Abstract 631: Single-cell analysis of immune and stroma cell remodeling in renal cell carcinoma primary tumors and bone metastatic lesions
Authors: Mei Shenglin , Alchahin Adele M. , Tsea Ioanna , Kfoury Youmna , Taghreed Taghreed , Sarkar Hirak , Wu Shulin , Subtelny Alexander O. , Zhang Yida , Salari Keyan , Wu Chin-Lee , Randolph Mark A. , Scadden David T. , Dahl Douglas , Shin John , Kharchenko Peter , Saylor Philip , Sykes David , Baryawno Ninib 
Published: June 2023

Abstract
Background: Renal cell carcinoma (RCC) is the most common renal tumor in adults, and among these clear cell RCC (ccRCC) is most common subtype and accounts for most renal cancer-related deaths. One-third of patients with advanced ccRCC present with bone metastases at the time of diagnosis. Despite therapeutic advances, once cancer has metastasized to the bone, it represents a highly morbid and ultimately lethal disease. Comprehensive genomic studies in ccRCC have provided important insights into the somatic alterations and intra-tumor heterogeneity. However, the bone metastatic niche in humans, including the immune and stromal microenvironments, has not been well-defined.
Methods: We collected fresh patient samples directly from the operating room and performed single-cell transcriptomic profiling of human ccRCC tumors (ccRCC primary), solid metastatic tissue (Bone Met), liquid bone marrow at the vertebral level of spinal cord compression (Involved), liquid bone marrow from a different vertebral body distant from the tumor site but within the surgical field (Distal), as well as bone marrow stroma cells from patients undergoing hip replacement surgery (Benign) as control. We provide a comparative single cell transcriptomic analysis between ccRCC primary tumors and bone metastatic lesions.
Results: Comparison of malignant cells from primary and metastatic sites reveal a distinct transcriptional signature that is predictive of metastatic potential and patient survival. The bone marrow in metastatic patients has sustained immune-suppressive microenvironment, featuring increased, exhausted CD8+ cytotoxic T-cells, T-regulatory cells and tumor-associated macrophages (TAM) with distinct transcriptional states in metastatic lesions. Bone marrow stroma from tumor samples demonstrated a tumor-associated mesenchymal stromal cell population (TA-MSC) that appears to be supportive of epithelial-to mesenchymal transition (EMT), bone remodeling, and a cancer-associated fibroblast (CAFs) phenotype. This stromal subset is associated with poor progression-free and overall survival, markedly upregulates bone remodeling through the dysregulation of RANK/RANKL/OPG signaling activity in bone cells, ultimately leading to bone resorption.
Conclusions: These results provide insights into mechanisms underlying of ccRCC tumors progression leading bone metastasis. We also highlight potential communication channels and therefore therapeutic targets within both the immune and the tumor cell populations.
Citation Format: Shenglin Mei, Adele M. Alchahin, Ioanna Tsea, Youmna Kfoury, Taghreed Taghreed, Hirak Sarkar, Shulin Wu, Alexander O. Subtelny, Yida Zhang, Keyan Salari, Chin-Lee Wu, Mark A. Randolph, David T. Scadden, Douglas Dahl, John Shin, Peter Kharchenko, Philip Saylor, David Sykes, Ninib Baryawno. Single-cell analysis of immune and stroma cell remodeling in renal cell carcinoma primary tumors and bone metastatic lesions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 631.