Different adhesion properties of highly and poorly metastatic HT-29 colon carcinoma cells with extracellular matrix components: role of integrin expression and cytoskeletal components

Integrin-mediated tumour cell adhesion to extracellular matrix (ECM) compon ents is an important step in the development of metastatic lesions. Thus, i ntegrin expression and integrin-mediated adhesion of colon carcinoma cells to various ECM components was examined. Poorly (HT-29P) and highly (HT-29LM M) liver-metastatic colon carcinoma cells were used to study the rates of a dhesion to collagen I (C I), collagen IV (C IV), laminin (LN), fibronectin (FN), or vitronectin (VN) in a static adhesion assay (10-120 min). Cells we re untreated or treated with oligopeptides (RGD, GRGDS, YIGSR, RGES), anti- integrin antibodies, or colchicine, nocodazole, cycloheximide, acrylamide o r cytochalasin D (to disrupt cytoskeletal structures). Both cell lines expr essed similar patterns of integrin expression (alpha(2), alpha(3), alpha(6) , alpha(v), beta(1), beta(4) and beta(5)) by immunocytochemistry and immuno precipitation. HT-29LMM cells showed significantly higher rates of adhesion to LN (P < 0.001) and FN (P < 0.001), but significantly poorer rates of ad hesion to C I (P < 0.05) and C IV (P < 0.001) than HT-29P cells, respective ly, adhesion to VN was insignificant. RGD and GRGDS inhibited HT-29LMM cell adhesion to FN only. Pretreatment with anti-beta(1) or anti-alpha(2) integ rin subunits suppressed adhesion to C I and C IV, and adhesion to LN was in hibited with anti-beta(1) or anti-alpha(6) integrin. Anti-beta(1) or anti-a lpha(v) blocked adhesion to FN. Pretreatment of cells with cytochalasin D, cycloheximide or acrylamide inhibited adhesive interactions of both cell li nes to the ECM components. In contrast, colchicine and nocodazole had no ef fect. The results demonstrate that adhesion of HT-29 cells to ECM is mediat ed, in part, by different integrins, depending on the substrate. Poorly and highly metastatic HT-29 cells possessed different patterns of adhesion to the various ECM substrates, but these differences were not due to different expression of integrin subunits. The results also suggested that the initi al adhesion of poorly or highly metastatic HT-29 cells to ECM components re quires, in part, the presence of native action and intermediate filaments, but not of microtubules. Thus the adhesion of tumour cells to ECM component s may be dependent on signal transduction and assembly of microfilaments.