Advances in the understanding of malignant transformation of keratinocytes: an immunohistochemical study

Pharmacological Agents Used in the Prevention and Treatment of Actinic Keratosis: A Review

Actinic keratosis (AK) is among the most commonly diagnosed skin diseases with potentially life-threatening repercussions if left untreated. Usage of pharmacologic agents represents one of many therapeutic strategies that can be used to help manage these lesions. Ongoing research into these compounds continues to change our clinical understanding as to which agents most benefit particular patient populations. Indeed, factors such as past personal medical history, lesion location and tolerability of therapy only represent a few considerations that clinicians must account for when prescribing appropriate treatment. This review focuses on specific drugs used in either the prevention or treatment of AKs. Nicotinamide, acitretin and topical 5-fluorouracil (5-FU) continue to be used with fidelity in the chemoprevention of actinic keratosis, although some uncertainty persists in regard to which agents should be used in immunocompetent vs. immunodeficient/immunosuppressed patients. Topical 5-FU, including combination formulations with either calcipotriol or salicylic acid, as well as imiquimod, diclofenac and photodynamic light therapy are all accepted treatment strategies employed to target and eliminate AKs. Five percent of 5-FU is regarded as the most effective therapy in the condition, although the literature has conflictingly shown that lower concentrations of the drug might also be as effective. Topical diclofenac (3%) appears to be less efficacious than 5% 5-FU, 3.75-5% imiquimod and photodynamic light therapy despite its favorable side effect profile. Finally, traditional photodynamic light therapy, while painful, appears to be of higher efficacy in comparison to its more tolerable counterpart, daylight phototherapy.

Antibody gene transfer treatment drastically improves epidermal pathology in a keratitis ichthyosis deafness syndrome model using male mice

BACKGROUND

Keratitis ichthyosis deafness (KID) syndrome is a rare disorder caused by hemichannel (HC) activating gain-of-function mutations in the GJB2 gene encoding connexin (Cx) 26, for which there is no cure, or current treatments based upon the mechanism of disease causation.

METHODS

We applied Adeno Associated Virus (AAV) mediated mAb gene transfer (AAVmAb) to treat the epidermal features of KID syndrome with a well-characterized HC blocking antibody using male mice of a murine model that replicates the skin pathology of the human disease.

FINDINGS

We demonstrate that in vivo AAVmAb treatment significantly reduced the size and thickness of KID lesions, in addition to blocking activity of mutant HCs in the epidermis in vivo. We also show that AAVmAb treatment eliminated abnormal keratinocyte proliferation and enlarged cell size, decreased apoptosis, and restored the normal distribution of keratin expression.

INTERPRETATION

Our findings reinforce the critical role played by increased HC activity in the skin pathology associated with KID syndrome. They also underscore the clinical potential of anti-HC mAbs coupled with genetic based delivery systems for treating the underlying mechanistic basis of this disorder. Inhibition of HC activity is an ideal therapeutic target in KID syndrome, and the genetic delivery of mAbs targeted against mutant HCs could form the basis of new therapeutic interventions to treat this incurable disease.

FUNDING

Fondazione Telethon grant GGP19148 and University of Padova grant Prot. BIRD187130 to FM; Foundation for Ichthyosis and Related Skin Types (FIRST) and National Institutes of Health grant EY 026911 to TWW.

Prognostic Significance of RAS Mutations and P53 Expression in Cutaneous Squamous Cell Carcinomas

TP53 is considered the most commonly-altered gene in cutaneous squamous cell carcinoma (cSCC). Conversely, RAS mutations have been reported in a low percentage of cSCC. The objective of our study was to evaluate the frequency of p53 expression and RAS mutations in cSCC and correlate them with clinicopathological features and patient outcome. We performed immunohistochemistry for p53 and genetic profiling for RAS mutations in a retrospective series of cSCC. The predictive value of p53 expression, RAS mutations, and clinicopathological parameters was assessed using logistic regression models. The overall frequency of RAS mutations was 9.3% (15/162), and 82.1% of the cases (133/162) had p53 overexpression. RAS mutations rate was 3.2% (1/31) of in situ cSCCs and 10.7% (14/131) of invasive cSCCs. RAS mutations were more frequently associated with an infiltrative than an expansive pattern of invasion (p = 0.046). p53 overexpression was a predictor of recurrence in the univariate analysis. Our results indicate that RAS mutations associate with features of local aggressiveness. Larger studies with more recurrent and metastatic cSCCs are necessary to further address the prognostic significance of p53 overexpression in patients’ risk stratification.

A potent antagonist antibody targeting connexin hemichannels alleviates Clouston syndrome symptoms in mutant mice

BACKGROUND

Numerous currently incurable human diseases have been causally linked to mutations in connexin (Cx) genes. In several instances, pathological mutations generate abnormally active Cx hemichannels, referred to also as "leaky" hemichannels. The goal of this study was to assay the in vivo efficacy of a potent antagonist antibody targeting Cx hemichannels.

METHODS

We employed the antibody to treat Cx30A88V/A88V adult mutant mice, the only available animal model of Clouston syndrome, a rare orphan disease caused by Cx30 p.A88V leaky hemichannels. To gain mechanistic insight into antibody action, we also performed patch clamp recordings, Ca2+ imaging and ATP release assay in vitro.

FINDINGS

Two weeks of antibody treatment sufficed to repress cell hyperproliferation in skin and reduce hypertrophic sebaceous glands (SGs) to wild type (wt) levels. These effects were obtained whether mutant mice were treated topically, by application of an antibody cream formulation, or systemically, by intraperitoneal antibody injection. Experiments with mouse primary keratinocytes and HaCaT cells revealed the antibody blocked Ca2+ influx and diminished ATP release through leaky Cx30 p.A88V hemichannels.

INTERPRETATION

Our results show anti-Cx antibody treatment was effective in vivo and sufficient to counteract the effects of pathological connexin expression in Cx30A88V/A88V mice. In vitro experiments suggest antibodies gained control over leaky hemichannels and contributed to restoring epidermal homeostasis. Therefore, regulating cell physiology by antibodies targeting the extracellular domain of Cxs may enforce an entirely new therapeutic strategy. These findings support the further development of antibodies as drugs to address unmet medical needs for Cx-related diseases. FUND: Fondazione Telethon, GGP19148; University of Padova, SID/BIRD187130; Consiglio Nazionale delle Ricerche, DSB.AD008.370.003\TERABIO-IBCN; National Science Foundation of China, 31770776; Science and Technology Commission of Shanghai Municipality, 16DZ1910200.

Density of Langerhans Cells in Nonmelanoma Skin Cancers: A Systematic Review

Langerhans cells (LCs) are bone marrow-derived dendritic cells (DCs) that represent 2-3% of the entire cell population of the human skin, known to have an ability to present antigens to T lymphocytes. Moreover, there is evidence that LCs are probably capable of inducing the local cytotoxic type T-cell-mediated response against the tumour-associated antigens. In the past two decades, a dramatic increase has been noted in the incidence of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). The purpose of this study was to critically assess the results of available studies quantitatively assessing the LCs in nonmelanoma skin cancers and try to establish a conclusion of its possible impact on their future treatment. The PubMed, EMBASE, and the Web of Science databases were searched, which returned 948 citations. After a thorough analysis of full article texts, 30 studies have been chosen, including 11 of the BCC, 12 of the SCC specimens, and 7 analysing both tumour types. There was an overall trend towards slightly higher numbers of LCs in BCC than in SCC; however, these tendencies were discrepant between the studies. We presume that such differences could be caused by various staining techniques with a broad spectrum of specificity, including anti-S100, anti-CD1a, and ATPase activity staining used for LCs identification. We hypothesise that as there is a high inconsistency between the results of the studies, as far as the densities of LCs observed in the specimens are concerned, it seems that the mechanism of the influence of LCs on the antitumoural immune response is complicated. Finally, as at present, there is a paucity of available risk scores for the recurrence or progression of BCC or SCC, the creation of classification stratifying that risk including the density of LCs could bring additional information both for the physician and the patient.

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.

Morphologic grading and treatment of facial actinic keratosis

Actinic keratoses (AKs) represent the earliest stage in the development of squamous cell carcinoma (SCC) and represent important biomarkers for individuals at risk for development of invasive SCC. Based on clinical morphology, AK can be subdivided into three different grades, which correspond to specific dermatoscopic, reflectance confocal microscopic, and histopathologic substrates. Given the risk for potential progression toward invasive SCC, AK should be treated at the earliest stage. A wide range of minimal destructive or topical therapies is available for the treatment of AK. The choice of treatment depends on the number, size, clinical grading, duration, and location of lesions, patient's compliance, general health conditions, and cosmetic outcome. Treatment can be divided into lesion-directed and field-directed therapies. Lesion-directed treatment focuses on the treatment of single lesions, whereas field-directed treatment aims to eliminate both clinically visible and subclinical lesions within the field of actinic damage (concept of field cancerization). Noninvasive techniques such as dermoscopy and reflectance confocal microscopy can be helpful in identifying AK potentially progressing toward SCC, as well as in the selection of the adequate treatment and monitoring of the treatment outcome.

Triterpenes promote keratinocyte differentiation in vitro, ex vivo and in vivo: a role for the transient receptor potential canonical (subtype) 6

It has been shown recently that triterpenes inhibit cancer cell growth of various cell types in vitro. In this work, the effect of highly purified triterpenes (TE) with betulin as the major compound (>80% w/w) on cell proliferation, apoptosis, and differentiation of human keratinocytes was analyzed in vitro, ex vivo, and in vivo. In vitro, TE increased calcium influx into primary keratinocytes and upregulated various differentiation markers including keratin 10. TE also specifically increased the expression of the non-selective transient receptor potential canonical (subtype) 6 (TRPC6) in keratinocytes, and knocking down TRPC6 inhibited keratin 10 upregulation. Ex vivo, in human skin explants TE induced the expression of TRPC6 in the epidermis and increased DNA fragmentation of terminally differentiating keratinocytes. Topical treatment with TE of actinic keratoses, that represent in situ squamous cell carcinomas with disturbed epithelial differentiation, resulted in downgrading of aberrant Ki67 expression and upregulation of keratin 10 in vivo. Our data indicate that TE promotes keratinocyte differentiation in vitro and in vivo. This effect seems to be mediated at least in part by TRPC6.

Purinergic receptors are part of a signalling system for proliferation and differentiation in distinct cell lineages in human anagen hair follicles

We investigated the expression of P2X(5), P2X(7), P2Y(1) and P2Y(2) receptor subtypes in adult human anagen hair follicles and in relation to markers of proliferation [proliferating cell nuclear antigen (PCNA) and Ki-67], keratinocyte differentiation (involucrin) and apoptosis (anticaspase-3). Using immunohistochemistry, we showed that P2X(5), P2Y(1) and P2Y(2) receptors were expressed in spatially distinct zones of the anagen hair follicle: P2Y(1) receptors in the outer root sheath and bulb, P2X(5) receptors in the inner and outer root sheaths and medulla and P2Y(2) receptors in living cells at the edge of the cortex/medulla. P2X(7) receptors were not expressed. Colocalisation experiments suggested different functional roles for these receptors: P2Y(1) receptors were associated with bulb and outer root sheath keratinocyte proliferation, P2X(5) receptors were associated with differentiation of cells of the medulla and inner root sheaths and P2Y(2) receptors were associated with early differentiated cells in the cortex/medulla that contribute to the formation of the hair shaft. The therapeutic potential of purinergic agonists and antagonists for controlling hair growth is discussed.

Vehicle-controlled, randomized, double-blind study to assess safety and efficacy of imiquimod 5% cream applied once daily 3 days per week in one or two courses of treatment of actinic keratoses on the head

BACKGROUND

Imiquimod has been investigated as a safe and effective therapeutic option for the treatment of actinic keratosis (AK).

OBJECTIVES

To evaluate imiquimod vs. vehicle applied three times a week for 4 weeks in one or two courses of treatment for AK on the face or balding scalp.

PATIENTS AND METHODS

Patients diagnosed with AK were enrolled in this multicentre, vehicle-controlled, double-blind study conducted in Europe. Twenty study centres enrolled a total of 259 patients in this study. Patients applied the study drug for 4 weeks, entered a 4-week rest period and if they did not have complete clearance, they then entered a second course of treatment.

RESULTS

Patients in the imiquimod group had an overall complete clearance rate of 55.0% (71/129) vs. a rate of 2.3% (3/130) for the vehicle group. There was a high rate of agreement between the clinical assessment and histological findings with respect to AK lesion clearance. At both 8-week post-treatment visits, the negative predictive value of the investigator assessment was 92.2% for clinical assessments vs. histological results.

CONCLUSIONS

A 4-week course of treatment with three times weekly dosing of imiquimod 5% cream, with a repeated course of treatment for those patients who fail to clear after the first course of treatment, is a safe and effective treatment for AK. The overall complete clearance rate (complete clearance after either course 1 or course 2) is comparable to the 16-week treatment regimen, while decreasing drug exposure to the patient and decreasing the overall treatment time.

Imiquimod-induced regression of actinic keratosis is associated with infiltration by T lymphocytes and dendritic cells: a randomized controlled trial

BACKGROUND

Imiquimod 5% cream is a topically applied immune response modifier that has been shown to give effective treatment of actinic keratosis (AK). The therapeutic effects of imiquimod are likely to involve the provocation of a cutaneous immune response against abnormal cells, an assumption based on a strong correlation between complete clearance rates and the severity of the local skin reactions (erythema, oedema, erosion/ulceration, weeping/exudation and scabbing/crusting); however, no clinical studies have conclusively proved this mechanism.

OBJECTIVES

To determine the nature of cellular infiltrates induced by the application of imiquimod to AK lesions and to study cells involved in the cutaneous immune response.

METHODS

Eighteen patients participated in this phase I, randomized, double-blind, parallel group, vehicle-controlled study. Enrolled patients were randomized in a 2 : 1 ratio to receive imiquimod cream or vehicle cream and applied study cream to five lesions on the scalp, forearm or upper trunk once daily, three days per week for up to 16 weeks. Each patient had punch biopsies of two distinct AK lesions: a lesion was biopsied before treatment to obtain baseline biomarker levels, and a different lesion was biopsied after 2 weeks of treatment. Biopsy specimens were examined using routine and immunohistochemical staining.

RESULTS

The imiquimod group showed statistically significant increases from baseline to week 2 in tissue biomarker levels for CD3, CD4, CD8, CD11c, CD86/CD11c, CD68, HLA-DR and TUNEL. No significant differences were seen for the vehicle group. Complete clearance of all treated AK lesions was achieved in five of 11 (45%) imiquimod patients and in none of six vehicle patients.

CONCLUSIONS

Imiquimod stimulates a cutaneous immune response characterized by increases in activated dendritic cells and CD4+ and CD8+ T cells.

Nuclear Morphometry and Molecular Biomarkers of Actinic Keratosis, Sun-Damaged, and Nonexposed Skin

Computer-assisted image analysis is useful for quantifying the histologic and molecular changes of sun-induced squamous cell carcinoma progression. We used the CAS 200 image analysis system to measure nuclear morphometric parameters, p53 expression, and proliferation markers in actinic keratosis (AK), sun-exposed, and normal skin in 51 patients. Nuclear morphometry revealed significant increases in nuclear absorbance, irregularity of nuclear shape, and nuclear size in AK compared with normal and sun-damaged skin. These parameters showed significantly greater variability in AK nuclei. Argyrophyllic nucleolar organizer area and number were also significantly greater in AK compared with sun-damaged skin and normal skin. Ki67 and p53 expressions were both increased in sun-damaged skin relative to normal and greater still in AK. These data are evidence that sun damage induces proliferation and p53 abnormalities before the appearance of nuclear abnormalities and their associated DNA instability. Following these changes during a skin cancer chemopreventative trial can then help assess the efficacy of the agent and help determine where in the progression of neoplastic changes it exerts its biological effects.

Imiquimod 5% cream for the treatment of actinic keratosis: Results from a phase III, randomized, double-blind, vehicle-controlled, clinical trial with histology

BACKGROUND

Increasing evidence suggests imiquimod may be a safe therapeutic option for the treatment of actinic keratosis (AK). The diagnosis and assessment of most AK lesions is made clinically, without histologic confirmation.

OBJECTIVE

A phase III, randomized, double-blind, parallel group, vehicle-controlled study evaluated the efficacy of imiquimod 5% cream compared with vehicle in the treatment of AK lesions on the face and balding scalp including pretreatment and posttreatment biopsy specimens.

METHODS

A total of 286 patients at 18 centers in 6 European countries with histologically confirmed AK were randomized to either imiquimod 5% cream or vehicle cream. Study cream was applied once per day, 3 days per week, for 16 weeks. Clearance of AK lesions was clinically and histologically assessed at an 8-week posttreatment visit.

RESULTS

The complete clearance rate for the imiquimod group was 57.1% versus 2.2% for the vehicle group (P <.001). The partial clearance rate (> or =75% reduction in baseline lesions) for the imiquimod group was 72.1% versus 4.3% for the vehicle group (P <.001). The most common side effects were erythema, scabbing/crusting, and erosions/ulceration. For the imiquimod group the incidence of severe erythema, scabbing/crusting, or erosions/ulceration was 30.6%, 29.9%, and 10.2%, respectively.

CONCLUSION

Imiquimod 5% cream used 3 times per week for 16 weeks is an effective treatment for AK. Clinical clearance was established by both clinical observation and histologic analysis.

Imiquimod 5% cream for the treatment of actinic keratosis: results from two phase III, randomized, double-blind, parallel group, vehicle-controlled trials

BACKGROUND

The immune system plays a critical role in the development and pathogenesis of actinic keratosis (AK). Imiquimod has been shown to stimulate the cutaneous immune response and be effective for the treatment of nonmelanoma skin cancers.

OBJECTIVE

Two phase III, randomized, double-blind, vehicle-controlled studies evaluated the efficacy of imiquimod 5% cream compared with vehicle in the treatment of AK lesions on the face and balding scalp.

METHODS

A total of 436 participants at 24 centers in the United States and Canada were randomized to either imiquimod 5% or vehicle cream. Study cream was applied one time per day, 2 days per week for 16 weeks. Clearance of AK lesions was clinically assessed at an 8-week posttreatment visit.

RESULTS

The complete clearance rate was 45.1% for the imiquimod group and 3.2% for the vehicle group. The difference in complete clearance rates (imiquimod minus vehicle) was 41.9% with a 95% confidence interval of 34.9% to 49%. The partial (> or =75%) clearance rate was 59.1% for the imiquimod group and 11.8% for the vehicle group. The difference in partial clearance rates (imiquimod minus vehicle) was 47.3% with a 95% confidence interval of 39.5% to 55.1%. The median percent reduction in AK lesions was 83.3% for the imiquimod group and 0% for the vehicle group. Local skin reactions were common. Severe erythema was reported by 17.7% of participants who received imiquimod and 2.3% of participants who received vehicle. Overall, imiquimod was very well tolerated.

CONCLUSION

Imiquimod 5% cream used 2 times per week for 16 weeks is an effective and well-tolerated treatment for AK.

Management of actinic keratoses

Actinic keratoses are quite common. Since they represent the initial stage in the evolution of squamous cell carcinoma, recognition and treatment are important. Recently, new treatment modalities have become available including immune modulators, photodynamic therapy, and topical nonsteroidal anti-inflammatory agents.

Purinergic Receptors Are Part of a Signaling System for Keratinocyte Proliferation, Differentiation, and Apoptosis in Human Fetal Epidermis

We have investigated the expression of P2X5, P2X7, P2Y1, and P2Y2 receptor subtypes in 8- to 11-wk-old human fetal epidermis in relation to markers of proliferation (proliferating cell nuclear antigen (PCNA) and Ki-67), keratinocyte differentiation (cytokeratin K10 and involucrin), and markers of apoptosis (TdT-mediated dUTP nick end labeling (TUNEL) and anti-caspase-3). Immunohistochemistry showed that each of the four receptors was expressed in spatially distinct zones of the developing epidermis: P2Y1 receptors were found in the basal layer, P2X5 receptors were predominantly in the basal and intermediate layers, and both P2Y2 and P2X7 receptors were in the periderm. Colocalization experiments suggested different functional roles for these receptors. P2Y1 receptors were found in fetal keratinocytes positive for PCNA and Ki-67, suggesting a role in proliferation. P2X5 receptors double labeled with differentiated fetal keratinocytes that were positive for cytokeratin K10, suggesting a role in differentiation. P2X7 receptors colocalized with anti-caspase-3 antibody and were also expressed in periderm cells positive for TUNEL, suggesting a role in periderm cell apoptosis. P2Y2 receptors were found only in periderm cells and may have a role in chloride and fluid secretion into the amniotic fluid.

Expression of p53, bcl-2 and growth hormone receptor in actinic keratosis, hypertrophic type

According to novel investigations, actinic keratosis (AK) is not a premalignant lesion but is a malignant lesion in the evolution to invasive squamous cell carcinoma (SCC). Thus, we analyzed p53, bcl-2 and growth hormone receptor (GHR) expression in hypertrophic-type AK (HAK) to determine the relative importance of these protooncogenes in the biological behavior of HAK. Expression of p53, bcl-2 and GHR was determined by immunohistochemistry in 33 HAK specimens and surrounding perilesional normal skin (PNS). The relative proportions of immunoreactive cells were determined. Of the 33 HAK specimens, 30 (91%) showed immunopositive staining for p53, 33 (100%) for bcl-2, and 12 (36%) for GHR. Highly positive p53 expression in HAK lesions could indicate that p53 mutation is an early and crucial event in lesion development. The detected pattern of the p53/ bcl-2 ratio in HAK suggests an important role for another gene: the proapoptotic gene bax. Our findings indicate that GHR expression could be a biological marker of progression of HAK to SCC.