Microenvironmental Landscape of Human Melanoma Brain Metastases in Response to Immune Checkpoint Inhibition.

Melanoma-derived brain metastases (MBM) represent an unmet clinical need because central nervous system progression is frequently an end stage of the disease. Immune checkpoint inhibitors (ICI) provide a clinical opportunity against MBM; however, the MBM tumor microenvironment (TME) has not been fully elucidated in the context of ICI. To dissect unique elements of the MBM TME and correlates of MBM response to ICI, we collected 32 fresh MBM and performed single-cell RNA sequencing of the MBM TME and T-cell receptor clonotyping on T cells from MBM and matched blood and extracranial lesions. We observed myeloid phenotypic heterogeneity in the MBM TME, most notably multiple distinct neutrophil states, including an IL8-expressing population that correlated with malignant cell epithelial-to-mesenchymal transition. In addition, we observed significant relationships between intracranial T-cell phenotypes and the distribution of T-cell clonotypes intracranially and peripherally. We found that the phenotype, clonotype, and overall number of MBM-infiltrating T cells were associated with response to ICI, suggesting that ICI-responsive MBMs interact with peripheral blood in a manner similar to extracranial lesions. These data identify unique features of the MBM TME that may represent potential targets to improve clinical outcomes for patients with MBM.

Low expression of the PPARγ-regulated gene thioredoxin-interacting protein accompanies human melanoma progression and promotes experimental lung metastases.

The thioredoxin system plays key roles in regulating cancer cell malignancy. Here we identify the Thioredoxin-interacting protein (TXNIP) as a gene, which expression is regulated by PPARγ in melanoma cells. We show that high TXNIP expression levels associate with benign melanocytic lesions, with tumor regression in patients on MAP kinase targeted therapy, with decreased proliferation in patients' melanoma biopsies, and with cell cycle arrest in human melanoma cell lines. In contrast, reduced TXNIP expression associates with advanced melanoma and with disease progression in patients. TXNIP depletion in human melanoma cells altered the expression of integrin beta-3 and the localization of the integrin alpha-v/beta-3 dimer at their surface. Moreover, TXNIP depletion affected human melanoma cell motility and improved their capacity to colonize mouse lungs in an in vivo assay. This study establishes TXNIP as a PPARγ-regulated gene in melanoma cells, thereby suggesting a link between these two proteins both involved in the regulation of cancer and of energy metabolism. It also reveals that the decrease in TXNIP expression, which is observed in advanced patient tumors, likely favors lung metastatic seeding of malignant cells.

Adjuvant Therapy Failure Patterns in the Modern Era of Melanoma Management.

BACKGROUND: The management of patients with resected stage 3 melanoma has changed significantly due to adoption of the Multicenter Selective Lymphadenectomy Trial (MSLT)-2 guidelines and to the survival benefit of adjuvant anti-PD-1 immunotherapy and BRAF/MEK-inhibitor (BRAF/MEKi) therapy. Data are scarce regarding recurrence patterns, adjuvant therapy responses, and therapy-associated adverse events (AEs) in the modern era. METHODS: This single-institution, retrospective study analyzed surgically resected stage 3 and oligometastatic stage 4 patients who received anti-PD-1, BRAF/MEKi, or surgery with active surveillance only. The primary end point of the study was recurrence-free survival (RFS). The secondary end points were the location and clinical characteristics of recurrence and therapy-associated AEs. RESULTS: From a cohort of 137 patients, the study enrolled 102 patients treated with adjuvant anti-PD-1 (n = 46), adjuvant BRAF/MEKi (n = 3), or surgery alone (n = 26). During a mean follow-up period of 17 months, 20% of the ani-PD-1 patients, 13% of the BRAF/MEKi patients, and 42% of the surgery-only patients experienced recurrence. Log-rank testing showed a significantly longer RFS for the patients treated with anti-PD-1 [15.3 months; interquartile range (IQR), 8.2-23.2 months; p = 0.04] or BRAF/MEKi (17.9 months; IQR, 12.5-23 months; p = 0.01) than for those treated with surgery alone (11.9 months; IQR, 7.0-17.6 months). In the anti-PD-1 group, AEs occurred less frequently than in the BRAF/MEKi group (54% vs 80%; p = 0.03). CONCLUSIONS: Adjuvant anti-PD-1 and BRAF/MEKi were associated with significantly improved RFS for the patients with resected stage 3 or 4 melanoma. The BRAF/MEKi group had significantly more AEs than the anti-PD-1 group. This is the first study to characterize real-world recurrence in the modern era of adjuvant therapy for melanoma.

Mixed Response to Immunotherapy in Patients with Metastatic Melanoma.

BACKGROUND: Immunotherapy has improved overall survival in metastatic melanoma. Response to therapy can be difficult to evaluate as the traditionally used RECIST 1.1 criteria do not capture heterogeneous responses. Here we describe the clinical characterization of melanoma patients with a clinically defined mixed response to immunotherapy. METHODS: This was a single institution, retrospective analysis of stage IV melanoma patients who received first-line anti-CTLA-4, anti-PD1, or combination anti-CTLA-4/anti-PD1. Therapy response was assessed via clinical definitions, which consisted of cross-sectional imaging combined with clinical exam. Course of disease, clinicopathological characteristics, and management in patients with a mixed clinical response were analyzed. RESULTS: In 292 patients (anti-CTLA4 = 63; anti-PD1 = 148, anti-CTLA4/anti-PD1 = 81), 103 were responders (35%), 64 mixed responders (22%), and 125 patients had progressive disease (43%). Of patients with a mixed response, 56% eventually had response to therapy (mixed response followed by response, MR-R), while 31% progressed on therapy (MR-NR). MR-NR patients had higher median LDH (p < 0.01), 3 or more organ sites with metastases (p < 0.01), and more frequently had M1d disease (p < 0.01). Mixed responders who underwent surgery (n = 20) had a significantly longer mean OS compared to patients who did not undergo surgery (6.9 years, 95% CI 6.2-7.6 vs. 6.0 years, 95% CI 4.6-7.3, p = 0.02). DISCUSSION: Mixed response to immunotherapy in metastatic melanoma was not uncommon in our cohort (22%). Clinical characteristics associated with progression of disease after initial mixed response included higher LDH, brain metastases, and ≥ 3 organ sites with metastases. Surgical treatment for highly selected patients with a mixed response was associated with improved outcomes.