Abstract 1312: Transcriptional signatures associated with lack of response to anti-PD-1 therapy in patients with renal cell carcinoma
Authors: Ascierto Maria Libera , McMiller Tracee , Berger Alan , Anders Robert A. , Cheadle Chris , Hu Haiying , Drake Charles , Pardoll Drew , Taube Janis , Topalian Suzanne L. 
Published: August 2015

Abstract
Background: The PD-1/PD-L1 immune checkpoint pathway limits host immune responses to cancer in the local tumor microenvironment. Monoclonal antibodies blocking PD-1 or PD-L1 have shown promising clinical results in a variety of advanced human cancers including renal cell carcinoma (RCC). We previously reported that response to anti-PD-1 therapy correlates with PD-L1 expression by tumor cells in pre-treatment biopsies. Although 20-30% of patients with metastatic RCC respond to anti-PD-1 therapy, many patients with PD-L1+ tumors still do not respond. The current study was undertaken to understand mechanisms underlying the failure of anti-PD-1 targeted therapies in patients with PD-L1+ RCC.
Methods: The specimen cohort included formalin-fixed, paraffin-embedded (FFPE) pre-treatment tumor biopsies expressing PD-L1, derived from 13 RCC patients treated with nivolumab (anti-PD-1) at a single institution [4 responders (R), 9 non-responders (NR); RECIST]. PD-L1+ specimens were defined as those having ≥5% of tumor cells with cell surface PD-L1 expression by immunohistochemistry (IHC). RNA was isolated from PD-L1+ regions on FFPE slides. Whole genome microarray profiling with cDNA-mediated Annealing, Selection, extension and Ligation (DASL) was performed. Global gene expression analysis was profiled using BRBArrayTools. Multiplex quantitative (q)RT-PCR was used to validate differential expression of genes of interest, and IHC was used to validate protein expression from select genes, in R vs. NR.
Results: Whole genome analysis revealed 234 transcripts that were differentially expressed in R vs. NR (p value ≤ 0.01, fold change ≥1.5). Ingenuity Pathway Analysis (IPA) of these transcripts showed the involvement of metabolic and immune pathways as well as genes encoding oxidation stress response molecules. Multiplex qRT-PCR for a subset of 60 differentially expressed genes validated significant over-expression of genes with metabolic functions, such as drug glucuronidation (UGT1A6/A1/A3), glucose transport (SLC23A1), and mitochondrial oxidation (AKR1C3) in NR vs. R. Conversely, R were found to overexpress immune markers such as BMP1, which has been shown to positively regulate PD-L1 expression, and CCL3 involved in leukocyte migration.
Conclusions: Although tumor PD-L1 expression is associated with an increased likelihood of response to anti-PD-1/PD-L1 therapy, tumor cell-intrinsic metabolism may contribute to treatment resistance in PD-L1+ patients. Our data suggest that overexpression of certain metabolic factors may contribute to the failure of PD-L1+ RCC to respond to PD-1 pathway blockade, while immune factors in the tumor immune microenvironment may contribute to success. Treatment strategies that co-target these factors may be needed to enhance responses to anti-PD-1 immunotherapy in RCC.
Supported by grants from Bristol-Myers Squibb and Stand Up to Cancer
Citation Format: Maria Libera Ascierto, Tracee McMiller, Alan Berger, Robert A. Anders, Chris Cheadle, Haiying Hu, Charles Drake, Drew Pardoll, Janis Taube, Suzanne L. Topalian. Transcriptional signatures associated with lack of response to anti-PD-1 therapy in patients with renal cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1312. doi:10.1158/1538-7445.AM2015-1312