemical genomics approaches to disease treatment have suggested the use of TGF-beta agonists and/or antagonists for treatment of vascular disease as well as cancer. Clinical syndromes resulting from mutations in components of the TGF-beta signaling pathway are typified by highly variable penetrance and expressivity. The clinical outcome of individual mutations is very heterogeneous and clearly affected by modifier genes (1, 6). There is therefore much to be learnt concerning cellular and molecular mechanisms regulating in vivo responses to TGF-beta and to TGF-beta inhibitors, which will clearly be of great relevance to future clinical studies.

An integrated molecular and biological approach is warranted because, although the biochemistry of TGF-beta signal transduction has been well characterized in vitro, much remains unresolved concerning functional interactions that occur between this signaling pathway and other biological pathways in vivo. We are using the mouse as an in vivo model together with in vitro systems to study these processes during angiogenesis and tumorigenesis.

The group has made several contributions to understanding the in vivo biology of TGF-beta. These in vivo findings often differ considerably from those predicted from in vitro studies. We provided early evidence of an involvement of TGF-beta1 in chemically-induced skin carcinogenesis (7), and went on to definitively demonstrate the biphasic action of TGF-beta (tumor suppressor/tumor promoter) in tumorigenesis in vivo (8). We definitively demonstrated a role for TGF-beta1 signaling in vascular development in vivo (9, 10), and subsequently showed that the effects of TGF-beta1 action, both in vascular development and tumorigenesis in vivo, are highly dependent on interaction with endogenous variants of other genes (11-14).

We are now utilizing state-of-the-art molecular and genomic technologies to identify and characterize endogenous variant genes that modify a) the phenotypic outcome of Tgf-beta1 nullizygosity (11-13) and b) the action of naturally-occurring variant TGF-beta1 alleles (14-19) in tumorigenesis and vascular development/disease. We have identified three genetic loci that have these properties (Tgfbm1-3) (11-13). Based on fine genetic mapping using congenic mice (13), we have identified a few prime candidate genes for these modifier effects, and detailed functional studies are underway to validate these genes and to determine how they interact with the TGF-beta signaling pathway in vitro and in vivo.  Additionally, we are utilizing our congenic mouse panel to address the role of TGF-beta1 modifier loci in a number of in vivo biological processes, including developmental angiogenesis, post-natal pathological angiogenesis, both non-neoplastic and neoplastic, maintenance of vascular integrity, as well as in overt tumorigenesis.

Whilst maintaining a major interest in the basic molecular mechanisms that regulate angiogenesis both during embryogenesis and tumorigenesis, and in the molecular mechanisms responsible for interaction between the TGF-beta signaling pathway and TGF-beta modifier genes, we are applying this knowledge to clinical studies. We have embarked on human genetic association studies to address the involvement of orthologous modifier genes in human diseases. Namely, how human variants of these genes interact with the TGF-beta1 gene to alter risk for cancer or cardiovascular disease.  Several groups (15-19) have already demonstrated a clear genetic association between functional polymorphisms within the human TGF-beta1 gene and risks for myocardial infarction, hypertension, invasive breast and prostate cancer and diabetic retinopathy (pathological angiogenesis). Utilizing state of the art screens and statistical analysis we are currently testing the role of interactions between human TGF-beta1 and TGFBMs in disease risks for breast cancer, Hereditary Hemorrhagic Telangiectasia and myocardial infarction.

In collaboration with Dr. Ervin Epstein, we are also addressing the role that TGF-beta plays in the highly elevated risk of skin tumorigenesis observed in organ transplant recipients following a few years of anti-rejection drug administration (20-22). This project involves model studies in mice together with analysis of material from organ transplant patients, including genetic association and tissue microarray studies.

Our studies of mouse models and human genetics will give insight, not only to genetically-determined disease risk associated with altered TGF-beta signaling, but the prediction of possible side-effects from anti-TGF-beta therapy.

In conclusion, the lab is taking multiple complementary approaches, including mouse tumorigenesis and developmental biology, mouse and human genetics, together with in vitro cell and molecular analysis, to further an understanding of the role that TGF-beta plays in tumorigenesis and angiogenesis. It is highly likely that TGF-beta inhibitors are going to be successful for certain clinical applications (3, 4), making this area of study highly relevant to translational research.

1. Akhurst, R.J. (2004) TGF beta signaling in health and disease. Nat Genet, 36, 790-2.

2. Derynck, R., Akhurst, R.J. and Balmain, A. (2001) TGF-beta signaling in tumor suppression and cancer progression. Nat Genet, 29, 117-29.

3. Akhurst, R.J. (2006) Large and small molecule inhibitors of TGF beta signaling. Curr Opin Investig Drugs, 7, 513-521.

4. Saunier, E.F. and Akhurst, R.J. (2006) TGFbeta inhibition for cancer therapy. Current Cancer Drug Targets, 6, 519-532.

5. van den Driesche, S., Mummery, C.L. and Westermann, C.J. (2003) Hereditary hemorrhagic telangiectasia: an update on transforming growth factor beta signaling in vasculogenesis and angiogenesis. Cardiovasc Res, 58, 20-31.

6. Harradine, K.A. and Akhurst, R.J. (2006) Mutations of TGFbeta signaling molecules in human disease. Ann Med, 38, 403-14.

7. Akhurst, R.J., Fee, F. and Balmain, A. (1988) Localized production of TGF-beta mRNA in tumour promoter-stimulated mouse epidermis. Nature, 331, 363-5.

8. Cui, W., Fowlis, D.J., Bryson, S., Duffie, E., Ireland, H., Balmain, A. and Akhurst, R.J. (1996) TGFbeta1 inhibits the formation of benign skin tumors, but enhances progression to invasive spindle carcinomas in transgenic mice. Cell, 86, 531-42.

9. Akhurst, R.J., Lehnert, S.A., Faissner, A. and Duffie, E. (1990) TGF beta in murine morphogenetic processes: the early embryo and cardiogenesis. Development, 108, 645-56.

10. Dickson, M.C., Martin, J.S., Cousins, F.M., Kulkarni, A.B., Karlsson, S. and Akhurst, R.J. (1995) Defective haematopoiesis and vasculogenesis in transforming growth factor-beta 1 knock out mice. Development, 121, 1845-54.

11. Bonyadi, M., Rusholme, S.A., Cousins, F.M., Su, H.C., Biron, C.A., Farrall, M. and Akhurst, R.J. (1997) Mapping of a major genetic modifier of embryonic lethality in TGF beta 1 knockout mice. Nat Genet, 15, 207-11.

12. Tang, Y., McKinnon, M.L., Leong, L.M., Rusholme, S.A., Wang, S. and Akhurst, R.J. (2003) Genetic modifiers interact with maternal determinants in vascular development of Tgfb1(-/-) mice. Hum Mol Genet, 12, 1579-89.

13. Tang, Y., Sook Lee, K., Yang, H., Logan, D.W., Wang, S., McKinnon, M.L., Holt, L.J., Condie, A., Luu, M.T. and Akhurst, R.J. (2005) Epistatic interactions between modifier genes confer strain-specific redundancy for Tgfb1 in developmental angiogenesis. Genomics, 85, 60-70.

14. Mao, J.H., Saunier, E.F., de Koning, J.P., McKinnon, M.M., Higgins, M.N., Nicklas, K., Yang, H.T., Balmain, A. and Akhurst, R.J. (2006) Genetic variants of Tgfb1 act as context-dependent modifiers of mouse skin tumor susceptibility. Proc Natl Acad Sci U S A, 103, 8125-30.

15. Cambien, F., Ricard, S., Troesch, A., Mallet, C., Generenaz, L., Evans, A., Arveiler, D., Luc, G., Ruidavets, J.B. and Poirier, O. (1996) Polymorphisms of the transforming growth factor-beta 1 gene in relation to myocardial infarction and blood pressure. The Etude Cas-Temoin de l’Infarctus du Myocarde (ECTIM) Study. Hypertension, 28, 881-7.

16. Yokota, M., Ichihara, S., Lin, T.L., Nakashima, N. and Yamada, Y. (2000) Association of a T29—>C polymorphism of the transforming growth factor-beta1 gene with genetic susceptibility to myocardial infarction in Japanese. Circulation, 101, 2783-7.

17. Beranek, M., Kankova, K., Benes, P., Izakovicova-Holla, L., Znojil, V., Hajek, D., Vlkova, E. and Vacha, J. (2002) Polymorphism R25P in the gene encoding transforming growth factor-beta (TGF-beta1) is a newly identified risk factor for proliferative diabetic retinopathy. Am J Med Genet, 109, 278-83.

18. Dunning, A.M., Ellis, P.D., McBride, S., Kirschenlohr, H.L., Healey, C.S., Kemp, P.R., Luben, R.N., Chang-Claude, J., Mannermaa, A., Kataja, V. et al. (2003) A transforming growth factorbeta1 signal peptide variant increases secretion in vitro and is associated with increased incidence of invasive breast cancer. Cancer Res, 63, 2610-5.

19. Shin, A., Shu, X.O., Cai, Q., Gao, Y.T. and Zheng, W. (2005) Genetic polymorphisms of the transforming growth factor-beta1 gene and breast cancer risk: a possible dual role at different cancer stages. Cancer Epidemiol Biomarkers Prev, 14, 1567-70.

20. London, N.J., Farmery, S.M., Will, E.J., Davison, A.M. and Lodge, J.P. (1995) Risk of neoplasia in renal transplant patients. Lancet, 346, 403-6.

21. Stockfleth, E., Ulrich, C., Meyer, T. and Christophers, E. (2002) Epithelial malignancies in organ transplant patients: clinical presentation and new methods of treatment. Recent Results Cancer Res, 160, 251-8.

22. Hojo, M., Morimoto, T., Maluccio, M., Asano, T., Morimoto, K., Lagman, M., Shimbo, T. and Suthanthiran, M. (1999) Cyclosporine induces cancer progression by a cell-autonomous mechanism. Nature, 397, 530-4.