Beta1 integrin cytoplasmic variants differentially regulate expression of the antiangiogenic extracellular matrix protein thrombospondin 1.
Beta(1) integrins play an important role in regulating cell proliferation and survival. Using small interfering RNA or an inhibitory antibody to beta(1), we show here that, in vivo, beta(1) integrins are essential for prostate cancer growth. Among the five known beta(1) integrin cytoplasmic variants, two have been shown to differentially affect prostate cell functions. The beta(1A) variant promotes normal and cancer cell proliferation, whereas the beta(1C) variant, which is down-regulated in prostate cancer, inhibits tumor growth and appears to have a dominant effect on beta(1A). To investigate the mechanism by which beta(1C) inhibits the tumorigenic potential of beta(1A), we analyzed changes in gene expression in cells transfected with either beta(1C) or beta(1A). The results show that beta(1C) expression increases the levels of an extracellular matrix protein, thrombospondin 1 (TSP1), an angiogenesis inhibitor. TSP1 protein levels are increased upon beta(1C) expression in prostate cancer cells as well as in beta(1)-null GD25 cells. We show that TSP1 does not affect proliferation, apoptosis, or anchorage-independent growth of prostate cancer cells. In contrast, the newly synthesized TSP1, secreted by prostate cancer cells expressing beta(1C), prevents proliferation of endothelial cells. In conclusion, our novel findings indicate that expression of the beta(1C) integrin variant in prostate glands prevents cancer progression by up-regulation of TSP1 levels and inhibition of angiogenesis.
Goel
Hira Lal
HL
Department of Cancer Biology, Prostate Cancer Discovery and Development Program, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
Moro
Loredana
L
Murphy-Ullrich
Joanne E
JE
Hsieh
Chung-Cheng
CC
Wu
Chin-Lee
CL
Jiang
Zhong
Z
Languino
Lucia R
LR
D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D042783:Endothelial Cells / Q000166:cytology / Q000473:pathology; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D014644:Genetic Variation; D006801:Humans; D019012:Integrin beta1 / Q000235:genetics*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009389:Neovascularization, Pathologic / Q000517:prevention & control; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics / Q000473:pathology; D034741:RNA, Small Interfering / Q000235:genetics; D019700:Thrombospondin 1 / Q000235:genetics*; D014162:Transfection; D014471:Umbilical Veins
D016326:Extracellular Matrix Proteins; D019012:Integrin beta1; D034741:RNA, Small Interfering; D019700:Thrombospondin 1