Abstract A029: Epigenomic profiling nominates master transcription factors (TFs) driving sarcomatoid differentiation of renal cell carcinoma (RCC)
Authors: Semaan Karl , Zarif Talal El , Eid Marc , Shah Valisha , Fortunato Brad , Saliby Renee Maria , Nassar Amin H. , Alaiwi Sarah Abou , Seo Ji-Heui , Labaki Chris , Bakouny Ziad , Matar Sayed , Ahmar Nourhan El , Laimon Yasmin Nabil , Lee Gwo-Shu Mary , Pomerantz Mark , Berchuck Jacob , Signoretti Sabina , Van Allen Eliezer , Choueiri Toni , Braun David , Freedman Matthew , Baca Sylvan 
Published: August 2023

Abstract
Introduction Sarcomatoid RCC (sRCC) is associated with poor prognosis. Recent studies showed promising response rates of sRCC to immune checkpoint blockade (ICB). Although distinct patterns of gene expression in sRCC have been reported, the gene regulatory programs that drive SD remain unknown. This study aims to nominate TFs driving SD and to evaluate their impact on the clinical outcomes of patients (pts) with RCC. Methods Chromatin immunoprecipitation and sequencing (ChIP-seq) for H3K27ac was performed on histologically annotated areas of sRCC and non-sRCC fresh frozen tissue samples collected at Dana-Farber Cancer Institute. Regulatory elements that were differentially active between the two groups were identified (cutoff p&lt;0.01, log-fold change (LFC) threshold=1). Enrichment of specific TF binding motifs at activated regulatory elements in sRCC was assessed using HOMER. Differential gene expression analysis of TFs was performed using DESeq2 on RNA-seq data from TCGA (Benjamini-Hochberg q &lt;0.01, LFC threshold=1). An unpaired student’s t-test was performed to compare mean gene expression levels in transcript per million (TPM) on baseline sRCC and non-sRCC tissue samples from the IMmotion151 trial (sunitinib vs. atezolizumab-bevacizumab in metastatic RCC). Pts enrolled in the IMmotion151 trial were divided into quartiles based on gene expression levels of candidate TFs. Progression-free survival (PFS) was compared between the quartiles using a multivariable Cox proportional-hazards model accounting for age and IMDC risk score. The association of TF expression with the objective radiographic response (ORR) was analyzed using a logistic regression model. Results ChIP-seq was performed on 9 sRCC & 17 non-sRCC samples. We identified 278 candidate regulatory elements with increased H3K27ac levels in sRCC vs. non-sRCC that were enriched for nucleotide motifs bound by the TFs FOSL1 and E2F7. Differential expression analysis between 48 sRCC vs. 493 non-sRCC samples showed that FOSL1 & E2F7 were significantly upregulated in sRCC vs. non-sRCC (LFC=1.7, q=5e-11; LFC=1.8, q=1.3e-20; resp.). Mean TPMs of FOSL1 & E2F7 were significantly increased in sRCC vs. non-sRCC in IMmotion151 cohort (2.5 vs. 1.5 TPM for FOSL1, and 2.9 vs. 1.9 TPM for E2F7, all p&lt;0.001). Pts in the highest quartile of FOSL1 and E2F7 expression showed significantly shorter PFS in IMmotion151 pts receiving sunitinib alone (HR=1.6, 95%CI=1.3-2.2, p=0.008 & HR=2.6, 95%CI=1.8-3.7, p&lt;0.001; resp.). We observed similar results even after controlling for the presence of SD. Increased expression of E2F7 was associated with worse ORR in IMmotion151 pts who received sunitinib alone, even after controlling for the presence of SD (OR=0.24±0.4, p&lt;0.001). Conclusion This is the first study to analyze the epigenomic landscape of sRCC by integrating ChIP-seq and RNA-seq data. Our findings implicated FOSL1 & E2F7 as transcriptional regulators of SD with prognostic relevance. Further studies are underway to validate these results.
Citation Format: Karl Semaan, Talal El Zarif, Marc Eid, Valisha Shah, Brad Fortunato, Renee Maria Saliby, Amin H. Nassar, Sarah Abou Alaiwi, Ji-Heui Seo, Chris Labaki, Ziad Bakouny, Sayed Matar, Nourhan El Ahmar, Yasmin Nabil Laimon, Gwo-Shu Mary Lee, Mark Pomerantz, Jacob Berchuck, Sabina Signoretti, Eliezer Van Allen, Toni Choueiri, David Braun, Matthew Freedman, Sylvan Baca. Epigenomic profiling nominates master transcription factors (TFs) driving sarcomatoid differentiation of renal cell carcinoma (RCC) [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr A029.