Abstract
Pancreatic ductal adenocarcinoma (PDAC) is highly lethal and resistant to immunotherapy. Although immune recognition can be enhanced with immunomodulatory agents including checkpoint inhibitors and vaccines, few patients experience clinical efficacy because the tumor immune microenvironment (TiME) is dominated by immunosuppressive myeloid cells that impose T cell inhibition. Inhibition of phosphodiesterase-5 (PDE5) was reported to downregulate metabolic regulators arginase and inducible NOS in immunosuppressive myeloid cells and enhance immunity against immune-sensitive tumors, including head and neck cancers. We show for the first time to our knowledge that combining a PDE5 inhibitor, tadalafil, with a mesothelin-specific vaccine, anti–programmed cell death protein 1, and anti–cytotoxic T lymphocyte–associated protein 4 yields antitumor efficacy even against immune-resistant PDAC. To determine immunologic advantages conferred by tadalafil, we profiled the TiME using mass cytometry and single-cell RNA-sequencing analysis with Domino to infer intercellular signaling. Our analyses demonstrated that tadalafil reprograms myeloid cells to be less immunosuppressive. Moreover, tadalafil synergized with the vaccine, enhancing T cell activation including mesothelin-specific T cells. Tadalafil treatment was also associated with myeloid/T cell signaling axes important for antitumor responses (e.g., Cxcr3, Il12). Our study shows that PDE5 inhibition combined with vaccine-based immunotherapy promotes pro-inflammatory states of myeloid cells, activation of T cells, and enhanced myeloid/T cell crosstalk to yield antitumor efficacy against immune-resistant PDAC.
Authors
Nicole E. Gross, Zhehao Zhang, Jacob T. Mitchell, Soren Charmsaz, Alexei G. Hernandez, Erin M. Coyne, Sarah M. Shin, Diana Carolina Vargas Carvajal, Dimitrios N. Sidiropoulos, Yeonju Cho, Guanglan Mo, Xuan Yuan, Courtney Cannon, Jayalaxmi Suresh Babu, Melissa R. Lyman, Todd Armstrong, Luciane T. Kagohara, Katherine M. Bever, Dung T. Le, Elizabeth M. Jaffee, Elana J. Fertig, Won Jin Ho
Figure 1
The addition of tadalafil to ICIs and mesothelin expressing listeria vaccine diminishes tumor growth.
