Faculty Bibliography

PURPOSE: Irradiation of cancer cells can cause immunogenic death. We used mouse models to determine whether irradiation of melanoma can enhance the host antitumour immune response and function as an effective vaccination strategy, and investigated the molecular mechanisms involved in this radiation-induced response. MATERIALS AND METHODS: For in vivo studies, C57BL6/J mice and the B16F0 melanoma cell line were used in a lung metastasis model, intratumoural host immune activation assays, and tumour growth delay studies. In vitro studies included a dendritic cell (DC) phagocytosis assay, detection of cell surface exposure of the protein calreticulin (CRT), and small interfering RNA (siRNA)-mediated depletion of CRT cellular levels. RESULTS: Irradiation of cutaneous melanomas prior to their resection resulted in more than 20-fold reduction in lung metastases after systemic challenge with untreated melanoma cells. A syngeneic vaccine derived from irradiated melanoma cells also induced adaptive immune response markers in irradiated melanoma implants. Our data indicate a trend for radiation-induced increase in melanoma cell surface exposure of CRT, which is involved in the enhanced phagocytic activity of DC against irradiated melanoma cells (VIACUC). CONCLUSION: The present study suggests that neoadjuvant irradiation of cutaneous melanoma tumours prior to surgical resection can stimulate an endogenous anti-melanoma host immune response.

The transcription factor p63 belongs to a family of regulatory proteins that bind DNA in a sequence-specific manner, close to a target gene, to activate or repress its transcription. These proteins display a striking conservation of functional domains, but are differentially involved in regulating cellular processes. Nearly a decade after the discovery of p63, its critical role for proper epithelial development, maintenance and tumorigenesis is widely recognized. Several important cellular endpoints have been linked to p63 regulation in epithelium, including differentiation, cell fate specification, proliferation, survival, senescence, apoptosis, cell-cell and cell-matrix interaction programs. Although a large number of genes have been associated with p63-dependent regulation, only a few of these have been validated as direct p63 transcriptional targets. The challenge still remains to define the p63 transcriptome in epithelial cells, and to dissect the cellular mechanisms used to modulate the expression of this transcriptional profile. In this article we will review current knowledge regarding the basic mechanisms used by p63 to regulate gene expression. Also, we will discuss specific p63-regulated biological endpoints in epithelial cells and the specific genes that have been linked to p63 regulation in these particular contexts.

DeltaNp63alpha is a nuclear transcription factor that maintains epithelial progenitor cell populations, is overexpressed in several epithelial cancers, and can negatively regulate apoptosis. However, the mechanisms by which DeltaNp63alpha promotes cell survival are unclear. DeltaNp63alpha has been reported to act as a transcriptional repressor, but specific target genes directly repressed by DeltaNp63alpha remain unidentified. Here, we present evidence that DeltaNp63alpha functions to negatively regulate the proapoptotic protein IGFBP-3. Disruption of p63 expression in squamous epithelial cells increases IGFBP-3 expression, whereas ectopic expression of DeltaNp63alpha down-regulates IGFBP-3. DeltaNp63alpha binds to sites in the IGFBP-3 gene in vivo and can modulate transcription through these sites. Furthermore, DeltaNp63alpha and IGFBP-3 expression patterns are inversely correlated in normal squamous epithelium and squamous cell carcinomas. These data suggest that IGFBP-3 is a target of transcriptional repression by DeltaNp63alpha and that this repression represents a mechanism by which tumors that overexpress p63 may be protected from apoptosis.