Growth factor regulation of gene expression.
Alterations in proto-oncogenes and tumor suppressor genes drive tumor cell growth and progression. The normal versions of these genes are also often regulated to control cancer or normal cell growth and differentiation. I have been interested in understanding how these genes are regulated both in oncogenesis and in normal cellular growth control. These genes are parts of cellular signaling pathways where many of the pathway components can be altered in cancer.
We have investigated these cellular signaling pathways that control cell growth by studying one of the earliest steps. Quiescent cells can be induced to divide by treatment with growth factors. One of the first consequences is induction of gene expression of a class of genes called cellular immediate early genes (IEGs). A paradigm of these immediate early genes is the proto-oncogene c-fos. Transcriptional activation of c-fos is mediated by a sequence element in its promoter, the Serum Response Element (SRE). A specific transcription factor, Serum Response Factor (SRF), binds the SRE and is required for expression of many IEGs.
SRF is activated by two signaling pathways. One is MAP kinase phosphorylation of the SRF cofactors, the ternary complex factors (TCFs), and the second is signaling through the small GTPase RhoA. The RhoA pathway works through the myocardin-related family of SRF coactivators (MKL1 and MKL2). The RhoA pathway causes changes in the actin cytoskeleton of the cell and changes in actin filaments directly control activation of MKL1 and MKL2.
MKL1 was originally identified at a translocation breakpoint in megakaryoblastic leukemia. Activation of MKL1 and of SRF target genes is likely responsible for this leukemia. The role of this pathway in cancer is further shown by studies of the Rho family which show a role in cancer metastasis and of an inhibitor of RhoA, Deleted in Liver Cancer 1 (DLC1), which is thought to be a tumor suppressor for many types of cancer. Loss or repression of DLC1 can cause activation of RhoA and subsequently MKL1 and SRF. We are interested in how DLC1 is regulated and how its activation of MKL1/SRF promotes cancer growth and metastasis.
Another step where cancer cell progression is regulated is the transition from a benign to a metastatic tumor. One mechanism for metastatic progression we are studying is the epithelial to mesenchymal transition (EMT) in breast epithelial cells. EMT is a differentiation step that can allow cancer cells to break their epithelial cell-cell contacts and be more invasive. We have studied this through regulation of the p53-related gene, p63. p63 acts as a master regulator of the epithelial state and its expression is strongly repressed during EMT. We have found that certain oncogenes can repress p63 expression and induce EMT. We are studying how p63 expression is regulated in this process. Blocking this repression should inhibit cancer progression where it is dependent upon EMT.
- Yoh, K. and Prywes, R. (2015). Pathway regulation of p63, a director of epithelial cell fate. Frontiers in Endocrinology. In press.
- Henckels, E. and Prywes, R. (2013). Fra-1 regulation of Matrix Metallopeptidase-1 (MMP-1) in metastatic variants of MDA-MB-231 breast cancer cells. F1000Research, 2:229 (doi: 10.12688/f1000research.2-229.v1) Article
- Lewis, T. and Prywes, R. (2013). Serum regulation of Id1 expression by a BMP pathway and BMP responsive elements. Bioch. Biophys. Acta-Gene Regulatory Mechanisms. 1829(10):1147-1159. Article
- Hampl, V., Martin, C., Aigner, A., Frank, N., Prywes, R., Gudermann, T., and Muehlich, S. (2013). Depletion of the transcriptional coactivators megakaryoblastic leukaemia 1 and 2 abolishes hepatocellular carcinoma xenograft growth by inducing oncogene-induced senescence. EMBO Mol Med. 5(9):1367-82. Article
- Muehlich, S., Hampl, V., Khalid, S., Singer, S., Frank, N., Breuhahn, K., Gudermann T., and Prywes, R. (2012). The transcriptional coactivators MKL1/2 mediate the effects of loss of the tumor suppressor DLC1. Oncogene. 31(35):3913-23. Article
- Lee, S.M., Vasishtha, M. and Prywes, R. (2010) Activation and repression of cellular immediate early genes by SRF cofactors. J Biol Chem. Epub ahead of print: 2010 May 12. Article
- Muehlich, S., Wang, R., Lee, S.M., Lewis, T.C., Dai C. and Prywes, R. (2008) Serum-induced phosphorylation of the SRF coactivator MKL1 by the ERK1/2 pathway inhibits its nuclear localization Mol. Cell. Biol. 28(20): 6302-13. Article
- Shen, J., Snapp, E.L., Lippincott-Schwartz, J. and Prywes, R (2005) Stable binding of ATF6 to BiP in the ER stress response Mol. Cell. Biol 25(3): 921-32. Article
- Shen, J. and Prywes, R. (2005) ER stress signaling by regulated proteolysis of ATF6. Methods 35(4): 382-9. Article
- Selvaraj, A. and Prywes, R. (2004) Expression profiling of serum inducible genes identifies a subset of SRF target genes that are MKL dependent. BMC Mol. Biol 5(1): 13. Article
- Shen, J. and Prywes, R. (2004) Dependence of site-2 protease cleavage of ATF6 on prior site-1 protease digestion is determined by the size of ATF6's lumenal domain J. Biol. Chem 279(41): 43046-51. Article
- Cen, B., Selvaraj, and Prywes, R. (2004) The Myocardin/MKL family of SRF coactivators: key regulators of immediate early and muscle specific gene expression J. Cell. Biochem 93(1): 74-82. Article
- Selvaraj, A. and Prywes, R. (2003) Megakaryoblastic Leukemia-1/2, a transcriptional co-activator of SRF, is required for skeletal myogenic differentiation J. Biol. Chem. 278(43): 41977-87. Article
- Cen, B., Selvaraj, A., Burgess, R.C., Hitzler, J.K., Ma, Z., Morris, S.W. and Prywes, R. (2003) Megakaryoblastic Leukemia-1, a potent transcriptional coactivator for Serum Response Factor, is required for serum induction of SRF target genes Mol. Cell. Biol. 23: 6597-6608. Article