Development of intracytoplasmic lumens in colon cancer cells cultured on non-adhesive surface

Cell-matrix interactions have important effects on phenotypic features, suc h as morphology, differentiation and cell growth. Several papers have sugge sted that when cell-matrix interaction is interrupted, cells grow as multic ellular spheroids and eventually undergo apoptosis. We found that when ET(- ), a laminin non-adherent colon cancer cell line, was cultured on poly-2-hy droxyethyl methacrylate (HEMA) coated plastic, the cells floated as cellula r aggregates of spheroids or as single cells. Some of the single cells cont ained large intracytoplasmic lumens (ICL) and appeared similar to signer ri ng cells. These ICL were lined by a layer of short microvilli. The number o f the cell did not increase when cultured on poly-HEMA. Another type of sin gle cells, usually without ICL, demonstrated the characteristics of apoptot ic cells by histologic examination. Acridine orange staining, flow cytometr y and electron microscopy confirmed the apoptotic nature of those cells. On immunohistochemical staining for proliferating cell nuclear antigen, spher oids of cells and single cells with ICL were immunoreactive, while most of the single cells without ICL were negative. These results suggest that mult icellular aggregates and formation of ICL were induced by the adaptation of ET(-) colon cancer cells in a harmful environment caused by reduced adhesi veness, and these changes might be related to cell survival.