Nonactivated and activated glucocorticoid receptor complexes from human salivary gland adenocarcinoma cell line

Retinoic acid receptor in subclone of human salivary gland adenocarcinoma cell line HSG and effect of retinoic acid on cellular growth

Retinoic acid (RA) binding has been detected in the nuclei of a subclone (CL-1) of human submandibular adenocarcinoma cell line HSG conditioned to grow in a serum-free defined medium. Competition assay confirmed the specificity of the RA binding. Scatchard analysis showed the binding molecule to have a high affinity and low capacity. From the analyses by gel-filtration and glycerol density gradient centrifugation, the nuclear binding molecule appears to be distinct from cellular RA binding protein (CRABP) in terms of molecular weight. Furthermore, immunoblotting analysis revealed a band (Mr 47,000) reactive with specific antibody to RA receptor (RAR) alpha in the gel containing the nuclear fraction of CL-1 cells. Northern blotting analysis with specific cDNA probes revealed the expression of RAR alpha and RAR gamma in CL-1 cells. These results indicate that CL-1 cells express two types of RAR subtype, suggesting that these receptor molecules may mediate biological effects of RA. Treatment of CL-1 cells with RA resulted in an increase in the incorporation of [3H]thymidine into TCA-insoluble materials. The maximal increase was observed at 10(-6) M around 48 h. Previously, we demonstrated the autocrine growth of HSG cells mediated by epidermal growth factor (EGF) receptors and EGF-like molecules (Kurokawa et al. (1989) Cancer Res. 49, 5136-5142) and showed that RA had no significant effect on the secretion of the EGF-like molecule. RA induced an increase in [125I]EGF binding to CL-1 cells. The increase in the EGF binding was maximal at 24 h at 10(-6) M RA. RA also increased the amount of [3H]leucine-labeled EGF receptor dose-dependently. No significant change was observed in total protein synthesis of CL-1 cells by treatment with RA. These results suggest that RA stimulates the growth of CL-1 cells by increasing EGF receptor levels.

Effect of glucocorticoid on epidermal growth factor receptor in human salivary gland adenocarcinoma cell line HSG

Human salivary gland adenocarcinoma (HSG) cells treated with 10(-6) M triamcinolone acetonide for 48 h exhibited a 1.7- to 2.0-fold increase in [125I]human epidermal growth factor (hEGF) binding capacity as compared with untreated HSG cells. Scatchard analysis of [125I]EGF binding data revealed that the number of binding sites was 83,700 (+/- 29,200) receptors/cell in untreated cells and 160,500 (+/- 35,500) receptors/cell in treated cells. No substantial change in receptor affinity was detected. The dissociation constant of the EGF receptor was 0.78 (+/- 0.26).10(-9) M for untreated cells, whereas it was 0.93 (+/- 0.31).10(-9)M for treated cells. The triamcinolone acetonide-induced increase in [125I]EGF binding capacity was dose-dependent between 10(-9) and 10(-6)M, and maximal binding was observed at 10(-6)M. EGF receptors on HSG cells were affinity-labeled with [125I]EGF by use of the cross-linking reagent disuccinimidyl suberate (DSS). The cross-linked [125I]EGF was 3-4% of the total [125I]EGF bound to HSG cells. The affinity-labeled EGF receptor was detected as a specific 170 kDa band in the autoradiograph after SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Densitometric analysis revealed that triamcinolone acetonide amplified the intensity of this band 2.0-fold over that of the band of untreated cells. EGF receptor synthesis was also measured by immunoprecipitation of [3H]leucine-labeled EGF receptor protein with anti-hEGF receptor monoclonal antibody. Receptor synthesis was increased 1.7- to 1.8-fold when HSG cells were treated with 10(-8)-10(-6)M triamcinolone acetonide for 48 h. When the immunoprecipitated, [35S]methionine-pulse-labeled EGF receptor was analyzed by SDS-PAGE and fluorography, the newly synthesized EGF receptor was detected at the position of 170 kDa; and treatment of HSG cells with triamcinolone acetonide resulted in a 2.0-fold amplification of this 170 kDa band. There was no significant difference in turnover rate of EGF receptor between treated and untreated HSG cells. These results demonstrate that the triamcinolone acetonide-induced increase in [125I]EGF binding capacity is due to the increased synthesis of EGF receptor protein in HSG cells.