Modulation of cell shedding and glycosaminoglycan synthesis of human malignant keratinocytes by all-trans-retinoic acid and hydrocortisone in vitro.

Physiologic concentrations (5 X 10(-8) M) of all-trans-retinoic acid (RA) caused a 2- to 3-fold increase in the rate of cell desquamation of a malignant keratinocyte line (SqCC/Y1) grown in serum-free medium. Measurement of the incorporation of [35S]sulfate and [3H]glucosamine into cetylpyridinium chloride-precipitable glycosaminoglycans (GAGS) demonstrated that RA treatment did not alter total GAG production. In addition, compartmental distribution was not affected by RA, with 50-70% of GAGS being recovered from the medium, 25% from the pericellular matrix, and the remainder from the cells. Relatively small amounts of GAGS were associated with shed cells in RA-treated cultures, presumably reflecting a relatively short association of these cells with the monolayer before desquamation. Chondroitin sulfate (Ch-S), heparin/heparan sulfate (Hep-S), and hyaluronic acid (HA) were the GAG species identified in SqCC/Y1 cultures by gel-exclusion chromatography. RA reduced the relative amount of HA in the trypsin-sensitive pericellular compartment by 50%. Since the proportions of Ch-S and Hep-S were not affected by RA, the findings suggest that the altered ratio of HA to sulfated GAGS in this fraction may contribute to the increased cell desquamation. Hydrocortisone (10(-6) M) reversed the effect of RA on cell shedding, and increased the proportion of pericellular HA relative to that found in cultures exposed to RA alone. These findings support the concept that the relative proportion of HA to sulfated GAGS may be important in the intercellular cohesion of keratinocytes. In addition, the relative decrease in HA and the predominance of Ch-S over Hep-S in SqCC/Y1 cultures differed from results reported with normal keratinocytes, indicating that this property may be associated with the malignant phenotype.