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.

A Skin Cancer Prophylaxis Study in Hairless Mice Using Methylene Blue, Riboflavin, and Methyl Aminolevulinate as Photosensitizing Agents in Photodynamic Therapy

The high incidence of sunlight-induced human skin cancers reveals a need for more effective photosensitizing agents. In this study, we compared the efficacy of prophylactic photodynamic therapy (PDT) when methylene blue (MB), riboflavin (RF), or methyl aminolevulinate (MAL) were used as photosensitizers. All mice in four groups of female C3.Cg/TifBomTac hairless immunocompetent mice (N = 100) were irradiated with three standard erythema doses of solar-simulated ultraviolet radiation (UVR) thrice weekly. Three groups received 2 × 2 prophylactic PDT treatments (days 45 + 52 and 90 + 97). The PDT treatments consisted of topical administration of 16% MAL, 20% MB, or 20% RF, and subsequent illumination that matched the photosensitizers’ absorption spectra. Control mice received no PDT. We recorded when the first, second, and third skin tumors developed. The pattern of tumor development after MB-PDT or RF-PDT was similar to that observed in irradiated control mice (p > 0.05). However, the median times until the first, second, and third skin tumors developed in mice given MAL-PDT were significantly delayed, compared with control mice (256, 265, and 272 vs. 215, 222, and 230 days, respectively; p < 0.001). Only MAL-PDT was an effective prophylactic treatment against UVR-induced skin tumors in hairless mice.

The long-term risk of lymphoma and skin cancer did not increase after topical calcineurin inhibitor use and phototherapy in a cohort of 25,694 patients with vitiligo

BACKGROUND

Topical calcineurin inhibitors have been used to treat vitiligo, either alone or in combination with phototherapy; however, the long-term safety of these agents remains controversial.

OBJECTIVE

To investigate the risk of lymphoma and skin cancer in vitiligo patients who received topical calcineurin inhibitors or phototherapy.

METHODS

A multicenter retrospective cohort study of 25,694 vitiligo patients who received topical calcineurin inhibitors or phototherapy for 6 weeks or more between 2001 and 2019 was performed. Cumulative doses of topical calcineurin inhibitors and total phototherapy sessions were determined. Outcomes were the development of lymphoma or skin cancer after enrollment, confirmed through chart review and pathology reports.

RESULTS

During 95,203 person-years, 13 cases of lymphoma, 22 of actinic keratosis, 15 of nonmelanoma skin cancer, and 5 of melanoma were observed. The risk of lymphoma and skin cancer was not significantly increased by topical calcineurin inhibitor dose or phototherapy sessions. The interaction between the topical calcineurin inhibitors and phototherapy was not associated with an increased risk of skin cancer.

LIMITATIONS

Retrospective study, individual follow-up duration less than 4 years, and no adjustment for comorbidities and medication history. Not generalizable to other races.

CONCLUSION

The long-term risk of skin cancer or lymphoma was not associated with the use of topical calcineurin inhibitors, phototherapy, and both treatments in combination in patients with vitiligo.

[UV phototherapy : UV phototherapy and photodiagnostics-a practical overview]

UV phototherapy is an essential and efficient therapeutic option in the treatment of dermatological diseases. It is an integral part of multiple guidelines and maintains its high clinical significance despite the development of new therapeutic options for systemic treatment. Due to the difficult revenue situation, the market for ready-to-use products of psoralen and UV therapy devices is constantly changing.

Impact of UVR Exposure Pattern on Squamous Cell Carcinoma-A Dose-Delivery and Dose-Response Study in Pigmented Hairless Mice

Cumulative lifetime ultraviolet radiation (UVR) is an important factor in the development of squamous cell carcinoma. This study examines the impact of UVR exposure pattern on tumor development. Hairless C3.Cg/TifBomTac immunocompetent pigmented mice (n = 351) were irradiated with 12 standard erythema doses (SED)/week, given as 2 SED ×6, 3 SED ×4, 4 SED ×3, or 6 SED ×2 (dose-delivery study) or 0, 0.6, 1.2, 2, 3 or 4 SED ×3/week (dose-response study). All mice were irradiated until development of 3 tumors of 4 mm each. Pigmentation was measured once monthly. In the dose-delivery study, the median time until tumor development was independent of dose fractions. In the dose-response study, higher UVR doses resulted in faster tumor appearance. When the weekly UVR dose was decreased from 12 to 6 SED, the cumulative UVR dose needed for tumor development was reduced by 40%. In conclusion, delivery schedules of a fixed weekly UVR dose did not affect tumor development. When using different weekly UVR doses, longer time to tumor development was observed using lower UVR doses. Lower weekly UVR doses however resulted in lower cumulative UVR doses to induce tumors in hairless pigmented mice.

Pimecrolimus Is a Potent Inhibitor of Allergic Reactions to Hymenopteran Venom Extracts and Birch Pollen Allergen In Vitro

Pimecrolimus (Elidel, SDZ ASM 981) is an anti-inflammatory and immunomodulatory 33-epichloro-derivative of macrolactam ascomycin, with low potential for affecting systemic immune responses compared with other calcineurin inhibitors, cyclosporin A and tacrolimus. Despite numerous studies focused on the mechanism of pimecrolimus action on mast cells, only the single report has addressed pimecrolimus effects on other typical FcεRI-expressing cells, the basophils. Patients allergic to birch pollen (n = 20), hymenopteran venoms (n = 23) and 10 non-allergic volunteers were examined. Primary human basophils pre-treated or not with 0.5-50 μMol pimecrolimus were exposed to various concentrations of recombinant Bet v 1a allergen, bee or wasp venom extracts and anti-IgE for 20 min, and then examined for the expression of CD45, CD193, CD203c, CD63 and CD164 using flow cytometry. The externalization of basophil activation markers (CD63 and CD164) was equally inhibited through pimecrolimus in cells activated by recombinant pollen allergen, hymenopteran venom extracts and anti-IgE. Although the individual response rate was subject to strong variation, importantly, pre-treatment with pimecrolimus lowered the number of activated basophils in response to any of the stimuli in the basophils from all patients. The inhibition was concentration-dependent; approximately half of the basophils were inhibited in the presence of 2.5 mMol pimecrolimus. Pimecrolimus is a valuable new tool for the inhibition of hyper-reactive basophils in patients with pollen allergy and a history of anaphylactic reactions to bee or wasp venoms. Further research should address short-term use of pimecrolimus in vivo in a wide spectrum of allergic diseases.

Effects of a sunscreen formulation on albino hairless mice: a morphological approach

The purpose of the study was to evaluate the effects of a sunscreen formulation on the skin of albino hairless mice subjected to simulated solar light (SSL) in terms of morphological changes. Young adult albino hairless mice HRS/J (n = 36) were used as an experimental model for determining skin photoaging changes. Mice were irradiated with SSL, and the sunscreen (estimated SPF 30, PF-UVA) was obtained from the Pharmacy College/UFRJ, Brazil. The animals were divided into four groups: non-treated (G1), radiation only (G2), sunscreen-treated (G3) and vehicle + radiation (G4). Animals from groups G2, G3 and G4 were irradiated weekly (5 weeks), with no immobilization. One week after the final exposure, the dorsal skin was observed using a dermatoscopic camera. Biopsies were analyzed in order to quantify neovascularization and to evaluate histological aspects of the skin. Neovascularization was also evaluated with immunohistochemical reactions for the Von Willebrand factor. Animals from G2 displayed classical morphological changes denoting skin photoaging: thickening of the epidermis, increased dermal cellularity, follicular keratosis, sebaceous gland hyperplasia, and angiogenesis. Animals from groups G3 and G1 displayed similar morphological profiles, without these changes. Animals from group G4 showed more morphological changes than group G2, emphasizing the relative importance of the putative photosensitizing components present in the vehicle formulation. The extent of the morphological skin changes suggested that the sunscreen formulation was effective against SSL, and showed the importance of assessing the phototoxicity of vehicle formulations.

Topical nutlin-3a does not decrease photocarcinogenesis induced by simulated solar radiation in hairless mice

BACKGROUND

Nutlin-3a increases p53 levels after UVB radiation, which could result in a decrease in DNA damage and thus lead to a lower risk of non-melanoma skin cancer. Especially, organ transplant recipients might derive benefit from such a topical formulation with an active ingredient to prevent DNA damage.

PURPOSE

To investigate whether topical nutlin-3a can decrease photocarcinogenesis induced by simulated solar radiation.

METHODS

72 hairless C3.Cg/TifBomTac mice were treated 3 days/week topically with 100 μl nutlin-3a (9 mM) [Groups 1 and 3 (120 days)) or 100 μl vehicle (Group 2). Three hours later, all mice were exposed to simulated solar radiation (a radiometric equivalent of three standard erythema dose units).

RESULTS

The median time to tumours did not differ between the mice treated with nutlin-3a and with the vehicle. The median time to the first and second tumours did not differ between 'nutlin-3a-120 days' and vehicle-treated mice, but there was a small significant difference in the median time to the third tumour (211 vs. 196 days, P = 0.043). However, after Bonferroni correction, there was no difference at all.

CONCLUSION

Nutlin-3a had no reductive effect on photocarcinogenesis and we do not believe in nutlin-3a as a potential drug against DNA damage in a topical formulation for organ transplant patients.

Neonatal mice do not have increased sensitivity to induction of squamous cell carcinomas

BACKGROUND

Squamous cell carcinoma (SCC) is linked with the lifelong cumulative effect of ultraviolet radiation (UVR). In contrast, epidemiological data have shown that sunburn in childhood is a stronger risk factor for cutaneous malignant melanoma than continuous UVR, indicating a higher carcinogenic sensitivity early in life.

METHODS

We investigated how a high neonatal dose of UVR affects the development of SCC in mice irradiated later in life. We used simulated solar radiation (sun) and solarium radiation (solarium). Ninety-nine C3.Cg/TifBomTac-immunocompetent hairless mice received 0, 25 or 35 standard erythema doses (SED) UVR when they were 4 days old followed by 4 SED sun or 4 SED solarium three times/weekly from 9 weeks of age.

RESULTS

Tumours developed faster in mice treated with 35 SED UVR + 4 SED sun compared with 4 SED sun, but no change was observed in the cumulative dose required to achieve tumours. Tumours also developed faster in mice treated with 35 SED UVR + 4 SED solarium compared with 4 SED solarium, and a difference was also observed in the cumulative dose required to achieve tumours. If the Skin Cancer Utrecht-Philadelphia-murine spectrum was used to weigh the delivered irradiance instead of the International Commission on Illumination erythema action spectrum, tumours developed after the same accumulated dose.

CONCLUSION

In conclusion, this study does not indicate increased sensitivity to induction of SCC early in life.

Effects of pimecrolimus versus triamcinolone on Langerhans cells after UV exposure

BACKGROUND/PURPOSE

Pimecrolimus is a topical immunomodulator for atopic dermatitis. Concerns regarding malignancy risk resulted in its black box warning in 2006. The purpose of this study is to determine the effects of pimecrolimus on Langerhans cells (LC), mediators of the cutaneous immunity UV-irradiated skin.

METHODS

A RCT was conducted investigating pimecrolimus 1% cream vs triamcinolone 0.1% cream on UV-irradiated epidermal LC on 20 healthy volunteers. Punch biopsies were stained with antibodies to CD1a, HLADR and CD83.

RESULTS

Triamcinolone caused more depletion in UV-irradiated CD1a(+) epidermis relative to pimecrolimus treatment. (P=0.030). Using HLA-DR as a pan-marker for APCs, pimecrolimus caused marginally less depletion than triamcinolone (P=0.013). Using anti-CD83 as a maturation marker, UV-irradiated skin treated with pimecrolimus showed more mature LC than skin treated with triamcinolone (P=0.00090).

CONCLUSION

UV-induced changes in LC are minimally affected by pimecrolimus, compared with triamcinolone.

High death rate in mice treated topically with diclofenac

Recently, 3% diclofenacnatrium gel (diclofenac) was introduced for the treatment of actinic keratoses. Data on photocarcinogenesis of topical diclofenac are limited, and we wished to investigate whether topical diclofenac can accelerate photocarcinogenesis using simulated solar radiation (SSR). Diclofenac was applied topically on the backs of hairless, female, C3.Cg/TifBomTac immunocompetent mice three times weekly followed by ultraviolet radiation (2, 3, or 4 Standard Erythema Dose) until death. There was a significant difference in survival between diclofenac-treated groups and control groups (P<0.0001). Physical examination of the diclofenac-treated mice showed peptic ulcers, oesophageal ulcers and gastrointestinal bleeding. To be sure that these side effects were not caused by topical absorption without oral ingestion, one group of mice was wearing Elizabethan collars and was single housed. Nevertheless, these mice also had gastrointestinal side effects. We terminated the experiment after 151 days when only a few mice remained in the diclofenac-treated groups and most had symptoms of discomfort and weight loss. No tumors developed as a result of the early termination.

Critical Review of Preclinical Approaches to Evaluate the Potential of Immunosuppressive Drugs to Influence Human Neoplasia

Many immunosuppressive drugs are associated with an increased risk of B-cell lymphoma, squamous cell carcinoma, and Kaposi sarcoma. Thirteen immunosuppressive drugs have been tested in 2-year carcinogenicity studies (abatacept; azathioprine; busulfan; cyclophosphamide; cyclosporine; dexamethasone; everolimus; leflunomide; methotrexate; mycophenolate mofetil; prednisone; sirolimus; and tacrolimus) and in additional models including neonatal and genetically modified mice; chemical, viral, ultraviolet, and ionizing radiation co-carcinogenesis, and in models with transplanted tumor cells. The purpose of this review is to outline the mechanisms by which immunosuppressive drugs can influence neoplasia, to summarize the available preclinical data on the 13 drugs, and to critically review the performance of the models. A combination of primary tumor and metastasis assays conducted with transplanted cells may provide the highest value for hazard identification and can be applied on a case-by-case basis. However, for both small molecules and therapeutic proteins, determining the relative risk to patients from preclinical data remains problematic. Classifying immunosuppressive drugs based on their mechanism of action and hazard identification from preclinical studies and a prospective pharmacovigilance program to monitor carcinogenic risk may be a feasible way to manage patient safety during the clinical development program and postmarketing.

Photocarcinogenicity of selected topically applied dermatological drugs: calcineurin inhibitors, corticosteroids, and vitamin D analogs

Topical therapies constitute the mainstay of dermatological treatments for skin disorders, such as atopic dermatitis, contact dermatitis, psoriasis, or acne. Since some of these diseases are often chronic, treatment duration may last for years and may even last the patient's entire lifetime. Obviously, such long-term therapy may raise safety concerns, which also include the potential photocarcinogenic effect. Most patients are exposed to ultraviolet radiation (UVR) during leisure, work, vacations, or in tanning beds. Additionally, the patients may receive UVR via UVB phototherapy or psoralens plus UVA radiation (PUVA). The use of immunosuppressant's, such as corticosteroids and calcineurin inhibitors, has markedly increased. Patients with skin diseases have benefited from both systemic and topical treatment of both new and established drugs. The issue of a black box warning by the US Food and Drug Administration has increased concerns about photocarcinogenesis, which raises the question: "Are these drugs safe?" This review focuses on the mechanism of action and photocarcinogenic potential of commonly used topical treatments, such as corticosteroids, calcineurin inhibitors, and vitamin D analogs.

Topical pimecrolimus: a review of its use in the management of pediatric atopic dermatitis

Topical pimecrolimus 1% cream (Elidel) [hereafter referred to as topical pimecrolimus] is a nonsteroidal alternative in the treatment of pediatric atopic dermatitis. In vehicle-controlled, short-term, continuous-use trials in pediatric patients with mild to moderate atopic dermatitis, topical pimecrolimus was effective in treating disease symptoms. Topical pimecrolimus was effective in preventing disease flares and reducing the need for topical corticosteroids in longer term, intermittent-use trials. In addition, topical pimecrolimus was associated with improvements in the health-related quality of life (HR-QOL) of pediatric patients with atopic dermatitis and their parents. In vehicle-controlled trials, topical pimecrolimus was generally as well tolerated as vehicle. Topical pimecrolimus showed similar efficacy to topical tacrolimus 0.03% ointment (hereafter topical tacrolimus) in a short-term, continuous-use trial and the two agents had a generally similar tolerability profile. Although comparative data between topical pimecrolimus and topical corticosteroids are lacking in pediatric patients, and the long-term tolerability (beyond 1-2 years) of topical pimecrolimus is yet to be established, topical pimecrolimus is a useful agent in the management of pediatric patients with mild to moderate atopic dermatitis who do not achieve satisfactory treatment with other topical pharmacologic treatments, including topical corticosteroids.