Stromal-epithelial interactions regulate tissue development and homeostasis. In particular, the extracellular matrix, which is the noncellular component of the microenvironment, influences cell growth, survival, migration and tissue-specific differentiation through a repertoire of cellular receptors including integrins, syndecans and discoidin receptors. My group is exploring the molecular mechanisms whereby these extracellular matrix receptors modulate cell fate. Specifically, we are investigating how mechanical and topological properties of the matrix, which are related to its composition and organization, regulate the function of matrix receptors to alter cell behavior. Our research program is broadly divided into two fields of inquiry. The first focuses on understanding how matrix composition and organization influences mammary tissue development and tumor progression, and the second aims to clarify the role of matrix force on embryonic and adult stem cell fate. See below for more detailed description.
1) Clarifying how mechanical forces mediated by the microenvironment in the context of a three dimensional tissue could modulate breast tumor progression and treatment efficacy. To this end we employ three dimensional organotypic culture models, xenograft and syngeneic mouse models, transgenic animals and fresh and fixed clinical samples. These studies are currently focusing on an exploration of collagen cross linking (lysyl oxidase dependent), increased expression, and remodeling (MMPs) and integrins and DDRs.
2) Elaborating the molecular mechanisms whereby matrix stiffness and topology could alter cell fate which include:
2A.) computational studies aimed at modeling the role of matrix and cellular force at the beta 1 integrin extracellular matrix interface;
2B.) signaling studies focused on dissecting the role of matrix dimensionality and tissue polarity on laminin ligated alpha 6 beta 4 integrins ability to signal through rac and arf6 to activate NFkappa B and enhance survival and apoptosis resistance in mammary epithelial cells and tissues;
2C.) studies exploring the role of matrix composition and force on chromatin remodeling including SMRT-dependent apoptosis resistance through alpha 6/beta 4 integrin to NFkappa B dependent gene transcription;
2D.) studies examining the Swi/Snf Brm and alpha 5 integrin/fibronectin functional interactions in mammary epithelial cell migration and survival using organotypic culture assays and a Brm knockout mouse;
2E.) studies exploring links between matrix stiffness (force), methylation and breast cell survival using primary human mammary cell cultures and matrices with tuned visco elasticities;
2F.) a project exploring functional links between matrix stiffness, micro RNAs and HoxA9 dependent regulation of BRCA1 and mammary cell survival and tumorigenesis - using organotypic culture models, a HoxA9 knockout and xenograft manipulations;
2G.) a project exploring how matrix force influences mammary cells morphogenesis and tumor progression through effects on protein tyrosine phosphatases - with a focus on PTP-PEST and PTP-Meg1.
3) Characterizing the role of and molecular mechanisms whereby mechanical force could regulate human embryonic stem cell fate using two and three dimensional matrices with calibrated stiffness and exerting acute forces on ES cells embedded within defined natural and synthetic matrices using a force reactor. These studies will elaborate on mechanisms identified using the human mammary epithelial cells including effects of force on DNA methylation, homeobox gene expression and function, and Brm.
Rotation Projects currently available at the Weaver Lab:
1. The role of matrix force on breast tumor progression using collagen mutant mice and organotypic culture assays.
2. The role of matrix force on SMRT-dependent chromatin remodeling and alpha 6/beta 4 integrin-dependent apoptosis resistance using organotypic culture assays and a force reactor.
3. The role of matrix force and topology on breast tumor invasion and metastasis with a focus on the role of beta 4 integrin and Arf6 signaling and durotaxis.
4. Effects of matrix stiffness on micro RNA expression and function using 2D and 3D matrices with calibrated mechanical properties.
Friedland JC, Lakins JN, Kazanietz MG, Chernoff J, Boettiger D, Weaver VM, "alpha6beta4 integrin activates Rac-dependent p21-activated kinase 1 to drive NF-kappaB-dependent resistance to apoptosis in 3D mammary acini", J Cell Sci, October, 2007, 120:20:3700-3712
Lakins JN, Chin AR, Weaver VM. Exploring the link between human embryonic stem cell organization and fate using tension-calibrated extracellular matrix functionalized polyacrylamide gels. Methods Mol Biol. 2012;916:317-50
Levental KR, Yu H, Kass L, Lakins JN, Egeblad M, Erler JT, Fong SF, Csiszar K, Giaccia A, Weninger W, Yamauchi M, Gasser DL, Weaver VM. Matrix crosslinking forces tumor progression by enhancing integrin signaling. Cell. 2009 Nov 25;139(5):891-906.
Paszek MJ, Zahir N, Johnson KR, Lakins JN, Rozenberg GI, Gefen A, Reinhart-King CA, Margulies SS, Dembo M, Boettiger D, Hammer DA, Weaver VM. Tensional homeostasis and the malignant phenotype. Cancer Cell, 2005, 8:3:241-254
Rizki A, Weaver VM, Lee SY, Rozenberg GI, Chin K, Myers CA, Bascom JL, Mott JD, Semeiks JR, Grate LR, Mian IS, Borowsky AD, Jensen RA, Idowu MO, Chen F, Chen DJ, Petersen OW, Gray JW, Bissell MJ, A human breast cell model of preinvasive to invasive transition. Cancer Research, March 2008, 68:5:1378-87
Weaver, VM, Lelievre, S., Lakins, JN., Chrenek, M., Jones, J., Giancotti, F., Werb, Z., and Bissell,MJ, Beta 4 integrin-dependent formation of polarized three-dimentional architecture confers resistance to apoptosis in normal and malignant mammary epithelium. Cancer Cell, 2002, 205-216
Zahir N, Lakins JN, Russell A, Ming W, Chatterjee C, Rozenberg GI, Marinkovich MP, Weaver VM, Autocrine laminin-5 ligates alpha6beta4 integrin and activates RAC and NFkappaB to mediate anchorage-independent survival of mammary tumors. J Cell Bio, 2003, 163:6:1397-1407