Cutaneous Tumorigenesis Research Articles

Abstract 3141: Toll-like receptor 4 knockout promotes cutaneous tumorigenesis in mice lack of Ikka heterozygous loss in keratinocytes

Abstract Role of recognizing pathogen-associated molecular patterns in skin carcinogenesis has not been extensively studied. Toll-like receptor 4 (TLR4) recognizes gram-negative lipopolysaccharide. To explore the impact of interplay between TLR4-regulated microbiota and host epithelial cells on tumorigenesis, we adopted a mouse model that expresses hemizygous Ikkα gene induced by a keratin 5 Cre (K5.Cre, IkkααKC/+). IkkααKC mice die within 3 weeks after birth. Inducible Ikkα ablation mediated by K15.CrePR1 or K5.CreER results in spontaneous skin tumors. We found an increased incidence of spontaneous skin tumors in Tlr4-/-;IkkααKC/+ mice compared to Tlr4-/- or IkkααKC/+ mice. We detected markedly elevated bacteria numbers on the surface of skin tumors compared to the adjacent skin. Interestingly, the oral cavity of Tlr4-/-;IkkααKC/+ mice showed an elevated proportion of gram-negative bacteria compared to Tlr4-/- or IkkααKC/+ mice. To further determine the effect of bone marrow (BM)-derived hemopoietic cells on tumorigenesis, we performed BM transplant experiments. IkkααKC/+ mice with Tlr4-/- BM developed more cutaneous skin tumors than IkkααKC/+ mice with WT BM. Based on these findings, we hypothesized that Tlr4-/- hemopoietic cells regulate microbiota, which further results in altered skin carcinogenesis. We are revealing the detailed mechanism of how Tlr4-/- hemopoietic cells contribute to microbiota changes and tumorigenic promotion. Citation Format: Amit Kumar Singh. Toll-like receptor 4 knockout promotes cutaneous tumorigenesis in mice lack of Ikka heterozygous loss in keratinocytes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3141.

Epigenetic modifiers DNMT3A and BCOR are recurrently mutated in CYLD cutaneous syndrome

Patients with CYLD cutaneous syndrome (CCS; syn. Brooke-Spiegler syndrome) carry germline mutations in the tumor suppressor CYLD and develop multiple skin tumors with diverse histophenotypes. Here, we comprehensively profile the genomic landscape of 42 benign and malignant tumors across 13 individuals from four multigenerational families and discover recurrent mutations in epigenetic modifiers DNMT3A and BCOR in 29% of benign tumors. Multi-level and microdissected sampling strikingly reveal that many clones with different DNMT3A mutations exist in these benign tumors, suggesting that intra-tumor heterogeneity is common. Integrated genomic, methylation and transcriptomic profiling in selected tumors suggest that isoform-specific DNMT3A2 mutations are associated with dysregulated methylation. Phylogenetic and mutational signature analyses confirm cylindroma pulmonary metastases from primary skin tumors. These findings contribute to existing paradigms of cutaneous tumorigenesis and metastasis.

Update on protease-activated receptor 2 in cutaneous barrier, differentiation, tumorigenesis and pigmentation, and its role in related dermatologic diseases.

Protease-activated receptor 2 (PAR2) is a transmembrane receptor expressed by multiple tissues, including skin, with rapidly expanding knowledge regarding its roles. In the skin, PAR2 has extensively documented effects in promoting Th2 inflammation and pruritus; and its role in atopic dermatitis continues to be thoroughly studied. Numerous new investigations have shown a more complex range of activities potentially related to dermatologic diseases. Goal of this review is to outline emerging effects of PAR2 activation in the skin other than those related to immunologic and pruritic functions. Specifically, this work seeks to summarize current knowledge (and gaps) of PAR2 as a regulator of epidermal barrier, keratinocyte differentiation, cutaneous tumorigenesis and pigmentation. Additional focus will be placed on possible involvement in dermatologic disease and emergence as a therapeutic target.

Effect of Oral Co-administration of Curcumin and Piperine on the Development of Induced Cutaneous Tumors in Mice

Turmeric is a yellow powder from the rhizomes of a herbaceous plant, Curcuma longa. Curcumin, a major component of turmeric, is a polyphenol that has anti-oxidant, anti-inflammatory and antiproliferative properties that give it an antitumor effect. Administration of oral curcumin appears few effective because of its low bioavailability but adjuvants such as piperine present in black pepper may improve this bioavailability. The aim of the present study is the evaluation the effect of curcumin and piperine-based regimen on the development and growth of chemo-induced cutaneous tumors in Swiss albino mice. A single topical application of 400 nmol of DMBA (7,12-dimethylbenz (a) anthracene) is followed one week later by the application twice a week of 5 nmol of TPA (12-O-tetradecanoylphorbol-13-acetate) during 10 weeks. DMBA/TPA-induced papillomas are evaluated in mice fed a standard diet or curcumin (0.5%) and piperine (0.005%) diet. Curcumin significantly inhibited the tumorigenic effect of DMBA and TPA by decreasing tumor incidence by 50%, tumor multiplicity by 38% and tumor volume by 90%. In addition, the histological study showed that the curcumin and piperine diet attenuated epidermal changes caused by DMBA/TPA treatment such as hyperplasia, cellular atypia and hyperkeratosis. Our study demonstrated that oral co-administration of curcumin and piperine has a significant inhibitory effect on DMBA/TPA-induced cutaneous tumorigenesis. Piperine, by increasing the bioavailability of curcumin, improves its chemoprotective and chemo-preventive efficacy against tumor development.

Chemically induced skin carcinogenesis: Updates in experimental models (Review).

Skin cancer is one of the most common malignancies affecting humans worldwide, and its incidence is rapidly increasing. The study of skin carcinogenesis is of major interest for both scientific research and clinical practice and the use of in vivo systems may facilitate the investigation of early alterations in the skin and of the mechanisms involved, and may also lead to the development of novel therapeutic strategies for skin cancer. This review outlines several aspects regarding the skin toxicity testing domain in mouse models of chemically induced skin carcinogenesis. There are important strain differences in view of the histological type, development and clinical evolution of the skin tumor, differences reported decades ago and confirmed by our hands-on experience. Using mouse models in preclinical testing is important due to the fact that, at the molecular level, common mechanisms with human cutaneous tumorigenesis are depicted. These animal models resemble human skin cancer development, in that genetic changes caused by carcinogens and pro-inflammatory cytokines, and simultaneous inflammation sustained by pro-inflammatory cytokines and chemokines favor tumor progression. Drugs and environmental conditions can be tested using these animal models. keeping in mind the differences between human and rodent skin physiology.

Topical application of a platelet activating factor receptor agonist suppresses phorbol ester-induced acute and chronic inflammation and has cancer chemopreventive activity in mouse skin.

Platelet activating factor (PAF) has long been associated with acute edema and inflammatory responses. PAF acts by binding to a specific G-protein coupled receptor (PAF-R, Ptafr). However, the role of chronic PAF-R activation on sustained inflammatory responses has been largely ignored. We recently demonstrated that mice lacking the PAF-R (Ptafr-/- mice) exhibit increased cutaneous tumorigenesis in response to a two-stage chemical carcinogenesis protocol. Ptafr-/- mice also exhibited increased chronic inflammation in response to phorbol ester application. In this present study, we demonstrate that topical application of the non-hydrolysable PAF mimetic (carbamoyl-PAF (CPAF)), exerts a potent, dose-dependent, and short-lived edema response in WT mice, but not Ptafr -/- mice or mice deficient in c-Kit (c-Kit W-sh/W-sh mice). Using an ear inflammation model, co-administration of topical CPAF treatment resulted in a paradoxical decrease in both acute ear thickness changes associated with a single PMA application, as well as the sustained inflammation associated with chronic repetitive PMA applications. Moreover, mice treated topically with CPAF also exhibited a significant reduction in chemical carcinogenesis. The ability of CPAF to suppress acute and chronic inflammatory changes in response to PMA application(s) was PAF-R dependent, as CPAF had no effect on basal or PMA-induced inflammation in Ptafr-/- mice. Moreover, c-Kit appears to be necessary for the anti-inflammatory effects of CPAF, as CPAF had no observable effect in c-Kit W-sh/W-sh mice. These data provide additional evidence that PAF-R activation exerts complex immunomodulatory effects in a model of chronic inflammation that is relevant to neoplastic development.

326 - Acute Solar UV Exposure Generates Photodamage-Associated Protein Epitopes in Healthy Human Skin: Implications for Cutaneous Tumorigenesis

326 - Acute Solar UV Exposure Generates Photodamage-Associated Protein Epitopes in Healthy Human Skin: Implications for Cutaneous Tumorigenesis

Cooperative benefit for the combination of rapamycin and imatinib in tuberous sclerosis complex neoplasia

Tuberous sclerosis (TS) is a common autosomal-dominant disorder characterized by tumors of the skin, lung, brain, and kidneys. Monotherapy with rapamycin however resulted in partial regression of tumors, implying the involvement of additional pathways. We have previously implicated platelet-derived growth factor-BB in TS-related tumorigenesis, thus providing a rationale for a combination of mTOR/PDGF blockade using rapamycin and imatinib. Here, we test this combination using a well-established preclinical model of cutaneous tumorigenesis in TS, tsc2ang1 cells derived from a skin tumor from a mouse heterozygous for tsc2. Treatment of tsc2ang1 cells with a combination of rapamycin and imatinib led to an inhibition of proliferation compared with either vehicle treatment or treatment with rapamycin or imatinib monotherapy. Combination therapy also led to a decrease in Akt activation. Potent in vivo activity in animal experiments by combination therapy was noted, without toxicity to the animals. Our findings provide a rationale for the combined use of rapamycin and imatinib, both FDA approved drugs, for the treatment of TS.

New Insights About Infant and Toddler Skin: Implications for Sun Protection

The skin is increasingly recognized as a component of the innate immune response, in addition to its role as a physical barrier. Although the deleterious effects of solar ultraviolet radiation (UVR), including immunosuppression and cutaneous tumorigenesis, are widely acknowledged, most studies to date have concentrated on adult skin. Despite the more sensitive nature of infant and toddler skin, little is known about its responses to UVR exposure, whether acute or long-term. Accumulating evidence suggests not only that the skin's barrier protection remains immature throughout at least the first 2 years of life but also that accumulation of UVR-induced changes in the skin may begin as early as the first summer of life. Such evidence not only affirms the importance of sun protection during the infant and toddler years but underscores the need for more research to establish evidence-based standards of care in this area. In this article we review recent studies in which differences between the skin properties of infants and young children and those of adults were compared, and we discuss the implications of these differences for sun-protection practices.

Changes of cathepsin B in human photoaging skin both in vivo and in vitro

Background Cathepsin B plays an important role in cell cycle, extracellular matrix changes and cutaneous tumorigenesis: whether it plays a role in photoaged skin remains unknown. This study aimed to investigate the role of cathepsin B in skin photoaging in vivo and in vitro. Methods The expressions of cathepsin B were compared with immunohistochemical methods in solar exposed skin and solar protected skin of six healthy Chinese volunteers. The mRNA and protein expression of cathepsin B in ultraviolet light A (UVA) induced premature senescence fibroblasts in vitro were detected by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting technique. Results Decreased expression of cathepsin B was observed in photoaged skin compared with that of the solar protected skin. In the UVA induced, premature senescence fibroblasts, a lower expression of cathepsin B was detected by Western blotting and a decreased synthesis of cathepsin B mRNA in the same cells was revealed by real-time RT-PCR. Conclusions The results demonstrated a significant negative correlation between skin photoaging and cathepsin B in vitro and in vivo. We propose that cathepsin B, besides matrix metalloproteinases and antioxidant enzymes, is involved in the process of skin photoaging in that it contributes to extracellular matrix remodelling and is a dominant protease in cellular apoptosis and senescence.

CHEMOPREVENTIVE EFFECT OF VITIS VINIFERA EXTRACT ON 12- O-TETRADECANOYL-13-PHORBOL ACETATE-INDUCED CUTANEOUS OXIDATIVE STRESS AND TUMOR PROMOTION IN MURINE SKIN

Vitis vinifera (grapes) is used as a fruit worldwide and known for its pharmacological properties. The present paper assesses the chemopreventive potential of Vitis vinifera against 12- O-tetradecanoyl-13-phorbol acetate (TPA)-mediated tumor promotion in 7,12-dimethyl-benz[a]anthracene (DMBA) initiated mice skin. Skin tumor initiation was achieved by a single topical application of DMBA (40 μg/animal/0.20 ml acetone) to mice. Two weeks after the initiation, promoting agent, TPA (5.0 μg/animal/0.2 ml acetone) was applied two times a week for 20 weeks. Pretreatment of Vitis vinifera 1 h prior to each application of TPA resulted in protection against cutaneous tumorigenesis in dose-dependent manner. This inhibition was evident when tumor data was considered as the percentage of mice with tumor and the number of tumors per mouse. We have shown that typical application of Vitis vinifera prior to that of TPA resulted in significant inhibition against TPA-caused induction of epidermal ODC activity ( P<0.001) and DNA synthesis. Application of Vitis vinifera at a dose level of 5.0 mg and 10.0 mg kg −1 body weight in acetone prior to that of TPA treatment resulted in partial significant inhibition of oxidative stress in dose-dependent manner. The concomitant increase in the microsomal lipid peroxidation and xanthine oxidase activities were significantly reduced ( P<0.001). In addition, the depleted level of glutathione and inhibited activities of antioxidant enzymes were recovered to the partial significant level. Hence, it can be suggested that Vitis vinifera can be used as a chemopreventive agent against oxidative stress and carcinogenesis.

Microsatellite instability and its relevance to cutaneous tumorigenesis.

Increasing evidence suggests that human tumors sequentially accumulate multiple mutations that cannot be explained by the low rates of spontaneous mutations in normal cells (2-3 mutations/cell). The mathematical models estimate that for the solid tumors to develop, as many as 6-12 mutations are required in each tumor cell. Therefore, to account for such high mutation rates, it is proposed that tumor cells are genetically unstable, i.e. they have genome-wide mutations at short repetitive DNA sequences called microsatellites. Microsatellite repeats are scattered throughout the human genome, primarily in the non-coding regions, and can give rise to variants with increased or reduced lengths, i.e. microsatellite instability (MSI). This instability has been reported in an increasing number of cutaneous tumors including: melanocytic tumors, basal cell carcinomas and primary cutaneous T-cell lymphomas. Moreover, MSI has been observed in skin tumors arising in the context of some hereditary disorders such as Muir-Torre syndrome, Von Recklinghausen's disease and disseminated superficial porokeratosis. While MSI in some of these disorders reflects underlying DNA replication errors, the mechanism of instability in others is still unknown. Thus far, MSI is considered to be a distinct tumorigenic pathway that reveals surprising versatility. The ramifications for cutaneous neoplasms warrant further investigation.

Low iron state is associated with reduced tumor promotion in a two-stage mouse skin carcinogenesis model

The purpose of this study was to investigate the effect of low iron state in a two-stage mouse skin carcinogenesis model using 7,12-dimethylbenz[ a]anthracene (DMBA)-initiated and benzoyl peroxide (BPO)-promoted cutaneous tumorigenesis. All mice were treated with DMBA. Low iron state was achieved by injection with phenylhydrazine hydrochloride and feeding low iron diet. A low iron state resulted in a decrease in tumor incidence (papillomas and carcinomas) and number of tumors/mouse. Also, the conversion of papillomas to carcinomas was lower in mice on a low iron state. BPO treatment enhanced epidermal lipid peroxidation (LPO) and was accompanied by a depletion in the level of epidermal reduced glutathione (GSH) and decrease in the activities of antioxidant enzymes. BPO treatment also increased ornithine decarboxylase (ODC) activity and [ 3H]thymidine incorporation into cutaneous DNA. Mice in a low iron state were less susceptible to the effects of BPO treatment, as was apparent from a partial recovery of GSH levels and the activities of antioxidant enzymes, as well as a lower induction in ODC activity, [ 3H]thymidine incorporation into cutaneous DNA and lesser epidermal LPO. As expected, cutaneous iron levels were lower in mice on a low iron state. Thus, our data show that the tumor-promoting potential of BPO is reduced by low iron state in a two-stage mouse skin carcinogenesis model.

Effect of iron overload on the benzoyl peroxide-mediated tumor promotion in mouse skin

In this communication, we report that iron overload augments benzoyl peroxide (BPO)-mediated tumor promotion in 7,12-dimethylbenz[ a]anthracene (DMBA)-initiated mouse skin. Female albino Swiss mice were overloaded with iron and tumors were initiated by applying a single topical application of DMBA. A week after the initiation, promoting agent, BPO, was applied three times/week for 46 weeks. The appearance of the first tumor (papilloma) and the number of tumors/mouse were recorded. When compared to the control group, the iron-overloaded mice showed an increased incidence of tumors at various time intervals. In iron-overloaded animals, tumors appeared earlier and also the number of tumors/mouse was significantly higher. These data could be correlated with the iron levels of mouse skin in the two groups. Further, BPO-mediated induction in ornithine decarboxylase (ODC) activity and [ 3H]thymidine incorporation in cutaneous DNA were higher in the iron overload group. In addition, in iron-overloaded mice, cutaneous lipid peroxidation (LPO) and xanthine oxidase (XOD) activities were higher, whereas catalase activity was reduced. Similar to papilloma induction, a significant increase in carcinoma yield and incidence was observed in iron-overloaded animals. Based on this study, we propose that iron overload significantly increases the tumor promotion and progression potential of BPO. We suggest that oxidative stress generated by iron overload is responsible for the augmentation of BPO-mediated cutaneous tumorigenesis.

Effects of a new antiulcer agent, ecabet sodium on a cutaneous tumorigenesis induced with 7,12-dimethylbenz(a)anthracene in mice

A new antiulcer agent, ecabet sodium is one of dehydroabietic acid derivatives prepared from pine resin, and is known to have a potent protective effect on gastric hemorrhagic lesions induced with carcinogens by covering a gastric mucosa after oral administration. In the present study, we investigated the effects of synthetic ecabet sodium on cutaneous tumorigenesis and development of skin-tumors induced by 7,12-dimethylbenz(a)anthracene application on mouse back skin. It was tentatively concluded that ecabet sodium reduced the incidence of skin-tumors (squamous cell papillomas) by inhibition of DNA synthesis in de novo pathway, and suppressed the development of papillomas by decrease of DNA synthesis in a salvage pathway.