Project 1: Genomic Sunlight Dosimeters for Melanoma Prevention
Douglas Brach, PhD, Deepak Narayan, MD, Michael Krauthammer, MD/PhD, Co-Leaders
Detecting melanoma early leads to a nearly 100% cure rate, but diagnosing it at an advanced stage results in less than 20% survival. The power of early diagnosis has made it the major approach to preventing death from melanoma. Yet there is little evidence that large public skin cancer screenings prevent melanoma deaths. Focusing on people at greatest risk would be possible with an early predictor of risk that helps the primary care physician identify patients who should be followed by a dermatologist. This preventive test needs to measure both aspects of melanoma risk: genetic risk and sun-exposure risk. Project 1 focus is on sun-exposure risk because most people with Fitzpatrick Type I skin do not get melanoma. Yet UV exposure is usually ascertained by patient recollections rather than by objective biological indicators of past sun exposure. To overcome this critical barrier to assessing personal UV exposure and thus melanoma risk, we propose to couple two new technologies with Next-Gen sequencing to create genomic surrogate biomarkers of long-term sun exposure. One dosimeter takes advantage of the accumulation of DNA photoproducts in special regions of the genome; the other incorporates our knowledge about clonal expansion of cells in skin. We then evaluate these genomic dosimeter readings in skin for association with melanoma. The Specific Aims are:
Aim 1: Map human genomic regions that are UV damage hotspots or DNA repair slowspots.
Aim 2: Quantitate rare UV-mutated genes in skin in vivo.
Aim 3: Use genomic regions sensitive to UV photoproducts and mutations as dosimeters to correlate cumulative sunlight exposure in normal skin to risk for melanoma. These studies establish ways to objectively ascertain exposure to cancer risk using modern measurement technologies.
Project 2: The PD-1/B7-H1 Pathway and Melanoma Immunity
Lieping Chen, PhD, and Mario Sznol, MD, Co-Leaders
Multiple factors in the cancer microenvironment down-regulate tumor immunity and promote tumor progression. In melanoma, one of the dominant mechanisms is the induction of co-inhibitory receptors on tumor-specific T cells and expression of corresponding co-inhibitory ligands by tumor or other cells within tumor stroma, leading to complete or partial loss of T-cell effector functions. Amplified co-inhibitory interactions in the cancer microenvironment impede not only immune tumor surveillance, but also therapeutic immune interventions that may explain the failure of approaches aimed at stimulation of T cells, including tumor antigen-based vaccination and T cell stimulatory cytokines. A prime example of the co-inhibitory interactions is the B7-H1 (PD-L1)/PD-1 pathway. Preclinical and clinical studies support B7-H1 as an important co-inhibitory molecule in the down-regulation of immune responses in the melanoma microenvironment and blockade of the B7-H1/PD-1 pathway as one of the most promising approaches for the treatment of melanoma. The specific aims are:
Aim 1: to assess the association between B7-H1/PD-1 expression in human melanoma microenvironment with clinical response to anti-PD-1 therapy
Aim 2: to study effector mechanisms of the B7-H1/PD-1 blockade in augmenting anti-melanoma immunity and in melanoma regression;
Aim 3: to maximize melanoma therapeutic immunity by mechanism-based combinatory approaches. Our studies should have direct impact for current development of B7-H1/PD-1 blockade as a novel and promising approach for melanoma therapy.
Project 3: Molecular Diversity of Melanomas and Response to Targeted Therapy
Ruth Halaban, PhD, Harriet Kluger, MD, Titus J. Boggon, PhD, Co-Leaders
The new treatment opportunities and the remarkable heterogeneity of melanoma tumors require better profiling of tumor sub-types to achieve efficient selection of patients for targeted therapies. We will focus on responses to BRAF inhibitors (BRAFi) such as PLX4032/RG7204/ Vemurafenib and GSK2118436. The studies will include novel kinase inhibitors developed by Plexxikon to overcome the “paradoxical effect” of BRAFi (i.e., stimulation of cells with wild type BRAF), termed “paradox breakers” (PLX-PB). We will assess the characteristics of tumors poorly responsive to BRAFi compared to those with durable response, relapsing over a year after treatment. The major translational outcome of this work is classification of melanomas by phospho-proteomic/genomic/gene expression aberrations that show an association between treatment and response that will lead to development of assays for selection of patients for targeted therapies. In addition, the project will facilitate clinical trials of novel BRAFV600 kinase inhibitors.
Aim 1: To correlate phospho-proteomic, genomic and gene expression aberrations with resistance to BRAFi.
Aim 2: To perform functional analyses on the best markers associated with treatment response employing melanoma cells in culture.
Aim 3: To conduct a Phase I clinical trial with next-generation “paradox-breakers” (PB) BRAFi developed by Plexxikon Inc.
Project 4: The RAC1 Pathways as a Target for Melanoma Therapy
Joseph Schlessinger, PhD, Ruth Halaban, PhD, Titus J. Boggon, PhH, Harriet Kluger, MD, Co-Leaders
In order to discover new targets for therapy, we sequenced the coding regions of~100 melanomas and identified a large number of somatic mutations and inherited Single Nucleotide Variants (SNVs). One of the most important findings of this effort is the identification of the “RAC1 signaling pathway” as a potential new target for melanoma therapy. The analysis revealed a recurrent, UV signature activating mutation in this RHO family of small GTPases, RAC^P29S, in ~9% of sun-exposed melanomas. In addition, the sequencing data revealed mutations in upstream regulators and downstream effectors of RAC1 pathway in a large numbers of melanoma tumors. Functional studies demonstrated an important role in proliferation and migration of not only mutant but also melanoma cells that that do not harbor the P29S mutation. The data suggest that pharmacological inhibition of RAC1 or its critical effector(s) can be applied for development of new therapies for melanoma patients. The general goals of this project are to determine the frequency and prognostic significance of RAC^P29S mutation in sun exposed melanocytic lesions, and to identify downstream effectors of RAC1 most likely to be druggable targets in this pathway. The specific aims are:
Aim 1: To determine the frequency of RAC1P29S mutation and RAC1 expression levels in a large cohort of melanocytic lesions and correlate with pathological features and tumor progression.
Aim 2: To elucidate the downstream targets of activated RAC1 in melanomas.
Aim 3: To identify small-molecule inhibitors of PAK kinases, the RAC1 effectors. These studies are likely to provide new opportunities for drug discovery for melanomas and possibly other cancers that can facilitate patient-tailored targeted therapy.