Skin Carcinogenesis Research Articles

Efficacy of sulforaphane in skin cancer animal models: A systematic review.

Globally, skin cancer is the predominant form of cancer, with melanoma identified as its most deadly variant. Projections suggest a surge exceeding 50% in melanoma occurrences by 2040, underscoring the urgency for preventive interventions. Sulforaphane (SFN), a compound found in cruciferous vegetables, is recognized for its cancer-preventive capabilities, particularly against skin cancer. This study employed a rigorous systematic review of various databases, adhering to predefined inclusion criteria for study selection. Data extraction was conducted using a uniform template, and the quality of the included studies was evaluated through the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) risk of bias tool, specifically designed for animal research. The review encompasses studies published in English from 2000 to 2023, culminating in the inclusion of 9 pertinent studies. The findings highlight SFN's capacity to act as a protective agent in preventing skin cancer in animal models. It demonstrated efficacy in curbing skin tumorigenesis triggered by assorted carcinogens, reducing the onset of skin tumors and impeding the growth and spread of skin cancer cells. Furthermore, SFN showed preventive effects against UVB-induced skin carcinogenesis by obstructing the activator protein 1 signaling pathway. Based on evidence from animal-based research, SFN emerges as a promising chemopreventive substance against skin cancer. Nevertheless, determining its optimal dosage, application duration and method of administration for human subjects remains pending. If its effectiveness is substantiated, SFN could complement or offer an alternative to existing preventive measures against skin cancer.

Disabled 2 (Dab2) Regulates Tumour Progression in Skin Squamous Cell Carcinoma.

Dab2 is an endocytic adaptor protein involved in various physiological processes and signaling pathways. Dab2 is deregulated in various cancers; however, its role in skin squamous cell carcinoma ( SCC) has not been elucidated yet. In the present study, we used the DMBA/TPA induced murine skin carcinogenesis model to examine the role of Dab2 in skin tumour progression. We generated tamoxifen inducible Dab2 conditional knockout system for our study. Loss of Dab2 led to delayed papilloma initiation and reduced papilloma burden. Delayed papilloma initiation was due to reduce proliferative potential of the papillomas due to Dab2 loss. Furthermore, while the WT papillomas progressed to SCC, the papillomas formed in Dab2 cKO mice failed to undergo malignant conversion to SCC. Dab2 cKO tumours showed reduced expression of K8, a marker for aggressive tumour. Moreover, Dab2 ckO tumours failed to undergo EMT as shown by reduced expression of Vimentin and Twist1. Dab2 cKO tumours also showed reduced expression of Sox2, a stem cell marker. Furthermore, qPCR analysis showed upregulation of Dab2 expression in the human skin cancer cell lines as compared to normal human skin keratinocytes. In patients, TCGA data analysis of skin cancer melanoma (SKCM) showed a trend where high levels of Dab2 correlated with poor overall survival. The present study shows that Dab2 promotes tumour progression in skin SCC.

STIL overexpression shortens lifespan and reduces tumor formation in mice.

Centrosomes are the major microtubule organizing centers of animal cells. Supernumerary centrosomes are a common feature of human tumors and associated with karyotype abnormalities and aggressive disease, but whether they are cause or consequence of cancer remains controversial. Here, we analyzed the consequences of centrosome amplification by generating transgenic mice in which centrosome numbers can be increased by overexpression of the structural centrosome protein STIL. We show that STIL overexpression induces centrosome amplification and aneuploidy, leading to senescence, apoptosis, and impaired proliferation in mouse embryonic fibroblasts, and microcephaly with increased perinatal lethality and shortened lifespan in mice. Importantly, both overall tumor formation in mice with constitutive, global STIL overexpression and chemical skin carcinogenesis in animals with inducible, skin-specific STIL overexpression were reduced, an effect that was not rescued by concomitant interference with p53 function. These results suggest that supernumerary centrosomes impair proliferation in vitro as well as in vivo, resulting in reduced lifespan and delayed spontaneous as well as carcinogen-induced tumor formation.

Antioxidant and Chemopreventive Potential of Uraria picta Root Extracts against DMBA/croton Oil Induced Skin Carcinogenesis in Mice

Antioxidant and Chemopreventive Potential of Uraria picta Root Extracts against DMBA/croton Oil Induced Skin Carcinogenesis in Mice

P2RY6 deletion promotes UVB-induced skin carcinogenesis by activating the PI3K/AKT signal pathway.

Our previous research has demonstrated that P2RY6 functions as an oncogene in DMBA/TPA-induced two-stage chemical skin carcinogenesis in mice. However, considering that human skin cancer is predominantly attributed to UV radiation from sunlight, additional investigations are needed to elucidate the role of P2RY6 in UVB-induced skin carcinogenesis. Surprisingly, we found that P2ry6-deficient mice exhibited marked promotion to UVB-induced skin papilloma formation compared with wild-type mice, suggesting its tumor-suppressive role in UVB-induced skin cancer. Additionally, a P2ry6 gene knockout promoted skin hyperplasia induced by short-term UVB irradiation, while UDP, the ligand of P2RY6, could inhibit the short-term UVB-induced increase of epiderma thickness in mouse skin. Furthermore, UVB irradiation could significantly upregulate P2RY6 expression in human and mouse skin cells. These results indicated that P2RY6 may play a crucial protective role in resisting the UVB-induced formation of skin tumors. At the molecular level, the loss of the P2RY6 gene inhibits the ubiquitination modification and expression of XPC after UVB irradiation in skin keratinocytes, resulting in the accumulation of CPDs (cyclobutane pyrimidine dimers). We have also demonstrated that P2RY6 deletion activates the PI3K/AKT signaling pathway both invitro and invivo. The CPD accumulation and acute inflammatory response enhanced by the loss of the P2RY6 gene can be reversed by an AKT inhibitor. These findings suggest that P2RY6 may act as a tumor suppressor in UVB-induced skin cancer by regulating the PI3K/AKT signaling pathway.

New Formulations of Acyclothymidine Dinucleosides Reduce Damaging Effects of Ultraviolet Radiation in an Ex Vivo Skin Model.

The greatest risk factor for skin cancer is exposure to ultraviolet (UV) rays of the sun. Among the three types of solar radiation (UVA, UVB, UVC), UVB rays are most commonly associated with skin cancer. UVB exposure promotes the formation of cyclobutane pyrimidine dimers (CPDs) in the DNA of cells in the epidermal skin layers, which can lead to mutations as DNA repair machinery attempts to repair the damage. These mutations can lead directly to skin carcinogenesis. Previous studies in animal and in human ex vivo skin models have shown that topical application of acyclothymidine dinucleosides protects DNA from UV-induced damage by preventing the formation of CPDs and helps initiate repair through the activation of DNA repair enzymes. Here we review the biological evidence leading to the development and formulation of ProteXidineTM (Topix Pharmaceuticals, Inc., Amityville, NY), as a UV protective agent for topical human application. We also provide clinical data pertaining to four ProteXidineTM formulations (test materials 1-4) tested for their abilities to reduce CPDs in an ex vivo human skin tissue model. J Drugs Dermatol. 2024;23(11):953-956. doi:10.36849/JDD.8420.

Penentuan Kadar Flavonoid dan Kandungan Fitokimia Ekstrak Kulit Bawang Merah (Allium cepa L) dengan Berbantukan Microwave sebagai Potensi Bahan Aktif Tabir Surya

The skin serves as a protective barrier against dust and ultraviolet (UV) radiation. Excessive UV exposure is associated with accelerated skin aging, erythema, hyperpigmentation, and carcinogenesis. This study aimed to quantify flavonoid concentrations and characterize phytochemical constituents in shallot skin extracts for their potential as active ingredients in sunscreen formulations. Shallot skin was subjected to microwave assisted extraction using 70% ethanol as the solvent. Phytochemical screening revealed the presence of flavonoids, tannins, saponins, and alkaloids in the extract. Flavonoid content was determined via UV-Vis spectrophotometry, yielding 36.33 mgQE/g. The high flavonoid concentration observed in shallot skin extract suggests its potential efficacy as an active ingredient in sunscreen formulations.

BRAF Inhibition and UVB Light Synergistically Promote Mus musculus Papillomavirus 1-Induced Skin Tumorigenesis.

The development of keratinocytic skin tumors, presumably attributable to paradoxical activation of the MAPK pathway, represents a relevant side effect of targeted therapies with BRAF inhibitors (BRAFis). The role of cutaneous papillomavirus infection in BRAFi-associated skin carcinogenesis, however, is still inconclusive. Employing the Mus musculus papillomavirus 1 (MmuPV1) skin infection model, the impact of BRAFis and UVB exposure on papillomavirus induced skin tumorigenesis was investigated in immunocompetent FVB/NCrl mice. Systemic BRAF inhibition in combination with UVB light induced skin tumors in 62% of the MmuPV1-infected animals. In contrast, significantly fewer tumors were observed in the absence of either BRAF inhibition, UVB irradiation or virus infection, as demonstrated by lesional outgrowth in 20%, 5% and 0% of the mice, respectively. Combinatory exposure to BRAFis and UVB favored productive viral infection, which was shown by high numbers of MmuPV1 genome copies and E1^E4 spliced transcripts and an abundance of E6/E7 oncogene mRNA and viral capsid proteins. BRAF inhibition, but not viral infection or UVB light, activated ERK1/2, whereas γH2AX expression, inducible by UVB light, remained unaltered by BRAFis. These results provide experimental evidence that BRAF inhibition and UVB irradiation synergistically promote MmuPV1-induced skin tumor development in vivo. This indicates an alternative pathway by which papillomavirus skin infection may contribute to BRAFi-associated skin tumorigenesis.

14-3-3σ/Stratifin and p21 limit AKT-related malignant progression in skin carcinogenesis following MDM2-associated p53 loss.

To study mechanisms driving/inhibiting skin carcinogenesis, stage-specific expression of 14-3-3σ (Stratifin) was analyzed in skin carcinogenesis driven by activated rasHa/fos expression (HK1.ras/fos) and ablation of PTEN-mediated AKT regulation (K14.creP/Δ5PTENflx/flx). Consistent with 14-3-3σ roles in epidermal differentiation, HK1.ras hyperplasia and papillomas displayed elevated 14-3-3σ expression in supra-basal keratinocytes, paralleled by supra-basal p-MDM2166 activation and sporadic p-AKT473 expression. In bi-genic HK1.fos/Δ5PTENflx/flx hyperplasia, basal-layer 14-3-3σ expression appeared, and alongside p53/p21, was associated with keratinocyte differentiation and keratoacanthoma etiology. Tri-genic HK1.ras/fos-Δ5PTENflx/flx hyperplasia/papillomas initially displayed increased basal-layer 14-3-3σ, suggesting attempts to maintain supra-basal p-MDM2166 and protect basal-layer p53. However, HK1.ras/fos-Δ5PTENflx/flx papillomas exhibited increasing basal-layer p-MDM2166 activation that reduced p53, which coincided with malignant conversion. Despite p53 loss, 14-3-3σ expression persisted in well-differentiated squamous cell carcinomas (wdSCCs) and alongside elevated p21, limited malignant progression via inhibiting p-AKT1473 expression; until 14-3-3σ/p21 loss facilitated progression to aggressive SCC exhibiting uniform p-AKT1473. Analysis of TPA-promoted HK1.ras-Δ5PTENflx/flx mouse skin, demonstrated early loss of 14-3-3σ/p53/p21 in hyperplasia and papillomas, with increased p-MDM2166/p-AKT1473 that resulted in rapid malignant conversion and progression to poorly differentiated SCC. In 2D/3D cultures, membranous 14-3-3σ expression observed in normal HaCaT and SP1ras61 papilloma keratinocytes was unexpectedly detected in malignant T52ras61/v-fos SCC cells cultured in monolayers, but not invasive 3D-cells. Collectively, these data suggest 14-3-3σ/Stratifin exerts suppressive roles in papillomatogenesis via MDM2/p53-dependent mechanisms; while persistent p53-independent expression in early wdSCC may involve p21-mediated AKT1 inhibition to limit malignant progression.

Targeting PAK1 is effective against cutaneous squamous cell carcinoma in a syngenic mouse model.

By taking advantage of forward genetic analysis in mice, we have demonstrated that Pak1 plays a crucial role during DMBA/TPA skin carcinogenesis. Although Pak1 has been considered to promote cancer development, its overall function remains poorly understood. To clarify the functional significance of Pak1 in detail, we sought to evaluate the possible effect of an allosteric inhibitor against PAK1 (NVS-PAK1-1) on a syngeneic mouse model. To this end, we established two cell lines, 9AS1 and 19AS1, derived from DMBA/TPA-induced squamous cell carcinoma (SCC) that engrafted in FVB mice. Based on our present results, NVS-PAK1-1 treatment significantly inhibited the growth of tumors derived from 9AS1 and 19AS1 cells invitro and invivo. RNA-sequencing analysis on the engrafted tumors indicates that NVS-PAK1-1 markedly potentiates the epidermal cell differentiation and enhances the immune response in the engrafted tumors. Consistent with these observations, we found an expansion of Pan-keratin-positive regions and potentially elevated infiltration of CD8-positive immune cells in NVS-PAK1-1-treated tumors as examined by immunohistochemical analyses. Together, our present findings strongly suggest that PAK1 is tightly linked to the development of SCC, and that its inhibition is a promising therapeutic strategy against SCC.

Zinc oxide nanoparticles derived from Penicillium griseofulvum mitigate DMBA/TPA-promoted mice skin carcinogenesis by modulating NF-ĸB associated signalling.

This study investigates the synthesis of zinc oxide nanoparticles using Penicillium griseofulvum (ZnONPs-PG) and their potential role in preventing DMBA/TPA-induced skin cancer. The synthesis process involved using a 1-mM zinc acetate dihydrate as a precursor in P. griseofulvum. Various analytical techniques, including FTIR spectroscopy, UV-Vis, TEM, XRD, and DLS, were utilized to characterize the ZnONPs. The efficacy of ZnONPs-PG was then evaluated in a DMBA/TPA-induced skin cancer model. Mice were treated topically with DMBA/TPA in acetone (200μL) over 2weeks, with treatments continuing for 20weeks. Results showed 100% tumor occurrence, histological changes, elevated lipid peroxidation (LPO) levels, and decreased antioxidant levels in DMBA/TPA-treated mice. However, topical application of ZnONPs magnificently reverted the tumor occurrence, histological changes, elevated malanoldehyde and hydrogen peroxide levels; decreased antioxidant levels in DMBA/TPA-treated mice. ZnONPs-PG treatment suppressed the increased levels of inflammatory markers (COX-2, iNOS and NF-κB,) and cell proliferation markers (Cyclin-E1, Cyclin D1, VEGF, TGF-β1) exposed mice. In addition, ZnONPs-PG treatment decreased the DMBA/TPA-induced anti-apoptotic Bcl-2 protein and increasing the expression of pro-apoptotic markers (Bax and caspase 3) in skin tissues. Thus, ZnONPs-PG may prevent skin carcinogenesis through its potent antioxidant properties and inhibiting NF-κB-mediated inflammatory and proliferation pathways.

Development and evaluation of imiquimod-loaded nanoemulsion-based gel for the treatment of skin cancer

BackgroundThe human skin, as the body’s largest organ, is particularly sensitive to many chemical mutagens and carcinogens encountered in daily life. Skin cancer has become a notable global health concern, partly due to increased exposure to environmental pollutants and UV rays. Various treatments are available to treat skin cancer. Imiquimod is approved for the treatment of actinic keratosis and basal cell carcinoma. The present investigation aimed to develop nanoemulsion-based gel with imiquimod (2.5% w/w) and carbopol ultrez 10 NF using a modified method to enhance the solubility, permeation, and therapeutic effectiveness of imiquimod to treat skin cancer. Combinations of rose oil and oleic acid, with Tween 20/Propylene glycol as Smix, were used in the formulation. The formulation underwent evaluation for parameters such as % drug content, in vitro drug diffusion studies, viscosity, skin irritation, in vitro cytotoxicity assay (MTT assay) and the DMBA/ croton oil skin cancer in vivo model.ResultsThe formulation showed a minimum globule size of 118 nm, a zeta potential– 56.26 mV, a PDI of 0.378 and a drug content of 99.77%. In vitro drug release exhibited 45.00% of imiquimod release within 8 h, while approximately 34.32% release was found from the commercial cream. The imiquimod-loaded nanoemulsion-based gel showed significant cytotoxicity (p < 0.001) against the A431 cell line compared to Imiquad cream. The IC50 value of the imiquimod-loaded nanoemulsion-based gel was noted to be 10.76 ± 2.54 µg/mL. In vivo results showed a significant reduction in tumor incidence (16.66%), tumor volume (140.26 ± 3.48 mm3), tumor burden (5.50 mm3) and tumor mass (0.66 ± 0.05 g) compared with the DMBA/croton oil carcinogen treatment control group. Histopathological finding showed the absence of keratinized pearls, epidermal hyperplasia, and acanthosis in the formulation treated group.ConclusionThe results revealed that the nanoemulsion-based gel, with half the IMQ concentration of the commercial cream and incorporating Carbopol Ultrez 10NF, is a promising method for treating skin carcinogenesis. It potentially reduces dose-dependent side effects and demonstrating enhanced efficacy.Graphical abstract

AKT and PERP Show Higher Expression in Precancerous than in Malignant Skin Neoplasms: Profiling in an Animal Model of Sequential Skin Carcinogenesis.

The primary aim of this study was to evaluate the activation of the PERP and Akt oncogenes in the induction of skin cancer in FVB/N mice by a stepwise chemical process. Forty four-week-old female FVB/N mice were randomly divided into a control group (n = 8) and two experimental groups (group A: n = 16, group B: n = 16). In the study, the groups were subjected to a two-stage carcinogenesis procedure. This consisted of an initial application of 97.4 nmol DMBA to shaved skin on the back, followed by applications of 32.4 nmol TPA after thirteen weeks for group A and after twenty weeks for group B. The control group received no treatment. Skin conditions were monitored weekly for tumor development. At the end of the experiment, the animals were euthanized for further tissue sampling. Examination of the skin lesions in the experimental groups showed a correlation with tumor progression, ranging from dysplasia to carcinoma. Tumor samples were examined both histologically and immunohistochemically. Notably, and PERP expression was higher in precancerous than in malignant tumors. The differences in expression between precancerous and benign tumors provide further evidence of a role for PERP and Akt in the transition from benign to malignant states. Our findings underscore the critical roles of PERP and Akt in the pathogenesis of skin cancer and suggest their potential as biomarkers for early detection and targets for therapeutic intervention.

Genetic evolution of keratinocytes to cutaneous squamous cell carcinoma.

We performed multi-omic profiling of epidermal keratinocytes, precancerous actinic keratoses, and squamous cell carcinomas to understand the molecular transitions during skin carcinogenesis. Single-cell mutational analyses showed that most keratinocytes in normal skin had lower mutation burdens than melanocytes and fibroblasts, however keratinocytes with TP53 or NOTCH1 mutations had substantially higher mutation burdens, suggesting that these mutations prime keratinocytes for transformation by increasing their mutation rate. Mutational profiling and spatial transcriptomics on squamous cell carcinomas adjacent to actinic keratoses revealed TERT promoter and CDKN2A mutations emerging in actinic keratoses, whereas additional mutations inactivating ARID2 and activating the MAPK-pathway delineated the transition to squamous cell carcinomas. Spatial variation in gene expression patterns was common in both tumor and immune cells, with high expression of checkpoint molecules at the invasive front of tumors. In conclusion, this study documents key events during the evolution of cutaneous squamous cell carcinoma.

Sustained high expression of NRF2 inhibits cell apoptosis in arsenite-transformed human keratinocytes

Our previous study identified that nuclear factor-erythroid-2 p45-related factor 2 (NRF2) was activated in arsenite-induced tumorigenesis. However, the underlying mechanisms of NRF2 mediating apoptosis in arsenic-induced skin carcinogenesis remain unknown. This study explored the dynamic changes in apoptosis rate and the expression of apoptosis proteins in immortalized human keratinocytes (HaCaT) malignant transformation caused by 1.0 μM NaAsO2 at passages 0, 1, 7, 14, 21, 28, and 35. The result showed that the apoptosis rate decreased. The apoptosis-related proteins cleaved-caspase-3/caspase-3 ratio decreased in the later stages (passages 21, 28, and 35). Moreover, the expression of intrinsic ER stress pathway-related CHOP, ATF4, ATF6, and the intrinsic mitochondrial pathway-related Bax protein decreased in the later stages, while Bcl-2 and Mcl-1 increased, and NRF2 protein levels also increased. The apoptosis rate increased by silencing NRF2 expression in arsenite-transformed HaCaT (T-HaCaT) cells. Meanwhile, the expression of pro-apoptotic proteins (cleaved-caspase-3/caspase-3, CHOP, Bax) and ATF4, ATF6 increased. On the contrary, antiapoptotic protein levels (Bcl-2 and Mcl-1) decreased. The ability of colony formation and migration of T-HaCaT cells decreased. In conclusion, arsenite activated NRF2 in the later stages, decreasing apoptosis characterized by inhibiting endoplasmic reticulum stress-depended and mitochondria-depended apoptosis pathway, and further promoting NaAsO2-induced HaCaT cellular malignant transformation.

Sag deletion promotes DMBA/TPA-induced skin carcinogenesis via YAP accumulation.

Sag deletion promotes DMBA/TPA-induced skin carcinogenesis via YAP accumulation.

Epigenetics and ultraviolet radiation: Implications for skin ageing and carcinogenesis.

Recent published data have highlighted the importance of epigenetics in the response of the skin to recreational and therapeutic ultraviolet radiation (UVR) exposure. 'Epi'-from the Greek επί, meaning over, outside of or around-relates to the chemical modifications that occur on top of the DNA sequence (for example, DNA methylation) and its associated proteins (e.g. histone modifications, including methylation, acetylation and phosphorylation). These epigenetic processes, collectively called the 'epigenome', dictate the three-dimensional conformation of the DNA, thus impacting upon gene expression and genomic stability. Given that epigenetic changes are long-lived and mitotically heritable, an accumulation of epigenetic perturbations likely influence the pathogenesis of the chronic consequences of UVR exposure, including photoageing and skin cancer risk. In this review, we describe the multifarious epigenetic effects elicited by UVR in the skin. We further speculate on the underlying molecular mechanisms that may direct epigenetic changes, such as oxidative stress and changes in metabolism, and their impact on skin health and disease.

An Insight on Skin Cancer About Different Targets With Update on Clinical Trials and Investigational Drugs.

Cancer is a diverse disease caused by transcriptional changes involving genetic and epigenetic features that influence a huge variety of genes and proteins. Skin cancer is a potentially fatal disease that affects equally men and women globally and is characterized by many molecular changes. Despite the availability of various improved approaches for detecting and treating skin cancer, it continues to be the leading cause of death throughout society. This review highlights a general overview of skin cancer, with an emphasis on epidemiology, types, risk factors, pathological and targeted facets, biomarkers and molecular markers, immunotherapy, and clinical updates of investigational drugs associated with skin cancer. The skin cancer challenges are acknowledged throughout this study, and the potential application of novel biomarkers of skin cancer formation, progression, metastasis, and prognosis is explored. Although the mechanism of skin carcinogenesis is currently poorly understood, multiple articles have shown that genetic and molecular changes are involved. Furthermore, several skin cancer risk factors are now recognized, allowing for efficient skin cancer prevention. There have been considerable improvements in the field of targeted treatment, and future research into additional targets will expand patients' therapeutic choices. In comparison to earlier articles on the same issue, this review focused on molecular and genetic factors and examined various skin cancer-related factors in depth.

Anti-Toxic Principles from Musa Sapientum and Moringa Oleifera Ameliorated Skin Histo-Pathology, Decreased Lipid Peroxidation and Promoted Melatonin/TNF-Alpha/p53-Mediated Apoptosis in Cadmium Chloride-Induced Carcinogenesis in Rats

This study evaluated anticancer potentials of Musa sapientum (MS) and Moringa oleifera (MO) in cadmium chloride (CdCl2)-induced skin and liver carcinogenesis. Musa sapientum fraction-1 (MSF1) and Moringa oleifera fraction-6 (MOF6) were extracted from MS suckers and MO leaves, respectively, using column-chromatography methods. Forty-five adult male rats were randomly divided into 11 groups (n = 5). Cancer-induction was via single intraperitoneal administration of 1.25 mg/kg CdCl2. Groups 1 and 2 received physiological saline and CdCl2 dose, respectively. Groups 3–5 received CdCl2 dose on day 1 but were post-treated on days 15–56 with 15 mg/kg MOF6, 30 mg/kg MOF6 and 10 mg/kg MSF1, respectively. Group 6 received CdCl2dose on day 1 and were post-treated on days 15– 28 with doxorubicin + cisplatin doses. Groups 7–9 received MOF6 dose and MSF1 dose, respectively (days 1–56). Groups 10 and 11 received CdCl2dose on day 1 and were posttreated with 30 mg/kg MOF6 and 10 mg/kg MSF1, respectively (days 1–56). Doxorubicin and extracts doses were administered orally. Skin histo-pathology (haematoxylin and eosin), sera melatonin and tumour necrosis factor-alpha (TNFa) (enzyme linked immunosorbent assays [ELISA]) levels were evaluated. Malondialdehyde (thiobarbituric acid assay) and p53 (ELISA) levels were evaluated in liver homogenates. Data were statistically analysed using ANOVA at p ≤ 0.05. Results showed skin histo-alterations in Group 2, compared with normal skin histology in Groups 1 and 3–11. Statistical analyses showed significant downregulation of p53, non-significant downregulations of malondialdehyde and TNFa, and non-significant upregulation of melatonin in Groups 3–11 compared with Group 2. Overall, post-treatments with MOF6 and MSF1 exhibited possible anticancer potentials of these plants extracts via degrees of amelioration of CdCl2-induced skin histo-pathology and carcinogenesis.

Activation of Peroxisome Proliferator-Activated Receptor-β/δ (PPARβ/δ) in Keratinocytes by Endogenous Fatty Acids.

Nuclear hormone receptors exist in dynamic equilibrium between transcriptionally active and inactive complexes dependent on interactions with ligands, proteins, and chromatin. The present studies examined the hypothesis that endogenous ligands activate peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) in keratinocytes. The phorbol ester treatment or HRAS infection of primary keratinocytes increased fatty acids that were associated with enhanced PPARβ/δ activity. Fatty acids caused PPARβ/δ-dependent increases in chromatin occupancy and the expression of angiopoietin-like protein 4 (Angptl4) mRNA. Analyses demonstrated that stearoyl Co-A desaturase 1 (Scd1) mediates an increase in intracellular monounsaturated fatty acids in keratinocytes that act as PPARβ/δ ligands. The activation of PPARβ/δ with palmitoleic or oleic acid causes arrest at the G2/M phase of the cell cycle of HRAS-expressing keratinocytes that is not found in similarly treated HRAS-expressing Pparb/d-null keratinocytes. HRAS-expressing Scd1-null mouse keratinocytes exhibit enhanced cell proliferation, an effect that is mitigated by treatment with palmitoleic or oleic acid. Consistent with these findings, the ligand activation of PPARβ/δ with GW0742 or oleic acid prevented UVB-induced non-melanoma skin carcinogenesis, an effect that required PPARβ/δ. The results from these studies demonstrate that PPARβ/δ has endogenous roles in keratinocytes and can be activated by lipids found in diet and cellular components.