Histamine H4 receptor knockout mice display reduced inflammation in a chronic model of atopic dermatitis

BACKGROUND

The histamine H4 receptor (H4R) was brought into focus as a new therapeutic target for the treatment of allergic disorders such as atopic dermatitis (AD). H4R antagonists have already been tested in several animal models of AD, but these studies have yielded conflicting results.

MATERIAL AND METHODS

The development of ovalbumin-induced AD-like skin lesions was analysed in H4R(-/-) mice and in H4R antagonist (JNJ28307474)-treated mice.

RESULTS

H4R(-/-) mice showed a clear amelioration of the skin lesions, with a diminished influx of inflammatory cells and a reduced epidermal hyperproliferation at lesional skin sites. H4R(-/-) mice had a reduced amount of ovalbumin-specific IgE, a reduced number of splenocytes and lymph node cells with a decreased number of CD4+ T cells. The H4R modulated the cytokine secretion of CD4+ T cells and splenocytes and altered the cellular profile in the lymph nodes. The anti-inflammatory effect could only partially be mimicked by JNJ28307474 and only when the H4R antagonist was given during sensitization and challenge and not when JNJ28307474 was only given during the provocation phase of the allergic reaction.

CONCLUSION

The H4R modulates inflammation in a chronic allergic dermatitis setting. However, results of this study indicate that it is necessary to block the H4R during ontogeny and development of the allergic inflammation.

A randomized, controlled phase III trial of nab-Paclitaxel versus dacarbazine in chemotherapy-naïve patients with metastatic melanoma

BACKGROUND

The efficacy and safety of nab-paclitaxel versus dacarbazine in patients with metastatic melanoma was evaluated in a phase III randomized, controlled trial.

PATIENTS AND METHODS

Chemotherapy-naïve patients with stage IV melanoma received nab-paclitaxel 150 mg/m(2) on days 1, 8, and 15 every 4 weeks or dacarbazine 1000 mg/m(2) every 3 weeks. The primary end point was progression-free survival (PFS) by independent radiologic review; the secondary end point was overall survival (OS).

RESULTS

A total of 529 patients were randomized to nab-paclitaxel (n = 264) or dacarbazine (n = 265). Baseline characteristics were well balanced. The majority of patients were men (66%), had an Eastern Cooperative Oncology Group status of 0 (71%), and had M1c stage disease (65%). The median PFS (primary end point) was 4.8 months with nab-paclitaxel and 2.5 months with dacarbazine [hazard ratio (HR), 0.792; 95.1% confidence interval (CI) 0.631-0.992; P = 0.044]. The median OS was 12.6 months with nab-paclitaxel and 10.5 months with dacarbazine (HR, 0.897; 95.1% CI 0.738-1.089; P = 0.271). Independently assessed overall response rate was 15% versus 11% (P = 0.239), and disease control rate (DCR) was 39% versus 27% (P = 0.004) for nab-paclitaxel versus dacarbazine, respectively. The most common grade ≥3 treatment-related adverse events were neuropathy (nab-paclitaxel, 25% versus dacarbazine, 0%; P < 0.001), and neutropenia (nab-paclitaxel, 20% versus dacarbazine, 10%; P = 0.004). There was no correlation between secreted protein acidic and rich in cysteine (SPARC) status and PFS in either treatment arm.

CONCLUSIONS

nab-Paclitaxel significantly improved PFS and DCR compared with dacarbazine, with a manageable safety profile.

Radiosensitization by BRAF inhibitor therapy-mechanism and frequency of toxicity in melanoma patients

BACKGROUND

Recent evidence suggests that ionizing radiation may be associated with unexpected side-effects in melanoma patients treated with concomitant BRAF inhibitors. A large multicenter analysis was carried out to generate reliable safety data and elucidate the mechanism.

METHODS

A total of 161 melanoma patients from 11 European skin cancer centers were evaluated for acute and late toxicity, of whom 70 consecutive patients received 86 series of radiotherapy with concomitant BRAF inhibitor therapy. To further characterize and quantify a possible radiosensitization by BRAF inhibitors, blood samples of 35 melanoma patients were used for individual radiosensitivity testing by fluorescence in situ hybridization of chromosomal breaks after ex vivo irradiation.

RESULTS

With radiotherapy and concomitant BRAF inhibitor therapy the rate of acute radiodermatitis ≥2° was 36% and follicular cystic proliferation was seen in 13% of all radiotherapies. Non-skin toxicities included hearing disorders (4%) and dysphagia (2%). Following whole-brain radiotherapy, rates of radiodermatitis ≥2° were 44% and 8% (P < 0.001) for patients with and without BRAF inhibitor therapy, respectively. Concomitant treatment with vemurafenib induced acute radiodermatitis ≥2° more frequently than treatment with dabrafenib (40% versus 26%, P = 0.07). In line with these findings, analysis of chromosomal breaks ex vivo indicated significantly increased radiosensitivity for patients under vemurafenib (P = 0.004) and for patients switched from vemurafenib to dabrafenib (P = 0.002), but not for patients on dabrafenib only. No toxicities were reported after stereotactic treatment.

CONCLUSION

Radiotherapy with concomitant BRAF inhibitor therapy is feasible with an acceptable increase in toxicity. Vemurafenib is a more potent radiosensitizer than dabrafenib.

Lentivirus-induced 'Smart' dendritic cells: Pharmacodynamics and GMP-compliant production for immunotherapy against TRP2-positive melanoma

Monocyte-derived conventional dendritic cells (ConvDCs) loaded with melanoma antigens showed modest responses in clinical trials. Efficacy studies were hampered by difficulties in ConvDC manufacturing and low potency. Overcoming these issues, we demonstrated higher potency of lentiviral vector (LV)-programmed DCs. Monocytes were directly induced to self-differentiate into DCs (SmartDC-TRP2) upon transduction with a tricistronic LV encoding for cytokines (granulocyte macrophage colony stimulating factor (GM-CSF) and interleukin-4 (IL-4)) and a melanoma antigen (tyrosinase-related protein 2 (TRP2)). Here, SmartDC-TRP2 generated with monocytes from five advanced melanoma patients were tested in autologous DC:T cell stimulation assays, validating the activation of functional TRP2-specific cytotoxic T lymphocytes (CTLs) for all patients. We described methods compliant to good manufacturing practices (GMP) to produce LV and SmartDC-TRP2. Feasibility of monocyte transduction in a bag system and cryopreservation following a 24-h standard operating procedure were achieved. After thawing, 50% of the initial monocyte input was recovered and SmartDC-TRP2 self-differentiated in vitro, showing uniform expression of DC markers, detectable LV copies and a polyclonal LV integration pattern not biased to oncogenic loci. GMP-grade SmartDC-TRP2 expanded TRP2-specific autologous CTLs in vitro. These results demonstrated a simpler GMP-compliant method of manufacturing an effective individualized DC vaccine. Such DC vaccine, when in combination with checkpoint inhibition therapies, might provide higher specificity against melanoma.

[Cutaneous side effects of anti-tumor therapy with BRAF and MEK inhibitors]

BACKGROUND

BRAF and MEK inhibitors are new targeted therapies which are used in the treatment of malignancies, in particular of malignant melanoma.

SIDE EFFECTS

Cutaneous side effects are common during the treatment with both types of inhibitors. These side effects include inflammatory reactions such as maculopapular and papulopustular exanthema, hand-foot syndrome, panniculitis, paronychia, photo- and radio-sensitization. As a class effect, BRAF-inhibitors induce proliferative disorders of keratinocytes and melanocytes, such as palmoplantar hyperkeratosis (as part of the hand-foot syndrome), verruciform and acanthoma-like lesions, follicular and Grover disease-like hyperkeratoses, keratoacanthomas, squamous cell carcinomas and atypical melanocytic nevi with transition to secondary melanomas. Furthermore, hair alterations and xerosis are possible.

CONCLUSIONS

Treatment with BRAF and MEK inhibitors requires close dermatologic monitoring of the patient. This manuscript summarizes the most frequent cutaneous side effects and their management.

Profiling of histamine H4 receptor agonists in native human monocytes

BACKGROUND AND PURPOSE

Since the identification of the histamine H₄ receptor, several ligands activating this receptor have been described and more compounds are in development. These ligands are well characterized in pharmacological assays, including radioligand competition binding studies, GTPγS and GTPase assays. In most cases, these experiments are performed in transfected cell lines, expressing unnaturally high levels of target receptors and G-protein signalling components. In this study we investigated the specific properties of H₄ receptor ligands in native cells.

EXPERIMENTAL APPROACH

Histamine and five different H₄ receptor agonists - 4-methylhistamine, UR-PI376, clobenpropit, VUF8430 and ST-1006 - were characterized in freshly isolated human monocytes. The ligands (10 nM-10 μM) were tested as inhibitors of IL-12p70 secretion from human monocytes and the effects of the H₂ receptor antagonist ranitidine and the H₄ receptor antagonist JNJ7777120 on their action was investigated.

KEY RESULTS

Histamine and all the tested agonists reduced IL-12p70 secretion into monocyte supernatants by 40-70%. The potencies varied with pEC50 values ranging from 5.7 to 6.9, depending on the agonist used. All potencies were lower than those determined in the original investigations of the compounds. Pretreatment of monocytes with H₂ or H₄ receptor antagonists showed that some H₄ receptor ligands also had low activity at the H₂ receptor.

CONCLUSIONS AND IMPLICATIONS

Our study demonstrates discrepancies between the potencies obtained from assays in transfected cell lines and assays in native human cells, indicating the importance of evaluating H₄ receptor ligands in native cells.

Differential influence of vemurafenib and dabrafenib on patients' lymphocytes despite similar clinical efficacy in melanoma

BACKGROUND

Since the majority of melanomas eventually become resistant and progress, combining selective BRAF inhibitors (BRAFi) with immunotherapies has been proposed to achieve more durable treatment responses. Here, we explored the impact of selective BRAFi on the hosts' immune system.

PATIENTS AND METHODS

Clinical data, whole blood counts (WBC) and serum lactate dehydrogenase (LDH) of 277 vemurafenib- and 65 dabrafenib-treated melanoma patients were evaluated. The frequency and phenotype of lymphocyte subpopulations were determined by flow cytometry while T cell cytokine secretion was measured by multiplex assays.

RESULTS

Progression-free survival (PFS) as well as overall survival (OS) were similar in patients treated with either BRAFi. High pretreatment LDH was associated with shorter PFS and OS in both groups. During therapy, peripheral lymphocytes decreased by 24.3% (median, P < 0.0001) in vemurafenib-treated patients but remained unchanged in dabrafenib-treated patients (+1.2%, P = 0.717). Differentiation of peripheral lymphocytes of vemurafenib-treated patients showed a significant decrease in CD4(+) T cells (P < 0.05). Within CD4(+) T cells obtained during treatment, an increase in CCR7(+)CD45RA(+) (naïve) and a decrease in CCR7(+)CD45RA(-) (central memory) populations were found (P < 0.01 for both). Furthermore, secretion of interferon-γ and interleukin-9 by CD4(+) T cells was significantly lower in samples obtained during vemurafenib treatment compared with baseline samples.

CONCLUSION

While both compounds have comparable clinical efficacy, vemurafenib but not dabrafenib decreases patients peripheral lymphocyte counts and alters CD4(+) T cell phenotype and function. Thus, selective BRAFi can significantly affect patients' peripheral lymphocyte populations. Fully understanding these effects could be critical for successfully implementing combinatorial therapies of BRAFi with immunomodulatory agents.

Treatment of advanced cutaneous squamous cell carcinomas with epidermal growth factor receptor inhibitors

In advanced cutaneous squamous cell carcinoma (cSCC), efficient medical treatment options are limited in case surgery and radiotherapy failed, particularly since most patients are of higher age and suffer from comorbidities. In many tumor entities, the epidermal growth factor receptor (EGFR) has been established as an important therapeutic target, and blockade of EGFR signaling by monoclonal antibodies or small molecules achieves a therapeutic benefit. EGFR expression is also often dysregulated in cSCC. We report here two patients with advanced cSCC treated with the EGFR inhibitor cetuximab and summarize the current published experience with the use of EGFR inhibitors in cSCC.

[Squamous cell carcinoma developing in oral lichen planus]

Oral lichen planus is a mucosal inflammatory disease whose pathogenesis is unclear. The chronic inflammation leads to development of a squamous cell carcinoma in 1-2% of the patients; we present an exemplary case.

Histamine suppresses epidermal keratinocyte differentiation and impairs skin barrier function in a human skin model

Background

Defects in keratinocyte differentiation and skin barrier are important features of inflammatory skin diseases like atopic dermatitis. Mast cells and their main mediator histamine are abundant in inflamed skin and thus may contribute to disease pathogenesis.

Methods

Human primary keratinocytes were cultured under differentiation-promoting conditions in the presence and absence of histamine, histamine receptor agonists and antagonists. The expression of differentiation-associated genes and epidermal junction proteins was quantified by real-time PCR, Western blot, and immunofluorescence labeling. The barrier function of human skin models was tested by the application of biotin as tracer molecule.

Results

The addition of histamine to human keratinocyte cultures and organotypic skin models reduced the expression of the differentiation-associated proteins keratin 1/10, filaggrin, and loricrin by 80–95%. Moreover, the addition of histamine to skin models resulted in the loss of the granular layer and thinning of the epidermis and stratum corneum by 50%. The histamine receptor H1R agonist, 2-pyridylethylamine, suppressed keratinocyte differentiation to the same extent as did histamine. Correspondingly, cetirizine, an antagonist of H1R, virtually abrogated the effect of histamine. The expression of tight junction proteins zona occludens-1, occludin, claudin-1, and claudin-4, as well as that of desmosomal junction proteins corneodesmosin and desmoglein-1, was down-regulated by histamine. The tracer molecule biotin readily penetrated the tight junction barrier of skin cultures grown in the presence of histamine, while their diffusion was completely blocked in nontreated controls.

Conclusions

Our findings suggest a new mechanism by which mast cell activation and histamine release contribute to skin barrier defects in inflammatory skin diseases.

[Remission of an iatrogenic Kaposi sarcoma in a patient with myasthenia gravis after switching immunosuppressive therapy to the mTOR inhibitor everolimus]

Iatrogenic Kaposi sarcomas (KS) in organ transplant recipients are often treated by switching immunosuppressive therapy to an mTOR inhibitor, such as sirolimus or everolimus, as these have immunosuppressive as well as anti-tumor effects. We report on an 80-year-old male patient who developed a disseminated cutaneous KS during therapy with prednisone and azathioprine for myasthenia gravis. After discontinuation of azathioprine therapy and despite continuing therapy with cortisone, the KS progressed and autoantibody levels against the nicotinic acetylcholine receptor increased. During the administration of everolimus, a long-term near-complete remission of KS and a decrease in autoantibodies took place. This case study illustrates that even in non-organ transplant patients with iatrogenic KS, switching to immunosuppressive therapy using an mTOR inhibitor can be beneficial.