Distribution of an estrogen receptor-related protein (P29) in normal skin and in cultured human keratinocytes

Role of estrogen receptor-related antigen in initiating the growth of human glioma cells

OBJECT

The expression of estrogen receptor-related antigen (ER-D5) has been demonstrated in many tumors, including those of the brain, but the actual role of ER-D5 in cell growth is unknown. The authors evaluated the role of ER-D5 in the growth of gliomas in vitro.

METHODS

Human glioblastoma multiforme (GBM) cell lines A172, T98G, U87MG, and U118MG; rat C6 glioma and 9L gliosarcoma; AS human astrocytoma; GBM in primary culture and tumor tissues; and normal brain tissues were examined for ER-D5 by using immunohistochemical, Western immunoblot, flow cytometry, and enzyme-linked immunosorbent assays. The ER-D5 was detected in all tumor cell types of human origin, but not in rat cell lines and normal brain; the expression of ER-D5 was not related to cell cycle phase. Kinetic analysis of ER-D5 expression in cultured cell lines revealed that an enhanced and sharp accumulation of ER-D5 occurred during the first 24 hours of culture, followed by a sharp fall in the next 24 hours. Gradual decreases of ER-D5 during the subsequent days were demonstrated in all human cell lines, and in primary cultures of GBM. This accumulation pattern of ER-D5 was confirmed on Western blot analysis. The ER-D5 was also detected in cells cultured in serum-free medium. Culture cells were treated with D5 antibody against ER-D5 for 48 hours and the effects were evaluated using a monotetrazolium colorimetric assay; the result revealed that growth of cultured cells was inhibited in a dose-dependent manner, and that addition of a single median inhibitory concentration dose resulted in complete growth inhibition and arrest of cell growth at the G0/G1 phase at 96 hours posttreatment.

CONCLUSIONS

These findings indicated that synthesis and accumulation of ER-D5 is an essential event in the very early phase of in vitro growth of human gliomas.

Oestrogen receptor beta is the predominant oestrogen receptor in human scalp skin

Oestrogens play a major role in non-classic target tissues in both sexes, yet there have been few studies on estrogens and skin. Recently a second oestrogen receptor (ERbeta) has been discovered. Therefore, we have compared the expression of oestrogen receptor alpha (ERalpha), beta (ERbeta), the androgen receptor (AR) and a cell proliferation marker in male and female non-balding scalp skin. ERbeta was the major steroid receptor expressed in human skin. It was highly expressed in epidermis, blood vessels and dermal fibroblasts, in contrast to ERalpha and AR. In the hair follicle, ERbeta expression was localized to nuclei of outer root sheath, epithelial matrix and dermal papilla cells, in contrast to ERalpha, and the AR, which was only expressed in dermal papilla cells. Serial sections also showed strong nuclear expression of ERbeta in the cells of the bulge, while neither ERalpha nor AR was expressed. In the sebaceous gland, ERbeta was expressed in both basal and partially differentiated sebocytes. ERalpha exhibited a similar pattern of expression, while the AR was expressed in the basal and very early differentiated sebocytes. There was no obvious difference in the expression of either oestrogen receptor in male or female skin. The wide distribution of ERbeta in human skin suggests that oestrogens may play an important role in the maintenance of skin and in the regulation of the pilosebaceous unit, and provides further evidence for oestrogen action in non-classic target tissues. The differential expression of ERalpha, ERbeta and AR in human skin suggests that the mechanisms by which steroid hormones mediate their effects may be more complex than previously thought.

The biological actions of estrogens on skin

There is still extensive disparity in our understanding of how estrogens exert their actions, particularly in non-reproductive tissues such as the skin. Although it has been recognized for some time that estrogens have significant effects on many aspects of skin physiology and pathophysiology, studies on estrogen action in skin have been limited. However, estrogens clearly have an important function in many components of human skin including the epidermis, dermis, vasculature, hair follicle and the sebaceous, eccrine and apocrine glands, having significant roles in skin aging, pigmentation, hair growth, sebum production and skin cancer. The recent discovery of a second intracellular estrogen receptor (ERbeta) with different cell-specific roles to the classic estrogen receptor (ERalpha), and the identification of cell surface estrogen receptors, has provided further challenges to understanding the mechanism of estrogen action. It is now time to readdress many of the outstanding questions regarding the role of estrogens in skin and improve our understanding of the physiology and interaction of steroid hormones and their receptors in human skin. Not only will this lead to a better understanding of estrogen action, but may also provide a basis for further interventions in pathological processes that involve dysregulation of estrogen action.

Retinoid receptors and keratinocytes

In 1987, a tremendous boost in our understanding of the action of dietary vitamin A occurred with the discovery and characterization of nuclear receptors for retinoic acid, the active form of the vitamin, in the laboratories of P. Chambon and R. Evans. They have shown that the nuclear receptors are ligand-activated transcription factors capable of specific gene regulation. Since that discovery, it has been determined that there are at least six retinoic acid receptors belonging to two families, RARs and RXRs, that they are differentially expressed in various mammalian tissues, and that they act as homo- and heterodimers interacting with other ligand-activated nuclear receptors. The domain structure of the receptors has been described, and their DNA-binding, ligand-binding, dimerization, and transcriptional activation regions characterized. Among the most important retinoid-regulated genes are the homeobox proteins, regulatory transcription factors which are responsible for body axis formation, patterning, limb formation, and other crucial processes during development. Retinoic acid and its receptors also regulate many differentiation markers which are particularly important in stratified epithelia, such as skin and oral epithelia. Our increased understanding led to improved therapy of a large number of skin disorders, ranging from acne to wrinkles and including epidermal and oral carcinomas.

Immunohistochemical expression of the estrogen receptor-related antigen (ER-D5) in human intracranial tumors

BACKGROUND

Expression of the estrogen receptor-related antigen (ER-D5) has been reported in some normal and neoplastic tissues. The authors evaluated the expression of ER-D5 in 143 intracranial tumors of different histologic types.

METHODS

Formalin fixed, paraffin embedded tumor sections were stained with the monoclonal D5 antibody by avidin-biotin complex immunohistochemistry.

RESULTS

Eighty-eight (62%) of the 143 brain tumors showed positive ER-D5 immunoreactivity. ER-D5 expression was observed in 9/30 low grade astrocytomas, in 6/13 anaplastic astrocytomas, in 16/27 glioblastomas, in 2/5 ependymomas, in 5/8 medulloblastomas, in 10/15 meningiomas, in 20/23 schwannomas, in 11/11 hemangioblastomas, in 9/9 germ cell tumors, in 0/2 oligodendrogliomas, and in 17/28 pediatric and childhood brain tumors. The mean percentage of ER-D5-positive cells varied in different tumor types, was lowest in the meningotheliomatous meningiomas, and was highest in the hemangioblastomas. ER-D5 immunoreactivity was also observed in the microvascular endothelial proliferations and in tumor blood vessels. ER-D5 expression in tumors was not related to the overall tumor grades, but a statistically significant higher percentage of ER-D5-positive cells was noted in the glioblastomas compared with the low grade astrocytomas (P < 0.05) and in the combined high grade tumors compared with the low grade tumors (P < 0.005) if vascular-origin tumor hemangioblastomas are considered a separate entity from other brain tumors.

CONCLUSION

The current study suggests that the ER-D5 antigen may participate in the growth of the intracranial tumors and tumor angiogenesis. ER-D5 in embryonal and germ cell brain tumors suggests that ER-D5 may be a developmentally regulated protein.

Female sex hormone stimulates cultured human keratinocyte proliferation and its RNA- and protein-synthetic activities

The present study was carried out to assess the effect of female sex hormones, i.e., estrogen and progesterone, on human keratinocyte proliferation, and its RNA- and protein-synthetic activities in a culture system. The presence of receptors for estrogen and progesterone and their messenger ribonucleic acids (mRNAs) in the cultured cells was also investigated. Human keratinocytes were cultured in the experimental DMEM-Ham's F12 medium containing various concentrations of estrogen or progesterone, which was followed by determining cell yields and [3H]thymidine incorporation. The keratinocytes were also tested for RNA- and protein-synthetic activities by measuring [3H]uridine and [3H]leucine incorporation. Both estrogen and progesterone receptors were determined by the enzyme immunoassay method using monoclonal antibodies, and mRNA expression for these hormone receptors was detected by in situ hybridization. Cell yields and [3H]thymidine incorporation increased gradually until 3 x 10(-10) M of both estrogen and progesterone, decreased thereafter until 3 x 10(-7) M, and peaked at 3 x 10(-10) M. [3H]Uridine and [3H]leucine uptake followed almost the same pattern as the cell proliferation, peaking at 3 x 10(-10) M of both hormones. Small amounts of estrogen and progesterone receptors were present in the cultured cells, and their mRNAs were found to be present in the cell cytoplasm. These results clearly suggest that sex hormones play an important role in human keratinocyte proliferation, and its RNA- and protein-synthetic activities, at least in part, via their hormone receptors.

Pachydermoperiostosis: study of epidermal growth factor and steroid receptors

Pachydermoperiostosis is a rare osteo-cutaneous disease characterized by hypertrophy of bones and surrounding soft tissues. The cutaneous manifestations include coarsening of facial features, cutis verticis gyrata, digital clubbing, hyperhidrosis and seborrhoea. The pathogenetic mechanism of the disease is still debated, and proposed aetiological factors include genetic influences, anomalies in fibroblast activity, or alteration in peripheral blood flow. We studied a patient with the incomplete form of pachydermoperiostosis, assessing epidermal growth factor receptor (EGF-R) and sex hormone steroid receptors (SR) in the affected skin, and also evaluating the urinary excretion of EGF. The results showed high levels of nuclear steroid receptors, increased cytosolic oestrogen receptors, and no detectable progesterone and androgen cytosolic receptors. EGF-R was also undetectable, and the urinary excretion of EGF was elevated. These findings suggest that the increased tissue sensitivity to circulating sex-steroids could induce enhanced tissue EGF/transforming growth factor alpha (TGF-alpha) production and utilization. The SR-EGF-R system could therefore be involved in determining hypertrophy of the affected tissues.

Dynamic changes in intracellular localization and isoforms of the 27-kD stress protein in human keratinocytes

We have begun to characterize the low molecular weight, 27-kD heat shock or stress protein (HSP27) in normal keratinocytes and in HaCaT, a spontaneously transformed keratinocyte line. The presence and location of HSP27 was determined by indirect immunofluorescence on fixed whole cells and immunoblot analysis of cytosolic, membrane, nuclear, and cytoskeletal cell fractions. HSP27 is localized throughout the cytoplasm of cells at 37 degrees C. After heating at 42 degrees C, there is a rapid (within 10 min) increase in nuclear HSP27. Two-dimensional gel analysis of whole cell HaCaT lysates identified multiple isoforms of HSP27 with different isoelectric points. The function of HSP27 is largely unknown but its presence throughout the cytoplasm of cells at 37 degrees C, its translocation to the nucleus after cellular stress, and the presence of multiple isoforms suggest a biologic role in both stressed and unstressed human keratinocytes.

Expression of an estrogen receptor-associated protein (p29) in epithelial tumors of the skin

p29 is a cytoplasmic serine phosphoprotein of 29 kD MW, closely linked to estrogen receptors. In this work we studied the expression of p29 protein in normal human skin and a group of cutaneous benign and malignant tumors by using a monoclonal antibody (ERD5) that specifically recognizes p29. In normal skin, p29 reactivity was observed in epidermal and some adnexal keratinocytes, as well as in smooth muscle cells of dermal arterioles and arrector pili muscles. p29 was also detected in most, but not all, epithelial tumors studied. The expression of p29 was generally stronger in the more differentiated (keratinized) normal and neoplastic keratinocytes; however, no correlation could be noted between immunochemical staining for p29 and either benignity of the lesion or sex of the patient considered. Whereas, in breast cancer, the expression of p29 is reported to correlate with endocrine response, the precise relationship between epithelial tumors of the skin and the action of estrogens remains to be elucidated.