Alterations in cholesterol sulfate and its biosynthetic enzyme during multistage carcinogenesis in mouse skin.

Recent evidence suggests that cholesterol sulfate may be an important second messenger involved in signaling epidermal differentiation in skin. The activity of cholesterol sulfotransferase (Ch-ST) is increased during squamous differentiation of keratinocytes and is believed to be a marker enzyme for terminal differentiation. The primary objective of this study was to examine changes in levels of cholesterol sulfate (CS) and activity of its biosynthetic enzyme, Ch-ST, during multistage carcinogenesis in mouse skin. Using SENCAR mice, we determined the activity of Ch-ST in normal epidermis, in tumor promoter-treated epidermis, in epidermis during wound healing, and in mouse skin tumors generated by initiation-promotion regimens. A single topical application of tumor promoters led to significantly elevated levels of Ch-ST activity and of CS. Epidermal Ch-ST activity was also elevated during wound healing. Dramatic increases in CS levels and in the activity of Ch-ST were found in nearly all of the papillomas and squamous cell carcinomas examined. The increased levels of CS and activity of Ch-ST in tumor promoter-treated epidermis were accompanied by increased transglutaminase-I activity. In contrast, transglutaminase I activity was not elevated in primary papillomas or squamous cell carcinomas. Finally, Ch-ST activity was significantly elevated in the epidermis of newborn HK1.ras transgenic mice, whereas transglutaminase I activity did not correlate with Ch-ST activity in these mice. These results demonstrate that diverse tumor-promoting stimuli all produce elevated CS levels and Ch-ST activity and that CS levels and Ch-ST activity were constitutively elevated in both papillomas and squamous cell carcinomas. The data also suggest a mechanism for upregulation of Ch-ST in skin tumors involving activation/upregulation of Ha-ras.

Programmed expression of cholesterol sulfotransferase and transglutaminase during epidermal differentiation of murine skin development.

To clarify the role of cholesterol sulfate (CS) in the process of epidermal differentiation in vivo, we investigated the concentration of CS and the specific activities of cholesterol sulfotransferase (CST), cholesterol sulfate sulfatase (CS sulfatase) and epidermal transglutaminase (ETG) in murine skin in the pre- and postnatal periods. In the skin at day 14 of gestation, CS was not detected with TLC and the specific activities of all the enzymes were low. However, concomitant with the formation of the multilayered structure of the epidermis (at day 16), the specific activities of CST steeply increased. Although the insoluble CS sulfatase in the microsomal fraction remained at a relatively constant level, the soluble CST in the cytosol fraction showed a 6-fold increase from day 14 to day 16, and the activity decreased continuously in the following period, reaching one forty-sixth of the maximum level at 4-months-old mice. Reflected by the increase in activity, CS was detected in fetal skin at day 15, and the concentration in epidermis significantly increased during the gestation period, reaching maximum level at day 17. Furthermore, the changes in the concentration of cholesterol sulfate were identical with those of N-(O-linoleoyl)-omega-hydroxy fatty acyl sphingosine and its glucosyl derivative in the epidermis. On the other hand, the specific activity of ETG increased after birth. Thus, the activation of CST and ETG was shown to occur separately in association with the formation of the multilayered structure and thickening of the stratum corneum, respectively.