Anchorless keratinocyte survival: an emerging pathogenic mechanism for squamous cell carcinoma in recessive dystrophic epidermolysis bullosa

Type VII Collagen Deficiency in the Oncogenesis of Cutaneous Squamous Cell Carcinoma in Dystrophic Epidermolysis Bullosa

Dystrophic epidermolysis bullosa is a rare genetic skin disorder caused by COL7A1 sequence variations that result in type VII collagen deficits and cutaneous and extracutaneous manifestations. One serious complication of dystrophic epidermolysis bullosa is cutaneous squamous cell carcinoma, a leading driver of morbidity and mortality, especially among patients with recessive dystrophic epidermolysis bullosa. Type VII collagen deficits alter TGFβ signaling and evoke multiple other cutaneous squamous cell carcinoma progression-promoting activities within epidermal microenvironments. This review examines cutaneous squamous cell carcinoma pathophysiology in dystrophic epidermolysis bullosa with a focus on known oncogenesis pathways at play and explores the idea that therapeutic type VII collagen replacement may reduce cutaneous squamous cell carcinoma risk.

Squamous Cell Carcinoma in Patients with Inherited Epidermolysis Bullosa: Review of Current Literature

Epidermolysis bullosa (EB) is a group of rare congenital diseases caused by mutations in structural proteins of the dermal/epidermal junction that are characterized by extreme epithelial fragility, which determines the formation of bullae and erosions either spontaneously or after local mechanical traumas. In EB patients, skin fragility leads to many possible complications and comorbidities. One of the most feared complications is the development of cutaneous squamous cell carcinomas (SCCs) that particularly in the dystrophic recessive EB subtype can be extremely aggressive and often metastatic. SCCs in EB patients generally arise more often in the extremities, where chronic blisters and scars are generally located. SCCs represent a big therapeutic challenge in the EB population. No standard of care exists for the treatment of SCC in these patients, and therapy is based on small case studies. Moreover, the pathogenesis of cSCC in EB patients is still unclear. Many theories have been indeed postulated in order to explain why cSCC behaves so much more aggressively in EB patients compared to the general population. cSCC in EB seems to be the result of many complex interactions among cancer cells, skin microenvironment, susceptibility to DNA mutations and host immune response. In this review, we analyze the different pathogenetic mechanisms of cSCC in EB patients, as well as new therapies for this condition.

Treatment of skin cancers in epidermolysis bullosa

Squamous cell carcinomas (SCCs) are highly aggressive in patients with epidermolysis bullosa (EB). Non-ultraviolet-related SCCs are the leading cause of death in patients with recessive dystrophic EB, particularly recessive dystrophic EB-generalized severe subtype (RDEB-GS). The mechanism of SCC development in patients with RDEB continues to be investigated and several theories have been reported in the literature.

Type VII collagen: the anchoring fibril protein at fault in dystrophic epidermolysis bullosa

Type VII collagen is a major component of the anchoring fibrils of the dermal-epidermal adhesion on the dermal side at the lamina densa/papillary dermis interface. Dystrophic epidermolysis bullosa (DEB) emerged as a candidate for type VII collagen mutations becausing anchoring fibrils were shown to be morphologically altered, reduced in number, or completely absent in patients with different forms of DEB. Circulating autoantibodies recognize type VII collagen epitopes in epidermolysis bullosa acquisita. The suggestion that type VII collagen is required for human epidermal tumorigenesis relates to the increasing numbers of life-threatening complications associated with developing squamous cell carcinomas because of the extended life span of affected individuals with recessive DEB.

An in vitro three-dimensional model of primary human cutaneous squamous cell carcinoma

Squamous cell carcinomas (SCC) represent a substantial clinical problem because of increases, frequent recurrences and successive de novo tumors, especially in organ transplant recipients. To improve upon the current surgical and other non-selective therapies, a validated organotypic in vitro model of primary human SCC needs to be developed. Such a model will have obvious advantages over current cell line and animal based approaches, and may render the latter partly obsolete. In a first approach, an explant technique of primary SCC biopsies onto dermal constructs was used to emulate tumor expansion in an in vitro model. Histological analysis revealed the formation of nests of squamous cells, mimicking an invasive morphological feature of primary SCC. Immunohistochemical analysis comprised an array of markers characteristic of keratinocyte (hyper) proliferation (K6, K16, K17 and Ki67), differentiation (K1, K10 and involucrin), basement membrane (collagen types IV and VII, integrins alpha(6) and beta(4) and laminin 332) and SCC (K4, K13 and Axl). The generated human SCC models displayed disturbed differentiation and keratins associated with hyperproliferation, but a low frequency of Ki67 positive cells. Basement membrane composition of the in vitro SCC model resembled that of normal skin. These results show for the first time that in vitro modelling of three-dimensional growth of primary cutaneous human SCC is feasible. This model may provide a platform to develop refined preventive and curative treatments and thereby gain understanding of SCC pathogenesis.

Mutation analysis and characterization of COL7A1 mutations in dystrophic epidermolysis bullosa

Dystrophic epidermolysis bullosa (DEB) is inherited in both an autosomal dominant DEB and autosomal recessive manner RDEB, both of which result from mutations in the type VII collagen gene (COL7A1). To date, 324 pathogenic mutations have been detected within COL7A1 in different variants of DEB; many mutations are clustered in exon 73 (10.74%) which is close to the 39 amino acid interruption region. Dominant dystrophic epidermolysis bullosa usually involves glycine substitutions within the triple helix of COL7A1 although other missense mutations, deletions or splice-site mutations may underlie some cases. In recessive dystrophic epidermolysis bullosa, the mutations include nonsense, splice site, deletions or insertions, 'silent' glycine substitutions within the triple helix and non-glycine missense mutations within the triple helix or non-collagenous NC-2 domain. The nature of mutations in COL7A1 and their positions correlate reasonably logically with the severity of the resulting phenotypes.

Recessive dystrophic epidermolysis bullosa-associated squamous-cell carcinoma: an enigmatic entity with complex pathogenesis

Expression of either collagen VII or the noncollagenous (NC1) fragment derived from it has been suggested to be indispensable for the development of squamous-cell carcinomas (SCCs) in patients affected by recessive dystrophic epidermolysis bullosa (RDEB). This view is challenged here by the observation that SCCs do develop in RDEB patients lacking expression of collagen VII altogether. The aggressive behavior of RDEB-associated SCCs remains unexplained.