PLX4032: does it keep its promise for metastatic melanoma treatment?

Importance of the field: Activating mutations in the BRAF kinase gene have been identified in 50% of all melanomas. PLX4032, a selective and potent inhibitor of BRAF V600E mutant tumor cells, has shown inhibition of tumor growth in cell lines harboring BRAF V600E mutations. Data from early clinical trials showed promising results in the treatment of patients with metastatic melanoma.

Areas covered in this review: An extensive literature search was conducted that included published articles and abstracts on PLX4032 to evaluate the existing data in both preclinical and Phase I–II studies.

What the reader will gain: The review comprises the rationale for choosing a selective BRAF inhibitor for certain types of melanoma, its mode of action, associated toxicities and potential pitfalls.

Take home message: Despite the convincing response rates in Phase I trials, duration of tumor response is limited in some patients, and a cure cannot be expected. Intrinsic and acquired PLX4032 resistance still has to be investigated; signaling pathway switching is probably the most important factor for development of resistance. Combination therapy with simultaneous inhibition of different pathways might be more effective and warrants further investigation. The toxicity profile of PLX4032 is considerably low, and special attention is needed to address the development of keratoacanthomas and cutaneous squamous cell carcinomas.     

Induction of Resistance to BRAF Inhibitor Is Associated with the Inability of Spry2 to Inhibit BRAF-V600E Activity in BRAF Mutant Cells

The clinical benefits of oncogenic BRAF inhibitor therapies are limited by the emergence of drug resistance. In this study, we investigated the role of a negative regulator of the MAPK pathway, Spry2, in acquired resistance using BRAF inhibitor-resistant derivatives of the BRAF-V600E melanoma (A375P/Mdr). Real-time RT-PCR analysis indicated that the expression of Spry2 was higher in A375P cells harboring the BRAF V600E mutation compared with wild-type BRAF-bearing cells (SK-MEL-2) that are resistant to BRAF inhibitors. This result suggests the ability of BRAF V600E to evade feedback suppression in cell lines with BRAF V600E mutations despite high Spry2 expression. Most interestingly, Spry2 exhibited strongly reduced expression in A375P/Mdr cells with acquired resistance to BRAF inhibitors. Furthermore, the overexpression of Spry2 partially restored sensitivity to the BRAF inhibitor PLX4720 in two BRAF inhibitor-resistant cells, indicating a positive role for Spry2 in the growth inhibition induced by BRAF inhibitors. On the other hand, long-term treatment with PLX4720 induced pERK reactivation following BRAF inhibition in A375P cells, indicating that negative feedback including Spry2 may be bypassed in BRAF mutant melanoma cells. In addition, the siRNA-mediated knockdown of Raf-1 attenuated the rebound activation of ERK stimulated by PLX4720 in A375P cells, strongly suggesting the positive role of Raf-1 kinase in ERK activation in response to BRAF inhibition. Taken together, these data suggest that RAF signaling may be released from negative feedback inhibition through interacting with Spry2, leading to ERK rebound and, consequently, the induction of acquired resistance to BRAF inhibitors.     

Overcoming metastatic melanoma with BRAF inhibitors

Melanoma has the capacity to spread via the blood stream to the brain, and has been notoriously resistant to drug therapy. An activating mutation in the gene encoding BRAF is known to be responsible for half of melanomas. This article provides a review of GSK2118436 and PLX4032 as potential therapeutics for the treatment of melanomas by inhibiting oncogenic BRAF.     

BRAF as therapeutic target in melanoma

BRAF is a member of the RAF kinase family, which acts in the ERK/MAP kinase pathway, a signalling cascade that regulates cellular proliferation, differentiation and survival. Single point mutations can turn BRAF into an oncogene, but there appears to be a cell type/tumour specific relevance for BRAF kinase-activating mutations, since they are found predominantly in cutaneous melanoma. With the success of targeting other oncogenic kinases such as BCR-ABL, KIT or members of the epidermal-growth factor receptor (EGFR) family in other cancers, the expectations were high when the first RAF kinase-targeting drug (sorafenib) reached clinical trials. However, disappointingly the first studies using sorafenib in melanoma patients did not show the anticipated single agent efficacy. More recently, the resolution of the BRAF crystal structure has led to the development of better, more specific BRAF inhibitors such as the Plexxikon compound, PLX4032, which induced a dramatic response rate in phase I trials, validating BRAF as a clinically relevant target. In addition, our understanding of melanoma biology and the role BRAF is playing therein has improved significantly. The complexity in the ERK/MAP kinase pathway including important feedback mechanisms has been dissected, and the relevance of cross-talks with other signalling pathways has been revealed, suggesting strategies for the design of improved, more efficient combinatorial therapies. This review highlights the relevance of BRAF and the ERK/MAP kinase pathway for melanoma cell biology and discusses some of the recent advances in both, the understanding of BRAF function in melanoma and the development of improved BRAF targeting inhibitors.     

Development and characterization of poly(lactic-co-glycolic) acid nanoparticles loaded with copaiba oleoresin

Abstract

Copaiba oleoresin (CPO), obtained from Copaifera landgroffii, is described as active to a large number of diseases and more recently in the endometriosis treatment. In this work, poly(lactic-co-glycolic acid) (PLGA) nanoparticles containing CPO were obtained using the design of experiments (DOE) as a tool to optimize the production process. The nanoparticles optimized by means of DOE presented an activity in relation to the cellular viability of endometrial cells. The DOE showed that higher amounts of CPO combined with higher surfactant concentrations resulted in better encapsulation efficiency and size distribution along with good stability after freeze drying. The encapsulation efficiency was over 80% for all produced nanoparticles, which also presented sizes below 300?nm and spherical shape. A decrease in viability of endometrial stromal cells from ectopic endometrium of patients with endometriosis and from eutopic endometriotic lesions was demonstrated after 48?h of incubation with the CPO nanoparticles. The nanoparticles without CPO were not able to alter the cell viability of the same cells, indicating that this material was not cytotoxic to the tested cells and suggesting that the effect was specific to CPO. The results indicate that the use of CPO nanoparticles may represent a promising alternative for the treatment of endometriosis.     

Differential Sensitivity of Wild-Type and BRAF-Mutated Cells to Combined BRAF and Autophagy Inhibition

BRAF inhibitors are insufficient monotherapies for BRAF-mutated cancer; therefore, we investigated which inhibitory pathway would yield the most effective therapeutic approach when targeted in combination with BRAF inhibition. The oncogenic BRAF inhibitor, PLX4720, increased basal autophagic flux in BRAF-mutated cells compared to wild-type (WT) BRAF cells. Interestingly, early autophagy inhibition improved the effectiveness of PLX4720 regardless of BRAF mutation, whereas late autophagy inhibition did not. Although ATG5 knockout led to PLX4720 resistance in both WT and BRAF-mutated cells, the MEK inhibitor trametinib exhibited a synergistic effect on PLX4720 sensitivity in WT BRAF cells but not in BRAF-mutated cells. Conversely, the prolonged inhibition of endoplasmic reticulum (ER) stress reduced basal autophagy in BRAF-mutated cells, thereby increasing PLX4720 sensitivity. Taken together, our results suggest that the combined inhibition of ER stress and BRAF may simultaneously suppress both pro-survival ER stress and autophagy, and may therefore be suitable for treatment of BRAF-mutated tumors whose autophagy is increased by chronic ER stress. Similarly, for WT BRAF tumors, therapies targeting MEK signaling may be a more effective treatment strategy. Together, this study presents a rational combination treatment strategy to improve the efficacy of BRAF inhibitors depending on BRAF mutation status.     

Activation of Signal Transduction Kinases by Tamoxifen

Purpose. To study the signal transduction mechanisms of tamoxifen via the activation of MAPKs, JNK and ERK in order to understand its regulation of gene expression. Methods. The effects of tamoxifen (TAM) on the activation of serine/ threonine mitogen-activated protein kinase (MAPK, p42/ERK2) and the stress-activated protein kinases (p46 SAPK or c-Jun N-terminal kinase, JNK1) were evaluated using a human cervical epitheloid carcinoma HeLa cell line. Results. TAM activated both JNK1 and ERK2 activities in a time- and dose-dependent manner in HeLa cells. The activation of JNK1 was enhanced when the cells were pretreated with prooxidant H₂O₂. Conclusions. These studies show that TAM activates the signal transduction kinases, JNK1 and ERK2, which may play important roles in the regulation of gene expression by TAM.     

BRAF as a target for cancer therapy

Tumors with mutations in the gene encoding the serine-threonine protein kinase BRAF are dependent on the MAPK signaling pathway for their growth, what offers an opportunity to test oncogene-targeted therapy. Mutations at the position V600 of BRAF were described in approximately 8% of all solid tumors, including 50% of melanomas, 30 to 70% of papillary thyroid carcinomas and 5 to 8% of colorectal adenocarcinomas. Specific BRAF kinase inhibitors are undergoing rapid clinical development and promising data on efficacy have been demonstrated in activated mutant BRAF V600 melanomas. This review article will address: (a) preclinical data on the antitumor activity of BRAF inhibitors in cell lines/ in vivo models and their opposing functions as inhibitors or activators of the MAPK pathway, depending on the cellular context; (b) drug development from non-selective RAF inhibitors to selective BRAF inhibitors, such as PLX4032 and GSK2118436, with emphasis in the clinical efficacy and toxicity of these agents; and (c) possible mechanisms of resistance to BRAF inhibitors and strategies to overcome its development in BRAF mutant tumors.     

New treatment strategies and emerging drugs in endometriosis

Introduction: Endometriosis, histologically defined as the presence of endometrium-like tissue – glands and stroma – that develops outside of the uterine cavity, is still an enigmatic disease responsible for pelvic pain and infertility. The current treatments of endometriosis are surgery and hormonal therapies that act by suppressing ovulation and/or directly on steroid receptors located in endometriotic lesions.

Areas covered: New hormonal and non-hormonal therapies are being developed for the treatment of endometriosis-related pain. The authors review the state of advancement and the results of novel treatments studied in registered trials (www.ClinicalTrials.gov). Cellular signaling pathways activated in endometriotic cells, which constitute potential targets for future treatments, are also described.

Expert opinion: Therapeutic research efforts should focus on identifying and testing substances capable of acting locally on the lesions themselves, without interfering with ovulation, in order to be efficacious on both pain symptoms and infertility.     

A patent review of BRAF inhibitors: 2013-2018

Introduction: As a key element in arguably the most important pathway MAPK signaling, the BRAF kinase gives rise to severe diseases including cancers when pathologically activated. Extensive research on BRAFi (BRAF inhibitor) has been carried out to profile the characters for optimized agents and to elaborate the therapeutic strategies for the related cancer treatment.

Areas covered: This review gives an overview of recently approved BRAF agents on function mode, therapeutic efficacy, and deficiency, based on which current challenges and corresponding strategies were presented. New entities as BRAFi for medical purpose in patent literature during the period 2013–2018 were also briefly introduced.

Expert opinion: With the disclosure of paradox-breaker BRAFi PLX7904 crystal in complex with BRAF, the rational design for next-generation BRAFi is becoming ever more feasible. Accompanying therapeutic strategies in BRAFi elaboration may also provide flexible choice in the future ‘personal medicine’. Further digging in the greatly enriched BRAFi pool will greatly benefit the drug design processes such as FBDD- and SBDD-driven development.     

BRAF and MEK inhibition for the treatment of advanced BRAF mutant melanoma

Introduction: BRAF inhibition alone has achieved unprecedented efficacy results in patients affected by BRAF-mutated advanced melanoma. Since these findings, it was postulated that dual inhibition of BRAF and other components of the RAS/RAF/MEK/ERK MAPK pathway (such as MEK) would be superior to BRAF inhibition as monotherapy. A series of recent clinical trials have confirmed this hypothesis.

Areas covered: In this article, the biological rationale for both single and concomitant inhibitions of the MAPK pathway in BRAF mutant melanoma is provided. Moreover, available clinical data on the efficacy and toxicity of BRAF and MEK inhibition as single agents and in combination are extensively reviewed.

Expert opinion: Dual BRAF and MEK inhibition in advanced BRAF-mutated melanoma is superior to single inhibition in terms of efficacy without significant increase in toxicity. Therefore, BRAF plus MEK inhibition is expected to supersede single-agent BRAF inhibition in these patients in the near future.     

Histomorphometric alteration and cell-type specific modulation of arylhydrocarbon receptor and estrogen receptor expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin and 17beta-estradiol in mouse experimental model of endometriosis

Our purpose was to examine the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), either singly (10 μg/kg) or with 17β-estradiol (E₂, 100 μg/kg), on the growth of endometriosis in a mouse endometriosis model by employing histo-morphometrical analysis as well as expression of arylhydrocarbon receptor (AhR) and estrogen receptor (ER). Epithelial height, stromal thickness, and proliferative activity of the endometriotic lesions were significantly increased by E₂ in ovariectomized mice, whereas co-administered TCDD significantly reduced these effects. TCDD alone did not affect the proliferative activity but rather reduced the epithelial height and stromal thickness. ER expression in the luminal epithelium was decreased by E₂ compared with ovariectomy alone, while TCDD significantly increased it. On the other hand, stromal ER expression was significantly increased by ovariectomy and decreased by E₂, though TCDD did not further enhance this expression. These results indicate that a short-term exposure to TCDD failed to increase the growth of endometriotic lesion and the direct effect of TCDD probably depends on a cell-specific interaction with ovarian steroids mediated by their own receptors. These initial findings in intact tissue of mouse endometriosis may suggest critical roles of steroid hormones in the pathogenesis of endometriosis in relation to endocrine disruptors.     

子宫内膜异位症E-钙粘素的异常表达及意义

目的探讨E-钙粘素在子宫内膜异位症的异常表达及意义。方法应用免疫组织化学及图像分析方法比较E-钙粘素在正常子宫内膜、内膜异位症在位及异位内膜中的量。结果正常子宫内膜和内膜异位症在位内膜腺上皮E-钙粘素的表达无明显的周期性变化。在整个月经周期中,内膜异位症在位内膜腺上皮E-钙粘素的表达显著低于同期正常子宫内膜。卵巢子宫内膜异位囊肿中异位内膜腺上皮E-钙粘素的表达显著低于同组患者的在位内膜。结论子宫内膜异位症在位和异位内膜腺上皮E-钙粘素的表达降低与内膜异位症的发病密切相关。     

The discovery and development of cyclooxygenase-2 inhibitors as potential anticancer therapies

Introduction: In the past, clinical studies had demonstrated that aspirin and NSAIDs reduce the risk of colorectal cancer. After the discovery of selective prostaglandin-endoperoxide synthase 2 (PTGS2) inhibitors, the further beneficial effects of celecoxib and some other related structures (coxibs) have been demonstrated in both in vivo and in vitro studies.

Areas covered: The authors illustrate the role of prostaglandins following the overexpression of PTGS2 (COX-2) in signaling pathways. The authors elucidate the role of coxibs in cell proliferation, apoptosis, angiogenesis and multi-drug resistance and discuss the molecular mechanisms involved. The authors also present the strong evidence related to the usefulness of coxibs in several cancer cell lines.

Expert opinion: There have been a number of PTGS2 (COX-2) selective inhibitors suggested as potential anticancer therapies. In recent years, the development of nanotechnology has also had an impact on chemotherapy. Indeed, nanoparticles of cytotoxic drug carriers have demonstrated potential through their accumulation in cancer cells, and targeting these nanoparticles has been under evaluation. This area could be opened up for coxib development as they are potentially important targets in cancer cells. Further research using celecoxib as a co-drug with PTGS2-overexpressed and PTGS2-independent cancer is still needed.     

深部浸润型子宫内膜异位症手术方式对疼痛改善的影响

目的 评估深部浸润型子宫内膜异位症（DIE）患者腹腔镜下完全切除与未完全切除DIE病灶对疼痛改善的影响。方法 选择2013年4月至2015年4月安徽省肿瘤医院收治的45例DIE患者,经腹腔镜手术,完全切除病灶的患者纳入A组（26例）,未完全切除病灶的患者纳入B组（19例）,比较两组的手术时间、出血量、疼痛改善情况。结果 术后12个月,A组视觉模拟评分法（VAS）评分为（4.79±0.95）分,较术前明显降低,差异有统计学意义（P<0.05）;B组VAS评分为（9.82±1.59）分,与术前差异无统计学意义（P>0.05）;A组与B组VAS评分差异有统计学意义（P<0.05）。结论 DIE患者经手术完全切除病灶,疼痛症状明显改善。     

VEGF在不同部位子宫内膜异位症中的表达及意义

目的探讨血管内皮生长因子(VEGF)在不同部位子宫内膜异位症中的表达及意义。方法选择子宫内膜异位症组织标本40例为研究组(盆腔外特殊部位的子宫内膜异位症15例;卵巢子宫内膜异位症异位内膜25例,其中同期在位内膜20例);正常子宫内膜20例为对照组,应用免疫组化EnvisionTM二步法检测VEGF在不同部位子宫内膜异位中的表达,研究VEGF在子宫内膜异位症中的相关性以及与临床分期的关系。结果 VEGF阳性表达主要见于子宫内膜间质血管内皮细胞和腺上皮细胞的胞浆。(1)盆腔外异位病灶中VEGF表达高于卵巢异位内膜(P<0.05),与正常子宫内膜相比差异有极显著性(P<0.005);(2)卵巢异位内膜VEGF表达与同期在位内膜相比,表达增高,差异有显著性(P<0.05),且明显高于正常内膜(P<0.005);(3)在位内膜与正常子宫内膜相比,VEGF表达差异无显著性(P>0.05),在位内膜和正常内膜中增生期与分泌期VEGF表达无显著性差异(P>0.05)。VEGF的表达与子宫内膜异位症临床分期无明显相关性。结论盆腔外子宫内膜异位症、卵巢子宫内膜异位症的异位内膜中存在VEGF的高表达,可能导致了血管生成,利于种植及生长,可能成为内异症早期诊断的指标。     

Ketoconazole-induced JNK phosphorylation and subsequent cell death via apoptosis in human osteosarcoma cells

This study examined the effect of ketoconazole on viability, apoptosis, mitogen-activated protein kinases (MAPKs) and Ca²⁺ levels in MG63 osteosarcoma cells. Ketoconazole at 20–200 μM decreased cell viability via apoptosis as demonstrated by propidium iodide staining and activation of caspase-3. Immunoblotting suggested that ketoconazole induced phosphorylation of ERK and JNK, but not p38, MAPKs. Ketoconazole-induced cell death and apoptosis were partially reversed by the selective JNK inhibitor SP600125, but not by the selective ERK inhibitor PD98059, suggesting that ketoconazole’s cytotoxic action was via JNK, but not via ERK and p38 MAPKs. Ketoconazole at a concentration of 100 μM induced [Ca²⁺]_i increases. Chelation of intracellular Ca²⁺ with 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) totally inhibited ketoconazole-induced [Ca²⁺]_i increases without reversing ketoconazole-induced cell death. Collectively, in MG63 cells, ketoconazole induced cell death and apoptosis via evoking JNK phosphorylation in a Ca²⁺-independent manner.     

Quantification of a Pharmacodynamic ERK End Point in Melanoma Cell Lysates: Toward Personalized Precision Medicine

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Role of Dopamine D1 Receptors in the Activation of Nucleus Accumbens Extracellular Signal-Regulated Kinase (ERK) by Cocaine-Paired Contextual Cues

Exposure to drug-paired cues can trigger addicts to relapse into drug seeking. Although the molecular mechanisms underlying cue-elicited cocaine seeking are incompletely understood, the protein kinase extracellular signal-regulated kinase (ERK) is known to have an important role. Psychostimulants and their associated cues can activate ERK in medium spiny neurons of the nucleus accumbens core (AcbC). These medium spiny neurons can be classified according to their projections (to ventral pallidum and/or substantia nigra) and by their mRNA expression. The present experiments were designed to determine which distinct set of AcbC projection neurons expresses phosphorylated ERK (pERK) in response to cocaine-paired contextual cues. Combined use of the retrograde label Flurogold with immunohistochemical staining of pERK was used to show that the AcbC pERK accompanying preference for cocaine-paired contexts occurs in both the accumbens (Acb)-nigral and Acb-pallidal projections. The gene expression characteristics of the neurons expressing pERK in response to cocaine-paired cues was further investigated using combined in situ hybridization and immunocytochemistry to show that AcbC pERK+ cells correspond to D1, but not preproenkephalin, mRNA+ cells. Furthermore, intra-AcbC infusion of the D1-antagonist {"type":"entrez-protein","attrs":{"text":"SCH23390","term_id":"1052733334","term_text":"SCH23390"}}SCH23390 attenuated cue-induced AcbC pERK expression. In aggregate, these results indicate that (i) the D1-expressing AcbC neurons evidence long-term plasticity related to drug-cue memories and (ii) local dopamine D1 receptors are necessary for the expression of cocaine-paired cue-induced pERK in these AcbC neurons.     

Mitogen-activated protein kinases contribute to reactive oxygen species-induced cell death in renal proximal tubule epithelial cells

Extracellular signal-regulated kinases (ERK1/2), c-Jun N-terminal kinases (JNK/SAPK), and p38 mitogen-activated protein kinase (MAPK) were all rapidly activated in a ROS-dependent manner during 2,3,5-tris-(glutathion-S-yl)hydroquinone (TGHQ)-mediated oxidative stress and oncotic cell death in renal proximal tubule epithelial cells (LLC-PK1). TGHQ-induced phosphorylation of ERK1/2 and JNK MAPKs required epidermal growth factor receptor (EGFR) activation, whereas p38 MAPK activation was EGFR independent. In contrast to their established roles in cell survival, TGHQ-activated ERK1/2 and p38 MAPK (but not JNK) appear to contribute to cell death, since inhibition of ERK1/2 or p38 MAPKs with PD098059 or SB202190 respectively, attenuated TGHQ-mediated cell death. TGHQ increased AP-1 and NFkappaB DNA-binding activity, but whereas pharmacological inhibition of ERK1/2 or p38 MAPKs attenuated AP-1 DNA binding activity, it potentiated TGHQ-mediated NFkappaB activation. Consistent with a role for NFkappaB activation in the cytoprotective response to ROS in renal epithelial cells, an anti-NFkappaB peptide SN50 suppressed the protective effects of ERK inhibition (PD098059 treatment). The data provide evidence that the activation of MAPKs by ROS in renal epithelial cells plays an important role in oncotic cell death, and NF-kB is involved in the cytoprotective effects of PD098059.