Evaluation of Hedgehog Pathway Inhibition on Nevoid Basal Cell Carcinoma Syndrome Fibroblasts and Basal Cell Carcinoma-Associated Fibroblasts: Are Vismodegib and Sonidegib Useful to Target Cancer-Prone Fibroblasts?

Simple Summary: Nevoid basal cell carcinoma syndrome (NBCCS) is a genetic disorder of autosomal dominant inheritance that dramatically predisposes a patient to the formation of basal cell carcinoma (BCC) due to causative mutations in several genes associated with the Hedgehog (Hh) pathway. Somatic mutations in this pathway are also associated with sporadic BCC, the most common form of skin cancer. Hh signalling extends its effect on tumorigenesis by modulating the tumour microenvironment in a paracrine fashion. Consistently, NBCCS fibroblasts could facilitate BCC occurrence. Here, we investigated vismodegib and sonidegib, two molecules currently used to target this pathway in cancer cells, as a therapeutic option against syndromic and BCC-associated fibroblasts.Activating mutations in the Hh pathway underlies the development of sporadic and familial skin BCC. For these oncogenic proliferations displaying ligand-independent activation of the intracellular pathway, two molecules have been approved for therapeutic purposes: vismodegib and sonidegib. Improper Hh signalling occurs in many human tumours also via a paracrine mechanism (ligand-dependent) in which the secretion of Hh ligands by stromal cells support tumour growth. On the other hand, the mobilization of neoplastic stroma by cancer cells is sustained by the activation of Hh signalling in surrounding fibroblasts suggesting a central role of this bidirectional crosstalk in carcinogenesis. Additionally, loss-of-function mutations in the PTCH1 gene in the context of NBCCS, an autosomal dominant disorder predisposing to multiple BCCs, determine tumour permissive phenotypes in dermal fibroblasts. Here, profiling syndromic and BCC-associated fibroblasts unveiled an extraordinary similarity characterized by overexpression of several Hh target genes and a marked pro-inflammatory outline. Both cell types exposed to Hh inhibitors displayed reversion of the tumour-prone phenotype. Under vismodegib and sonidegib treatment, the Wnt/beta-catenin pathway, frequently over-active in tumour stroma, resulted down-regulated by pAKT-GSK3 beta axis and consequent increase of beta-catenin turnover. Overall, this study demonstrated that vismodegib and sonidegib impacting on fibroblast tumour supportive functions might be considered in therapy for BCC independently to the mutation status of Hh components in neoplastic cells.