Dataset Information

Deletion of 14-3-3σ sensitizes mice to DMBA/TPA-induced papillomatosis.

ABSTRACT: The p53-inducible cell cycle regulator 14-3-3σ exhibits tumor suppressive functions and is highly expressed in differentiating layers of the epidermis and hair follicles. 14-3-3σ/SFN/stratifin is frequently silenced in human epithelial cancers, and experimental down-regulation of 14-3-3σ expression immortalizes primary human keratinocytes. In the repeated-epilation (ER) mouse model, a heterozygous nonsense mutation of 14-3-3σ causes repeated hair-loss, hyper-proliferative epidermis, and spontaneous development of papillomas and squamous cell carcinomas in aging mice. Therefore, loss of 14-3-3σ function might contribute to epithelial tumor development. Here, we generated mice with loxP sites surrounding the single 14-3-3σ exon which allowed Cre-mediated deletion of the gene. 14-3-3σ-deficient mice are viable, but demonstrate a permanently disheveled fur. However, histological analyses of the skin did not reveal obvious defects in the hair follicles or the epidermis. Deletion of 14-3-3σ did not enhance spontaneous epidermal tumor development, whereas it increased the frequency and size of DMBA/TPA-induced papillomas. In conclusion, 14-3-3σ is dispensable for normal epidermal homeostasis but critical for suppression of chemically-induced skin carcinogenesis. In addition, these results suggest that the ER mutation of 14-3-3σ is not equivalent to loss of 14-3-3σ, but may represent a gain-of-function variant, which does not reflect the organismal function of wild-type 14-3-3σ.

SUBMITTER: Winter M

PROVIDER: S-EPMC5216908 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Deletion of 14-3-3σ sensitizes mice to DMBA/TPA-induced papillomatosis.

Winter Markus M Lodygin Dmitri D Verdoodt Berlinda B Hermeking Heiko H

Oncotarget 20160701 30

The p53-inducible cell cycle regulator 14-3-3σ exhibits tumor suppressive functions and is highly expressed in differentiating layers of the epidermis and hair follicles. 14-3-3σ/SFN/stratifin is frequently silenced in human epithelial cancers, and experimental down-regulation of 14-3-3σ expression immortalizes primary human keratinocytes. In the repeated-epilation (ER) mouse model, a heterozygous nonsense mutation of 14-3-3σ causes repeated hair-loss, hyper-proliferative epidermis, and spontane ...[more]

PMID: 27409835

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Project description:The study tested the hypothesis that apoptosis can prevent and control growth of neoplastic cells. Previous studies in-vitro have shown that the pro-apoptotic P2X(7) receptor regulates growth of epithelial cells. The specific objective of the present study was to understand to what degree the P2X(7) system controls development and growth of skin cancer in vivo, and what cellular and molecular mechanisms are involved in the P2X(7) action.Skin neoplasias in mice (papillomas, followed by squamous spindle-cell carcinomas) were induced by local application of DMBA/TPA. Experiments in-vitro utilized cultured epidermal keratinocytes generated from wild-type or from P2X(7)-null mice. Assays involved protein immunostaining and Western blots; mRNA real-time qPCR; and apoptosis (evaluated in situ by TUNEL and quantified in cultured keratinocytes as solubilized DNA or by ELISA). Changes in cytosolic calcium or in ethidium bromide influx (P2X(7) pore formation) were determined by confocal laser microscopy.(a) Co-application on the skin of the P2X7 specific agonist BzATP inhibited formation of DMBA/TPA-induced skin papillomas and carcinomas. At the completion of study (week 28) the proportion of living animals with cancers in the DMBA/TPA group was 100% compared to 43% in the DMBA/TPA+BzATP group. (b) In the normal skin BzATP affected mainly P2X(7)-receptor - expressing proliferating keratinocytes, where it augmented apoptosis without evoking inflammatory changes. (c) In BzATP-treated mice the degree of apoptosis was lesser in cancer than in normal or papilloma keratinocytes. (d) Levels of P2X(7) receptor, protein and mRNA were 4-5 fold lower in cancer tissues than in normal mouse tissues. (e) In cultured mouse keratinocytes BzATP induced apoptosis, formation of pores in the plasma membrane, and facilitated prolonged calcium influx. (f) The BzATP-induced apoptosis, pore-formation and augmented calcium influx had similar dose-dependence for BzATP. (g) Pore formation and the augmented calcium influx were depended on the expression of the P2X(7) receptor, while the BzATP-induced apoptosis depended on calcium influx. (h) The BzATP-induced apoptosis could be blocked by co-treatment with inhibitors of caspase-9 and caspase-3, but not of caspase-8.(a) P2X(7)-dependent apoptosis is an important mechanism that controls the development and progression of epidermal neoplasia in the mouse. (b) The P2X(7)-dependent apoptosis is mediated by calcium influx via P2X(7) pores, and involves the caspase-9 (mitochondrial) pathway. (c) The diminished pro-apoptotic effect of BzATP in mouse cancer keratinocytes is possibly the result of low expression of the P2X(7) receptor. (d) Activation of P2X(7)-dependent apoptosis, e.g. with BzATP could be a novel chemotherapeutic growth-preventive modality for papillomas and epithelial cancers in vivo.

Project description:Silibinin, a major bioactive flavonolignan in Silybum marianum, has received considerable attention in view of its anticarcinogenic activity. The present study examines its anticancer potential against 7, 12-dimethylbenz(a)anthracene (DMBA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) induced skin cancer. Male LACA mice were randomly segregated into 4 groups: Control, DMBA/TPA, Silibinin and Silibinin+DMBA/TPA. Tumors in DMBA/TPA and Silibinin+DMBA/TPA groups were histologically graded as squamous cell carcinoma. In the Silibinin+DMBA/TPA group, significant reduction in tumor incidence (23%), tumor volume (64.4%), and tumor burden (84.8%) was observed when compared to the DMBA/TPA group. The underlying protective mechanism of Silibinin action was studied at pre-initiation (2 weeks), post-initiation (10 weeks) and promotion (22 weeks) stages of the skin carcinogenesis. The antioxidant nature of Silibinin was evident at the end of 2 weeks of its treatment. However, towards the end of 10 and 22 weeks, elevated lipid peroxidation (LPO) levels indicate the pro-oxidative nature of Silibinin in the cancerous tissue. TUNEL assay revealed enhanced apoptosis in the Silibinin+DMBA/TPA group with respect to the DMBA/TPA group. Therefore, it may be suggested that raised LPO could be responsible for triggering apoptosis in the Silibinin+DMBA/TPA group. 1H Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the metabolic profile of the skin /skin tumors. Dimethylamine (DMA), glycerophosphocholine (GPC), glucose, lactic acid, taurine and guanine were identified as the major contributors for separation between the groups from the Principal Component Analysis (PCA) of the metabolite data. Enhanced DMA levels with no alteration in GPC, glucose and lactate levels reflect altered choline metabolism with no marked Warburg effect in skin tumors. However, elevated guanine levels with potent suppression of taurine and glucose levels in the Silibinin+DMBA/TPA group are suggestive of the pro-oxidative nature of Silibinin in regressing tumors. Thus, supporting the theory of augmented LPO levels resulting in increased apoptosis in the skin tumors treated with Silibinin.

Dataset Information

Deletion of 14-3-3σ sensitizes mice to DMBA/TPA-induced papillomatosis.

Publications

Deletion of 14-3-3σ sensitizes mice to DMBA/TPA-induced papillomatosis.

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