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

Hypoxia in Skin Cancer: Molecular Basis and Clinical Implications

Skin cancer is one of the most prevalent cancers in the Caucasian population. In the United States, it is estimated that at least one in five people will develop skin cancer in their lifetime, leading to significant morbidity and a healthcare burden. Skin cancer mainly arises from cells in the epidermal layer of the skin, where oxygen is scarce. There are three main types of skin cancer: malignant melanoma, basal cell carcinoma, and squamous cell carcinoma. Accumulating evidence has revealed a critical role for hypoxia in the development and progression of these dermatologic malignancies. In this review, we discuss the role of hypoxia in treating and reconstructing skin cancers. We will summarize the molecular basis of hypoxia signaling pathways in relation to the major genetic variations of skin cancer.

Approved Small-Molecule ATP-Competitive Kinases Drugs Containing Indole/Azaindole/Oxindole Scaffolds: R&D and Binding Patterns Profiling

Kinases are among the most important families of biomolecules and play an essential role in the regulation of cell proliferation, apoptosis, metabolism, and other critical physiological processes. The dysregulation and gene mutation of kinases are linked to the occurrence and development of various human diseases, especially cancer. As a result, a growing number of small-molecule drugs based on kinase targets are being successfully developed and approved for the treatment of many diseases. The indole/azaindole/oxindole moieties are important key pharmacophores of many bioactive compounds and are generally used as excellent scaffolds for drug discovery in medicinal chemistry. To date, 30 ATP-competitive kinase inhibitors bearing the indole/azaindole/oxindole scaffold have been approved for the treatment of diseases. Herein, we summarize their research and development (R&D) process and describe their binding models to the ATP-binding sites of the target kinases. Moreover, we discuss the significant role of the indole/azaindole/oxindole skeletons in the interaction of their parent drug and target kinases, providing new medicinal chemistry inspiration and ideas for the subsequent development and optimization of kinase inhibitors.

Effect of antioxidants coenzyme Q10 and β-carotene on the cytotoxicity of vemurafenib against human malignant melanoma

Melanoma is a type of highly invasive skin cancer derived from melanocytes with poor prognosis. Vemurafenib (PLX4032) is a clinically approved targeted therapeutic for BRAF mutant melanoma that has a high therapeutic response rate and significantly prolongs the overall survival time of patients with melanoma. Antioxidants have been widely used as supplements for cancer prevention and for decreasing the side effects of cancer therapy. However, antioxidants can also protect cancer cells from oxidative stress and promote cancer growth and progression. The present study aimed to examine the effect of the antioxidants coenzyme Q10 (CoQ10) and β-carotene on melanoma cell growth and invasiveness and on the cytotoxicity of vemurafenib against both vemurafenib-sensitive (SK-MEL-28) and vemurafenib-resistant (A2058) human malignant melanoma cell lines. MTS assay and wound-healing assay demonstrated that CoQ10 alone significantly reduced the viability and migration of melanoma cells, respectively, and synergistically worked with vemurafenib to decrease the viability and migration of human melanoma cells. In contrast, MTS assay and flow cytometry revealed that β-carotene alone did not affect the viability and apoptosis induction of melanoma cells; however, it inhibited cell migration and invasiveness. Wound-healing and Transwell assay demonstrated that β-carotene alleviated the cytotoxicity of vemurafenib and mitigated the inhibitory effect of vemurafenib on cell migration and invasion. Both CoQ10 and β-carotene protected melanoma cells from undergoing apoptosis induced by vemurafenib. Immunoblotting demonstrated that β-carotene at physiological concentration worked synergistically with vemurafenib to suppress the Ras-Raf-Mek-Erk intracellular signaling pathway. The present study aimed to add to the evidence of the in vitro effects of CoQ10 and β-carotene on the antimelanoma effects of vemurafenib.

Multicenter, real-life experience with checkpoint inhibitors and targeted therapy agents in advanced melanoma patients in Switzerland

Metastatic melanoma is a highly aggressive disease. Recent progress in immunotherapy (IT) and targeted therapy (TT) has led to significant improvements in response and survival rates in metastatic melanoma patients. The current project aims to determine the benefit of the introduction of these new therapies in advanced melanoma across several regions of Switzerland. This is a retrospective multicenter analysis of 395 advanced melanoma patients treated with standard chemotherapy, checkpoint inhibitors, and kinase inhibitors from January 2008 until December 2014. The 1-year survival was 69% (n=121) in patients treated with checkpoint inhibitors (IT), 50% in patients treated with TTs (n=113), 85% in the IT+TT group (n=66), and 38% in patients treated with standard chemotherapy (n=95). The median overall survival (mOS) from first systemic treatment in the entire study cohort was 16.9 months. mOS of patients treated either with checkpoint or kinase inhibitors (n=300, 14.6 months) between 2008 and 2014 was significantly improved (P<0.0001) compared with patients treated with standard chemotherapy in 2008–2009 (n=95, 7.4 months). mOS of 61 patients with brain metastases at stage IV was 8.1 versus 12.5 months for patients without at stage IV (n=334), therefore being significantly different (P=0.00065). Furthermore, a significant reduction in hospitalization duration compared with chemotherapy was noted. Treatment with checkpoint and kinase inhibitors beyond clinical trials significantly improves the mOS in real life and the results are consistent with published prospective trial data.

Function and Clinical Implications of Long Non-Coding RNAs in Melanoma

Metastatic melanoma is the most deadly type of skin cancer. Despite the success of immunotherapy and targeted agents, the majority of patients experience disease recurrence upon treatment and die due to their disease. Long non-coding RNAs (lncRNAs) are a new subclass of non-protein coding RNAs involved in (epigenetic) regulation of cell growth, invasion, and other important cellular functions. Consequently, recent research activities focused on the discovery of these lncRNAs in a broad spectrum of human diseases, especially cancer. Additional efforts have been undertaken to dissect the underlying molecular mechanisms employed by lncRNAs. In this review, we will summarize the growing evidence of deregulated lncRNA expression in melanoma, which is linked to tumor growth and progression. Moreover, we will highlight specific molecular pathways and modes of action for some well-studied lncRNAs and discuss their potential clinical implications.

The Predicted Impact of Ipilimumab Usage on Survival in Previously Treated Advanced or Metastatic Melanoma in the UK

BACKGROUND

Evaluating long-term prognosis is important for physicians, patients and payers. This study reports the results of a model developed to predict long-term survival for UK patients receiving second-line ipilimumab.

METHODS

MDX010-20 trial data were used to predict survival for ipilimumab versus UK best supportive care. Two aspects of this analysis required novel approaches: 1) The overall survival Kaplan-Meier data shape is unusual: an initial steep decline is observed before a 'plateau'. 2) The need to extrapolate beyond the trial end (4.6 years). Based upon UK clinician advice, a three-part curve fit was used: from 0-1.5 years, Kaplan-Meier data from the trial; from 1.5-5 years, standard parametric curve fits; after 5 years, long-term data from the American Joint Committee on Cancer registry.

RESULTS

This approach provided good internal validity: low mean absolute error and good match to median and mean trial data. Lifetime predicted means were 2.77 years for ipilimumab and 1.07 for best supportive care, driven by increased long-term survival with ipilimumab.

CONCLUSION

To understand the full benefit of treatment and to meet reimbursement requirements, accurate estimation of treatment benefit is key. Models, such as the one presented, can be used to extrapolate beyond trials.

Aberrant CpG methylation of the TFAP2A gene constitutes a mechanism for loss of TFAP2A expression in human metastatic melanoma

Metastatic melanoma is a deadly treatment-resistant form of skin cancer whose global incidence is on the rise. During melanocyte transformation and melanoma progression the expression profile of many genes changes. Among these, a gene implicated in several steps of melanocyte development, TFAP2A, is frequently silenced; however, the molecular mechanism of TFAP2A silencing in human melanoma remains unknown. In this study, we measured TFAP2A mRNA expression in primary human melanocytes compared to 11 human melanoma samples by quantitative real-time RT-PCR. In addition, we assessed CpG DNA methylation of the TFAP2A promoter in these samples using bisulfite sequencing. Compared to primary melanocytes, which showed high TFAP2A mRNA expression and no promoter methylation, human melanoma samples showed decreased TFAP2A mRNA expression and increased promoter methylation. We further show that increased CpG methylation correlates with decreased TFAP2A mRNA expression. Using The Cancer Genome Atlas, we further identified TFAP2A as a gene displaying among the most decreased expression in stage 4 melanomas vs. non-stage 4 melanomas, and whose CpG methylation was frequently associated with lack of mRNA expression. Based on our data, we conclude that TFAP2A expression in human melanomas can be silenced by aberrant CpG methylation of the TFAP2A promoter. We have identified aberrant CpG DNA methylation as an epigenetic mark associated with TFAP2A silencing in human melanoma that could have significant implications for the therapy of human melanoma using epigenetic modifying drugs.

In vitro treatment of melanoma brain metastasis by simultaneously targeting the MAPK and PI3K signaling pathways

Malignant melanoma is the most lethal form of skin cancer, with a high propensity to metastasize to the brain. More than 60% of melanomas have the BRAF^V600E mutation, which activates the mitogen-activated protein kinase (MAPK) pathway [1]. In addition, increased PI3K (phosphoinositide 3-kinase) pathway activity has been demonstrated, through the loss of activity of the tumor suppressor gene, PTEN [2]. Here, we treated two melanoma brain metastasis cell lines, H1_DL2, harboring a BRAF^V600E mutation and PTEN loss, and H3, harboring WT (wild-type) BRAF and PTEN loss, with the MAPK (BRAF) inhibitor vemurafenib and the PI3K pathway associated mTOR inhibitor temsirolimus. Combined use of the drugs inhibited tumor cell growth and proliferation in vitro in H1_DL2 cells, compared to single drug treatment. Treatment was less effective in the H3 cells. Furthermore, a strong inhibitory effect on the viability of H1_DL2 cells, when grown as 3D multicellular spheroids, was seen. The treatment inhibited the expression of pERK1/2 and reduced the expression of pAKT and p-mTOR in H1_DL2 cells, confirming that the MAPK and PI3K pathways were inhibited after drug treatment. Microarray experiments followed by principal component analysis (PCA) mapping showed distinct gene clustering after treatment, and cell cycle checkpoint regulators were affected. Global gene analysis indicated that functions related to cell survival and invasion were influenced by combined treatment. In conclusion, we demonstrate for the first time that combined therapy with vemurafenib and temsirolimus is effective on melanoma brain metastasis cells in vitro. The presented results highlight the potential of combined treatment to overcome treatment resistance that may develop after vemurafenib treatment of melanomas.

Anticancer activity of combination targeted therapy using cetuximab plus vemurafenib for refractory BRAF (V600E)-mutant metastatic colorectal carcinoma

Mismatch-repair-deficient colorectal cancers often contain kinase-activating V600E BRAF mutations, but no clinical utility has yet been demonstrated in this setting for monotherapy using oral braf kinase inhibitors such as vemurafenib or dabrafenib. Recent studies have indicated that tumour resistance to braf inhibition is mediated by upregulated epidermal growth factor receptor (egfr) signalling, disruption of which is a routine treatment strategy in KRAS wild-type colorectal cancer. In this report, we describe the clinical course of a heavily pretreated patient who elected to receive off-label dual-targeted braf- and egfr-inhibitory therapy with good tolerance and apparent clinical benefit.

Clinicopathological relevance of BRAF mutations in human cancer

BRAF represents one of the most frequently mutated protein kinase genes in human tumours. The mutation is commonly tested in pathology practice. BRAF mutation is seen in melanoma, papillary thyroid carcinoma (including papillary thyroid carcinoma arising from ovarian teratoma), ovarian serous tumours, colorectal carcinoma, gliomas, hepatobiliary carcinomas and hairy cell leukaemia. In these cancers, various genetic aberrations of the BRAF proto-oncogene, such as different point mutations and chromosomal rearrangements, have been reported. The most common mutation, BRAF V600E, can be detected by DNA sequencing and immunohistochemistry on formalin fixed, paraffin embedded tumour tissue. Detection of BRAF V600E mutation has the potential for clinical use as a diagnostic and prognostic marker. In addition, a great deal of research effort has been spent in strategies inhibiting its activity. Indeed, recent clinical trials involving BRAF selective inhibitors exhibited promising response rates in metastatic melanoma patients. Clinical trials are underway for other cancers. However, cutaneous side effects of treatment have been reported and therapeutic response to cancer is short-lived due to the emergence of several resistance mechanisms. In this review, we give an update on the clinical pathological relevance of BRAF mutation in cancer. It is hoped that the review will enhance the direction of future research and assist in more effective use of the knowledge of BRAF mutation in clinical practice.

Comparative analysis of MAPK and PI3K/AKT pathway activation and inhibition in human and canine melanoma

The lack of advanced animal models of human cancers is considered a barrier to developing effective therapeutics. Canine and human melanomas are histologically disparate but show similar disease progression and response to therapies. The purpose of these studies was to compare human and canine melanoma tumours and cell lines regarding MAPK and PI3K/AKT signalling dysregulation, and response to select molecularly targeted agents. Pathway activation was investigated via microarray and mutational analysis. Growth inhibition and cell cycle effects were assessed for pathway inhibitors AZD6244 (MAPK) and rapamycin (PI3K/AKT) in human and canine melanoma cells. Human and canine melanoma share similar differential gene expression patterns within the MAPK and PI3K/AKT pathways. Constitutive pathway activation and similar sensitivity to AZD6244 and rapamycin was observed in human and canine cells. These results show that human and canine melanoma share activation and sensitivity to inhibition of cancer-related signalling pathways despite differences in activating mutations.

[Mutation of the BRAF genes in non-small cell lung cancer]

BRAF mutations have been found to be a driver mutation and maybe a therapy target in patients with non-small cell lung cancer. This article reviews the current understanding of BRAF gene, its structure, expression, the signal pathway, as well as its relationship with cancer especially the targeted therapies for non-small cell lung cancer.

Assessment of association between BRAF-V600E mutation status in melanomas and clinical response to ipilimumab

Ipilimumab, a fully human monoclonal antibody against cytotoxic T lymphocyte antigen-4, has demonstrated significant improvement in overall survival in previously treated advanced melanoma patients. The BRAF inhibitor, vemurafenib, has shown up to 78% objective response rates in melanoma patients harboring the BRAF-V600E mutation but not in patients lacking the mutation. As an immune potentiator, the mechanism of action of ipilimumab may not be dependent of the activity of the BRAF pathway. To test this, we investigated whether the clinical activity of ipilimumab would be affected by the BRAF-V600E mutation status of the tumors. Thus, this retrospective analysis was carried using a set of tumor biopsies from a completed phase II clinical trial. CA184004 was a randomized, double-blind, multicenter trial of 82 previously treated or untreated patients with unresectable stage III/IV melanoma. Patients received ipilimumab 3 or 10 mg/kg every 3 weeks for four doses followed by maintenance dosing in eligible patients. The BRAF-V600E mutation status for 80 patients was determined in tumor biopsies by PCR-based assays. Data on disease control were available for 69 patients with evaluated BRAF-V600E mutation status. Rates of objective responses and stable disease in patients with BRAF-V600E mutation positive tumors (30%) were comparable to those in patients with the wild-type gene (~33%). Eleven patients displayed Durable Disease Control (DDC) of which 55% had BRAF-V600E mutation positive tumors and 45% did not. In the 48 patients showing no DDC, the mutation frequency was 50%. In this study, no association between BRAF-V600E mutation status of melanoma tumors and DDC after treatment with ipilimumab was detected.

Function but not phenotype of melanoma peptide-specific CD8(+) T cells correlate with survival in a multiepitope peptide vaccine trial (ECOG 1696)

ECOG 1696 was a Phase II multi-center trial testing vaccination with melanoma peptides, gp100, MART-1 and tyrosinase delivered alone, with GM-CSF, IFN-α2b or both cytokines to HLA-A2(+) patients with metastatic melanoma. Here, the frequency of circulating CD8(+) tetramer(+) (tet(+) ) T cells and maturation stages of responding T cells were serially monitored and compared with baseline values in a subset of patients (n = 37) from this trial. Multiparameter flow cytometry was used to measure the frequency of CD8(+) T cells specific for gp100, MART-1, tyrosinase and influenza (FLU) peptides. Expression of CD45RA/CCR7 on CD8(+) tet(+) T cells and CD25, CD27, CD28 on all circulating T cells was determined. Vaccine-induced changes in the CD8(+) tet(+) T cell frequency and phenotype were compared with results of IFN-γ ELISPOT assays and with clinical responses. The frequency of CD8(+) tet(+) T cells in the circulation was increased for the melanoma peptides (p < 0.03-0.0001) but not for FLU (p < 0.9). Only gp100- and MART-1-specific T cells differentiated to CD45RA(+) CCR7(-) effector/memory T cells. In contrast to the IFN-γ ELISPOT frequency, previously correlated with overall survival (Kirkwood et al., Clin Cancer Res 2009;15:1443-51), neither the frequency nor differentiation stage of CD8(+) tet(+) T cells correlated with clinical responses. Delivery of GM-CSF and/or IFN-α2b had no effects on the frequency or differentiation of CD8(+) tet(+) , CD8+ or CD4+ T cells. Phenotypic analyses of CD8(+) tet(+) T cells did not correlate with clinical responses to the vaccine, indicating that functional assessments of peptide-specific T cells are preferable for monitoring of anti-tumor vaccines.

Towards new therapeutic approaches for malignant melanoma

Recent progress in understanding the molecular mechanisms of the initiation and progression of melanoma has created new opportunities for developing novel therapeutic modalities to manage this potentially lethal disease. Although at first glance, melanoma carcinogenesis appears to be a chaotic system, it is indeed, arguably, a deterministic multistep process involving sequential alterations of proto-oncogenes, tumour suppressors and miRNA genes. The scope of this article is to discuss the most recent and significant advances in melanoma molecular therapeutics. It is apparent that using single agents targeting solely individual melanoma pathways might be insufficient for long-term survival. However, the outstanding results on melanoma survival observed with novel selective inhibitors of B-RAF, such as PLX4032 give hope that melanoma can be cured. The fact that melanoma develops acquired resistance to PLX4032 emphasises the importance of simultaneously targeting several pathways. Because the most striking feature of melanoma is its unsurpassed ability to metastasise, it is important to implement newer systems for drug delivery adapted from research on stem cells and nanotechnology.

Multikinase inhibitors: a new option for the treatment of thyroid cancer

Thyroid cancer typically has a good outcome following standard treatments, which include surgery, radioactive iodine ablation and treatment with TSH-suppressive levothyroxine. Thyroid cancers that persist or recur following these therapies have a poorer prognosis. Activation of mitogenic and angiogenic signaling pathways occurs in these cancers, and preclinical models have shown that inhibition of key kinase steps in these pathways can have antitumoral effects. Several of these kinase inhibitors have now been tested in phase II and phase III trials, with modestly encouraging results. Some promising data exist for the use of vandetanib (also known as ZD6474), motesanib, axitinib, cabozantinib (also known as XL184), sorafenib, sunitinib, pazopanib and lenvatinib (also known as E7080) in progressive thyroid cancer of medullary, papillary and follicular subtypes. These drugs are generally well-tolerated, although dose-limiting toxicities are common, and a few (probable) treatment-related deaths have been reported. Additional phase III trials will be needed to conclusively show that treatment benefit exceeds risk. Drug resistance can occur via activation of alternate mitogenic signals (pathway switching), as has been reported for the use of kinase inhibitors in other malignancies, such as melanoma. The hypothesis that combinations of kinase inhibitors targeting different pathways might produce better results is currently being tested in several clinical trials.

Equipoise should be amended, not abandoned

BACKGROUND

Benjamin Freedman has argued in 1987 that before a controlled trial is started, there should be 'genuine uncertainty in the expert medical community about the preferred treatment'. Freedman's definition of the concept is widespread in clinical research, but has been controversial since its start. Over the past decade, the equipoise controversy has become increasingly complex.

PURPOSE

This article aims: (1) to identify and clarify the main points of contention in the equipoise controversy, and (2) to reconcile the opposing views by pointing at areas of overlap between proponents and opponents in the equipoise debate.

METHODS

We analyze the positions of the leading authors in the equipoise debate in the past decade.

RESULTS

There is substantial overlap between the opponents and proponents of equipoise. Both should be able to accept the following answers to points of contention in the debate: (1) the therapeutic obligation can remain the basis for equipoise as long as it is conceived as an obligation to provide participants with competent care, (2) equipoise is grounded in a competent care and an epistemological dilemma, (3) equipoise does not as a rule prohibit placebo-controlled trials when proven effective treatment exists, (4) patient equipoise and individual physician equipoise are irrelevant, and (5) having to stop a trial is not always equivalent to disturbing equipoise. Clarification of these points of contention leads to a sharpened definition of equipoise: 'a state of genuine agnosticism or conflict in the expert medical community about the net preferred medically established procedure for the condition under study'. This definition asks of physician-researchers and members of IRBs to meet two conditions: (1) to genuinely evaluate to what extent a proposed randomized clinical trial solves a state of agnosticism or a knowledge conflict in the expert medical community and (2) to respect the standard of competent care, meaning that they consider whether the regular clinical standard from an all-things considered perspective is also the preferred standard in the research context. Equipoise is a specification of two general ethical principles for clinical research: scientific validity and a favorable risk benefit ratio. As a specification equipoise adds substance to these principles since they do not explicitly ask for the two conditions. Equipoise is a prima facie obligation rather than a morally authoritative principle for determining the acceptability of clinical trials. It needs to be balanced against other norms for clinical research. Violation of equipoise is therefore not always unethical.

LIMITATIONS

This study is limited to the context of randomized clinical trials.

CONCLUSIONS

There is no decisive reason to give up on the equipoise requirement.