Transcriptome-wide In Vitro Effects of Aspirin on Patient-derived Normal Colon Organoids

Mechanisms underlying aspirin chemoprevention of colorectal cancer remain unclear. Prior studies have been limited because of the inability of preclinical models to recapitulate human normal colon epithelium or cellular heterogeneity present in mucosal biopsies. To overcome some of these obstacles, we performed in vitro aspirin treatment of colon organoids derived from normal mucosal biopsies to reveal transcriptional networks relevant to aspirin chemoprevention. Colon organoids derived from 38 healthy individuals undergoing endoscopy were treated with 50 μmol/L aspirin or vehicle control for 72 hours and subjected to bulk RNA sequencing. Paired regression analysis using DESeq2 identified differentially expressed genes (DEG) associated with aspirin treatment. Cellular composition was determined using CIBERSORTx. Aspirin treatment was associated with 1,154 significant (q < 0.10) DEGs prior to deconvolution. We provide replication of these findings in an independent population-based RNA-sequencing dataset of mucosal biopsies (BarcUVa-Seq), where a significant enrichment for overlap of DEGs was observed (P < 2.2E-16). Single-cell deconvolution revealed changes in cell composition, including a decrease in transit-amplifying cells following aspirin treatment (P = 0.01). Following deconvolution, DEGs included novel putative targets for aspirin such as TRABD2A (q = 0.055), a negative regulator of Wnt signaling. Weighted gene co-expression network analysis identified 12 significant modules, including two that contained hubs for EGFR and PTGES2, the latter being previously implicated in aspirin chemoprevention. In summary, aspirin treatment of patient-derived colon organoids using physiologically relevant doses resulted in transcriptome-wide changes that reveal altered cell composition and improved understanding of transcriptional pathways, providing novel insight into its chemopreventive properties. PREVENTION RELEVANCE: Numerous studies have highlighted a role for aspirin in colorectal cancer chemoprevention, though the mechanisms driving this association remain unclear. We addressed this by showing that aspirin treatment of normal colon organoids diminished the transit-amplifying cell population, inhibited prostaglandin synthesis, and dysregulated expression of novel genes implicated in colon tumorigenesis.

Serum HMGB1 associates with liver disease and predicts readmission and mortality in patients with alcohol use disorder

Identifying the minority of patients with alcohol use disorder (AUD) who develop the wide spectrum of alcohol-associated liver disease (ALD), and risk-stratifying these patients, is of critical importance. High-Mobility Group Box 1 protein (HMGB1) is an alarmin that has been implicated in the pathogenesis of multiple liver diseases. Its use as a biomarker for liver disease in those with AUD has not been studied. In this report, we investigated the association between serum HMGB1 and the presence, severity, and progression of ALD in two well-characterized cohorts of patients with AUD. In our discovery cohort of 80 patients, we found that patients with AUD and ALD exhibited higher serum HMGB1 levels compared to patients with AUD only (p = 0.0002). Additionally, serum HMGB1 levels were positively associated with liver disease severity (p < 0.0001). We found that index serum HMGB1 levels were associated with liver disease progression, defined by an increase in MELD score at 120 days (p = 0.0397). Serum HMGB1 was notable for its diagnostic and prognostic ability; it proved able to distinguish accurately between severe and non-severe forms of ALD in both our discovery cohort (AUC = 0.8199, p = 0.0003) and an independent validation cohort of 74 patients with AUD (AUC = 0.8818, p < 0.0001). Moreover, serum HMGB1 levels effectively predicted both liver-related readmission (AUC = 0.8849, p < 0.0001) and transplantation/death (AUC = 0.8614, p = 0.0002) at 90 days. The predictive potential of HMGB1 was also validated in an independent cohort of patients with AUD. Taken together, our results suggest that serum HMGB1 shows promise as a biologically relevant biomarker for ALD in patients with AUD.

Abstract 3022: Lymph node metastasis in solid tumors: A marker or driver of disease progression

Background: The presence of lymph node metastasis in patients with solid tumors is associated with tumor aggressiveness, poorer prognosis and the recommendation for systemic therapy. However, whether tumor cells exit the lymph node and contribute to distant metastases remains controversial. Methods: In this study, we used syngeneic murine cell lines representing breast and melanoma cancer that spontaneously metastasize to the lymph node. We engineered these cells to express Dendra2, a photoconvertable protein. Dendra2 is a green-fluorescent protein that can be converted to emit red light by exposure to 405nm light. Once tumor cells spontaneously metastasized to the lymph node from the primary site, a 405nm laser diode was used on 5 consecutive days to convert Dendra2-cancer cells from green to red fluorescence, restricting the light exposure only to the metastatic lymph node. This technology allowed us to specifically trace the fate of cancer cells in the lymph node and beyond to other organs. Results: We show that spontaneous lymph node metastasis from breast cancer and melanoma mouse models can leave the lymph node and enter the blood circulation. We identified micrometastatic disease in the lung that originated from the lymph node in both models. We hypothesized that cancer cells escape the lymph node by directly invading lymph node blood vessels, as opposed to draining through the efferent lymphatic vessel. Immunohistochemical analysis of metastatic lymph nodes revealed isolated cancer cells in close association with CD31+ blood vessels, within high endothelial venules (HEVs) and breaching the vascular basement membrane. Quantitative analysis showed that 23±2% of isolated cancer cells were within 5μm of a blood vessel, compared to only 11±1% using a predictive model of randomly distributed cells in the lymph node (p&lt;0.05). Further, 6±2% of the cancer cells were inside blood vessels defined as cells within the lumen of blood vessels and having cell centroids more than 3μm from the blood vessel endothelium. To further confirm that metastatic cancer cells in a lymph node have affinity for lymph node blood vessels, we used multiphoton intravital microscopy to measure cancer cell migration in an optical lymph node window in mice. Dendra2 expressing metastatic cancer cells are first seen in the subcapsular sinus of the lymph node and later invade the cortex of the lymph node where they accumulate around rhodamine-dextran labeled blood vessels. Cancer cells can be observed in directed migration toward blood vessels as well as moving inside blood vessels. Finally, we analyzed lymph nodes with metastatic lesions from patients with head and neck cancer and identified cancer cells that were closely associated with and inside blood vessels. Conclusions: Together, our data show for the first time that in spontaneous breast and melanoma mouse models, tumor cells in the lymph node can invade blood vessels, exit the node and colonize the lung.

Citation Format: Ethel R. Pereira, Dmitriy Kedrin, Giorgio Seano, Olivia Gautier, Eelco F. Meijer, Dennis Jones, Shan-Min Chin, Shuji Kitahara, Echoe M. Bouta, Jonathan Chang, Elizabeth Beech, Han-Sin Jeong, Michael C. Carroll, Alphonse G. Taghian, Timothy P. Padera. Lymph node metastasis in solid tumors: A marker or driver of disease progression [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 3022.

Abstract B38: In vivo genome editing and organoid transplantation models of colorectal cancer and metastasis

In vivo interrogation of the function of genes implicated in tumorigenesis is limited by the need to generate and cross germline mutant mice. Here we describe approaches to model colorectal cancer (CRC) and metastasis that rely on in situ gene editing and orthotopic organoid transplantation in mice without cancer-predisposing mutations. Autochthonous tumor formation is induced by CRISPR/Cas9-based editing of the Apc and Trp53 tumor suppressor genes in colon epithelial cells and by orthotopic transplantation of Apc-edited colon organoids. ApcΔ/Δ;KrasG12D/+;Trp53Δ/Δ (AKP) mouse colon organoids and human CRC organoids engraft in the distal colon and metastasize to the liver. Finally, we apply the orthotopic transplantation model to characterize the clonal dynamics of Lgr5+ stem cells and demonstrate sequential activation of an oncogene in established colon adenomas. These experimental systems enable rapid in vivo characterization of cancer-associated genes and reproduce the entire spectrum of tumor progression and metastasis.

Citation Format: Jatin Roper, Tuomas Tammela, Naniye Malli Cetinbas, Adam Akkad, Ali Roghanian, Steffen Rickelt, Mohammad Almeqdadi, Katherine Wu, Matthias Oberli, Francisco Sánchez-Rivera, Yoona Park, Xu Liang, George Eng, Martin S. Taylor, Roxana Azimi, Dmitriy Kedrin, Rachit Neupane, Semir Beyaz, Ewa T. Sicinska, Yvelisse Suarez, James Yoo, Lillian Chen, Lawrence Zukerberg, Pekka Katajisto, Vikram Deshpande, Adam Bass, Philip N. Tsichlis, Jacqueline Lees, Robert Langer, Richard O. Hynes, Jianzhu Chen, Arjun J. Bhutkar, Tyler Jacks, Ömer H. Yilmaz. In vivo genome editing and organoid transplantation models of colorectal cancer and metastasis [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr B38.

Lymph node metastases can invade local blood vessels, exit the node, and colonize distant organs in mice

Lymph node metastases in cancer patients are associated with tumor aggressiveness, poorer prognoses, and the recommendation for systemic therapy. Whether cancer cells in lymph nodes can seed distant metastases has been a subject of considerable debate. We studied mice implanted with cancer cells (mammary carcinoma, squamous cell carcinoma, or melanoma) expressing the photoconvertible protein Dendra2. This technology allowed us to selectively photoconvert metastatic cells in the lymph node and trace their fate. We found that a fraction of these cells invaded lymph node blood vessels, entered the blood circulation, and colonized the lung. Thus, in mouse models, lymph node metastases can be a source of cancer cells for distant metastases. Whether this mode of dissemination occurs in cancer patients remains to be determined.

Anti-VEGF therapy induces ECM remodeling and mechanical barriers to therapy in colorectal cancer liver metastases

The survival benefit of anti-vascular endothelial growth factor (VEGF) therapy in metastatic colorectal cancer (mCRC) patients is limited to a few months because of acquired resistance. We show that anti-VEGF therapy induced remodeling of the extracellular matrix with subsequent alteration of the physical properties of colorectal liver metastases. Preoperative treatment with bevacizumab in patients with colorectal liver metastases increased hyaluronic acid (HA) deposition within the tumors. Moreover, in two syngeneic mouse models of CRC metastasis in the liver, we show that anti-VEGF therapy markedly increased the expression of HA and sulfated glycosaminoglycans (sGAGs), without significantly changing collagen deposition. The density of these matrix components correlated with increased tumor stiffness after anti-VEGF therapy. Treatment-induced tumor hypoxia appeared to be the driving force for the remodeling of the extracellular matrix. In preclinical models, we show that enzymatic depletion of HA partially rescued the compromised perfusion in liver mCRCs after anti-VEGF therapy and prolonged survival in combination with anti-VEGF therapy and chemotherapy. These findings suggest that extracellular matrix components such as HA could be a potential therapeutic target for reducing physical barriers to systemic treatments in patients with mCRC who receive anti-VEGF therapy.

In vivo genome editing and organoid transplantation models of colorectal cancer and metastasis

In vivo interrogation of the function of genes implicated in tumorigenesis is limited by the need to generate and cross germline mutant mice. Here we describe approaches to model colorectal cancer (CRC) and metastasis, which rely on in situ gene editing and orthotopic organoid transplantation in mice without cancer-predisposing mutations. Autochthonous tumor formation is induced by CRISPR-Cas9-based editing of the Apc and Trp53 tumor suppressor genes in colon epithelial cells and by orthotopic transplantation of Apc-edited colon organoids. ApcΔ/Δ;Kras^G12D/+;Trp53Δ/Δ (AKP) mouse colon organoids and human CRC organoids engraft in the distal colon and metastasize to the liver. Finally, we apply the orthotopic transplantation model to characterize the clonal dynamics of Lgr5⁺ stem cells and demonstrate sequential activation of an oncogene in established colon adenomas. These experimental systems enable rapid in vivo characterization of cancer-associated genes and reproduce the entire spectrum of tumor progression and metastasis.

Bariatric Surgery Prior to Index Screening Colonoscopy Is Associated With a Decreased Rate of Colorectal Adenomas in Obese Individuals

Objectives:

Obesity is an important risk factor for the development of colorectal cancer (CRC). Although the impact of bariatric surgery on CRC is conflicting, its impact on precursor lesions is unknown. The aim of this study was to determine whether bariatric surgery before index screening colonoscopy is associated with decreased development of colorectal adenomas.

Methods:

We performed a retrospective cohort study of bariatric surgery patients who had undergone index, screening colonoscopy at an academic center from 2001 to 2014. Patients who had bariatric surgery at least 1 year before index colonoscopy were compared with those who had surgery after colonoscopy, using multivariable logistic regression to control for presurgical body mass index, sex, gender, race, type of surgery, aspirin use, metformin use, smoking, and age at colonoscopy.

Results:

One hundred and twenty-five obese individuals who had bariatric surgery before colonoscopy were compared with 223 individuals who had colonoscopy after surgery. Adenomatous polyps were found in 16.8% of individuals who had surgery first vs. 35.5% who had colonoscopy before bariatric surgery (unadjusted odds ratio (OR) 0.37, 95% confidence interval (CI): 0.21–0.64, P=0.0003). After multivariable adjustment, bariatric surgery before index screening colonoscopy was associated with a decreased risk of adenomas at index colonoscopy (adjusted OR 0.37, 95% CI: 0.19–0.69, P=0.002).

Conclusions:

Bariatric surgery is associated with a decreased risk of colorectal adenomas in obese individuals without a family history of CRC.

ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED): a study protocol for a randomized controlled trial

BACKGROUND

Although aspirin is recommended for the prevention of colorectal cancer, the specific individuals for whom the benefits outweigh the risks are not clearly defined. Moreover, the precise mechanisms by which aspirin reduces the risk of cancer are unclear. We recently launched the ASPirin Intervention for the REDuction of colorectal cancer risk (ASPIRED) trial to address these uncertainties.

METHODS/DESIGN

ASPIRED is a prospective, double-blind, multidose, placebo-controlled, biomarker clinical trial of aspirin use in individuals previously diagnosed with colorectal adenoma. Individuals (n = 180) will be randomized in a 1:1:1 ratio to low-dose (81 mg/day) or standard-dose (325 mg/day) aspirin or placebo. At two study visits, participants will provide lifestyle, dietary and biometric data in addition to urine, saliva and blood specimens. Stool, grossly normal colorectal mucosal biopsies and cytology brushings will be collected during a flexible sigmoidoscopy without bowel preparation. The study will examine the effect of aspirin on urinary prostaglandin metabolites (PGE-M; primary endpoint), plasma inflammatory markers (macrophage inhibitory cytokine-1 (MIC-1)), colonic expression of transcription factor binding (transcription factor 7-like 2 (TCF7L2)), colonocyte gene expression, including hydroxyprostaglandin dehydrogenase 15-(NAD) (HPGD) and those that encode Wnt signaling proteins, colonic cellular nanocytology and oral and gut microbial composition and function.

DISCUSSION

Aspirin may prevent colorectal cancer through multiple, interrelated mechanisms. The ASPIRED trial will scrutinize these pathways and investigate putative mechanistically based risk-stratification biomarkers.

TRIAL REGISTRATION

This protocol is registered with the U.S. National Institutes of Health trial registry, ClinicalTrials.gov, under the identifier NCT02394769 . Registered on 16 March 2015.

Abstract PR06: VEGF-targeted therapy induces extracellular matrix remodeling and increases mechanical barriers to therapy in colorectal cancer liver metastases

Introduction: The anti-VEGF antibody bevacizumab in combination with chemotherapy is a standard treatment for metastatic colorectal cancer (mCRC) today, based on an overall survival improvement. However, this survival benefit is modest and mCRC ultimately progresses. The underlying mechanism of resistance to anti-angiogenic therapy remains unclear. Recent preclinical studies have shown that anti-angiogenic therapy increases collagen expression in tumors as a consequence of hypoxia. The extracellular matrix (ECM) play an important role in solid stress-induced blood vessel collapse as they transmit the mechanical stress created by proliferating cells within the confined space of a tumor. In this study, we investigated the effects of anti-angiogenic therapy on extracellular matrix expression, both collagenous and non-collagenous and perfusion as a novel mechanism of acquired resistance to anti-angiogenic therapy in liver metastases from CRC.

Experimental Design: We used C57BL/6 and BALB/c, as well as CCR2-/- and ATR1-/- mice for this study. To generate liver metastasis, we exteriorized and transected spleen, inject syngenic CRC SL4 or CT26 cells (0.1 million cells) in one hemispleen and then, removed it. The other hemispleen remained intact. We monitored tumor burden by measuring blood Gaussia luciferase (Gluc) activity from Gluc transduced tumors and/or by high-frequency ultrasound imaging. Treatments include anti-VEGF monoclonal antibody B20.4-1.1 (5 mg/kg or 1 mg/kg i.p. 2x/week, Genentech), an anti-Ly6G antibody (5 mg/kg i.p. every 2days), pegylated hyaluronidase (PEGHAse, 4.5 mg/kg i.v. 2x/week 24 hour prior to administration of chemotherapy), 5-Fluorouracil (50 mg/kg i.v. 2x/week). We determined ECM–hyaluronic acid (HA), sulfated glycosaminoglycan (sGAG), and collagen contents—by ELISA, the Blyscan Proteoglycan and Glycosaminoglycan assay, and hydroxyproline assay, respectively. We further determined ECM, activated fibroblasts, vasculature, perfusion (Hechst33342), and hypoxia (pimonidazole) by immunohistochemistry, and immune cell profile using flow cytometry. We then, determined stiffness (Young's modulus) of tumors by unconfined compression tests (Cancer Res 60: 2497-503, 2000) and solid stress using a recently established method (PNAS 109: 15101-8, 2012).

We obtained patient samples from the Heidelberg University Hospital and analyzed surgical specimens of patients who underwent liver resection for colorectal liver metastases without preoperative chemotherapy, after preoperative chemotherapy without bevacizumab or after preoperative chemotherapy with bevacizumab.

Results: Here, we show that anti-VEGF therapy induces remodeling of the extracellular matrix with subsequent alteration of physical properties of liver metastases. We find that preoperative treatment with bevacizumab in patients with colorectal liver metastases resulted in a significant increase in HA deposition within the tumor. Moreover, in two syngeneic mouse models of mCRC, we show that anti-VEGF therapy markedly increased expression of HA and sGAG, without significant changes in collagen deposition. The density of these matrix components correlates with tumor stiffness; the latter was also significantly increased after anti-VEGF therapy. In time-course and immunofluorescence studies, treatment-induced hypoxia appeared as the driving force for enhanced extracellular matrix expression. Enzymatic depletion of HA partially reversed compromised perfusion in liver metastases after anti-VEGF therapy and prolonged survival in combination with anti-VEGF therapy and systemic chemotherapy.

Conclusion: These findings suggest that extracellular matrix components such as HA could be a potential therapeutic target for reducing physical barriers to systemic treatments in patients with mCRC who receive anti-VEGF therapy.

This abstract is also being presented as Poster B27.

Citation Format: Nuh N. Rahbari, Dmitriy Kedrin, Joao Incio, Hao Liu, William T. Ho, Hadi T. Nia, Christina M. Edrich, Keehoon Jung, Julien Daubriac, Ivy Chen, Takahiro Heishi, John Martin, Yuhui Huang, Nir Maimon, Christoph Reissfelder, Juergen Weitz, Yves Boucher, Jeffrey W. Clark, Alan J. Grodzinsky, Dan G. Duda, Rakesh K. Jain, Dai Fukumura. VEGF-targeted therapy induces extracellular matrix remodeling and increases mechanical barriers to therapy in colorectal cancer liver metastases. [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 PR06.

Abstract P3-01-22: Sentinel lymph node metastases in breast cancer: A contributor to distant metastases?

Breast cancer metastasis remains a major cause of mortality in patients. Although significant progress has been made in understanding the mechanisms of this complex process, the findings have yet to be translated into improved survival rates in patients with metastatic disease. The presence of lymph node metastasis in most breast cancer patients is associated with tumor aggressiveness, poorer prognosis and often results in the need for systemic therapy. However, whether tumor cells in the lymph node exit and contribute to distant metastases remains controversial. To track the fate of tumor cells that metastasized to the lymph node, we engineered breast tumor cell lines to express Dendra2, a photo-convertible protein that fluoresces green in the native state and on light activation converts to red fluorescence. Using a novel chronic lymph node window that allows time-lapse imaging over a period of 10 days, we were able to track the movement of cancer cells in the dynamic microenvironment using high- resolution multi-photon microscopy. Our studies show that tumor cells entering the lymph node through the afferent lymphatic vessel proliferate in the sub-capsular sinus and later begin to invade the lymph node parenchyma. Importantly, by photo-conversion of tumor cells in the lymph node, we are able to track the tumor cells that escaped the lymph node and entered the blood circulation. The circulating tumor cells that transited through the lymph node were viable and proliferated in vitro. Our data indicate that metastatic breast cancer cells can exit the node and potentially colonize distant organs.

Citation Format: Pereira ER, Kedrin D, Jones D, Beech E, Taghian A, Padera TP. Sentinel lymph node metastases in breast cancer: A contributor to distant metastases?. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-01-22.

Prediagnostic Plasma Adiponectin and Survival among Patients with Colorectal Cancer

Circulating adiponectin is inversely related to the risk of colorectal cancer. However, its influence on colorectal cancer survival is unclear. We conducted a prospective study to evaluate the association between prediagnostic plasma levels of adiponectin and mortality in patients with colorectal cancer. We identified 621 incident colorectal cancer cases who provided blood specimens prior to diagnosis within the Nurses' Health Study (NHS) and Health Professionals Follow-up Study (HPFS). Cox proportional hazards models were used to calculate HRs and 95% confidence intervals (CI). After a median follow-up of 9 years, there were 269 (43%) total deaths, of which 181 (67%) were due to colorectal cancer. Compared with participants in the lowest quartile of adiponectin, those in the highest quartile had multivariate HRs of 1.89 (95% CI, 1.21-2.97; P(trend) = 0.01) for colorectal cancer-specific mortality and 1.66 (95% CI, 1.15-2.39; P(trend) = 0.009) for overall mortality. The apparent increased risk in colorectal cancer-specific mortality was more pronounced in patients with metastatic disease (HR, 3.02: 95% CI, 1.50-6.08). Among patients with colorectal cancer, prediagnostic plasma adiponectin is associated with an increased risk of colorectal cancer-specific and overall mortality and is more apparent in patients with metastatic disease. Adiponectin may be a marker for cancers which develop through specific pathways that may be associated with worsened prognosis. Further studies are needed to validate these findings.

Colorectal cancer models for novel drug discovery

INTRODUCTION

Despite increased screening rates and advances in targeted therapy, colorectal cancer (CRC) remains the third leading cause of cancer-related mortality. CRC models that recapitulate key features of human disease are essential to the development of novel and effective therapeutics. Classic methods of modeling CRC such as human cell lines and xenograft mice, while useful for many applications, carry significant limitations. Recently developed in vitro and in vivo models overcome some of these deficiencies and thus can be utilized to better model CRC for mechanistic and translational research.

AREAS COVERED

The authors review established models of in vitro cell culture and describe advances in organoid culture for studying normal and malignant intestine. They also discuss key features of classic xenograft models and describe other approaches for in vivo CRC research, including patient-derived xenograft, carcinogen-induced, orthotopic transplantation and transgenic mouse models. We also describe mouse models of metastatic CRC.

EXPERT OPINION

No single model is optimal for drug discovery in CRC. Genetically engineered models overcome many limitations of xenograft models. Three-dimensional organoids can be efficiently derived from both normal and malignant tissue for large-scale in vitro and in vivo (transplantation) studies and are thus a significant advance in CRC drug discovery.

Prediagnostic plasma adiponectin and survival among patients with colorectal cancer

526

Background: Adiponectin is a hormone secreted by adipose tissue and has been demonstrated to possess anticarcinogenic, anti-inflammatory and insulin-sensitizing effects. Circulating adiponectin has been shown to be inversely associated with the risk of colorectal cancer (CRC) in prospective studies. However, the association of prediagnostic adiponectin with survival among patients with established colorectal cancer is unclear. Methods: We conducted a prospective study of 621 incident colorectal cancer cases from the Nurses’ Health Study and Health Professionals Follow-up Study to evaluate the association between prediagnostic plasma adiponectin and mortality. Plasma adiponectin levels were determined by enzyme-linked immunosorbent assay from ALPCO Diagnostics. The interbatch coefficient of variation from quality control samples randomly interspersed among the case samples was 8.6%. We examined the associations between quartiles of plasma adiponectin and mortality using a Cox proportional hazards model adjusted for established and putative risk factors. All statistical tests were two sided. Results: After a median follow-up of 9 years, there were 267 (43%) total deaths and 130 (21%) CRC deaths in the total study cohort. Compared with patients in the lowest quartile of adiponectin, patients in the highest quartile had a multivariate hazard ratio (HR) for CRC-specific mortality of 2.70 [95% confidence interval (CI), 1.54-4.75; Ptrend = 0.001]. The corresponding multivariate HR for overall mortality was 1.64 (95% CI, 1.14-2.36; Ptrend = 0.007). These associations were reasonably consistent in analyses according to subgroups defined by age, gender, body mass index, stage, grade and site of primary cancer. Similar results were yielded after excluding patients diagnosed within 4 years of blood collection (Ptrend = 0.027). Conclusions: Prediagnostic adiponectin is associated with an increased risk of colorectal cancer- specific and overall mortality. Further studies are needed to elucidate the mechanistic basis for these findings and determine the potential role of adiponectin as a prognostic marker in colorectal cancer.

The adherens junction protein afadin is an AKT substrate that regulates breast cancer cell migration

The PI3K-AKT signaling pathway regulates all phenotypes that contribute to progression of human cancers, including breast cancer. AKT mediates signal relay by phosphorylating numerous substrates, which are causally implicated in biologic responses such as cell growth, survival, metabolic reprogramming, migration, and invasion. Here a new AKT substrate is identified, the adherens junction protein Afadin, which is phosphorylated by AKT at Ser1718. Importantly, under conditions of physiologic IGF-1 signaling and oncogenic PI3K and AKT, Afadin is phosphorylated by all AKT isoforms, and this phosphorylation elicits a relocalization of Afadin from adherens junctions to the nucleus. Also, phosphorylation of Afadin increased breast cancer cell migration that was dependent on Ser1718 phosphorylation. Finally, nuclear localization of Afadin was observed in clinical breast cancer specimens, indicating that regulation of Afadin by the PI3K-AKT pathway has pathophysiologic significance.

IMPLICATIONS

Phosphorylation of the adhesion protein Afadin by AKT downstream of the PI3K pathway, leads to redistribution of Afadin and controls cancer cell migration.

Imaging tumor cell movement in vivo

This unit describes the methods that we have been developing for analyzing tumor cell motility in mouse and rat models of breast cancer metastasis. Rodents are commonly used both to provide a mammalian system for studying human tumor cells (as xenografts in immunocompromised mice) as well as for following the development of tumors from a specific tissue type in transgenic lines. The Basic Protocol in this unit describes the standard methods used for generation of mammary tumors and imaging them. Additional protocols for labeling macrophages, blood vessel imaging, and image analysis are also included.

The use of fluorescent proteins for intravital imaging of cancer cell invasion

The analysis of cancer cell behavior in the primary tumor in living animals provides an opportunity to explore the process of invasion and intravasation in the complex microenvironment that is present in vivo. In this chapter, we describe the methods that we have developed for performing intravital imaging of mammary tumors. We provide procedures for generating tumors through injection of tumor cell lines, and multiphoton imaging using a skin-flap tumor dissection and a mammary imaging window.

Abstract 552: Microglia-stimulation of glioma cell invasion is dependent on EGFR and CSF1R signaling

The ability of glioma tumor cells to invade surrounding brain parenchyma is what makes complete removal of tumor nearly impossible resulting in a median survival of only 12 months for patients afflicted by this disease. Targeting the motile properties of this tumor therefore, is an attractive strategy for therapeutic intervention. Many recent studies have demonstrated a key role for the tumor microenvironment in promoting tumor cell invasion and metastasis. Our laboratory and collaborators have demonstrated that tumor associated macrophages (TAMs) play a critical role in breast carcinoma invasion and metastasis. Here I propose a similar mechanism may occur between glioma cells and microglia within the brain. In this study we demonstrate that murine microglia are able to enhance GL261 glioma cell invasion into Matrigel in co-culture assays by up to 3 fold. Furthermore, we have found using pharmacological and/or antibody mediated inhibition of EGFR or CSF1R signaling abrogates this effect. GL261 cells constituitively secrete CSF-1, the levels of which are unaffected by EGF stimulation, EGFR inhibition or coculture with microglia. Disruption of EGF binding to EGFR using an EGF-specific function-blocking antibody also inhibits microglia-stimulated invasion, showing that EGF is responsible for mediating invasion. This data strongly suggests a paracrine loop exists between microglia and glioma similar to that seen in the breast cancer model. It is our hope that the results of this study may offer novel therapeutic approaches against glioblastoma by targeting functions of the tumor associated microglia as well as the glioma cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 552.

Dendra2 photoswitching through the Mammary Imaging Window

In the last decade, intravital microscopy of breast tumors in mice and rats at single-cell resolution^1-4 has resulted in important insights into mechanisms of metastatic behavior such as migration, invasion and intravasation of tumor cells^{5, 6}, angiogenesis³ and immune cells response^7-9. We have recently reported a technique to image orthotopic mammary carcinomas over multiple intravital imaging sessions in living mice¹⁰. For this, we have developed a Mammary Imaging Window (MIW) and optimized imaging parameters for Dendra2¹¹ photoswitching and imaging in vivo. Here, we describe the protocol for the manufacturing of MIW, insertion of the MIW on top of a tumor and imaging of the Dendra2- labeled tumor cells using a custom built imaging box. This protocol can be used to image the metastatic behavior of tumor cells in distinct microenvironments in tumors and allows for long term imaging of blood vessels, tumor cells and host cells.

ERBB1 and ERBB2 have distinct functions in tumor cell invasion and intravasation

PURPOSE

The epidermal growth factor receptor (ERBB1) and related family member HER-2/neu (ERBB2) are often overexpressed in aggressive breast cancers and their overexpression is correlated with poor prognosis. Clinical studies using ERBB inhibitors have focused on tumor growth effects, but ERBBs can contribute to malignancy independent of their effects on tumor growth. Our studies were designed to evaluate the effect of ERBB inhibition on tumor cell motility and intravasation in vivo using clinically relevant small-molecule inhibitors.

EXPERIMENTAL DESIGN

Using in vivo mouse models of breast cancer, we test the effects of ERBB1 and ERBB2 inhibitors AC480 and lapatinib, ERBB1 inhibitor gefitinib, and ERBB2 inhibitor AG825 on in vivo tumor cell invasive properties in mammary fat pad tumors.

RESULTS

ERBB1 and ERBB2 inhibition rapidly (within 3 h) inhibits both tumor cell motility and intravasation. Using gefitinib, ERBB1 inhibition rapidly inhibits tumor cell motility and invasion but not intravasation, whereas ERBB2 inhibition by AG825 rapidly blocks intravasation.

CONCLUSIONS

ERBB1 and ERBB2 inhibition can rapidly block tumor cell invasive properties. In addition, we differentiate for the first time the contributions of ERBB1 and ERBB2 to the key metastatic properties of in vivo tumor cell invasion and intravasation. These experiments temporally and molecularly separate two key stages in tumor cell entry into blood vessels: invasion and intravasation. These results indicate that ERBB inhibition should be considered for blocking other tumor cell malignant properties besides growth.

The EGF/CSF-1 paracrine invasion loop can be triggered by heregulin beta1 and CXCL12

An important step in the process of metastasis from the primary tumor is invasive spread into the surrounding stroma. Using an in vivo invasion assay, we have previously shown that imposed gradients of epidermal growth factor (EGF) or colony-stimulating factor-1 (CSF-1) can induce invasion through an EGF/CSF-1 paracrine loop between cancer cells and macrophages. We now report that invasion induced by other ligands also relies on this EGF/CSF-1 paracrine invasive loop. Using an in vivo invasion assay, we show that MTLn3 breast cancer cells overexpressing ErbB3 exhibit enhanced invasion compared with control MTLn3 cells in response to the ErbB3 ligand HRG-beta1. The invasive response of both MTLn3-ErbB3 and transgenic MMTV-Neu tumors to HRG-beta1 is inhibited by blocking EGF receptor, CSF-1 receptor, or macrophage function, indicating that invasiveness to HRG-beta1 is dependent on the EGF/CSF-1 paracrine loop. Furthermore, we show that CXCL12 also triggers in vivo invasion of transgenic MMTV-PyMT tumors in an EGF/CSF-1-dependent manner. Although the invasion induced by HRG-beta1 or CXCL12 is dependent on the EGF/CSF-1 paracrine loop, invasion induced by EGF is not dependent on HRG-beta1 or CXCL12 signaling, showing an asymmetrical relationship between different ligand/receptor systems in driving invasion. Our results identify a stromal/tumor interaction that acts as an engine underlying invasion induced by multiple ligands.

Intravital imaging of metastatic behavior through a mammary imaging window

We report a technique to evaluate the same tumor microenvironment over multiple intravital imaging sessions in living mice. We optically marked individual tumor cells expressing photoswitchable proteins in an orthotopic mammary carcinoma and followed them for extended periods through a mammary imaging window. We found that two distinct microenvironments in the same orthotopic mammary tumor affected differently the invasion and intravasation of tumor cells.

Imaging tumor cell movement in vivo

This unit describes the methods that we have been developing for analyzing tumor cell motility in mouse and rat models of breast cancer metastasis. Rodents are commonly used to provide a mammalian system for studying human tumor cells as xenografts in immunocompromised mice, as well as for following the development of tumors from a specific tissue type in transgenic lines. The Basic Protocol describes the standard methods used for generation of mammary tumors and imaging them. Additional protocols for labeling macrophages, blood vessel imaging, and image analysis are also included.

Cell motility and cytoskeletal regulation in invasion and metastasis

Cell motility and chemotaxis can make important contributions to the metastatic cascade. Cell migration pathways in general play significant roles in a variety of physiological processes that can be "hijacked" by cancer cells. Both growth factors and chemokines provide important chemotactic signals in development and metastasis. Receptor activation, following binding of a growth factor or a chemokine, leads to dynamic morphological changes in the actin cytoskeleton network via a variety of distinct and interconnected pathways, resulting in translocation of the cell up a chemoattractant gradient. Such gradients may be produced by stromal cells in the local microenvironment, including macrophages and fibroblasts. A better understanding of the mechanisms of cell motility and cytoskeletal regulation may provide novel therapeutic strategies that would block metastatic progression, reducing dissemination of tumor cells and increasing patient survival.

Soluble nonclassical HLA generated by the metalloproteinase pathway

Soluble human leukocyte antigens (HLA-A, -B, and -C) proteins can be generated by a membrane-bound metalloproteinase (MPase). The MPase-mediated pathway produces soluble nonconformed HLA proteins susceptible to further degradation, and also HLA proteins with high affinity peptides stable at physiologic temperatures. Accessibility of classical HLA to the MPase cleavage inversely correlates with stability of heavy chain (HC) interactions with beta2-microglobulin (beta(2)m). Whether a MPase is involved in release of soluble nonclassical HLA or CD1 proteins is unknown. We have investigated this question with transfectants expressing full-length HLA proteins. Native surface HLA-E and -G complexes, similar to HLA-A2, were unstable at low pH and dissociated giving rise to beta(2)m-free HC. Furthermore, HLA-E and -G proteins, similar to HLA-A2, were readily released from cell surface into supernatants as soluble 37-kilodalton beta(2)m-free HC. However, the stability of surface CD1d complexes was not affected by pH changes and no soluble CD1d was detected. Because beta(2)m-free CD1d HC were expressed on cells, the lack of cleaved soluble products cannot be explained by high stability of native complexes. Instead, absence of a CD1d-specific MPase in these cells or its impaired interactions with substrate HC may be responsible.