Deficiency in fibroblast PPARβ/δ reduces nonmelanoma skin cancers in mice

Cell Death Differ. 2020 Sep;27(9):2668-2680. doi: 10.1038/s41418-020-0535-y. Epub 2020 Apr 20.

Abstract

The incidence of nonmelanoma skin cancer (NMSC) has been increasing worldwide. Most studies have highlighted the importance of cancer-associated fibroblasts (CAFs) in NMSC progression. However much less is known about the communication between normal fibroblasts and epithelia; disruption of this communication affects tumor initiation and the latency period in the emergence of tumors. Delineating the mechanism that mediates this epithelial-mesenchymal communication in NMSC could identify more effective targeted therapies. The nuclear receptor PPARβ/δ in fibroblasts has been shown to modulate adjacent epithelial cell behavior, however, its role in skin tumorigenesis remains unknown. Using chemically induced skin carcinogenesis, we showed that FSPCre-Pparb/dex4 mice, whose Pparb/d gene was selectively deleted in fibroblasts, had delayed emergence and reduced tumor burden compared with control mice (Pparb/dfl/fl). However, FSPCre-Pparb/dex4-derived tumors showed increased proliferation, with no difference in differentiation, suggesting delayed tumor initiation. Network analysis revealed a link between dermal Pparb/d and TGF-β1 with epidermal NRF2 and Nox4. In vitro investigations showed that PPARβ/δ deficiency in fibroblasts increased epidermal Nox4-derived H2O2 production, which triggered an NRF2-mediated antioxidant response. We further showed that H2O2 upregulated NRF2 mRNA via the B-Raf-MEK1/2 pathway. The enhanced NRF2 response altered the activities of PTEN, Src, and AKT. In vivo, we detected the differential phosphorylation profiles of B-Raf, MEK1/2, PTEN, Src, and AKT in the vehicle-treated and chemically treated epidermis of FSPCre-Pparb/dex4 mice compared with that in Pparb/dfl/fl mice, prior to the first appearance of tumors in Pparb/dfl/fl. Our study revealed a role for fibroblast PPARβ/δ in the epithelial-mesenchymal communication involved in cellular redox homeostasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carcinogenesis / metabolism
  • Carcinogenesis / pathology
  • Epidermis / pathology
  • Fibroblasts / metabolism*
  • Fibroblasts / pathology*
  • Gene Regulatory Networks
  • Glycoproteins / metabolism
  • Keratinocytes / metabolism
  • Kinetics
  • Melanoma / metabolism
  • Melanoma / pathology
  • Mice, Transgenic
  • NADPH Oxidase 4 / metabolism
  • NF-E2-Related Factor 2 / metabolism
  • Neoplasm Proteins / metabolism
  • PPAR delta / deficiency*
  • PPAR delta / metabolism
  • PPAR-beta / deficiency*
  • PPAR-beta / metabolism
  • Phosphorylation
  • Reactive Oxygen Species / metabolism
  • Signal Transduction
  • Skin Neoplasms / genetics
  • Skin Neoplasms / metabolism*
  • Skin Neoplasms / pathology*
  • Transforming Growth Factor beta1 / metabolism
  • Tumor Burden

Substances

  • Glycoproteins
  • LRG1 protein, mouse
  • NF-E2-Related Factor 2
  • Neoplasm Proteins
  • Nfe2l2 protein, mouse
  • PPAR delta
  • PPAR-beta
  • Reactive Oxygen Species
  • Transforming Growth Factor beta1
  • NADPH Oxidase 4
  • Nox4 protein, mouse