Faculty Bibliography

Natural killer (NK) cells are innate immune cells that become progressively exhausted in advanced stage cancer, crippling their ability to execute antitumor functions. We previously characterized the nature of NK cell exhaustion in metastatic melanoma patients, reporting a correlation with high expression of TIM-3. Blockade of this immune checkpoint molecule reversed the exhausted phenotype and improved NK cell function.

Neural infiltration in primary melanoma is a histopathologic feature that has been associated with desmoplastic histopathologic subtype and local recurrence in the literature. We tested the hypothesis that improved detection and characterization of neural infiltration into peritumoral or intratumoral location and perineural or intraneural involvement could have a prognostic relevance. We studied 128 primary melanoma cases prospectively accrued and followed at New York University using immunohistochemical detection with antihuman neurofilament protein and routine histology with hematoxylin and eosin. Neural infiltration, defined as the presence of tumor cells involving or immediately surrounding nerve foci, was identified and characterized using both detection methods. Neural infiltration rate of detection was enhanced by immunohistochemistry for neurofilament in matched-pair design (47% by immunohistochemistry versus 25% by routine histology). Immunohistochemical detection of neural infiltration was significantly associated with ulceration (P = .021), desmoplastic and acral lentiginous histologic subtype (P = .008), and head/neck/hands/feet tumor location (P = .037). Routinely detected neural infiltration was significantly associated with local recurrence (P = .010). Immunohistochemistry detected more intratumoral neural infiltration cases compared with routine histology (30% versus 3%, respectively). Peritumoral and intratumoral nerve location had no impact on clinical outcomes. Using a multivariate model controlling for stage, neither routinely detected neural infiltration nor enhanced immunohistochemical characterization of neural infiltration was significantly associated with disease-free or overall survival. Our data demonstrate that routinely detected neural infiltration is associated with local recurrence in all histologic subtypes but that improved detection and characterization of neural infiltration with immunohistochemistry in primary melanoma does not add to prognostic relevance.

BACKGROUND: Melanoma is a heterogeneous tumor with subgroups requiring distinct therapeutic strategies. Genetic dissection of melanoma subgroups and identification of therapeutic agents are of great interest in the field. These efforts will ultimately lead to treatment strategies, likely combinatorial, based on genetic information. METHODS: To identify "driver" genes that can be targeted therapeutically, we screened metastatic melanomas for somatic mutations by exome sequencing followed by selecting those with available targeted therapies directed to the gene product or its functional partner. The FBXW7 gene and its substrate NOTCH1 were identified and further examined. Mutation profiling of FBXW7, biological relevance of these mutations and its inactivation, and pharmacological inhibition of NOTCH1 were examined using in vitro and in vivo assays. RESULTS: We found FBXW7 to be mutated in eight (8.1%) melanoma patients in our cohort (n = 103). Protein expression analysis in human tissue samples (n = 96) and melanoma cell lines (n = 20) showed FBXW7 inactivation as a common event in melanoma (40.0% of cell lines). As a result of FBXW7 loss, we observed an accumulation of its substrates, such as NOTCH1. Ectopic expression of mutant forms of FBXW7 (by 2.4-fold), as well as silencing of FBXW7 in immortalized melanocytes, accelerated tumor formation in vivo (by 3.9-fold). Its inactivation led to NOTCH1 activation, upregulation of NOTCH1 target genes (by 2.6-fold), and promotion of tumor angiogenesis and resulted in tumor shrinkage upon NOTCH1 inhibition (by fivefold). CONCLUSIONS: Our data provides evidence on FBXW7 as a critical tumor suppressor mutated and inactivated in melanoma that results in sustained NOTCH1 activation and renders NOTCH signaling inhibition as a promising therapeutic strategy in this setting.

Recent whole genome melanoma sequencing studies have identified recurrent mutations in the gene encoding the catalytic subunit of serine/threonine phosphatase 6 (PPP6C/PP6C). However, the biochemical, functional, and clinical ramifications of these mutations are unknown. Sequencing PP6C from patients with melanoma (233 primary and 77 metastatic specimens) with extended prospective clinical outcome revealed a large number of hotspot mutations in patients with both primary and metastatic melanoma. Despite minimal association between stage and presence of PP6C mutations in patients with primary melanoma, a subpopulation of cells within each tumor did contain PP6C mutations, suggesting PP6C mutation is an early, but non-tumor-initiating event in melanoma. Among patients with primary melanoma with PP6C mutations, patients with stop mutations had significantly shorter recurrence-free survival compared with patients without stop mutations. In addition, PP6C mutations were independent of commonly observed BRAF and NRAS mutations. Biochemically, PP6C mutations could be classified as those that interact with PP6C regulatory subunits and those that do not. Mutations that did not bind to PP6C regulatory subunits were associated with increased phosphorylation of Aurora kinase, a PP6C substrate, and mitotic defects. However, both classes of PP6C mutations led to increased sensitivity to Aurora kinase inhibition. Together, these data support for the first time that PP6C mutations are molecularly, biochemically, and clinically heterogeneous. Implications: PP6C mutations have distinct functional and clinical consequences in melanoma, and confer sensitivity to Aurora A kinase inhibitors. Mol Cancer Res; 12(3); 433-9. (c)2013 AACR.

Global microRNA (miRNA) profile may predict prostate cancer (PCa) behaviors. In this study, we examined global miRNA expression by miRNA profiling as well as specific miRNA expression levels in PCa epithelium and stroma by in situ hybridization (ISH) and correlated with various clinicopathological features. We first performed comprehensive miRNA profiling on 27 macrodissected cases of PCa by miRNA microarray. A total of 299 miRNAs were significantly dysregulated in high grade and advanced stage PCa. We demonstrated that PCa can be readily classified into high grade/stage and low-grade/stage groups by its global miRNA expression profile. Next, we examined the expression of several selected dysregulated miRNAs, including let-7c, miR-21, miR-27a, miR-30c, and miR-219, in PCa by ISH. The levels of miRNA expression in epithelial and stromal cells were scored semiquantitatively and compared with clinicopathological features, including age, race, Gleason score, stage, PSA recurrence, metastasis, hormone resistance and survival. We found that the expression of miR-30c and miR-219 were significantly down-regulated in PCa. miR-21 and miR-30c were significantly down-regulated in PCa in African Americans compared to Caucasian Americans. In addition, down-regulation of let-7c, miR-21, miR-30c, and miR-219 are associated with metastatic disease. Furthermore, down-regulation of miR-30c and let-7c are significantly associated with androgen-dependent PCa. In PCa stromal cells, let-7c downregulation is significantly associated with extraprostatic extension. Our data suggest that selected miRNAs may serve as potential biomarkers to predict cancer progression.

T cells play a critical role in host defense against viruses, intra- and extracellular microbes, and tumors. Because foreign antigen is presented amongst a vast majority of self-antigens, T cells have evolved the unique ability to discriminate "self" from "non-self" with high sensitivity and selectivity, enabling the elimination of foreign pathogens while largely avoiding self-reactivity. However, tissue-specific autoimmunity and tolerance to or eradication of cancer does not fit neatly into the self/non-self paradigm because the T cell responses in these situations are not directed to an exogenous pathogen, but rather most often to non-mutated self-proteins. Therefore, an important question is how the immune system establishes suitable thresholds that allow positively selected T cells to interact with selfligands in the periphery without causing overt activation. One hypothesis to explain how a T cell distinguishes among different types of self-ligands is the kinetic proof-reading theory, which relates signaling efficacy to the lifetime of the TCR (T cell receptor)-pMHC (peptide-major histocompatibility complex) interaction. More recently, T cell maturation associated signaling feedback pathways have also been hypothesized to play a role in T cell discrimination of between self-ligands. We are taking a variety of biophysical and cellular imaging approaches to determine how specific thresholds for T cell recognition of self-antigens are set. Our recent results [1] indicate that antitumor activity and autoimmunity are coupled and have a similar kinetic threshold; reducing autoimmunity cannot be accomplished without sacrificing efficacy of tumor killing. Therefore, an "optimal TCR affinity range" that leads to optimal tumor regression and minimal autoimmunity is elusive and treatment strategies focusing on increasing TCR affinities to a supraphysiological level has most likely little therapeutic benefit. Therefore, other approaches are needed to improve the balance between anti-tumor responses and autoimmunity. Our strategy to overcome this issue includes novel methods for careful biophysical engineering of tumor-specific TCRs to carefully balance tumorreactivity and autoimmunity. Furthermore, our recent preliminary data show that TCR-proximal signaling differs significantly between effector memory and central memory T cells due to differential constitutive activity and localization of signaling molecules. Understanding how activation signaling contributes to differences in memory T cell subset sensitivity may provide insight into how T cells can be manipulated to achieve optimal anti-tumor sensitivity. This could lead to adjuvants that target and enhance antigenspecific T cell anti-tumor efficacy. Together may lead to development of cancer immunotherapy approaches with improved outcomes

Introduction: The immunoregulatory protein T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) contributes towards T cell exhaustion in several chronic diseases, including melanoma [1]. NK cells from the latter were shown to be functionally impaired/exhausted, as they failed to proliferate, produce cytokines or kill target cells. In addition they down regulated activating receptors (NKG2D and NKp46) and upregulated inhibitory receptors (KIRB1, KIRNKAT2 and Tim-3). Notably Tim-3 blockade reversed this exhausted phenotype, implicating this molecule as a major checkpoint inhibitor in advanced melanoma [2]. To further evaluate NK cell phenotype and function as a consequence of progressive melanoma, we monitored NK cells from a large cohort of patients with stage I-IV melanoma tested the association between NK cell phenotype and clinicopathological variables associated with melanoma prognosis. Expression of MICA (NKG2D ligand) and HMGB1 (Tim-3 ligand) in the plasma/sera of our main cohort was also monitored in an independent validation cohort. Methods: NK cells were purified from the peripheral blood of melanoma patients. They were evaluated for the expression of activating and inhibitory receptors. Cytotoxicity was measured by Lamp-1 expression. IFN-gamma production was measured after 4h stimulation with rhIL-12. Proliferation was quantified by CFSE after 6 days in the presence of rhIL- 2. MICA and HMGB1 expression on patients' plasma/sera was measured by ELISA. Event-time distributions were estimated with the use of the Kaplan-Meier method. Two tailed t-test unpaired was used to compare samples from different stages. Results: NK cells gradually develop a phenotypic and functional profile consistent with progressive exhaustion, from stage I to stage IV characterized by: 1) up-regulation of inhibitory receptors (Tim-3, KIRB1 and KIRNKAT2); 2) down-regulation of activating receptors (NKG2D and NKp46); 3) loss of IFN-gamma production, proliferation and cytotoxicity. Interestingly, the expression of Tim-3 is higher, while the cytotoxicy and IFN-gamma production is reduced in patients with melanomas thicker than 1mm. Moreover, higher expression of Tim-3 and KIRB1, and a lower cytotoxic ability and T-bet expression is associated with local or distant metastases. Higher expression of MICA in the plasma was associated with worse prognosis, as was validated in an independent cohort (Figure 1). Conclusions: These data demonstrate that NK cells become progressively exhausted in the context of melanoma progression and that Tim-3 blockade possibly earlier in disease may have some benefit on innate immune function. Finally, our data suggest that soluble MICA is a potential prognostic marker which may contribute to the NK cell exhaustion through its interactions with NKG2D