Melanoma brain metastases: review of histopathological features and immune-molecular aspects

The ERK inhibitor LY3214996 augments anti-PD-1 immunotherapy in preclinical mouse models of BRAFV600E melanoma brain metastasis

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment; however, only a subset of patients with brain metastasis (BM) respond to ICI. Activating mutations in the mitogen-activated protein kinase signaling pathway are frequent in BM. The objective of this study was to evaluate whether therapeutic inhibition of extracellular signal-regulated kinase (ERK) can improve the efficacy of ICI for BM.

METHODS

We used immunotypical mouse models of BM bearing dual extracranial/intracranial tumors to evaluate the efficacy of single-agent and dual-agent treatment with selective ERK inhibitor LY3214996 (LY321) and anti-programmed death receptor 1 (PD-1) antibody. We verified target inhibition and drug delivery, then investigated treatment effects on T-cell response and tumor-immune microenvironment using high-parameter flow cytometry, multiplex immunoassays, and T-cell receptor profiling.

RESULTS

We found that dual treatment with LY321 and anti-PD-1 significantly improved overall survival in 2 BRAFV600E-mutant murine melanoma models but not in KRAS-mutant murine lung adenocarcinoma. We demonstrate that although LY321 has limited blood-brain barrier (BBB) permeability, combined LY321 and anti-PD-1 therapy increases tumor-infiltrating CD8+ effector T cells, broadens the T-cell receptor repertoire in the extracranial tumor, enriches T-cell clones shared by the periphery and brain, and reduces immunosuppressive cytokines and cell populations in tumors.

CONCLUSIONS

Despite the limited BBB permeability of LY321, combined LY321 and anti-PD-1 treatment can improve intracranial disease control by amplifying extracranial immune responses, highlighting the role of extracranial tumors in driving intracranial response to treatment. Combined ERK and PD-1 inhibition is a promising therapeutic approach, worthy of further investigation for patients with melanoma BM.

Demographics aspects of brain and spine metastatic melanoma. Retrospective analysis in a single third-level center

Background

Melanoma metastases to the CNS rank third in frequency, just after lung and breast metastases. There is controversy regarding the factors predisposing to developing CNS metastases in patients with cutaneous melanoma and their survival with conventional treatments.

Methods

We carried out a retrospective analysis in a third-level hospital in Mexico to determine epidemiological aspects of melanoma metastases to the central nervous system, factors related to its appearance, clinical presentation, and survival in three treatment groups: surgery, radiotherapy, and conservative management.

Results

We found that the nodular variant has the most significant association with CNS metastases. In addition, the superficial spreading variant has the highest risk of presenting a more substantial number of lesions, up to seven for each case and predominantly in the infratentorial space. On the other hand, we found more remarkable survival in patients treated only with surgery than those treated with radiotherapy or conservatively.

Conclusions

This study lays the foundations for future prospective survival analysis of the different current treatment modalities for metastatic melanoma in the brain and spine. It also highlights the clinical risk factors for metastatic brain and spine tumors of melanoma.

Multi-omic profiling reveals discrepant immunogenic properties and a unique tumor microenvironment among melanoma brain metastases

Melanoma brain metastases (MBM) are clinically challenging to treat and exhibit variable responses to immune checkpoint therapies. Prior research suggests that MBM exhibit poor tumor immune responses and are enriched in oxidative phosphorylation. Here, we report results from a multi-omic analysis of a large, real-world melanoma cohort. MBM exhibited lower interferon-gamma (IFNγ) scores and T cell-inflamed scores compared to primary cutaneous melanoma (PCM) or extracranial metastases (ECM), which was independent of tumor mutational burden. Among MBM, there were fewer computationally inferred immune cell infiltrates, which correlated with lower TNF and IL12B mRNA levels. Ingenuity pathway analysis (IPA) revealed suppression of inflammatory responses and dendritic cell maturation pathways. MBM also demonstrated a higher frequency of pathogenic PTEN mutations and angiogenic signaling. Oxidative phosphorylation (OXPHOS) was enriched in MBM and negatively correlated with NK cell and B cell-associated transcriptomic signatures. Modulating metabolic or angiogenic pathways in MBM may improve responses to immunotherapy in this difficult-to-treat patient subset.

A distinct pattern of growth and RAC1 signaling in melanoma brain metastasis cells

BACKGROUND

Melanoma, the deadliest of skin cancers, has a high propensity to form brain metastases that are associated with a markedly worsened prognosis. In spite of recent therapeutic advances, melanoma brain lesions remain a clinical challenge, biomarkers predicting brain dissemination are not clear and differences with other metastatic sites are poorly understood.

METHODS

We examined a genetically diverse panel of human-derived melanoma brain metastasis (MBM) and extracranial cell lines using targeted sequencing, a Reverse Phase Protein Array, protein expression analyses, and functional studies in vitro and in vivo.

RESULTS

Brain-specific genetic alterations were not detected; however, MBM cells in vitro displayed lower proliferation rates and MBM-specific protein expression patterns associated with proliferation, DNA damage, adhesion, and migration. MBM lines displayed higher levels of RAC1 expression, involving a distinct RAC1-PAK1-JNK1 signaling network. RAC1 knockdown or treatment with small molecule inhibitors contributed to a less aggressive MBM phenotype in vitro, while RAC1 knockdown in vivo led to reduced tumor volumes and delayed tumor appearance. Proliferation, adhesion, and migration were higher in MBM vs. non-MBM lines in the presence of insulin or brain-derived factors and were affected by RAC1 levels.

CONCLUSIONS

Our findings indicate that despite their genetic variability, MBM engage specific molecular processes such as RAC1 signaling to adapt to the brain microenvironment and this can be used for the molecular characterization and treatment of brain metastases.

Treatment of Advanced Metastatic Melanoma

The introduction in clinical practice of new drug compounds both targeted therapies anti-BRAF and checkpoint inhibitors have largely improved our potential to manage advanced metastatic melanoma patients. This has led to a significant improvement in terms of response rates and particularly in the overall survival (OS). The long-term results of trials with follow-up data of patients treated with targeted or immunotherapies reported median OS rates around 24 months, with 5-year survival rates around 35-40%. As to the drugs currently available and reimbursed by the Italian National Health System, 3 combinations of anti-BRAF/anti-MEK inhibitors are available (dabrafenib/trametinib, vemurafenib/cobimetinib and the most recently introduced encorafenib/binimetinib). As for checkpoint inhibitors, first line immunotherapy is represented by anti-PD1 blockers (nivolumab and pembrolizumab), whilst the anti-CTLA-4 ipilimumab can be used as second line immunotherapy. The decision-making factors that define the best treatment approach in stage IV patients with metastatic melanoma include the mutation pattern, performance status, high/low tumor load, brain metastases, progression pattern (low/fast), and availability of clinical trials. This review will analyze the current therapeutic tools adopted for the treatment of metastatic melanoma patients. It will then focus on the latest results obtained by novel treatments (checkpoint inhibitors and targeted therapies) which can be used in the clinical daily practice.