Association of gene expression profile in metastatic melanoma and survival to a dendritic cell-based vaccine

Abstract

9002 Background: Emerging data suggests that features of the melanoma tumor microenvironment may determine the clinical outcome to immunotherapies. We recently have observed a gene expression signature that correlated with a favorable clinical outcome in response to an IL-12-based melanoma vaccine. Increased expression of chemokine genes and T cell transcripts, and decreased expression of genes associated with aggressive tumor biology, were observed in the favorable group. To determine whether these patterns were reproducible, gene expression profiling was performed from an independent vaccine clinical trial. Methods: Patients with advanced melanoma were treated with autologous, mature monocyte-derived dendritic cells loaded with a combination of melanoma antigen peptides. Pretreatment biopsies were cryopreserved for RNA extraction and gene expression profiling. Patients were categorized into “long survival” (> 24 months) or “short survival” outcomes. Supervised hierarchical clustering was performed to identify genes differentially expressed in the two outcome groups. Results: RNA that passed quality control was obtained from 17 stage IV patients, 5 with a short survival and 12 with a long survival. 408 genes were differentially at least 2- fold. Consistent with previous observations, tumors from favorable outcome patients expressed higher levels of several T cell-specific genes, including Thy1 and CD28; chemokines, including CCL19, CXCL12, and CXCL14; and other immune genes, including LTβ, IL-1R, IFNαR2, IL27R, CD69, and FcRs. Conversely, tumors from unfavorable outcome patients expressed higher levels of pro- angiogeneic genes, including Flt1; anti-apoptotic genes, including SerpinH1 and Serpine1; and multiple collagens. Conclusions: Our results confirm that a subset of transcripts expressed in melanoma metastases may be useful as a predictive biomarker for response to melanoma vaccines. The categories of genes identified point toward new opportunities for overcoming resistance mechanisms. Future studies should integrate gene expression profiling of pre-treatment biopsies as a stratification or enrichment factor in immunotherapy trials. No significant financial relationships to disclose.