Brain metastases (BM) are one the most lethal and poorly managed clinical complications in cancer patients. These secondary tumors represent the most common intracranial neoplasm in adults, most frequently originating from lung cancer, breast cancer, and cutaneous melanoma. In primary brain tumors, such as gliomas, recent advances in DNA methylation profiling have allowed for a comprehensive molecular classification. Such data provide prognostic information, in addition to helping predict patient response to specific systemic therapies. However, epigenetic alterations of metastatic brain tumors with specific biological and translational relevance still require much further exploration. Using the widely employed Illumina Infinium HumanMethylation 450K platform, we have generated a cohort of genome-wide DNA methylomes from ninety-six needle-dissected BM specimens from patients with lung cancer, breast cancer, and cutaneous melanoma with clinical, pathological, and demographic annotations. This resource offers an unprecedented and unique opportunity to identify novel DNA methylation features influencing the behavior of brain metastasis, and thus accelerate the discovery of BM-specific theranostic epigenetic alterations.

This study validated the EORTC prognostic model for recurrence-free and melanoma-specific survival of patients with negative sentinel nodes. The addition of other prognostic factors only improved the model marginally. The validated EORTC model could be used for personalizing follow-up and selecting high-risk patients for trials of adjuvant systemic therapy.

Cancers, including cutaneous melanoma, can cluster in families. In addition to environmental etiological factors such as ultraviolet radiation, cutaneous melanoma has a strong genetic component. Genetic risks for cutaneous melanoma range from rare, high-penetrance mutations to common, low-penetrance variants. Known high-penetrance mutations account for only about half of all densely affected cutaneous melanoma families, and the causes of familial clustering in the remainder are unknown. We hypothesize that some clustering is due to the cumulative effect of a large number of variants of individually small effect. Common, low-penetrance genetic risk variants can be combined into polygenic risk scores. We used a polygenic risk score for cutaneous melanoma to compare families without known high-penetrance mutations with unrelated melanoma cases and melanoma-free controls. Family members had significantly higher mean polygenic load for cutaneous melanoma than unrelated cases or melanoma-free healthy controls (Bonferroni-corrected t-test P = 1.5 × 10-5 and 6.3 × 10-45, respectively). Whole genome sequencing of germline DNA from 51 members of 21 families with low polygenic risk for melanoma identified a CDKN2A p.G101W mutation in a single family but no other candidate high-penetrance melanoma susceptibility genes. This work provides further evidence that melanoma, like many other common complex disorders, can arise from the joint action of multiple predisposing factors, including rare high-penetrance mutations, as well as via a combination of large numbers of alleles of small effect.

LNK (SH2B3) is a key negative regulator of JAK-STAT signaling which has been extensively studied in malignant hematopoietic diseases. We found that LNK is significantly elevated in cutaneous melanoma; this elevation is correlated with hyperactive signaling of the RAS-RAF-MEK pathway. Elevated LNK enhances cell growth and survival in adverse conditions. Forced expression of LNK inhibits signaling by interferon-STAT1 and suppresses interferon (IFN) induced cell cycle arrest and cell apoptosis. In contrast, silencing LNK expression by either shRNA or CRISPR-Cas9 potentiates the killing effect of IFN. The IFN-LNK signaling is tightly regulated by a negative feedback mechanism; melanoma cells exposed to IFN upregulate expression of LNK to prevent overactivation of this signaling pathway. Our study reveals an unappreciated function of LNK in melanoma and highlights the critical role of the IFN-STAT1-LNK signaling axis in this potentially devastating disease. LNK may be further explored as a potential therapeutic target for melanoma immunotherapy.

Checkpoint inhibitor blockade response is limited to a subset of the patient population. These results have implications for the development of LC3B as a predictive biomarker of checkpoint inhibitor blockade to guide patient selection, as well as G9a inhibition as a strategy to extend the proportion of patients responding to immunotherapy.

10050 Background: ctDNA detected by ddPCR predicts ICI response in MM, although its utility is limited to pts with known recurring mutations eg. BRAF, NRAS, KIT. We sought to overcome this limitation by using a next generation sequencing approach in BRAF V600 wild type (WT) MM pts. Methods: Plasma was collected at baseline and Week (wk) 6 in 35 BRAF V600 WT MM pts treated with ICI. Cell free (cf)DNA was analyzed using Guardant360 and only somatic non-synonymous and promoter variants were considered. Pts who failed cfDNA extraction at baseline were excluded (n = 3). Favorable ctDNA was defined as undetectable ctDNA at wk 6 and unfavorable ctDNA defined as detectable ctDNA at wk6. Response was according to RECIST at first restaging. Results: Of the evaluable 32 pts (64 plasma samples), median baseline cfDNA quantity was 33ng (range 4-657ng) and ctDNA was detected in 29/32 pts (91%). All 3 pts with undetectable baseline ctDNA had less than 10ng cfDNA compared to only 1/29 pts with detectable baseline ctDNA. Number of mutations identified in the 29 ctDNA-positive pts was 4 per pt (range 1-22). Response assessment was performed on 30 evaluable pts. Candidate driver mutation(s) in BRAF, NF1, or N/K/HRAS were identified in 26/30 pts. These mutations were often detected with other established mutations involved in tumorigenesis (eg. TERT promoter), or passenger mutations (eg. clonal hematopoiesis). Analysis of driver mutations revealed a sensitivity and specificity in predicting treatment failure of 92% and 93%, respectively (table). When all mutations identified were evaluated for treatment response, 9/18 responding pts retained some ctDNA at wk 6, although this never included TERT variants. The resulting sensitivity and specificity in predicting treatment failure changed to 100% and 50%, respectively, when all cfDNA variants were included. Conclusions: The extensive coverage of Guardant360 improves ctDNA detection in BRAF V600 WT MM pts, allowing non-invasive, rapid, and longitudinal assessment of response in a broader population. The expanded coverage also identifies passenger variants of potential non-MM origin, eg. clonal hematopoiesis, and with significant overlap with ctDNA, it is not possible to distinguish between the two in the circulation. We therefore recommend identification and monitoring of known cancer driver mutations only. [Table: see text]

Clinicopathological and body site differences between de novo melanoma and NAM support the divergent pathway model of development. These differences were also found in thin melanomas, suggesting that de novo melanomas are different from NAM and their differences are not due to the obliteration of naevus remnants in thicker tumours.

While immune checkpoint inhibitors targeting the CTLA-4 and PD-1 receptors have significantly improved outcomes of many patients with metastatic melanoma, there remains a group of patients who demonstrate no benefit. In this study, we sought to characterise patients who do not respond to anti-PD-1-based therapies based on their clinical, genetic and immune profiles. Forty patients with metastatic melanoma who did not respond to anti-PD-1 +/- anti-CTLA-4 treatment were identified. Targeted RNA sequencing (<i>n</i> = 37) was performed on pretreatment formalin-fixed paraffin-embedded (FFPE) melanoma specimens. Patients clustered into two groups based on the expression profiles of 26 differentially expressed genes: an immune gene rich group (<i>n</i> = 17) expressing genes associated with immune and T cell signalling, and a second group (<i>n</i> = 20) expressing genes associated with metabolism, signal transduction and neuronal signalling. Multiplex immunohistochemistry validated significantly higher densities of tumour-infiltrating lymphocytes (TILs) and macrophages in the immune gene-rich group. This TIL-high subset of patients also demonstrated higher expression of alternative immune-regulatory drug targets compared to the TIL-low group. Patients were also subdivided into rapid progressors and other progressors (cut-off 2 mo progression-free survival), with significantly lower TILs (<i>p</i> = 0.04) and CD68+ macrophages (<i>p</i> = 0.0091) in the rapid progressors. Furthermore, a trend towards a higher tumour burden was observed in rapid progressors (<i>p</i> = 0.06). These data highlight the need for a personalised and multilayer (clinical and molecular) approach for identifying the most appropriate treatments for anti-PD-1 resistant patients and provides insight into how individual treatment strategies can be achieved.