Black tattoos protect against UVR-induced skin cancer in mice

Lessons learned in a decade: Medical-toxicological view of tattooing

Tattooing has been part of the human culture for thousands of years, yet only in the past decades has it entered the mainstream of the society. With the rise in popularity, tattoos also gained attention among researchers, with the aim to better understand the health risks posed by their application. 'A medical-toxicological view of tattooing'-a work published in The Lancet almost a decade ago, resulted from the international collaboration of various experts in the field. Since then, much understanding has been achieved regarding adverse effects, treatment of complications, as well as their regulation for improving public health. Yet major knowledge gaps remain. This review article results from the Second International Conference on Tattoo Safety hosted by the German Federal Institute for Risk Assessment (BfR) and provides a glimpse from the medical-toxicological perspective, regulatory strategies and advances in the analysis of tattoo inks.

Oral phytochemicals as photoprotectants in UVR exposed hairless mice: A study of hesperidin methyl chalcone, phloroglucinol, and syringic acid

Ultraviolet radiation is the primary risk factor for keratinocyte carcinoma. Because of increasing incidence rates, new methods of photoprotection must be explored. Oral supplementation with photoprotective compounds presents a promising alternative. Phytochemical compounds like hesperidin methyl chalcone, phloroglucinol, and syringic acid are particularly of interest because of their antioxidant properties. Our primary outcome was to evaluate the effects of oral phytochemicals on photocarcinogenesis with time until tumour onset as the primary endpoint. A total of 125 hairless C3.Cg-Hrhr/TifBom Tac mice were randomised to receive tap water supplemented with either 100 mg/kg hesperidin methyl chalcone, phloroglucinol, or syringic acid, 600 mg/kg nicotinamide as a positive control, or no supplementation. The mice were irradiated with 3.5 standard erythema doses thrice weekly to induce photocarcinogenesis. Supplementation with the phytochemicals phloroglucinol and syringic acid and nicotinamide delayed tumour onset from a median of 140 days to 151 (p = 0.036), 157 days (p = 0.02), and 178 (p = 2.7·10-5), respectively. Phloroglucinol and nicotinamide supplementation reduced tumour number. Nicotinamide increased UV-induced pigmentation and reduced oedema formation, while phloroglucinol supplementation reduced epidermal thickness. These results indicate that oral supplementation with phloroglucinol and syringic acid protects against photocarcinogenesis in hairless mice, but not to the same extent as nicotinamide.

Repeated exposure to fractional CO2 laser delays squamous cell carcinoma formation and prevents clinical and subclinical photodamage visualized by line-field confocal optical coherence tomography and histology

OBJECTIVES

Ablative fractional laser (AFL) is a well-established modality for treating ultraviolet radiation (UVR)-induced skin photodamage. We aimed to investigate the potential of AFL to delay squamous cell carcinoma (SCC) formation and prevent photodamage in a preclinical UVR-induced SCC model.

MATERIALS AND METHODS

Hairless C3.Cg-Hrhr /TifBomTac mice (n = 50) were exposed to UVR three times weekly throughout the study. UV-exposed mice were randomized to two groups that received dorsal CO2 AFL (10 mJ/mb, 10% density) or no treatment. AFL was performed every other week for a total of 16 weeks (nine treatments in total). The primary outcome was time to tumor occurrence. In a subset of mice on Day 150, prevention of clinical photodamage was assessed by examination of skin tightness and dyspigmentation. Concomitantly, assessment of subclinical photoprevention based on normalization of keratinocyte dysplasia, dermo-fiber morphology (collagen and elastin fibers), and skin thickness, was performed using line-field confocal optical coherence tomography (LC-OCT) and histology.

RESULTS

Repeated AFL treatments delayed SCC tumor development compared to UVR control mice by 12, 19, and 30 days for first, second, and third tumors, respectively (p ≤ 0.0017). Compared to UVR controls, AFL prevented photodamage both clinically and subclinically, based on LC-OCT and histology. In the epidermal layer, AFL imparted photopreventative effects including reduced dyspigmentation and keratinocyte dysplasia (1 vs. 2.5, p = 0.0079) and partial normalization of the epidermal thickness (p < 0.0001). In the dermis, AFL led to twofold greater skin tightness (p = 0.0079), improved dermo-fiber structure, and dermal thickness (p = 0.0011).

CONCLUSION

In conclusion, repeated AFL treatments of UVR-exposed skin significantly delayed SCC tumor formation and prevented clinical and imaging-assessed subclinical signs of photodamage, indicating a potential for AFL in prevention strategies for SCC and photodamage in high-risk populations.

Syncarcinogenesis of natural UV radiation and polycyclic aromatic hydrocarbons in the development of squamous cell carcinomas of the skin?

Squamous cell carcinomas (SCC) of the skin can be induced by occupational exposures to polycyclic aromatic hydrocarbons (PAHs), as in tar and soot, or to UV radiation and can be recognized and compensated as occupational diseases. A possible syncarcinogenic effect of these exposures in the development of SCC in humans is under discussion. For the scientific validation of this question, a systematic literature search was conducted using the databases PubMed, Web of Science, and Scopus. Studies on individuals with SCC of the skin and their precursors as well as occupational, non-occupational, or therapeutic exposure to UV radiation and PAHs were selected. In addition, animal studies with exposure to UV radiation and PAHs were evaluated. After screening the abstracts of 510 identified studies, the full texts of 131 studies were reviewed. None of the epidemiological studies provided robust evidence for a syncarcinogenesis of PAHs and UV radiation in the development of SCC of the skin in humans. Nevertheless, as there are indications for a (super-)additive effect of UV radiation and PAH exposure from animal studies and mechanistic investigations, syncarcinogenesis seems possible. However, quantitative dose-response relationships are lacking which would allow comparison of the onset of an adverse effect between the different exposure levels.

In vitro analysis of catalase and superoxide dismutase mimetic properties of blue tattoo ink

Tattoo inks are comprised of different combinations of bioactive chemicals with combined biological effects that are insufficiently explored. Tattoos have been associated with oxidative stress; however, a recent N-of-1 study suggested that blue tattoos may be associated with suppressed local skin oxidative stress. The present study aimed to explore the attributes of the blue tattoo ink (BTI) that may explain its possible effects on redox homeostasis, namely the catalase (CAT) and superoxide dismutase (SOD)-mimetic properties that have been reported for copper(II) phthalocyanine (CuPC) - the main BTI constituent. Intenze™ Persian blue (PB) BTI has been used in the experiment. CAT and SOD-mimetic properties of PB and its pigment-enriched fractions were analyzed using the carbonato-cobaltate (III) formation-derived H₂O₂ dissociation and 1,2,3-trihydroxybenzene autoxidation rate assays utilizing simple buffers and biochemical matrix of normal skin tissue as chemical reaction environments. CuPC-based tattoo ink PB and both its blue and white pigment-enriched fractions demonstrate CAT and SOD-mimetic properties in vitro with effect sizes demonstrating a substantial dependence on the biochemical environment. PB constituents act as inhibitors of CAT but potentiate its activity in the biochemical matrix of the skin. CuPC-based BTI can mimic antioxidant enzymes, however chemical constituents other than CuPC (e.g. the photoreactive TiO₂) seem to be at least partially responsible for the BTI redox-modulating properties.

Topical Brimonidine Delays Ultraviolet Radiation-Induced Squamous Cell Carcinoma in Hairless Mice

We investigated whether topical brimonidine delayed or enhanced the development of squamous cell carcinoma (SCC) when ultraviolet radiation (UVR) was applied to a well-established murine model. Hairless female mice (n = 125) were randomized into five groups and treated as follows: 1% brimonidine cream before UVR (Group 1), 0.33% brimonidine gel before UVR (Group 2), 1% brimonidine cream after UVR (Group 3), UVR only (control; Group 4) and 1% brimonidine cream only (control; Group 5). For each animal, the first four tumors were recorded and followed until three tumors reached 4 mm or one tumor reached 12 mm in diameter. All animal experiments continued for up to 365 days or until death. Application of 1% brimonidine cream before UVR delayed tumor development relative to control mice treated with UVR alone (P = 0.000006). However, when 0.33% brimonidine gel was applied before UVR (P = 0.313) or 1% brimonidine cream was applied after UVR (P = 0.252), there was no significant delay in tumor development relative to control mice treated with UVR alone. The development of the second and third tumors followed a similar pattern. Topical 1% brimonidine cream applied before UVR exposure delayed SCC development in hairless mice. In contrast, when brimonidine was applied after UVR there was no significant delay in tumor development. These results suggest that the 1% brimonidine cream probably absorbed the UVR, and therefore, a delay in tumor formation was only seen when brimonidine was applied before irradiation. However, there can be multiple reasons for this delay in photocarcinogenesis.

Few X-ray and PUVA treatments accelerate photocarcinogenesis in hairless mice

PUVA is a treatment that combines oral methoxypsoralen (8-MOP) with ultraviolet radiation A (UVA). It is used for severe psoriasis and the early stages of T-cell lymphoma. X-rays are an effective treatment for skin cancers. Both treatments are in higher doses used to treat skin malignancies and simultaneously increase the risk of keratinocyte cancer. The main objective of this study was to test whether a few PUVA or X-ray treatments could delay the development of ultraviolet radiation (UVR)-induced skin tumors in a well-established hairless mouse model. Three groups of immunocompetent mice (total, N = 75) were included in the study. All groups were UVR-exposed during the study period. In addition, one group was treated with PUVA and another group was treated with X-rays at days 45, 52, 90 and 97. A control group was treated with UVR only. We recorded when the first, second and third skin tumors were induced in each mouse. Skin tumors developed significantly earlier in both the PUVA and X-ray groups (median, 188 days) than in the control mice (median, 215 days; p < 0.001). Therefore, a few X-ray and PUVA treatments both significantly accelerated the development of skin tumors in hairless mice, compared to UVR controls. Neither treatment showed a delay of UVR-induced skin tumors and caution should be exercised before applying these treatments to sun-damaged skin.

Phototoxic versus photoprotective effects of tattoo pigments in reconstructed human skin models: In vitro phototoxicity testing of tattoo pigments: 3D versus 2D

The increasing number of tattooed persons urges the development of reliable test systems to assess tattoo associated risks. The alarming prevalence of 60 % phototoxic reactions in tattoos ask for a more comprehensive investigation of phototoxic reactions in tattooed skin. Here, we aimed to compare the cellular responses of human skin cells to ultraviolet (UV)A and UVB irradiation in doses of short to intermitted sun exposure (3-48 J/cm² and 0.05-5 J/cm², respectively) in the presence of tattoo pigments. Therefore, we used fibroblast monolayer culture (2D), our recently developed three dimensional full-thickness skin model with dermal-located tattoo pigments (TatS_FT) and its dermal equivalents (TatS_DE) that lack keratinocytes. We tested the most frequently used tattoo pigments carbon black, titanium dioxide (TiO₂) anatase and rutile as well as Pigment Orange (P.O.)13 in ranges from 0.067 to 2.7 ng/cell in 2D. For TatS_DE and TatS_FT, concentrations were 1.3 ng/cell for TiO₂, 0.67 ng/cell for P.O.13 and 0.067 ng/cell for carbon black. We assessed cell viability and cytokine release in all systems, and cyclobutane pyrimidine dimer (CPD) formation in TatS_FT. Phototoxicity of tattoo pigments was exclusively observed in 2D, where especially TiO₂ anatase induced phototoxic effects in all concentrations (0.067-2.7 ng/cell). In contrast, fibroblasts were protected from UV irradiation in TatS_DE by TiO₂ and carbon black. Neither toxic nor protective effects were recorded in TatS_FT. P.O.13 showed altered cytokine secretion in 2D (0.067-1.3 ng/cell) and TatS_DE, despite the absence of significant effects on viability in all systems. All pigments reduced the number of CPDs in TatS_FT compared to the pigment-free controls. In conclusion, our study shows that within a 3D arrangement, intradermal tattoo pigments may act photoprotective despite intrinsic phototoxic properties in 2D. Thus, dermal 3D equivalents should be considered to evaluate acute tattoo pigment toxicology.

Tumor Clearance and Immune Cell Recruitment in UV-Induced Murine Squamous Cell Carcinoma Exposed to Ablative Fractional Laser and Imiquimod Treatment

BACKGROUND AND OBJECTIVES

Keratinocyte carcinoma (KC) is the most common cancer worldwide, and squamous cell carcinoma (SCC) is the second most frequent subtype. Ablative fractional laser (AFL)-assisted drug delivery significantly enhances the uptake of topically applied drugs. The objective of this study was to assess tumor response and perform a descriptive characterization of the local recruitment of immune cells and systemic immune mediator levels in an ultraviolet radiation (UVR)-induced murine SCC model after AFL treatment alone and combined with topical imiquimod.

STUDY DESIGN/MATERIALS AND METHODS

Immunocompetent hairless mice (C3·Cg/TifBomTac, n = 74) were irradiated with solar-simulated UVR until 3-mm SCCs developed. The mice were divided into four interventional groups: AFL alone, AFL + imiquimod, imiquimod alone, and untreated SCC controls. AFL was given as a single treatment, whereas imiquimod was applied daily until the mice were euthanized on Days 0, 2, 7, or 14. SCCs were photographed and measured (mm) to assess the therapeutic response. Skin samples were processed for histopathological and immunohistochemical analyses, as well as for flow cytometry. Cytokine expression changes in sera were analyzed using ELISpot cytokine arrays.

RESULTS

Treatment of mouse SCCs with AFL + imiquimod induced the most robust immune cell infiltration and the greatest proportion of tumor clearance compared to other interventions. Early innate immune cell infiltration was induced by AFL + imiquimod treatment as the number of neutrophils and macrophages had increased fourfold within 2 days of treatment initiation compared with untreated SCC control mice (P < 0.05). AFL treatment alone had a more limited effect, with a fourfold increase in neutrophils (P < 0.05) but no significant increase in the number of macrophages. Correspondingly, treatment with AFL + imiquimod had the greatest effects on the adaptive immune cell recruitment: CD4⁺ T-helper cells increased threefold at Day 7 compared with untreated SCCs (P = 0.0001) and, notably, cytotoxic CD8⁺ T cells increased 14-fold at Day 14 (P = 0.0112). In addition, FOXP3⁺ regulatory T cells (Tregs) increased 14-fold at Day 7 (P = 0.0026), suggesting the resolution of the inflammatory infiltration. AFL treatment alone induced a moderate immune cell infiltration (a twofold increase in CD4⁺ T-helper cells, P = 0.0200; a threefold increase in CD8⁺ T cells, P = 0.0100; and a 14-fold increase in FOXP3⁺ Tregs at Day 14, P = 0.0021), whereas imiquimod alone did not significantly increase cell counts. AFL + imiquimod treatment increased CXCL12 serum levels threefold at Day 14 (P = 0.0200).

CONCLUSION

AFL treatment alone and in combination with imiquimod induces substantial tumor clearance associated with local recruitment of innate and adaptive immune cells in UVR-induced murine SCCs. These results may provide a basis for new immunotherapeutic approaches to KC treatment.

Solar Freckles: Long-Term Photochromic Tattoos for Intradermal Ultraviolet Radiometry

While tattooable nanotechnology for in-skin sensing and communication has been a popular concept in science fiction since the 1990s, the first tattooable intradermal nanosensors have only emerged in the past few years, and none have been demonstrated in human skin. We developed a photochromic tattoo that serves as an intradermal ultraviolet (UV) radiometer that provides naked-eye feedback about UV exposure in real time. These small tattoos, or "solar freckles", comprise dermally implanted colorimetric UV sensors in the form of nanoencapsulated leuco dyes that become more blue in color with increasing UV irradiance. We demonstrate the tattoos' functionality for both quantitative and naked-eye UV sensing in porcine skin ex vivo, as well as in human skin in vivo. Solar freckles offer an alternative and complementary approach to self-monitoring UV exposure for the sake of skin cancer prevention. Activated solar freckles provide a visual reminder to protect the skin, and their color disappears rapidly upon removal of UV exposure or application of topical sunscreen. The sensors are implanted in a minimally invasive procedure that lasts only a few seconds, yet remain functional for months to years. These semipermanent tattoos provide an early proof-of-concept for long-term intradermal sensing nanomaterials that provide users with biomedically relevant information in the form of an observable color change.

[Melanoma within tattoos: Two cases and a systematic literature review]

BACKGROUND

There have been reports of malignant melanoma arising within tattoos. However, there is no clear relationship between tattoos and the development of cutaneous malignancies. We report two new cases of melanoma and provide a review of cases of melanoma reported in the medical literature.

PATIENTS AND METHODS

Case No. 1: a 61-year-old patient consulted following the appearance one year ago of a nodular lesion measuring 4.5×3cm on a blue and red tattoo on his back. Complete excision of the lesion with histological analysis revealed an ulcerated nodular melanoma with a Breslow depth of 7mm. No secondary sites were found. Case No. 2: a 39-year-old patient with a blue tattoo on his left arm consulted following the appearance of a pigmented lesion a few months earlier. Surgical excision was immediately performed, confirming the diagnosis of SSM, with a Breslow depth of 0.9mm. There was no sign of relapse 9 years later.

DISCUSSION

In our systematic review we noted 34 cases of melanoma occurring in tattoos. There was a high male prevalence (90.3%) and a relatively young mean age (45.9 years). Most tattoos were monochrome (71.0%). The average time between tattooing and onset of melanoma was 13.2 years. The most common sites of melanoma were the upper limbs (53.1%) and trunk (34.4%). Mean tumor size was 11.6mm. Histologic examination revealed 2 cases of melanoma in situ, and in 13 cases, the Breslow depth was 1mm or less. In 5 cases, macroscopic or microscopic lymph node metastasis (sentinel lymph node) was found at diagnosis, and in one case, in transit skin metastases were also observed at the time of diagnosis. We discuss the hypothetical pathogenic role of tattoos in melanoma.

Safety of tattoos and permanent make-up: a regulatory view

The continuous increase in the popularity of tattoos and permanent make-up (PMU) has led to substantial changes in their societal perception. Besides a better understanding of pathological conditions associated with the injection of highly diverse substances into subepidermal layers of the skin, their regulation has occupied regulatory bodies around the globe. In that sense, current regulatory progress in the European Union is an exemplary initiative for improving the safety of tattooing. On one hand, the compilation of market surveillance data has provided knowledge on hazardous substances present in tattoo inks. On the other hand, clinical data gathered from patients enabled correlation of adverse reactions with certain substances. Nevertheless, the assessment of risks remains a challenge due to knowledge gaps on the biokinetics of highly complex inks and their degradation products. This review article examines the strategies for regulating substances in tattoo inks and PMU in light of their potential future restriction in the frame of the REACH regulation. Substance categories are discussed in terms of their risk assessment and proposed concentration limits.

An update on cutaneous complications of permanent tattooing

Introduction: Decorative tattooing involves the introduction of exogenous pigments and/or dyes into the dermis to produce a permanent design.Areas covered: This review provides an overview of the current aspects of cutaneous complications associated with permanent tattooing and permanent make-up based on the previous reviews of interest, case series, and case reports of interest. References for this review were found through a search of PubMed by use of the terms 'tattoo', 'tattoos', or 'tattooing'.Expert opinion: Complications include primarily infections, allergy to tattoo pigments, benign, and sometimes malignant tumors arising on tattoos and the localization of various dermatoses to tattoos. Immunocompromised patients and individuals with chronic conditions should be able to discuss with their physician and ask advice before getting tattooed. Tattoo color allergy still remains an unsolved issue. The identification of current culprit failed. It is most likely a byproduct that appears in situ in the skin during the life of the tattooed bearer. Studies involving expert centers are warranted to establish the best treatments for tattoo allergy. The risk of tattoo associated cancers appears to this author as largely overstated. However, case controls studies on large on cohorts of individuals with or without tattoos could help to evaluate whether tattoos have a possible in role in cancers.

Atypical Intraepidermal Melanocytic Proliferation Masked by a Tattoo: Implications for Tattoo Artists and Public Health Campaigns

Tattoos have become increasingly popular worldwide. While tattoos carry a minimal risk of complications, previous reports have located malignant melanoma hidden within tattoos. We present a case of an atypical intraepidermal melanocytic proliferation masked by a large tattoo in a 39-year-old Caucasian male. Tattooed skin can be difficult to examine, particularly when the tattoos are dark, pigmented, and extensive. We demonstrate that a careful examination of tattooed skin leads to the early detection of atypical melanocytic proliferations. We present an extensive review of literature related to the relationship between tattoos and skin cancer, as well as public health recommendations for tattoo artists and individuals seeking to obtain tattoos. We urge a vigilant examination of tattooed skin and encourage collaboration between dermatologists and tattoo artists in promoting the detection of suspicious lesions prior and following tattooing.

Repeated Treatments with Ingenol Mebutate Prevents Progression of UV-Induced Photodamage in Hairless Mice

Background and Aim

Ingenol mebutate (IngMeb) is an effective treatment for actinic keratosis. In this study, we hypothesized that repeated treatments with IngMeb may prevent progression of UV-induced photodamage, and that concurrent application of a corticosteroid may reduce IngMeb-induced local skin responses (LSR).

Methods

Hairless mice (n = 60; 3 groups of 20 mice) were irradiated with solar simulated ultraviolet radiation (UVR) throughout the study. Five single treatments with IngMeb were given at 4-week intervals (Days 21, 49, 77, 105, and 133). Clobetasol propionate (CP) was applied once daily for 5 days prior to each IngMeb application, as well as 6 h and 1 day post treatment. One week after IngMeb treatment No. 1, 3, and 5 (Days 28, 84, and 140), biopsies from four mice in each group were collected for histological evaluation of UV-damage on a standardized UV-damage scale (0–12). LSR (0–24) were assessed once daily (Days 1–7) after each IngMeb treatment.

Results

IngMeb prevented progression of photodamage in terms of keratosis grade, epidermal hypertrophy, dysplasia, and dermal actinic damage with a lower composite UV-damage score on day 140 (UVR 10.25 vs. UVR+IngMeb 6.00, p = 0.002) compared to UVR alone. IngMeb induced LSR, including erythema, flaking, crusting, bleeding, vesiculation, and ulceration. Concurrent CP increased LSR (max LSR Tx 1–5: UVR+IngMeb+CP 3.6–5.5 vs. UVR+IngMeb 2.6–4.3) and provided better prevention of photodamage compared to IngMeb alone (Day 140: UVR+IngMeb 6.00 vs. UVR+IngMeb+CP 3.00 p < 0.001).

Conclusion

Repeated field-directed treatments with IngMeb prevent progression of cutaneous photodamage in hairless mice, while CP cannot be used to alleviate IngMeb-induced LSR. The findings suggest that IngMeb may potentially serve as a prophylactic treatment for UV-induced tumors.

Skin tumor development after UV irradiation and photodynamic therapy is unaffected by short-term pretreatment with 5-fluorouracil, imiquimod and calcipotriol. An experimental hairless mouse study

BACKGROUND

Photodynamic therapy (PDT) delays ultraviolet (UV) radiation-induced squamous cell carcinomas (SCCs) in hairless mice. Efficacy may be enhanced by combining PDT with antineoplastic or pro-differentiating agents. We investigated if pretreatment with 5-fluorouracil (5FU), imiquimod (IMIQ) or calcipotriol (CAL) before PDT further delays tumor onset.

METHODS

Hairless mice (n=224) were exposed 3 times weekly to 3 standard erythema doses (SED) of UV radiation. Methyl-aminolevulinate (MAL)-PDT sessions were given on days 45 and 90 before SCC development. Three applications of topical 5FU, IMIQ or CAL were given before each PDT session. Fluorescence photography quantified protoporphyrin IX (PpIX) formation.

RESULTS

PDT delayed UV-induced SCC development by 59 days (212 days UV-MAL-PDT vs. 153 days UV-control, P<0.001). Pretreatment with 5FU, IMIQ or CAL before PDT did not further delay SCC onset compared to PDT alone (207 days UV-5FU-MAL-PDT, 215 days UV-IMIQ-MAL-PDT, 206 days UV-CAL-MAL-PDT vs. 212 days UV-MAL-PDT, P=ns). PpIX fluorescence intensified by 5FU-pretreatment (median 21,392 au UV-5FU-MAL-PDT, P=0.011), decreased after IMIQ-pretreatment (12,452 au UV-IMIQ-MAL-PDT, P<0.001), and was unaffected by CAL-pretreatment (19,567 au UV-CAL-MAL-PDT, P=ns) compared to MAL alone (18,083 au UV-MAL-PDT).

CONCLUSIONS

Short-term three-day pretreatment with 5FU, IMIQ and CAL before PDT does not further delay tumor onset in UV-exposed hairless mice.