UV mutation signature in tumor suppressor genes involved in skin carcinogenesis in xeroderma pigmentosum patients.

Molecular analysis of p53 and patched (PTCH), two candidate tumor suppressor genes for non-melanocytic skin cancer, was performed in skin tumors from six patients affected by the cancer-prone disease xeroderma pigmentosum (XP). UV-specific p53 mutations were detected at a frequency of 38-50% in all the tumor types analysed, including melanomas. Additional analysis of PTCH mutations in the subset of eight basal call carcinomas (BCC) revealed a very high mutation frequency of this gene (90%) which exceeded that detected in the p53 gene in the same tumors (38%). PTCH mutations were predominantly UV-specific C>T transitions. This mutation pattern is different from that reported in BCC from normal donors where PTCH mutation frequency is 27% and mutations are frequently deletions and insertions. These findings suggest that PTCH mutations represent an earlier event in BCC development than p53 alterations and that the inability of XP patients to repair UV-induced PTCH mutations might significantly contribute to the early and frequent appearance of BCC observed in these patients.

Novel mutations in the LAMC2 gene in non-Herlitz junctional epidermolysis bullosa: effects on laminin-5 assembly, secretion, and deposition.

Laminin-5 is the major adhesion ligand of epithelial cells. Mutations in the three genes (LAMA3, LAMB3, LAMC2) encoding the laminin-5 chains cause junctional epidermolysis bullosa, a clinically and genetically heterogeneous blistering skin disease. Here, we describe a non-Herlitz junctional epidermolysis bullosa patient, compound heterozygote for two novel mutations affecting the LAMC2 gene. The mutation in the paternal allele is a de novo splice site mutation (522-1G-->A) that results in in-frame skipping of exon 4 and synthesis of a mutated gamma2 polypeptide (gamma2Delta4) carrying a 33 amino acid deletion within the N-terminal domain V. The maternal mutation is a one base pair insertion (3511insA) in the 3' terminal exon of LAMC2 resulting in a frameshift and a premature termination codon. Mutation 3511insA is predicted to lead to the synthesis of a gamma2 polypeptide (gamma2t) disrupted in its alpha-helical C-terminal structure and truncated of the last 25 amino acids. Keratinocytes isolated from the patient's skin showed a markedly decreased level of gamma2 chain mRNA and secreted scant amounts of laminin-5, which undergoes physiologic proteolytic processing. To investigate the biologic function of the laminin-5 molecules synthesized by the patient, mutant gamma2 cDNAs were transiently expressed in gamma2-null keratinocytes. Transfection of the gamma2Delta4 cDNA resulted in restoration of laminin-5 deposition onto the culture substrate, which demonstrates that the gamma2 polypeptides carrying a deletion in domain V, upstream of the gamma2 proteolytic cleavage site, are assembled into native laminin-5 that is secreted and extracellularly processed. In contrast, transfection of a mutant cDNA expressing the gamma2t chain failed to restore laminin-5 immunoreactivity, which indicates that integrity of the gamma2 C-terminal amino acid sequences is required for laminin-5 assembly. These results correlate for the first time a functional alteration in a laminin-5 domain with a mild junctional epidermolysis bullosa phenotype.

Compound heterozygosity for a recessive glycine substitution and a splice site mutation in the COL7A1 gene causes an unusually mild form of localized recessive dystrophic epidermolysis bullosa.

Type VII collagen is the major component of anchoring fibrils, adhesion structures of stratified epithelia that span the basement membrane region and papillary dermis. Mutations in the gene COL7A1 encoding type VII collagen cause dystrophic epidermolysis bullosa, a clinically heterogeneous autosomal dominant or recessive blistering disorder of the skin and mucous membranes. In this report, we investigate three siblings affected by an unusually mild form of localized recessive dystrophic epidermolysis bullosa who were shown to be compound heterozygotes for novel mutations affecting COL7A1. The maternally inherited mutation is a G-->C transversion that converts a codon for glycine to a codon for arginine (G1347R). The paternal mutation is a neutral G-->A transition at the last base of exon 70(5820G-->A) that alters the correct splicing of COL7A1 pre-mRNA, giving rise to an aberrant mRNA carrying the in-frame skipping of exon 70 in addition to the full-length RNA transcript carrying the G-->A substitution. Consistent with the normal levels of COL7A1 mRNA transcripts detected by northern analysis, immunoblotting and immunofluorescence studies evidenced that the patient keratinocytes synthesize and secrete normal amounts of stable type VII collagen, which is correctly deposited at the dermal-epidermal junction. In addition, mutated type VII collagen molecules assemble to form numerous, normally shaped anchoring fibrils, as shown by electron microscopic examination. The combination of a recessive glycine substitution with a splice site mutation that permits partially correct splicing therefore leads to a normal expression of mutated type VII collagen molecules with marginally altered biologic activity, and to the extremely mild phenotype observed in our patients.

A homozygous nonsense mutation in type XVII collagen gene (COL17A1) uncovers an alternatively spliced mRNA accounting for an unusually mild form of non-Herlitz junctional epidermolysis bullosa.

In this study we describe six Italian patients presenting an unusually mild variant of non-Herlitz junctional epidermolysis bullosa associated with a reduced expression of type XVII collagen. All patients are homozygous for a novel nonsense mutation (R795X) within exon 33 of COL17A1 and show a common haplotype, attesting propagation of an ancestral allele within the Italian population. Analysis of patients' COL17A1 transcripts showed the presence of two mRNA species: a normal-sized mRNA carrying mutation R795X that undergoes rapid decay, and a transcript generated by in-frame skipping of exon 33. Patients keratinocytes were shown to synthesize minute amounts of type XVII collagen, which appeared correctly localized along the cutaneous basement membrane. We therefore suggest that the exon 33-deleted COL17A1 splice variant encodes for type XVII collagen molecules that maintain a functional role and account for the mild phenotype of our patients.

Detection of human papillomavirus DNA in laryngeal squamous cell carcinoma by polymerase chain reaction.

Although human papillomaviruses (HPVs) have been found in many, but not all, tumours of the oral cavity, nose, pharynx and larynx, the true role of HPV in malignant tumours of the head and neck is still unclear. The presence of HPV DNA was investigated in 45 fresh squamous cell carcinoma (SCC) specimens and in 29 normal mucosa specimens collected from 45 primary laryngeal SCC patients. HPV DNA was detected using the polymerase chain reaction (PCR) with consensus primers that detect HPV types 6, 11, 16 and 18.9 of the 45 patients (20%) were HPV positive; the presence of HPV was also detected in the corresponding normal laryngeal mucosa of four of the 29 specimens (14%). No statistically significant differences were found between the presence of HPV DNA in normal specimens and in neoplastic mucosa specimens. No correlation was found between HPV DNA positive tumours and size, T classification, lymph node involvement and histological grading. This study adds further evidence suggesting a possible role of HPV DNA infection in laryngeal carcinogenesis.

Epidermodysplasia verruciformis with multiple mucosal carcinomas treated with pegylated interferon alfa and acitretin.

Epidermodysplasia verruciformis (EV) is characterized by abnormal genetically-determined susceptibility to widespread and persistent infection of the skin with human papillomaviruses (HPV). The infection results in disseminated pityriasis versicolor-like lesions and flat warts. Skin malignant changes are very common and occur on sun-exposed areas. Several treatments have been used but without consistent benefit. Recently, retinoids and alpha-interferon, alone or in combination, have been reported to be of value in the therapy of EV lesions. We present the case of a 43-year-old white female affected by EV who developed multiple squamous cell carcinomas in the oral and genital mucosae during the previous four years. Both wart and cancer lesions harbored HPV24 along with the novel putative HPV type FA51. The patient was treated with a combination of acitretin (0.2 mg/kg per day) and peginterferon alfa-2b (1 microg/kg per week s.c.) for one year, with marked improvement of verrucous lesions and no recurrence of mucosal cancer. Thereafter, interferon was stopped whereas acitretin therapy was continued, but a new Bowen's disease developed in the perianal region, and the acitretin dose was increased at 0.5 mg/kg per day. At six-month follow-up, only a low number of flat warts persisted, and no clinical signs of cutaneous or mucosal carcinoma were evident.

Chronic staphylococcal osteomyelitis: a new experimental rat model.

A rat model of chronic staphylococcal osteomyelitis was developed. Fibrin glue (5 microliters) and Staphylococcus aureus (2 x 10(6) CFU/5 microliters) were inoculated into the proximal metaphysis of the tibia. The rats were killed at intervals of between 1 and 6 months, and the tibias were removed. Induced lesions were evaluated by radiographic, macroscopic, and histological examinations and bacterial counts. Roentgenograms revealed osteomyelitis in more than 90% of the tibias. Gross bone pathology revealed skeletal deformation, new bone formation, abscesses, and draining skin fistulas in more than 80% of cases. Histological examination revealed osteomyelitis in more than 90% of cases, and bacterial counts were positive in 86% of cases. Only fibrin glue (5 microliters) was inoculated into controls. Controls showed no osteomyelitic lesions, and counts were negative in seven of eight control tibias. The main feature of this model is the use of fibrin glue instead of the sclerosing agents and foreign bodies used in other models. The model reproduces lesions similar to those of human posttraumatic osteomyelitis and can be reliably used in pathophysiological and therapeutic studies.

180-kDa bullous pemphigoid antigen defective generalized atrophic benign epidermolysis bullosa: report of four cases with an unusually mild phenotype.

Generalized atrophic benign epidermolysis bullosa (GABEB) is a rare variant of non-lethal junctional epidermolysis bullosa characterized by generalized skin blistering healing with atrophy and by atrophic alopecia with onset in childhood. Other features include mild mucosal blistering, dental abnormalities and nail dystrophy. We report four additional cases of GABEB from two families originating from the same isolated village. The patients shared an unusually mild clinical phenotype with cutaneous blisters strictly limited to trauma sites and rare occurrence of oral mucosal lesions. Scalp, eyelash and eyebrow alopecia was present in only two cases. Immunofluorescence studies showed a markedly reduced expression of the 180-kDa bullous pemphigoid antigen (BP180), and northern analysis of cultured keratinocytes indicated that the gene encoding for BP180 is affected in these GABEB patients.

Pretibial dystrophic epidermolysis bullosa: a recessively inherited COL7A1 splice site mutation affecting procollagen VII processing.

Pretibial epidermolysis bullosa (PEB) is a rare form of localized epidermolysis bullosa dystrophica (EBD), a heterogeneous group of inherited, blistering diseases characterized by scarring, loss of dermal-epidermal adhesion and altered anchoring fibrils (AF). Mutations in the type VII collagen gene (COL7A1) underlie EBD and in a dominant PEB family a glycine substitution mutation has been identified. We report a 33-year-old man affected by PEB showing abnormal AF and reduced immunostaining for type VII collagen. Mutation search in the COL7A1 gene revealed a 14 bp deletion in the 115 exon-intron boundary (33563del14), which resulted in the in-frame skipping of exon 115 with elimination of 29 amino acids from the pro-alpha1(VII) polypeptide chain. As a consequence, procollagen VII failed to be processed to mature collagen VII and accumulated at the dermal-epidermal junction, as revealed by immunofluorescence staining using a NC-2 domain-specific antibody. The proband's father was a clinically unaffected heterozygous carrier of mutation 33563del14, whereas the maternal pathogenetic mutation has still not been identified. This represents the first report of a recessive deletion mutation in PEB and extends the range of EBD phenotypes associated with mutation 33563del14.

Non-Herlitz junctional epidermolysis bullosa without hair involvement associated with BP180 deficiency.

Junctional epidermolysis bullosa (JEB) is a clinically and genetically heterogeneous recessively inherited blistering disease of the skin and mucous membranes due to impaired epithelial adhesion. In particular, defective expression of the 180-kD bullous pemphigoid antigen (BP180) has been correlated to a non-lethal (non-Herlitz) form of JEB, generalized atrophic benign epidermolysis bullosa (GABEB), characterized by widespread skin blistering healing with atrophy and by atrophic alopecia with onset in childhood. We report the case of a 33-year-old man suffering from a generalized blistering skin disorder since birth. He also presented nail dystrophy and tooth abnormalities. Mucosal involvement was limited to gingival erosion. Alopecia was absent and body, axillary and pubic hair were normal. Immunofluorescence analysis showed a markedly reduced expression of BP180, electron microscopy studies evidenced hypoplastic hemidesmosomes and Northern blot analysis confirmed a striking decrease in the amount of BP180 mRNA. The clinical features of our patient confirm that BP180 deficiency usually results in a non-Herlitz JEB form. However, the degree of skin, mucous membranes and hair involvement appears more variable and less typical than originally described for GABEB.

Compound heterozygosity for an out-of-frame deletion and a splice site mutation in the LAMB3 gene causes nonlethal junctional epidermolysis bullosa.

Laminin-5 is the major adhesion ligand of epithelial cells. Mutations in the genes encoding laminin-5 cause junctional epidermolysis bullosa (JEB), a clinically and genetically heterogeneous group of recessively inherited blistering disease of skin and mucous membranes. In this report, we describe a patient with a non-lethal variant of JEB who is a compound heterozygous for mutations affecting the LAMB3 gene. The paternally inherited mutation is a deletion of a single base (T) leading to a frameshift and premature termination codon. It results in mRNA decay. The maternally inherited mutation is a G-->A transition at the last base of exon 7 (628G-->A) which converts a codon for glutamic acid in a codon for lysine (E210K). The mutation 628G-->A alters the correct splicing of LAMB3 pre-mRNA giving rise to two aberrant mRNA, in addition to the RNA transcript carrying the G-->A substitution. This result is compatible with the reduced expression of mutated laminin 5 molecules with altered biological activity, and the mild JEB phenotype observed in the patient.