RESUMEN
<p><b>OBJECTIVE</b>To imitate tumor microenvironment in vivo through construction of two-layer cell spheroid as a three-dimensional tumor model, and to validate its application in the study of Cx43 expression in colorectal cancer cell-fibroblast interactions and colorectal cancer progression.</p><p><b>METHODS</b>The two-layer cell spheroid was constructed from SW620 colorectal cancer cells and HELF fibroblasts. The expression of Cx43 in the spheroid was detected by immunocytochemistry. The expression of Cx43 in cultured SW620 cells with or without co-cultured fibroblasts was detected by immunocytochemistry and immunofluorescence. The expression of Cx43 in colorectal cancer tissue was detected by immunohistochemistry.</p><p><b>RESULTS</b>The spheroid showed well-defined cellular morphology and clear boundary between two cell lines.Significant expression of Cx43 was found along the boundary.SW620 cells had no expression of Cx43 when cultured alone, while the expression of Cx43 was induced upon co-culturing with fibroblasts.In the colorectal cancer tissue, expression of Cx43 was minimal in the centre of tumor in contrast to an upregulated expression at invasive front.</p><p><b>CONCLUSIONS</b>The two-layer cell spheroid is an observable and sensitive model for cell-cell interaction for studies of tumor microenvironment.It can simulate colorectal cancer cell-fibroblast interactions through up-regulation of Cx43 expression.</p>