S. Peter Goedegebuure

Cancer immunotherapy generally offers limited clinical benefit without coordinated strategies to mitigate the immunosuppressive nature of the tumor microenvironment. Critical drivers of immune escape in the tumor microenvironment include tumor-associated macrophages and myeloid-derived suppressor cells, which not only mediate immune suppression, but also promote metastatic dissemination and impart resistance to cytotoxic therapies. Thus, strategies to ablate the effects of these myeloid cell populations may offer great therapeutic potential. In this report, we demonstrate in a mouse model of pancreatic ductal adenocarcinoma (PDAC) that inhibiting signaling by the myeloid growth factor receptor CSF1R can functionally reprogram macrophage responses that enhance antigen presentation and productive antitumor T-cell responses. Investigations of this response revealed that CSF1R blockade also upregulated T-cell checkpoint molecules, including PDL1 and CTLA4, thereby restraining beneficial therapeutic effects. We found that PD1 and CTLA4 antagonists showed limited efficacy as single agents to restrain PDAC growth, but that combining these agents with CSF1R blockade potently elicited tumor regressions, even in larger established tumors. Taken together, our findings provide a rationale to reprogram immunosuppressive myeloid cell populations in the tumor microenvironment under conditions that can significantly empower the therapeutic effects of checkpoint-based immunotherapeutics.

PURPOSE: To determine the role of the CCL2/CCR2 axis and inflammatory monocytes (CCR2(+)/CD14(+)) as immunotherapeutic targets in the treatment of pancreatic cancer. EXPERIMENTAL DESIGN: Survival analysis was conducted to determine if the prevalence of preoperative blood monocytes correlates with survival in patients with pancreatic cancer following tumor resection. Inflammatory monocyte prevalence in the blood and bone marrow of patients with pancreatic cancer and controls was compared. The immunosuppressive properties of inflammatory monocytes and macrophages in the blood and tumors, respectively, of patients with pancreatic cancer were assessed. CCL2 expression by human pancreatic cancer tumors was compared with normal pancreas. A novel CCR2 inhibitor (PF-04136309) was tested in an orthotopic model of murine pancreatic cancer. RESULTS: Monocyte prevalence in the peripheral blood correlates inversely with survival, and low monocyte prevalence is an independent predictor of increased survival in patients with pancreatic cancer with resected tumors. Inflammatory monocytes are increased in the blood and decreased in the bone marrow of patients with pancreatic cancer compared with controls. An increased ratio of inflammatory monocytes in the blood versus the bone marrow is a novel predictor of decreased patient survival following tumor resection. Human pancreatic cancer produces CCL2, and immunosuppressive CCR2(+) macrophages infiltrate these tumors. Patients with tumors that exhibit high CCL2 expression/low CD8 T-cell infiltrate have significantly decreased survival. In mice, CCR2 blockade depletes inflammatory monocytes and macrophages from the primary tumor and premetastatic liver resulting in enhanced antitumor immunity, decreased tumor growth, and reduced metastasis. CONCLUSIONS: Inflammatory monocyte recruitment is critical to pancreatic cancer progression, and targeting CCR2 may be an effective immunotherapeutic strategy in this disease.

Most cancer treatment strategies target cell proliferation, angiogenesis, migration, and intravasation of tumor cells in an attempt to limit tumor growth and metastasis. An in vitro platform to assess tumor progression and drug sensitivity could provide avenues to enhance our understanding of tumor metastasis as well as precision medicine. We present a microfluidic platform that mimics biological mass transport near the arterial end of a capillary in the tumor microenvironment. A central feature is a quiescent perfused 3D microvascular network created prior to loading tumor cells or patient-derived tumor organoids in an adjacent compartment. The physiological delivery of nutrients and/or drugs to the tumor then occurs through the vascular network. We demonstrate the culture, growth, and treatment of tumor cell lines and patient-derived breast cancer organoids. The platform provides the opportunity to simultaneously and dynamically observe hallmark features of tumor progression including cell proliferation, angiogenesis, cell migration, and tumor cell intravasation. Additionally, primary breast tumor organoids are viable in the device for several weeks and induce robust sprouting angiogenesis. Finally, we demonstrate the feasibility of our platform for drug discovery and personalized medicine by analyzing the response to chemo- and anti-angiogenic therapy. Precision medicine-based cancer treatments can only be realized if individual tumors can be rapidly assessed for therapeutic sensitivity in a clinically relevant timeframe (⪅14 days). Our platform indicates that this goal can be achieved and provides compelling opportunities to advance precision medicine for cancer.