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

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/d^ex4 mice, whose Pparb/d gene was selectively deleted in fibroblasts, had delayed emergence and reduced tumor burden compared with control mice (Pparb/d^fl/fl). However, FSPCre-Pparb/d^ex4-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/d^ex4 mice compared with that in Pparb/d^fl/fl mice, prior to the first appearance of tumors in Pparb/d^fl/fl. Our study revealed a role for fibroblast PPARβ/δ in the epithelial-mesenchymal communication involved in cellular redox homeostasis.

SUBMITTER: Tan MWY

PROVIDER: S-EPMC7429869 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundCase-control studies have reported that exogenous estrogen use is associated with increased risk of skin cancer. The effects of menopausal hormone therapy on incidence of nonmelanoma skin cancer and melanoma were evaluated in post hoc analyses of the Women's Health Initiative randomized placebo-controlled hormone therapy trials of combined estrogen plus progestin (E + P) and estrogen only (E-alone).MethodsPostmenopausal women aged 50-79 years were randomly assigned to conjugated equine estrogen (0.625 mg/d) plus medroxyprogesterone acetate (2.5 mg/d) or placebo in the E + P trial if they had an intact uterus (N = 16,608) or to conjugated equine estrogen alone or placebo in the E-alone trial if they had a hysterectomy (N = 10,739); the mean follow-up was 5.6 and 7.1 years, respectively. Incident nonmelanoma skin cancers (n = 980 [E + P trial]; n = 820 [E-alone trial]) and melanomas (n = 57 [E + P trial]; n =38 [E-alone trial]) were ascertained by self-report. Incident cases of cutaneous malignant melanoma were confirmed by physician review of medical records. Incidences of nonmelanoma skin cancer and melanoma were compared between the two randomization groups within each trial using hazard ratios (HRs), with corresponding 95% confidence intervals (CIs) and Wald statistic P values from Cox proportional hazards models. All statistical tests were two-sided.ResultsRates of incident nonmelanoma skin cancer and melanoma were similar between the active hormone (combined analysis of E + P and E-alone) and placebo groups (nonmelanoma skin cancer: HR = 0.98, 95% CI = 0.89 to 1.07; melanoma: HR = 0.92, 95% CI = 0.61 to 1.37). Results were similar for the E + P and E-alone trials when analyzed individually.ConclusionsMenopausal hormone therapy did not affect overall incidence of nonmelanoma skin cancer or melanoma. These findings do not support a role of menopausal estrogen, with or without progestin, in the development of skin cancer in postmenopausal women.

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

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