In vivo lymphatic imaging of a human inflammatory breast cancer model

High-fat diet, but not duration of lactation, increases mammary gland lymphatic vessel function and subsequent growth of inflammatory breast cancer cells

Inflammatory breast cancer (IBC) presents as rapid-onset swelling and breast skin changes caused by tumor emboli in the breast and breast skin lymphatics. IBC has been linked with obesity and duration of breastfeeding, but how these factors affect IBC tumor progression is not clear. We modeled the simultaneous effects of diet and weaning in mice on in vivo lymphatic function; on IBC tumor growth; and on aspects of the mammary gland microenvironment before and after IBC (SUM149) xenograft inoculation. We hypothesized that weaning status and diet would have synergistic effects on lymphatic function and the breast microenvironment to enhance IBC tumor growth. Changes in lymphatic structure and function were characterized with in vivo near-infrared fluorescence (NIRF) imaging. Mice were fed either a high-fat diet (HFD; 60 kcal%) or a normal/low-fat diet (LFD; 10 kcal%), bred twice, and subjected to either normal-duration nursing (NW) or forced weaning (FW). SUM149 IBC tumors were implanted at 14 months; images were obtained before and after implantation. Multiparous mice fed HFD showed increased pre-tumor lymphatic pulsing in both the FW and NW groups relative to mice fed LFD. HFD promoted tumor growth independent of weaning time (P = 0.04). Pre-tumor lymphatic pulsing was associated with tumor volume at 8 weeks (P = 0.02) and was significantly correlated with expression of the lymphatic tracking ligand CCL21 (P = 0.05, Table 1). HFD significantly increased the numbers of monocyte-derived IBA1+, CD163+, and CD11c+ cells (P < 0.0001, P < 0.0001, P = 0.0005) in the contralateral, non-tumor-bearing mammary gland. Numbers of lymphangiogenic podoplanin+/IBA1+ macrophages were increased in the ducts of HFD and FW mice (all P < 0.003). HFD in nulliparous mice had a similar increase in lymphatic pulsing at 14 weeks (P = 0.006), indicating that this functional change was independent of parity. We conclude that HFD induced increases in mammary gland lymphatic function, assessed as pulsing rate before tumor initiation, and correlated with inflammation in the mammary gland and increased SUM149 tumor growth. The relationship between diet, lymphatic pulsing, and tumor growth warrants further investigation.

A Novel Preclinical Murine Model to Monitor Inflammatory Breast Cancer Tumor Growth and Lymphovascular Invasion

Inflammatory breast cancer (IBC), an understudied and lethal breast cancer, is often misdiagnosed due to its unique presentation of diffuse tumor cell clusters in the skin and dermal lymphatics. Here, we describe a window chamber technique in combination with a novel transgenic mouse model that has red fluorescent lymphatics (ProxTom RFP Nu/Nu) to simulate IBC clinicopathological hallmarks. Various breast cancer cells stably transfected to express green or red fluorescent reporters were transplanted into mice bearing dorsal skinfold window chambers. Intravital fluorescence microscopy and the in vivo imaging system (IVIS) were used to serially quantify local tumor growth, motility, length density of lymph and blood vessels, and degree of tumor cell lymphatic invasion over 0-140 h. This short-term, longitudinal imaging time frame in studying transient or dynamic events of diffuse and collectively migrating tumor cells in the local environment and quantitative analysis of the tumor area, motility, and vessel characteristics can be expanded to investigate other cancer cell types exhibiting lymphovascular invasion, a key step in metastatic dissemination. It was found that these models were able to effectively track tumor cluster migration and dissemination, which is a hallmark of IBC clinically, and was recapitulated in these mouse models.

Tumor Growth Progression in Ectopic and Orthotopic Xenografts from Inflammatory Breast Cancer Cell Lines

Xenografts can grow in immunosuppressed hosts, such as SCID mice, and tumor material can be injected into hosts either ectopically or orthotopically. Choosing the correct model to use is a crucial step in animal research. The aim of this study was to report the differences between ectopic and orthotopic xenografts in tumor progression, metastasis capacity, histological features, and steroid hormone profiles in xenografts from the cIMC (canine inflammatory mammary cancer) cell line IPC-366 and hIBC (human inflammatory breast cancer) cell line SUM149. To achieve this purpose, 40 female mice 6-8 weeks old were inoculated with IPC-366 and SUM149 cells subcutaneously (ectopic models) or into mammary fat pad (orthotopic models). Mice were monitored for tumor progression and appearance of metastases, and generated tumors were analyzed in terms of histological examination and steroid hormone production. The results revealed differences in tumor appearance and percentage of metastasis between ectopic and orthotopic models, which were higher in the ectopic xenografts from both cell lines. However, both models had similar characteristics of tumor progression, histological features, and steroid hormone secretion profiles. We show that the ectopic model can be validated as a good and useful model of tumor development in addition to, not contrary to, the orthotopic model in breast cancer research.

Inflammatory breast cancer appearance at presentation is associated with overall survival

Background

Inflammatory breast cancer (IBC) is a clinical diagnosis. Here, we examined the association of a “classic” triad of clinical signs, swollen involved breast, nipple change, and diffuse skin change, with overall survival (OS).

Method

Breast medical photographs from patients enrolled on a prospective IBC registry were scored by two independent reviewers as classic (triad above), not classic, and difficult to assign. Chi‐squared test, Fisher's exact test, and Wilcoxon rank‐sum test were used to assess differences between patient groups. Kaplan–Meier estimates and the log‐rank test and Cox proportional hazard regression were used to assess the OS.

Results

We analyzed 245 IBC patients with median age 54 (range 26–81), M0 versus M1 status (157 and 88 patients, respectively). The classic triad was significantly associated with smoking, post‐menopausal status, and metastatic disease at presentation (p = 0.002, 0.013, and 0.035, respectively). Ten‐year actuarial OS for not classic and difficult to assign were not significantly different and were grouped for further analyses. Ten‐year OS was 29.7% among patients with the classic sign triad versus 57.2% for non‐classic (p < 0.0001). The multivariate Cox regression model adjusting for clinical staging (p < 0.0001) and TNBC status (<0.0001) demonstrated classic presentation score significantly associated with poorer OS time (HR 2.6, 95% CI 1.7–3.9, p < 0.0001).

Conclusions

A triad of classic IBC signs independently predicted OS in patients diagnosed with IBC. Further work is warranted to understand the biology related to clinical signs and further extend the understanding of physical examination findings in IBC.

Fluorescent nanotechnology for in vivo imaging

Fluorescent imaging in living animals gives an intuitive picture of the dynamic processes in the complex environment within a living being. However, animal tissues present a substantial barrier and are opaque to most wavelengths of visible light. Fluorescent nanoparticles (NPs) with new photophysical characteristics have shown excellent performance for in vivo imaging. Hence, fluorescent NPs have been widely studied and applied for the detection of molecular and biological processes in living animals. In addition, developments in the area of nanotechnology have allowed materials to be used in intact animals for disease detection, diagnosis, drug delivery, and treatment. This review provides information on the different types of fluorescent particles based on nanotechnology, describing their unique individual properties and applications for detecting vital processes in vivo. The development and application of new fluorescent NPs will provide opportunities for in vivo imaging with better penetration, sensitivity, and resolution. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

Growth of tumor emboli within a vessel model reveals dependence on the magnitude of mechanical constraint

Tumor emboli-aggregates of tumor cells within vessels-pose a clinical challenge as they are associated with increased metastasis and tumor recurrence. When growing within a vessel, tumor emboli are subject to a unique mechanical constraint provided by the tubular geometry of the vessel. Current models of tumor emboli use unconstrained multicellular tumor spheroids, which neglect this mechanical interplay. Here, we modeled a lymphatic vessel as a 200 μm-diameter channel in either a stiff or soft, bioinert agarose matrix to create a vessel-like constraint model (VLCM), and we modeled colon or breast cancer tumor emboli with aggregates of HCT116 or SUM149PT cells, respectively. The stiff matrix VLCM constrained the tumor emboli to the cylindrical channel, which led to continuous growth of the emboli, in contrast to the growth rate reduction that unconstrained spheroids exhibit. Emboli morphology in the soft matrix VLCM, however, was dependent on the magnitude of mechanical mismatch between the matrix and the cell aggregates. In general, when the elastic modulus of the matrix of the VLCM was greater than the emboli (EVLCM/Eemb > 1), the emboli were constrained to grow within the channel, and when the elastic modulus of the matrix was less than the emboli (0 < EVLCM/Eemb < 1), the emboli bulged into the matrix. Due to a large difference in myosin II expression between the cell lines, we hypothesized that tumor cell aggregate stiffness is an indicator of cellular force-generating capability. Inhibitors of myosin-related force generation decreased the elastic modulus and/or increased the stress relaxation of the tumor cell aggregates, effectively increasing the mechanical mismatch. The increased mechanical mismatch after drug treatment was correlated with increased confinement of tumor emboli growth along the channel, which may translate to increased tumor burden due to the increased tumor volume within the diffusion distance of nutrients and oxygen.

The Development and Treatment of Lymphatic Dysfunction in Cancer Patients and Survivors

Breast-cancer-acquired lymphedema is routinely diagnosed from the appearance of irreversible swelling that occurs as a result of lymphatic dysfunction. Yet in head and neck cancer survivors, lymphatic dysfunction may not always result in clinically overt swelling, but instead contribute to debilitating functional outcomes. In this review, we describe how cancer metastasis, lymph node dissection, and radiation therapy alter lymphatic function, as visualized by near-infrared fluorescence lymphatic imaging. Using custom gallium arsenide (GaAs)-intensified systems capable of detecting trace amounts of indocyanine green administered repeatedly as lymphatic contrast for longitudinal clinical imaging, we show that lymphatic dysfunction occurs with cancer progression and treatment and is an early, sub-clinical indicator of cancer-acquired lymphedema. We show that early treatment of lymphedema can restore lymphatic function in breast cancer and head and neck cancer patients and survivors. The compilation of these studies provides insights to the critical role that the lymphatics and the immune system play in the etiology of lymphedema and associated co-morbidities.

Role of VEGFs/VEGFR-1 Signaling and its Inhibition in Modulating Tumor Invasion: Experimental Evidence in Different Metastatic Cancer Models

The vascular endothelial growth factor (VEGF) family members, VEGF-A, placenta growth factor (PlGF), and to a lesser extent VEGF-B, play an essential role in tumor-associated angiogenesis, tissue infiltration, and metastasis formation. Although VEGF-A can activate both VEGFR-1 and VEGFR-2 membrane receptors, PlGF and VEGF-B exclusively interact with VEGFR-1. Differently from VEGFR-2, which is involved both in physiological and pathological angiogenesis, in the adult VEGFR-1 is required only for pathological angiogenesis. Besides this role in tumor endothelium, ligand-mediated stimulation of VEGFR-1 expressed in tumor cells may directly induce cell chemotaxis and extracellular matrix invasion. Furthermore, VEGFR-1 activation in myeloid progenitors and tumor-associated macrophages favors cancer immune escape through the release of immunosuppressive cytokines. These properties have prompted a number of preclinical and clinical studies to analyze VEGFR-1 involvement in the metastatic process. The aim of the present review is to highlight the contribution of VEGFs/VEGFR-1 signaling in the progression of different tumor types and to provide an overview of the therapeutic approaches targeting VEGFR-1 currently under investigation.

Near-Infrared Fluorescent Proteins and Their Applications

High transparency, low light-scattering, and low autofluorescence of mammalian tissues in the near-infrared (NIR) spectral range (~650-900 nm) open a possibility for in vivo imaging of biological processes at the micro- and macroscales to address basic and applied problems in biology and biomedicine. Recently, probes that absorb and fluoresce in the NIR optical range have been engineered using bacterial phytochromes - natural NIR light-absorbing photoreceptors that regulate metabolism in bacteria. Since the chromophore in all these proteins is biliverdin, a natural product of heme catabolism in mammalian cells, they can be used as genetically encoded fluorescent probes, similarly to GFP-like fluorescent proteins. In this review, we discuss photophysical and biochemical properties of NIR fluorescent proteins, reporters, and biosensors and analyze their characteristics required for expression of these molecules in mammalian cells. Structural features and molecular engineering of NIR fluorescent probes are discussed. Applications of NIR fluorescent proteins and biosensors for studies of molecular processes in cells, as well as for tissue and organ visualization in whole-body imaging in vivo, are described. We specifically focus on the use of NIR fluorescent probes in advanced imaging technologies that combine fluorescence and bioluminescence methods with photoacoustic tomography.

Stromal cells in breast cancer as a potential therapeutic target

Breast cancer in the United States is the second most commonly diagnosed cancer in women. About 1 in 8 women will develop invasive breast cancer over the course of her lifetime and breast cancer remains the second leading cause of cancer-related death. In pursuit of novel therapeutic strategies, researchers have examined the tumor microenvironment as a potential anti-cancer target. In addition to neoplastic cells, the tumor microenvironment is composed of several critical normal cell types, including fibroblasts, vascular and lymph endothelial cells, osteoclasts, adipocytes, and immune cells. These cells have important roles in healthy tissue stasis, which frequently are altered in tumors. Indeed, tumor-associated stromal cells often contribute to tumorigenesis, tumor progression, and metastasis. Consequently, these host cells may serve as a possible target in anti-tumor and anti-metastatic therapeutic strategies. Targeting the tumor associated host cells offers the benefit that such cells do not mutate and develop resistance in response to treatment, a major cause of failure in cancer therapeutics targeting neoplastic cells. This review discusses the role of host cells in the tumor microenvironment during tumorigenesis, progression, and metastasis, and provides an overview of recent developments in targeting these cell populations to enhance cancer therapy efficacy.

PDE5 inhibition eliminates cancer stem cells via induction of PKA signaling

Cancer stem cells (CSCs) are involved in metastasis and resistance development, thus affecting anticancer therapy efficacy. The underlying pathways required for CSC maintenance and survival are not fully understood and only a limited number of treatment strategies to specifically target CSCs have been identified. To identify novel CSC targeting compounds, we here set-up an aldehyde dehydrogenase (ALDH)-based phenotypic screening system that allows for an automated and standardized identification of CSCs. By staining cancer cells for ALDH activity and applying high-content-based single-cell population analysis, the proportion of a potential CSC subpopulation with significantly higher ALDH activity (ALDH_high) can be quantified in a heterogeneous cell population. We confirmed high ALDH activity as surrogate marker for the CSC subpopulation in vitro and validated Wnt signaling as an essential factor for the maintenance of CSCs in SUM149 breast cancer cells. In a small molecule screen, we identified phosphodiesterase type 5 (PDE5) inhibition as potential strategy to target CSC maintenance and survival in multiple cancer cell lines. CSC elimination by PDE5 inhibition was not dependent on PKG signaling, and we suggest a novel mechanism in which PDE5 inhibition leads to elevated cGMP levels that stimulate cAMP/PKA signaling to eliminate CSCs.

Bacterial Phytochromes, Cyanobacteriochromes and Allophycocyanins as a Source of Near-Infrared Fluorescent Probes

Bacterial photoreceptors absorb light energy and transform it into intracellular signals that regulate metabolism. Bacterial phytochrome photoreceptors (BphPs), some cyanobacteriochromes (CBCRs) and allophycocyanins (APCs) possess the near-infrared (NIR) absorbance spectra that make them promising molecular templates to design NIR fluorescent proteins (FPs) and biosensors for studies in mammalian cells and whole animals. Here, we review structures, photochemical properties and molecular functions of several families of bacterial photoreceptors. We next analyze molecular evolution approaches to develop NIR FPs and biosensors. We then discuss phenotypes of current BphP-based NIR FPs and compare them with FPs derived from CBCRs and APCs. Lastly, we overview imaging applications of NIR FPs in live cells and in vivo. Our review provides guidelines for selection of existing NIR FPs, as well as engineering approaches to develop NIR FPs from the novel natural templates such as CBCRs.

New concept for the prevention and treatment of metastatic lymph nodes using chemotherapy administered via the lymphatic network

Intravenous chemotherapy has poor access to metastatic lymph nodes (LNs) and is limited by short-lived drug concentrations. Here, we describe the administration of chemotherapy via the lymphatic network as a new concept for the prevention and treatment of metastatic LNs. A metastatic LN can be treated by the injection of drugs into an upstream LN, either the sentinel LN (SLN) or another upstream LN. In a mouse model, tumor cells were inoculated into the subiliac LN (SiLN) to induce metastasis to the proper axillary LN (PALN). Two routes were used for drug delivery to the PALN, namely from the SiLN and from the accessory axillary LN (AALN). We found that tumor masses were formed in lymphatic vessels between the SiLN and PALN. The flow of fluorescent solution injected into the SiLN towards the PALN decreased with tumor mass formation. Delivery from the AALN (free of metastatic tumor cells) to the PALN was identified as an alternative route. Intranodal injection can deliver high concentrations of drugs to secondary metastatic LNs. The study advocates a new concept for the prevention and treatment of metastatic lymph nodes whereby drugs injected into upstream lymph nodes can reach metastatic lymph nodes via the lymphatic network.

Longitudinal far red gene-reporter imaging of cancer metastasis in preclinical models: a tool for accelerating drug discovery

In this short communication, we demonstrate for the first time, the use of far red fluorescent gene reporter, iRFP to longitudinally and non-invasively track the in vivo process of lymphatic metastases from an orthotopic site of mammary implantation through lymphatic vessels and to draining lymph nodes. Potentially useful to accelerate cancer drug discovery as an in vivo screening tool to monitor the pharmacological arrest of metastasis, we show that the custom as well as commercial small animal imaging devices have adequate performance to detect the gene reporter in stably expressing metastatic cancer cells.

Primary breast cancer induces pulmonary vascular hyperpermeability and promotes metastasis via the VEGF-PKC pathway

The lung is one of the most frequent target organs for breast cancer metastasis. When breast cancer cells from a primary tumor do not colonize the lung, which we named the premetastatic phase, the microenvironment of the lung has already been influenced by the primary tumor. However, little is known about the exact premetastatic alteration and regulatory mechanisms of the lung. Here, we used 4T1 cells (a mouse breast cancer cell line which can specifically metastasize to the lung) to build a mouse breast cancer model. We found that primary breast tumor induced increased pulmonary vascular permeability in the premetastatic phase, which facilitated the leakage of rhodamine-dextran and the extravasation of intravenous therapy injected cancer cells. Furthermore, tight junctions (TJs) were disrupted, and the expression of zonula occludens-1(ZO-1), one of the most important components of tight junctions, was decreased in the premetastatic lung. In addition, elevated serum vascular endothelial growth factor (VEGF) was involved in the destabilization of tight junctions and the VEGF antagonist bevacizumab reversed the primary tumor-induced vascular hyperpermeability. Moreover, activation of the protein kinase C (PKC) pathway disrupted the integrity of TJs and accordingly, the disruption could be alleviated by blocking VEGF. Taken together, these data demonstrate that primary breast cancer may induce tight junction disruptions in the premetastatic lung via the VEGF-PKC pathway and promote pulmonary vascular hyperpermeability before metastasis. © 2015 Wiley Periodicals, Inc.

Near-infrared fluorescent proteins engineered from bacterial phytochromes

Near-infrared fluorescent proteins (NIR FPs), photoactivatable NIR FPs and NIR reporters of protein-protein interactions developed from bacterial phytochrome photoreceptors (BphPs) have advanced non-invasive deep-tissue imaging. Here we provide a brief guide to the BphP-derived NIR probes with an emphasis on their in vivo applications. We describe phenotypes of NIR FPs and their photochemical and intracellular properties. We discuss NIR FP applications for imaging of various cell types, tissues and animal models in basic and translational research. In this discussion, we focus on NIR FPs that efficiently incorporate endogenous biliverdin chromophore and therefore can be used as straightforward as GFP-like proteins. We also overview a usage of NIR FPs in different imaging platforms, from planar epifluorescence to tomographic and photoacoustic technologies.