Melanoma Lesions Independently Acquire T-cell Resistance during Metastatic Latency

Abstract

Melanoma often recurs after a latency period of several years, presenting a T cell-edited phenotype that reflects a role for CD8(+) T cells in maintaining metastatic latency. Here, we report an investigation of a patient with multiple recurrent lesions, where poorly immunogenic melanoma phenotypes were found to evolve in the presence of autologous tumor antigen-specific CD8(+) T cells. Melanoma cells from two of three late recurrent metastases, developing within a 6-year latency period, lacked HLA class I expression. CD8(+) T cell-resistant, HLA class I-negative tumor cells became clinically apparent 1.5 and 6 years into stage IV disease. Genome profiling by SNP arrays revealed that HLA class I loss in both metastases originated from a shared chromosome 15q alteration and independently acquired focal B2M gene deletions. A third HLA class I haplotype-deficient lesion developed in year 3 of stage IV disease that acquired resistance toward dominant CD8(+) T-cell clonotypes targeting stage III tumor cells. At an early stage, melanoma cells showed a dedifferentiated c-Jun(high)/MITF(low) phenotype, possibly associated with immunosuppression, which contrasted with a c-Jun(low)/MITF(high) phenotype of T cell-edited tumor cells derived from late metastases. In summary, our work shows how tumor recurrences after long-term latency evolve toward T-cell resistance by independent genetic events, as a means for immune escape and immunotherapeutic resistance. Cancer Res; 76(15); 4347-58. ©2016 AACR.

RIG-I activation induces the release of extracellular vesicles with antitumor activity

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Figure 1.RIG-I stimulation triggers the release of extracellular vesicles (EVs). (A) Melanoma cells D04mel 28 or Ma-Mel-86c 29 were analyzed for mRNA expression of RIG-I by quantitative real-time PCR in the presence or absence of type I Interferon (IFN) stimulation. Data are normalized to β-Actin.

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“…Schmidt 28 . The human melanoma cell line Ma-Mel-86c was provided by A. Paschen 29 . The mouse melanoma cell line (HCmel12) was derived from a primary melanoma in HGF/SF—CDK4(R24C) mice by serial transplantation 33 .…”

HLA class I loss in metachronous metastases prevents continuous T cell recognition of mutated neoantigens in a human melanoma model

“…Her clinical course is summarized in Supplementary Figure 1 and detailed in [20]. Permanent melanoma cell lines Ma-Mel-86a, −86b, −86c and −86f were established from four distinct LN metastases occurring during stage III disease in 01/2002 and during stage IV disease in 02/2004, 05/2005 and 12/2008, respectively.…”

“…Ma-Mel-86b and −86f represented HLA class I loss variants due to a biallelic beta-2-microglobulin gene ( B2M ) inactivation. Ma-Mel-86c was lacking one complete HLA class I haplotype [20]. Autologous peripheral blood mononuclear cells (PBMCs) were isolated in 05/2002, 04/2004 and 08/2004.…”

“…Herein, we searched for potentially immunogenic single nucleotide substitutions (SNS) and insertions and deletions (indels) using exome and transcriptome sequencing data generated from four melanoma cell lines derived from distinct lymph node (LN) metastases of patient Ma-Mel-86 [20] and from an autologous lymphoblastoid cell line as germline control. By this means, 181 expressed non-synonymous somatic SNS and ten expressed non-synonymous indels were identified in the four melanoma cell lines.…”