Personalized Development of Antisense Oligonucleotides for Exon Skipping Restores Type XVII Collagen Expression in Junctional Epidermolysis Bullosa.

Intermediate junctional epidermolysis bullosa caused by mutations in the COL17A1 gene is characterized by the frequent development of blisters and erosions on the skin and mucous membranes. The rarity of the disease and the heterogeneity of the underlying mutations renders therapy developments challenging. However, the high number of short in-frame exons facilitates the use of antisense oligonucleotides (AON) to restore collagen 17 (C17) expression by inducing exon skipping. In a personalized approach, we designed and tested three AONs in combination with a cationic liposomal carrier for their ability to induce skipping of COL17A1 exon 7 in 2D culture and in 3D skin equivalents. We show that AON-induced exon skipping excludes the targeted exon from pre-mRNA processing, which restores the reading frame, leading to the expression of a slightly truncated protein. Furthermore, the expression and correct deposition of C17 at the dermal-epidermal junction indicates its functionality. Thus, we assume AON-mediated exon skipping to be a promising tool for the treatment of junctional epidermolysis bullosa, particularly applicable in a personalized manner for rare genotypes.

Phase 1 Dose Escalation Trial of Ipilimumab and Stereotactic Body Radiation Therapy in Metastatic Melanoma.

PURPOSE: To report the results of a phase 1 trial evaluating the safety of the ipilimumab/radiation therapy combination in patients with metastatic melanoma. PATIENTS AND METHODS: Thirteen patients with metastatic melanoma were enrolled. Trial treatment consisted of 4 cycles of ipilimumab in combination with concurrent dose-escalated high-dose radiation therapy to 1 lesion administered before the third cycle of ipilimumab. RESULTS: Grade 3 or 4 ipilimumab-related adverse events occurred in 25% of patients. The maximum tolerated radiation therapy dose was not reached. Local control of the irradiated lesions was achieved in 11 of 12 irradiated patients (1 patient had progressive disease before irradiation and dropped out of the trial). Evaluation of the nonirradiated lesions demonstrated that 3 of 13 patients experienced clinical benefit, with 1 patient developing a partial response and 2 patients having confirmed stable disease. Immunomonitoring data showed that in patients without clinical benefit, factors linked to immunotolerance increased early after the initiation of ipilimumab, suggesting that early initiation of radiation therapy might be more effective if combined with ipilimumab. CONCLUSIONS: Our findings suggest that the combination of ipilimumab and high-dose radiation therapy is feasible and safe.

A phase I/II trial of fixed-dose stereotactic body radiotherapy with sequential or concurrent pembrolizumab in metastatic urothelial carcinoma: evaluation of safety and clinical and immunologic response.

BACKGROUND: Current first-line standard of therapy for metastatic urothelial carcinoma is platinum-based combination chemotherapy. Pembrolizumab in phase III has demonstrated a promising overall response rate of 21.1% in patients with progression or recurrence after platinum-based chemotherapy. Preclinical and clinical evidence suggests that radiotherapy has a systemic anti-cancer immune effect and can increase the level of PD-L1 and tumor infiltrating lymphocytes in the tumor microenvironment. These findings gave rise to the hypothesis that the combination of radiotherapy with anti-PD1 treatment could lead to a synergistic effect, hereby enhancing response rates. METHODS: The phase I part will assess the dose limiting toxicity of the combination treatment of stereotactic body radiotherapy (SBRT) with four cycles of pembrolizumab (200 mg intravenously, every 3 weeks) in patients with metastatic urothelial carcinoma. The dose of both pembrolizumab and SBRT will be fixed, yet the patients will be randomized to receive SBRT either before the first cycle of pembrolizumab or before the third cycle of pembrolizumab. SBRT will be delivered (24 Gy in 3 fractions every other day) to the largest metastatic lesion. Secondary objectives include response rate according to RECIST v1.1 and immune related response criteria, progression-free survival and overall survival. The systemic immune effect triggered by the combination therapy will be monitored on various time points during the trial. The PD-L1/TIL status of the tumors will be analyzed via immunohistochemistry and response rates in the subgroups will be analyzed separately. A Simon's two-stage optimum design is used to select the treatment arm associated with the best response rate and with acceptable toxicity to proceed to the phase II trial. In this phase, 13 additional patients will be accrued to receive study treatment. DISCUSSION: The progress made in the field of immunotherapy has lead to promising breakthroughs in various solid malignancies. Unfortunately, the majority of patients do not respond. The current trial will shed light on the toxicity and potential anti-tumor activity of the combination of radiotherapy with anti-PD1 treatment and may identify potential new markers for response and resistance to therapy. Trial registration this trial is registered on clinicaltrials.gov (NCT02826564).

A phase II trial of stereotactic body radiotherapy with concurrent anti-PD1 treatment in metastatic melanoma: evaluation of clinical and immunologic response.

BACKGROUND: Antibodies blocking programmed cell death 1 (PD-1) have encouraging responses in patients with metastatic melanoma. Response to anti-PD-1 treatment requires pre-existing CD8+ T cells that are negatively regulated by PD-1-mediated adaptive immune resistance. Unfortunately, less than half of melanoma tumours have these characteristics. Combining anti-PD-1 treatment with other immunomodulating treatments to activate CD8+ T cells is therefore of vital importance to increase response rates and long-term survival benefit in melanoma patients. Both preclinical and retrospective clinical data support the hypothesis that radiotherapy increases the response rates to anti-PD-1 treatment by stimulating the accumulation and activation of CD8+ T cells in the tumour microenvironment. Combining radiotherapy with a PD-1 blocking antibody might therefore increase response rates and even induce long-term survival. The current phase II study will be testing these hypotheses and aims to improve local and distant tumour responses by exploiting the pro-immunogenic effects of radiotherapy in addition to anti-PD-1 treatment. METHODS: The trial will be conducted in patients with metastatic melanoma. Nivolumab or pembrolizumab, both antibodies that target PD-1, will be administrated according to the recommended dosing schedule. Prior to the 2nd cycle, radiotherapy will be delivered in three fractions of 8 Gy to the largest FDG-avid metastatic lesion. The primary endpoint is the proportion of patients with a partial or complete response in non-irradiated metastases according to RECIST v1.1. Secondary endpoints include response rate according to immune related response criteria, metabolic response, local control and survival. To identify peripheral blood biomarkers, peripheral blood mononuclear cells and serum samples will be collected prospectively before, during and after treatment and subjected to flow cytometry and cytokine measurement. DISCUSSION: The current phase II trial aims at exploring the suggested benefits of combining anti-PD-1 treatment and radiotherapy. The translational focus on immunologic markers might be suitable for predicting efficacy and monitoring the effect so to improve patient selection for future clinical applications. ClinicalTrials.gov Identifier NCT02821182.

Systemic immune changes associated with adjuvant interferon-α2b-therapy in stage III melanoma patients: failure at the effector phase?

Interferon-α (IFN-α) is the only approved adjuvant treatment for high-risk melanoma patients in Europe, but the impact on overall survival is low. Although it is believed that IFN-α exerts its effects through immunomodulation, data on its impact on circulating immune cells are scarce. Flow cytometry was performed on peripheral blood mononuclear cells of eight IFN-α2b-treated stage III melanoma patients and 26 untreated stage III melanoma patients as controls to enumerate myeloid and plasmacytoid dendritic cells (mDC and pDC), monocytic and polymorphonuclear myeloid-derived suppressor cells (mMDSC and pmnMDSC) and cytotoxic and regulatory T-cells (Tregs). The expression of several immunosuppressive markers [indoleamine 2,3-dioxygenase (IDO), programmed-death ligand-1 (PD-L1) and cytotoxic T-lymphocyte antigen-4 (CTLA4)] was explored. IDO activity in the blood was confirmed by ultra-performance liquid chromatography. Compared with controls, IFN-α2b treatment was associated with increased IDO expression by pDCs (P=0.021) and an increased kynurenine/tryptophan ratio in the serum (P=0.004), compatible with IDO enzyme activity. Furthermore, IFN-α2b-treated patients had a decreased mDC/DC ratio (P=0.002), decreased CD3+ lymphocytes (P=0.034) and increased circulating Treg (P<0.001) and PD-L1+cytotoxic T-cell (P=0.001) frequencies. IDO expression is upregulated in circulating pDCs of high-risk melanoma patients treated with adjuvant IFN-α2b. This is associated with tryptophan consumption in the patients' serum and higher Treg and PD-L1+cytotoxic T-cell frequencies. We hypothesize that in IFN-α2b-treated patients, IDO activity acts as a negative feedback mechanism and might limit the clinical efficacy of IFN-α2b therapy. The underlying mechanism should be explored as this could lead to more efficient immunotherapies.

Clinical significance of plasmacytoid dendritic cells and myeloid-derived suppressor cells in melanoma.

BACKGROUND: Immune markers in the peripheral blood of melanoma patients could provide prognostic information. However, there is currently no consensus on which circulating cell types have more clinical impact. We therefore evaluated myeloid-derived suppressor cells (MDSC), dendritic cells (DC), cytotoxic T-cells and regulatory T-cells (Treg) in a series of blood samples of melanoma patients in different stages of disease. METHODS: Flow cytometry was performed on peripheral blood mononuclear cells of 69 stage I to IV melanoma patients with a median follow-up of 39 months after diagnosis to measure the percentage of monocytic MDSCs (mMDSCs), polymorphonuclear MDSCs (pmnMDSCs), myeloid DCs (mDCs), plasmacytoid DCs (pDCs), cytotoxic T-cells and Tregs. We also assessed the expression of PD-L1 and CTLA-4 in cytotoxic T-cells and Tregs respectively. The impact of cell frequencies on prognosis was tested with multivariate Cox regression modelling. RESULTS: Circulating pDC levels were decreased in patients with advanced (P = 0.001) or active (P = 0.002) disease. Low pDC levels conferred an independent negative impact on overall (P = 0.025) and progression-free survival (P = 0.036). Even before relapse, a decrease in pDC levels was observed (P = 0.002, correlation coefficient 0.898). High levels of circulating MDSCs (>4.13%) have an independent negative prognostic impact on OS (P = 0.012). MDSC levels were associated with decreased CD3+ (P < 0.001) and CD3 + CD8+ (P = 0.017) T-cell levels. Conversely, patients with high MDSC levels had more PD-L1+ T-cells (P = 0.033) and more CTLA-4 expression by Tregs (P = 0.003). pDCs and MDSCs were inversely correlated (P = 0.004). The impact of pDC levels on prognosis and prediction of the presence of systemic disease was stronger than that of MDSC levels. CONCLUSION: We demonstrated that circulating pDC and MDSC levels are inversely correlated but have an independent prognostic value in melanoma patients. These cell types represent a single immunologic system and should be evaluated together. Both are key players in the immunological climate in melanoma patients, as they are correlated with circulating cytotoxic and regulatory T-cells. Circulating pDC and MDSC levels should be considered in future immunoprofiling efforts as they could impact disease management.

Development of an oral mucosa model to study host-microbiome interactions during wound healing.

Crosstalk between the human host and its microbiota is reported to influence various diseases such as mucositis. Fundamental research in this area is however complicated by the time frame restrictions during which host-microbe interactions can be studied in vitro. The model proposed in this paper, consisting of an oral epithelium and biofilm, can be used to study microbe-host crosstalk in vitro in non-infectious conditions up to 72 h. Microbiota derived from oral swabs were cultured on an agar/mucin layer and challenged with monolayers of keratinocytes grown on plastic or collagen type I layers embedded with fibroblasts. The overall microbial biofilm composition in terms of diversity remained representative for the oral microbiome, whilst the epithelial cell morphology and viability were unaffected. Applying the model to investigate wound healing revealed a reduced healing of 30 % in the presence of microbiota, which was not caused by a reduction of the proliferation index (52.1-61.5) or a significantly increased number of apoptotic (1-1.13) or necrotic (32-30.5 %) cells. Since the model allows the separate study of the microbial and cellular exometabolome, the biofilm and epithelial characteristics after co-culturing, it is applicable for investigations within fundamental research and for the discovery and development of agents that promote wound healing.

The biology of hyperpigmentation syndromes.

Hyperpigmentation is a key feature in a variety of inherited and acquired syndromes. Nonetheless, determining the exact diagnosis only on the clinical phenotype can be challenging, and a detailed search for associated symptoms is often of crucial importance. As pigmentation pathways are regulated by complex signaling transduction cascades (e.g. MSH/cAMP, KIT signaling pathways), the underlying defects leading to elevated melanin production are numerous. With regard to treatment, limited therapeutic options exist, each with specific side effects. In acquired hyperpigmentation, the melanin deposition may, however, be reversible after adequate therapy of the underlying disorder or even disappear spontaneously. In this review, we provide an overview of the biology of hyperpigmentation syndromes classified according to the main underlying defect that deregulates physiological melanogenesis. The identification of novel genes or key players involved in hyperpigmentary disorders is becoming increasingly important in view of the development of safer and more efficient treatments.

Differential regulation of extracellular matrix protein expression in carcinoma-associated fibroblasts by TGF-ß1 regulates cancer cell spreading but not adhesion.

Cancer progression is characterized by a complex reciprocity between neoplastic epithelium and adjacent stromal cells. In ductal carcinoma in situ (DCIS) of the breast, both reduced stromal decorin expression and myxoid stroma are correlated with increased recurrence risk. In this study, we aimed to investigate paracrine regulation of expression of decorin and related extracellular matrix (ECM) proteins in cancer-associated fibroblasts (CAFs). Transforming growth factor-ß1 (TGF-ß1) was identified as a competent ECM modulator, as it reduced decorin and strongly enhanced versican, biglycan and type I collagen expression. Similar but less pronounced effects were observed when fibroblasts were treated with basic fibroblast growth factor (bFGF). Despite this concerted ECM modulation, TGF-ß1 and bFGF differentially regulated alpha-smooth muscle actin (α-SMA) expression, which is often proposed as a CAF-marker. Cancer cell-derived secretomes induced versican and biglycan expression in fibroblasts. Immunohistochemistry on twenty DCIS specimens showed a trend toward periductal versican overexpression in DCIS with myxoid stroma. Cancer cell adhesion was inhibited by decorin, but not by CAF-derived matrices. Cancer cells presented significantly enhanced spreading when seeded on matrices derived from TGF-ß1-treated CAF. Altogether these data indicate that preinvasive cancerous lesions might modulate the composition of surrounding stroma through TGF-ß1 release to obtain an invasion-permissive microenvironment.

miR-145 overexpression suppresses the migration and invasion of metastatic melanoma cells.

MicroRNAs (miRNAs) are post-transcriptional modulators of gene expression which play important roles in tumorigenesis and cancer metastasis. Since they are often highly deregulated in various types of cancer, miRNAs may be effective treatment targets. miRNA profiling studies of melanoma have led to the identification of several tumor suppressor miRNAs. One of these include miR-145, although functional data proving its specific function are limited. Therefore, in this study, we examined the expression levels of miR-145 in three melanoma cell lines (BLM, FM3P and WM793). Additional gain-of-function experiments revealed that miR-145 exerts an anti-proliferative effect in the primary, non-invasive melanoma cell line, WM793, whereas cell migration and the invasive potential of metastatic melanoma cells was suppressed following transfection with miR-145 mimics. In order to investigate the mechanisms by which miR-145 exerts its invasion suppressor function, we examined the expression level of target genes [fascin homolog 1 (FSCN1), myosin­Va (MYO5A and SOX9] and that of an indirect target (RAB27A) following the overexpression of miR-145. The results showed that SOX9, MYO5A and RAB27A were not involved in the biological effects caused by miR-145 mimics. Surprisingly, we discovered that miR-145 in melanoma, in contrast to many other tumor types, does not necessarily act via the target, FSCN1, since the downregulation of FSCN1 did not inhibit cell proliferation or migration but, on the contrary, increased cell invasion in two out of the three melanoma cell lines examined. Our in vitro data is in accordance with previously reported in vivo data describing the low expression of FSCN1 in malignant melanomas when compared to dysplastic nevi, suggesting that the expression of FSCN1 decreases as the formation and progression stage of melanoma advances. In conclusion, our data provide evidence that miR-145 is an invasion suppressor in metastatic melanoma cells. Despite the fact that it remains unclear which genes or pathways are regulated by miR-145 in melanoma, miR-145 may serve as a useful therapeutic agent in melanoma when re-expressed in situ.

Identification of miR-145 as a key regulator of the pigmentary process.

The current treatments for hyperpigmentation are often associated with a lack of efficacy and adverse side effects. We hypothesized that microRNA (miRNA)-based treatments may offer an attractive alternative by specifically targeting key genes in melanogenesis. The aim of this study was to identify miRNAs interfering with the pigmentary process and to assess their functional role. miRNA profiling was performed on mouse melanocytes after three consecutive treatments involving forskolin and solar-simulated UV (ssUV) irradiation. Sixteen miRNAs were identified as differentially expressed in treated melan-a cells versus untreated cells. Remarkably, a 15-fold downregulation of miR-145 was detected. Overexpression or downregulation of miR-145 in melan-a cells revealed reduced or increased expression of Sox9, Mitf, Tyr, Trp1, Myo5a, Rab27a, and Fscn1, respectively. Moreover, a luciferase reporter assay demonstrated direct targeting of Myo5a by miR-145 in mouse and human melanocytes. Immunofluorescence tagging of melanosomes in miR-145-transfected human melanocytes displayed perinuclear accumulation of melanosomes with additional hypopigmentation of harvested cell pellets. In conclusion, this study has established an miRNA signature associated with forskolin and ssUV treatment. The significant down- or upregulation of major pigmentation genes, after modulating miR-145 expression, suggests a key role for miR-145 in regulating melanogenesis.

Immune mediated mechanisms of melanocyte destruction: Paving the way for efficient immunotherapeutic strategies against melanoma.

Insights into immune reactions against benign and malignant melanocytes may help the development of more efficient immunotherapeutic treatments for melanoma. The interplay between an active systemic antitumor immunity and a responsive local tumor environment is crucial to achieve effective clinical responses. Increasing evidence confirms this strategy can lead to an adequate and durable immunosurveillance of melanocytes.

Indoleamine 2,3-dioxygenase, a new prognostic marker in sentinel lymph nodes of melanoma patients.

BACKGROUND: Indoleamine 2,3-dioxygenase (IDO), an enzyme with immunosuppressive properties is considered as a factor that impairs the antitumour immune response in melanoma. In this study, we investigated the expression of IDO in sentinel nodes of melanoma patients to determine its prognostic relevance. PATIENTS AND METHODS: One hundred and sixteen melanoma patients were enrolled in this study with a median follow-up time after diagnosis of 71 months. The expression of IDO and forkhead box P3 (Foxp3) in the sentinel lymph nodes was determined by immunohistochemistry and correlated with progression-free survival and overall survival. In 42 patients, regulatory T cells were investigated by flow cytometry. RESULTS: Cox regression survival analysis showed a significant negative effect of IDO expression on progression-free survival (p = 0.015) and overall survival (p = 0.010). High IDO expression was correlated with a significant higher frequency of Foxp3-positive cells in uninvaded lymph nodes (p = 0.016). The presence of IDO expression in the sentinel nodes was not associated with an increased frequency of circulating regulatory T cells (Tregs) but was significantly correlated with an increased mean fluorescence intensity of Cytotoxic T-Lymphocyte Antigen 4 (CTLA-4) in Tregs (p = 0.019). After CD3CD28 stimulation, peripheral blood mononuclear cells of patients with high IDO expression showed a lower production of interferon-gamma (IFN-γ) (p = 0.025). CONCLUSIONS: This study points to an independent predictive role of IDO on survival, especially in melanoma patients with uninvolved sentinel nodes. Investigating IDO expression in the sentinel nodes of melanoma patients may be a useful marker to pre-identify patients with a less favourable prognosis in stage I and II disease.

Melanocyte-specific immune response in a patient with multiple regressing nevi and a history of melanoma.

BACKGROUND/AIM: Regressing nevi are considered an example of an efficient early antitumoral response preventing the development of neoplasia. The underlying mechanism has not been elucidated, although an immune-based destruction of melanocytes is supposed. The aim of this study was to provide evidence of an effective immunosurveillance of pigment lesions in a patient at high risk of melanoma. CASE REPORT: A patient with the dysplastic nevus syndrome and a history of melanoma was included in this study. Since 2003, a marked regression of almost all nevi was observed. Immunohistochemistry was performed and the antigen specificity of T-cells was analyzed on T-cells isolated from a regressing nevus by flow cytometry using HLA-A2-peptide tetramers containing Mart-1(26-35), gp100(280-288), gp100(209-217) and tyrosinase(369-377). Immunohistochemistry of the regressing nevi showed a strong infiltrate of CD4 + and CD8 + T-cells. Flow cytometric analyses demonstrated the presence of a CD8 + T-cell response against gp100(280-288) and Mart-1(26-35) both in peripheral blood and in a regressing nevus. CONCLUSION: These findings indicate that an immune reaction against melanocyte differentiation antigens can target specifically nevi without signs of vitiligo and suggests that boosting the anti-melanocyte immune response in patients at high risk for melanoma may prevent tumor development at an early stage.

P-cadherin counteracts myosin II-B function: implications in melanoma progression.

BACKGROUND: Malignant transformation of melanocytes is frequently attended by a switch in cadherin expression profile as shown for E- and N-cadherin. For P-cadherin, downregulation in metastasizing melanoma has been demonstrated, and over-expression of P-cadherin in melanoma cell lines has been shown to inhibit invasion. The strong invasive and metastatic nature of cutaneous melanoma implies a deregulated interplay between intercellular adhesion and migration-related molecules RESULTS: In this study we performed a microarray analysis to compare the mRNA expression profile of an invasive BLM melanoma cell line (BLM LIE) and the non-invasive P-cadherin over-expression variant (BLM P-cad). Results indicate that nonmuscle myosin II-B is downregulated in BLM P-cad. Moreover, myosin II-B plays a major role in melanoma migration and invasiveness by retracting the tail during the migratory cycle, as shown by the localization of myosin II-B stress fibers relative to Golgi and the higher levels of phosphorylated myosin light chain. Analysis of P-cadherin and myosin II-B in nodular melanoma sections and in a panel of melanoma cell lines further confirmed that there is an inverse relationship between both molecules. CONCLUSIONS: Therefore, we conclude that P-cadherin counteracts the expression and function of myosin II-B, resulting in the suppression of the invasive and migratory behaviour of BLM melanoma cells.

The flavonoid tangeretin activates the unfolded protein response and synergizes with imatinib in the erythroleukemia cell line K562.

We explored the mechanism of cell death of the polymethoxyflavone tangeretin (TAN) in K562 breakpoint cluster region-abelson murine leukemia (Bcr-Abl+) cells. Flow cytometric analysis showed that TAN arrested the cells in the G(2)/M phase and stimulated an accumulation of the cells in the sub-G(0) phase. TAN-induced cell death was evidenced by poly(ADP)-ribose polymerase cleavage, DNA laddering fragmentation, activation of the caspase cascade and downregulation of the antiapoptotic proteins Mcl-1 and Bcl-x(L). Pretreatment with the pancaspase inhibitor Z-VAD-FMK_blocked caspase activation and cell cycle arrest but did not inhibit apoptosis which suggest that other cell killing mechanisms like endoplasmic reticulum (ER)-associated cell death pathways could be involved. We demonstrated that TAN-induced apoptosis was preceded by a rapid activation of the proapoptotic arm of the unfolded protein response, namely PKR-like ER kinase. This was accompanied by enhanced levels of glucose-regulated protein of 78 kDa and of spliced X-box binding protein 1. Furthermore, TAN sensitized K562 cells to the cell killing effects of imatinib via an apoptotic mechanism. In conclusion, our results suggest that TAN is able to induce apoptosis in Bcr-Abl+ cells via cell cycle arrest and the induction of the unfolded protein response, and has synergistic cytotoxicity with imatinib.

Xanthohumol activates the proapoptotic arm of the unfolded protein response in chronic lymphocytic leukemia.

BACKGROUND: Chronic lymphocytic leukemia (CLL) is an incurable disease with a natural history of increasing resistance to chemotherapy. A novel approach to overcome chemotherapy resistance may be targeting the endoplasmic reticulum (ER). PATIENTS AND METHODS: The involvement of the unfolded protein response (UPR) in the cell killing effect of xanthohumol (X) was examined in 18 patient samples. RESULTS: X-induced apoptosis of CLL cells was accompanied by the induction of glucose-regulated protein of 78 kDa (GRP78) and heat-shock protein of 70 kDa (Hsp70) protein levels and by sustained phosphorylation of the eukaryotic translation initiation factor 2 (eIF2alpha), suggesting the involvement of the ER stress transducer, the double-stranded RNA-activated protein kinase (PKR)-like ER kinase (PERK). The X-box-binding protein 1 (XBP1) mRNA was spliced but no clear activation of activating transcription factor 6 (ATF6) was observed. The proapoptotic outcome was further demonstrated by the up-regulation of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP), down-regulation of myeloid cell leukemia 1 (Mcl-1) and B-cell lymphoma 2 (Bcl-2), cleavage of poly-(ADP)-ribose polymerase (PARP) and processing of caspase-3, -4 and -9. Furthermore, X showed proteasome inhibitory activity. CONCLUSION: X stimulates the proapoptotic arm of the UPR in ex vivo CLL cells, suggesting that ER stress may play an important role during X-induced apoptosis.

Steroid effects on ZAP-70 and SYK in relation to apoptosis in poor prognosis chronic lymphocytic leukemia.

There is resurgent interest in glucocorticoids (GCs) in the treatment of poor prognosis chronic lymphocytic leukemia (CLL). Little is known however on how GCs induce apoptosis in CLL. Methylprednisolone (MP) induces apoptosis in ZAP-70 positive CLL more readily than in ZAP-70 negative CLL, which is in contrast to the effects of radiation and chemotherapy. The increased GC sensitivity of ZAP-70+ CLL was studied in relation to the expression status of ZAP-70 and the related signal transducing tyrosine kinase SYK. Both ZAP-70 and SYK were downregulated by GC treatment. Moreover, SYK was dephosphorylated by the phosphatase PTP1B of which the expression and translation levels were induced by GCs. Inhibition of PTP1B successfully restored ZAP-70 expression and SYK phosphorylation but did not interfere with GC-induced apoptosis. Therefore, the downregulation of ZAP-70 and P-SYK per se during treatment with GCs is not sufficient to induce apoptosis, and different mechanisms must therefore be responsible for the increased steroid sensitivity of ZAP-70+ CLL.

Griscelli syndrome: a model system to study vesicular trafficking.

Griscelli syndrome (GS) is a rare autosomal recessive disorder caused by mutations in either the myosin VA (GS1), RAB27A (GS2) or melanophilin (GS3) genes. The three GS subtypes are commonly characterized by pigment dilution of the skin and hair, due to defects involving melanosome transport in melanocytes. Here, we review how detailed studies concerning GS have contributed to a better understanding of the molecular mechanisms involved in vesicle transport and membrane trafficking processes. Additionally, we demonstrate that the identification and biological analysis of novel disease-causing mutations highlighted the functional importance of the RAB27A-MLPH-MYO5A tripartite complex in intracellular melanosome transport. As the small GTPase Rab27a is able to interact with multiple effectors, including Slp2-a and Myrip, we report on their presumed role in melanosome transport. Furthermore, we summarize data suggesting that RAB27B and RAB27A are functionally redundant and hereby provide further insight into the pathogenesis of GS2. Finally, we discuss how the gathered knowledge about the RAB27A-MLPH-MYO5A tripartite complex can be translated into a possible therapeutic application to reduce (hyper)pigmentation of the skin.

The role of RhoC in growth and metastatic capacity of melanoma.

BACKGROUND: RhoC overexpression in tumor cells promotes invasive and metastatic behavior. RhoC expression levels have been correlated with tumor progression and metastasis in multiple human cancers. In melanoma, RhoC is upregulated in highly metastatic tumors. Induced expression in melanoma cell lines resulted in invasion and metastasis, whereas inhibition of RhoC reversed the metastatic phenotype both in vitro and in vivo. METHODS: RhoC mRNA and protein expression in two human melanoma cell lines (DX3aza and MeWo) and pooled primary melanocytes were investigated by means of real-time quantitative polymerase chain reaction and western blotting. RhoC protein expression was evaluated in 123 primary cutaneous melanoma samples by the use of immunohistochemistry and correlated with known prognostic features. RESULTS: RhoC upregulation was observed in the highly metastatic DX3aza cell line, whereas in MeWo, only low expression levels could be detected. RhoC expression in primary cutaneous melanoma was strongly associated with thicker and ulcerated tumors. RhoC expression was associated with the presence of lymphatic metastases at the time of diagnosis and shorter disease-free and overall survival rates, without being an independent predictor. CONCLUSION: These results further support a role for RhoC in growth and metastasis of melanoma.