Distinct roles of osteopontin in host defense activity and tumor survival during squamous cell carcinoma progression in vivo.
Secreted phosphoprotein 1 (spp1), the gene encoding osteopontin (OPN), is expressed in many human carcinomas, although its in vivo functions remain unclear. To delineate the role of OPN during tumor progression, we have subjected OPN null mutant mice to repeated applications of a mutagen/carcinogen to induce cutaneous squamous cell carcinoma. OPN null animals exhibited accelerated tumor growth and progression and had a greater number of metastases per animal compared with wild-type animals. However, metastases in the OPN null animals were significantly smaller than in controls. When injected into nude mice, the growth of OPN null tumor lines and the same lines engineered to reexpress spp1 recapitulated the growth differences observed in the progression study. These differences in tumor growth inversely correlated with the degree of macrophage infiltration. Slower-growing, OPN-producing tumors contained significantly more macrophages, although a higher proportion were mannose receptor positive, a characteristic of differentiated resting macrophages. In vitro, OPN null cell lines displayed decreased survival at clonal density compared with OPN-producing lines, an observation consistent with the smaller metastases of the OPN null mice. Overall, we provide evidence for a model where host-derived OPN acts as a macrophage chemoattractant, whereas tumor-derived OPN is able to inhibit macrophage function and enhances the growth or survival of metastases.
Crawford
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HC
Department of Cell Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Matrisian
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LM
Liaw
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D000818:Animals; D002273:Carcinogens; D002277:Carcinoma / Q000139:chemically induced / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D002294:Carcinoma, Squamous Cell / Q000139:chemically induced / Q000276:immunology / Q000378:metabolism* / Q000556:secondary; D002452:Cell Count; D002455:Cell Division; D018450:Disease Progression; D005260:Female; D008297:Male; D008769:Methylnitronitrosoguanidine; D051379:Mice; D009363:Neoplasm Proteins / Q000502:physiology*; D053495:Osteopontin; D010212:Papilloma / Q000139:chemically induced / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D010641:Phenotype; D012795:Sialoglycoproteins / Q000502:physiology*; D012878:Skin Neoplasms / Q000139:chemically induced / Q000276:immunology / Q000378:metabolism* / Q000473:pathology
D002273:Carcinogens; D009363:Neoplasm Proteins; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; D053495:Osteopontin; D008769:Methylnitronitrosoguanidine