Partial Characterization of A Glucocorticoid Suppressible Mitogenic Activity Secreted from a Rat Hepatoma Cell Line Hypersensitive to the Antiproliferative Effects of Glucocorticoids

FKBP51 expressed by both normal epithelial cells and adenocarcinoma of colon suppresses proliferation of colorectal adenocarcinoma

It has been reported, as a result of Western blot analyses, that FKBP51 is expressed in various tissues, but that it is not expressed in the pancreas, lung, colon, stomach, or spleen. In this paper, we show, using Western blot analyses, reverse transcriptase polymerase chain reaction, and immunohistochemical analyses of samples from colon cancer patients, that both normal epithelial cells and adenocarcinoma in the human colon express FKBP51, and that there are no significant differences in the expressions of FKBP51 between them. We also show that FKBP51 suppresses the proliferation of colorectal adenocarcinoma, possibly due to the suppression of functions of the glucocorticoid receptors.

In vivo effects of dexamethasone on the tumor growth of glucocorticoid-sensitive Fu5-derived rat hepatoma cells

We have previously demonstrated that BDS.1 cells are a minimal deviation rat hepatoma cell line that is hypersensitive to the anti-proliferative effects of glucocorticoids in vitro. When transplanted into athymic mice, exposure to dexamethasone reduced the initial growth rate and increased the latency time before detection of palpable BDS.1-derived tumors but did not affect the maximal growth rate, size and histology of the tumor. After collagenase dissociation, the in vitro growth of BDS.1-derived tumor cells was fully suppressed by dexamethasone. Exposure to insulin prevented the glucocorticoid inhibition of anchorage-independent growth of BDS.1 cell colonies in vitro and may therefore be one of the systemic factors that masks the long term in vivo growth response of glucocorticoids.

Glucocorticoid effects and receptors in two rat colon carcinoma cell lines differing by their tumorigenicity

Steroid hormones, regulators of cell differentiation and proliferation, are believed to play a role in carcinogenesis. Glucocorticoid hormones in particular modulate the expression of a number of proteins implicated in this process. We have investigated the effect of dexamethasone on two cell lines derived from a colon carcinoma, which differ by their tumorigenicity. Dexamethasone was found to inhibit growth of both the progressive (PROb) and the regressive clone (REGb). Upon hormonal treatment, glucocorticoid hormones induced fibronectin secretion by the two clones, whereas PROb cells were found to secrete an additional Mr approximately 43,000 protein. The cellular effect of glucocorticoid hormones being mediated through a specific soluble receptor, we have characterized this protein. The progressive cells (PROb) contained more specific glucocorticoid-binding sites (approximately 170,000 sites per cell) than the regressive ones (REGb cells; approximately 100,000 sites per cell). In both clones, the receptor was associated with the Mr approximately 90,000 heat shock protein to yield large complexes (Stokes radius Rs approximately 7.5 nm), which were dissociated to the same extent upon heat- and salt-treatment. The steroid- and DNA-binding unit of the receptor, characterized under denaturing conditions using an anti-receptor monoclonal antibody was found to be more degraded in the progressive cell line.