Outcome-Related Signatures Identified by Whole Transcriptome Sequencing of Resectable Stage III/IV Melanoma Evaluated after Starting Hu14.18-IL2.

Purpose: We analyzed whole transcriptome sequencing in tumors from 23 patients with stage III or IV melanoma from a pilot trial of the anti-GD2 immunocytokine, hu14.18-IL2, to identify predictive immune and/or tumor biomarkers in patients with melanoma at high risk for recurrence.

Experimental Design: Patients were randomly assigned to receive the first of three monthly courses of hu14.18-IL2 immunotherapy either before (Group A) or after (Group B) complete surgical resection of all known diseases. Tumors were evaluated by histology and whole transcriptome sequencing.

Results: Tumor-infiltrating lymphocyte (TIL) levels directly associated with relapse-free survival (RFS) and overall survival (OS) in resected tumors from Group A, where early responses to the immunotherapy agent could be assessed. TIL levels directly associated with a previously reported immune signature, which associated with RFS and OS, particularly in Group A tumors. In Group A tumors, there were decreased cell-cycling gene RNA transcripts, but increased RNA transcripts for repair and growth genes. We found that outcome (RFS and OS) was directly associated with several immune signatures and immune-related RNA transcripts and inversely associated with several tumor growth-associated transcripts, particularly in Group A tumors. Most of these associations were not seen in Group B tumors.

Conclusions: We interpret these data to signify that both immunologic and tumoral cell processes, as measured by RNA-sequencing analyses detected shortly after initiation of hu14.18-IL2 therapy, are associated with long-term survival and could potentially be used as prognostic biomarkers in tumor resection specimens obtained after initiating neoadjuvant immunotherapy.