Phosphaturic mesenchymal tumor-induced rickets.

We describe two prepubertal girls with oncogenic rickets. The first patient, 9 years of age, presented with recent-onset lower-extremity pain. The second girl, presented at 4 years of age following a 9-month period of muscle weakness, bone pain, and poor linear growth. Laboratory analyses in both patients revealed hypophosphatemia and hyperphosphaturia; elevated circulating alkaline phosphatase activity was present in one of them. Radiographic evidence of a generalized rachitic process was evident in both cases. Computerized tomography of the paranasal sinuses and facial bones in patient 1 revealed a small lesion eroding through the inner table of the left mandibular ramus. Microscopic examination of this mass revealed a spindle cell neoplasm with chondroid material, dystrophic calcification, and both osteoclast-like and fibroblast-like cells. Prominent vascularity and marked atypia were present. These features are consistent with a phosphaturic mesenchymal tumor of the mixed connective tissue variant. In the second patient, computerized tomography revealed a lytic lesion located in the right proximal tibia, with histologic features consistent with a phosphaturic mesenchymal tumor of the nonossifying fibroma-like variant. Resection of each tumor resulted in rapid correction of the phosphaturia and healing of the rachitic abnormalities. A careful search for small or occult tumors should be carried out in cases of acquired phosphaturic rickets.

Pigmentary anomalies in the multiple lentigines syndrome: Is it distinct from LEOPARD syndrome?

We observed 2 families with 26 individuals affected by multiple lentigines syndrome (MLS). All patients had extensive generalized lentigines, including in the axillary and inguinal regions, diffuse hyperpigmentation, hypopigmented patches, and hyperpigmented patches, many of which appeared clinically to be cafe au lait spots. Multiple lentigines syndrome should be considered in the differential diagnosis of multiple cafe au lait spots in children, particularly since the spots are usually present before the lentigines develop and may be clinically indistinguishable from the cafe au lait spots of neurofibromatosis. No significant noncutaneous features occurred in the two families with three generations of affected individuals, suggesting that MLS is a distinct entity. However, patients with the noncutaneous abnormalities of the LEOPARD syndrome have been described in families in which most members had pigmentary lesions only. Therefore, patients with multiple lentigines should be evaluated for noncutaneous abnormalities, particularly hearing loss and cardiac anomalies. Similarly, until investigators demonstrate lack of genetic linkage between MLS and LEOPARD syndrome, genetic counseling of patients affected by the cutaneous features of the former should include the potential for noncutaneous features in offspring.

Ganglioside GT1b inhibits keratinocyte adhesion and migration on a fibronectin matrix.

Highly sialylated gangliosides have been shown to alter cellular adhesion to a fibronectin matrix. The effect of these gangliosides on the adhesion, spreading, and migration of cultured keratinocytes on a fibronectin matrix has not been explored. Ganglioside GT1b significantly prevented attachment of keratinocytes to fibronectin and also detached previously adherent keratinocytes in a concentration-dependent manner without cell toxicity. GT1b did not affect adhesion of keratinocytes to wells coated with laminin, type I or type IV collagen, 804G extracellular matrix, or albumin. GT1b also inhibited keratinocyte migration on fibronectin in a concentration-dependent manner at concentrations as low as 5 nM GT1b, but had no effect on migration of keratinocytes plated on other matrices. GT1b binds to intact fibronectin and to the 120-kD RGDS-containing cell-binding fibronectin fragment, but not to the heparin- or gelatin-binding fragments of fibronectin. Although RGDS competes with GT1b in inhibiting adhesion, GT1b does not diminish binding of keratinocytes to a derivatized RGDS substratum, suggesting that the GT1b effect involves a non-RGDS site in the cell-binding region that modulates RGDS/alpha 5 beta 1 integrin receptor interaction. Through a specific effect on keratinocyte interaction with fibronectin, GT1b may participate in the regulation of cell adhesion and migration on a fibronectin substratum, which are important events during wound healing and the spreading of cutaneous neoplasia.

Chemiluminescence detection of gangliosides by thin-layer chromatography.

We describe a method for the detection of gangliosides on thin-layer chromatography plates using enhanced chemiluminescence. In contrast to previously published colorimetric techniques, the use of chemiluminescence of detect antibody binding to gangliosides has increased sensitivity and simplicity. In addition, the use of chemiluminescence lacks the hazards of radioactivity, and produces a permanent record.

Ganglioside GT1b induces keratinocyte differentiation without activating protein kinase C.

The altered patterns of expression of gangliosides during density-dependent growth inhibition, oncogenic transformation, and embryogenesis suggest that gangliosides, sialylated membrane glycolipids, may affect cellular proliferation and differentiation. Gangliosides of the "b" pathway of ganglioside synthesis, including GM3, GD3, and GD1b, inhibit the proliferation of cultured keratinocytes without increasing differentiation. We have examined the effect on keratinocyte proliferation and differentiation of supplemental ganglioside GT1b, a more highly sialylated ganglioside of the "b" synthetic pathway that is also present in cultured keratinocytes. In contrast to the lack of effect on differentiation of these other gangliosides, we noted significant induction of keratinocyte differentiation by GT1b, as evidenced by early desmosome formation, and increased cornified envelope formation and expression of involucrin and of the differentiation-specific keratin K1. The addition of GT1b did not cause a shift in intracellular free calcium or alter protein kinase C activity. Alterations in the membrane concentration of ganglioside GT1b, a minor ganglioside component of the keratinocyte membrane, may participate in regulating keratinocyte differentiation.

Familial multiple cafe au lait spots.

BACKGROUND: Familial multiple cafe au lait spots (CLS) represent a rare, autosomal dominant pigmentary disorder characterized by the multiple CLS seen in neurofibromatosis type 1 (NF-1) but differing from NF-1 by the absence of neurofibromas and other neural crest tumors. OBSERVATIONS: We describe multiple CLS in 12 patients from three families, each with at least two generations of affected adults. The clinical presentation was consistent within families. In one family, the CLS were accompanied by axillary and inguinal freckling and Lisch nodules. Otherwise, none of the 12 patients had neurofibromas or noncutaneous manifestations of NF-1. CONCLUSIONS: These families provide further evidence that patients may have multiple CLS, with or without axillary freckling or Lisch nodules, and yet not have NF-1. Care must be taken when counseling families with CLS that the diagnosis of NF-1, with its many associated potential problems, is not made erroneously. Studies of the gene mutation(s) of patients with familial multiple CLS are needed to distinguish NF-1 and familial multiple CLS as distinct disorders.

Z-4',5'-didehydro-5'-deoxy-5'-fluoroadenosine (MDL 28,842), an irreversible inhibitor of S-adenosylhomocysteine hydrolase, suppresses proliferation of cultured keratinocytes and squamous carcinoma cell lines.

S-Adenosylmethionine-dependent transmethylation reactions are required for many critical pathways in human cells. The enzyme S-adenosylhomocysteine hydrolase converts S-adenosylhomocysteine, a potent endogenous inhibitor of S-adenosylmethione-mediated methyltransferase reactions, to adenosine and L-homocysteine. The effects of the inhibitor of S-adenosylhomocysteine hydrolase, Z-4',5'-didehydro-5'-deoxy-5'-fluoroadenosine (MDL 28,842), on the growth of cultured keratinocytes and cutaneous squamous cell carcinoma lines were investigated. MDL 28,842 suppressed the proliferation of all cells in a dose-dependent manner, and significantly increased keratinocyte differentiation at a concentration of 1 microM. Following incubation with MDL 28,842, the methylation indices (ratio of S-adenosylmethionine/S-adenosylhomocysteine) of undifferentiated keratinocytes and squamous cell carcinoma lines were significantly decreased. These data demonstrate that the inhibitory effect of MDL 28,842 on squamous carcinoma cells and keratinocyte proliferation may result directly from inhibition of S-adenosylhomocysteine hydrolase activity. The antiproliferative activity of MDL 28,842 against squamous carcinoma cells and keratinocytes suggests a potential role for MDL 28,842 as a novel therapeutic agent for neoplastic and hyperproliferative disorders of the skin.

Ganglioside GM3 inhibits the proliferation of cultured keratinocytes.

Ganglioside GM3 is the predominant ganglioside of keratinocyte membranes. It has been proposed in other cell types that GM3 may participate in the regulation of cell proliferation. To examine the role of GM3 in keratinocyte proliferation, purified GM3 was added to cultured keratinocytes from normal foreskin, from lesional skin of patients with psoriasis and ichthyosis, and to cutaneous squamous carcinoma cell lines. Supplemental GM3 inhibited the growth of all cultured keratinocytes in a dose-dependent manner at concentrations of 10-100 microM. Keratinocytes from patients with psoriasis and ichthyosis were most sensitive to the inhibitory effects of GM3, and confluent undifferentiated keratinocytes were least sensitive. No change in differentiation was noted after addition of GM3. GD3, 9-0-acetyl-GD3, and GD1b also inhibited keratinocyte proliferation. Gangliosides GM1 and GD1a and sialic acid had little effect. Addition of 50 microM 3H-GM3 to cultured keratinocytes resulted in 1.7 times the amount of cellular GM3. These data suggest that hematoside (GM3) and "b" pathway gangliosides (GD3, GD1b), generated by the preferential activation of sialyltransferase II versus N-acetylgalactosaminyltransferase, may be involved in control of keratinocyte growth but not of differentiation.

Alteration in keratinocyte ganglioside content in basal cell carcinomas.

We examined the ganglioside content of normal human keratinocytes and basal cell carcinomas (BCC). The total ganglioside content of the epidermis was 0.098 +/- 0.01 microgram lipid-bound sialic acid/mg dry weight. GM3 was the predominant ganglioside of epidermis. GM2 and GD3 were also found in significant amounts. Polysialylated gangliosides were identified in only small amounts. In contrast to all other body locations, breast epidermis showed large amounts of GM1. The total ganglioside content of nodular and sclerosing facial BCC was approximately 3.5 times that of normal facial epidermis. This marked elevation of total ganglioside was not affected by dermal ganglioside contamination, because the total ganglioside content of the dermis was similar to that of the epidermis. The relative percentage of GM2 was significantly decreased, whereas the relative percentage of GM3 was slightly decreased in BCC. 9-O-acetyl-GD3 was present in the BCC, but not in normal epidermis or dermis. 9-O-acetyl-GD3 may be a surface marker for BCC. Furthermore, the alterations in amount and composition of individual gangliosides on neoplastic membranes may lead to novel therapeutic interventions.