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Breast cancer is the most commonly diagnosed cancer in the USA. Although advances in treatment over the past several decades have significantly improved the outlook for this disease, most women who are diagnosed with estrogen receptor positive disease remain at risk of metastatic relapse for the remainder of their life. The cellular source of late relapse in these patients is thought to be disseminated tumor cells that reactivate after a long period of dormancy. The biology of these dormant cells and their natural history over a patient’s lifetime is largely unclear. We posit that research on tumor dormancy has been significantly limited by the lack of clinically relevant models. This review will discuss existing dormancy models, gaps in biological understanding, and propose criteria for future models to enhance their clinical relevance.

Pancreatic cancer has the worst prognosis of all cancers due to disease aggressiveness and paucity of early detection platforms. We developed biomaterial scaffolds that recruit metastatic tumor cells and reflect the immune dysregulation of native metastatic sites. While this platform has shown promise in orthotopic breast cancer models, its potential in other models is untested. Herein, we demonstrate that scaffolds recruit disseminated pancreatic cells in the KPCY model of spontaneous pancreatic cancer prior to adenocarcinoma formation (3-fold increase in scaffold YFP + cells). Furthermore, immune cells at the scaffolds differentiate early- and late-stage disease with greater accuracy (0.83) than the natural metastatic site (liver, 0.50). Early disease was identified by an approximately 2-fold increase in monocytes. Late-stage disease was marked by a 1.5-2-fold increase in T cells and natural killer cells. The differential immune response indicated that the scaffolds could distinguish spontaneous pancreatic cancer from spontaneous breast cancer. Collectively, our findings demonstrate the utility of scaffolds to reflect immunomodulation in two spontaneous models of tumorigenesis, and their particular utility for identifying early disease stages in the aggressive KPCY pancreatic cancer model. Such scaffolds may serve as a platform for early detection of pancreatic cancer to improve treatment and prognosis.

Metastasis represents the greatest challenge to treatment of cancer patients. Biomaterial scaffolds that recruit tumor cells to a defined site in vivo are an emerging platform for the diagnosis, treatment, and study of metastasis. Recruitment of immune cells and metastatic tumor cells to a defined location provides a precision health platform to assess current clinical cancer biomarkers in a metastatic setting, and to define the next generation of biomarkers. These platforms represent an opportunity to create a molecular staging of metastasis that could aid in both the early diagnosis and treatment of metastasis.

For most cancers, metastasis is the point at which disease is no longer curable. Earlier detection of metastasis, when it is undetectable by current clinical methods, may enable better outcomes. We have developed a biomaterial implant that recruits metastatic cancer cells in mouse models of breast cancer. Here, we investigate spectral ultrasound imaging (SUSI) as a non-invasive strategy for detecting metastasis to the implanted biomaterial scaffolds. Our results show that SUSI, which detects parameters related to tissue composition and structure, identified changes at an early time point when tumor cells were recruited to scaffolds in orthotopic breast cancer mouse models. These changes were not associated with acellular components in the scaffolds but were reflected in the cellular composition in the scaffold microenvironment, including an increase in CD31 + CD45-endothelial cell number in tumor bearing mice. In addition, we built a classification model based on changes in SUSI parameters from scaffold measurements to stratify tumor free and tumor bearing status. Combination of a linear discriminant analysis and bagged decision trees model resulted in an area under the curve of 0.92 for receiver operating characteristics analysis. With the potential for early non-invasive detection, SUSI could facilitate clinical translation of the scaffolds for monitoring metastatic disease.

For female cancer survivors, premature ovarian insufficiency (POI) is a common complication of anticancer treatments. Ovarian tissue cryopreservation before treatment, followed by auto-transplantation after remission is a promising option to restore fertility and ovarian endocrine function. However, auto-transplantation is associated with the risk of re-introducing malignant cells harbored in the stroma of the ovarian autograft. To mitigate this risk, we investigated in this pilot study whether an immuno-isolating dual-layered poly(ethylene glycol)(PEG) capsule can retain cancer cells, while supporting folliculogenesis. The dual PEG capsule loaded with 1000 4T1 cancer cells retained 100% of the encapsulated cells in vitro for 21 days of culture. However, a greater cell load of 10,000 cells/capsule led to capsule failure and cells’ release. To assess the ability of the capsule to retain cancer cells, prevent metastasis, and support folliculogenesis in vivo we co-encapsulated cancer cells with ovarian tissue in the dual PEG capsule and implanted subcutaneously in mice. Control mice implanted with 2000 non-encapsulated cancer cells had tumors formed within 14 days and metastasis to the lungs. In contrast, no tumor mass formation or metastasis to the lungs was observed in mice with the same number of cancer cells encapsulated in the capsule. Our findings suggest that the immuno-isolating capsule may prevent the escape of the malignant cells potentially harbored in ovarian allografts and, in the future, improve the safety of ovarian tissue auto-transplantation in female cancer survivors.

The pre-metastatic niche - the accumulation of aberrant immune cells and extracellular matrix proteins in target organs - primes the initially healthy organ microenvironment and renders it amenable for subsequent metastatic cell colonization. By attracting metastatic cancer cells, mimics of the pre-metastatic niche offer both diagnostic and therapeutic potential. However, deconstructing the complexity of the niche by identifying the interactions between cell populations and the mediatory roles of the immune system, soluble factors, extracellular matrix proteins, and stromal cells has proved challenging. Experimental models need to recapitulate niche-population biology in situ and mediate in vivo tumour-cell homing, colonization and proliferation. In this Review, we outline the biology of the pre-metastatic niche and discuss advances in engineered niche-mimicking biomaterials that regulate the behaviour of tumour cells at an implant site. Such oncomaterials offer strategies for early detection of metastatic events, inhibiting the formation of the pre-metastatic niche, and attenuating metastatic progression.

Pancreatic cancer is a lethal malignancy with a 5-year survival rate of less than 10%. This poor prognosis is, in part, due to patients most often presenting with already metastatic disease. Pancreatic cancer is characterized by an abundant, reactive fibroinflammatory stroma, consisting of cancer-associated fibroblasts (CAFs) and infiltrating immune cells that send and receive signals to and from other nearby cells, including the tumor cells. The crosstalk between tumor cells and elements of the stroma results in an immunosuppressive tumor microenvironment both at the primary tumor and the sites of metastases. A key limitation in studying metastatic disease in mouse models is the inability to predict when the cancer cells will ultimately metastasize. In this study biomaterial scaffolds that mimic the premetastatic niche in vivo, by attracting immune cells followed by tumor cells, were used to longitudinally follow the metastasis process in individual animals. Biomaterial scaffolds were implanted subcutaneously to mimic the premetastatic niche in both syngeneic and spontaneous mouse (iKras* p53*) models of pancreatic cancer. Scaffolds were harvested 21 days post implantation and taken for histologic analysis to characterize the cellular infiltrate in response to the primary tumor. Histologic analysis (H&E, Gomori’s trichrome, and multiplex IHC) shows tumor cell colonization in the scaffold along with a robust immune and fibrotic response. To further characterize the scaffold infiltrate in control versus tumor-bearing mice, mass cytometry (CyTOF) and single-cell RNA sequencing (scRNA seq) analysis was performed. CyTOF analysis revealed the most abundant cell population is heterogenous myeloid cells, which are immunosuppressive in nature. Scaffolds from tumor-bearing animals have an increase in fibroblasts, and subsequently have fewer cytotoxic, CD8+ T cells. scRNA seq analysis of the scaffold infiltrate reveals CD8+ T cells from tumor-bearing animals express higher levels of the immune checkpoint, programmed cell death protein 1 (PD-1) and lower levels of the functional markers, perforin 1 and granzyme B, suggesting the CD8+ T cells are unable to perform their cytotoxic functions. Further analysis revealed a chemokine signaling axis, where fibroblasts recruit distinct subsets of myeloid cells. Taken together, the premetastatic niche (recapitulated by the biomaterial scaffolds) in pancreatic cancer has a high abundance of immunosuppressive myeloid cells, an increase in fibroblasts, and fewer CD8+ T cells, creating an immunosuppressive niche that allows for tumor cell colonization and growth. Future directions include blocking myeloid cell chemotaxis to the scaffold to prevent tumor cell dissemination and reduce metastatic burden. Citation Format: Samantha Kemp, Nina Steele, Eileen Carpenter, Veerin Sirihorachai, Grace Bushnell, Aaron Morris, Carlos Espinoza, Fatima Lima, Zeribe Nwosu, Sophia Orbach, Lonnie Shea, Filip Bednar, Howard Crawford, Marina Pasca di Magliano. Using biomaterial scaffolds to study the genesis of the immunosuppressive premetastatic niche in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr A25.

The onset of distant organ metastasis from primary breast cancer marks the transition to a stage IV diagnosis. Standard imaging modalities often detect distant metastasis when the burden of disease is high, underscoring the need for improved methods of detection to allow for interventions that would impede disease progression. Here, microporous poly(ϵ-caprolactone) scaffolds were developed that capture early metastatic cells and thus serve as a sentinel for early detection. These scaffolds were used to characterize the dynamic immune response to the implant spanning the acute and chronic foreign body response. The immune cell composition had stabilized at the scaffold after approximately 1 month and changed dramatically within days to weeks after tumor inoculation, with CD11b+Gr1hiLy6C− cells having the greatest increase in abundance. Implanted scaffolds recruited metastatic cancer cells that were inoculated into the mammary fat pad in vivo, which also significantly reduced tumor burden in the liver and brain. Additionally, cancer cells could be detected using a label-free imaging modality termed inverse spectroscopic optical coherence tomography, and we tested the hypothesis that subsequent removal of the primary tumor after early detection would enhance survival. Surgical removal of the primary tumor following cancer cell detection in the scaffold significantly improved disease-specific survival. The enhanced disease-specific survival was associated with a systemic reduction in the CD11b+Gr1hiLy6C− cells as a consequence of the implant, which was further supported by Gr-1 depletion studies. Implementation of the scaffold may provide diagnostic and therapeutic options for cancer patients in both the high-risk and adjuvant treatment settings. Cancer Res; 76(18); 5209–18. ©2016 AACR.

Objective: For most cancers, the formation of distant metastasis is the point at which clinical treatment shifts from curative intent to palliative care. At present, there is no clinical method to detect metastatic dissemination and colonization until radiologically evident, at which point organ function has already been compromised. The Shea laboratory has developed a biomaterial implant that acts as a synthetic pre-metastatic niche and recruits metastatic cancer cells in xenogeneic human and syngeneic mouse models of breast cancer. Scaffold implantation has facilitated detection of metastasis prior to colonization of organs and has been shown to reduce metastatic burden, resulting in enhanced survival with surgical intervention. Methods: Triple-negative breast cancer models were used in which tdTomato+ 4T1 or MDA-MB-231-BR cells were orthotopically inoculated into balb/c or NSG mice. Microporous polycaprolactone (PCL) scaffolds were fabricated using gas-foaming and poragen leaching and were subcutaneously implanted one month prior to tumor inoculation. High frequency ultrasound (US) was used to probe the scaffold for early detection of tumor cells prior to metastasis to organs. Human tumor cells were isolated from the scaffold (SCAF), primary tumor (PT), and a bone metastasis via MACS mouse cell depletion (Miltenyi) and grown into stable cell lines in vitro. Scratch, migration, invasion, mammosphere, cancer stem cell markers, RNA-seq, qRT-PCR, and HiC assays were performed to investigate behavioral differences between cell lines in vitro. Additionally, cell lines were inoculated into mice and investigated for metastatic ability. Results: Initial studies applied US for detection of metastatic cell arrival at the scaffold. The analysis of spectral imaging distinguished scaffolds from tumor bearing relative to tumor free mice. A cell line created from the scaffold (SCAF) was more aggressive in vitro, demonstrating higher levels of migration, invasion, mammosphere formation, and proportion of cancer stem cells compared to PT. SCAF cells were also found to be ~30x more metastatic to the lung in vivo compared to PT cells (SCAF 10,150±7792 PT 354±296 cells per lung). RNA-seq identified 14232 genes with measured expression, 2901 of which were differentially expressed (p 0.6) between scaffold and primary tumor cells. Conclusions: Biomaterial scaffolds capable of recruiting metastatic tumor cells in vivo can serve as a platform for early detection and intervention, and also provide a tool to study metastasis in vivo and the properties of the early metastatic cells. Citation Format: Grace G. Bushnell, Tejaswini P. Hardas, Rachel M. Hartfield, Yining Zhang, Robert S. Oakes, Adeline Hong, Jacqueline S. Jeruss, Lonnie D. Shea. Biomaterial scaffolds that capture metastatic tumor cells in vivo to detect, treat, and study mechanisms of the premetastatic niche and metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5000.

Background Intraoperative rupture (IOR) is a rare, but potentially morbid complication of endovascular aneurysm coil embolization. Yet, IOR predictors have remained relatively uninvestigated in relation to coil design. Objective To develop a novel in vitro aneurysm model to characterize forces exerted by coils of different design on the aneurysm during endovascular embolization that are hypothesized to contribute to IOR. Methods A 3-mm saccular aneurysm model was developed with flat latex membrane at the dome apex. Membrane deflection was observed throughout simulated embolization and converted to force measurement. Simultaneous coil insertion and force measurement were accomplished with a compression strength-testing machine. Membrane and insertion forces across coil type, microcatheter tip placement, and insertion rate were evaluated. Results Insertion force and force directly on the aneurysm wall exhibited a difference, with framing coils exerting greatest force, followed by filling and finishing coils. Regarding microcatheter placement, a similar graded response in membrane and insertion forces was observed with positioning in the top-third of the aneurysm generating the greatest force compared with central and bottom-third placement. Insertion rate was also a factor with the slowest rate (10 mm/min) exhibiting the greatest membrane force, followed by lower forces at 30 and 50 mm/min. A multiple linear regression model was created to assess the contributions of each factor toward aneurysm forces. Conclusion Increased force on the aneurysm is associated with framing coil use, microcatheter placement proximal to aneurysm dome, and slow insertion rate. Further characterization remains necessary to reduce IOR risk, especially concerning the contributions of insertion rate.