Overexpression of Desmoglein 2 in a mouse model of Gorlin syndrome enhances spontaneous basal cell carcinoma formation through STAT3-mediated Gli1 expression

Activation of the Hedgehog (Hh) pathway is causative of virtually all sporadic and Gorlin syndrome-related basal cell carcinomas (BCC), with loss of function of Patched1 (Ptc1) being the most common genomic lesion. Sporadic BCCs also overexpress desmoglein-2 (Dsg2), a desmosomal cadherin normally found in the basal layer. Using a mouse model of Gorlin syndrome (Ptc1+/lacZ mice), we found that overexpressing Dsg2 in the basal layer (K14-Dsg2/Ptc1+/lacZ) or the superficial epidermis (Inv-Dsg2/Ptc1+/lacZ mice) resulted in increased spontaneous BCC formation at 3 and 6 months, respectively. The tumors did not show loss of heterozygosity of Ptc1, despite high levels of Gli1 and phosphorylated Stat3. A panel of sporadic human BCCs showed increased staining of both Dsg2 and P-Stat3 in 9/9 samples. Overexpression of Dsg2 in ASZ001 cells, a Ptc1-/- BCC cell line, induced Stat3 phosphorylation and further increased Gli1 levels, both in an autocrine and paracrine manner. Three different Stat3 inhibitors reduced viability and Gli1 expression in ASZ001 cells, but not in HaCaT cells. Conversely, stimulation of Stat3 in ASZ001 cells with IL-6 increased Gli1 expression. Our results indicate that Dsg2 enhances canonical Hh signaling downstream of Ptc1 to promote BCC development through the activation of P-Stat3 and regulation of Gli1 expression

Patients with recessive dystrophic epidermolysis bullosa develop squamous-cell carcinoma regardless of type VII collegen expression.

Recent data suggest that individuals with recessive dystrophic epidermolysis bullosa (RDEB) only develop squamous-cell carcinoma (SCC) in the presence of the NC1 domain of type VII collagen. This conclusion was based on experimental work in which cryosections of SCCs from 10 people with RDEB all showed positive type VII collagen immunostaining and observations in a murine model of SCC development in which tumors only occurred using keratinocytes from RDEB subjects that expressed detectable levels of the NC1 domain of the type VII collagen protein. To assess whether the clinical interpretation was valid in another cohort of RDEB patients, we examined expression of type VII collagen in 17 SCC tumors excised from 11 patients. Indirect immunofluorescent staining of SCC cryosections and Western blotting of cultured keratinocyte lysates identified two RDEB individuals who did not express detectable levels of type VII collagen. Mutation analysis revealed that these two patients harbor compound heterozygous nonsense mutations within the region of the COL7A1 gene encoding the NC1 domain. These data suggest that individuals with RDEB can develop SCC regardless of type VII collagen expression and that additional factors have a role in explaining the high incidence of tumors complicating this genodermatosis