The Impact of Next-generation Sequencing on Interobserver Agreement and Diagnostic Accuracy of Desmoplastic Melanocytic Neoplasms

Next-generation sequencing (NGS) is increasingly being utilized as an ancillary tool for diagnostically challenging melanocytic neoplasms. It is incumbent upon the pathology community to perform studies assessing the benefits and limitations of these tools in specific diagnostic scenarios. One of the most challenging diagnostic scenarios faced by skin pathologists involves accurate diagnosis of desmoplastic melanocytic neoplasms (DMNs). In this study, 20 expert melanoma pathologists rendered a diagnosis on 47 DMNs based on hematoxylin and eosin sections with demographic information. After submitting their diagnosis, the experts were given the same cases, but this time with comprehensive genomic sequencing results, and asked to render a diagnosis again. Identification of desmoplastic melanoma (DM) improved by 7%, and this difference was statistically significant ( P <0.05). In addition, among the 15 melanoma cases, in the pregenomic assessment, only 12 were favored to be DM by the experts, while after genomics, this improved to 14 of the cases being favored to be DM. In fact, some cases resulting in metastatic disease had a substantial increase in the number of experts recognizing them as DM after genomics. The impact of the genomic findings was less dramatic among benign and intermediate-grade desmoplastic tumors (BIDTs). Interobserver agreement also improved, with the Fleiss multirater Kappa being 0.36 before genomics to 0.4 after genomics. NGS has the potential to improve diagnostic accuracy in the assessment of desmoplastic melanocytic tumors. The degree of improvement will be most substantial among pathologists with some background and experience in bioinformatics and melanoma genetics.

Assessing vulnerability for future Zika virus outbreaks using seroprevalence data and environmental suitability maps

The 2015-17 Zika virus (ZIKV) epidemic in the Americas subsided faster than expected and evolving population immunity was postulated to be the main reason. Herd immunization is suggested to occur around 60-70% seroprevalence, depending on demographic density and climate suitability. However, herd immunity was only documented for a few cities in South America, meaning a substantial portion of the population might still be vulnerable to a future Zika virus outbreak. The aim of our study was to determine the vulnerability of populations to ZIKV by comparing the environmental suitability of ZIKV transmission to the observed seroprevalence, based on published studies. Using a systematic search, we collected seroprevalence and geospatial data for 119 unique locations from 37 studies. Extracting the environmental suitability at each location and converting to a hypothetical expected seroprevalence, we were able to determine the discrepancy between observed and expected. This discrepancy is an indicator of vulnerability and divided into three categories: high risk, low risk, and very low risk. The vulnerability was used to evaluate the level of risk that each location still has for a ZIKV outbreak to occur. Of the 119 unique locations, 69 locations (58%) fell within the high risk category, 47 locations (39%) fell within the low risk category, and 3 locations (3%) fell within the very low risk category. The considerable heterogeneity between environmental suitability and seroprevalence potentially leaves a large population vulnerable to future infection. Vulnerability seems to be especially pronounced at the fringes of the environmental suitability for ZIKV (e.g. Sao Paulo, Brazil). The discrepancies between observed and expected seroprevalence raise the question: "why did the ZIKV epidemic stop with large populations unaffected?". This lack of understanding also highlights that future ZIKV outbreaks currently cannot be predicted with confidence.

Fucosylation of HLA-DRB1 regulates CD4+ T cell-mediated anti-melanoma immunity and enhances immunotherapy efficacy

Immunotherapy efficacy is limited in melanoma, and combinations of immunotherapies with other modalities have yielded limited improvements but also adverse events requiring cessation of treatment. In addition to ineffective patient stratification, efficacy is impaired by paucity of intratumoral immune cells (itICs); thus, effective strategies to safely increase itICs are needed. We report that dietary administration of L-fucose induces fucosylation and cell surface enrichment of the major histocompatibility complex (MHC)-II protein HLA-DRB1 in melanoma cells, triggering CD4+ T cell-mediated increases in itICs and anti-tumor immunity, enhancing immune checkpoint blockade responses. Melanoma fucosylation and fucosylated HLA-DRB1 associate with intratumoral T cell abundance and anti-programmed cell death protein 1 (PD1) responder status in patient melanoma specimens, suggesting the potential use of melanoma fucosylation as a strategy for stratifying patients for immunotherapies. Our findings demonstrate that fucosylation is a key mediator of anti-tumor immunity and, importantly, suggest that L-fucose is a powerful agent for safely increasing itICs and immunotherapy efficacy in melanoma.

Revision of the Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis Classification Schema for Melanocytic Lesions: A Consensus Statement

IMPORTANCE

A standardized pathology classification system for melanocytic lesions is needed to aid both pathologists and clinicians in cataloging currently existing diverse terminologies and in the diagnosis and treatment of patients. The Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis (MPATH-Dx) has been developed for this purpose.

OBJECTIVE

To revise the MPATH-Dx version 1.0 classification tool, using feedback from dermatopathologists participating in the National Institutes of Health-funded Reducing Errors in Melanocytic Interpretations (REMI) Study and from members of the International Melanoma Pathology Study Group (IMPSG).

EVIDENCE REVIEW

Practicing dermatopathologists recruited from 40 US states participated in the 2-year REMI study and provided feedback on the MPATH-Dx version 1.0 tool. Independently, member dermatopathologists participating in an IMPSG workshop dedicated to the MPATH-Dx schema provided additional input for refining the MPATH-Dx tool. A reference panel of 3 dermatopathologists, the original authors of the MPATH-Dx version 1.0 tool, integrated all feedback into an updated and refined MPATH-Dx version 2.0.

FINDINGS

The new MPATH-Dx version 2.0 schema simplifies the original 5-class hierarchy into 4 classes to improve diagnostic concordance and to provide more explicit guidance in the treatment of patients. This new version also has clearly defined histopathological criteria for classification of classes I and II lesions; has specific provisions for the most frequently encountered low-cumulative sun damage pathway of melanoma progression, as well as other, less common World Health Organization pathways to melanoma; provides guidance for classifying intermediate class II tumors vs melanoma; and recognizes a subset of pT1a melanomas with very low risk and possible eventual reclassification as neoplasms lacking criteria for melanoma.

CONCLUSIONS AND RELEVANCE

The implementation of the newly revised MPATH-Dx version 2.0 schema into clinical practice is anticipated to provide a robust tool and adjunct for standardized diagnostic reporting of melanocytic lesions and management of patients to the benefit of both health care practitioners and patients.

Appropriate use criteria for ancillary diagnostic testing in dermatopathology: New recommendations for 11 tests and 220 clinical scenarios from the American Society of Dermatopathology Appropriate Use Criteria Committee

BACKGROUND

Appropriate use criteria (AUC) provide patient-centered physician guidance in test selection. An initial set of AUC was reported by the American Society of Dermatopathology (ASDP) in 2018. AUC reflect evidence collected at single timepoints and may be affected by evolving evidence and experience. The objective of this study was to update and expand AUC for selected tests.

METHODS

RAND/UCLA (RAND Corporation [Santa Monica, CA]/University of California Los Angeles) methodology used includes the following: (a) literature review; (b) review of previously rated tests and previously employed clinical scenarios; (c) selection of previously rated tests for new ratings; (d) development of new clinical scenarios; (e) selection of additional tests; (f) three rating rounds with feedback and group discussion after rounds 1 and 2.

RESULTS

For 220 clinical scenarios comprising lymphoproliferative (light chain clonality), melanocytic (comparative genomic hybridization, fluorescence in situ hybridization, reverse transcription polymerase chain reaction, telomerase reverse transcriptase promoter), vascular disorders (MYC), and inflammatory dermatoses (periodic acid-Schiff, Gömöri methenamine silver), consensus by panel raters was reached in 172 of 220 (78%) scenarios, with 103 of 148 (70%) rated "usually appropriate" or "rarely appropriate" and 45 of 148 (30%), "appropriateness uncertain."

LIMITATIONS

The study design only measures appropriateness. Cost, availability, test comparison, and additional clinical considerations are not measured. The possibility that the findings of this study may be influenced by the inherent biases of the dermatopathologists involved in the study cannot be excluded.

CONCLUSIONS

AUC are reported for selected diagnostic tests in clinical scenarios that occur in dermatopathology practice. Adhering to AUC may reduce inappropriate test utilization and improve healthcare delivery.

An ulcerating plaque of the lower lip

A middle-aged man presented to a cancer centre with a painful, ulcerating plaque of the lower lip, which had been diagnosed as squamous cell carcinoma. Computed tomography revealed increased focal metabolic activity in the lip, and histology revealed spirochaetes.

Clinical characteristics and prognostic factors of 70 patients with Sézary syndrome: a single-institutional experience at Moffitt cancer center

Sézary syndrome (SS) is a rare and aggressive leukemic variant of cutaneous T-cell lymphoma, with a median overall survival (OS) rate of 2-4 years. Few studies have described the clinical outcome of SS patients since 2012. We retrospectively analyzed 70 patients diagnosed with SS treated at a high-volume tertiary cancer center between 2000 and 2018. Overall survival at 1 and 5 years was 84.1% and 50.7%, respectively. Univariate analyses identified older age (>65 years) and male sex as poor prognostic factors. Five patients presented with circulating large granular lymphocytic proliferation and had a favorable prognosis. Targeted therapies were effective in treating refractory/relapsed SS patients with a durable response. Therapeutic advancements and the comprehensive treatments used in a multidisciplinary clinic improved OS rates.

The Role of External Genital Lesions in Human Immunodeficiency Virus Seroconversion Among Men Participating in a Multinational Study

BACKGROUND

Studies in women have shown an increased risk of human immunodeficiency virus (HIV) acquisition with prior human papilloma virus (HPV) infection; however, few studies have been conducted among men. Our objective was to assess whether HPV-related external genital lesions (EGLs) increase risk of HIV seroconversion among men.

METHODS

A total of 1379 HIV-negative men aged 18 to 70 years from the United States, Mexico, and Brazil were followed for up to 7 years and underwent clinical examination for EGLs and blood draws every 6 months. Human immunodeficiency virus seroconversion was assessed in archived serum. Cox proportional hazards and marginal structural models assessed the association between EGL status and time to HIV seroconversion.

RESULTS

Twenty-nine participants HIV seroconverted during follow-up. Older age was associated with a lower hazard of HIV seroconversion. We found no significant difference in the risk of HIV seroconversion between men with and without EGLs (adjusted hazard ratio, 0.94; 95% confidence interval, 0.32-2.74). Stratified analyses focusing on men that have sex with men found no association between EGLs and HIV seroconversion risk (hazards ratio, 0.63; 95% confidence interval, 0.00-1.86).

CONCLUSIONS

External genital lesions were not associated with higher risk for HIV seroconversion in this multinational population, although statistical power was limited as there were few HIV seroconversions. Results may differ in populations at higher risk for HIV.

LMD-03. Single cell analysis reveals how therapy remodels the tumor microenvironment in melanoma CNS metastases and uncovers a novel predictor of improved survival

We interrogated the microenvironment of 43 clinical samples from melanoma skin, brain (MBM) and leptomeningeal metastases (LMM) using single-cell RNA-seq analysis to determine how therapeutic intervention shaped the immune environment and affected patient survival. LMM is a poorly-characterized, devastating complication of late-stage disease, typically refractory to treatment and associated with dismal survival time. Analysis of serial specimens over the course of therapy demonstrated reductions in melanoma cells and macrophages, coupled with increased levels of T cells and dendritic cells in the CSF of a rare extraordinary responder, whereas typical poor survivors showed no improvement in T cell responses. In MBM patients, both targeted therapy and immunotherapy was associated with increased immune infiltrate. Treatment with targeted therapy was associated with an enrichment of CD8 T cells, while immunotherapy was associated with a more diverse lymphocyte landscape and higher numbers of antibody-producing cells. These findings were confirmed by multiplex-IF staining of patient specimens and using an immune-competent mouse model of MBM. Interestingly, a history of prior radiation therapy was associated with a diminished myeloid compartment. Although immune infiltrate was significantly lower in the brain compared to skin tumors, the phenotypic make-up of the lymphocyte compartment was quite similar, suggesting that the immune cells may have trafficked from the periphery to the brain post-therapy. Correlation analysis across the entire immune landscape identified the presence of a rare, novel population of dendritic cells (DC3s) to be correlated with increased overall survival, regardless of disease site/treatment. The presence of DC3s positively regulated the immune environment of both patient samples and preclinical melanoma models through modulation of activated T cells and MHC expression in the tumor. Overall, we present the first ever comprehensive single-cell atlas of the tumor microenvironment in melanoma CNS metastases in response to therapy.

OTME-17. Single cell characterization of the immune microenvironment of melanoma brain and leptomeningeal metastases

Melanoma brain metastases (MBM) and leptomeningeal metastases (LMM) are two manifestations of melanoma dissemination to the CNS with vastly different survival outcomes. Analysis of single cell RNA-Seq data from 43 clinical specimens has uncovered a distinct, immune-suppressed T cell landscape in the LMM microenvironment that is distinct to those of the brain and skin metastases. An LMM patient with an extraordinarily long survival and documented response to therapy demonstrated an immune repertoire that was distinct from those of typical poor survivors and more similar to CSF from non-LMM donors. Analysis of serial specimens over the course of therapy demonstrated reductions in melanoma cells and macrophages, coupled with increased levels of T cells and dendritic cells in the CSF of the extraordinary responder, whereas poor survivors showed no improvement in T cell responses. In MBM patients, targeted therapy and immunotherapy was associated with increased immune infiltrate, with similar T cell transcriptional diversity noted between skin metastases and MBM - suggestive of immune cell trafficking into the brain. Treatment with targeted therapy was associated with an enrichment of CD8 T cells. Immunotherapy was associated with a more diverse lymphocyte landscape and higher numbers of antibody-producing cells. These findings were confirmed by multiplexed staining of patient specimens and using an immune-competent mouse model of MBM. Correlation analysis across the entire immune landscape identified the presence of a rare, novel population of dendritic cells (DC3s) to be correlated with increased overall survival, regardless of disease site/treatment. The presence of DC3s positively regulated the immune environment of both patient samples and preclinical melanoma models through modulation of activated T cells and MHC expression in the tumor. Our study provides the first comprehensive atlas of two distinct sites of melanoma CNS metastases and identifies rare populations of cells that underlie the biology of this devastating disease.

Abstract 421: Characteristics of melanoma diagnosed in patients with underlying HIV infection

Background: Melanoma is diagnosed more frequently in patients living with HIV (PLWH) compared to the general US population and HIV-infected melanoma patients also experience higher cancer-specific mortality. The mechanisms underlying these outcome disparities are poorly understood, and data describing tumor pathology and non-mortality outcomes for melanoma patients with HIV are lacking.

Objective: To describe differences in tumor presentation and disease course among melanoma patients presenting with or without underlying HIV infection in the era of effective HIV therapy.

Methods: We conducted an initial retrospective chart review of 29 HIV+ and 29 HIV- patients, matched as possible to HIV+ patients on age and disease stage, who presented to Moffitt Cancer Center between 2004 and 2019. Data abstracted included patient demographics, tumor pathology, treatment details, and clinical outcomes.

Results: Certain melanoma pathology features differed by HIV status, with a higher prevalence of elevated mitotic rate (78.9% vs 41.2%, p=0.02) and vertical growth phase (90% vs 55%, p=0.02) in melanoma patients with HIV. Nearly all patients underwent lesion excision, but post-treatment complications were greater in PLWH (44.8% vs 24%, p=0.09). Among 16 patients who received systemic therapy after excision (HIV+ 6; HIV- 10), progressive disease was more frequent in PLWH (100% vs 30%, p=0.01), with further suggestion of higher severe side effect rates, defined as events interrupting systemic therapy (66.7% vs 30%; p=0.18). Despite these differences in progression, overall survival rate were similar in PLWH (79.3%) and uninfected patients (82.8%).

Conclusions: These preliminary results suggest that PLWH and melanoma experience a unique disease course. Higher prevalence of post-excision complications and disease progression following systemic therapy in particular warrant further attention as age-related cancers, such as melanoma, are expected to grow in the US HIV population in coming years.

Citation Format: Grace Wei, Sweta Sinha, Jane Messina, Anna E. Coghill. Characteristics of melanoma diagnosed in patients with underlying HIV infection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 421.

A rare concurrence of Muir-Torre-associated sebaceous carcinoma in the setting of a lipedematous scalp

Muir-Torre syndrome (MTS) a genetic disorder characterized by predisposition to cutaneous neoplasms. Lipedematous scalp is characterized by the presentation of a thick, sponge-like scalp due to the altered and increased deposition of adipose tissue. We present a case of Muir-Torre-associated sebaceous carcinoma of the scalp consistent with a lipedematous scalp.

CD8-positive cutaneous lymphoproliferation associated with large granular lymphocyte leukemia in a patient with X-linked agammaglobulinemia

Patients with primary immunodeficiency are at increased risk for malignancy, especially hematologic neoplasms. This paper reports a unique case of a 47-year-old man with X-linked agammaglobulinemia who presented with progressive asymptomatic violaceous papules and plaques on his face, hands, and trunk for 1 year. Skin biopsies revealed deep, nodular infiltrates of histiocytes and CD8-positive lymphocytes, with a CD4:CD8 ratio of 1:10. Laboratory studies showed cytopenias. Flow cytometry in the skin, blood, and bone marrow (BM) showed a CD3+/CD8+/CD57+ large granular lymphocyte population. BM biopsy showed 30% involvement with these atypical T-cells. T-cell gene rearrangement studies of skin, blood, and BM revealed identical T-cell clones. He was diagnosed with T-large granular lymphocyte leukemia (T-LGLL) with an associated CD8+ cutaneous lymphoproliferation. Skin involvement was suspected to represent infiltration by T-LGLL. However, co-existence of two lymphoproliferative disorders (LPDs), T-LGLL and CD8+ granulomatous LPD, remains a possibility. In general, cutaneous infiltrates associated with LGLL are rare and poorly understood. It has been suggested that they are markers of poor prognosis. Our case report describes skin, blood, and BM findings in an immunosuppressed patient with T-LGLL in detail. These findings have not yet been reported and their significance requires further investigation.

Noncanonical EphA2 Signaling Is a Driver of Tumor-Endothelial Cell Interactions and Metastatic Dissemination in BRAF Inhibitor‒Resistant Melanoma

Acquired BRAF/MAPK/extracellular signal‒regulated kinase inhibitor resistance in melanoma results in a new transcriptional state associated with an increased risk of metastasis. In this study, we identified noncanonical ephrin receptor (Eph) EphA2 signaling as a driver of the resistance-associated metastatic state. We used mass spectrometry‒based proteomic and phenotypic assays to demonstrate that the expression of active noncanonical EphA2-S897E in melanoma cells led to a mesenchymal-to-amoeboid transition driven by Cdc42 activation. The induction of mesenchymal-to-amoeboid transition promoted melanoma cell invasion, survival under shear stress, adhesion to endothelial cells under continuous-flow conditions, increased permeability of endothelial cell monolayers, and stimulated melanoma transendothelial cell migration. In vivo, melanoma cells expressing EphA2-S897E or active Cdc42 showed superior lung retention after tail-vain injection. Analysis of BRAF inhibitor‒sensitive and ‒resistant melanoma cells demonstrated resistance to be associated with a mesenchymal-to-amoeboid transition switch, upregulation of Cdc42 activity, increased invasion, and transendothelial migration. The drug-resistant metastatic state was dependent on histone deacetylase 8 activity. Silencing of histone deacetylase 8 led to the inhibition of EphA2 and protein kinase B phosphorylation, reduced invasion, and impaired melanoma cell-endothelial cell interactions. In summary, we have demonstrated that the metastatic state associated with acquired BRAF inhibitor resistance is dependent on noncanonical EphA2 signaling, leading to increased melanoma-endothelial cell interactions and enhanced tumor dissemination.

Effect of automated TIL quantification in early-stage melanoma on accuracy of standard T staging using AJCC guidelines

10076

Background: Patients diagnosed with early stage melanoma are at risk of recurrence and death. Adjuvant therapy decreases risk but incurs toxicity and expense. While tumor-infiltrating lymphocytes (TILs) improve prognosis, studies have shown conflicting results due, at least in part, to inter-observer variability. Thus, TILs are not included in standard American Joint Committee on Cancer (AJCC) staging. Here, we quantitatively analyze TILs in hematoxylin and eosin (H&E) melanoma images using two machine learning algorithms. Methods: H&E images were evaluated by two methods for patients with resectable stage I-III melanoma from Columbia (N = 81) and validated using samples from Geisinger and Moffitt (N = 128). For both methods, H&E images were manually annotated using open source software, QuPath, to specify tumor regions. For Method A, images were divided into patches and, for each patch, a probability was generated to detect lymphocytes. Patches above a set threshold were considered to be “TIL positive”. Ratio of TIL positive patches to total patches was assessed for every image. For Method B, a classifier was manually trained in QuPath and then applied on each image to determine the ratio of the areas of all immune cells to all tumor cells as previously published. Cutoff values to define high and low risk groups were established based on a test set and then validated in an independent cohort. Results: Both methods distinguished patients with visceral recurrence from those without for the Columbia training set (Method A p = .0015, Method B p = .043). Using Method A, Kaplan-Meier curve at the selected cutoff also correlated significantly with disease specific survival (DSS) for Columbia (p = .022) and was validated in the Geisinger/Moffitt (p = .046) cohort. Cox analysis using Method A showed that TIL status predicted DSS in the validation set (p = .047) and added significantly to depth and ulceration (HR = 3.43, CI: 1.047-11.257, p = .042). Conclusions: Both open source machine learning algorithms find significantly higher TILs in patients who do not develop metastasis. Notably, Method A may add to standard predictors, such as depth and ulceration. These results demonstrate the promise of computational algorithms to enhance visual grading, and suggest that digital TIL evaluation may add to current AJCC staging. [Table: see text]

Ipilimumab/nivolumab-induced pseudolymphoma in a patient with malignant melanoma

Combination therapy with ipilimumab and nivolumab is an adjuvant treatment approach for metastatic melanoma that boasts increased 3-year survival when compared with a single immunotherapy agent. Combination therapy, however, is associated with increased toxicities, especially cutaneous side-effects. Here we present a patient with metastatic melanoma and a sudden eruption of painful nodules on the face and arms 10 days after the administration of the fourth dose of combination ipilimumab/nivolumab. Biopsies demonstrated lymphoid hyperplasia, not clinically or pathologically consistent with an infectious, malignant or autoimmune etiology; a diagnosis of pseudolymphoma secondary to ipilimumab/nivolumab was made. After a steroid taper, the lesions resolved, and the patient was restarted on nivolumab monotherapy 2 weeks later without recurrence of symptoms or disease.

Cutaneous squamous cell carcinoma causing a rhinophymatous mass in a patient with clinically occult hypertrophic lupus erythematosus

Hypertrophic lupus erythematosus is a variant of discoid lupus erythematosus, which manifests as verrucous plaques and/or keratoacanthoma-like nodules on the face and arms. Diagnosis and treatment of hypertrophic lupus erythematosus can be challenging as it can resemble cutaneous squamous cell carcinoma clinically and histopathologically. Furthermore, cutaneous squamous cell carcinoma is a known complication of discoid lupus erythematosus. We present a diagnostically challenging case of a patient with a rapidly enlarging rhinophymatous mass and multiple keratoacanthoma-like lesions of the bilateral upper extremities whose work-up was initially equivocal. CD123 staining helped to elucidate a final diagnosis of cutaneous squamous cell carcinoma arising in a background of occult hypertrophic lupus erythematosus.

Abstract A73: Fucosylation in CD4+ T cell-mediated melanoma suppression

While immunotherapies have had a striking efficacy in melanoma patients, significant proportions of melanoma patients exhibit poor responsiveness to immunotherapies. Further understanding of immunoregulatory mechanisms is needed to improve immunotherapies. Previously, we discovered increasing tumor fucosylation in melanomas reduces tumor growth and metastasis (Lau et al., 2015). To identify tumor-infiltrating lymphocytes (TILs) affected by L-fucose, we profiled lymphocytes from syngeneic tumors of control- or fucose-fed mice tumors. Dietary supplementation of L-fucose increased TILs by ~10-50-fold. Of total TILs, CD3+ T cells (including CD4+ and CD8+ T cells) doubled. L-fucose did not trigger tumor suppression in immune-deficient mouse melanoma models, indicating the immune system’s requirement for L-fucose-triggered suppression. Immunodepletion of CD4+ or CD8+ T cells during L-fucose treatment revealed that CD4+ T cells are crucial for tumor suppression. CD4+ T-cell depletion abrogated infiltration of NK, dendritic, and CD8+ T cells in the tumors, implicating these populations as downstream effectors of fucosylation- and CD4+ T cell-triggered tumor suppression. To identify proteins on melanomas contributing to fucosylation-triggered immune responses, we performed mass spectrometric analysis of all fucosylated proteins in melanoma and identified 2 MHC proteins, HLA-A and HLA-DRB1, as fucosylated. Knockdown of HLA- DRB1 and HLA-A in vivo revealed HLA-DRB1 is required for L-fucose-mediated tumor suppression, and notably, for recruitment of CD4+ T cells. We further investigated how fucosylation affects CD4+ T-cell biology using CD4+ T cells isolated from healthy donors, which we pharmacologically modulated fucosylation. The roles of fucosylation on tumor vs. CD4+ T cells and clinical utility/implications for melanoma patients will be discussed. Our data show how increased fucosylation drives tumor suppression through CD4+ T cells, and support the potential of dietary L-fucose to boost immunity in melanomas.

Citation Format: Daniel K. Lester, Pasquale Innamarato, Krithika Kodumudi, Gregory Watson, Matt Mercurio, Shari Pilon-Thomas, Jane Messina, Susan McCarthy, Eric Lau. Fucosylation in CD4+ T cell-mediated melanoma suppression [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A73.

Neoadjuvant BRAF-targeted therapy in regionally advanced and oligometastatic melanoma

Current management of locoregional and oligometastatic melanoma is typically with surgery; however, some patients are unable to undergo resection due to location/size of their tumors and/or the anticipated morbidity of the surgery. While there are currently no established guidelines for neoadjuvant therapy in melanoma, neoadjuvant BRAF-targeted therapy may make resection more feasible. A retrospective analysis was conducted of 23 patients with BRAFV600-mutant, stage III/IV melanoma treated with BRAF-targeted therapy prior to surgery, with no adjuvant treatment. Surgical specimens, preoperative imaging, and clinical outcomes were evaluated. Results: Ten of 23 patients (44%) attained a pathologic complete response (pCR), with no correlation between RECIST response based on preoperative imaging and pathologic response. After a median of 43-month follow-up, only 1 patient (10%) with a pCR recurred, while 8 of 13 (62%) patients without a pCR recurred. Patients with a pCR had significantly improved relapse-free (RFS) and overall survival (OS) compared to patients with residual tumor. Neoadjuvant BRAF-targeted therapy is associated with a high pCR rate in patients with stage III-IV melanoma, which may correlate with improved RFS and OS.

An erythematous facial rash

Two months of treatment with doxycycline provided no improvement. A biopsy of the patient's cheek led to a proper diagnosis.

Merkel Cell Carcinoma, Version 1.2018, NCCN Clinical Practice Guidelines in Oncology

This selection from the NCCN Guidelines for Merkel Cell Carcinoma (MCC) focuses on areas impacted by recently emerging data, including sections describing MCC risk factors, diagnosis, workup, follow-up, and management of advanced disease with radiation and systemic therapy. Included in these sections are discussion of the new recommendations for use of Merkel cell polyomavirus as a biomarker and new recommendations for use of checkpoint immunotherapies to treat metastatic or unresectable disease. The next update of the complete version of the NCCN Guidelines for MCC will include more detailed information about elements of pathology and addresses additional aspects of management of MCC, including surgical management of the primary tumor and draining nodal basin, radiation therapy as primary treatment, and management of recurrence.

Abstract LB-085: PTPN11 plays oncogenic roles and is a therapeutic target for BRAF wild-type melanomas

Melanoma is one of the most highly mutated cancer types. To identify functional drivers of melanoma, we searched for cross-species conserved mutations utilizing a mouse melanoma model driven by loss of PTEN and CDKN2A, and identified mutations in Kras, Erbb3, and Ptpn11. PTPN11 encodes the SHP2 protein tyrosine phosphatase (PTP) that activates the RAS/RAF/MAPK pathway. Although PTPN11 is an oncogene in leukemia, lung, and breast cancers, its roles in melanoma are not clear. In this study, we found that PTPN11 is frequently activated in human melanoma specimens and cell lines and is required for full RAS/RAF/MAPK signaling activation in BRAF wild-type (either NRAS mutant or wild-type) melanoma cells. PTPN11 played oncogenic roles in melanoma by driving anchorage-independent colony formation and tumor growth. In Pten and Cdkn2a null mice, tet-inducible and melanocyte-specific PTPN11 E76K expression significantly enhanced melanoma tumorigenesis. Melanoma cells derived from this mouse model showed doxycycline-dependent tumor growth in nude mice. Silencing PTPN11 E76K expression by doxycycline withdrawal caused regression of established tumors by induction of apoptosis and senescence, and suppression of proliferation. Moreover, the PTPN11 inhibitor (SHP099) also caused regression of NRAS Q61K-mutant melanoma. Using a quantitative tyrosine phosphoproteomics approach, we identified GSK3α/β as one of the key substrates that were differentially tyrosine-phosphorylated in these experiments modulating PTPN11. This study identifies PTPN11 as an oncogenic driver and a novel and actionable therapeutic target for BRAF wild-type melanoma.

Citation Format: Kristen Hill, Jane Messina, Jie Wu, Charles E. Chalfant, Minjung Kim. PTPN11 plays oncogenic roles and is a therapeutic target for BRAF wild-type melanomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-085.

Abstract 3800: HDAC8 regulates plasticity and escape from therapy in BRAF mutant melanoma

Melanoma cells are highly plastic and have the ability to switch to a dedifferentiated, invasive phenotype in response to multiple stimuli. We here show that exposure to melanoma cell lines and patient specimens to multiple stresses including BRAF-MEK inhibitor therapy, hypoxia and UV-irradiation leads to an increase in HDAC8 expression/activity, and in turn, the adoption of a drug-resistant, invasive phenotype. Systems level analyses using mass spectrometry-based phosphoproteomics and RNA-Seq demonstrated HDAC8 to be involved in pathways that regulated cell cycle entry, ribosome function, RNA binding, regulation of the cytoskeleton and MAPK pathway signaling. Introduction of HDAC8 into drug-naïve melanoma cells conveyed resistance in vitro and in in vivo xenograft models. The HDAC8-mediated BRAF inhibitor resistance was mediated through upstream receptor tyrosine kinase (RTK) activation, Ras/CRAF/MEK/ERK signaling and the suppression of apoptosis through increased stabilization of Mcl-1 and the inhibition of pro-apoptotic BIM. Among the multiple RTKs increased by HDAC8, EGFR emerged as a direct transcriptional target, and it was found that EGFR inhibition could overcome HDAC8-mediated tolerance to BRAF inhibition. Although it is known that HDACs primarily function at the histone level, they can also regulate signaling through the modulation of cytoplasmic protein acteylation. In line with this, we observed that HDAC8 introduction decreased the acetylation of c-JUN, leading to an increase in its transcriptional activity and the enrichment for an AP-1 gene signature. Mutation of putative acetylation sites in c-JUN (K268R, K271R, K273R) reduced the transcriptional activation of c-JUN in melanoma cells and conveyed resistance to BRAF inhibition through increased MAPK pathway activity. In vivo xenograft studies confirmed the key role of HDAC8 in therapeutic adaptation, with either a pan-HDAC inhibitor (panobinostat) or an HDAC8 inhibitor (PCI-34051) enhancing the durability of response to BRAF inhibitor therapy. We have thus identified HDAC8 as a key driver of phenotype switching in melanoma that regulates the responses to multiple cellular stresses and conveys resistance to BRAF inhibition. Our studies demonstrate that isoform-specific HDAC8 inhibitors could be an excellent strategy to limit the adaptation of melanoma cells to multiple stresses and therapeutic interventions, including the BRAF-MEK inhibitor combination.

Citation Format: Michael Emmons, Fernanda Flores, John Koomen, Edward Seto, Jane Messina, Eric Lau, Jonathan Licht, Keiran Smalley. HDAC8 regulates plasticity and escape from therapy in BRAF mutant melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3800.

Testicular tissue cryopreservation: 8 years of experience from a coordinated network of academic centers

STUDY QUESTION

Is it feasible to disseminate testicular tissue cryopreservation with a standardized protocol through a coordinated network of centers and provide centralized processing/freezing for centers that do not have those capabilities?

SUMMARY ANSWER

Centralized processing and freezing of testicular tissue from multiple sites is feasible and accelerates recruitment, providing the statistical power to make inferences that may inform fertility preservation practice.

WHAT IS KNOWN ALREADY

Several centers in the USA and abroad are preserving testicular biopsies for patients who cannot preserve sperm in anticipation that cell- or tissue-based therapies can be used in the future to generate sperm and offspring.

STUDY DESIGN, SIZE, DURATION

Testicular tissue samples from 189 patients were cryopreserved between January 2011 and November 2018. Medical diagnosis, previous chemotherapy exposure, tissue weight, and presence of germ cells were recorded.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human testicular tissue samples were obtained from patients undergoing treatments likely to cause infertility. Twenty five percent of the patient's tissue was donated to research and 75% was stored for patient's future use. The tissue was weighed, and research tissue was fixed for histological analysis with Periodic acid-Schiff hematoxylin staining and/or immunofluorescence staining for DEAD-box helicase 4, and/or undifferentiated embryonic cell transcription factor 1.

MAIN RESULTS AND THE ROLE OF CHANCE

The average age of fertility preservation patients was 7.9 (SD = 5) years and ranged from 5 months to 34 years. The average amount of tissue collected was 411.3 (SD = 837.3) mg and ranged from 14.4 mg-6880.2 mg. Malignancies (n = 118) were the most common indication for testicular tissue freezing, followed by blood disorders (n = 45) and other conditions (n = 26). Thirty nine percent (n = 74) of patients had initiated their chemotherapy prior to undergoing testicular biopsy. Of the 189 patients recruited to date, 137 have been analyzed for the presence of germ cells and germ cells were confirmed in 132.

LIMITATIONS, REASONS FOR CAUTION

This is a descriptive study of testicular tissues obtained from patients who were at risk of infertility. The function of spermatogonia in those biopsies could not be tested by transplantation due limited sample size.

WIDER IMPLICATIONS OF THE FINDINGS

Patients and/or guardians are willing to pursue an experimental fertility preservation procedure when no alternatives are available. Our coordinated network of centers found that many patients request fertility preservation after initiating gonadotoxic therapies. This study demonstrates that undifferentiated stem and progenitor spermatogonia may be recovered from the testicular tissues of patients who are in the early stages of their treatment and have not yet received an ablative dose of therapy. The function of those spermatogonia was not tested.

STUDY FUNDING/COMPETING INTEREST(S)

Support for the research was from the Eunice Kennedy Shriver National Institute for Child Health and Human Development grants HD061289 and HD092084, the Scaife Foundation, the Richard King Mellon Foundation, the Departments of Ob/Gyn & Reproductive Sciences and Urology of the University of Pittsburgh Medical Center, United States-Israel Binational Science Foundation (BSF), and the Kahn Foundation. The authors declare that they do not have competing financial interests.

Phase I study of vemurafenib (VEM) and cobimetinib (COB) with heat shock protein 90 (HSP90) inhibitor XL888 in advanced BRAFV600 mutant melanoma

9553

Background: Resistance to BRAF+MEK inhibitors(i) in BRAF-mutant melanoma is common. Multiple resistance mechanisms involve HSP90 clients, and a phase 1 study of VEM with XL888 showed PFS rates similar to the combination of BRAF+MEKi (Eroglu, CCR, 2018). Methods: Combination of VEM (960 mg PO BID) and COB (60 mg QD for 21 of 28 days) with escalating dose cohorts of XL888 (30, 45, 60 or 90 mg PO twice weekly) was investigated in a phase 1 study of advanced melanoma, with a modified Ji dose escalation design. Dose-limiting toxicity (DLT) was defined as related grade ≥3 adverse event or inability to deliver 75% of XL888 in first 4 weeks. Results: 25 pts (9 female, median age 62, 15 with M1C disease, 6 with prior anti-PD-1 therapy) were enrolled. After 2 DLTs (rash and acute kidney injury) in first cohort, a lower dose of VEM 720 mg BID and COB 40 mg, with the same XL888 cohorts was investigated. 3 DLTs (rash) in 12 pts were observed in the XL888 60 mg cohort, which was determined as the maximum tolerated dose. Most common grade 3 toxicities included diarrhea (8), hypertension (6), rash (5), alkaline phosphate/GGT elevation (4). 11 patients required dose reductions of VEM and/or COB. Objective responses (PR/CR) were observed in 18 of 25 pts (72%; 95% CI: 51-88%). Median PFS was 8.1 months (4.7 – NA); median overall survival was not reached, with 1-year OS of 71% (45-86%). Single cell RNA-Seq (10X genomics) was performed on baseline and on-treatment tumor biopsies; 8 days of treatment was associated with an increase in immune cell influx (CD4+ and CD8+) and a decrease in number of melanoma cells. At day 8, one patient (now without progression for nearly 2 years) had no tumor cells remaining with only immune cells and stromal fibroblasts left. Further analyses will be presented. Serial plasma BRAF circulating tumor (ct)DNA levels were obtained, with decrease in ctDNA levels corresponding with response and 83% of patients with disease progression showing an elevation in ctDNA from baseline. Conclusions: VEM/COB plus XL888 had significant toxicity, requiring dose-reductions that may have contributed to the low PFS rate despite high response rate. Caution must be used in combination of BRAF+MEKi with other agents. Clinical trial information: NCT02721459.

Association Between Recent Ultraviolet Radiation Exposure and Cutaneous Beta Human Papillomavirus Infection

Keratinocyte carcinoma (KC), comprised of squamous cell carcinoma and basal cell carcinoma, is the most common cancer in the United States. The effects of ultraviolet radiation (UVR), an established risk factor for KC, on cutaneous human papillomavirus (HPV) infection, a suggested risk factor currently under investigation, are not well established. We assessed cross sectional associations between UVR exposure and cutaneous beta HPV infection, using data obtained from the Viruses in Skin Cancer Study (VIRUSCAN), a prospective cohort study conducted at the Moffitt Cancer Center and the University of South Florida. Methods: Eyebrow hairs (EBH), skin swabs (SSW) and spectrophotometer-based measurements of recent UVR exposure were obtained from 1,179 skin cancer screening patients enrolled in the VIRUSCAN study. Viral DNA was measured using a multiplex PCR assay for 46 beta HPV types in both skin swab samples and eyebrow hair follicles. Logistic regression was used to examine the association between UVR exposure and cutaneous HPV infection in individual sites. Ordinal logistic regression was used to examine the effect of UVR exposure on the trend of having the same HPV infection across two sites, adjusted for age and sex. Results: Patients with higher UVR exposure were more likely to test positive for beta HPV 19, 47, 100 and 145 in EBH. In SSW, beta 38, 49, 76, 100, 124 were positively associated with UVR exposure. When considering viral infection across two sites, we found UVR exposure to be significantly associated with the odds of having infection in both EBH and SSW for beta HPV 19 (OR = 1.12, 95% CI: 1.03–1.23, p-trend = 0.04), 38 (OR = 1.08, 95% CI: 1.04–1.13, p-trend &lt; 0.01), 76 (OR = 1.06, 95% CI: 1.00–1.12, p-trend = 0.01), and 100 (OR = 1.10, 95% CI: 1.04–1.17, p-trend = 0.01). Conclusions: UVR exposure is positively associated with beta cutaneous HPV at the type level, in both individual sites and across skin swab and eyebrow hair. Future research is needed to better understand the biological mechanisms mediating the associations between UVR and cutaneous HPV infection.

Abstract 2387: The oncogenic role and therapeutic potential of PTPN11 in melanoma

The RAS/RAF/MEK/ERK signaling pathway, which is intricately regulated by multiple proteins including PTPN11 (Tyrosine-Protein Phosphatase Non-Receptor Type 11, encoding SHP2), is frequently activated in melanoma. Although implicated as an oncogene in multiple cancer types, the oncogenic role of PTPN11 has not been established in melanoma. Recently, we preformed whole exome sequencing on tumors generated by a mouse model driven by loss of PTEN and CDKN2A (INK4A/ARF) and identified several conserved cross-species orthologous mutations in Kras, Erbb3, and Ptpn11. In this study, we addressed the functional roles of PTPN11 in melanoma tumorigenesis and tumor maintenance; as well as, PTPN11's effect on the RAS/RAF/MEK/ERK signaling pathway and its activation status in human melanoma.

PTPN11 can be activated by receptor tyrosine kinases (RTKs) or by point mutations. We observed activating phosphorylation on Tyr 542 of PTPN11 in 40% (n=15/38) of melanoma specimens and the majority of human melanoma cell lines (n=14), supporting frequent activation of PTPN11 in human melanoma even though the mutation rate is low (1~3%). PTPN11 knock-down suppressed ERK activation in NRAS mutant and BRAF/NRAS wild-type melanoma cells, but not in BRAF mutant cells. Moreover, we have shown that expression of active PTPN11E76K mutant drives soft-agar colony growth in vitro, tumor growth in nude mice, RAS/RAF/MEK/ERK activation, and resistance to MEK inhibition. Alternatively, knock-down of Ptpn11 reduces colony growth and ERK activation. We generated a tet-inducible, melanocyte-specific, PTPN11E76K transgenic mouse model in a PTEN and CDKN2A null background and observed melanoma formation. Implantation of melanoma cells derived from this model showed doxycycline dependent tumor growth in nude mice. Doxycycline withdrawal and subsequent extinction of PTPN11E76K caused regression of established tumors, supporting the tumor maintenance role of PTPN11. Subsequently, tumor tissue from this model underwent phosphor-tyrosine proteomic analysis to identify downstream effectors of PTPN11's protein tyrosine phosphatase activity. The proteins identified in this analysis are currently being confirmed. These data support the oncogenic roles of PTPN11 in melanoma by regulating RAS/RAF/MAPK pathway activation and the value of PTPN11 as a novel and actionable therapeutic target.

Citation Format: Kristen Suzanne Hill, Evan Roberts, Ellen Marin, Xue Wang, Jamie Teer, Jane Messina, Jerry Wu, Minjung Kim. The oncogenic role and therapeutic potential of PTPN11 in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2387.

Abstract 3025: Ligand-independent EphA2 signaling drives an amoeboid phenotype that promotes melanoma brain metastasis development

The majority of melanoma patients treated with BRAF inhibitors (BRAFi) ultimately develop resistance and fail on therapy. It has previously been shown that BRAFi resistance is highly correlated with the adoption of a strongly invasive phenotype through ligand-independent EphA2 signaling.

In this study, we used comprehensive mass spectrometry-based proteomic approaches to delineate the global signaling changes associated with the aggressive phenotype driven by ligand-independent EphA2 signaling. Preliminary data have identified new signaling adaptations associated with a mesenchymal-to-amoeboid transition (MAT) phenotype, which was confirmed in 3D collagen cultures. Functional experiments demonstrated that the amoeboid phenotype promoted cell migration and invasion, which was mediated through the interaction of EphA2 and CDC42. These findings were confirmed by expressing a constitutively activated form of CDC42. BRAFi resistant cell lines also exhibited the MAT phenotype and were more invasive compared to their treatment-naïve counterparts, in line with their dependence upon ligand-independent EphA2 signaling following BRAFi selection pressure.

To further demonstrate the metastatic potential of these amoeboid cells driven by ligand-independent EpHA2 signaling in vivo, we performed intracardiac injections in mice with cell lines expressing either EpHA2 S897A (inactive) or S897E (constitutively active phosphomimetic). Interestingly, we found a preferential homing of EphA2 S897E cells to the brain, but no difference in metastasis to other organs including the lung and liver. An analysis of brain metastasis specimens from patients failing BRAF and BRAF/MEK inhibitor therapy showed strong staining for the amoeboid phenotype marker EphA2.

To investigate whether the amoeboid phenotype may confer a survival advantage in circulation, we carried out shear stress assays. These experiments demonstrated that the amoeboid phenotype driven by ligand-independent EphA2 signaling promoted the survival of melanoma cells under shear stress. Cell attachment assays, trans-endothelial invasion assays and vascular permeability assays show that these cells are better suited to attach to and permeate an endothelial monolayer. We further show that inhibiting PI3K reversed the amoeboid phenotype and limited the EphA2-driven invasive capacity.

In summary, we show for the first time that BRAFi resistance is associated with the adoption of an MAT phenotype that increases the metastatic seeding of melanoma cells to the brain, which can be reversed through inhibition of PI3K signaling.

Citation Format: Chao Zhang, Inna Smalley, Ritin Sharma, Michael Emmons, Jane Messina, John Koomen, Keiran Smalley. Ligand-independent EphA2 signaling drives an amoeboid phenotype that promotes melanoma brain metastasis development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3025.

Abstract 4364: R-Ras activation cooperates with BRAF mutation in melanoma tumorigenesis

The Ras family of small GTP binding proteins are tightly regulated through a complex network of proteins. In melanoma the Ras signaling pathway is frequently activated by mutations in NRAS (20%), KRAS (2%) and HRAS (1%); alternatively, Ras can also be activated by the inactivation of Ras GTPase activating proteins (RasGAPs) such as NF1, RASA1, and RASA2. Recently, we observed that inactivation of RASA1 (RAS p21 protein activator 1, also called p120RasGAP) suppressed melanoma via its RasGAP activity toward the R-Ras (related RAS viral (r-ras) oncogene homolog) isoform and that R-Ras was required to promote anchorage-independent growth driven by RASA1 inactivation. Moreover, a low level of RASA1 mRNA expression is associated with decreased overall survival in melanoma patients with BRAF mutations. Based on these observations, we hypothesized that, although not mutated, R-Ras is activated in melanoma by inactivation of RasGAPs and that BRAF activation cooperates with this RasGAP/R-Ras pathway activation in melanoma tumorigenesis.

In this study, we addressed the importance of R-Ras, a previously less appreciated member of the Ras small GTPases family, in melanoma tumorigenesis. We observed frequent activation of R-Ras in BRAF mutant human melanoma cell lines and human melanoma specimens. In addition, RNAi-mediated knockdown of R-Ras suppressed anchorage-independent colony growth and tumor growth. Of the 3 major RAS effector pathways, specifically MEK/ERK, AKT and Ral-A, reduced R-Ras expression suppressed Ral-A activation, which may explain the mechanism of Ral-A activation in BRAF mutant melanoma. Interestingly, anchorage-independent growth driven by R-Ras activation downstream of RASA1 inactivation was suppressed by both genetic (siRNA targeting Ral-A) and pharmacological (Ral inhibitor BQU57) inhibition of Ral-A. To further investigate the impact of RASA1 loss, and thus R-Ras activation, on BRAF mutant melanoma development in vivo, we generated a Rasa1L/L; BRAFCA/CA; Tyr-CreERT2 mouse model in which treatment with 4OHT results in expression of constitutively activated mutant BRAF and deletion of Rasa1 in melanocytic lineage cells. Preliminary analysis shows hyperpigmentation of the ear, tail, and foot pad in Rasa1L/L BRAFCA/CA mice compared to Rasa1+/+ BRAFCA/CA littermates; as well as, the development of cutaneous melanoma in Rasa1 deficient mice. Tumors generated in this animal model will be analyzed to determine the extent of R-Ras and Ral-A activity in vivo. This study demonstrates the importance of the RASA1/R-Ras/Ral-A signaling pathway in BRAF mutant melanoma and supports the possible combinatorial treatment strategy targeting both the BRAF/MAPK and Ral signaling pathways.

Citation Format: Kristen S. Hill, Evan R. Roberts, Xue Wang, Youngchul Kim, Jane Messina, Minjung Kim. R-Ras activation cooperates with BRAF mutation in melanoma tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4364.

Abstract B12: The importance of the RASA1/R-Ras/Ral-A signaling axis in melanoma tumorigenesis

The Ras family of small GTP-binding proteins is frequently activated by mutations, including NRAS (20%), KRAS (2%), and HRAS (1%), in melanoma. In addition to mutations, Ras isoforms can also be activated by the inactivation of Ras GTPase activating proteins (RasGAPs), such as NF1, RASA1, and RASA2. In our recent study, we observed that the inactivation of RASA1 (RAS p21 protein activator 1, also called p120RasGAP) suppressed melanoma via its RasGAP activity toward the R-Ras (related RAS viral (r-ras) oncogene homolog) isoform. We hypothesized that, although not mutated, R-Ras is activated in melanoma through the inactivation of RasGAPs and that RasGAP/R-Ras pathway activation cooperates with BRAF activation in melanoma tumorigenesis.

In this study, we addressed the importance of R-Ras, a previously less-appreciated member of the Ras family, in melanoma tumorigenesis and investigated the molecular mechanisms underlying R-Ras signaling in BRAF mutant melanoma. We observed frequent activation of R-Ras in BRAF mutant human melanoma cell lines. In addition, RNAi-mediated reduced expression of R-Ras suppressed anchorage-independent colony growth and tumor growth. Moreover, among the three major RAS effector pathways, reduced R-Ras expression suppressed Ral-A activation, which may explain the mechanism of Ral-A activation in BRAF mutant melanoma. Interestingly, anchorage-independent growth driven by RASA1 inactivation and subsequent R-Ras activation was suppressed by both genetic (siRNA targeting Ral-A) and pharmacologic (Ral inhibitor BQU57) inhibition of Ral-A. To further investigate the impact of RASA1 loss, and thus R-Ras activation, on BRAF mutant melanoma development in vivo, we generated a RASA1 L/L; BRAF CA/CA; Tyr-CreERT2 mouse model in which treatment with 4OHT results in the expression of constitutively activated mutant BRAF and the deletion of RASA1 in melanocytic lineage cells. Preliminary analysis shows hyperpigmentation of the ear, tail, and foot pad in RASA1 L/L BRAF CA/CA mice compared to RASA1 +/+ BRAF CA/CA littermates and the development of melanoma in RASA1 mutant mice. This study demonstrates the importance of the RASA1/R-Ras/Ral-A signaling pathway in BRAF mutant melanoma and supports the possible combinatorial treatment strategy targeting both the BRAF/MAPK and Ral signaling pathways.

Citation Format: Kristen S. Hill, Xue Wang, Evan R. Roberts, Youngchul Kim, Jane Messina, Minjung Kim. The importance of the RASA1/R-Ras/Ral-A signaling axis in melanoma tumorigenesis [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr B12.

Abstract A04: Cross-species oncogenomics approach identifies PTPN11 as an oncogene and potential therapeutic target in melanoma

Melanoma is a deadly disease carrying many genetic mutations. A major challenge to the development of effective targeted therapies in melanoma is the identification of true “driver” mutations among numerous “passenger” alterations. Several previous studies support using cross-species comparative oncogenomic approaches for cancer gene discovery. Specifically, it has been shown that mice and humans share several genetic events in the development of cancer and that these events that are conserved across different species may point to functionally important and evolutionary conserved alterations targeting “driver” genes. Recently, we analyzed melanoma genomes from a mouse model driven by the loss of PTEN and CDKN2A (INK4A/ARF), commonly observed alterations in human melanoma patients, by whole-exome sequencing. This study identified several conserved cross-species orthologous mutations in Kras, Erbb3, and Ptpn11. In this study, we addressed the functional roles of PTPN11 in melanoma tumorigenesis and tumor maintenance, its effect on RAS/RAF/MEK/ERK signaling pathway, and its activation status in human melanoma.

Melanoma displays frequent activation of the RAS/RAF/MEK/ERK signaling pathway, which is intricately regulated by multiple proteins including PTPN11 (Tyrosine-Protein Phosphatase Non-Receptor Type 11, encoding SHP2). Although implicated as an oncogene in multiple cancer types, the oncogenic role of PTPN11 has not been fully established in melanoma. PTPN11 can be activated by receptor tyrosine kinases (RTKs) and/or by point mutations. Although the mutation rate is low (1~3%), we observed activating phosphorylation on Tyr 542 of PTPN11 in 40% (n=15/38) of melanoma specimens and the majority of human melanoma cell lines (n=14), indicating the potential frequent activation of PTPN11 in human melanoma. PTPN11 knock-down suppressed ERK activation in NRAS mutant (WM1361A, 1366, 1346) and BRAF/NRAS wt (WM3211, MeWo, CHL1) melanoma cells, but not in BRAF mutant (1205Lu, IGR1, 983C) cells. Moreover, we have shown that the expression of active PTPN11 E76K mutant drives soft-agar colony growth in vitro, tumor growth in nude mice, RAS/RAF/MEK/ERK activation, and resistance to MEK inhibition, whereas knock-down of Ptpn11 reduces colony growth and ERK activation. We generated a tet-inducible, melanocyte-specific, PTPN11 E76K transgenic mouse model in a Pten and Cdkn2a null background and observed melanoma formation. Implantation of melanoma cells derived from this model showed doxycycline-dependent tumor growth in nude mice; additionally, withdrawal of doxycycline and subsequent extinction of PTPN11 E76K caused regression of established tumors, supporting a tumor-maintenance role of PTPN11. These data support the oncogenic roles of PTPN11 in melanoma by regulating RAS/RAF/MAPK pathway activation and the value of PTPN11 as a novel and actionable therapeutic target.

Citation Format: Kristen S. Hill, Xue Wang, Evan R. Roberts, Ellen M. Marin, Jamie K. Teer, Youngchul Kim, Jane Messina, Jie Wu, Minjung Kim. Cross-species oncogenomics approach identifies PTPN11 as an oncogene and potential therapeutic target in melanoma [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr A04.

Second Opinion Reviews for Cancer Diagnoses in Anatomic Pathology: A Comprehensive Cancer Center's Experience

AIM

The objective of this study was to define the rates of discrepancy between outside pathological diagnoses and secondary reviews.

MATERIALS AND METHODS

We assessed the rates of discordance between outside diagnoses and secondary reviews, categorizing by organ site and minor or major (affecting patient care) discordances.

RESULTS

A total of 9,289 consecutive surgical pathology (SP) and cytopathology (CP) cases reviewed in 2015 were identified. For 8,191 outside SP cases reviewed, the overall discordance rate (DR) was 14.2% (2.2% major, 12.0% minor). Specifically, neuropathology had the highest DR (10.9%), cutaneous and breast the lowest (1.1% each). Among 1,098 CP cases, the total DR was 13.7% (3.0% major, 10.7% minor). The majority of CP cases (1,066) were non-gynecological and had a total DR of 13.4% (2.7% major, 10.7% minor).

CONCLUSION

While major DR was low, certain subspecialties had high DRs. This project can help identify areas where focused education could help improve pathological diagnostic accuracy for cancer.

Eccrine squamous syringometaplasia in an allogenic stem cell transplant patient undergoing chemotherapy

Eccrine squamous syringometaplasia (ESS) is a rare finding defined as metaplastic change of the cuboidal epithelial cells of eccrine glands into two or more layers of squamous epithelial cells. We present a patient who developed ESS after induction of CLAG chemotherapy [2-Chlorodeoxyadenosine (2-CdA) with cytarabine (Ara-C) and (granulocyte-colony stimulating factor) G-CSF] for management of the blast crisis of his chronic myelogenous leukemia (CML). Our patient's ESS eruption presented with a variety of morphologies, thus multiple skin biopsies were taken to determine the possible diagnosis(es). All skin biopsies showed ESS and the eruption resolved with topical corticosteroids after CLAG therapy was finished.

Abstract 365: Cross-talk between BRAF and Hippo/YAP1 signaling in melanoma

Hippo/YAP1 signaling pathway is a tumor suppressive pathway that controls the organ size by modulating the cell growth, proliferation and apoptosis and is conserved from Drosophila to mammals. In mammals, the Hippo tumor suppressor pathway consists of cascade of kinases in which MST1/2 phosphorylates and activates LATS1/2. The latter phosphorylates the oncogenic transcriptional coactivators YAP1 and TAZ, leading to their cytoplasmic retention by 14-3-3 proteins and/or degradation. Inactivation of MST and LATS kinases allows YAP1 and/ or TAZ nuclear translocation and subsequent activation of their target genes.

Deregulation of Hippo pathway can induce tumors in model organisms and occurs in wide range of human cancers including melanoma. Merlin, a key component of this pathway which inhibits YAP1, is mutated/deleted in 8% of melanoma. Majority of uveal melanomas are driven by Gq/11 mutations that trigger YAP1 nuclear translocation, promoting tumor growth. High levels of YAP1 in BRAFV600E mutant tumors confer resistance to RAF- and MEK- targeted therapy in patients.

Our results show that YAP1 level is elevated in melanoma and the YAP1 inhibitor verteporfin alone or in combination with B-RAF inhibitor PLX4720 reduces the viability, invasion and anchorage-independent growth of B-RAF V600E mutant SK-MEL-28 and SK-MEL-5 cells. In addition, verteporfin treatment also reduced the viability of PLX4720 resistant 1205 cells. Western blot analysis of verteporfin and PLX4720 treated SK-MEL-28 and SK-MEL-5 cells displayed reduced levels of YAP1, B-RAF, pERK, MEK and pMEK.

We also report a novel physical interaction between YAP1 and B-RAF; this could be detected using double immunofluorescence and immunoprecipitation-western blotting techniques in both B-RAF V600E mutant and N-Ras mutant melanoma cells. Proximity ligation assays on tissue microarray showed that YAP1-B-RAF interaction is elevated in metastatic melanoma compared to normal skin. These novel findings highlight the crosstalk between B-RAF and Hippo/YAP1 signaling which might have a

potential role in melanoma development and progression. Further, experiments are in progress to elucidate the functional significance of YAP1-B-RAF interaction in melanoma.

Citation Format: Mohan Kumar Durai Raj, Jonathan Nguyen, Namrata Bora-singhal, Jane Messina, Geoffrey Gibney, Srikumar Chellappan. Cross-talk between BRAF and Hippo/YAP1 signaling in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 365. doi:10.1158/1538-7445.AM2017-365

Patterns of histologic response to neoadjuvant targeted therapy in patients with BRAF mutant melanoma

9584

Background: While BRAF and MEK inhibitors are approved for patients with BRAF V600 + unresectable/metastatic melanoma, their role in the neoadjuvant setting is less well defined. Results from small trials have noted robust response rates, but less is known about histological patterns of response in resected tumor specimens and relation to outcome in these patients (pts). Methods: In a retrospective study, we analyzed the clinical and pathologic patterns of response to neoadjuvant BRAF ± MEK inhibitor therapy in pts with locally advanced melanoma subsequently rendered disease free with surgery. Results: Twenty pts were identified, nine with stage IIIC and 11 with stage IV melanoma. Seven patients received neoadjuvant vemurafenib (VEM), 12 received dabrafenib + trametinib (D+T), and one encorafenib + binimetinib. The median duration of treatment was 7.8 months. Seven patients (35%) had a pathologic complete response (pCR); six of them had received combination therapy, 5 with D+T, 1 VEM with an HSP90 inhibitor. Four distinct histologic patterns were observed in the resected tumor specimens: necrotic, fibrotic/melanotic (tumoral melanosis), hyalinized, or mixed. With median follow-up of 25 months (range 1-60), six pts (30%) had experienced recurrence; three developed CNS metastases. Four of the six patients had received neoadjuvant D+T; three were restarted on their prior targeted therapy at recurrence and all responded. All 6 pts with recurrence had residual disease in the surgical specimen; three had no necrosis identified. In contrast to the 13 pts with persistent tumor, none of the 7 pCR pts has relapsed (p = 0.05). There was a trend towards improved relapse-free-survival (RFS) with a pCR, with a 1 yr of RFS-rate of 50.4% vs 100% in pCR.(p = 0.08) Of the 14 patients without subsequent recurrence, 9 had either a pure necrotic histology, or a mixed histological pattern that included necrosis. Conclusions: In locally advanced or M1a BRAF mutant melanoma, attaining a pCR to neoadjuvant targeted therapy may correlate with improved patient outcomes and be more likely achieved with combination therapy. Presence of necrosis in the surgical specimen appears be a favorable prognostic factor.

Epidermal programmed cell death-ligand 1 expression in TEN associated with nivolumab therapy

Nivolumab is a programmed cell death receptor-1 (PD-1) antibody used in the treatment of metastatic or unresectable melanoma. Cutaneous reactions are the most common adverse events reported with these agents and are rarely severe or life-threatening. Here we present a case report describing the clinicopathological findings of a patient with a fatal toxic epidermal necrolysis (TEN) eruption associated with use of nivolumab for treatment of metastatic melanoma. The patient developed a pruritic, morbiliform eruption, which slowly progressed over 3 months to a tender, exfoliative dermatosis. Histology initially showed interface dermatitis and subsequently revealed full thickness epidermal necrosis. The diagnosis of TEN was made. From initial biopsy to TEN presentation, there was an increase in the number of CD8+ lymphocytes within the dermal-epidermal junction and an increase of programmed death ligand 1 (PD-L1) expression in both lymphocytes and keratinocytes. Despite treatment with infliximab, high-dose steroids and intravenous immunoglobulin, the patient expired. Herein we describe what we believe is the second case of TEN associated with anti-PD1 therapy reported in the literature. Increased expression of PD-L1 by immunohistochemistry was observed as the eruption progressed to TEN. Early diagnosis and treatment is necessary in these fatal TEN reactions secondary to the anti-PD-1 antibody therapies.