Abstract B21: Elucidating the molecular mechanism of Myeloid Derived Suppressor Cell (MDSC) divergence in the tumor microenvironment (TME) of pancreatic cancer


 Pancreatic cancer is one of the deadliest malignancies with an average five-year survival of mere 2-9%. Emerging evidence suggests that the presence of polymorphonuclear (PMN) myeloid derived suppressor cells (MDSCs) with neutrophil-like phenotypes and morphologies play a major role in adverse clinical outcomes due in part to their contribution in establishing immunosuppressive tumor microenvironment (TME). Despite recent advances in our understanding of MDSC phenotypes and characteristics in the TME, the underlying molecular mechanisms by which classical neutrophils differentiate into MDSC within the TME remails largely unknown. To investigate the microenvironmental cues that regulate PMN-MDSC differentiation at the tumor site, we established several in vitro co-culture systems using pancreatic cancer cells and 3D spheroid conditions. With live cell migration microscopy, we first showed that neutrophils actively swarmed into the pancreatic cancer spheroids and stayed active for an extended time period in the tumor. We further found that cancer cell culture supernatant significantly extended neutrophil survival and successfully differentiated neutrophils into MDSCs that exhibited decreased type 1 Interferon levels, increased arginase and ROS expression, and had the ability to suppress CD8 cytotoxicity. Additionally, when compared to other forms of neutrophil activators such as LPS and TNF, only tumor conditioned media enhanced neutrophil survival and MDSC differentiation. Our data suggest the presence of novel molecular processes that support MDSC differentiation at the tumor site. To identify the molecular regulators of MDSC formation, we have developed a CRISPR-Cas9 pooled library screen using the immortalized granulocyte-monocyte progenitor cell line, HoxB8. This study will further our understanding of MDSC differentiation and may help to develop therapeutics to limit MDSC development in the TME of pancreatic and other solid cancers.
 Citation Format: Ankit Dahal, Yeonsun Hong, Minsoo Kim. Elucidating the molecular mechanism of Myeloid Derived Suppressor Cell (MDSC) divergence in the tumor microenvironment (TME) of pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B21.