Development of intracytoplasmic lumens in a colon cancer cell line cultured on a non-adhesive surface.

Cell-matrix interactions have important effects on phenotypic features, such as morphology, differentiation and cell growth. Several papers have suggested that when cell-matrix interactions are interrupted, cells grow as multicellular spheroids and eventually undergo apoptosis. We found that when ET(-), a laminin non-adherent colon cancer cell line, was cultured on poly-2-hydroxyethyl methacrylate (HEMA) coated plastic, the cells floated as cellular aggregates of spheroids or as single cells. Some of the single cells contained a very large intracytoplasmic lumen (ICL) and appeared similar to signet ring cells. These ICL were lined by a layer of short microvilli. The number of the cell did not increased cells when cultured on poly-HEMA. Another type of single cells, usually without ICL, demonstrated the characteristics of apoptotic cells by histologic examination. Acridine orange staining, flow cytometry and electron microscopy confirmed the apoptotic nature of those cells. In immunohistochemical staining for proliferating cell nuclear antigen, spheroids of cells and single cells with ICL were immunoreactive, while most of the single cells without ICL were negative. These results suggest that multicellular aggregation and formation of ICL were induced by the adaptation of ET(-) colon cancer cells in a harmful environment caused by reduced adhesiveness, and these changes might be related to cell survival.