The expression of the molecular chaperone calnexin is decreased in cancer cells grown as colonies compared to monolayer

Differential display was used to identify genes which were differentially expressed when HT-29 human colon adenocarcinoma cells were grown as monolayers attached to plastic or as colonies in soft agarose. One of the gel bands differentially displayed corresponded to a 171 bp fragment that showed 99% identity with a sequence of mRNA for human calnexin. The decrease in calnexin gene expression by HT-29 cells growing as colonies in soft agarose was confirmed by reverse transcriptase-PCR (RT-PCR) using calnexin-specific primers. We also used RT-PCR to show that the expression of calnexin was decreased in HT-29 cells and MCF-7 human breast adenocarcinoma cells growing in suspension in poly(hydroxyethyl methacrylate)-coated wells compared to cells growing as monolayers. The results suggest that there is a signal for the up-regulation of calnexin expression when cells contact a substrate which allows cell adhesion.