(left to right) Dr. Massar Alsamraae, Postdoctoral Trainee; Mackenzie Hutchinson, Cancer Biology Master's student; Dr. Leah Cook, Assistant Professor; Diane Costanzo-Garvey, Technician; Catherine Johnson, Cancer Biology PhD student.
The majority of cancer-related deaths are due to tumor progression to metastasis. Efficient metastasis requires the spread of cancer cells to tissue sites distant and foreign to the primary tumor, and growth into secondary tumors. This process requires modification of the foreign tissue microenvironment and recruitment and assistance from surrounding stromal cells, including immune cells. Polymorphonuclear Leukocytes/Neutrophils are “first-responder” innate immune cells that mount a rapid response during inflammation and infections that is resolved by macrophages. In recent years, however, PMNs have been shown to be recruited into tumor microenvironments where they can promote tumor growth via: 1) the secretion of growth promoting cytokines, such as transforming growth factor beta, 2) oxidative burst, which inhibits tumor growth while also suppressing cytotoxic T cell function, 3) neutrophil extracellular traps (NETs), scaffolds of decondensed chromatin that harbor DNAses. The main focus of the Cook lab involves identifying the contribution of PMNs in: 1) tumor growth at sites of metastasis and 2) tumor progression to the development of distant metastases. We are currently focused on bone metastatic prostate cancer and pancreatic cancer.
Neutrophils in the Prostate Tumor Bone microenvironment: Prostate cancer metastasizes to bone more frequently than any other tissue site. Bone metastatic prostate cancer (BM-PCa) is the deadliest aspect of prostate cancer and is currently incurable. In bone, PCa cells induce excessive bone breakdown and abnormal bone formation resulting in the release of bone-derived growth factors, such as transforming growth factor beta (TGFβ), which drive tumor growth. PCa cells rely heavily on interactions with bone resident cells to survive and proliferate in bone. Although this seems like a straightforward process, current bone-targeting therapies have been unsuccessful in improving patient survival. Targeted immunotherapies have shown promising results for treating less advanced BM-PCa (i.e. patients with fewer than 20 bone lesions), demonstrating that immune cells can play a critical role in regulating BM-PCa progression. The most abundant immune cell in bone are neutrophils. Recent studies demonstrated the existence of two distinct PMN populations in tumors: cytotoxic anti-tumoral (N1) and immunosuppressive pro-tumoral (N2) PMNs, with emergence of the latter being regulated by the accumulation of TGFβ.
Emerging data from the Cook lab demonstrates that neutrophils heavily infiltrate regions of PCa in bone as identified in patient bone specimens. Our preliminary studies revealed that: 1) BM-PCa, compared to non-metastatic PCa stimulates expansion of PMNs dependent on TGFbeta, 2) BM-PCa suppress N1 PMNs in vitro and 3) BM-PCa evades PMN cell killing to grow in bone. Thus, we are testing the hypothesis that bone metastatic PCa cells evade cytotoxic PMN cell killing potentially by TGFβ-mediated skewing of PMN function. This hypothesis is being tested using analyses of BM-PCa media on PMN function, gene expression analyses of PCa patient-derived PMNs, and in vivo mouse bone metastasis models therapeutically targeting PMNs and models examining the role of MSCs on PMN polarization in bone. Our main goal is to identify novel immunotherapeutic targets for treating and curing bone metastatic prostate cancer.
Neutrophils in Pancreatic Cancer: Pancreatic cancer (PanCan) is an aggressive disease and is the third leading cause of cancer-related deaths in the United States. Although PanCan is associated with the accumulation of specific mutations, including constitutive KRAS signaling and the loss of tumor suppressor genes TP53, CDKN2A, and Smad 4, targeted therapies against these known mutations have failed to be clinically effective. Stromal cells can account for nearly 90% of pancreatic tumor volume and contribute significantly to tumor progression. This would suggest that efficacious therapeutic approaches would require dual targeting of both the tumor and surrounding microenvironment, which is comprised of cancer-associated fibroblasts, stellate cells, and an abundant population of macrophages and PMNs. Immunohistochemical analysis of tumor samples from the UNMC Rapid Autopsy program (RAP) revealed heavy PMN infiltration in pancreatic tumors of patients treated with the standard chemotherapy, gemcitabine, in comparison to untreated patients, suggesting that PMNs contribute, in some part, to cancer response to therapy. Preliminary findings from my group revealed that treated patients exhibit significantly more NETs in the primary tumor site than in metastatic sites. Likewise, PMNs cultured with PanCan cells in vitro kill significantly more non-metastatic PanCan (MiaPaCa-2, AsPC-1) compared to metastatic cells (Capan-1, S2013). Inhibition of NETosis/NET secretion completely rescued PMN-mediated killing. Additionally, PanCan with acquired chemotherapy resistance fail to induce PMN cytotoxicity. It is unclear how this phenomenon impacts tumor growth and disease progression or how acquired therapy-resistance impacts this phenotype. Based on these preliminary findings, we hypothesize that pancreatic cancer progression and emergence of therapeutic resistance is mediated, in part, by PMN recruitment and function. This hypothesis is currently being tested using PanCan transplantation models of metastasis and therapy resistance with a primary goal of identifying immunotherapeutic targets for preventing PanCan progression and therapy resistance.