C. Michael DiPersio
Integrins are the major family of receptors for cell adhesion to the extracellular matrix (ECM). The DiPersio lab investigates how integrins regulate epithelial cell functions that govern tissue remodeling, and how changes in this regulation contribute to cancer progression and pathological wound healing. We use a variety of genetic, cell biological, and genomic approaches to investigate the mechanisms through which the laminin-binding integrin, α3β1, regulates ECM assembly/remodeling, cell migration/invasion, and paracrine stimulation of angiogenesis. Our long-term goal is to develop therapeutic strategies that target α3β1, or its effectors, to inhibit cancer progression and metastasis or treat pathological wound healing.
Current areas of investigation:
I. Roles of epidermal integrins in cutaneous wound healing. To exploit integrins as therapeutic targets to treat wounds, we need to better understand how different integrins within the epidermis function in a coordinated manner. Our lab, in collaboration with Dr. Livingston Van De Water in our Center, has developed integrin knockout mice and mouse keratinocyte (MK) cell lines to investigate the combinatorial roles of two epidermal integrins, α3β1 and α9β1, in cutaneous wound healing. Using these models, we determined that α3β1 is essential in the epidermis of healing wounds for proper ECM assembly and paracrine stimulation of endothelial cells/angiogenesis, and that these functions occur through α3β1-dependent expression of keratinocyte genes involved in tissue remodeling, including fibulin-2 (a matricellular protein) and mitogen-regulated protein 3 (MRP3, a pro-angiogenic growth factor). Moreover, α9β1 suppresses these functions of α3β1, suggesting that α9β1 acts as a temporally regulated “brake” on α3β1 at later stages of wound healing when ECM assembly is complete and angiogenesis is no longer required. We have recently initiated studies to determine whether the coordinated functions of α9β1 and α3β1 in the epidermis similarly regulate paracrine crosstalk to fibroblasts/myofibroblasts, the cells responsible for scarring. For these studies, we have adapted an in vivo model of mechanically induced scar formation to our genetic models of integrin knockout. These studies may lead to therapeutic strategies for targeting integrins α9β1 and α3β1 to treat chronic wounds or prevent hypertrophic scars.
II. Roles for integrin α3β1 in regulating cancer gene expression through mRNA processing and stability. A major focus of our research is determining molecular pathways through which integrin α3β1 regulates genes that drive cancer progression and metastasis. Post-transcriptional mRNA processing and stability are emerging as major modes of gene regulation in cancer, yet little is known about how signals from the tumor microenvironment are transmitted into tumor cells to control these processes. Using two different models, we discovered that α3β1 promotes the expression of two pro-tumorigenic/pro-angiogenic genes, cyclooxygenase-2 (COX-2/PTGS2) and matrix metalloproteinase-9 (MMP-9), by controlling alternative mRNA processing that determines susceptibility to mRNA degradation pathways. In the first model, use of RNA interference (RNAi) to suppress α3β1 in breast cancer cells leads to alternative splicing of COX-2 mRNA, thereby causing retention of an intron that harbors premature termination codons (PTCs) and targets the mRNA transcript for nonsense-mediated decay (NMD). In the second model, genetic deletion of α3β1 in immortalized keratinocytes leads to use of an alternative downstream polyadenylation site in the MMP-9 gene, thereby generating an extended 3’-untranslated region that encompasses several AU-rich elements (AREs) and destabilizes the mRNA transcript. A common theme in both models is that α3β1 maintains expression of COX-2 or MMP-9 by promoting the exclusion of regulatory elements from the mRNA transcript that would otherwise target it for degradation by NMD or ARE-mediated pathways. Global exon profiling of breast cancer cells revealed that α3β1-dependent mRNA splicing or polyadenylation extends to many other genes. Current efforts are focused on developing minigene splice reporters and high-throughput cDNA and RNAi screens to identify α3β1-dependent trans-regulators of mRNA spicing in cancer cells. We are coupling these approaches with in vivo tumor models to investigate the importance of these pathways in cancer progression and metastasis, towards our long-term goal of exploiting integrin-dependent mRNA splicing pathways as therapeutic targets.
- Missan DS, Mitchell K, Subbaram S, DiPersio CM. Integrin alpha3/beta1 signaling through MEK/ERK determines alternative polyadenylation of the MMP-9 mRNA transcript in immortalized mouse keratinocytes. PLoS One 10(3):e0119539, 2015.
- Missan DS, Chittur SV, DiPersio CM. Regulation of fibulin-2 gene expression by integrin alpha3/beta1 contributes to the invasive phenotype of transformed keratinocytes. J Invest Dermatol 134(9):2418-2427, 2014.
- Longmate WM, Monichan R, Tsuda T, Chu M-L, Mahoney MG, DiPersio CM: Reduced fibulin-2 contributes to loss of basement membrane integrity and skin blistering in mice lacking integrin alpha3/beta1 in the epidermis. J Invest Dermatol 134(6):1609-1617, 2014.
- Longmate WM, DiPersio CM: Integrin regulation of epidermal functions in wounds. Adv Wound Care 3(3):229-246, 2014.
- Aggarwal A, Al-Rohil RN, Batra A, Feustel PJ, Jones DM, DiPersio CM. Expression of integrin alpha3/beta1 and cyclooxygenase-2 (Cox-2) are positively correlated in human breast cancer. BMC Cancer 14:459, 2014.
- Subbaram S, Lyons SP, Svenson KB, Hammond SL, Craig L, Chittur SV, DiPersio CM: Integrin alpha3/beta1 controls mRNA splicing that determines Cox-2 mRNA stability in breast cancer cells. J Cell Sci 127:1179-1189.
- Subbaram S, DiPersio CM: Integrin alpha3/beta1 as a breast cancer target. Expert Opinion on Therapeutic Targets 15(10):1197-1210, 2011.
- Mitchell K, Svenson KB, Longmate WM, Gkirtzimanaki K, Sadej R, Wang X, Zhao J, Eliopoulos AG, Berditchevski F, DiPersio CM: Suppression of integrin alpha3/beta1 in breast cancer cells reduces Cyclooxygenase-2 gene expression and inhibits tumorigenesis, invasion, and crosstalk to endothelial cells. Cancer Res 70:6359-6357, 2010.
- Mitchell K, Szekeres C, Milano V, Svenson KB, Nilsen-Hamilton, M, Kreidberg J, DiPersio CM: Alpha3/beta1 integrin in epidermis promotes wound angiogenesis and keratinocyte-to-endothelial cell crosstalk through induction of MRP3. J Cell Sci 122(11):1778-1787, 2009.
- Lamar J, Pumiglia K, DiPersio CM: An immortalization-dependent switch in integrin function upregulates MMP-9 to enhance tumor cell invasion. Cancer Res 68:7371-7379, 2008.