Cytokine therapy in melanoma

Promising Strategies for Overcoming BRAF Inhibitor Resistance Based on Known Resistance Mechanisms

BACKGROUND

Almost 50% of metastatic melanomas harbor BRAF mutations. Since 2011, BRAF inhibitors have exhibited striking clinical benefits in BRAF-mutant melanoma patients. Unfortunately, their therapeutic effects are often temporary. The resistance mechanisms vary and can be broadly classified as MAPK reactivation-dependent and -independent. Elucidation of these resistance mechanisms provides new insights into strategies for overcoming resistance. Indeed, several alternative treatment strategies, including changes in the mode of administration, combinations of BRAF and MEK inhibitors, and immunotherapy have been verified as beneficial to BRAF inhibitor-resistant melanoma patients.

Prospect

In this review, we discuss promising strategies for overcoming drug resistance and highlighting the prospects for discovering strategies to counteract BRAF inhibitor resistance.

Targeting the alternatively spliced soluble isoform of CTLA-4: prospects for immunotherapy?

CTLA-4 is an inhibitory protein that contributes to immune homeostasis and tolerance, a role that has led to its exploitation as a therapeutic in several clinical settings including cancer and autoimmune disease. Development of CTLA-4 therapies focused largely on the full-length receptor isoform but other CTLA-4 isoforms are also expressed, including a secretable form of CTLA-4 (soluble CTLA-4 [sCTLA-4]). The contribution of sCTLA-4 to immune regulation has been less well studied, primarily because it was identified some years after the original description of CTLA-4. Here, we examine how sCTLA-4 might contribute to immune regulation and ask whether it might be a biomarker to inform current CTLA-4 therapies or represent a novel CTLA-4 target for future therapeutics.

Achievements and challenges of molecular targeted therapy in melanoma

The treatment of melanoma has been revolutionized over the past decade with the development of effective molecular and immune targeted therapies. The great majority of patients with melanoma have mutations in oncogenes that predominantly drive signaling through the mitogen activated protein kinase (MAPK) pathway. Analytic tools have been developed that can effectively stratify patients into molecular subsets based on the identification of mutations in oncogenes and/or tumor suppressor genes that drive the MAPK pathway. At the same time, potent and selective inhibitors of mediators of the MAPK pathway such as RAF, MEK, and ERK have become available. The most dramatic example is the development of single-agent inhibitors of BRAF (vemurafenib, dabrafenib, encorafenib) and MEK (trametinib, cobimetinib, binimetinib) for patients with metastatic BRAFV600-mutant melanoma, a subset that represents 40% to 50% of patients with metastatic melanoma. More recently, the elucidation of mechanisms underlying resistance to single-agent BRAF inhibitor therapy led to a second generation of trials that demonstrated the superiority of BRAF inhibitor/MEK inhibitor combinations (dabrafenib/trametinib; vemurafenib/cobimetinib) compared to single-agent BRAF inhibitors. Moving beyond BRAFV600 targeting, a number of other molecular subsets--such as mutations in MEK, NRAS, and non-V600 BRAF and loss of function of the tumor suppressor neurofibromatosis 1 (NF1)--are predicted to respond to MAPK pathway targeting by single-agent pan-RAF, MEK, or ERK inhibitors. As these strategies are being tested in clinical trials, preclinical and early clinical trial data are now emerging about which combinatorial approaches might be best for these patients.

Emerging clinical issues in melanoma in the molecularly targeted era

The standard of care of patients with malignant melanoma is dramatically changing, hallmarked by the approval of three new agents for the treatment of malignant melanoma in 2011. In this changing therapeutic landscape, several clinical issues are emerging which will best be addressed through the application of advances in molecular analytics, diagnostics, and therapeutics. It is expected that dedicated and coordinated efforts in basic, translational, and clinical will be responsible for the next major breakthroughs in the care of patients with this dreaded disease. In this chapter, five critical, emerging clinical issues are presented with descriptions of approaches that might be expected to help solve these challenges to optimal patient care.

Long-lasting complete response of metastatic melanoma to ipilimumab with analysis of the resident immune cells

Even though ipilimumab is a promising antibody used for stage IV melanoma therapy, the response varies and is difficult to predict. We here report on a case of successful treatment with ipilimumab in dacarbazine-resistant metastatic malignant melanoma, including a review of the literature on the long-term treatment results. A 62-year-old patient with a history of a resected lentigo-maligna melanoma 5 years earlier and parotideal metastasis 1 year before was admitted with a newly detected 3.5 cm liver metastasis. Atypical liver resection was performed (R1). Immunohistochemically, CD3+ T-lymphocytes and CD68+ macrophages were detected at the tumour margins and within the parotideal and hepatic melanoma metastases. A sub-analysis of the liver metastasis showed scattered FOX-P3+ regulatory T-lymphocytes as well as multiple CD8+ effector T-cells. Chemotherapy with dacarbazine 1,000 mg/m(2)/day was administered at 4-weeks intervals for 3 months. A follow-up positron-emission computed tomography and liver biopsy revealed melanoma metastases in the liver, lungs, and mediastinum. Compassionate use of ipilimumab was administered at 3 mg/kg every 3 weeks for a total of four doses. After an initial increase in tumour size, most lesions responded, but progressive axillary and cervical lymphadenopathy was observed before complete remission was achieved. Side effects included fatigue, dyspnoea, cough, upper abdominal pain with diarrhoea, and gingival hyperplasia. Now, 36 months after ipilimumab therapy and 8 years after the initial melanoma diagnosis, the tumour did not recur. It would be challenging to hypothesize that long intervals between diagnosis and need for treatment, clinical side effects, an initial increase in tumour size and the presence of intra-tumoural T-cells and macrophages might predict tumour response.

The intersection of immune-directed and molecularly targeted therapy in advanced melanoma: where we have been, are, and will be

In three years, four drugs have gained regulatory approval for the treatment of metastatic and unresectable melanoma, with at least seven other drugs having recently completed, currently in, or soon to be in phase III clinical testing. This amazing achievement has been made following a remarkable increase of knowledge in molecular biology and immunology that led to the identification of high-valued therapeutic targets and the clinical development of agents that effectively engage and inhibit these targets. The discovery of either effective molecularly targeted therapies or immunotherapies would have led to dramatic improvements to the standard-of-care treatment of melanoma. However, through parallel efforts that have showcased the efficacy of small-molecule BRAF and MAP-ERK kinase (MEK) inhibitors, as well as the immune checkpoint inhibitors, namely ipilimumab and the anti-PD1/PDL1 antibodies (lambrolizumab, nivolumab, MPDL3280), an opportunity exists to transform the treatment of melanoma specifically and cancer generally by exploring rational combinations of molecularly targeted therapies, immunotherapies, and molecular targeted therapies with immunotherapies. This overview presents the historical context to this therapeutic revolution, reviews the benefits and limitations of current therapies, and provides a look ahead at where the field is headed.

Antigen-specific versus antigen-nonspecific immunotherapeutic approaches for human melanoma: the need for integration for optimal efficacy?

Due to its immunogenecity and evidence of immune responses resulting in tumor regression, metastatic melanoma has been the target for numerous immunotherapeutic approaches. Unfortunately, based on the clinical outcomes, even the successful induction of tumor-specific responses does not correlate with efficacy. Immunotherapies can be divided into antigen-specific approaches, which seek to induce T cells specific to one or several known tumor associated antigens (TAA), or with antigen-nonspecific approaches, which generally activate T cells to become nonspecifically lytic effectors. Here the authors critically review the different immunotherapeutic approaches in melanoma.