Abstract LB309: Influence of pathological pericytes on PDAC tumor progression and tumor microenvironment
Authors: Natarajan Vikneshwari , Ha Sangdeuk , Kim Jiha 
Published: April 2024

Abstract
Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer death in men and women in the U.S., with a 5-year survival rate of 12 %. This poor prognosis is partly due to the aggressive nature of the disease, lack of early detection methods, its complex and dense tumor microenvironment (TME), and lack of effective treatment options. Within the PDAC TME, morphologically aberrant leaky vessels are responsible for hypoxia and impaired immune response, which likely reduces the efficacy of cancer therapies. We and others showed that pericyte coverage significantly correlates with vascular integrity/function and intratumoral hypoxia. Therefore, understanding perivascular heterogeneity and the unique contribution of each phenotype to the TME evolution is a critical step toward personalized treatment options for PDAC. Consequently, we hypothesize that correcting such undesirable phenotype via vascular normalization will alleviate the harsh TME and enhance the treatment efficacy.
Our study revealed that tumor-associated pericytes across all PDAC tumor tissues exhibited ectopic αSMA expression up to 10 times higher than normal pericytes. This aberrant pericyte phenotype correlated with vascular leakiness, hypoxia, and vessel leakiness. Our attempt to elucidate the underlying mechanism of pericyte phenotype switching using an in-vitro culture system shows that pancreatic cancer cell-derived extracellular vesicles are a potent inducer of αSMA expression in pericytes present mechanical abnormalities and immune-suppressive features.
To further determine the pathological signature of tumor pericytes and identify potential target molecules toward vascular normalization, we performed single-cell RNA sequencing (scRNA-seq). Pericytes were isolated from WT pancreas and KPC tumors at 15-20 weeks to obtain desired viable single-cell population suitable for 10x library preparation and Illumina sequencing.We isolated and barcode at least 5000 cells using the 10X genomics system. Sequencing libraries were prepared using the Chromium Single Cell 3ʹ reagent kit v3. They were sequenced until a sequencing depth of 100,000 reads per cell was achieved, and the data was analyzed using Cell Ranger and various other analytical tools (e.g., Seuret, Conos, ScMerge, singleR). We generated custom scripts from the single-cell data to answer the relevant questions. Sequences were demultiplexed based on barcodes and assigned unique molecular identifiers (UMIs). We visualized clusters using graphing methods, such as t-SNE plots and UMAP clustering. This approach helped identify groups of cells with unique and differential transcriptional landscapes and group them into cellular subtypes based on their gene expression profiles.
In conclusion, our study indicates that tumor-associated pericytes undergo phenotype switching under the influence of pancreatic cancer cells, and these aberrant pericytes might contribute to non-optimal vascular integrity and function. Single-cell RNA sequencing helped understand the molecular signature of the pericyte subpopulation, providing a powerful tool to develop novel targeting strategies for vascular normalization. Future work includes exploring the vascular normalization approach by suppressing pericyte phenotype switching to enhance vascular function and chemo and immunotherapeutic efficacy.
Citation Format: Vikneshwari Natarajan, Sangdeuk Ha, Jiha Kim. Influence of pathological pericytes on PDAC tumor progression and tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB309.