Characterization of Matrix Metalloprotease 1a in Tumorigenesis.
metalloproteases (MMPs) are a family of extracellular proteases that allow cells to both
sense and remodel their extracellular environment through cleavage of cell surface
receptors, secreted factors and matrix proteins. While proteolytic activity of MMPs is
required for normal tissue homeostasis and other physiologic processes, many
pathophysiologic conditions are associated... read morewith dysregulated MMP activity. While some
diversity exists between vertebrate MMPs, animal models have been extensively utilized
to characterize MMP signaling in disease. However, the study of MMP1, a tumorigenic
collagenase and activator of protease activated receptor 1 (PAR1), has been limited in
animal models due to uncertainty as to whether mouse MMP1 is functionally equivalent to
human MMP1. In rodents, gene duplication has created to two potential MMP1 homologues,
Mmp1a and Mmp1b. Mmp1b lacks enzymatic activity, suggesting that Mmp1a is the MMP1
homologue in tumorigenesis models. Mouse-derived lung cancer and melanoma cells
expressed high levels of Mmp1a. Mmp1a expression promoted PAR1-driven collagen invasion
and stellate growth in three-dimensional culture. Silencing of Mmp1a reduced in vivo
tumorigenesis, invasion, and metastasis of mouse lung cancer cells, consistent with
Mmp1a acting as an MMP1-like activity in tumor models. To better understand the
functions of Mmp1a in vivo, Mmp1a-deficient animals were generated. Mmp1a-/- animals are
healthy and fertile. Tumor growth and angiogenesis was reduced in Mmp1a-/- mice. This
phenotype was present despite cancer cell Mmp1a expression and could be rescued by
co-implantation of Mmp1a+/+ fibroblasts, highlighting the importance of stromal Mmp1a.
Despite homologous MMP1-like functions in tumorigenesis models, Mmp1a expression was
less than MMP1 in quiescent tissues. Mammalian expression systems revealed a severe
defect in production of mature Mmp1a but not MMP1 protein. This defect was caused by
instability of the Mmp1a prodomain, partially due to a phenylalanine to leucine
prodomain substitution that interfaces with the catalytic domain. Together, these
results demonstrate that Mmp1a is a relevant homologue for MMP1 in tumorigenesis models
but also highlight key biochemical differences between MMP1 and Mmp1a that require
further exploration for the development of relevant MMP1 mouse models of human
Thesis (Ph.D.)--Tufts University, 2014.
Submitted to the Dept. of Genetics.
Advisor: Athan Kuliopulos.
Committee: Alain Charest, Phil Hinds, and Peter Brodeur.
Keyword: Genetics.read less