NK and NKT cells in the pathogenesis of Hidradenitis suppurativa: Novel therapeutic strategy through targeting of CD2

Hidradenitis suppurativa (HS) is a chronic debilitating inflammatory skin disease with poorly understood pathogenesis. Single-cell RNAseq analysis of HS lesional and healthy individual skins revealed that NKT and NK cell populations were greatly expanded in HS, and they expressed elevated CD2, an activation receptor. Immunohistochemistry analyses confirmed significantly expanded numbers of CD2+ cells distributed throughout HS lesional tissue, and many co-expressed the NK marker, CD56. While CD4+ T cells were expanded in HS, CD8 T cells were rare. CD20+ B cells in HS were localized within tertiary follicle like structures. Immunofluorescence microscopy showed that NK cells (CD2 + CD56 dim ) expressing perforin, granzymes A and B were enriched within the hyperplastic follicular epidermis and tunnels of HS and juxtaposed with apoptotic cells. In contrast, NKT cells (CD2 + CD3 + CD56 bright ) primarily expressed granzyme A and were associated with α-SMA expressing fibroblasts within the fibrotic regions of the hypodermis. Keratinocytes and fibroblasts expressed high levels of CD58 (CD2 ligand) and they interacted with CD2 expressing NKT and NK cells. The NKT/NK maturation and activating cytokines, IL-12, IL-15 and IL-18, were significantly elevated in HS. Inhibition of cognate CD2-CD58 interaction with blocking anti-CD2 mAb in HS skin organotypic cultures resulted in a profound reduction of the inflammatory gene signature and secretion of inflammatory cytokines and chemokines in the culture supernate. In summary, we show that a cellular network of heterogenous NKT and NK cell populations drives inflammation, tunnel formation and fibrosis in the pathogenesis of HS. Furthermore, CD2 blockade is a viable immunotherapeutic approach for the management of HS.

Altered sphingolipid pathway in SARS-CoV-2 infected human lung tissue

Introduction

The SARS-CoV-2 mediated COVID-19 pandemic has impacted millions worldwide. Hyper-inflammatory processes, including cytokine storm, contribute to long-standing tissue injury and damage in COVID-19. The metabolism of sphingolipids as regulators of cell survival, differentiation, and proliferation has been implicated in inflammatory signaling and cytokine responses. Sphingosine-kinase-1 (SK1) and ceramide-synthase-2 (CERS2) generate metabolites that regulate the anti- and pro-apoptotic processes, respectively. Alterations in SK1 and CERS2 expression may contribute to the inflammation and tissue damage during COVID-19. The central objective of this study is to evaluate structural changes in the lung post-SARS-CoV-2 infection and to investigate whether the sphingolipid rheostat is altered in response to SARS-CoV-2 infection.

Methods

Central and peripheral lung tissues from COVID-19+ or control autopsies and resected lung tissue from COVID-19 convalescents were subjected to histologic evaluation of airspace and collagen deposisiton, and immunohistochemical evaluation of SK1 and CERS2.

Results

Here, we report significant reduction in air space and increase in collagen deposition in lung autopsy tissues from patients who died from COVID-19 (COVID-19+) and COVID-19 convalescent individuals. SK1 expression increased in the lungs of COVID-19+ autopsies and COVID-19 convalescent lung tissue compared to controls and was mostly associated with Type II pneumocytes and alveolar macrophages. No significant difference in CERS2 expression was noted. SARS-CoV-2 infection upregulates SK1 and increases the ratio of SK1 to CERS2 expression in lung tissues of COVID-19 autopsies and COVID-19 convalescents.

Discussion

These data suggest an alteration in the sphingolipid rheostat in lung tissue during COVID-19, suggesting a potential contribution to the inflammation and tissue damage associated with viral infection.

Mitochondrial transfer from cancer associated fibroblasts increases migration in aggressive breast cancer

Cancer associated fibroblasts (CAFs) have distinct roles within the tumor microenvironment, which may impact the mode and efficacy of tumor cell migration. CAFs are known to increase invasion of less-aggressive breast cancer cells through matrix remodeling and leader-follower dynamics. Here, we demonstrate that CAFs communicate with breast cancer cells through the formation of contact-dependent tunneling nanotubes (TNTs) that allow for the exchange of cargo between cell types. The transferring of CAF mitochondria is an integral cargo component, and CAF mitochondria are sufficient to increase the 3D migration of cancer cells. This cargo transfer results in an increase in mitochondrial ATP production in cancer cells while having negligible impact on glycolytic ATP production. Manually increasing mitochondrial oxidative phosphorylation (OXPHOS) by providing extra substrates for OXPHOS fails to enhance cancer cell migration unless glycolysis is maintained at a constant level. Together, these data indicate that tumor-stromal crosstalk via TNTs and the associated metabolic symbiosis is a finely controlled mechanism by which tumor cells co-opt their microenvironment to promote cancer progression and may become a potential therapeutic target.

Abstract B33: Tumor-stromal response to immune checkpoint blockade within patient tissue derived three-dimensional lung tumor models

The tumor microenvironment is a key regulator of tumor biology and response to therapeutic intervention, with intercellular communication between tumor and stromal cells regulating growth and progression. While two dimensional cultures are commonly utilized for in vitro preclinical studies, they do not recapitulate the tissue microenvironment or three dimensional tissue architecture. Herein, we utilize tissue engineering strategies and patient-derived specimen to develop ex vivo non-small cell lung tumor models. These models allow for evaluation of tumor-stromal interactions and response to immune directed therapies while keeping the native tissue microenvironment intact. For this study, tumor models were generated utilizing remnant lung tumor specimen from consented patients undergoing surgical tumor resection. 5 mm diameter tissue cores were placed in a volume of extracellular matrix within a perfusion bioreactor platform, and through-channels were generated to provide nutrient circulation during ex vivo culture. Spatial profiling using the Nanostring GeoMx platform, multiplex cytokine analysis, histologic and flow cytometric analyses were performed following culture. Primary human tumor specimens cultured ex vivo maintain histologic architecture and representative cell populations following 14 days culture. Tissues treated with an anti-programmed cell death protein 1 (PD-1) blocking antibody showed reduced IL-6 (380.8 ±133.9 pg/mL) levels within the circulating media when compared to IgG control treated tissues (1119 ±382.9 pg/mL, p=0.08). Spatial profiling showed increased proportions of dividing T cells (2.27 ± 1.02 IgG vs. 8.28 ± 1.171 anti-PD-1; p=0.02) and CD8+ memory T cells (0.09 ± 0.09 IgG vs. 1.74 ± 0.64 anti-PD-1; p=0.04) and a trend towards more natural killer cells (3.88 ± 0.73 IgG vs. 6.56 ± 3.14 anti-PD-1; p=0.067), along with decreased proportions of macrophages (14.33 ± 2.16 IgG vs. 6.44 ± 0.59 anti-PD-1; p=0.004) near the tumor in tissues treated with anti-PD-1 when compared to control. Additionally, genes within the tumor immune signature associated with programmed cell death ligand 1 suppression, anti-tumor cytotoxicity and T cell response, including CXCR6, CCL3, NKG7, CMKLR1, CD27 & PSMB10, were upregulated and genes associated with immune suppression, including IDO and HLA-E, were downregulated with anti-PD-1 treatment when compared to IgG control. Moving forward, this platform will allow for extensive characterization of tumor-stromal interactions, response to therapeutic intervention, and therapeutic resistance in a patient specific manner. Funding: Nanostring DSP Cancer Transcriptome Atlas Award; 1R21 CA263365-01A1; Respiratory Health Association Lung Cancer Award (RHA2022-01-LC).

Citation Format: Kayla F. Goliwas, Anthony M. Wood, Young-il Kim, Joel L. Berry, James M. Donahue, Jessy S. Deshane. Tumor-stromal response to immune checkpoint blockade within patient tissue derived three-dimensional lung tumor models [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B33.

Sphingolipids in Lung Pathology in the Coronavirus Disease Era: A Review of Sphingolipid Involvement in the Pathogenesis of Lung Damage

Sphingolipids are bioactive lipids involved in the regulation of cell survival, proliferation, and the inflammatory response. The SphK/S1P/S1PR pathway (S1P pathway) is a driver of many anti-apoptotic and proliferative processes. Pro-survival sphingolipid sphingosine-1-phosphate (S1P) initiates its signaling cascade by interacting with various sphingosine-1-phosphate receptors (S1PR) through which it is able to exert its pro-survival or inflammatory effects. Whereas sphingolipids, including ceramides and sphingosines are pro-apoptotic. The pro-apoptotic lipid, ceramide, can be produced de novo by ceramide synthases and converted to sphingosine by way of ceramidases. The balance of these antagonistic lipids and how this balance manifests is the essence of the sphingolipid rheostat. Recent studies on SARS-CoV-2 have implicated the S1P pathway in the pathogenesis of novel coronavirus disease COVID-19-related lung damage. Accumulating evidence indicates that an aberrant inflammatory process, known as "cytokine storm" causes lung injury in COVID-19, and studies have shown that the S1P pathway is involved in signaling this hyperinflammatory response. Beyond the influence of this pathway on cytokine storm, over the last decade the S1P pathway has been investigated for its role in a wide array of lung pathologies, including pulmonary fibrosis, pulmonary arterial hypertension (PAH), and lung cancer. Various studies have used S1P pathway modulators in models of lung disease; many of these efforts have yielded results that point to the potential efficacy of targeting this pathway for future treatment options. Additionally, they have emphasized S1P pathway's significant role in inflammation, fibrosis, and a number of other endothelial and epithelial changes that contribute to lung damage. This review summarizes the S1P pathway's involvement in COVID-19 and chronic lung diseases and discusses the potential for targeting S1P pathway as a therapeutic option for these diseases.

Local SARS-CoV-2 peptide-specific Immune Responses in Convalescent and Uninfected Human Lung Tissue Models

Multi-specific and long-lasting T cell immunity have been recognized as indicators for long term protection against pathogens including the novel coronavirus SARS-CoV-2, the causative agent of the COVID-19 pandemic. Functional significance of peripheral memory T cell subsets in COVID-19 convalescents (CONV) are beginning to be appreciated; but little is known about lung resident memory T cell (lung TRM) responses and their role in limiting the severity of SARS-CoV-2 infection. Here, we utilize a perfusion three dimensional (3D) human lung tissue model and identify pre-existing local T cell immunity against SARS-CoV-2 spike protein and structural antigens in the lung tissues. We report ex vivo maintenance of functional multi-specific IFN-γ secreting lung TRM in CONV and their induction in lung tissues of vaccinated CONV. Importantly, we identify SARS-CoV-2 spike peptide-responding B cells in lung tissues of CONV in ex vivo 3D-tissue models. Our study highlights a balanced and local anti-viral immune response in the lung and persistent induction of TRM cells as an essential component for future protection against SARS-CoV-2 infection. Further, our data suggest that inclusion of multiple viral antigens in vaccine approaches may broaden the functional profile of memory T cells to combat the severity of coronavirus infection.

Extracellular Vesicle Mediated Tumor-Stromal Crosstalk Within an Engineered Lung Cancer Model

Tumor-stromal interactions within the tumor microenvironment (TME) influence lung cancer progression and response to therapeutic interventions, yet traditional in vitro studies fail to replicate the complexity of these interactions. Herein, we developed three-dimensional (3D) lung tumor models that mimic the human TME and demonstrate tumor-stromal crosstalk mediated by extracellular vesicles (EVs). EVs released by tumor cells, independent of p53 status, and fibroblasts within the TME mediate immunomodulatory effects; specifically, monocyte/macrophage polarization to a tumor-promoting M2 phenotype within this 3D-TME. Additionally, immune checkpoint inhibition in a 3D model that included T cells showed an inhibition of tumor growth and reduced hypoxia within the TME. Thus, perfused 3D tumor models incorporating diverse cell types provide novel insights into EV-mediated tumor-immune interactions and immune-modulation for existing and emerging cancer therapies.

Abstract 1711: Mechanical strain induces phenotypic changes in breast cancer cells and promotes immunosuppression in the tumor microenvironment

Introduction: Breast cancer (BCa) occurs with a complex, three-dimensional microenvironment that involves heterogeneous biochemical and biophysical cues. Understanding how mechanical properties within the tumor microenvironment (TME) regulate breast cancer phenotype and immunosuppression is of great interest.

Materials and Methods: BCa cells (MCF-7, MDA-MB-231 or 4T1.2) cultured to confluence on collagen coated FlexCell culture plates were subjected to 10% uniaxial cyclic/oscillatory strain at 0.3 Hz, or 10% constant strain, or no strain for 48 hours. They were isolated for analysis of proliferation (MTT assay and cell count by trypan blue), and migration (transwell and wound healing assay). Exosomes from conditioned media were isolated by differential centrifugation or using the Total Exosome Isolation kit. The purified exosomes were quantified by NanoSight and characterized by ImageStream. 5 × 105 4T1.2 cells or PKH67-labeled strained or control cells were injected into the mammary fat pad of BALB/c mice. Tumor volume was measured at the indicated time points after injection. Tumor-infiltrating immune cells and the internalization of exosomes were analyzed by flow cytometry on day 14 post implantation. In some experiments, on day 6 after tumor injection, 7.5 × 108 PHK67-labeled tumor cell-derived exosomes or PBS were injected into the tumor nodule. Tumor tissues were harvested for analysis of the internalization of exosomes by immune cells and tumor cells on days 2 and 8 after exosome injection.

Results: We show that mechanical strain enhanced the proliferation and migration of BCa cells in vitro. Exosome concentrations produced by triple negative breast cancer (TNBC) cells were increased following exposure to oscillatory strain. Phenotyping exosomes by ImageStream showed that the percentages of CD81+PD-L1+ and CD63+PD-L1+ exosomes were increased after exposure to oscillatory strain. Using a syngeneic orthotopic mouse model of TNBC, we showed that preconditioning with mechanical strain increased tumor growth. The percentages of tumor-infiltrating monocytic myeloid-derived suppressor cells (M-MDSC) and recruited macrophages were increased while CD8+ T cells decreased in the TME of mice implanted with 4T1.2 cells preconditioned with oscillatory strain. Further, exosome internalizations by M-MDSC and recruited macrophages were elevated when tumor cells were preconditioned with oscillatory strain. Moreover, exosomes internalization by immune cells and tumor cells in TME were identified by PKH67 positive signals on days 2 and 8 after injection of PKH67-labeled exosomes into tumor nodules by flow cytometry analyses and confocal microscope imaging.

Conclusions: Our data indicate that exposure to mechanical strain promotes invasive and pro-tumorigenic phenotypes in BCa, alters exosome production by BCa and induces immunosuppression in the TME.

Citation Format: Yong Wang, Kayla F. Goliwas, Paige E. Severino, Kenneth Hough, Derek Van Vessem, Hong Wang, Sultan Tousif, Roy P. Koomullil, Andra R. Frost, Selvarangan Ponnazhagen, Joel L. Berry, Jessy S. Deshane. Mechanical strain induces phenotypic changes in breast cancer cells and promotes immunosuppression in the tumor microenvironment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1711.

Moving Immune Therapy Forward Targeting TME

The host immune system shapes the fate of tumor progression. Hence, manipulating patients' immune system to activate host immune responses against cancer pathogenesis is a promising strategy to develop effective therapeutic interventions for metastatic and drug-resistant cancers. Understanding the dynamic mechanisms within the tumor microenvironment (TME) that contribute to heterogeneity and metabolic plasticity is essential to enhance the patients' responsiveness to immune targeted therapies. Riera-Domingo et al. (Riera-Domingo C, Audige A, Granja S, Cheng WC, Ho PC, Baltazar F, Stockmann C, Mazzone, M. Physiol Rev 100: 1-102, 2020) describe the immune landscape within the TME and highlight the significance of metabolic and hypoxic signatures that impact immune function and response to immunotherapy strategies. Current literature in this field confirms that targeting tumor metabolism and the acidic microenvironment commonly associated with tumors may present viable strategies to modulate the host immune system in favor of response to immune targeted therapies. However, development of better tools to understand tumor-immune interactions and identify mechanisms driving nonresponders, more innovative clinical trial design, and new therapies will need to be identified to move the field forward. Personalized immune therapies incorporating metabolic and microbiome-based gene signatures to influence the therapeutic response and novel methods to generate immunologically "hot" tumors are at the forefront of immunotherapy currently. The combination of these approaches with clinically approved immunotherapies will be valuable moving forward.

Abstract B23: Engineered three-dimensional lung tumor mimics maintain tissue heterogeneity allowing for investigation of tumor-stromal interactions

The tumor microenvironment is a key regulator of tumor biology and response to therapeutic intervention, with intercellular communication between tumor and stromal cells known to regulate growth and progression. While two-dimensional cell culture is the most common method utilized for in vitro preclinical studies, it creates an artificial environment that does not take into account critical tissue components, including the tissue microenvironment (i.e., matrix proteins and stromal cell populations) and the three-dimensional tissue architecture/dimensionality. Recently, in vitro engineered tissues have been implemented as surrogates of human pathophysiology in biomedical and pharmaceutical research. Herein we utilize tissue engineering strategies to develop in vitro non-small cell lung tumor mimics that include key tissue components, including matrix proteins and stromal cell populations, utilizing patient-derived specimen. With the inclusion of stromal cell populations, these tumor mimics allow for evaluation of tumor-stromal interactions and could be utilized to determine the impact of these interactions on therapeutic response. Engineered tumor mimics were generated utilizing freshly isolated lung tumor specimen from consented patients undergoing surgical tumor resection. 5-mm-diameter tissue cores were produced and placed in a volume of extracellular matrix (ECM) within the bioreactor platform and maintained via a closed perfusion platform to provide nutrient circulation. Histologic and flow cytometric analyses were performed to evaluate cellular heterogeneity within the tumor mimics following culture. Primary human lung tumor specimens cultured ex vivo in the engineered tumor mimic platform maintain histologic architecture and representative cell populations, including endothelial cells (CD31+,10.46%), epithelial cells (EpCAM+,25.15%), fibroblasts (CD90+, 7.23%), CD8+ T cells (CD3+CD8+, 2.95%), and macrophages (CD14+CD64+CD11b+, 9.25%) following 14 days’ culture. Additionally, a tumor-promotive microenvironment is supported by this platform with maintenance of monocytic and granulocytic myeloid-derived suppressor cells (8.59% and 0.83 %, respectively) and tumor-promotive macrophages (M2 like, 81.3% of macrophages). Furthermore, the hypoxic biochemical microenvironment is recapitulated with carbonic anhydrase 9-positive cell populations maintained during culture. Moving forward, this platform will allow for extensive characterization of tumor-stromal interactions, response to therapeutic intervention, and therapeutic resistance in a patient-specific manner.

Citation Format: Kayla F. Goliwas, Yong Wang, Joel L. Berry, Victor J. Thannickal, James M. Donahue, Jessy S. Deshane. Engineered three-dimensional lung tumor mimics maintain tissue heterogeneity allowing for investigation of tumor-stromal interactions [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr B23.

Abstract A05: Evaluation of in vitro three dimensional breast cancer surrogates using histologic morphology and non-invasive imaging to monitor growth and viability throughout culture

Introduction: Tumor dimensionality creates a dynamic three dimensional (3D) architecture that is influenced by the associated microenvironment, including stromal cells and the extracellular matrix. These paracrine interactions impact therapeutic efficacy and can alter drug response in vivo , yet most current in vitro models do not accurately recapitulate the dimensionality or the stromal microenvironment of human tumors. In vitro models that are more recapitulative of the human tumor microenvironment have broad applicability in evaluation of signaling pathways driving cancer progression, therapeutic efficacy, and mechanisms involved in therapeutic resistance and tumor recurrence. There is a great need to adapt traditional analytical methods, developed for two dimensional cell culture, for use in 3D tissue models. Herein, a novel perfusion bioreactor system is used to support the multi-week growth and development of 3D breast carcinoma tissue surrogates (measuring 1.0 cm in maximum dimension) consisting of breast carcinoma epithelial cell lines and cancer associated fibroblasts (CAF) in a supportive extracellular matrix. Further, non-invasive imaging techniques, commonly employed to evaluate in vivo animal model systems, were used to measure growth of the surrogates overtime.

Methods: 3D breast carcinoma surrogates were generated by incorporating MDA-MB-231 cells (tagged with GFP and luciferase) or MCF-7 cells (tagged with GFP and luciferase), with or without CAF, into an extracellular matrix. Surrogates were cultured in a perfusion bioreactor system for up to 3 weeks. Cell growth was measured on histologic sections of surrogates by counting the number of nucleated cells per surrogate cross-sectional area (cell density). Growth and viability were also determined in the same surrogates over time by using non-invasive fluorescence and luminescence imaging (IVIS 100 system).

Results: The use of a flow perfusion bioreactor system resulted in a marked increase in the cell density of surrogates compared to non-perfused surrogates (perfused: 93.3 nucleated cells/area vs. non-perfused: 32.1 nucleated cells/area) at 21 days culture. Fluorescence and luminescence imaging of surrogates, containing increasing concentrations of breast cancer epithelial cells, were imaged at day 0 to confirm a correlation between signal intensity and cell number using each imaging modality (GFP: R2=0.97, p<0.01, Luciferase: R2=0.99, p=0.053 ). Next, fluorescence imaging of the same 3D breast carcinoma surrogates (containing breast carcinoma cells and CAF) overtime was completed at days 0, 7, and 14 of culture and showed an increase in signal (7.9 fold higher signal at day 14 compared to day 0) indicating growth throughout culture. Similar results were seen with imaging of the luciferase signal where the signal was 28.2 fold higher at day 14 compared to day 0.

Conclusions: The presence of perfusion allows the growth and development of a recapitulative breast carcinoma surrogate with a size similar to human breast carcinomas at the time of detection and with an appropriate tumor microenvironment. Non-invasive imaging methods have successfully been adapted to evaluate growth of the breast carcinoma surrogates throughout multi-week culture.

Future Directions: The use of these perfused breast carcinoma surrogates and imaging modalities in the evaluation of established and candidate cancer therapeutics will be assessed.

Citation Format: Kayla F. Goliwas, Jillian R. Richter, Lauren E. Marshall, Joel L. Berry, Andra R. Frost. Evaluation of in vitro three dimensional breast cancer surrogates using histologic morphology and non-invasive imaging to monitor growth and viability throughout culture. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A05.

A recapitulative three-dimensional model of breast carcinoma requires perfusion for multi-week growth

Breast carcinomas are complex, three-dimensional tissues composed of cancer epithelial cells and stromal components, including fibroblasts and extracellular matrix. In vitro models that more faithfully recapitulate this dimensionality and stromal microenvironment should more accurately elucidate the processes driving carcinogenesis, tumor progression, and therapeutic response. Herein, novel in vitro breast carcinoma surrogates, distinguished by a relevant dimensionality and stromal microenvironment, are described and characterized. A perfusion bioreactor system was used to deliver medium to surrogates containing engineered microchannels and the effects of perfusion, medium composition, and the method of cell incorporation and density of initial cell seeding on the growth and morphology of surrogates were assessed. Perfused surrogates demonstrated significantly greater cell density and proliferation and were more histologically recapitulative of human breast carcinoma than surrogates maintained without perfusion. Although other parameters of the surrogate system, such as medium composition and cell seeding density, affected cell growth, perfusion was the most influential parameter.

Preparation and Analysis of In Vitro Three Dimensional Breast Carcinoma Surrogates

Three dimensional (3D) culture is a more physiologically relevant method to model cell behavior in vitro than two dimensional culture. Carcinomas, including breast carcinomas, are complex 3D tissues composed of cancer epithelial cells and stromal components, including fibroblasts and extracellular matrix (ECM). Yet most in vitro models of breast carcinoma consist only of cancer epithelial cells, omitting the stroma and, therefore, the 3D architecture of a tumor in vivo. Appropriate 3D modeling of carcinoma is important for accurate understanding of tumor biology, behavior, and response to therapy. However, the duration of culture and volume of 3D models is limited by the availability of oxygen and nutrients within the culture. Herein, we demonstrate a method in which breast carcinoma epithelial cells and stromal fibroblasts are incorporated into ECM to generate a 3D breast cancer surrogate that includes stroma and can be cultured as a solid 3D structure or by using a perfusion bioreactor system to deliver oxygen and nutrients. Following setup and an initial growth period, surrogates can be used for preclinical drug testing. Alternatively, the cellular and matrix components of the surrogate can be modified to address a variety of biological questions. After culture, surrogates are fixed and processed to paraffin, in a manner similar to the handling of clinical breast carcinoma specimens, for evaluation of parameters of interest. The evaluation of one such parameter, the density of cells present, is explained, where ImageJ and CellProfiler image analysis software systems are applied to photomicrographs of histologic sections of surrogates to quantify the number of nucleated cells per area. This can be used as an indicator of the change in cell number over time or the change in cell number resulting from varying growth conditions and treatments.

Abstract 331: A novel perfusion bioreactor system maintains long-term viability of a three dimensional in vitro breast carcinoma surrogate

Background: Breast carcinomas are complex, three-dimensional (3D) tissues composed of breast cancer epithelial cells and stromal components, including fibroblasts and extracellular matrix (ECM). Most in vitro models of carcinoma consist only of cancer epithelial cells, omitting the stroma and, therefore, the 3D architecture of a tumor in vivo. While more accurate 3D modeling allows for enhanced recapitulation of tumor biology and behavior, 3D culture is acknowledged to be challenging with cell viability decreasing dramatically overtime due to lack of available nutrients. Here-in, a novel perfusion bioreactor system supplies medium through 400 uM-diameter channels to maintain survival of a 3D breast cancer surrogate consisting of MDA-MB-231 (231) breast cancer epithelial cells, breast cancer fibroblasts (CAF) and ECM. For optimization of ECM in the breast cancer surrogates, collagen I concentration and species were varied and the effect on 3D morphology and cell viability was assessed. Methods: To assess the effect of collagen concentration on 3D morphology and cell viability, 231 cells and CAF (2:1 ratio) were incorporated into 1.9, 4, 6, or 8 mg/ml (bovine or rat tail) collagen I mixed with 10% basement membrane (BM, i.e. GFR Matrigel) and cultured for 7 days in 8-well chamber slides (non-perfused, solid 3D cultures). H&E stained histologic sections were prepared after fixation and paraffin embedding of the cultures. Cell aggregation, as a measure of 3D morphology, and viability were assessed on histologic sections by image analysis (ImageJ) and autofluorescence, respectively. To compare cell viability in solid 3D culture to surrogates in the perfusion bioreactor system, 231 cells and CAF (2:1 ratio) were incorporated into an ECM composed of 6 mg/ml bovine collagen I mixed with 10% BM and grown in solid 3D culture or in the bioreactor system. The conditions were compared at 7, 14, and 21 days. Results: Collagen I concentration and species had no significant effect on the extent of cell aggregation. However, cell viability was significantly greater in 6 and 8 mg/ml (69.6% and 67.0% alive, respectively) than 1.9 mg/ml (31.9% alive) bovine collagen (ANOVA, p≤0.05). A similar increase in viability with increasing concentration was not seen with rat-tail collagen. Therefore, 6 mg/ml bovine collagen I was used in cancer surrogates in the perfusion bioreactor system. Cell viability was increased in the perfused surrogate (87.9% alive) in comparison to solid cultures (69.6% alive, t-Test, p = 0.03) at 7 days. There was no significant decrease in viability at 14 and 21 days in perfused surrogates (93.8% and 76.7% alive, respectively). Conclusions: Bovine collagen I concentration affects viability of breast cancer cells in 3D. The perfusion bioreactor system promotes cell viability allowing for multi-week culture of breast carcinoma surrogates.

Citation Format: Kayla F. Goliwas, Lauren E. Marshall, Kun Yuan, Joel L. Berry, Andra R. Frost. A novel perfusion bioreactor system maintains long-term viability of a three dimensional in vitro breast carcinoma surrogate. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 331. doi:10.1158/1538-7445.AM2015-331

The presence of primary cilia in cancer cells does not predict responsiveness to modulation of smoothened activity

Primary cilia are microtubule-based organelles that regulate smoothened-dependent activation of the GLI transcription factors in canonical hedgehog signaling. In many cancers, primary cilia are markedly decreased or absent. The lack of primary cilia may inhibit or alter canonical hedgehog signaling and, thereby, interfere in the cellular responsiveness to modulators of smoothened activity. Clinical trials of smoothened antagonists for cancer treatment have shown the best response in basal cell carcinomas, with limited response in other solid tumors. To determine whether the presence or absence of primary cilia in cancer cells will predict their responsiveness to modulation of smoothened activity, we compared the ability of an agonist and/or inhibitor of smoothened (SAG and SANT1, respectively) to modulate GLI-mediated transcription, as measured by GLI1 mRNA level or GLI-luciferase reporter activity, in non-cancer cells with primary cilia (ovarian surface epithelial cells and breast fibroblasts), in cancer cells that cannot assemble primary cilia (MCF7, MDA-MB-231 cell lines), and in cancer cells with primary cilia (SKOV3, PANC1 cell lines). As expected, SAG and SANT1 resulted in appropriate modulation of GLI transcriptional activity in ciliated non-cancer cells, and failed to modulate GLI transcriptional activity in cancer cells without primary cilia. However, there was also no modulation of GLI transcriptional activity in either ciliated cancer cell line. SAG treatment of SKOV3 induced localization of smoothened to primary cilia, as assessed by immunofluorescence, even though there was no increase in GLI transcriptional activity, suggesting a defect in activation of SMO in the primary cilia or in steps later in the hedgehog pathway. In contrast to SKOV3, SAG treatment of PANC1 did not cause the localization of smoothened to primary cilia. Our data demonstrate that the presence of primary cilia in the cancer epithelial cells lines tested does not indicate their responsiveness to smoothened activation or inhibition.

Flow-perfusion bioreactor system for engineered breast cancer surrogates to be used in preclinical testing

There is a need for preclinical testing systems that predict the efficacy, safety and pharmacokinetics of cancer therapies better than existing in vitro and in vivo animal models. An approach to the development of predictive in vitro systems is to more closely recapitulate the cellular and spatial complexity of human cancers. One limitation of using current in vitro systems to model cancers is the lack of an appropriately large volume to accommodate the development of this complexity over time. To address this limitation, we have designed and constructed a novel flow-perfusion bioreactor system that can support large-volume, engineered tissue comprised of multicellular cancer surrogates by modifying current microfluidic devices. Key features of this technology are a three-dimensional (3D) volume (1.2 cm³ ) that has greater tissue thickness than is utilized in existing microfluidic systems and the ability to perfuse the volume, enabling the development of realistic tumour geometry. The constructs were fabricated by infiltrating porous carbon foams with an extracellular matrix (ECM) hydrogel and engineering through-microchannels. The carbon foam structurally supported the hydrogel and microchannel patency for up to 161 h. The ECM hydrogel was shown to adhere to the carbon foam and polydimethylsiloxane flow chamber, which housed the hydrogel-foam construct, when surfaces were coated with glutaraldehyde (carbon foam) and nitric acid (polydimethylsiloxane). Additionally, the viability of breast cancer cells and fibroblasts was higher in the presence of perfused microchannels in comparison to similar preparations without microchannels or perfusion. Therefore, the flow-perfusion bioreactor system supports cell viability in volume and stromal contexts that are physiologically-relevant. Copyright © 2015 John Wiley & Sons, Ltd.

Abstract 2022: Importance of ECM and media permeation in 3D modeling of breast cancer

Background: Three dimensional (3D) culture is a more physiologically relevant method to model cell behavior in vitro than two dimensional culture. 3D modeling of cancer is of particular importance in drug development where predicting in vivo effectiveness is challenging. Not only is the 3D structure important for proper modeling of cancer but the response from the surrounding microenvironment, including the extracellular matrix (ECM) and fibroblasts, is also necessary to accurately predict drug response. A major hindrance to 3D culture is loss of cell viability due to nutrient limitation. Herein, we demonstrate the ability of our novel bioreactor system to prolong viability of 3D cultures and the importance of ECM composition in breast cancer modeling. Methods: To gain further understanding of the effect of different ECM on the 3D arrangement of breast cancer cells and breast fibroblasts, three different variations of ECM were tested: 1) 100% basement membrane (BM, reduced growth factor Matrigel) diluted to 9-12 μg/ml, 2) an equal volume of BM and Collagen I (50% BM + 50% Collagen I), and 3) 10% BM in Collagen I. MDA-MB-231 (231) breast cancer cells were grown in each ECM in monoculture or co-culture with breast fibroblasts (ratio of 2:1) for 3 or 7 days. The formation of cell aggregates, as seen in most infiltrating carcinomas of the breast, was assessed by image analysis. To improve viability, 250 μM channels penetrated the 3D co-cultures (consisting of 231 cells and fibroblasts (2:1) mixed into 10% BM/Collagen I) in our perfusion bioreactor system. Proliferation, measured by Ki-67 immunostaining, was compared over time in solid co-cultures and perfused and non-perfused co-cultures after 3 or 7 days. Results: In 3D monocultures, significantly greater cell aggregation was seen with 100% BM compared to 50% and 10% BM at both 3 and 7 days (p<0.002, ANOVA). A similar result was seen in 3D co-cultures with fibroblasts (p<0.002, ANOVA). 3D cultures without channels (solid) demonstrated a reduced Ki-67 labeling index over time (65% at 1 day, 35% at 3 days, and 8.5% at 7 days). Whereas, 3D co-cultures with channels, both perfused and non-perfused, had a more constant Ki-67 labeling index over time (49.6% at 3 days and 37.3% at 7 days with perfusion and 37.4% at 3 days and 34.4% at 7 days without perfusion). Conclusions: Using 3D co-culture with fibroblasts and ECM to model breast cancer recapitulates in vivo tumor-stromal interactions in breast carcinomas better than monocultures in 2D. The formulation of ECM affected cell arrangement, with the presence of BM promoting cell aggregation. The use of our perfusion bioreactor system improved cell proliferation in comparison to solid 3D cultures, which did not sustain growth over time. We anticipate that further refinement of our 3D culture system will allow more accurate investigation of tumor-stromal interactions and drug testing in breast cancer.

Citation Format: Kayla F. Goliwas, Lauren E. Marshall, Kun Yuan, Joel Berry, Andra R. Frost. Importance of ECM and media permeation in 3D modeling of breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2022. doi:10.1158/1538-7445.AM2014-2022