Faculty Bibliography

The pathogenesis of BCC is associated with sonic hedgehog (SHH) signaling. Vismodegib, a smoothened inhibitor that targets this pathway, is now in clinical use for advanced BCC patients, but its efficacy is limited. Therefore, new therapeutic options for this cancer are required. We studied gene expression profiling of BCC tumour tissues coupled with laser capture microdissection to identify tumour specific receptor tyrosine kinase expression that can be targeted by small molecule inhibitors. We found a >250 fold increase (FDR<10-4) of the oncogene, anaplastic lymphoma kinase (ALK) as well as its ligands, pleiotrophin and midkine in BCC compared to microdissected normal epidermis. qRT-PCR confirmed increased expression of ALK (p<0.05). Stronger expression of phosphorylated ALK in BCC tumour nests than normal skin was observed by immunohistochemistry. Crizotinib, an FDA-approved ALK inhibitor, reduced keratinocyte proliferation in culture, whereas a c-Met inhibitor did not. Crizotinib significantly reduced the expression of GLI1 and CCND2 (members of SHH-pathway) mRNA by approximately 60% and 20%, respectively (p<0.01). Our data suggest that ALK may increase GLI1 expression in parallel with the conventional SHH-pathway and promote keratinocyte proliferation. Hence, an ALK inhibitor alone or in combination with targeting SHH-pathway molecules may be a potential treatment for BCC patients.

Organ transplant recipients suffer from an increased incidence and recurrence rate of nonmelanoma skin cancers. These cancers are often more aggressive than those in the general population, resulting in significant morbidity and mortality. Often times, routine treatment modalities are not adequate and the use of different management strategies is necessary. Treatment modalities, including surgical excision, Mohs micrographic surgery, physically destructive modalities, topical therapy, and photodynamic therapy may be used. Combinations of these therapies may be used in rotation for treatment of extensive field disease. Chemoprophylaxis with oral retinoids and alteration of the immune suppression regimen may be indicated for specific cases. In addition, newly emerging therapies for squamous cell carcinomas including cetuximab and capecitabine may offer heightened control in organ transplant patients with significant cutaneous disease.

The development of vismodegib and its recent approval by the United States Food and Drug Administration for use in patients with locally advanced or metastatic basal cell carcinoma (BCC) carries with it a renewed sense of optimism. Once BCC has progressed to an advanced, or so-called inoperable stage, there has been a paucity of effective therapies, making the new small molecule inhibitors targeting the hedgehog pathway particularly hopeful prospects. In order to better understand the utility of these new treatments, it is important to assess the existing economic, physical, and psychological burden of advanced BCC. This review aims to recognize the impact of inoperable and metastatic BCC, as well as to better characterize the various types of advanced BCC. The use of vismodegib as a prophylactic treatment in patients with basal cell nevus syndrome is also addressed, including possible adverse events, tumor resistance, and new onset malignancies.

During wound healing, stem cells provide functional mature cells to meet acute demands for tissue regeneration. Simultaneously, the tissue must maintain a pool of stem cells to sustain its future regeneration capability. However, how these requirements are balanced in response to injury is unknown. Here we demonstrate that after wounding or ultraviolet type B irradiation, melanocyte stem cells (McSCs) in the hair follicle exit the stem cell niche before their initial cell division, potentially depleting the pool of these cells. We also found that McSCs migrate to the epidermis in a melanocortin 1 receptor (Mc1r)-dependent manner and differentiate into functional epidermal melanocytes, providing a pigmented protective barrier against ultraviolet irradiation over the damaged skin. These findings provide an example in which stem cell differentiation due to injury takes precedence over stem cell maintenance and show the potential for developing therapies for skin pigmentation disorders by manipulating McSCs.