Research
Research Overview
The tumor microenvironment remains a challenging area of research, because of a large number of actors such as the myofibroblasts (MF), extracellular matrix (ECM), immune cells interacting, and microbiome in a dynamic fashion with the cancer cells that determines the overall outcome. Our research is primarily focused on understanding how tumor microenvironmental factors such as cytokines and chemokines synergize with tumor intrinsic oncogenic pathways for tumor initiation and progression.
The fungal microbiome regulates the pancreatic cancer tumor microenvironment. Gut microbes can interact with the host and modulate disease pathogenesis and response to therapy. We and others have found that microbes can colonize the pancreas and play a role in PDAC tumorigenesis and progression. Specifically, we showed that the mycobiome present in the gut lumen migrates to the pancreas via the sphincter of Oddi. The intratumor fungi then activate a toll-like receptor (TLR) mediated signaling cascade that leads to the secretion of a damage associated molecular pattern (DAMP) molecule, IL-33 into the tumor microenvironment. The secreted IL-33 recruits and expands pro-tumorigenic immunocytes innate lymphoid cell 2 (ILC2), TH2 and eosinophil. These immunocytes upon activation by IL-33 secretes effector cytokines such as IL-4, IL-13 and IL-4 which creates a tumor permissive microenvironment.
Further, we discovered that oncogenic KrasG12D induces IL-33 expression and that genetic deletion of IL-33 or anti-fungal treatment each leads to robust PDAC tumor regression. This mechanism of cooperative interactions of intratumor fungi with cancer cells and priming type 2 immune responses to accelerate tumor progression identifies potential therapeutic strategies for PDAC.
Type 2 immune response in pancreatic cancer. Immuno-phenotyping of pancreatic cancer revealed a dramatic expansion of TH2 (CD4+Gata3+CCR4+) cells within the CD4+ T cell population in the PDAC TME (72.1%) compared with the normal pancreas (8.33%) and spleen (0.4%). This was accompanied by a significant increase in ILC2 cells (Lin−Sca1+ST2+) in the PDAC TME (74.2%) compared with the normal pancreas (7.96%), spleen (0.18%), and bone marrow (0.25%). Specifically, the frequency of ILC2 cells was approximately 60% of lineage-negative (Lin−) cells in the PDAC (KPC model) compared with <10% in the normal pancreas and ∼25% in PanIN. Similarly, the frequency of ILC2 cells was approximately 45% of Lin− cells in the PDAC (iKPC model) compared with <10% in the normal pancreas. Further, single-cell RNA sequencing (scRNA-seq) analysis identified the presence of the type 2 immunocytes in the PDAC TME. Using previously reported gene signatures for TH2 and ILC2, we found that the TH2 cluster was enriched for Cd4, Gata3, and Ccr4 genes and ILC2 clusters were enriched for Hes1, Hs3st1, and Il1rl1 genes, which are bona fide markers of TH2 and ILC2 cells, respectively. Finally, we analyzed fresh human PDAC samples by flow cytometry and found that ILC2 cells accounted for 14.2% of the Lin− cells. Overall, these results show that the murine and human PDAC TME contain abundant TH2 and ILC2s cells.
Role of TH2 cells in pancreatic cancer progression. A hallmark feature of PDAC is an extensive desmoplastic stroma comprised of myofibroblasts (MF), extracellular matrix (ECM), and immune cells. Most studies have focused on cytotoxic T cells, NK cells and M1 macrophages in inhibiting tumor initiation and progression. Less explored is the potential role of the immune cells, which are early responders to the mutation events in PDAC, especially CD4+ cells in disease promotion. CD4+ T helper cells, with its multiple subtypes (TH 1, 2, 9, 10, 17, 22) are critical for inflammatory processes in cancer. Among them, TH2 subtypes can promote tumor growth via various mechanisms that include induction of M2 macrophage polarization.
Previously, we have identified a unique role of TH2 polarized CD4 T-cells in collaborating with oncogenic Kras in transforming indolent PanIN into malignant pancreatic tumor. Our data show an important role of tumor infiltrating TH2 cells and its prototypic cytokines IL4 and IL13 driving tumor initiation and progression. Concurrently, oncogenic Kras upregulates the expression of cytokine receptors IL2rg, IL4ra and IL13ra1 that, upon IL4 and IL13 engagement, activates the Jak1-Stat6 pathway. The goal of this project is to identify factors that are released by cancer cells that attract TH2 cells into the tumor microenvironment and if blocking of TH2 infiltration mediated pathway has any therapeutic benefit.
Cytokine mediated metabolic reprogramming in cancer. A major component of tumor microenvironment is the secreted factors arising from infiltrating immune cells, stroma and cancer cells itself, which shapes the overall trajectory of the disease. Transcriptomic analysis has identified cMyc upregulation upon treatment with IL4 or IL13. In agreement with cMyc roles in influencing tumor metabolism, targeted metabolomic analysis have shown an increase in glycolysis upon treatment with IL4 or IL13. In consistence with increase in glycolysis upon IL4 or IL13 treatment, there is an increase in expression of glycolytic enzymes (Hexokinase II, lactate dehydrogenase and pyruvate dehydrogenase). This data is especially intriguing because prior in vitro studies failed to capture the dependence of cancer cells on glycolysis, probably because of the absence of these vital cytokines in vitro culture media forcing the cancer cells to utilize glutamine as carbon source. The goal of this project is to investigate the role of IL4 and/or IL13 in driving an alternative metabolic circuit especially the acceleration of glycolytic pathways. We will determine whether cMyc mediated metabolic shift is essential for cancer cell survival. We will use biochemical and metabolic techniques to understand whether cMyc increases the glucose consumption which contributes to cancer cell biomass leading to aggressive tumor growth.