title: Tumor cell and connective tissue cell interactions in human colorectal adenocarcinoma. Transfer of platelet-derived growth factor-AB/BB to stromal cells.
abstract: Mechanisms underlying stimulation of platelet-derived growth factor (PDGF) beta-receptors expressed on connective tissue cells in human colorectal adenocarcinoma were investigated in this study. PDGF-AB/BB, but not PDGF receptors, was expressed by tumor cells in situ, as well as in tumor cell isolates of low passage from human colorectal adenocarcinoma. In an experimental co-culture system, conditioned medium from tumor cells only marginally activated PDGF beta-receptors expressed on fibroblasts. In contrast, co-culturing of the two cell types led to a marked PDGF beta-receptor activation. Functional PDGF-AB/BB was found to be associated with heparinase-I-sensitive components on the tumor cell surface. PDGF-AB/BB, isolated from heparinase-I-sensitive cell surface components, induced a marked activation of PDGF beta-receptors. Furthermore, co-culturing tumor cells together with fibroblasts led to a sustained activation of PDGF beta-receptors expressed on fibroblasts. Double immunofluorescence staining of tissue sections from human colorectal adenocarcinoma, combined with computer-aided image analysis, revealed that nonproliferating tumor cells were the predominant cellular source of PDGF-AB/BB in the tumor stroma. In addition, PDGF-AB/BB-expressing tumor cells were found juxtapositioned to microvascular cells expressing activated PDGF beta-receptors. Confocal microscopy revealed a cytoplasmic and cell-membrane-associated expression of PDGF-AB/BB in tumor cells situated in the stroma. In contrast, epithelial cells situated in normal or tumorous acinar structures revealed only a cell-membrane-associated PDGF-AB/BB expression. The is vitro and in situ results demonstrate that tumor cells not only facilitate but also have the ability to modulate connective tissue cell responsiveness to PDGF-AB/BB in a paracrine fashion, through direct cell-cell interactions in human colorectal adenocarcinoma.
authors.affiliation: Department of Medical and Physiological Chemistry, University Hospital, Uppsala, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Sundberg
authors.forename: M
authors.initials: M
authors.lastname: Branting
authors.forename: B
authors.initials: B
authors.lastname: Gerdin
authors.forename: K
authors.initials: K
authors.lastname: Rubin
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D002450:Cell Communication; D018920:Coculture Techniques; D015179:Colorectal Neoplasms / Q000378:metabolism / Q000473:pathology*; D017077:Culture Media, Conditioned; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015151:Immunoblotting; D007150:Immunohistochemistry; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D017154:Stromal Cells / Q000378:metabolism / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D017077:Culture Media, Conditioned; D010982:Platelet-Derived Growth Factor