C-terminal cleavage of DeltaNp63alpha is associated with TSA-induced apoptosis in immortalized corneal epithelial cells

The foggy world(s) of p63 isoform regulation in normal cells and cancer

The p53 family member p63 exists as two major protein variants (TAp63 and ΔNp63) with distinct expression patterns and functional properties. Whilst downstream target genes of p63 have been studied intensively, how p63 variants are themselves controlled has been relatively neglected. Here, we review advances in understanding ΔNp63 and TAp63 regulation, highlighting their distinct pathways. TAp63 has roles in senescence and metabolism, and in germ cell genome maintenance, where it is activated post-transcriptionally by phosphorylation cascades after DNA damage. The function and regulation of TAp63 in mesenchymal and haematopoietic cells is less clear but may involve epigenetic control through DNA methylation. ΔNp63 functions to maintain stem/progenitor cells in various epithelia and is overexpressed in squamous and certain other cancers. ΔNp63 is transcriptionally regulated through multiple enhancers in concert with chromatin modifying proteins. Many signalling pathways including growth factors, morphogens, inflammation, and the extracellular matrix influence ΔNp63 levels, with inconsistent results reported. There is also evidence for reciprocal regulation, including ΔNp63 activating its own transcription. ΔNp63 is downregulated during cell differentiation through transcriptional regulation, while post-transcriptional events cause proteasomal degradation. Throughout the review, we identify knowledge gaps and highlight discordances, providing potential explanations including cell-context and cell-matrix interactions. Identifying individual p63 variants has roles in differential diagnosis and prognosis, and understanding their regulation suggests clinically approved agents for targeting p63 that may be useful combination therapies for selected cancer patients. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Cultivation and characterization of pterygium as an ex vivo study model for disease and therapy

PURPOSE

Development of ex vivo model to study pathogenesis, inflammation and treatment modalities for pterygium.

METHODS

Pterygium obtained from surgery was cultivated (3 months). Gravitational attachment method using viscoelastic facilitated adherence of graft and outgrowing cells. Medium contained serum as the only growth supplement with no use of scaffolds. Surface profiling of the multi-layered cells for hematopoietic- and mesenchymal stem cell markers was performed. Examination of cells by immunohistochemistry using pluripotency, oxidative stress, stemness, migration and proliferation, epithelial and secretory markers was performed. The effect of anti-proliferative agent Mitomycin C upon secretion of pro-inflammatory cytokines IL-6 and IL-8 was assessed.

RESULTS

Cells showed high expression of migration- (CXCR4), secretory- (MUC1, MUC4) and oxidative damage- (8-OHdG) markers, and low expression of hypoxia- (HIF-1α) and proliferation- (Ki-67) markers. Moderate and low expression of the pluripotency markers (Vimentin and ΔNp63) was present, respectively, while the putative markers of stemness (Sox2, Oct4, ABCG-2) and epithelial cell markers- (CK19, CK8-18) were weak. The surface marker profile of the outgrowing cells revealed high expression of the hematopoietic marker CD47, mesenchymal markers CD90 and CD73, minor or less positivity for the hematopoietic marker CD34, mesenchymal marker CD105, progenitor marker CD117 and attachment protein markers while low levels of IL-6 and IL-8 secretion ex vivo, were inhibited upon Mitomycin C treatment.

CONCLUSION

Ex vivo tissue engineered pterygium consists of a mixture of cells of different lineage origin, suitable for use as a disease model for studying pathogenesis ex vivo, while opening possibilities for new treatment and prevention modalities.

Trichostatin A inhibits collagen synthesis and induces apoptosis in keloid fibroblasts

Keloid, a fibro-proliferative benign tumor of skin, is characterized by an enriched milieu of growth factors and an abundant accumulation of extracellular matrix (ECM). Transforming growth factor (TGF)-β1 is well known as the crucial fibrogenic cytokine promoting ECM production and tissue fibrosis in keloid forming. Epigenetic modifications have been shown to play a role in the pathogenesis of cancer as well as autoimmune and inflammatory disorders. Recent publication reports epigenetic modifications in keloid fibroblasts that include an altered pattern of DNA methylation and histone acetylation. Therefore, the field of epigenetics may provide a new therapeutic idea for keloid treatment strategies. Currently, there is some evidence from experimental studies that histone deacetylase (HDAC) inhibitor Trichostatin A (TSA) causes abrogation of TGF-β1 induced collagen synthesis in skin fibroblasts. Furthermore, TSA could suppress proliferation and induce apoptosis in a broad spectrum of tumor cells both in vitro and in vivo. These findings suggest that TSA could also cause abrogation of TGF-β1 induced collagen synthesis and induce apoptosis of proliferating keloid fibroblasts.