Platelet-derived growth factor-C (PDGF-C) activation by serine proteases: implications for breast cancer progression.
The PDGF (platelet-derived growth factor) family members are potent mitogens for cells of mesenchymal origin and serve as important regulators of cell migration, survival, apoptosis and transformation. Tumour-derived PDGF ligands are thought to function in both autocrine and paracrine manners, activating receptors on tumour and surrounding stromal cells. PDGF-C and -D are secreted as latent dimers, unlike PDGF-A and -B. Cleavage of the CUB domain from the PDGF-C and -D dimers is required for their biological activity. At present, little is known about the proteolytic processing of PDGF-C, the rate-limiting step in the regulation of PDGF-C activity. In the present study we show that the breast carcinoma cell line MCF7, engineered to overexpress PDGF-C, produces proteases capable of cleaving PDGF-C to its active form. Increased PDGF-C expression enhances cell proliferation, anchorage-independent cell growth and tumour cell motility by autocrine signalling. In addition, MCF7-produced PDGF-C induces fibroblast cell migration in a paracrine manner. Interestingly, PDGF-C enhances tumour cell invasion in the presence of fibroblasts, suggesting a role for tumour-derived PDGF-C in tumour-stromal interactions. In the present study, we identify tPA (tissue plasminogen activator) and matriptase as major proteases for processing of PDGF-C in MCF7 cells. In in vitro studies, we also show that uPA (urokinase-type plasminogen activator) is able to process PDGF-C. Furthermore, by site-directed mutagenesis, we identify the cleavage site for these proteases in PDGF-C. Lastly, we provide evidence suggesting a two-step proteolytic processing of PDGF-C involving creation of a hemidimer, followed by GFD-D (growth factor domain dimer) generation.
Department of Pathology, Barbara Ann Karmanos Cancer Institute, Wayne State School of Medicine, Detroit, MI 48201, USA.
Newton J
NJ
Hurst
Abdo J
AJ
Najy
Carolyn V
CV
Ustach
Lisa
L
Movilla
Hyeong-Reh Choi
HR
Kim
D000818:Animals; D019898:Autocrine Communication / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D018450:Disease Progression; D005260:Female; D006801:Humans; D008222:Lymphokines / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D041681:NIH 3T3 Cells; D019899:Paracrine Communication / Q000235:genetics; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D055503:Protein Multimerization / Q000235:genetics / Q000502:physiology; D011499:Protein Processing, Post-Translational; D057057:Serine Proteases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
D008222:Lymphokines; D010982:Platelet-Derived Growth Factor; C411423:platelet-derived growth factor C; D057057:Serine Proteases