Predictive Biomarkers for Immunotherapy in Melanoma

Special Article - Melanoma Skin Cancer

Austin J Dermatolog. 2016; 3(1): 1045.

# Predictive Biomarkers for Immunotherapy in Melanoma

Rabold K* and Blokx WAM

Department of Pathology, Radboud University Medical Center, Nijmegen, The Netherlands

*Corresponding author: Rabold K, Department of Pathology, Radboud University Medical Center, Nijmegen, The Netherlands

Received: December 07, 2015; Accepted: February 19, 2016; Published: February 22, 2016

## Abstract

Advanced melanoma is an aggressive tumor that is difficult to treat. Yet new immunotherapeutic strategies are dramatically improving clinical outcomes. Especially Dendritic Cell (DC) vaccination shows promising outcomes at relative low cost when compared to Adoptive Cell Therapy (ACT) and immune checkpoint inhibition. However, not all patients respond to immunotherapy equally and the costly treatments can cause severe toxicities. Therefore, identification of predictive biomarkers to enable selection of patients that are eligible for immunotherapies is of utmost importance in order to improve treatment efficacy and reduce overall cost as well as toxicities. Focus of current investigations lies on the composition of the tumor microenvironment, as an immune-active tumor microenvironment seems to be beneficial for the effect of immunotherapy. Here, we review immunotherapies in melanoma with focus on immune checkpoint inhibition and DC vaccination. Our objective is to give an overview on the recent state of predictive biomarkers for immunotherapy in melanoma.

Keywords: Melanoma; Immunotherapy; Prognosis; Predictive; Marker; Review

## Abbreviations

DC-Dendritic Cell; ACT-Adoptive Cell Therapy; APC - Antigen- Presenting Cell; MHC-Major Histocompatibility Complex; TSAs - Tumor-Specific Antigens; TCR- T-Cell Receptor; IFN - Interferon ; CTLA- 4 - Cytotoxic T-Lymphocyte Associated Antigen-4; PD- 1- Programmed Cell Death 1; TME - Tumor Microenvironment; MDSC - Myeloid-Derived Suppressor Cells; ACT - Adoptive Cellular Immunotherapy; CAR - Chimeric Antigen Receptor; FDA - Food and Drug Administration; EMA - European Medicines Agency; OS - Overall Survival; ORR - Overall Response Rate; irAE - Immune- Related Adverse Events; RR - Response Rate; PFS - Progression-Free Survival; TAAs - Tumor-Associated Antigens; pDC - Plasmacytoid Dendritic Cells; DAS – Dasatinib; VEGF - Vascular Endothelial Growth Factor

## Introduction

Two emerging hallmarks of cancer, ‘tumor-promoting inflammation’ and ‘avoiding immune destruction’, have been described in a landmark review by Hannah and Weinberg in 2011 [1]. Now it is widely accepted that inflammatory and immune cells can promote cancer outgrowth but can also repress tumor growth [2-4]. This dual role of immunity on tumorigenesis is referred to as cancer immunoediting, a dynamic process consisting of three phases: elimination, equilibrium, and escape [3,5].

Elimination of a developing tumor occurs when molecules and cells of the innate and adaptive immunity identify transformed cells and destroy them on the basis of their expression of Tumor- Specific Antigens (TSAs). This process is also referred to as cancer immunosurveillance [3]. However, the tumor might not always be completely eliminated, can then become dormant and enter into an equilibrium phase where net tumor outgrowth is controlled by the immune system [3]. Finally, tumor cells might be able to progress into the escape phase by immune suppressive effects or when

transformed cells acquire adaptations that allow them to grow in an immunologically unrestricted manner [3,6]. The major cellular mediators in immunosurveillance are CD8+ cytotoxic T-cells and CD4+ T helper cells, next to Dendritic Cells (DCs). In a series of stepwise events, called the cancer-immunity cycle, first neoantigens produced by the cancer cells are recognized by DCs. Next, DCs present the captured antigens on Major Histocompatibility Complex (MHC) molecules to CD8+ T-cells, leading to T-cell activation and production of apoptosis-inducing molecules or cytotoxic granules. Full T-cell activation requires also a co-stimulatory signal of the T-Cell Receptor (TCR) CD28molecule from B7.1 (CD80) or B7.2 (CD86) on the Antigen-Presenting Cell (APC) [7-9]. CD4+ Th1 cells can provide help to the CD8+ T-cells [10]. Both, CD8+ T-cells and CD4+ Th1 cells, restrain carcinogenesis by producing interferon (IFN)-γ and cytotoxins [11].

Nevertheless, tumor cells can develop mechanisms to escape the immune control. One is the inactivation of once activated T-cells [2, 3]. The two best known pathways of T-cell inactivation are the expression of the Cytotoxic T-Lymphocyte Associated Antigen-4 (CTLA-4) receptor on the surface of a T-cell which transducts inhibitory signals from the APC to the T-cell nucleus, and the expression of the Programmed Cell Death 1 (PD-1) receptor on the T-cell surface which may lead to inactivation of the T-cell after binding to its ligands (PD-L1 and PD-L2) on tumor tissue [12]. These are also called immune checkpoints. Secondly, tumors can escape immune control due to immunosuppression by suppressive cells in the Tumor Microenvironment (TME), such as Myeloid-Derived Suppressor Cells (MDSC) or regulatory T-cells (Treg) that produce immunosuppressive molecules [13,14].

With our increasing understanding of cancer immunoediting and increasing knowledge about the tumor microenvironment, new strategies are developed to use the power of immunity for protection against cancer development or cancer progression. The development of cancer immunotherapy has reached an important milestone. Overall survival in patients with advanced metastatic disease has been improved, and - in contrast to targeted cancer therapies - durable monotherapy responses are being reported for different cancer types with several different agents [15-20]. Melanoma is a very aggressive tumor with about 132,000 diagnoses globally each year [21]. Patients are diagnosed with melanoma at the median age of 64 years for men and 57 years for women [22]. Albeit 84% of melanomas are diagnosed in the early stage and are mostly curable, the more advanced stages are still a challenge [22]. Patients with localized melanoma have a 5-year survival of 98.3%, whereas survival rates are radically declining in regional and distant stage disease to 62.4% and 16%, respectively [22]. The median survival duration of patients with metastatic melanoma is poor with only6 to 9 months [23]. Targeted therapies (e.g. BRAF inhibitors) were widely used as first-line treatment of advanced melanoma, but have the drawback that, in most cases, patients will develop resistance [24]. With the emergence of immunotherapy, a shift towards immunotherapy as first-line treatment for advanced melanoma is now observed, since they provide durable tumor control and long-term survival benefits [24].

Here, we review the most successful immunotherapies in melanoma. These include adoptive T-cell therapy, immune checkpoint inhibitors, and cancer vaccines. Our major focus is to describe the current knowledge on predictive biomarkers, which are markers that predict the clinical effect of a specific treatment. They are needed to improve treatment outcomes and to better select patients for these often expensive or laborious treatments to minimize the high costs [25] of immunotherapies.

## Immunotherapies in Melanoma

Amongst the most successful strategies of immunotherapy in melanoma are adoptive cell therapy, immune checkpoint inhibitors, and cancer vaccines. The mechanisms, clinical efficacy, and known predictive biomarkers of these approaches are discussed, with emphasis on checkpoint inhibitors and dendritic cell vaccination, which are the most recent and successful developments in immunotherapy in melanoma.

## Adoptive Cell Therapy

In the Adoptive Cellular Immunotherapy (ACT), autologous or allogeneic tumor-reactive T-cells are administered to patients, which have the ability to mediate cancer regression. For the cell preparation, lymphocytes with high affinity for tumor antigens are isolated, selected ex vivo, stimulated in vitro, and expanded to achieve sufficient number to eliminate important tumor masses in the patient. In vitro activation allows escape from inhibitory factors that exist in vivo [26]. Immunosuppression by lymphocyte-depleting chemotherapy is performed immediately before T-cell infusion to provide a favorable microenvironment for antitumor immunity [26]. Once the cells are administered, they can proliferate and maintain their antitumor effector functions [26].

Promising results have been shown in melanoma patients, where 49-72% of the patients respond to autologous ACT treatment, depending on the dose of lymph depletion, and 22% show complete tumor regression [27,28]. Since some tumors in this study were rendered inoperable, this approach can be attractive for treatment of tumors that cannot be removed surgically. Nevertheless, the poor outcome of ACT trials in other solid cancers and some limitations of ACT, such as the inability to expand autologous antitumor T-cells, have led to the development of genetic modification of T-cells with either a T-Cell Receptor (TCR) or a Chimeric Antigen Receptor (CAR) [26, 29].

The costs of the preparation vary wildly depending on patient characteristics, the protocol used, and the efficiency of the processing lab and are thus difficult to define. However, the cell generation costs including release testing are estimated around $25,000 to$40,000 per patient [30,31], but additional medical costs such as lymph depletion and treatment of adverse events can inflate the total costs to approximately $90,000 to$100,000per patient [32].

Potential safety risks associated with ACT are on-target off-tumor and off-target activity toxicities, and cytokine-release syndromes, although these are uncommon [33,34]. On-target off-tumor activity occurs when the antigen target is not tumor-specific but also present on nonmalignant cells. In melanoma patients this can result in adverse events such as vitiligo, uveitis or hearing loss when patients are treated with T cells targeting melanocytic differentiation antigens [33,34]. Off-target reactivity can occur as cross-reactivity against peptides in proteins other than the targeted ones, of which only one case is known [34]. Cytokine release syndrome can occur due to high tumor cell lysis leading to high levels of cytokine release and macrophage activation. This can cause high fevers, rigors and hypotension [33] (Table 1).

Citation: Rabold K and Blokx WAM. Predictive Biomarkers for Immunotherapy in Melanoma. Austin J Dermatolog. 2016; 3(1): 1045. ISSN:2381-9189