Ingenol Mebutate Field-Directed Treatment of UVB-Damaged Skin Reduces Lesion Formation and Removes Mutant p53 Patches

Characterization of Permeability Barrier Dysfunction in a Murine Model of Cutaneous Field Cancerization Following Chronic UV-B Irradiation: Implications for the Pathogenesis of Skin Cancer

Simple Summary

In the present work, we developed an experimental preclinical model of skin with cutaneous field cancerization after chronic UV-B light exposure in an immunologically intact mouse model (SKH1 aged mice). We observed impairments in the transepidermal water loss, stratum corneum hydration, and surface pH. We also detected a marked hyperkeratotic hyperplasia of the epidermis, induction of keratinocyte hyperproliferation, incidental actinic keratosis, and in situ squamous cell carcinomas in the UV-B light-irradiated groups. In this context, the association between the permeability barrier impairment and keratinocyte hyperproliferation might be considered a new target in the management of skin with cutaneous field cancerization. As current therapeutic approaches to actinic keratosis and cutaneous field cancerization only focus on the direct antineoplastic, immunomodulatory, or photodynamic effects of approved topical drugs, this mouse model of skin with cutaneous field cancerization might be helpful for both the identification and screening of potentially new preventive strategies or treatments (e.g., skin barrier therapies).

Abstract

Chronic ultraviolet B (UV-B) irradiation is known to be one of the most important hazards acting on the skin and poses a risk of developing photoaging, skin with cutaneous field cancerization (CFC), actinic keratosis (AKs), and squamous cell carcinomas (SCCs). Most of the UV-B light is absorbed in the epidermis, affecting the outermost cell layers, the stratum corneum, and the stratum granulosum, which protects against this radiation and tries to maintain the permeability barrier. In the present work, we show an impairment in the transepidermal water loss, stratum corneum hydration, and surface pH after chronic UV-B light exposure in an immunologically intact mouse model (SKH1 aged mice) of skin with CFC. Macroscopic lesions of AKs and SCCs may develop synchronically or over time on the same cutaneous surface due to both the presence of subclinical AKs and in situ SCC, but also the accumulation of different mutations in keratinocytes. Focusing on skin with CFC, yet without the pathological criteria of AKs or SCC, the presence of p53 immunopositive patches (PIPs) within the epidermis is associated with these UV-B-induced mutations. Reactive epidermis to chronic UV-B exposure correlated with a marked hyperkeratotic hyperplasia, hypergranulosis, and induction of keratinocyte hyperproliferation, while expressing an upregulation of filaggrin, loricrin, and involucrin immunostaining. However, incidental AKs and in situ SCC might show neither hypergranulosis nor upregulation of differentiation markers in the upper epidermis. Despite the overexpression of filaggrin, loricrin, involucrin, lipid enzymes, and ATP-binding cassette subfamily A member 12 (ABCA12) after chronic UV-B irradiation, the permeability barrier, stratum corneum hydration, and surface pH were severely compromised in the skin with CFC. We interpret these results as an attempt to restore the permeability barrier homeostasis by the reactive epidermis, which fails due to ultrastructural losses in stratum corneum integrity, higher pH on skin surface, abundant mast cells in the dermis, and the common presence of incidental AKs and in situ SCC. As far as we know, this is the first time that the permeability barrier has been studied in the skin with CFC in a murine model of SCC induced after chronic UV-B irradiation at high doses. The impairment in the permeability barrier and the consequent keratinocyte hyperproliferation in the skin of CFC might play a role in the physiopathology of AKs and SCCs.

Regional Variation in Epidermal Susceptibility to UV-Induced Carcinogenesis Reflects Proliferative Activity of Epidermal Progenitors

To better understand the influence of ultraviolet (UV) irradiation on the initial steps of skin carcinogenesis, we examine patches of labeled keratinocytes as a proxy for clones in the interfollicular epidermis (IFE) and measure their size variation upon UVB irradiation. Multicolor lineage tracing reveals that in chronically irradiated skin, patches near hair follicles (HFs) increase in size, whereas those far from follicles do not change. This is explained by proliferation of basal epidermal cells within 60 μm of HF openings. Upon interruption of UVB, patch size near HFs regresses significantly. These anatomical differences in proliferative behavior have significant consequences for the cell of origin of basal cell carcinomas (BCCs). Indeed, a UV-inducible murine BCC model shows that BCC patches are more frequent, larger, and more invasive near HFs. These findings have major implications for the prevention of field cancerization in the epidermis.

Mouse models for actinic keratoses

Actinic keratoses (AKs) represent a premalignant skin condition due to chronic sun damage that dramatically increases in prevalence in the aging population. Currently, animal models of AKs utilize photocarcinogenesis, chemical carcinogens, or targeted gene modulation, and each method possesses unique strengths and weaknesses. Models using photodamage most comprehensively describe methods for preferentially selecting AK lesions, while replicating the pathogenesis of AKs with greater fidelity than models utilizing other carcinogenic methods. The following review of current murine models of AKs will aid in the selection of mouse models appropriate for future in vivo studies to test the efficacy of novel therapeutic agents for the treatment of AKs.

Whole-mount staining coupled to a UV-inducible basal cell carcinoma murine model

The origin of basal cell carcinomas (BCC) remains elusive. This protocol combines the use of an ultraviolet (UV)-inducible BCC murine model (K14CrexPtch^wt/lox) and an optimized protocol for florescent whole-mount cytokeratin 17 immunostaining to address the spatiotemporal dynamics of BCC formation. The high-resolution three-dimensional confocal images are an excellent tool to visualize and quantify the distribution of skin cancers at a given time point. For complete details on the use and execution of this protocol, please refer to Roy et al. (2020).

Actinic Keratoses: Reconciling the Biology of Field Cancerization with Treatment Paradigms

This Perspective briefly reviews the relationship between UV-induced mutations in habitually sun-exposed human skin and subsequent development of actinic keratoses (AKs) and skin cancers. It argues that field therapy rather than AK-selective therapy is the more logical approach to cancer prevention and hypothesizes that treatment early in the process of field cancerization, even prior to the appearance of AKs, may be more effective in preventing cancer as well as more beneficial for and better tolerated by at-risk individuals. Finally, the Perspective encourages use of rapidly advancing DNA analysis techniques to quantify mutational burden in sun-damaged skin and its reduction by various therapies.

Sequential daylight photodynamic therapy and ingenol mebutate versus 2 sessions of daylight photodynamic therapy for the treatment of actinic keratosis: An observational, prospective, comparative study

BACKGROUND

Field-directed therapy, such as daylight-photodynamic therapy (DL-PDT) or ingenol mebutate (IM), is indicated for multiple actinic keratosis (AK) lesions located on contiguous areas of skin with significant sun damage.

OBJECTIVE

To compare the efficacy of sequential DL-PDT and IM treatment with that of 2 sessions of DL-PDT in AK patients.

MATERIAL AND METHODS

For this observational, multicenter, prospective study we recruited patients for whom DL-PDT was indicated for the treatment of AK lesions (grades I and II) located on the head. After 1 month of follow-up those who did not achieve a satisfactory clinical response received either a second session of DL-PDT or were treated with IM. Epidemiological and clinical data were collected and analyzed.

RESULTS

Forty-three patients were enrolled (39 male, 4 female). The mean (standard deviation, SD) age was 78 (7.84) years, and the mean (SD) number of AK lesions per patient was 9.58 (1.16). After the first session of DL-PDT, 27 patients (62.8%) required further treatment: 13 (48.1%) received a second session of DL-PDT and 14 (51.9%) were treated with IM. After 1 year of follow-up, lesion clearance rates were higher in patients who received 2 sessions of DL-PDT than those treated with sequential DL-PDT plus IM (75.2%vs 54.6%, p = 0.0013). Local skin reactions were more frequent in the DL-PDT plus IM group than the group treated with 2 sessions of DL-PDT (p = 0.0245).

CONCLUSIONS

The combination of DL-PDT plus IM appears to have no synergistic effect in the treatment of field cancerization, and offers no benefits over 2 sessions of DL-PDT monotherapy, although both combinations produced high lesion clearance rates, a good safety profile, excellent cosmetic outcome, and good patient satisfaction.

Ingenol mebutate-mediated reduction in p53-positive keratinocytes in skin cancerization field directly correlates with clinical response in patients with multiple actinic keratoses

BACKGROUND

UV radiation represents the main risk factor for non-melanoma skin cancers. Chronic UV exposure induces 'p53 patches', i.e. clonal outgrowths of keratinocytes with high nuclear expression of mutated p53, which might progress to actinic keratosis (AK) and ultimately squamous cell carcinomas (SCCs).

AIMS

Analysis of ingenol mebutate gel (150 and 500 mcg/g) effects in the reduction in 'p53 patches' inside skin cancerization field (CF) in patients with multiple AKs of face/scalp or trunk/extremities, in order to investigate whether the expected reduction in p53⁺ keratinocytes might have a direct role in the long-term AK reduction in treated areas.

RESULTS

We enrolled n = 10 patients, treated with ingenol mebutate and evaluated at 2 and 6 months after treatment. We observed clinical responses in the majority of patients (n = 7), with AK reduction or complete clearance (n = 6 and n = 1, respectively). Notably, two patients did not respond to the treatment, and in one patient, after initial partial response, new lesion was recorded. In untreated skin CF samples (n = 3), we observed numerous p53⁺ keratinocytes, similar to those observed in invasive SCC samples (53.56 ± 8.79 and 74.34 ± 22.05, respectively; P = 0.2). After treatment, we observed a variable p53⁺ keratinocyte reduction in CF samples at 2 months (24.67 ± 31.19; P = 0.19). Importantly, the amount of p53⁺ keratinocytes strongly and directly correlated with AK number (R²  = 0.81).

CONCLUSION

Untreated skin CF expresses high level of p53⁺ keratinocytes as invasive SCC. Ingenol mebutate is able to reduce p53⁺ keratinocytes with variable efficacy, this reduction degree directly correlating with clinical efficacy.

Mediators of Inflammation in Topical Therapy of Skin Cancers

Taking into consideration that the immune system plays a very important role in the development of melanoma and non-melanoma skin cancers, which have a high prevalence in immunosuppressed patients and after prolonged ultraviolet radiation, the interest in developing novel therapies, in particular targeting the inflammation in cancer, has increased in the past years. The latest data suggest that therapies such as imiquimod (IMQ), ingenol mebutate (IM), 5-fluorouracil (5-FU), retinoids, and nonsteroidal anti-inflammatory drugs (NSAIDs) have been used with success in the topical treatment of some cancers. Herein, we review the topical treatment targeting the inflammation in skin cancer and the mechanisms involved in these processes. Currently, various associations have shown a superior success rate than monotherapy, such as systemic acitretin and topical IMQ, topical 5-FU with tretinoin cream, or IMQ with checkpoint inhibitor cytotoxic T lymphocyte antigen 4. Novel therapies targeting Toll-like receptor-7 (TLR-7) with higher selectivity than IMQ are also of great interest.

Application of dynamic thermal imaging in a photocarcinogenesis mouse model

INTRODUCTION

In clinical practice and experimental settings, cutaneous premalignant and malignant lesions are commonly diagnosed by histopathological biopsy. However, this technique is invasive and results in functional or cosmetic defects. Dynamic thermal imaging is a non-invasive technique that quantifies the infra-red (IR) radiation emitted by a subject after the introduction of external thermal stimuli (such as heat or cold).

METHODS

Forty hairless albino (Crl:SKH1-hr) mice were randomised to the control group or the experimental group. The experimental group was regularly irradiated with artificial ultraviolet. Clinical photographs, immunohistochemical staining and dynamic thermal imaging results of both groups were obtained.

RESULTS

As photocarcinogenesis proceeded, faster thermal recovery to basal temperature after heat stimuli was significant on dynamic thermal imaging. With histopathological correlations, it was possible to differentiate normal, premalignant and malignant cutaneous lesions according to thermal imaging results. CD 31 staining analysis showed that increased vasculature was the key change responsible for different thermal imaging results among photocarcinogenesis steps.

CONCLUSIONS

Dynamic thermal imaging is useful to differentiate normal, premalignant and malignant cutaneous lesions. Increased vasculature is the key change responsible for different thermal imaging results.

Effect of ingenol mebutate on actinic keratosis in a Korean population: A prospective clinical, dermoscopic and histopathological study from a single center

Actinic keratosis (AK) is an in situ squamous cell carcinoma which is mostly found on sun-damaged skin, and it is prevalent among Caucasians. However, there is a lack of research on evaluating the treatment efficacy of ingenol mebutate (IM) on AK in Asians. This study was intended to analyze the treatment outcomes of IM on AK in Korean patients with regards to clinical, dermoscopic and histopathological aspects. A prospective study on 46 Korean patients who were diagnosed with AK and treated with IM was conducted. Clinically, 80% (24/30) of the patients showed an improvement at 8 weeks. Twenty out of the 30 (66.7%) patients were found to have achieved histopathological clearance. All local skin responses had disappeared at T4 in all patients. Patients with Fitzpatrick skin type III were proven to exhibit better treatment outcomes, both clinically (P = 0.001) and histopathologically (P = 0.001), than those with Fitzpatrick skin type IV. The clinical and histopathological clearance rate of AK with IM in Korean patients was 80% and 66.7%, respectively. The patients with Fitzpatrick skin type IV showed a tendency to have residual AK, histopathologically after treatment with IM. In conclusion, IM could be an effective and safe treatment option on AK in Korean patients. In addition, it would be helpful to carry out a cautious check-up when treating AK with IM in patients with a darker skin color.

Recent advances in field cancerization and management of multiple cutaneous squamous cell carcinomas

Cutaneous squamous cell carcinoma (SCC) is among the most common cancers in humans, and many patients with SCC will develop multiple tumors within their lifetime. The field cancerization concept, originally proposed over 60 years ago, hypothesized that multiple primary cancers may arise simultaneously and coexist with subclinical precursor lesions within a defined field. Genetic sequencing of SCC and precursor lesions has identified what may be the earliest clonal proliferations in SCC development and confirmed that field cancerization in the skin is mediated by ultraviolet radiation. For patients with multiple SCCs and severe actinic damage, treatment of precursor lesions within a cancerized field can decrease the risk of subsequent cancer development. Sunblock is an effective intervention for field cancerization, even in patients with established disease. There is now direct evidence that field therapy with topical 5-fluorouracil is effective in reducing the incidence of subsequent SCC, and there is indirect evidence suggesting that topical imiquimod, topical ingenol mebutate, and photodynamic therapy are similarly effective. There is limited direct evidence to show that systemic acitretin or nicotinamide can decrease incident SCC in patients with field cancerization. In this review, an approach to the management of patients with multiple SCCs and field cancerization is presented along with the rationale to support field-directed therapy.

Dangerous plants in dermatology: Legal and controlled

The plant and mushroom kingdoms have species used for intoxication, inebriation, or recreation. Some of these species are toxic. Given that many of these plants or substances are illegal and have histories of abuse, much of the research regarding therapeutic application is based on basic science, animal studies, and traditional use. This review examines Cannabis, Euphorbia, Ricinus, Podophyllum, Veratrum, mushrooms, and nightshades, along with resveratrol and cocaine as they relate to dermatology.

Ingenol mebutate for the treatment of actinic keratosis: effectiveness and safety in 246 patients treated in real-life clinical practice

INTRODUCTION

The aim of the study was to evaluate the results on effectiveness and safety of topical treatment for actinic keratosis (AK) with ingenol mebutate gel (IMG) in real-life conditions and to perform an analysis of the factors that may influence the treatment outcomes.

MATERIALS AND METHODS

Retrospective study of patients with non-hyperkeratotic AK lesions prescribed with IMG in Spain according to clinical practice. Dermatologists reported the characteristics of patients and AK at baseline, and the findings observed up to 60 d after treatment.

RESULTS AND CONCLUSIONS

A total of 260 treatments in 246 patients with a mean (SD) age 70.6 (10.4) years were reviewed. The number of clinically visible AK in the treated area decreased from 6.16 (3.02) to 1.22 (2.02) (p < .001) lesions with an average reduction of 84%. Univariate analysis showed higher reduction rates when IMG was applied in the face/scalp (p = .026), in women (p = .041), and in patients under 70 years of age (p = .033). According to multivariate analysis, advanced age was associated with worse clearance rates (p = .038). However, besides statistical significance, we can conclude that gender (female) and age (under 70 years-old) show a tendency to have better efficacy outcomes but without clinical relevance. Topical IMG was generally well tolerated and had positive cosmetic results after 60 d. Age influences on IMG effectiveness for AK and LSRs were correlated with higher effectiveness ratios.

Analysis of apoptosis-associated molecules Erythroid differentiation regulator 1, bcl-2 and p53 in actinic keratosis after treatment with ingenol mebutate

Actinic keratosis (AK) is the most common cutaneous premalignant neoplasm precursor of malignant skin tumors. The aberrant apoptotic pathway is thought to be associated with pathogenesis of AK. Ingenol mebutate has been shown to be effective and safe for treatment of AK. However, the effect of ingenol mebutate on apoptosis-related molecules using human skin samples has not been studied well. Erythroid differentiation regulator 1 (Erdr1) was recently reported to play a crucial role in malignant skin cancers like malignant melanoma. The role of Erdr1 in premalignant actinic keratosis (AK) has not been explored. The purpose of this study was to investigate whether the expression of apoptosis-associated molecules such as Erdr1, p53 and bcl-2 was affected by the treatment of ingenol mebutate in AK. Nine patients with AK underwent skin biopsy at baseline and 8 weeks after treatment with ingenol mebutate for immunohistochemical evaluation with Erdr1, p53 and bcl-2. In addition, skin samples from five control subjects were retrieved. Upregulation of Erdr1 and a significant decrease in expression of p53 and bcl-2 were observed after treatment with ingenol mebutate. Ingenol mebutate treatment for AK resulted in the modulation of apoptosis-associated molecules with an increase in the expression of Erdr1 and a decrease in the expression of p53 and bcl-2.

Tattoo removal with ingenol mebutate

An increasing number of people are getting tattoos; however, many regret the decision and seek their removal. Lasers are currently the most commonly used method for tattoo removal; however, treatment can be lengthy, costly, and sometimes ineffective, especially for certain colors. Ingenol mebutate is a licensed topical treatment for actinic keratoses. Here, we demonstrate that two applications of 0.1% ingenol mebutate can efficiently and consistently remove 2-week-old tattoos from SKH/hr hairless mice. Treatment was associated with relocation of tattoo microspheres from the dermis into the posttreatment eschar. The skin lesion resolved about 20 days after treatment initiation, with some cicatrix formation evident. The implications for using ingenol mebutate for tattoo removal in humans are discussed.

Efficacy of ingenol mebutate gel for actinic keratosis in patients treated by thiazide diuretics

Actinic keratosis (AK) is considered as superficial squamous cell carcinoma. Chronic sun exposure plays a central role in its pathogenesis. In particular, ultraviolet B radiation causes direct damage to the DNA, producing pyrimidine dimers that suppress the protective role of p53. Other risk factors include advanced age, male sex, and fair skin type. Even some drugs used for treating blood hypertension, such as thiazide diuretics, can increase the risk of developing AK. Their photosensitizing action seems to be connected with reactive oxygen species production. We report our experience with ten patients affected by multiple AK, in therapy with thiazide diuretics, treated by ingenol mebutate gel. AK was clinically and dermoscopically evaluated at baseline and after 30 days from the beginning of the treatment. Moreover, patients were screened for vitamin D₃ values and reported a general hypovitaminosis status. To our knowledge, we report for the first time the efficacy of ingenol mebutate gel in this group of patients, particularly at risk of developing AK.

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.

Tumor-Preferential Induction of Immune Responses and Epidermal Cell Death in Actinic Keratoses by Ingenol Mebutate

The rapid and strong clinical efficacy of the first-in-class, ingenol mebutate, against actinic keratosis (AK) has resulted in its recent approval. We conducted the first comprehensive analysis of the cellular and molecular mode of action of topical ingenol mebutate 0.05% gel in both AK and uninvolved skin of 26 patients in a phase I, single-center, open-label, within-patient comparison. As early as 1 day after application, ingenol mebutate induced profound epidermal cell death, along with a strong infiltrate of CD4⁺ and CD8⁺ T-cells, neutrophils, and macrophages. Endothelial ICAM-1 activation became evident after 2 days. The reaction pattern was significantly more pronounced in AK compared with uninvolved skin, suggesting a tumor-preferential mode of action. Extensive molecular analyses and transcriptomic profiling of mRNAs and microRNAs demonstrated alterations in gene clusters functionally associated with epidermal development, inflammation, innate immunity, and response to wounding. Ingenol mebutate reveals a unique mode of action linking directly to anti-tumoral effects.

Trial Registration: ClinicalTrials.gov NCT01387711

Ingenol Disoxate: A Novel 4-Isoxazolecarboxylate Ester of Ingenol with Improved Properties for Treatment of Actinic Keratosis and Other Non-Melanoma Skin Cancers

Introduction

Ingenol mebutate gel (Picato^®, LEO Pharma A/S) is approved for the field treatment of actinic keratosis and is characterized by high sustained clearance of actinic lesions. The inherent propensity of ingenol mebutate towards chemical rearrangement necessitates refrigeration of the final product. We sought to identify novel ingenol derivatives with enhanced chemical stability and similar or improved in vitro potency and in vivo efficacy.

Methods

A number of ingenol esters were synthesized with full regiocontrol from ingenol. Chemical stability was determined in aqueous buffer at physiological pH and hydroalcoholic gel at lower pH. Acute cytotoxicity was determined in HeLa or HSC-5 cells. Keratinocyte proliferation, viability and caspase 3/7 activation was measured in primary epidermal keratinocytes. Relative gene expression levels were determined by real-time quantitative PCR. Evaluation of in vivo tumor ablating potential was performed in the murine B16 melanoma mouse model and in the UV-induced skin carcinogenesis model in hairless SKH-1 mice following topical treatment for two consecutive days with test compounds formulated at 0.1% in a hydroalcoholic gel.

Results

This work resulted in the identification of ingenol disoxate (LEO 43204) displaying increased stability in a clinically relevant formulation and in aqueous buffer with minimal pH-dependent acyl migration degradation. Ingenol disoxate exhibited a significantly higher cytotoxic potency relative to ingenol mebutate. Likewise, cell growth arrest in normal human keratinocyte was more potently induced by ingenol disoxate, which was accompanied by protein kinase C dependent transcription of markers of keratinocyte differentiation. Most notably, ingenol disoxate possessed a superior antitumor effect in a B16 mouse melanoma model and significantly increased median survival time relative to ingenol mebutate. A significant effect on tumor ablation was also observed in a murine model of ultraviolet irradiation-induced skin carcinogenesis.

Conclusion

These data illustrate that the favorable in vitro and in vivo pharmacological properties driving ingenol mebutate efficacy are either preserved or improved in ingenol disoxate. In combination with improved chemical stability to potentially facilitate storage of the final product at ambient temperatures, these features support further development of ingenol disoxate as a convenient and efficacious treatment modality of non-melanoma skin cancers.

Funding

LEO Pharma A/S.

Electronic supplementary material

The online version of this article (doi:10.1007/s13555-016-0137-2) contains supplementary material, which is available to authorized users.

The barrier function of organotypic non-melanoma skin cancer models

Non-melanoma skin cancer (NMSC) is the most frequent human cancer with continuously rising incidences worldwide. Herein, we investigated the molecular basis for the impaired skin barrier function of organotypic NMSC models. We unraveled disturbed epidermal differentiation by reflectance confocal microscopy and histopathological evaluation. While the presence of claudin-4 and occludin were distinctly reduced, zonula occludens protein-1 was more wide-spread, and claudin-1 was heterogeneously distributed within the NMSC models compared with normal reconstructed human skin. Moreover, the cancer altered stratum corneum lipid packing and profile with decreased cholesterol content, increased phospholipid amount, and altered ceramide subclasses. These alterations contributed to increased surface pH and to 1.5 to 2.6-fold enhanced caffeine permeability of the NMSC models. Three topical applications of ingenol mebutate gel (0.015%) caused abundant epidermal cell necrosis, decreased Ki-67 indices, and increased lactate dehydrogenase activity. Taken together, our study provides new biological insights into the microenvironment of organotypic NMSC models, improves the understanding of the disease model by revealing causes for impaired skin barrier function in NMSC models at the molecular level, and fosters human cell-based approaches in preclinical drug evaluation.

IL-1 Contributes to the Anti-Cancer Efficacy of Ingenol Mebutate

Ingenol mebutate is approved for the topical treatment of actinic keratoses and may ultimately also find utility in treating skin cancers. Here we show that relapse rates of subcutaneous B16 melanoma tumours treated topically with ingenol mebutate were not significantly different in C57BL/6 and Rag1^-/- mice, suggesting B and T cells do not play a major role in the anti-cancer efficacy of ingenol mebutate. Relapse rates were, however, significantly increased in MyD88^-/- mice and in C57BL/6 mice treated with the anti-IL-1 agent, anakinra. Ingenol mebutate treatment induces a pronounced infiltration of neutrophils, which have been shown to have anti-cancer activity in mice. Herein we provide evidence that IL-1 promotes neutrophil recruitment to the tumour, decreases apoptosis of infiltrating neutrophils and increases neutrophil tumour killing activity. These studies suggest IL-1, via its action on neutrophils, promotes the anti-cancer efficacy of ingenol mebutate, with ingenol mebutate treatment causing both IL-1β induction and IL-1α released from keratinocytes.

Efficacy and safety of follow-up field treatment of actinic keratosis with ingenol mebutate 0·015% gel: a randomized, controlled 12-month study

BACKGROUND

Ingenol mebutate (IngMeb) is a novel patient-applied topical field therapy for actinic keratosis.

OBJECTIVES

To demonstrate the efficacy and safety of follow-up IngMeb field treatment of actinic keratoses (AKs) present at 8 weeks after initial treatment or emerging in a previously cleared field.

METHODS

In this phase III, randomized, double-blind study in patients with 4-8 clinically visible AKs within a contiguous 25-cm(2) treatment area on the face or scalp, all patients were treated initially with IngMeb 0·015% gel for three consecutive days. If lesions were present in the field at 8 weeks, or emerged at weeks 26 or 44, patients were randomized (2 : 1) to follow-up IngMeb or vehicle gel for three consecutive days. The main outcome was complete clearance rates of AKs 8 weeks after randomization.

RESULTS

Of 450 patients who received initial treatment with IngMeb, 61·6% demonstrated complete clearance at 8 weeks. Patients with AKs present at 8 weeks or emerging at weeks 26 or 44 were randomized to IngMeb (n = 134) or vehicle (n = 69). IngMeb achieved a higher complete clearance rate than vehicle 8 weeks after randomization in AKs present at 8 weeks (46·7% vs. 18·4%; P < 0·01) and in emergent AKs (59·5% vs. 25·0%; P = 0·01). Based on those who completed 12 months of follow-up (n = 340), the overall 12-month clearance rate was estimated at 50·0%. Follow-up IngMeb treatment was well tolerated.

CONCLUSIONS

This study demonstrated the long-term benefit of IngMeb 0·015% gel for initial and follow-up therapy of AKs.

Safety and tolerability of ingenol mebutate in the treatment of actinic keratosis

INTRODUCTION

Ingenol mebutate is a topical therapeutic agent for the treatment of actinic keratosis (AK). It has a novel mode of action and has shown comparable efficacy to other topical field therapies. This article summarizes and provides perspective on the safety profile of ingenol mebutate from clinical studies of this agent.

AREAS COVERED

The unique mechanism of action of ingenol mebutate, the basis for a rapid clinical effect, is outlined. Safety and tolerability data, including mean composite local skin response (LSR) scores, type of LSR, and adverse events from a range of clinical studies both in healthy volunteers and patients with AK, are reviewed. The safety profile of ingenol mebutate is then compared with other agents used to treat AK lesions.

EXPERT OPINION

Ingenol mebutate has a dosing period of 2 - 3 days, which is short compared with other field therapies, and there is no evidence of systemic absorption. The fact that most of the LSRs observed are mild to moderate in intensity and transient, with a majority resolved within 2 weeks, makes for a favorable safety profile. Ingenol mebutate enhances the armamentarium available to the dermatologist for the treatment of AK.

Ingenol mebutate treatment in keloids

BACKGROUND

Ingenol-mebutate has been used for the treatment of actinic keratosis. It has been shown that ingenol-mebutate inhibits the growth of cancer cells or induces tumor cell death through pro-apoptotic effects. Keloids are benign skin tumours and are the effect of a deregulated wound-healing process in genetically predisposed patients. Increased cell proliferation, which accounts for the progressive and hypertrophic nature of keloids, correlates with the failure of apoptosis and plays a role in the process of pathological scarring. Keloid cells show a mutated p53 gene resulting in functionally inactive p53 protein which cannot control genomic integrity. They tend to escape from apoptosis which leads to keloid development by means of accumulation of continuously proliferating cells. Currently, the treatment of keloids remains a challenge for high recurrence rates. However, the design and the development of pro-apoptotic therapeutic strategies would be beneficial to keloids treatment.

CASE PRESENTATION

A 55-year-old caucasian woman presented recurrent keloids on a presternal scar. Standard surgical intervention was used to treat the scar. However, this was unsuccessful and a year later the patient sought treatment again, but only by alternative means as the patient refused further surgical intervention. Consequently, based on past research and experience, the authors attempted to treat these lesions with ingenol mebutate gel, due to the pro-apoptotic effects.

CONCLUSION

After 1 month, there was a clinical resolution of lesions, with a slightly squamous, post-inflammatory erythema. A cutaneous biopsy proved the absence of residual keloids and deregulated expression of molecular markers. The last follow-up of the patient, 1 year after treatment, showed that the patient was still free of keloids recurrence.

Effective cutaneous vaccination using an inactivated chikungunya virus vaccine delivered by Foroderm

Foroderm is a new cutaneous delivery technology that uses high-aspect ratio, cylindrical silica microparticles, that are massaged into the skin using a 3D-printed microtextured applicator, in order to deliver payloads across the epidermis. Herein we show that this technology is effective for delivery of a non-adjuvanted, inactivated, whole-virus chikungunya virus vaccine in mice, with minimal post-vaccination skin reactions. A single topical Foroderm-based vaccination induced T cell, Th1 cytokine and antibody responses, which provided complete protection against viraemia and disease after challenge with chikungunya virus. Foroderm vaccination was shown to deliver fluorescent, virus-sized beads across the epidermis, with beads subsequently detected in draining lymph nodes. Foroderm vaccination also stimulated the egress of MHC II(+) antigen presenting cells from the skin. Foroderm thus has potential as a simple, cheap, effective, generic, needle-free technology for topical delivery of vaccines.

Intra-lesional injection of the novel PKC activator EBC-46 rapidly ablates tumors in mouse models

Intra-lesional chemotherapy for treatment of cutaneous malignancies has been used for many decades, allowing higher local drug concentrations and less toxicity than systemic agents. Here we describe a novel diterpene ester, EBC-46, and provide preclinical data supporting its use as an intra-lesional treatment. A single injection of EBC-46 caused rapid inflammation and influx of blood, followed by eschar formation and rapid tumor ablation in a range of syngeneic and xenograft models. EBC-46 induced oxidative burst from purified human polymorphonuclear cells, which was prevented by the Protein Kinase C inhibitor bisindolylmaleimide-1. EBC-46 activated a more specific subset of PKC isoforms (PKC-βI, -βII, -α and -γ) compared to the structurally related phorbol 12-myristate 13-acetate (PMA). Although EBC-46 showed threefold less potency for inhibiting cell growth than PMA in vitro, it was more effective for cure of tumors in vivo. No viable tumor cells were evident four hours after injection by ex vivo culture. Pharmacokinetic profiles from treated mice indicated that EBC-46 was retained preferentially within the tumor, and resulted in significantly greater local responses (erythema, oedema) following intra-lesional injection compared with injection into normal skin. The efficacy of EBC-46 was reduced by co-injection with bisindolylmaleimide-1. Loss of vascular integrity following treatment was demonstrated by an increased permeability of endothelial cell monolayers in vitro and by CD31 immunostaining of treated tumors in vivo. Our results demonstrate that a single intra-lesional injection of EBC-46 causes PKC-dependent hemorrhagic necrosis, rapid tumor cell death and ultimate cure of solid tumors in pre-clinical models of cancer.

Detecting field cancerization using a hyperspectral imaging system

BACKGROUND

Field cancerization denotes subclinical abnormalities in a tissue chronically exposed to UV radiation. These abnormalities can be found surrounding the clinically visible actinic keratoses.

OBJECTIVES

The aim of this study was to test the feasibility of a hyperspectral imaging system in the detection of multiple clinical and subclinical AKs for early treatment of the affected areas.

MATERIALS AND METHODS

Altogether 52 clinical AKs in 12 patients were included in this study. In six patients digital photos were taken of the naive AKs, and again after methylaminolevulinate(MAL)-fluorescence diagnosis which was used to teach HIS to find subclinical lesions. After 2-3 days when the MAL had vanished, the hyperspectral images were taken. Biopsies were taken from clinical AKs, healthy-looking skin and several suspected subclinical AKs. In the other six patients digital and hyperspectral images were taken of the naive AKs followed by one biopsy per patient.

RESULTS

HIS detected all clinically visible 52 AKs and numerous subclinical lesions. The histopathology of the 33 biopsied lesions were concordant with the HIS results showing either AK (n = 28) or photodamage (n = 5). Of the 28 histopathologically confirmed AKs, 16 were subclinical. A specific diffuse reflectance spectrum of an AK and healthy skin was defined.

CONCLUSION

The hyperspectral imaging system offers a new, non-invasive method for early detection of field cancerization. Lasers Surg. Med. 45:410-417, 2013. © 2013 Wiley Periodicals, Inc.

Cutaneous field cancerization: clinical, histopathological and therapeutic aspects

The concept of "field cancerization" was first introduced by Slaughter in 1953 when studying the presence of histologically abnormal tissue surrounding oral squamous cell carcinoma. It was proposed to explain the development of multiple primary tumors and locally recurrent cancer. Organ systems in which field cancerization has been described since then are: head and neck (oral cavity, oropharynx, and larynx), lung, vulva, esophagus, cervix, breast, skin, colon, and bladder. Recent molecular studies support the carcinogenesis model in which the development of a field with genetically altered cells plays a central role. An important clinical implication is that fields often remain after the surgery for the primary tumor and may lead to new cancers, designated presently as "a second primary tumor" or "local recurrence," depending on the exact site and time interval. In conclusion, the development of an expanding pre-neoplastic field appears to be a critical step in epithelial carcinogenesis with important clinical consequences. Diagnosis and treatment of epithelial cancers should not only be focused on the tumor but also on the field from which it developed. The most important etiopathogenetic, clinical, histopathological and therapeutic aspects of field cancerization are reviewed in this article.

Recurrent in situ melanoma successfully treated with ingenol mebutate

Background

Treatment options for melanoma in situ (MIS) include imiquimod, radiation therapy, cryotherapy, excisional and Mohs surgery. Ingenol mebutate is a new topical treatment option recognized for actinic keratosis. Although in vitro effectiveness has been demonstrated on melanoma cell lines, its therapeutic potential for in vivo melanomas is unknown.

Case Report

In 2011, a 91-year-old woman presented a thick melanoma of her cheek. The lateral sections revealed persisting in situ melanoma, which were again excised. She presented for follow-up and a recurrent MIS was evidenced centered on the previous scar. She refused further surgery and ingenol mebutate (0.015% gel) was administered on three consecutive days. One month later, a complete clinical resolution was observed. Histology and immunohistology revealed no residual MIS.

Conclusion

In this patient, ingenol mebutate was successful and well-tolerated as a topical, alternative therapy for MIS after failure of other treatment options.

Electronic supplementary material

The online version of this article (doi:10.1007/s13555-014-0051-4) contains supplementary material, which is available to authorized users.

Natural product and natural product derived drugs in clinical trials

The 25 Natural Product (NP)-derived drugs launched since 2008 and the 100 NP-derived compounds and 33 Antibody Drug Conjugates (ADCs) in clinical trials or in registration at the end of 2013 are reviewed.

Ingenol mebutate gel 0.015% and 0.05%: in actinic keratosis

Ingenol mebutate is the main active constituent of sap from the plant Euphorbia peplus, which has traditionally been used as a home remedy for various skin conditions. Ingenol mebutate gel is approved in the US, EU, Australia and Brazil for the topical treatment of actinic keratosis. A short course of field-directed therapy with topical ingenol mebutate gel was effective in the treatment of actinic keratoses on the face or scalp (ingenol mebutate gel 0.015% once daily for 3 consecutive days) and on the trunk or extremities (ingenol mebutate gel 0.05% once daily for 2 consecutive days), according to the results of four randomized, double-blind, vehicle-controlled, multicentre studies. Significantly higher complete clearance rates (primary endpoint) and partial clearance rates were seen at day 57 in patients receiving ingenol mebutate gel than in those receiving vehicle gel. Treatment with ingenol mebutate gel was generally associated with sustained clearance of actinic keratoses in the longer term. Topical ingenol mebutate gel was generally well tolerated in the treatment of patients with actinic keratoses on the face or scalp and on the trunk or extremities. Application-site conditions were the most commonly occurring adverse events.

Ingenol Mebutate: A Promising Treatment for Actinic Keratoses and Nonmelanoma Skin Cancers

Background:

A new treatment for actinic keratoses, ingenol mebutate, was recently approved by the US Food and Drug Administration.

Objective:

To review the mechanisms of action, efficacy and safety data, and practical recommendations for ingenol mebutate.

Methods:

The PubMed and clinicaltrials.gov databases were searched in March/April 2012 using the terms PEP005, ingenol mebutate, and ingenol 3-angelate. The abstracts from the Annual Scientific Meeting of the Australian College of Dermatologists (2009–2011) and the Annual Meeting of the American Academy of Dermatology (2009–2012) were also searched.

Results:

Due to its multiple mechanisms of action, ingenol mebutate treatment resulted in short- and long-term efficacy similar to other topical treatments for actinic keratoses in a shorter period of 2 or 3 days. This short therapy would reduce the duration of adverse events. Premarketing trials for treatment of nonmelanoma skin cancers also showed promising results for ingenol mebutate.

Conclusion:

Ingenol mebutate is a convenient, safe, and effective intervention for precancerous and cancerous skin conditions.

[What's new in dermatological therapy?]

Therapeutics is our daily tool to advance patient care. Although some may perceive a certain stagnation, the goal of this review was to choose among the hundreds of articles published between January and September 2012 those that seemed to contribute the greatest innovation. It is certainly valuable to observe that all include antibodies, cytokines, or conversely chemokine inhibitors, small regulatory molecules or even cells. This diversity illustrates the vitality of the research in dermatology, which covers fields from inflammatory and autoimmune diseases to vascular and infectious diseases. Beyond these established data, many of the results open useful and original leads for future research.

Tracking cells in their native habitat: lineage tracing in epithelial neoplasia

For tumours to develop, mutations must disrupt tissue homeostasis in favour of deregulated proliferation. Genetic lineage tracing has uncovered the behaviour of proliferating cells that underpins the maintenance of epithelial tissues and the barriers that are broken in neoplastic transformation. In this Review, we focus on new insights revealed by quantifying the behaviour of normal, preneoplastic and tumour cells in epithelia in transgenic mice and consider their potential importance in humans.

Clinical findings using ingenol mebutate gel to treat actinic keratoses

Actinic keratosis (AK) is a common ultraviolet light-induced skin lesion found on sun-exposed skin areas generally in older, fair-skinned people. It is part of a disease continuum observed in photodamaged skin that may lead to invasive squamous cell carcinoma. The presence of AK is associated with an increased risk of all skin cancers, as it is visible evidence of the carcinogenic effects of cumulative ultraviolet exposure. AKs are treated with lesion- and field-directed methods. Field-directed methods treat both the visible and subclinical lesions present in photodamaged skin, but treatment regimens are often lengthy and associated with poor tolerability because of vigorous local inflammatory reactions. Ingenol mebutate gel was recently approved by the Food and Drug Administration for topical treatment of AK. It induces cell death preferentially in transformed keratinocytes and promotes an inflammatory response that kills remaining tumor cells. In human studies, ingenol mebutate achieved high clearance rates of AK on the trunk or extremities and face or scalp after once-daily application for 2 or 3 consecutive daily treatments, when measured by complete or partial clearance of lesions. The localized inflammatory skin responses were generally mild to moderate and resolved in approximately 2 weeks on the face or scalp and 4 weeks on the trunk or extremities.

Malignant epithelial tumors: Part II. Therapy and prevention

A multitude of surgical and non-surgical therapies are available to treat malignant epithelial tumors of the skin. The article summarizes the current treatment options for basal cell carcinoma, squamous cell carcinoma and keratoacanthoma. Moreover, the possibilities of primary and secondary prevention for high-risk patients are reviewed. The decision about the best therapeutic option depends on location, age, and general health of the patient as well as the risk of tumor recurrence.

Preventative topical diclofenac treatment differentially decreases tumor burden in male and female Skh-1 mice in a model of UVB-induced cutaneous squamous cell carcinoma

Ultraviolet B (UVB) light is the major environmental carcinogen contributing to non-melanoma skin cancer (NMSC) development. There are over 3.5 million NMSC diagnoses in two million patients annually, with men having a 3-fold greater incidence of squamous cell carcinoma (SCC) compared with women. Chronic inflammation has been linked to tumorigenesis, with a key role for the cyclooxygenase-2 (COX-2) enzyme. Diclofenac, a COX-2 inhibitor and non-steroidal anti-inflammatory drug, currently is prescribed to patients as a short-term therapeutic agent to induce SCC precursor lesion regression. However, its efficacy as a preventative agent in patients without evidence of precursor lesions but with significant UVB-induced cutaneous damage has not been explored. We previously demonstrated in a murine model of UVB-induced skin carcinogenesis that when exposed to equivalent UVB doses, male mice had lower levels of inflammation but developed increased tumor multiplicity, burden and grade compared with female mice. Because of the discrepancy in the degree of inflammation between male and female skin, we sought to determine if topical treatment of previously damaged skin with an anti-inflammatory COX-2 inhibitor would decrease tumor burden and if it would be equally effective in the sexes. Our results demonstrated that despite observed sex differences in the inflammatory response, prolonged topical diclofenac treatment of chronically UVB-damaged skin effectively reduced tumor multiplicity in both sexes. Unexpectedly, tumor burden was significantly decreased only in male mice. Our data suggest a new therapeutic use for currently available topical diclofenac as a preventative intervention for patients predisposed to cutaneous SCC development before lesions appear.

New developments in the treatment of actinic keratosis: focus on ingenol mebutate gel

Actinic keratosis is a common disease in older, fair-skinned people, and is a consequence of cumulative ultraviolet exposure. It is part of a disease continuum in photodamaged skin that may lead to invasive squamous cell carcinoma. Treatment options frequently used include cryosurgery and topical pharmacologic agents, which are examples of lesion-directed and field-directed strategies. Ingenol mebutate gel was recently approved by the US Food and Drug Administration for topical treatment of actinic keratosis. While the mechanism of action of ingenol mebutate is not fully understood, in vitro and in vivo studies using tumor models indicate it has multiple mechanisms. Ingenol mebutate directly induces cell death by mitochondrial swelling and loss of cell membrane integrity preferentially in transformed keratinocytes. It promotes an inflammatory response characterized by infiltration of neutrophils and other immunocompetent cells that kills remaining tumor cells. The ability of ingenol mebutate to eliminate mutant p53 patches in ultraviolet-irradiated mouse skin suggests that it may have the potential to treat chronically ultraviolet-damaged skin. In human studies, ingenol mebutate achieved high clearance of actinic keratosis on the head and body after 2–3 consecutive daily treatments when measured by complete or partial clearance of lesions. Localized inflammatory skin responses were generally mild to moderate and resolved in less than a month.

Effective treatment of squamous cell carcinomas with ingenol mebutate gel in immunologically intact SKH1 mice

Ingenol mebutate has recently been approved by the Federal Drug Administration (USA) as a topical treatment for actinic keratoses. Herein, we describe the efficacy of ingenol mebutate for the topical treatment of squamous cell carcinoma (SCC) using a wild-type mouse model (SKH1) and the UV-induced mouse SCC cell line, T7. Daily treatment for 2 days with 0.25 % ingenol mebutate gel produced a cure rate of 70 %, with 0 % for placebo gel. Electron microscopy revealed swelling of cancer cell mitochondria within 1 h, with disruption of the inner mitochondrial membranes evident at 6 h post treatment. Primary necrosis of cancer cells was clearly evident by 24 h. Treatment was associated with local haemorrhage and a prodigious neutrophil infiltrate, with anti-T7 antibodies also detected. This is the first report of the successful treatment of SCC tumours with ingenol mebutate gel in wild-type mice, and supports the view that ingenol mebutate induces primary necrosis and activates the immune system.

A preliminary study of the safety of red light phototherapy of tissues harboring cancer

OBJECTIVE

Red light phototherapy is known to stimulate cell proliferation in wound healing. This study investigated whether low-level light therapy (LLLT) would promote tumor growth when pre-existing malignancy is present.

BACKGROUND DATA

LLLT has been increasingly used for numerous conditions, but its use in cancer patients, including the treatment of lymphedema or various unrelated comorbidities, has been withheld by practitioners because of the fear that LLLT might result in initiation or promotion of metastatic lesions or new primary tumors. There has been little scientific study of oncologic outcomes after use of LLLT in cancer patients.

METHODS

A standard SKH mouse nonmelanoma UV-induced skin cancer model was used after visible squamous cell carcinomas were present, to study the effects of LLLT on tumor growth. The red light group (n=8) received automated full body 670 nm LLLT delivered twice a day at 5 J/cm(2) using an LED source. The control group (n=8) was handled similarly, but did not receive LLLT. Measurements on 330 tumors were conducted for 37 consecutive days, while the animals received daily LLLT.

RESULTS

Daily tumor measurements demonstrated no measurable effect of LLLT on tumor growth.

CONCLUSIONS

This experiment suggests that LLLT at these parameters may be safe even when malignant lesions are present. Further studies on the effects of photoirradiation on neoplasms are warranted.

The role of ingenol mebutate in the treatment of actinic keratoses

Actinic keratoses (AK) are the most common premalignant pathology seen in dermatological practice and represent a burgeoning burden upon health services. Increasingly recognized is the damage to surrounding, perilesional skin, forming the premise for field-directed therapy. Ingenol mebutate gel is a novel agent for field-directed treatment of AK, requiring only 2 or 3 days of application. Following an overview of existing treatment modalities, the authors review recent trials and safety data pertaining to the use of ingenol mebutate gel and discuss its role in the treatment of AK.