Kaposi's sarcoma tumor cells preferentially express Bcl-xL.

Several recently identified proteins such as Bcl-2 and Bcl-x have been found to regulate programmed cell death (i.e., apoptosis). In this report, we examined the levels of expression of proteins that can either prevent apoptosis (i.e., Bcl-2 or the long form of Bcl-x, designated Bcl-x1) or promote apoptosis (i.e., Bax or the short form of Bcl-x, designated Bcl-xs) in proliferating benign and malignant endothelial cells (ECs). In normal skin with quiescent ECs, no detection by immunohistochemical staining was observed for Bcl-xL, Bcl-xs, or Bcl-2. However, in diseased skin samples that feature a prominent angiogenic response such as in psoriasis or pyogenic granulomas, the proliferating ECs markedly overexpressed Bcl-xL, with little to no Bcl-2. In an acquired-immune-deficiency-syndrome-related neoplasm, Kaposi's sarcoma, the spindle-shaped tumor cells also overexpressed Bcl-xL compared with Bcl-2. These in vivo studies were extended in vitro using cultured ECs and Kaposi's sarcoma tumor cells that were examined by flow cytometry and immunoblot analysis. Both cultured ECs and Kaposi's sarcoma tumor cells express significantly higher levels of Bcl-xL than Bcl-2. Such overexpression of cell survival gene products may contribute to prolonging the longevity of EC-derived cells in several different benign and neoplastic skin disorders that are characterized by a prominent angiogenic tissue response.     

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

Modulation of keratinocyte motility. Correlation with production of extracellular matrix molecules in response to growth promoting and antiproliferative factors.

Normal human epidermal keratinocytes (KC) grown under conditions that maintain the undifferentiated state are highly motile. Migration of these cells as measured in two different assays (migration out of an agarose drop explant, and into micropore filters in a modified Boyden chamber), is stimulated by fibronectin (FN) and to a lesser extent by thrombospondin (TSP). In contrast, laminin (LN) inhibits KC migration. Cultivation of the cells for 1 day under conditions that induce differentiation (ie, in the presence of 1.4 mM Ca2+) suppresses KC motility. A number of soluble growth modulating polypeptide factors also influence KC migration. Transforming growth factor-beta (TGF-beta) and epidermal growth factor (EGF) stimulate KC motility. These factors simultaneously induce KC production of FN and a significant portion of the stimulated motility can be inhibited with antibodies to FN. EGF and somatomedin-C (SM-C), but not TGF-beta, also stimulate TSP production while EGF and SM-C (but not TGF-beta) induce KC proliferation. In contrast to these factors, interferon-gamma (INF-gamma) inhibits KC production of both FN and TSP and concomitantly inhibits both motility and proliferation. These data suggest that KC properties essential for normal wound healing (ie, motility and proliferation) are regulated by both extracellular matrix molecules and soluble peptide factors. Finally, these effects of various growth promoting and antiproliferative factors on KCs may, in part, be mediated through alteration in the endogenous production of extracellular matrix molecules by KCs.     

Cutaneous expression of Thy-1 in mycosis fungoides.

Dermal dendritic cells from eleven cases of mycosis fungoides (MF) (six patch and five plaque stage), two cases of pre-MF, and five specimens of normal human skin, were characterized immunohistochemically using a panel of antibodies including anti-human Thy-1, intercellular adhesion molecule-1 (ICAM-1; CD54), endothelial leukocyte adhesion molecule-1 (ELAM-1), vascular cell adhesion molecule-1 (VCAM-1), CD1a, CD2, CD14, CD18, CD34, MAC387, KP-1, EBM-11, factor XIIIa, factor XIIIs, and S100. Thy-1 expression in normal skin was limited to the microvascular endothelium and perivascular dendritic cells. An extensive interstitial network of Thy-1+ dendritic cells was seen in the papillary dermis of all cases of MF, whereas no epidermal cells were Thy-1+. The mean +/- standard deviation of interstitial Thy-1+ cells per high power field in the dermis was: normal skin, 2.86 +/- 0.34; pre-MF, 15; patch stage MF, 13.4 +/- 7.08; plaque stage MF, 49.96 +/- 21.29. Thy-1+ dendritic cells morphologically resembled the factor XIIIa+ "dermal dendrocyte" (DD) and shared their VCAM-1+, ICAM-1+, CD1a, CD2-, CD14+, CD18+, EMB11+, factor XIIIa+, factor XI-IIs-, S100-, MAC387- and KP-1-immunophenotype in MF. Double labeling studies revealed up to 50% of Thy-1+DD were also factor XIIIa+ in MF. Immediately beneath these cells was a similar network of CD34+, Thy-1-, factor XIIIa- dendritic cells limited to the reticular dermis. Strong microvascular endothelial cell expression of Thy-1 and VCAM-1, and focal vascular ELAM-1 expression were also seen in MF. Distinct cellular compartmentalization (papillary dermis versus reticular dermis versus epidermis) of dendritic cells is demonstrated by the differential expression of Thy-1, factor XIIIa, and CD34 antigens. The extensive number and prominent dermal dendritic network in the papillary dermis juxtaposed between epidermal keratinocytes (KC) and dermal/epidermal T cells, suggests an important pathophysiologic role for this newly recognized and immunophenotypically distinctive cell population in MF.