Abstract 3196: Soluble factors released by pancreatic cancer cells enhance neutrophil survival
Authors: Goel Paran , Saxena Sugandha , Molczyk Caitlin , Singh Rakesh 
Published: July 2021

Pancreatic cancer (PC) remains a challenge to modern-day cancer therapeutics, with a dismal five-year survival rate of 10%. Due to the pancreas' tricky location and the dense stroma surrounding it, patients have late diagnosis and fail to respond to chemotherapy regimens. The genetic stability of the tumor microenvironment (TME) in comparison with rapidly evolving tumor cells makes it an attractive target for the development of cancer therapeutics. Neutrophils, the most abundant immune cell, is an essential player in the TME. These neutrophils can become pro-tumorigenic based on signals they receive in the TME by regulating immune suppression, tumor metastasis, and angiogenesis. Previous studies from our laboratory demonstrate an increase in the number of neutrophils in the pancreatic tumor with the PC disease's progression in the KPC Model (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre). Based on our previous observation and accumulating literature, we hypothesize that pancreatic tumor cells can increase neutrophil proliferation and/or survival in circulation and tumor in situ. We investigated the effect of soluble factors released by pancreatic tumor cells on neutrophil proliferation/survival with this rationale. For this objective, we utilized murine promyelocytes cells (MPRO), a mouse neutrophil cell line, and a human leukemia cell line (HL60), a human neutrophil cell line. We treated MPRO and HL60 cells with a gradient of supernatants collected from T3M-4- and CD18/HPAF-parent and gemcitabine-resistant cells. By utilizing the WST assay, we observed an increase in MRPO and HL60 cells' viability with an increasing gradient of supernatant collected from both T3M-4, CD18/HPAF-parent gemcitabine-resistant cells with serum-free media as a control. We also observed a slight increase in neutrophil viability when treated with the supernatant collected from parent cell-lines supernatant compared to supernatant collected from the gemcitabine resistant cell-lines. Next, to delineate the effect of direct interaction between pancreatic tumor cells and neutrophils, we utilized a co-culture assay between MPRO cells and CD18/HPAF cells. We observed an increase in the viability of CD18/HPAF cells when placed in contact with the neutrophils; however, we observed inhibition in the viability of neutrophils placed in contact with the tumor cells. Our results showing positive viability of neutrophils with the treatment of soluble tumor factors explain higher neutrophil to lymphocyte ratio in PC patients' blood circulation. Neutrophils in the TME release pro-tumorigenic cytokines that increase tumor cell proliferation, albeit resulting in neutrophil death as observed by neutrophil growth inhibition. Along with neutrophil survival, a more mechanistic understanding of neutrophil recruitment and polarization in TME will facilitate designing novel therapeutics for PC.

Citation Format: Paran Goel, Sugandha Saxena, Caitlin Molczyk, Rakesh Singh. Soluble factors released by pancreatic cancer cells enhance neutrophil survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3196.