CRAF inhibition induces apoptosis in melanoma cells with non-V600E BRAF mutations

Oncogene abnormalities in a series of primary melanomas of the sinonasal tract: NRAS mutations and cyclin D1 amplification are more frequent than KIT or BRAF mutations

Primary malignant melanoma of sinonasal tract is a rare but severe form of melanoma. We retrospectively analyzed 17 cases and focused on the histologic presentation and the expression of c-Kit, epidermal growth factor receptor (EGFR), cyclin D1/Bcl-1, PS100, and HMB45 and searched for BRAF, NRAS, and KIT mutations that are known to be associated with melanoma subtypes, together with amplifications of KIT, cyclin D1, cyclin-dependent kinase 4, MDM2, and microphthalmia-associated transcription factor using quantitative polymerase chain reaction. In most cases (78%), an in situ component was evidenced. Invasive components were composed of diffuse areas of rhabdoid, epithelioid, or spindle cells and, in most cases, lacked inflammatory reaction, suggesting that an immune escape phenomenon probably develops when the disease progresses. EGFR was rarely and weakly expressed in the in situ component of 2 cases. None of the investigated case showed BRAF V600E, but 1 had a D594G mutation. NRAS mutations in exon 2 (G12D or G12A) were found in 3 cases (18%), and a KIT mutation in exon 11 (L576P), in 1, whereas c-Kit was expressed at the protein level in half of the cases. Amplifications of cyclin D1 were evidenced in 5 cases, confirmed in 3 by fluorescence in situ hybridization, but this was not always correlated with protein expression, found in 8 patients (62.5%), 3 having no significant amplification. In conclusion, primary malignant melanoma of sinonasal tract is not associated with BRAF V600E mutations. Instead, NRAS or KIT mutations and cyclin D1 amplification can be found in a proportion of cases, suggesting that primary malignant melanoma of sinonasal tract is heterogeneous at the molecular level and should not be sensitive to therapeutic approaches aiming at BRAF.

Discovery of hybrid dual N-acylhydrazone and diaryl urea derivatives as potent antitumor agents: design, synthesis and cytotoxicity evaluation

Based on the hybrid pharmacophore design concept, a novel series of dual diaryl urea and N-acylhydrazone derivatives were synthesized and evaluated for their in vitro cytotoxicity by the standard MTT assay. The pharmacological results indicated that most compounds exhibited moderate to excellent activity. Moreover, compound 2g showed the most potent cytotoxicity against HL-60, A549 and MDA-MB-231 cell lines, with IC₅₀ values of 0.22, 0.34 and 0.41 μM, respectively, which was 3.8 to 22.5 times more active than the reference compounds sorafenib and PAC-1. The promising compound 2g thus emerges as a lead for further structural modifications.

Elucidating distinct roles for NF1 in melanomagenesis

BRAF mutations play a well-established role in melanomagenesis; however, without additional genetic alterations, tumor development is restricted by oncogene-induced senescence (OIS). Here, we show that mutations in the NF1 tumor suppressor gene cooperate with BRAF mutations in melanomagenesis by preventing OIS. In a genetically engineered mouse model, Nf1 mutations suppress Braf-induced senescence, promote melanocyte hyperproliferation, and enhance melanoma development. Nf1 mutations function by deregulating both phosphoinositide 3-kinase and extracellular signal-regulated kinase pathways. As such, Nf1/Braf-mutant tumors are resistant to BRAF inhibitors but are sensitive to combined inhibition of mitogen-activated protein/extracellular signal-regulated kinase kinase and mTOR. Importantly, NF1 is mutated or suppressed in human melanomas that harbor concurrent BRAF mutations, NF1 ablation decreases the sensitivity of melanoma cell lines to BRAF inhibitors, and NF1 is lost in tumors from patients following treatment with these agents. Collectively, these studies provide mechanistic insight into how NF1 cooperates with BRAF mutations in melanoma and show that NF1/neurofibromin inactivation may have an impact on responses to targeted therapies.

Immunohistochemistry with a mutation-specific monoclonal antibody as a screening tool for the BRAFV600E mutational status in primary cutaneous malignant melanoma

The V600E mutation of BRAF has emerged as both an effective biomarker and therapeutic target for select benign and malignant cutaneous and non-cutaneous human tumors and is typically determined using DNA-based techniques that include allele-specific PCR and direct DNA sequencing. Recently however, the development of new antibodies directed against the V600E protein has opened the door for an easier and more efficient strategy for identifying this mutation. Our present aim was to determine the efficacy of one such antibody, anti-B-Raf (V600E), a mouse monoclonal antibody in which the immunogen is a synthetic peptide derived from the internal region of BRAFV600E. A total of 35 cases of primary cutaneous melanoma were evaluated using a combination of DNA-based techniques that included allele-specific PCR and/or direct DNA sequencing and immunohistochemistry. Cases of papillary thyroid carcinomas (n=5) and colorectal carcinomas (n=5), known to harbor the BRAFV600E mutation, served as positive controls for the study. DNA analyses revealed that 6 of 35 (17%) cases of the primary cutaneous malignant melanoma possessed the BRAFV600E mutation. For immunohistochemical analyses, cytoplasmic positivity with anti-B-Raf was noted in 7 of 35 (20%) cases of primary melanoma and in all 10 positive controls. Statistical analyses of the data demonstrated that the sensitivity of the immunohistochemistry was 100% and specificity was 97%. Findings from the current study support the potential use of immunohistochemistry as an ancillary screening tool to assess the BRAFV600E mutation status in primary cutaneous melanoma.

Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascade inhibitors: how mutations can result in therapy resistance and how to overcome resistance

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Targeting these pathways is often complex and can result in pathway activation depending on the presence of upstream mutations (e.g., Raf inhibitors induce Raf activation in cells with wild type (WT) RAF in the presence of mutant, activated RAS) and rapamycin can induce Akt activation. Targeting with inhibitors directed at two constituents of the same pathway or two different signaling pathways may be a more effective approach. This review will first evaluate potential uses of Raf, MEK, PI3K, Akt and mTOR inhibitors that have been investigated in pre-clinical and clinical investigations and then discuss how cancers can become insensitive to various inhibitors and potential strategies to overcome this resistance.

Use of Nanotechnology to Develop Multi-Drug Inhibitors For Cancer Therapy

Therapeutic agents that inhibit a single target often cannot combat a multifactorial disease such as cancer. Thus, multi-target inhibitors (MTIs) are needed to circumvent complications such as the development of resistance. There are two predominant types of MTIs, (a) single drug inhibitor (SDIs) that affect multiple pathways simultaneously, and (b) combinatorial agents or multi-drug inhibitors (MDIs) that inhibit multiple pathways. Single agent multi-target kinase inhibitors are amongst the most prominent class of compounds belonging to the former, whereas the latter includes many different classes of combinatorial agents that have been used to achieve synergistic efficacy against cancer. Safe delivery and accumulation at the tumor site is of paramount importance for MTIs because inhibition of multiple key signaling pathways has the potential to lead to systemic toxicity. For this reason, the development of drug delivery mechanisms using nanotechnology is preferable in order to ensure that the MDIs accumulate in the tumor vasculature, thereby increasing efficacy and minimizing off-target and systemic side effects. This review will discuss how nanotechnology can be used for the development of MTIs for cancer therapy and also it concludes with a discussion of the future of nanoparticle-based MTIs as well as the continuing obstacles being faced during the development of these unique agents.’

Emerging molecular targets in melanoma invasion and metastasis

Metastatic cutaneous melanoma accounts for the majority of skin cancer deaths due to its aggressiveness and high resistance to current therapies. To efficiently metastasize, invasive melanoma cells need to change their cytoskeletal organization and alter contacts with the extracellular matrix and the surrounding stromal cells. Melanoma cells can use different migratory strategies depending on varying environments to exit the primary tumour mass and invade surrounding and later distant tissues. In this review, we have focused on tumour cell plasticity or the interconvertibility that melanoma cells have as one of the factors that contribute to melanoma metastasis. This has been an area of very intense research in the last 5 yr yielding a vast number of findings. We have therefore reviewed all the possible clinical opportunities that this new knowledge offers to both stratify and treat cutaneous malignant melanoma patients.

The histogenic origin of melanoma arising in respiratory epithelium of a teratomatous germ cell tumor of the mediastinum: an enigma unraveled from an unlikely source

Mixed germ cell tumors are rare neoplasms that are known to occur in the anterior mediastinum. Characterized by two or more types of germ cell components, these tumors comprise upwards of 25% of mediastinal germ cell tumors. Even rarer are those harboring somatic-type malignancies such as carcinoma, sarcoma, and hematopoietic malignancies. To date, however, there are no known cases of melanoma arising in a malignant mixed germ cell tumor of the anterior mediastinum. We describe the first case of malignant melanoma with spindle and epithelioid components arising from respiratory epithelium in a mediastinal malignant mixed germ cell tumor of a 32-year-old male. In addition, we also provide evidence supporting the theory of neuroendocrine cells as the origin of melanoma arising in the respiratory epithelium. This case emphasizes the need to carefully evaluate all germ cell tumors, not only for a myriad of benign embryological components, but also for malignancies arising in these components, as they might change the prognosis and patient's course of treatment. This microscopic approach should bring to light the diversity of mixed germ cell tumors in addition to somatic malignancies with corresponding biologic potentials.

NRAS mutant melanoma: biological behavior and future strategies for therapeutic management

The recent years have seen a significant shift in the expectations for the therapeutic management of disseminated melanoma. The clinical success of BRAF targeted therapy suggests that long-term disease control may one day be a reality for genetically defined subgroups of melanoma patients. Despite this progress, few advances have been made in developing targeted therapeutic strategies for the 50% of patients whose melanomas are BRAF wild-type. The most well-characterized subgroup of BRAF wild-type tumors is the 15-20% of all melanomas that harbor activating NRAS (Neuroblastoma Rat Sarcoma Virus) mutations. Emerging preclinical and clinical evidence suggests that NRAS mutant melanomas have patterns of signal transduction and biological behavior that is distinct from BRAF mutant melanomas. This overview will discuss the unique clinical and prognostic behavior of NRAS mutant melanoma and will summarize the emerging data on how NRAS-driven signaling networks can be translated into novel therapeutic strategies.

MEK and RAF inhibitors for BRAF-mutated cancers

The mitogen-activated protein kinase (MAPK) pathway has been implicated in the pathophysiology of many cancers. Under normal physiologic conditions, the RAS-RAF-mitogen-activated protein kinase kinase (MEK)-mitogen-activated protein kinase (ERK) signalling cascade interaction is initiated by ligation of a receptor-linked tyrosine kinase by its cognate growth factor. It has been demonstrated in many systems that aberrant autocrine or paracrine stimulation of growth factor receptors is pathogenic in large part because of MAPK activation. As one of the key downstream effector pathways of mutated RAS (KRAS, NRAS and HRAS), pharmacologic inhibition of components of the MAPK pathway has been pursued as a means to indirectly inhibit RAS, which remains a technical challenge for direct pharmacologic inhibition. RAF and MEK are the two non-membrane-bound, serine-threonine and tyrosine-threonine kinases, within the pathway that have been most extensively explored as drug targets. The discovery of activating BRAF mutations in cancer clarified which cancer types and subsets of certain cancers are most dependent on activation of the MAPK pathway for growth and survival. Now, with the successful translation of selective BRAF and MEK inhibitors into validated therapies for BRAF mutant melanoma, the field seeks to resolve the role for these agents in cancers harbouring RAS mutations or those driven by aberrant growth factor receptor activation.

Kinase-impaired BRAF mutations in lung cancer confer sensitivity to dasatinib

During a clinical trial of the tyrosine kinase inhibitor dasatinib for advanced non-small cell lung cancer (NSCLC), one patient responded dramatically and remains cancer-free 4 years later. A comprehensive analysis of his tumor revealed a previously undescribed, kinase-inactivating BRAF mutation ((Y472C)BRAF); no inactivating BRAF mutations were found in the nonresponding tumors taken from other patients. Cells transfected with (Y472C)BRAF exhibited CRAF, MEK (mitogen-activated or extracellular signal-regulated protein kinase kinase), and ERK (extracellular signal-regulated kinase) activation-characteristics identical to signaling changes that occur with previously known kinase-inactivating BRAF mutants. Dasatinib selectively induced senescence in NSCLC cells with inactivating BRAF mutations. Transfection of other NSCLC cells with these BRAF mutations also increased these cells' dasatinib sensitivity, whereas transfection with an activating BRAF mutation led to their increased dasatinib resistance. The sensitivity induced by (Y472C)BRAF was reversed by the introduction of a BRAF mutation that impairs RAF dimerization. Dasatinib inhibited CRAF modestly, but concurrently induced RAF dimerization, resulting in ERK activation in NSCLC cells with kinase-inactivating BRAF mutations. The sensitivity of NSCLC with kinase-impaired BRAF to dasatinib suggested synthetic lethality of BRAF and an unknown dasatinib target. Inhibiting BRAF in NSCLC cells expressing wild-type BRAF likewise enhanced these cells' dasatinib sensitivity. Thus, the patient's BRAF mutation was likely responsible for his tumor's marked response to dasatinib, suggesting that tumors bearing kinase-impaired BRAF mutations may be exquisitely sensitive to dasatinib. Moreover, the potential synthetic lethality of combination therapy including dasatinib and BRAF inhibitors may lead to additional therapeutic options against cancers with wild-type BRAF.

Thyroid carcinoma-associated genetic mutations also occur in thyroid lymphomas

Molecular testing for mutations activating the mitogen-associated protein kinase signaling pathway is being used to help diagnose thyroid carcinomas. However, the prevalence of these mutations in thyroid lymphomas has not been reported. Therefore, we studied the prevalence of BRAF, NRAS, HRAS, and KRAS mutations in 33 thyroid lymphomas and correlated the mutational status with the clinical, pathological, cytogenetic, and immunophenotypic findings. Eleven cases were also tested for PAX8/PPARγ translocations. The lymphomas included 25 diffuse large B-cell lymphomas, 6 extranodal marginal-zone lymphomas of mucosa-associated lymphoid tissue type, and 2 follicular lymphomas. Seventeen diffuse large B-cell lymphomas were germinal center type, six non-germinal center type, and two unclassifiable (Hans algorithm). None of the cases had an associated thyroid carcinoma. Mutations of the BRAF gene were identified in six (24%) diffuse large B-cell lymphomas (D594G in three germinal center diffuse large B-cell lymphomas, K601N in two germinal center diffuse large B-cell lymphomas, and V600E in one non-germinal center diffuse large B-cell lymphoma) and of the NRAS gene in two (8%) non-germinal center diffuse large B-cell lymphomas (Q61K and Q61H). BRAF and NRAS mutations were not found in any extranodal marginal-zone lymphomas of mucosa-associated lymphoid tissue type or follicular lymphomas. HRAS and KRAS mutations were not identified in any of the cases, nor were PAX8/PPARγ translocations found. Thus, interpretation of finding a BRAF or NRAS mutation in the thyroid, particularly in preoperative thyroid aspirates, must take into account the differential diagnosis of a lymphoma. In addition to the diagnostic importance, our data also demonstrate that alteration in the mitogen-associated protein kinase pathway may have a role in the pathogenesis of some large B-cell lymphomas of the thyroid with potential therapeutic implications.

The current state of targeted therapy in melanoma: this time it's personal

Treatment of metastatic melanoma has long been a challenge. Over the past 8 years significant advances have been made in understanding the genetic changes that drive melanoma development and progression. These studies have shown melanoma to be a heterogeneous group of tumors, driven by a diverse array of oncogenic mutations. There is now good evidence that activating mutations in the serine/threonine kinase BRAF and the receptor tyrosine kinase KIT constitute good therapeutic targets for restricted subgroups of melanoma. In this article, we discuss the genetics and etiology of cutaneous and noncutaneous melanoma and review some of the latest preclinical and clinical data on the new targeted therapy agents that are beginning to make an impact on the lives of melanoma patients.

BRAF inhibitors and melanoma

Selective BRAF inhibitors have recently emerged as a new standard treatment for patients with metastatic melanoma harboring activating BRAF mutations. Inhibition of the MAP kinase pathway and initial evidence of antitumor effects are very reliably observed. However, many patients experience short-lived responses, whereas others are durable. An overall survival benefit has been established for them, BRAF in it, the agents that have advanced furthest in clinical development. Nonetheless, attention has immediately turned to understanding de novo and acquired resistance and effort to develop rational combination therapy that will further improve patient outcomes. Opportunities for combining BRAF inhibitors with other signal transduction inhibitors as well as targeted therapies with distinct mechanisms of action are discussed.

From genes to drugs: targeted strategies for melanoma

The past decade has revealed that melanoma is comprised of multiple subclasses that can be categorized on the basis of key features, including the clinical stage of disease, the oncogenic molecular 'drivers', the anatomical location or the behaviour of the primary lesion and the expression of specific biomarkers. Although exercises in subclassification are not new in oncology, progress in this area has produced both conceptual and clinical breakthroughs, which, for melanoma, are unprecedented in the modern history of the disease. This Review focuses on these recent striking advances in the strategy of molecularly targeted approaches to the therapy of melanoma in humans.

Targeting mutant BRAF in melanoma: current status and future development of combination therapy strategies

The discovery of activating BRAF mutations in ∼50% of all melanomas has proved to be a turning point in the therapeutic management of the disseminated disease. In this commentary, we review the latest research delineating the role of mutant BRAF in melanoma initiation and progression and discuss the remarkable 10-year journey leading up to the recent U.S. Food and Drug Administration approval of the small-molecule BRAF inhibitor vemurafenib. We further outline the most recent findings on the mechanisms that underlie intrinsic and acquired BRAF inhibitor resistance and describe ongoing preclinical and clinical studies designed to delay or abrogate the onset of therapeutic escape. It is hoped that our evolving understanding of melanoma genetics and intracellular signaling coupled with a growing armamentarium of signal transduction inhibitors will lead to significant improvements in the level and durability of therapeutic response in metastatic melanoma.

Design, synthesis and biological evaluation of novel (E)-α-benzylsulfonyl chalcone derivatives as potential BRAF inhibitors

Activating mutations in the BRAF serine/threonine kinase are found in more than 70% of human melanomas, >90% of which are BRAF(V600E). It provides new therapeutic opportunities in malignant melanoma. In silico and in vitro screening of our compound collection has identified Hit 2 as BRAF(V600E) inhibitor. Based on its structure, a series of novel (E)-α-benzylsulfonyl chalcone derivatives (13-40) were designed and synthesized. Compound 38 exhibited the most potent inhibitory activity with an IC(50) value of 0.17 μM for BRAF(V600E) and GI(50) value of 0.52 μM for mutant BRAF-dependent cells. The results of cell based pERK activity and cellular selectivity suggested that those compounds could selectively inhibit proliferation of mutant BRAF-dependent melanoma cell line through inhibition of oncogenic BRAF.

New therapeutic targets in melanoma

Research into molecular targets for drug development in melanoma is starting to bear fruit. Of the drugs tested to date in patients with metastatic melanoma, those that have yielded the best results are V600E BRAF inhibitors in melanomas carrying the V600E mutation; c-kit tyrosine kinase activity inhibitors in melanomas carrying c-kit mutations; and anti-cytotoxic T lymphocyte antigen 4 (CTLA-4) antibodies, which block the mechanisms involved in immune tolerance. Many problems have yet to be resolved in these areas, however, such as the rapid development of resistance to BRAF and c-kit inhibitors and the lack of biomarkers to predict treatment response in the case of CTLA-4 blockers. We review the results of targeted therapy with these and other drugs in metastatic melanoma and discuss what the future holds for this field.

Targeting the RAS pathway in melanoma

Metastatic melanoma is a highly lethal type of skin cancer and is often refractory to all traditional chemotherapeutic agents. Key insights into the genetic makeup of melanoma tumors have led to the development of promising targeted agents. An activated RAS pathway, anchored by oncogenic BRAF, appears to be the central motor driving melanoma proliferation. Although recent clinical trials have brought enormous hope to patients with melanoma, adverse effects and novel escape mechanisms of these inhibitors have already emerged. Definition of the limits of the first successful targeted therapies will provide the basis for further advances in management of disseminated melanoma. In this review, the current state of targeted therapy for melanoma is discussed, including the potent BRAF(V600E) inhibitor vemurafenib.

High-throughput detection of actionable genomic alterations in clinical tumor samples by targeted, massively parallel sequencing

Knowledge of "actionable" somatic genomic alterations present in each tumor (e.g., point mutations, small insertions/deletions, and copy-number alterations that direct therapeutic options) should facilitate individualized approaches to cancer treatment. However, clinical implementation of systematic genomic profiling has rarely been achieved beyond limited numbers of oncogene point mutations. To address this challenge, we utilized a targeted, massively parallel sequencing approach to detect tumor genomic alterations in formalin-fixed, paraffin-embedded (FFPE) tumor samples. Nearly 400-fold mean sequence coverage was achieved, and single-nucleotide sequence variants, small insertions/deletions, and chromosomal copynumber alterations were detected simultaneously with high accuracy compared with other methods in clinical use. Putatively actionable genomic alterations, including those that predict sensitivity or resistance to established and experimental therapies, were detected in each tumor sample tested. Thus, targeted deep sequencing of clinical tumor material may enable mutation-driven clinical trials and, ultimately, "personalized" cancer treatment.

SIGNIFICANCE

Despite the rapid proliferation of targeted therapeutic agents, systematic methods to profile clinically relevant tumor genomic alterations remain underdeveloped. We describe a sequencingbased approach to identifying genomic alterations in FFPE tumor samples. These studies affirm the feasibility and clinical utility of targeted sequencing in the oncology arena and provide a foundation for genomics-based stratification of cancer patients.

Mechanism of RAF isoform switching induced by oncogenic RAS in melanoma

BRAF and RAS are often mutated in cutaneous melanoma and both mutations stimulate the MAPK pathway. However the biological consequences of BRAF and NRAS mutations are different because when RAS is mutated in melanoma, cells use CRAF rather than BRAF to activate MEK/ERK. The mechanism of this BRAF to CRAF isoform switching in response to oncogenic RAS has recently been described. Activation of the MAPK pathway, which results from a mutation of NRAS, induces phosphorylation of BRAF on serine 151 by ERK which prevents its binding to NRAS. To circumvent this negative feedback inhibition of BRAF, melanoma cells containing a mutation of RAS use CRAF to activate MEK/ERK. However, because the cAMP pathway in melanocytes constitutively inhibits CRAF, RAF isoform switching in melanoma is accompanied by an inhibition of the cAMP pathway. This inhibition is due to an increase in phosphodiesterase activity, which degrades cAMP thereby preventing inhibition of CRAF by PKA. These data highlight the importance of CRAF downstream of oncogenic Ras in tumor development.

RNA interference against SPARC promotes the growth of U-87MG human malignant glioma cells

Malignant glioma is a highly invasive brain tumor resistant to conventional therapies. Secreted protein acidic and rich in cysteine (SPARC) has been shown to facilitate glioma invasion. However, the effects of SPARC on cell growth have yet to be adequately elucidated. In this study, we constructed a plasmid expressing shRNA against SPARC, evaluated the effect of SPARCshRNA on SPARC expression and then assessed its effect on cell growth in U-87MG cells. Using plasmid-delivered shRNA, we effectively suppressed SPARC expression in U-87MG cells. Cell growth curves and colony formation assay suggested that the introduction of SPARCshRNA resulted in an increase of cell growth and colony formation. We also showed that knockdown of SPARC expression was capable of promoting the cell cycle progression from the G1 to S phase. However, no difference was found in the level of apoptosis. A molecular analysis of signal mediators indicated that the inhibition of p-c-Raf (Ser259) and accumulation of p-GSK-3β (Ser9) and p-AKT (Ser473) may be connected with the growth promotion by SPARC shRNA. Our study may provide an insight into the biological function of SPARC in glioma.

Acquired and intrinsic BRAF inhibitor resistance in BRAF V600E mutant melanoma

The discovery of activating BRAF V600E mutations in 50% of all cutaneous melanomas has revolutionized the understanding of melanoma biology and provided new strategies for the therapeutic management of this deadly disease. Highly potent small molecule inhibitors of BRAF are now showing great promise as a novel therapeutic strategy for melanomas harboring activating BRAF V600E mutations and are associated with high levels of response. This commentary article discusses the latest data on the role of mutated BRAF in the development and progression of melanoma as the basis for understanding the mechanism of action of BRAF inhibitors in the preclinical and clinical settings. We further address the issue of BRAF inhibitor resistance and outline the latest insights into the mechanisms of therapeutic escape as well as describing approaches to prevent and abrogate the onset of both intrinsic and acquired drug resistance. It is likely that our evolving understanding of melanoma genetics and signaling will allow for the further personalization of melanoma therapy with the goal of improving clinical responses.

BRAF targeted therapy changes the treatment paradigm in melanoma

After decades of stagnation, recent therapeutic advances in melanoma seem on the horizon. The discovery of the genetic underpinnings of this historically refractory disease has exposed potential targets for therapy, BRAF mutations being principal among them. In the 8 years following the discovery of BRAF mutations in 50-60% of advanced melanomas, only recently have potent and selective inhibitors of this intracellular signaling molecule shown efficacy from early clinical testing. Vemurafenib (PLX4032) and GSK2118436, two orally available and well tolerated agents are on the verge of transforming the landscape of melanoma therapy based on the promising results of their respective phase I, II, and III trials.

Clinical characteristics of patients with lung adenocarcinomas harboring BRAF mutations

PURPOSE

BRAF mutations occur in non-small-cell lung cancer. Therapies targeting BRAF mutant tumors have recently been identified. We undertook this study to determine the clinical characteristics of patients with lung adenocarcinomas harboring BRAF mutations.

PATIENTS AND METHODS

We reviewed data from consecutive patients with lung adenocarcinoma whose tumors underwent BRAF, EGFR, and KRAS mutation testing as well as fluorescence in situ hybridization for ALK rearrangements. Patient characteristics including age, sex, race, performance status, smoking history, stage, treatment history, and overall survival were collected.

RESULTS

Among 697 patients with lung adenocarcinoma, BRAF mutations were present in 18 patients (3%; 95% CI, 2% to 4%). The BRAF mutations identified were V600E (50%), G469A (39%), and D594G (11%). Mutations in EGFR were present in 24%, KRAS in 25%, and ALK translocations in 6%. In contrast to patients with EGFR mutations and ALK rearrangements who were mostly never smokers, all patients with BRAF mutations were current or former smokers (P < .001). The median overall survival of advanced-stage patients with BRAF mutations was not reached. In comparison, the median overall survival of patients with EGFR mutations was 37 months (P = .73), with KRAS mutations was 18 months (P = .12), and with ALK rearrangements was not reached (P = .64).

CONCLUSION

BRAF mutations occur in 3% of patients with lung adenocarcinoma and occur more commonly in current and former smokers. The incidence of BRAF mutations other than V600E is significantly higher in lung cancer than in melanoma.

Targeted molecular therapy in melanoma

Immunotherapy and chemotherapy benefit few patients with metastatic melanoma, and even fewer experience durable survival benefit. These poor results may come from treating all melanomas as though they are biologically homogeneous. Recently, it has been shown that targeting specific activated tyrosine kinases (oncogenes) can have striking clinical benefits in patients with melanoma. In 2002, a V600E mutation of the BRAF serine/threonine kinase was described as present in more than 50% of all melanomas. The mutation appeared to confer a dependency by the melanoma cancer cell on activated signaling through mitogen-activated protein kinase pathway. The frequency and focality of this mutation (>95% of all BRAF mutations being at V600 position) suggested its importance in melanoma pathophysiology and potential as a target for therapy. The recent results of a phase 1 study with PLX4032/RG7204, a small molecule RAF inhibitor, confirm this hypothesis. Mucosal and acral-lentiginous melanomas, comprising 3% of all melanomas, frequently harbor activating mutations of c-kit and drugs targeting this mutation seem to confer similar benefits for these types of tumors. Here we provide an overview of the targeted therapy development in melanoma with emphasis on BRAF inhibition because of its prevalence and possibility of transforming the care of many melanoma patients.

Molecular nevogenesis

Despite recent advances, the biology underlying nevogenesis remains unclear. Activating mutations in NRAS, HRAS, BRAF, and GNAQ have been identified in benign nevi. Their presence roughly correlates with congenital, Spitz, acquired, and blue nevi, respectively. These mutations are likely to play a critical role in driving nevogenesis. While each mutation is able to activate the MAP kinase pathway, they also interact with a host of different proteins in other pathways. The different melanocytic developmental pathways activated by each mutation cause the cells to migrate, proliferate, and differentiate to different extents within the skin. This causes each mutation to give rise to a characteristic growth pattern. The exact location and differentiation state of the cell of origin for benign moles remains to be discovered. Further research is necessary to fully understand nevus development given that most of the same developmental pathways are also present in melanoma.

Treatment implications of the emerging molecular classification system for melanoma

Melanoma is an aggressive disease with few standard treatment options. The conventional classification system for this disease is based on histological growth patterns, with division into four subtypes: superficial spreading, lentigo maligna, nodular, and acral lentiginous. Major limitations of this classification system are absence of prognostic importance and little correlation with treatment outcomes. Recent preclinical and clinical findings support the notion that melanoma is not one malignant disorder but rather a family of distinct molecular diseases. Incorporation of genetic signatures into the conventional histopathological classification of melanoma has great implications for development of new and effective treatments. Genes of the mitogen-associated protein kinase (MAPK) pathway harbour alterations sometimes identified in people with melanoma. The mutation Val600Glu in the BRAF oncogene (designated BRAF(V600E)) has been associated with sensitivity in vitro and in vivo to agents that inhibit BRAF(V600E) or MEK (a kinase in the MAPK pathway). Melanomas arising from mucosal, acral, chronically sun-damaged surfaces sometimes have oncogenic mutations in KIT, against which several inhibitors have shown clinical efficacy. Some uveal melanomas have activating mutations in GNAQ and GNA11, rendering them potentially susceptible to MEK inhibition. These findings suggest that prospective genotyping of patients with melanoma should be used increasingly as we work to develop new and effective treatments for this disease.

Molecular targeted therapy for patients with melanoma: the promise of MAPK pathway inhibition and beyond

IMPORTANCE OF THE FIELD

Recent discoveries have expanded the understanding of the molecular signaling events critical to melanomagenesis and led to the development of targeted therapeutic agents that are revolutionizing the treatment of patients with advanced melanoma.

AREAS COVERED IN THIS REVIEW

This article reviews current therapy and its limitations, describes the key pathogenic mechanisms in melanoma for which inhibitors have been tested, and summarizes the results of clinical trials involving molecularly targeted agents in this disease.

WHAT THE READER WILL GAIN

There has been an explosion of preclinical and clinical research aimed at targeting the key molecular alterations in melanoma for therapeutic benefit. These findings will be presented and placed in the proper clinical context, affording information regarding the current molecular targets in the melanoma and the activity and limitations of therapeutic agents directed against them.

TAKE HOME MESSAGE

Greater understanding of the pathogenic mechanisms underlying melanoma development has prompted the development of new therapeutic approaches aimed at counteracting these processes. While progress made over the past few years has generated considerable excitement, the benefits of these new therapies are still limited by incomplete and transient tumor regressions. It is hoped that with further investigation, particularly into mechanisms of treatment de novo and acquired treatment resistance, these limitations can be overcome.

Targeted therapy for melanoma: a primer

Melanoma is the most aggressive form of skin cancer. Unfortunately, despite recent improvements for some solid tumors, the prevalence and mortality of melanoma continue to increase. The identification of activating mutations in melanoma, combined with a growing appreciation of the different pattern of genetic changes in the anatomically defined melanoma subtypes, has become the focus of a concerted effort to translate these discoveries into personalized therapeutic approaches for this disease. This article reviews the known mutations, amplifications, and deletions in kinase signaling pathways that have been implicated in melanoma; the prevalence of these genetic events in clinicopathologically defined melanoma subtypes; and the results of clinical trials that use targeted therapy approaches to block aberrantly activated pathways resulting from these mutations. The challenges that must be overcome to achieve improved outcomes with targeted therapies in melanoma in the future are also discussed.

Acquired resistance to BRAF inhibitors mediated by a RAF kinase switch in melanoma can be overcome by cotargeting MEK and IGF-1R/PI3K

BRAF is an attractive target for melanoma drug development. However, resistance to BRAF inhibitors is a significant clinical challenge. We describe a model of resistance to BRAF inhibitors developed by chronic treatment of BRAF(V)⁶⁰⁰(E) melanoma cells with the BRAF inhibitor SB-590885; these cells are cross-resistant to other BRAF-selective inhibitors. Resistance involves flexible switching among the three RAF isoforms, underscoring the ability of melanoma cells to adapt to pharmacological challenges. IGF-1R/PI3K signaling was enhanced in resistant melanomas, and combined treatment with IGF-1R/PI3K and MEK inhibitors induced death of BRAF inhibitor-resistant cells. Increased IGF-1R and pAKT levels in a post-relapse human tumor sample are consistent with a role for IGF-1R/PI3K-dependent survival in the development of resistance to BRAF inhibitors.

BRAF, a target in melanoma: implications for solid tumor drug development

The successful translation of therapies targeting signal-transduction pathways that are activated by oncogenes has provided a model for molecularly targeted therapy, and the identification of mutations in v-raf murine sarcoma viral oncogene homolog B1 (BRAF), a serine/threonine kinase, has turned the attention of the melanoma field toward this concept. The current review indicated that BRAF represents an important target in cancer, in part because it is present in 7% of all cancers and also because it represents the first intracellular signaling molecule that is activated by point mutations for which single-agent therapy appears to have efficacy. Therapy for advanced melanoma has progressed slowly over the past 3 decades, although significant advances have been made in other cancers with the application of cytotoxic chemotherapy and targeted therapies. However, in melanoma, cytotoxic chemotherapies have severe limits, chemotherapy does not convincingly improve on the natural history of metastatic disease and has no role in the adjuvant setting, and cytokine therapy may have a niche in both the adjuvant and metastatic settings but confers only a modest benefit to a small proportion of patients at the cost of severe toxicity. Thus, there are few other cancers in which completely novel therapies are so highly prioritized in clinical research. Understanding network of signal-transduction pathways and how that network may adapt to BRAF inhibition or mitogen-activated protein kinase kinase inhibition will point to the next generation of clinical trials investigating rational combination regimens. The current investigations in melanoma will create a set of hypotheses to be tested in each cancer that harbors BRAF mutations.

[Current status of Akt in non-small cell lung cancer]

Lung cancer is one of the most common malignant tumors in the world, but its pathogenesis has still been remaining confusing. As an important protein in several signaling pathways, Akt has been identified to play a major role in the growth, proliferation, apoptosis and invasion of tumor cells. This paper is to review the effects of Akt, together with PDK1, Raf-1 and p70S6K, which are upstream and downstream regulatory molecules of Akt, and provide a new basis for the pathogenesis of non-small cell lung cancer.

A new era: melanoma genetics and therapeutics

We have recently witnessed an explosion in our understanding of melanoma. Knowledge of the molecular basis of melanoma and the successes of targeted therapies have pushed melanoma care to the precipice of a new era. Identification of significant pathways and oncogenes has translated to the development of targeted therapies, some of which have produced major clinical responses. In this review, we provide an overview of selected key pathways and melanoma oncogenes as well as the targeted agents and therapeutic approaches whose successes suggest the promise of a new era in melanoma and cancer therapy. Despite these advances, the conversion of transient remissions to stable cures remains a vital challenge. Continued progress towards a better understanding about the complexity and redundancy responsible for melanoma progression may provide direction for anti-cancer drug development.

Analysis of the genome to personalize therapy for melanoma

The treatment of cancer is being revolutionized by an improved understanding of the genetic events that occur in tumors. Advances in the understanding of the prevalence and patterns of mutations in melanoma have recently led to impressive results in trials of personalized, targeted therapies for this disease. In this review, we will discuss the molecular targets that have been validated clinically, additional genetic events that are candidates for future trials, and the challenges that remain to improve outcomes further in this aggressive disease.

[What is new in oncodermatology?]

News in the oncodermatology field this year were dominated by publications treating of melanoma and concerning in particular our increased knowledge of the various biological pathways involved in the distinct subtypes of melanoma. This molecular diversity is probably one of the reasons explaining the poor results of most of the clinical trials recently published because we don't know yet how to identify and select the right population of patients who could beneficiate from such or such therapy. However, some very encouraging results obtained with new protocols for adoptive immunotherapy have been published and we also hope that further results will confirm that the subset of KIT-mutated melanomas will beneficiate from an efficient targeted anti-Kit therapy. Besides melanoma, the scoop of the year was the discovery of a defective oncogenic polyomavirus which is very likely to be responsible for Merkel cell carcinoma.

B-RAF inhibitors: an evolving role in the therapy of malignant melanoma

Immunotherapy and chemotherapy benefit few patients with metastatic melanoma, and even fewer experience durable survival benefit. These poor results come from treating melanoma as a single homogeneous disease. Recently, it has been shown that targeting activated tyrosine kinases (oncogenes) can mediate striking clinical benefits in several cancers. In 2002, a mutation at the V600E amino acid of the BRAF serine/threonine kinase was described as present in over 50% of melanomas. The mutation appeared to confer a dependency by the melanoma cancer cell on its activation of the MAP kinase pathway. The frequency and specificity of this mutation (95% at V600E of BRAF) suggests that it may be a potential target for therapy, and recent results with one inhibitor, PLX4032/RG7204, bare this out. This review updates the status of BRAF inhibitors in melanoma and what may be on the horizon.

Effects of KRAS, BRAF, NRAS, and PIK3CA mutations on the efficacy of cetuximab plus chemotherapy in chemotherapy-refractory metastatic colorectal cancer: a retrospective consortium analysis

BACKGROUND

Following the discovery that mutant KRAS is associated with resistance to anti-epidermal growth factor receptor (EGFR) antibodies, the tumours of patients with metastatic colorectal cancer are now profiled for seven KRAS mutations before receiving cetuximab or panitumumab. However, most patients with KRAS wild-type tumours still do not respond. We studied the effect of other downstream mutations on the efficacy of cetuximab in, to our knowledge, the largest cohort to date of patients with chemotherapy-refractory metastatic colorectal cancer treated with cetuximab plus chemotherapy in the pre-KRAS selection era.

METHODS

1022 tumour DNA samples (73 from fresh-frozen and 949 from formalin-fixed, paraffin-embedded tissue) from patients treated with cetuximab between 2001 and 2008 were gathered from 11 centres in seven European countries. 773 primary tumour samples had sufficient quality DNA and were included in mutation frequency analyses; mass spectrometry genotyping of tumour samples for KRAS, BRAF, NRAS, and PIK3CA was done centrally. We analysed objective response, progression-free survival (PFS), and overall survival in molecularly defined subgroups of the 649 chemotherapy-refractory patients treated with cetuximab plus chemotherapy.

FINDINGS

40.0% (299/747) of the tumours harboured a KRAS mutation, 14.5% (108/743) harboured a PIK3CA mutation (of which 68.5% [74/108] were located in exon 9 and 20.4% [22/108] in exon 20), 4.7% (36/761) harboured a BRAF mutation, and 2.6% (17/644) harboured an NRAS mutation. KRAS mutants did not derive benefit compared with wild types, with a response rate of 6.7% (17/253) versus 35.8% (126/352; odds ratio [OR] 0.13, 95% CI 0.07-0.22; p<0.0001), a median PFS of 12 weeks versus 24 weeks (hazard ratio [HR] 1.98, 1.66-2.36; p<0.0001), and a median overall survival of 32 weeks versus 50 weeks (1.75, 1.47-2.09; p<0.0001). In KRAS wild types, carriers of BRAF and NRAS mutations had a significantly lower response rate than did BRAF and NRAS wild types, with a response rate of 8.3% (2/24) in carriers of BRAF mutations versus 38.0% in BRAF wild types (124/326; OR 0.15, 95% CI 0.02-0.51; p=0.0012); and 7.7% (1/13) in carriers of NRAS mutations versus 38.1% in NRAS wild types (110/289; OR 0.14, 0.007-0.70; p=0.013). PIK3CA exon 9 mutations had no effect, whereas exon 20 mutations were associated with a worse outcome compared with wild types, with a response rate of 0.0% (0/9) versus 36.8% (121/329; OR 0.00, 0.00-0.89; p=0.029), a median PFS of 11.5 weeks versus 24 weeks (HR 2.52, 1.33-4.78; p=0.013), and a median overall survival of 34 weeks versus 51 weeks (3.29, 1.60-6.74; p=0.0057). Multivariate analysis and conditional inference trees confirmed that, if KRAS is not mutated, assessing BRAF, NRAS, and PIK3CA exon 20 mutations (in that order) gives additional information about outcome. Objective response rates in our series were 24.4% in the unselected population, 36.3% in the KRAS wild-type selected population, and 41.2% in the KRAS, BRAF, NRAS, and PIK3CA exon 20 wild-type population.

INTERPRETATION

While confirming the negative effect of KRAS mutations on outcome after cetuximab, we show that BRAF, NRAS, and PIK3CA exon 20 mutations are significantly associated with a low response rate. Objective response rates could be improved by additional genotyping of BRAF, NRAS, and PIK3CA exon 20 mutations in a KRAS wild-type population.

FUNDING

Belgian Federation against Cancer (Stichting tegen Kanker).

Targeting the MAPK pathway in melanoma: why some approaches succeed and other fail

The Mitogen Activated Protein Kinase (MAPK) pathway plays a key role in melanoma development making it an important therapeutic target. In normal cells, the tightly regulated pathway relays extracellular signals from cell membrane to nucleus via a cascade of phosphorylation events. In melanomas, dysregulation of the MAPK pathway occurs frequently due to activating mutations in the B-RAF and RAS genes or other genetic or epigenetic modifications, leading to increased signaling activity promoting cell proliferation, invasion, metastasis, migration, survival and angiogenesis. However, identification of ideal pathway member to therapeutically target for maximal clinical benefit to melanoma patients remains a challenge. This review provides an overview of the obstacles faced targeting the MAPK pathway and why certain therapeutic approaches succeed while others fail. The review summarizes the roles played by the proteins, therapeutic potential and the drugs available to target each member of the pathway as well as concerns related to each. Potential for targeting multiple points and inhibiting other pathways along with MAPK inhibition for optimal efficacy are discussed along with explanations for development of drug resistance, which includes discussions related to cross-talk between pathways, RAF kinase isoform switching and phosphatase deregulation. Finally, the use of nanotechnology is reviewed as an approach to target the MAPK pathway using both genetic and pharmacological agents simultaneously targeting multiple points in the pathway or in combination with other cascades.

Disruption of IGF-1R signaling increases TRAIL-induced apoptosis: a new potential therapy for the treatment of melanoma

Resistance of cancer cells to apoptosis is dependent on a balance of multiple genetic and epigenetic mechanisms, which up-regulate efficacy of the surviving growth factor-receptor signaling pathways and suppress death-receptor signaling pathways. The Insulin-like Growth Factor-1 Receptor (IGF-1R) signaling pathway is highly active in metastatic melanoma cells by mediating downstream activation of PI3K-AKT and MAPK pathways and controlling general cell survival and proliferation. In the present study, we used human melanoma lines with established genotypes that represented different phases of cancer development: radial-growth-phase WM35, vertical-growth-phase WM793, metastatic LU1205 and WM9 [1]. All these lines have normal NRAS. WM35, WM793, LU1205 and WM9 cells have mutated BRAF (V600E). WM35 and WM9 cells express normal PTEN, while in WM793 cells PTEN expression is down-regulated; finally, in LU1205 cells PTEN is inactivated by mutation. Cyclolignan picropodophyllin (PPP), a specific inhibitor of IGF-1R kinase activity, strongly down-regulated the basal levels of AKT activity in WM9 and in WM793 cells, modestly does so in LU1205, but has no effect on AKT activity in the early stage WM35 cells that are deficient in IGF-1R. In addition, PPP partially down-regulated the basal levels of active ERK1/2 in all lines used, highlighting the role of an alternative, non-BRAF pathway in MAPK activation. The final result of PPP treatment was an induction of apoptosis in WM793, WM9 and LU1205 melanoma cells. On the other hand, dose-dependent inhibition of IGF-1R kinase activity by PPP at a relatively narrow dose range (near 500 nM) has different effects on melanoma cells versus normal cells, inducing apoptosis in cancer cells and G2/M arrest of fibroblasts. To further enhance the pro-apoptotic effects of PPP on melanoma cells, we used a combined treatment of TNF-Related Apoptosis-Inducing Ligand (TRAIL) and PPP. This combination substantially increased death by apoptosis for WM793 and WM9 cells, but did so only modestly for LU1205 cells with very high basal activity of AKT. The ultimate goal of this direction of research is the discovery of a new treatment method for highly resistant human metastatic melanomas. Our findings provide the rationale for further preclinical evaluation of this novel treatment.