Live tumor imaging shows macrophage induction and TMEM-mediated enrichment of cancer stem cells during metastatic dissemination

Cancer stem cells (CSCs) play an important role during metastasis, but the dynamic behavior and induction mechanisms of CSCs are not well understood. Here, we employ high-resolution intravital microscopy using a CSC biosensor to directly observe CSCs in live mice with mammary tumors. CSCs display the slow-migratory, invadopod-rich phenotype that is the hallmark of disseminating tumor cells. CSCs are enriched near macrophages, particularly near macrophage-containing intravasation sites called Tumor Microenvironment of Metastasis (TMEM) doorways. Substantial enrichment of CSCs occurs on association with TMEM doorways, contributing to the finding that CSCs represent >60% of circulating tumor cells. Mechanistically, stemness is induced in non-stem cancer cells upon their direct contact with macrophages via Notch-Jagged signaling. In breast cancers from patients, the density of TMEM doorways correlates with the proportion of cancer cells expressing stem cell markers, indicating that in human breast cancer TMEM doorways are not only cancer cell intravasation portals but also CSC programming sites.

Hematogenous Dissemination of Breast Cancer Cells From Lymph Nodes Is Mediated by Tumor MicroEnvironment of Metastasis Doorways

In primary breast tumors, cancer cells hematogenously disseminate through doorways in the vasculature composed of three-cell complexes (known as Tumor MicroEnvironment of Metastasis) comprising a perivascular macrophage, a tumor cell overexpressing the actin-regulatory protein Mammalian Enabled (Mena), and an endothelial cell, all in direct physical contact. It has been previously shown that once tumor cells establish lymph node metastases in patients, TMEM doorways form in the metastatic tumor cell nests. However, it has not been established if such lymph node-TMEM doorways actively transit tumor cells into the peripheral circulation and on to tertiary sites. To address this question in this short report, we used a mouse model of lymph node metastasis to demonstrate that TMEM doorways: (1) exist in tumor-positive lymph nodes of mice, (2) are restricted to the blood vascular endothelium, (3) serve as a mechanism for further dissemination to peripheral sites such as to the lungs, and (4) their activity can be abrogated by a pharmaceutical intervention. Our data suggest that cancer cell dissemination via TMEM doorways is a common mechanism of breast cancer cell dissemination to distant sites and thus the pharmacological targeting of TMEM may be necessary, even after resection of the primary tumor, to suppress cancer cell dissemination.

Abstract 372: Macrophage contact-dependent stemness induction and progressive CSC enrichment during metastatic dissemination in breast cancer

Background: Cancer stem cells (CSCs) play an important role during metastatic progression of breast cancer. However, little is known, at the single cell level, about the process of stemness induction in non-stem cells or the dynamic behavior of CSCs during hematogenous dissemination.

Methods: Here, we employed high-resolution intravital multiphoton microscopy with a SOX2/OCT4 responsive fluorescent biosensor for stemness to directly observe the induction of stemness in single non-stem cells and their evolution through the metastatic cascade in living animals using orthotopic breast cancer xenograft model. We confirmed our findings in vitro using tumor cell-macrophage co-culture assays.

Results: We report that, both in vitro and in vivo, direct physical contact with macrophages induces stemness in non-stem cancer cells via juxtacrine Notch-Jagged1 signaling. In vivo, macrophage depletion with clodronate treatment showed a significant decrease in stem cells. In vitro, using either the fate mapping of non-stem cells with or without macrophage contact, or the origin-mapping of stem cells to find whether they originated from non-stem cells or pre-existing stem cells, we found that there was four-fold increase in new CSC induction after direct macrophage contact. In contrast, we did not see any role of macrophages in the expansion of pre-existing CSCs, both in vivo and in vitro, indicating that macrophage contact-dependent stem induction is the primary mechanism of CSC generation.

Using immunohistochemical staining in fixed tissue and live imaging of primary tumors and lungs in mice using optical windows, we found that during the course of dissemination of tumor cells from the primary site, CSCs become progressively enriched in the tumor cell population as they approach dissemination doorways (known as TMEM, Tumor MicroEnvironment of Metastasis), intravasate, circulate and arrive at the lung. Association with and passage through TMEM doorways is the step that generates the greatest enrichment in CSCs (~ 60-fold). On arrival in the lung, CSCs represent more than 75% of the disseminated tumor cell population, greatly enriched compared with their representation in the bulk primary tumor of ~ 1%.

Conclusion: Overall, these data indicate, for the first time, that macrophages associated with TMEM induce CSCs and promote TMEM-mediated CSC intravasation and early metastatic seeding. Our results are consistent with the dramatic enrichment of cancer stem cell markers in association with TMEM in breast cancer patients (Kim et al 2020 AACR abstract) and support a strategy for anti-metastatic therapy.

Citation Format: Ved P. Sharma, Yarong Wang, Binwu Tang, George S. Karagiannis, Emily A. Xue, David Entenberg, Lucia Borriello, Anouchka Coste, Joan G. Jones, Chinmay R. Surve, Dominic Esposito, Maja H. Oktay, Lalage M. Wakefield, John S. Condeelis. Macrophage contact-dependent stemness induction and progressive CSC enrichment during metastatic dissemination in breast cancer [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 372.

Myosin-IIA heavy chain phosphorylation on S1943 regulates tumor metastasis

Nonmuscle myosin-IIA (NMHC-IIA) heavy chain phosphorylation has gained recognition as an important feature of myosin-II regulation. In previous work, we showed that phosphorylation on S1943 promotes myosin-IIA filament disassembly in vitro and enhances EGF-stimulated lamellipod extension of breast tumor cells. However, the contribution of NMHC-IIA S1943 phosphorylation to the modulation of invasive cellular behavior and metastasis has not been examined. Stable expression of phosphomimetic (S1943E) or non-phosphorylatable (S1943A) NMHC-IIA in breast cancer cells revealed that S1943 phosphorylation enhances invadopodia function, and is critical for matrix degradation in vitro and experimental metastasis in vivo. These studies demonstrate a novel link between NMHC-IIA S1943 phosphorylation, the regulation of extracellular matrix degradation and tumor cell invasion and metastasis.

Abstract IA16: Macrophages orchestrate early dissemination and metastasis

Cancer cell dissemination can occur during very early stages of breast cancer, but the mechanisms controlling this process are unclear. Here we show that a previously reported early MMTV-HER2+/P-p38lo/TWISThi/E-cadherinlo cancer cell subpopulation depends on macrophages for early dissemination. Depletion of macrophages before overt tumor detection drastically reduced early dissemination and diminished the late metastatic burden. CD206+/Tie2+ macrophages were attracted into early lesions in part by CCL2 produced by early HER2+ cancer cells and myeloid cells. Upregulation of Wnt-1 by macrophages could be stimulated by CCL2 and correlated with loss of E-cadherin in HER2+ early cancer cells. Both MMTV-PyMT and MMTV-HER2 early lesions showed macrophage-containing tumor microenvironments of metastasis (TMEM) structures, and PyMT early cancer cells also showed a reduction in early lesion E-cadherin junctions. Intraepithelial macrophages and loss of E-cadherin junctions was also found more frequently in high-grade human DCIS than in low-grade and normal breast tissue, but no association was found with HER2 status. We reveal a previously unrecognized mechanism by which macrophages play a causal role in early dissemination, impacting long-term metastasis development.

Citation Format: Nina Linde, Maria Casanova-Acebes, Maria Soledad Sosa, Arthur Mortha, Adeeb Rahman, Eduardo F. Farias, Kathryn Harper, Ethan Tardio, Ivan Reyes-Torres, Joan G. Jones, John S. Condeelis, Miriam Merad, Julio A. Aguirre-Ghiso. Macrophages orchestrate early dissemination and metastasis [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr IA16.

Abstract 67: Chemotherapy induced pro-metastatic changes in the primary breast tumors of racially diverse patients

Neoadjuvant chemotherapy (NAC) induces influx of bone marrow-derived proangiogenic Tie2hi monocytes into the primary tumor, resulting in increased density of perivascular Tie2hi macrophages (1). Perivascular Tie2hi/Vegfhi macrophages in physical contact with Mena expressing cancer cells create micro-anatomic sites of transient vascular permeability called TMEM, which mediate cancer cell intravasation and dissemination (2). Cancer cells capable of intravasation via TMEM sites express high level of MenaINV, an isoform of Mena, induced by macrophage contact, which renders tumor cells intravasation-competent (3, 4). Consequently, breast cancers from mice and patients treated with NAC have increased density of TMEM sites and show increased expression of MenaINV (1) Moreover, in PyMT mouse mammary carcinoma and patient derived xenografts, NAC increases the number of circulating tumor cells and lung metastasis (1). The Tie2-inhibitor rebastinib, which inhibits TMEM function, can reverse chemotherapy-induced increases in the number of CTCs and lung metastasis in mouse mammary carcinoma (1, 5). Although NAC induces pro-metastatic changes in breast cancer microenvironment, large randomized prospective studies did not find significant differences in distant-recurrence free survival (DRFS) and overall survival (OS) between breast cancer patients treated with adjuvant and neoadjuvant chemotherapy in predominantly white populations. Since the breast cancer microenvironment in black women has higher microvascular density and density of Tie2hi macrophages, suggesting that black women may be more prone to develop TMEM-associated pro-metastatic changes in response to NAC, we questioned if there is a difference in DRFS in black women treated with NAC compared to AC. We evaluated DRFS in 1,211 racially diverse patients with localized or regionally advanced breast cancer treated with neoadjuvant or adjuvant chemotherapy between January 2000 and December 2016 and found that black patients with localized breast cancer treated with systemic neoadjuvant chemotherapy not only have inferior DRFS compared to white patients, but also worse DRFS when compared to black patients treated with adjuvant chemotherapy, after adjustment for clinical covariates in multivariate analysis. The biologic factors contributing to this finding, in particular TMEM-mediated pro-metastatic changes have been evaluated and will be discussed. 1. Karagiannis et al, Sci Transl Med. 2017;9:397. 2. Harney et al, Cancer discovery. 2015;5:932. 3. Pignatelli J et al, Sci Rep. 2016;6:37874. 4. Pignatelli J et al, Sci Signal. 2014;7:353. 5. Harney et al, Mol Cancer Ther. 2017;16:2486.

Citation Format: George S. Karagiannis, Jessica M. Pastoriza, Sonali Lanjawar, Yarong Wang, David Entenberg, Esther Cheng, Timothy M. Dalfonso, Joan G. Jones, Jesus Anampa, Thomas E. Rohan, Joseph A. Sparano, John S. Condeelis, Maja H. Oktay. Chemotherapy induced pro-metastatic changes in the primary breast tumors of racially diverse patients [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 67.

Neoadjuvant chemotherapy induces breast cancer metastasis through a TMEM-mediated mechanism

Breast cancer cells disseminate through TIE2/MENA^Calc/MENA^INV-dependent cancer cell intravasation sites, called tumor microenvironment of metastasis (TMEM), which are clinically validated as prognostic markers of metastasis in breast cancer patients. Using fixed tissue and intravital imaging of a PyMT murine model and patient-derived xenografts, we show that chemotherapy increases the density and activity of TMEM sites and Mena expression and promotes distant metastasis. Moreover, in the residual breast cancers of patients treated with neoadjuvant paclitaxel after doxorubicin plus cyclophosphamide, TMEM score and its mechanistically connected MENA^INV isoform expression pattern were both increased, suggesting that chemotherapy, despite decreasing tumor size, increases the risk of metastatic dissemination. Chemotherapy-induced TMEM activity and cancer cell dissemination were reversed by either administration of the TIE2 inhibitor rebastinib or knockdown of the MENA gene. Our results indicate that TMEM score increases and MENA isoform expression pattern changes with chemotherapy and can be used in predicting prometastatic changes in response to chemotherapy. Furthermore, inhibitors of TMEM function may improve clinical benefits of chemotherapy in the neoadjuvant setting or in metastatic disease.

The Selective Tie2 Inhibitor Rebastinib Blocks Recruitment and Function of Tie2Hi Macrophages in Breast Cancer and Pancreatic Neuroendocrine Tumors

Tumor-infiltrating myeloid cells promote tumor progression by mediating angiogenesis, tumor cell intravasation, and metastasis, which can offset the effects of chemotherapy, radiation, and antiangiogenic therapy. Here, we show that the kinase switch control inhibitor rebastinib inhibits Tie2, a tyrosine kinase receptor expressed on endothelial cells and protumoral Tie2-expressing macrophages in mouse models of metastatic cancer. Rebastinib reduces tumor growth and metastasis in an orthotopic mouse model of metastatic mammary carcinoma through reduction of Tie2⁺ myeloid cell infiltration, antiangiogenic effects, and blockade of tumor cell intravasation mediated by perivascular Tie2^Hi/Vegf-A^Hi macrophages in the tumor microenvironment of metastasis (TMEM). The antitumor effects of rebastinib enhance the efficacy of microtubule inhibiting chemotherapeutic agents, either eribulin or paclitaxel, by reducing tumor volume, metastasis, and improving overall survival. Rebastinib inhibition of angiopoietin/Tie2 signaling impairs multiple pathways in tumor progression mediated by protumoral Tie2⁺ macrophages, including TMEM-dependent dissemination and angiopoietin/Tie2-dependent angiogenesis. Rebastinib is a promising therapy for achieving Tie2 inhibition in cancer patients. Mol Cancer Ther; 16(11); 2486-501. ©2017 AACR.

Abstract 3963: Neoadjuvant chemotherapy promotes prometastatic changes in the primary breast tumor microenvironment in mice and humans

Chemotherapy induces influx of bone marrow-derived proangiogenic Tie2hi monocytes in primary tumors. Tie2hi perivascular macrophages specifically induce the prometastatic Mena isoforms in tumor cells and can assemble specialized microanatomical sites called “tumor microenvironment of metastasis” (TMEM), structures that may serve as doorways for intravasation of tumor cells in mammary tumors. Both TMEM and MenaINV are required for tumor cell intravasation and dissemination. Thus, we hypothesized that chemotherapy may increase the density of TMEM sites and MenaINV-expressing, intravasation-competent tumor cells, resulting in increased tumor cell invasion and metastasis. We studied these potential pro-metastatic effects of chemotherapy in a neoadjuvant setting (NAC) by either administering paclitaxel or a combination of doxorubicin and cyclophosphamide in several mammary carcinoma mouse and human breast cancer models. As expected, chemotherapy delayed tumor growth, yet it significantly increased the recruitment of TMEM-forming, perivascular Tie2hi/Vegfhi macrophages and TMEM density. Using high-resolution multiphoton intravital imaging in live tumor-bearing mice, we observed that paclitaxel also increased the activity of TMEM sites, visualized as endothelial cell tight-junction disruption around TMEM and subsequent intravasation of the migratory cancer cell subpopulation. Indeed, paclitaxel-treated mice have higher numbers of circulating tumor cells, single cell seeding in lungs and incidence and number of micrometastatic foci, all associated with increased TMEM activity, as demonstrated by high-resolution imaging techniques. Tie2 inhibitors reversed paclitaxel-induced pro-metastatic phenotypes without affecting the assembly of TMEM, indicating that Tie2-mediated signaling is required for paclitaxel-mediated cancer cell dissemination via TMEM. Paclitaxel also caused a significant increase in the expression of MenaINV at both the gene and protein levels. Furthermore, paclitaxel treatment in Mena-/- breast tumor-bearing mice resulted in failure to assemble TMEM and to increase circulating-tumor cells and cancer cell metastasis despite the fact that Tie2hi macrophages are attracted to perivascular niches as a result of paclitaxel treatment. This indicated that Mena is involved in the paclitaxel-mediated increase in cancer cell dissemination but not required for Tie2hi macrophage recruitment. These pre-clinical data are further supported by findings from a cohort (N=20) of breast cancer patients, who received pre-operative paclitaxel-based chemotherapy and demonstrated significant increases in TMEM density and MenaINV expression. Together, our data provide solid evidence that NAC leads to metastasis in rodents via TMEM/ MenaINV-mediated mechanisms, and to cancer cell dissemination in certain clinical scenarios in humans.

Citation Format: George S. Karagiannis, Jessica Pastoriza, Jeanine Pignatelli, Yarong Wang, Allison S. Harney, David Entenberg, Ved P. Sharma, Emily Xue, Esther Cheng, Timothy M. D'Alfonso, Joan G. Jones, Jesus Anampa, Thomas E. Rohan, Joseph A. Sparano, John S. Condeelis, Maja H. Oktay. Neoadjuvant chemotherapy promotes prometastatic changes in the primary breast tumor microenvironment in mice and humans [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3963. doi:10.1158/1538-7445.AM2017-3963

Abstract P2-05-06: Analytical and clinical validation of a fully automated tissue-based quantitative assay (MetaSite Breast™) to detect the likelihood of distant metastasis in hormone receptor (HR)-positive, HER2-negative early stage breast cancer (ESBC)

Background: MetaSite Breast™ is a validated assay to predict risk of distant breast cancer metastasis in patients with HR+/HER2- ESBC. The assay measures the number of MetaSites defined as tumor microanatomic structures composed of MENA protein expressing tumor cells in contact with CD31+ endothelial cells and CD68+ macrophages. Previous studies have demonstrated that an increased number of these microanatomic structures is associated with distant metastasis (DM) in HR+/HER2- ESBC independent of clinicopathologic features. Analytical validation of MetaSite Breast™ demonstrated precision of 97-99% (repeat image analysis of the same slide) and performance of 91-96% (staining and image analysis of serial tumor sections). We sought to further understand the importance of the MetaSite in predicting distant breast cancer metastasis utilizing a fully automated prognostic assay in an independent large patient cohort.

Methods: We conducted a nested case-control study within a cohort of 3,760 patients diagnosed between 1980 and 2000 with invasive breast cancer from the Kaiser Permanente Northwest health care system. Cases (n=259) were women who developed a subsequent distant metastasis; controls, selected using incidence density sampling, were matched closely to cases (1:1) on age at and calendar year of primary diagnosis. Of the 481 patient tumor samples evaluated in this study, 57% were HR+/HER2-, 19% were triple negative (TN), and 15% were HER2+ disease. Multivariate models were adjusted for clinical factors including: lymph node status, tumor size, tumor grade, and HRT; as well as matching variables: age and year of diagnosis. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression.

Results: In the HR+/HER2- group, MetaSite Score (MS) ranged from 0-357 and the mean was 44.6. MS was a significant predictor of DM (P=0.039) in patients with HR+/HER2- disease. Cut-points based on tertiles of MS in all 259 controls defined intermediate (13-41) and high (>41) risk groups that were significantly associated with risk of DM versus the low risk group (OR=2.24; 95%CI=1.23-4.13, P=0.009) and (OR=2.94; 95%CI=1.62-5.41, P=0.0005), respectively. Univariate estimates of absolute risk of DM with cutoffs based on 90% sensitivity and specificity were 9.4% for the low risk group (MS<7), 14.1% for the intermediate (MS=7-91), and 23.4% for the high (MS>91). When adjusted for clinical factors, estimates of absolute risk of DM were 6.6%, 14.1%, and 33.0% for the low, intermediate, and high risk groups, respectively. A binary cut-point for the high risk group was determined (MS>14) and was significant with a 2-fold higher risk of DM versus the low risk group and adjusted for clinical covariates (P=0.036). MS was not positively associated with DM in TN or HER2+ disease.

Conclusions: MetaSite Breast™ significantly predicted the risk of distant breast cancer metastasis in ESBC patients with HR+/HER2-disease, independent of classical clinicopathologic features.

Citation Format: Donovan MJ, Jones JG, Entenberg DR, Condeelis JS, D'alfonso TM, Gustavson M, Molinaro A, Oktay MH, Xue X, Sparano JA, Peterson MA, Podznyakova O, Rohan TE, Shuber AP, Gertler FB, Ly A, Divelbiss ME, Hamilton DA. Analytical and clinical validation of a fully automated tissue-based quantitative assay (MetaSite Breast™) to detect the likelihood of distant metastasis in hormone receptor (HR)-positive, HER2-negative early stage breast cancer (ESBC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-05-06.

Abstract PD5-02: Paclitaxel induced mena- and TMEM-mediated pro-metastatic changes in the breast cancer microenvironment

Background: Breast cancer cell intravasation and dissemination occurs specifically at microanatomical structures that we call tumor-microenvironment of metastasis (TMEM), representing direct physical contact between a tumor cell expressing the actin-regulatory protein Mammalian-enabled (Mena), a perivascular Tie2hi/Vegfhi-expressing macrophage, and an endothelial cell (Harney et al. Cancer Discovery 2015). TMEM sites have been identified in mouse and human mammary carcinomas, and both TMEM density (Rohan et al. JNCI 2014) and invasive Mena isoform expression (Agarwal et al. Breast Cancer Res, 2012; Forse et al. BMC Cancer, 2015]) correlates with metastasis in early stage breast cancer. Since cytotoxic agents such as PTX induce influx of bone marrow-derived progenitors that differentiate into Tie2hi/VEGFhi macrophages in the primary tumor, we hypothesized that PTX may potentiate tumor cell invasion and metastasis by inducing the formation of TMEM sites and/or function.

Methods and Results in humans: We analyzed the effect of chemotherapy on TMEM and invasive Mena isoforms in 10 patients with localized breast cancer who had residual disease after neoadjuvant chemotherapy (NAC: weekly paclitaxel followed by dose-dense doxorubicin-cyclophosphamide [AC]), of whom 7 had more than 2-fold increase in TMEM density in residual disease compared with pretreatment. In a separate cohort of 5 patients, NAC produced an acute increase of up to 150-fold in invasive Mena isoforms after 1-2 doses of NAC.

Methods and Results in mice: After our preliminary data in humans, we evaluated effects of PTX in 4 different models, including 2 mouse models (PyMT-spontaneous & transplantation) and 2 patient-derived xenograft (PDX) triple negative models (HT17, HT33). Although PTX delayed primary tumor growth, tumors in PTX-treated mice had significantly more TMEM sites, circulating tumor cells (CTCs) and metastatic foci when compared to vehicle-treated animals. Using intravital imaging of MMTV-PyMT-Dendra2/Cfms-CFP mice, PTX induced influx of macrophages into primary tumors and intravasation of cancer cells at TMEM sites. Furthermore, PTX treatment significantly increased expression of Mena at the gene and protein levels, including invasive Mena isoforms. Deletion of the Mena gene completely abolished dissemination and metastasis in all cases, including those treated with PTX.

Conclusions: We show in mammary carcinoma mouse models and PDX models that although PTX delays tumor growth, it induces invasive Mena isoform expression and significantly increases the density of TMEM sites that are responsible for cancer cell intravasation, dissemination and metastasis. Thus, our data indicate that PTX paradoxically induces dissemination of breast cancer cells by promoting invasive Mena isoforms and TMEM-mediated cancer cell intravasation, suggesting that blockade of TMEM assembly and/or function could enhance the effectiveness of PTX and possibly other cytotoxic agents commonly used to treat early and advanced stage breast cancer.

Citation Format: Karagiannis GS, Pastoriza JM, Wang Y, Harney AS, Entenberg D, Pignatelli J, Jones JG, Anampa J, Sparano JA, Rohan TE, Condeelis JS, Oktay MH. Paclitaxel induced mena- and TMEM-mediated pro-metastatic changes in the breast cancer microenvironment [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD5-02.

Induction of lipogenesis in white fat during cold exposure in mice: link to lean phenotype

BACKGROUND/OBJECTIVE

Futile substrate cycling based on lipolytic release of fatty acids (FA) from intracellular triacylglycerols (TAG) and their re-esterification (TAG/FA cycling), as well as de novo FA synthesis (de novo lipogenesis (DNL)), represent the core energy-consuming biochemical activities of white adipose tissue (WAT). We aimed to characterize their roles in cold-induced thermogenesis and energy homeostasis.

METHODS

Male obesity-resistant A/J and obesity-prone C57BL/6J mice maintained at 30 °C were exposed to 6 °C for 2 or 7 days. In epididymal WAT (eWAT), TAG synthesis and DNL were determined using in vivo ²H incorporation from ²H₂O into tissue TAG and nuclear magnetic resonance spectroscopy. Quantitative real-time-PCR and/or immunohistochemistry and western blotting were used to determine the expression of selected genes and proteins in WAT and liver.

RESULTS

The mass of WAT depots declined during cold exposure (CE). Plasma levels of TAG and non-esterified FA were decreased by day 2 but tended to normalize by day 7 of CE. TAG synthesis (reflecting TAG/FA cycle activity) gradually increased during CE. DNL decreased by day 2 of CE but increased several fold over the control values by day 7. Expression of genes involved in lipolysis, glyceroneogenesis, FA re-esterification, FA oxidation and mitochondrial biogenesis in eWAT was induced during CE. All these changes were more pronounced in obesity-resistant A/J than in B6 mice and occurred in the absence of uncoupling protein 1 in eWAT. Expression of markers of glyceroneogenesis in eWAT correlated negatively with hepatic FA synthesis by day 7 in both strains. Leptin and fibroblast growth factor 21 plasma levels were differentially affected by CE in the two mouse strains.

CONCLUSIONS

Our results indicate integrated involvement of (i) TAG/FA cycling and DNL in WAT, and (ii) hepatic very-low-density lipoprotein-TAG synthesis in the control of blood lipid levels and provision of FA fuels for thermogenesis in cold. They suggest that lipogenesis in WAT contributes to a lean phenotype.

A mechanistic approach to modelling the formation of a drug reservoir in the skin

It has been shown that prolonged systemic presence of a drug can cause a build-up of that drug in the skin. This drug 'reservoir', if properly understood, could provide useful information about recent drug-taking history of the patient. We create a pair of coupled mathematical models which combine to explore the potential for a drug reservoir to establish based on the kinetic properties of the drug. The first compartmental model is used to characterise time-dependent drug concentrations in plasma and tissue following a customisable drug regimen. Outputs from this model provide boundary conditions for the second, spatio-temporal model of drug build-up in the skin. We focus on drugs that are highly bound as this will restrict their potential to move freely into the skin but which are lipophilic so that, in the unbound form, they would demonstrate an affinity to the outer layers of the skin. Buprenorphine, a drug used to treat opiate addiction, is one example of a drug satisfying these properties. In the discussion we highlight how our study might be used to inform future experimental design and data collection to provide relevant parameter estimates for reservoir formation and its potential to contribute to enhanced drug monitoring techniques.

Abstract 1528: Selective gene-expression profiling of metastasizing breast tumor cell subpopulations complements the predictive power of Mammaprint Dx and Oncotype Dx

Gene-expression profiling has yielded prognostic tests, such as MammaPrint and Oncotype Dx, which facilitate clinical decision-making in breast cancer patients. These tests are based on signatures constructed from whole tumor tissue, including tumor as well as stromal cells. Since metastatic tumor cells are not uniquely identified in these signatures, these tests may have reduced clinical specificity and sensitivity in predicting risk of metastasis. In contrast, we captured breast cancer cells in the act of migration/dissemination using an in vivo invasion assay and expression profiled these cells to create a distinct signature named the human invasion signature (HIS). A comparison between HIS and MammaPrint in the NKI295 cohort demonstrated that both signatures perform comparably in selecting a group of patients with significantly poorer outcomes. However, when compared to MammaPrint, the initial slope of the high-risk patients identified by the HIS is significantly steeper, suggesting that the HIS may identify patients at higher risk of early distant metastatic recurrence. Therefore HIS carries prognostic information beyond that captured by MammaPrint. Additionally, a more thorough examination of candidate genes present in HIS yielded two predictive tissue-based biomarkers: TMEM score which measures the density of cancer cell intravasation sites, and MenaCalc which measures the expression of invasive isoforms of the actin-regulatory protein Mena (MenaCalc = PanMena-Mena11a), thereby identifying tumor cells that disseminate. Both, TMEM density and MenaCalc independently predict the development of distant metastases in breast cancer patients. Here, we show that in a small patient cohort (n = 58), there is no correlation between TMEM density and the Oncotype recurrence score (RS). In particular, a subgroup of patients had tumors with high-Oncotype DX and low TMEM score while another subgroup had low Oncotype DX and high TMEM score. These findings indicate that TMEM and Oncotype Dx address different tumor biology and could be used in a complementary fashion for more accurate patient stratification, as well as better selection of systemic therapies to avoid over- and under-treatment.

Citation Format: George S. Karagiannis, Sumanta Goswami, Joan G. Jones, Maja H. Oktay, John S. Condeelis. Selective gene-expression profiling of metastasizing breast tumor cell subpopulations complements the predictive power of Mammaprint Dx and Oncotype Dx. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1528.

Abstract 244: Paclitaxel increases the assembly and function of the tumor microenvironment of metastasis in breast cancer

Chemotherapy induces influx of bone marrow-derived progenitors such as mesenchymal stem cells, endothelial progenitors and proangiogenic monocytes into the primary tumor to promote angiogenesis. Thus it is feared that chemotherapy may potentiate tumor cell invasion and metastasis. Here, we show that paclitaxel delays tumor growth in several mammary carcinoma mouse and human breast cancer models, yet it significantly increases the density of microanatomical sites called “tumor microenvironment of metastasis” (TMEM) that are responsible for tumor cell intravasation and dissemination of breast cancer. The TMEM site consists of a Mena-overexpressing cancer cell in direct contact with a Tie2hi/VEGFhi macrophage and an underlying endothelial cell. Mice treated with paclitaxel have significantly more circulating tumor cells (CTCs) and metastatic foci when compared to vehicle-treated animals indicating that the chemotherapy-induced TMEM are active in assisting tumor cell intravasation. Moreover, syngeneic transplantation of Dendra2+/PyMT tumors into FVB recipients showed significantly higher incidence of Dendra2+ cells in the lung, following paclitaxel administration. In parallel experiments, paclitaxel induced the influx of macrophages and intravasation of cancer cells as observed using intravital imaging of MMTV-PyMT-Dendra2/Cfms-CFP mice, in which blood vessels were visualized with Quantum dots. Furthermore, paclitaxel treatment in experimental mice caused a significant increase in the expression of Mena at the gene and protein levels. PCR assays for total Mena (PanMena) or specific Mena isoforms (MenaINV, Mena11a) revealed that this increase was particularly attributed to the invasive Mena isoforms [i.e. MenaINV and MenaCalc (Menacalc = PanMena - Mena11a)]. These pre-clinical data are supported by the findings from a cohort of 10 breast cancer patients who received neoadjuvant dose-dense paclitaxel followed by doxorubicin/ cyclophosphamide. Of these tumors, 7/10 patients had more than 2-fold increase in TMEM density following neoadjuvant chemotherapy regimen. Moreover, chemotherapy produced an acute increase of up to 150-fold in MenaINV expression in 3/7 and up to 5.5-fold in MenaCalc in 3/4 patients who underwent serial fine needle aspiration (FNA) biopsy before and after 1-2 doses of either neoadjuvant paclitaxel or doxorubicin-cyclophosphamide. This is provocative because an increase in either MenaCalc score or TMEM density are independently associated with increased risk of distant recurrence in breast cancer patients. In conclusion, our data indicate that paclitaxel treatment induces intravasation-mediated dissemination of breast cancer cells in rodents and in certain clinical scenarios in humans by promoting increases in MenaCalc expression and TMEM intravasation sites.

Citation Format: George S. Karagiannis, Allison H. Harney, Yarong Wang, Jessica Pastoriza, Jeanine Pignatelli, Jesus Anampa, Joseph A. Sparano, Joan G. Jones, David Entenberg, John S. Condeelis, Maja H. Oktay. Paclitaxel increases the assembly and function of the tumor microenvironment of metastasis in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 244.

Influence of pulmonary factors on pulse oximeter saturation in preterm infants

AIM

To describe how the stability of oxygen saturation measured by pulse oximetry (SpO2%) varies within and between infants with bronchopulmonary dysplasia (BPD).

METHODS

Clinically stable infants with BPD had SpO2 measured at different inspired oxygen concentrations (FIO2 expressed as %). A computer model of gas exchange, that is, ventilation/perfusion ratio (VA/Q) and shunt, plotted the curve of SpO2 versus FIO2 best fitting these data. The slope of this curve is the change in SpO2 per % change in FIO2, hence SpO2 stability, calculated at each SpO2 from 85% to 95%.

RESULTS

Data from 16 infants with BPD previously described were analysed. The dominant gas exchange impairment was low VA/Q (median 0.35, IQR, 0.16-0.4, normal 0.86). Median shunt was 1% (IQR, 0-10.5; normal <2%). Slope varied markedly between infants, but above 95% SpO2 was always <1.5. In infants with least severe BPD (VA/Q ≈0.4, shunt ≤2%) median slope at 85% SpO2 was 5.1 (IQR, 3.7-5.5). With more severe BPD (VA/Q ≤0.3) slope was flatter throughout the SpO2 range. The highest FIO2 for 90% SpO2 was in infants with the lowest VA/Q values.

CONCLUSIONS

In infants with BPD, there was large variation in the slope of the curve relating SpO2% to inspired oxygen fraction in the SpO2 range 85%-95%. Slopes were considerably steeper at lower than higher SpO2, especially in infants with least severe BPD, meaning that higher SpO2 target values are intrinsically much more stable. Steep slopes below 90% SpO2 may explain why some infants appear dependent on remarkably low oxygen flows.

Signatures of breast cancer metastasis at a glance

Gene expression profiling has yielded expression signatures from which prognostic tests can be derived to facilitate clinical decision making in breast cancer patients. Some of these signatures are based on profiling of whole tumor tissue (tissue signatures), which includes all tumor and stromal cells. Prognostic markers have also been derived from the profiling of metastasizing tumor cells, including circulating tumor cells (CTCs) and migratory-disseminating tumor cells within the primary tumor. The metastasis signatures based on CTCs and migratory-disseminating tumor cells have greater potential for unraveling cell biology insights and mechanistic underpinnings of tumor cell dissemination and metastasis. Of clinical interest is the promise that stratification of patients into high or low metastatic risk, as well as assessing the need for cytotoxic therapy, might be improved if prognostics derived from these two types of signatures are used in a combined way. The aim of this Cell Science at a Glance article and accompanying poster is to navigate through both types of signatures and their derived prognostics, as well as to highlight biological insights and clinical applications that could be derived from them, especially when they are used in combination.

Characterization of the expression of the pro-metastatic Mena(INV) isoform during breast tumor progression

Several functionally distinct isoforms of the actin regulatory Mena are produced by alternative splicing during tumor progression. Forced expression of the Mena(INV) isoform drives invasion, intravasation and metastasis. However, the abundance and distribution of endogenously expressed Mena(INV) within primary tumors during progression remain unknown, as most studies to date have only assessed relative mRNA levels from dissociated tumor samples. We have developed a Mena(INV) isoform-specific monoclonal antibody and used it to examine Mena(INV) expression patterns in mouse mammary and human breast tumors. Mena(INV) expression increases during tumor progression and to examine the relationship between Mena(INV) expression and markers for epithelial or mesenchymal status, stemness, stromal cell types and hypoxic regions. Further, while Mena(INV) robustly expressed in vascularized areas of the tumor, it is not confined to cells adjacent to blood vessels. Altogether, these data demonstrate the specificity and utility of the anti-Mena(INV)-isoform specific antibody, and provide the first description of endogenous Mena(INV) protein expression in mouse and human tumors.

Real-Time Imaging Reveals Local, Transient Vascular Permeability, and Tumor Cell Intravasation Stimulated by TIE2hi Macrophage-Derived VEGFA

Dissemination of tumor cells is an essential step in metastasis. Direct contact between a macrophage, mammalian-enabled (MENA)-overexpressing tumor cell, and endothelial cell [Tumor MicroEnvironment of Metastasis (TMEM)] correlates with metastasis in breast cancer patients. Here we show, using intravital high-resolution two-photon microscopy, that transient vascular permeability and tumor cell intravasation occur simultaneously and exclusively at TMEM. The hyperpermeable nature of tumor vasculature is described as spatially and temporally heterogeneous. Using real-time imaging, we observed that vascular permeability is transient, restricted to the TMEM, and required for tumor cell dissemination. VEGFA signaling from TIE2(hi) TMEM macrophages causes local loss of vascular junctions, transient vascular permeability, and tumor cell intravasation, demonstrating a role for the TMEM within the primary mammary tumor. These data provide insight into the mechanism of tumor cell intravasation and vascular permeability in breast cancer, explaining the value of TMEM density as a predictor of distant metastatic recurrence in patients.

SIGNIFICANCE

Tumor vasculature is abnormal with increased permeability. Here, we show that VEGFA signaling from TIE2(hi) TMEM macrophages results in local, transient vascular permeability and tumor cell intravasation. These data provide evidence for the mechanism underlying the association of TMEM with distant metastatic recurrence, offering a rationale for therapies targeting TMEM.

Abstract 4075: Proportion of breast cancer stem cells in fine needle aspirates co-relates with the marker of metastatic outcome TMEM

Cell surface biomarkers CD44, CD24 and CD133 and intracellular marker ALDH1 have recently been used to identify breast cancer stem cells. A very small number of these cancer stem cells can initiate a tumor growth and cause it to metastasize. The micro-anatomical sites of hematogenous dissemination of breast cancer cells called Tumor MicroEnvironment of Metastasis (TMEM) have been described in formalin-fixed paraffin-embedded invasive ductal carcinomas from patients. These sites are defined as the direct apposition of tumor cells and perivascular macrophages and are visualized using triple immunohistochemistry for CD68, CD31 and Mena to identify the macrophages, endothelial cells and invasive tumor cells respectively. The identification of TMEM sites is clinically important because TMEM density is a predictor of metastatic outcome. Migratory subpopulation of tumor cells has been shown to be enriched for cancer stem cells.

We have performed flow cytometry to identify CD44high/CD24low cells, mRNA fluorescent in situ hybridization (FISH) and qRT-PCR to identify CD133 and ALDH1 expression in breast cancer cells in 50 samples of invasive ductal carcinoma obtained from patients’ cancer excisions by fine needle aspiration (FNA) before formalin fixation. FNA is a minimally invasive method that uses 26 gauge needles to collect discohesive cancer cells primarily by capillary action. The stem cell marker expression was then compared to TMEM scores obtained from the very same cancer excisions after formalin fixation and paraffin embedding.

Our results show very strong correlation between the percentage of CD44high/CD24low cells with TMEM scores (r = 0.91), as well as the percentage of CD133 and ALDH1 expressing cells with TMEM scores (r = 0.88 and 0.86 respectively). We validated the results obtained by FISH with the direct qRT-PCR for CD133 and ALDH1 in the FNA samples. The correlation of CD133 and ALDH1 expression obtained by qRT-PCR with TMEM score was again very strong (r = 0.76 and 0.73 respectively).

Our findings here and those previously reported for migratory tumor cells demonstrate that TMEM rich microenvironments are enriched for cancer stem cells and partially explain positive correlation of TMEM scores with metastasis in patients. They also suggest that the assessment of stem cell proportion in breast cancers can be assessed in FNA samples. The clinical value of stem cell assessment using this approach for prognostic and predictive is under investigation.

Citation Format: Maja H. Oktay, Eli Grunblatt, Sweta Roy, Nathan Agi, Esther Adler, Joan G. Jones, John S. Condeelis, Sumanta Goswami. Proportion of breast cancer stem cells in fine needle aspirates co-relates with the marker of metastatic outcome TMEM. [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 4075. doi:10.1158/1538-7445.AM2015-4075

Abstract 5125: Imaging the tumor microenvironment of metastasis reveals the mechanism of transient blood vessel permeability and tumor cell intravasation

Sites of direct contact between a macrophage, a tumor cell and endothelial cell [Tumor MicroEnvironment of Metastasis (TMEM)], correlates with metastasis in breast cancer patients independently of other clinical prognostic indicators suggesting a direct role for TMEM function in hematogenous dissemination. Here we show, using intravital high-resolution two-photon microscopy, that tumor cell intravasation occurs only at TMEM. Tumor cell intravasation occurs concurrently with transient, local vascular permeability at TMEM in an autochthonous mouse mammary carcinoma model and a human patient-derived xenograft model. Ablation of the presence or activity of the TMEM associated macrophages blocks tumor cell intravasation at TMEM demonstrating an essential role of perivascular macrophages in TMEM function. A subset of TMEM macrophages are identified as Tie2-expressing macrophages that are characterized by F4/80+/CD11b+/CD68+/MRC1+/Tie2Hi/VEGFAHi/CD11c-. VEGFA signaling from Tie2Hi TMEM-associated macrophages causes the local loss of vascular junctions resulting in transient vascular permeability and tumor cell intravasation at TMEM. Macrophage-specific ablation of VEGFA results in increased vascular junction stability and inhibition of intravasation, demonstrating that vascular junction dissolution at VEGFAHi/Tie2Hi TMEM-associated macrophages leads to vascular permeability and tumor cell intravasation. Inhibition of Tie2 with the first in class small molecular inhibitor rebastinib impairs TMEM function leading to a reduction in vascular permeability, tumor cell dissemination and metastasis. Further, rebastinib inhibition of Tie2 blocks tumor cell extravasation and metastatic growth in the lungs.

Together, the findings that TMEM macrophages mediate vascular permeability and tumor cell intravasation demonstrate an essential role for TMEM within the primary mammary tumor as sites of tumor cell dissemination. These data reveal the mechanism of tumor cell intravasation in breast cancer, explain the prognostic value of TMEM density in predicting distant metastatic recurrence in breast cancer patients and document a strategy for inhibition of dissemination.

This research is supported by the Department of Defense Breast Cancer Research Program under award number BC120227 (ASH), NIH CA100324 (JSC) and the Integrated Imaging Program.

Citation Format: Allison S. Harney, Esther N. Arwert, David Entenberg, Yarong Wang, Peng Guo, Bin-Zhi Qian, Bryan D. Smith, Jeffrey W. Pollard, Joan G. Jones, Daniel L. Flynn, John S. Condeelis. Imaging the tumor microenvironment of metastasis reveals the mechanism of transient blood vessel permeability and tumor cell intravasation. [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 5125. doi:10.1158/1538-7445.AM2015-5125

Invasive breast carcinoma cells from patients exhibit MenaINV- and macrophage-dependent transendothelial migration

Metastasis is a complex, multistep process of cancer progression that has few treatment options. A critical event is the invasion of cancer cells into blood vessels (intravasation), through which cancer cells disseminate to distant organs. Breast cancer cells with increased abundance of Mena [an epidermal growth factor (EGF)-responsive cell migration protein] are present with macrophages at sites of intravasation, called TMEM sites (for tumor microenvironment of metastasis), in patient tumor samples. Furthermore, the density of these intravasation sites correlates with metastatic risk in patients. We found that intravasation of breast cancer cells may be prevented by blocking the signaling between cancer cells and macrophages. We obtained invasive breast ductal carcinoma cells of various subtypes by fine-needle aspiration (FNA) biopsies from patients and found that, in an in vitro transendothelial migration assay, cells that migrated through a layer of human endothelial cells were enriched for the transcript encoding Mena(INV), an invasive isoform of Mena. This enhanced transendothelial migration required macrophages and occurred with all of the breast cancer subtypes. Using mouse macrophages and the human cancer cells from the FNAs, we identified paracrine and autocrine activation of colony-stimulating factor-1 receptor (CSF-1R). The paracrine or autocrine nature of the signal depended on the breast cancer cell subtype. Knocking down Mena(INV) or adding an antibody that blocks CSF-1R function prevented transendothelial migration. Our findings indicate that Mena(INV) and TMEM frequency are correlated prognostic markers and CSF-1 and Mena(INV) may be therapeutic targets to prevent metastasis of multiple breast cancer subtypes.

Abstract 4940: Perivascular macrophages induce localized, transient blood vessel permeability and tumor cell intravasation

Metastasis is a multistep process involving tumor and stromal cells. The microanatomical site consisting of a perivascular macrophage interacting with a Mena over-expressing tumor cell has been named the “tumor microenvironment of metastasis” (TMEM). TMEM density predicts distant metastatic recurrence in breast cancer patients making the study of TMEM function essential. In spontaneous orthotopic mouse mammary tumors (MMTV-PyMT), as the tumor progresses to malignancy tumor cells have increased Mena expression and assemble TMEM. TMEM assembly is correlated with elevated levels of circulating tumor cells and lung metastases, indicating a functional role for TMEM in tumor cell dissemination. High-resolution multiphoton-based microscopy at single cell resolution has revealed transient blood vessel permeability events at TMEM, marked by the extravasation of otherwise impermeable serum markers such as Qdots and fluorescent 155 kDa dextran. In proximity to sites of permeability there is increased tumor cell and macrophage motility towards the blood vessel, and local intravasation of tumor cells. Blocking macrophage function results in decreased blood vessel permeability and decreased numbers of circulating tumor cells. TMEM-associated macrophages produce VEGF-A, and blocking VEGF-A reduces blood vessel permeability and circulating tumor cells. The observation that TMEM mediates tumor cell intravasation through localized blood vessel permeability in live animals demonstrates that TMEM is a key metastatic microenvironment in the primary tumor, explains the prognostic value of TMEM density in predicting distant metastatic recurrence in breast cancer patients and suggests a potentially valuable re-tasking of existing anti-angiogenesis drugs.

This research is supported by the Department of Defense [Breast Cancer Research Program)] under award number BC120227 (ASH).

Note: This abstract was not presented at the meeting.

Citation Format: Allison S. Harney, Esther N. Arwert, David Entenberg, Yarong Wang, Joan G. Jones, John S. Condeelis. Perivascular macrophages induce localized, transient blood vessel permeability and tumor cell intravasation. [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 4940. doi:10.1158/1538-7445.AM2014-4940

Tumor microenvironment of metastasis and risk of distant metastasis of breast cancer

BACKGROUND

Tumor microenvironment of metastasis (TMEM), consisting of direct contact between a macrophage, an endothelial cell, and a tumor cell, has been associated with metastasis in both rodent mammary tumors and human breast cancer. We prospectively examined the association between TMEM score and risk of distant metastasis and compared risk associated with TMEM score with that associated with IHC4.

METHODS

We conducted a case-control study nested within a cohort of 3760 patients with invasive ductal breast carcinoma diagnosed between 1980 and 2000 and followed through 2010. Case patients were women who developed a subsequent distant metastasis; control subjects were matched (1:1) on age at and calendar year of primary diagnosis. TMEM was assessed by triple immunostain and IHC4 by standard methods; slides were read by pathologists blinded to outcome. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression, adjusted for clinical variables. A Receiver Operating Characteristic analysis was performed, and the area under the curve was estimated. All statistical tests were two-sided.

RESULTS

TMEM score was associated with increased risk of distant metastasis in estrogen receptor (ER)(+)/human epidermal growth factor receptor (HER2)(-) tumors (multivariable OR high vs low tertile = 2.70; 95% CI = 1.39 to 5.26; P trend = .004), whereas IHC4 score had a borderline positive association (OR10 unit increase = 1.06; 95% CI = 1.00 to 1.13); the association for TMEM score persisted after adjustment for IHC4 score. The area under the curve for TMEM, adjusted for clinical variables, was 0.78. Neither TMEM score nor IHC4 score was independently associated with metastatic risk overall or in the triple negative or HER2(+) subgroups.

CONCLUSIONS

TMEM score predicted risk of distant metastasis in ER(+)/HER2(-) breast cancer independently of IHC4 score and classical clinicopathologic features.

Abstract P6-02-04: TMEM (Tumor MicroEnvironment of Metastasis) in human breast cancer is a blood vessel associated intravasation microenvironment unrelated to lymphatics

In breast cancer, both lymph node and distant metastasis represent dissemination of tumor cells from a primary site, but the mechanism of spread and the subsequent risk of mortality may not be the same. Historically, lymphatic spread has been documented both descriptively, as presence or absence of lymphovascular invasion (LVI), and as a formal part of TNM staging. Until recently, however, there has been no way to directly assess the risk of hematogenous dissemination by the primary tumor.

Observations from multiphoton-based intravital imaging of rodent models of breast cancer and the analysis of Mena function in tumor cells in vivo have characterized an intravasation microenvironment (ME) involved in the systemic dissemination of tumor cells from primary breast tumors. We have identified the corresponding structure in FFPE tissue and called it TMEM (Tumor MicroEnvironment of Metastasis). This microanatomic landmark is defined as the direct apposition of a Mena-overexpressing intravasation competent carcinoma cell, a perivascular macrophage, and an endothelial cell. In a case control study of 30 case-control pairs, where each matched pair differed only in their metastatic status – non-metastatic vs. metastatic – we found that the density of TMEM was significantly associated with development of systemic metastasis (p = 0.00006).

The relationship of hematogenous- and lymphatic-mediated tumor cell spread is not understood. Using the previously described cohort in which we showed that TMEM was associated with metastasis, the purpose of this study was to 1) assess intratumoral lymphatic density, 2) determine if TMEM- lymphatic structures associated with lymphatics exist, and 3) determine if TMEM- lymphatic structures correlate with systemic metastatic risk. Cases were stained with a triple immunostain identical to that used in our earlier study except that D2-40 (a lymphatic marker) was used, rather than CD31 (a blood vessel marker). The marker for macrophages (CD68) and invasive tumor cells (Mena) remained the same. Two pathologists, blinded to outcome, evaluated the presence or absence of intratumoral lymphatics and quantitated the number of TMEM-lymphatic structures per 10 high power (400x) fields in areas of highest intratumoral lymphatic density. A TMEM-lymphatic structure was defined as the direct apposition of a lymphatic (D2-40) endothelial cell with a macrophage and invasive tumor cell.

Intratumoral lymphatics were absent in a majority of tumors in each of the 2 groups (18 of 30 non-metastatic, 16 of 30 metastatic; p = 0.6). TMEM-lymphatic structures were rare and were equally present in the 2 groups (3 metastatic and 3 non-metastatic cases). Using the Wilcoxon (paired) signed-rank test, we found no significant difference in the density of these structures between the two groups (p = 0.4). Furthermore, TMEM-lymphatic structures did not correlate with the presence of lymph node metastases (p = 0.8). We conclude that lymphatic vessels do not participate in the TMEM assembly that has been associated with hematogenous metastasis. TMEM density assessment reflects a hematogenous intravasation ME and offers a novel approach to the assessment of metastatic risk.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-02-04.

Abstract 1410: TMEM (Tumor MicroEnvironment of Metastasis) in human breast cancer is a blood vessel associated intravasation microenvironment unrelated to lymphatics

Observations from intravital imaging (Wyckoff et al. Can Res 2007) and the analysis of Mena function in tumor cells in vivo (Roussos et al. JCS 2011) has characterized an intravasation microenvironment (ME) involved in the systemic dissemination of tumor cells from primary breast tumors. We have identified the corresponding structure in FFPE tissue and called it TMEM (Tumor MicroEnvironment of Metastasis). This microanatomic landmark is defined as the direct apposition of a Mena-overexpressing intravasation competent carcinoma cell, a perivascular macrophage, and an endothelial cell. In a case control study of 60 patients, where each matched pair differed only in their metastatic status - non-metastatic vs. metastatic - the density of TMEM was assessed and found to be significantly associated with development of systemic metastasis (p = 0.00006) (Robinson et al. Clin Can Res 2009). Although lymph node status is considered an important prognostic factor in breast cancer, the direct involvement of lymphatics in systemic tumor cell dissemination from primary tumors has not been demonstrated. In addition, the relationship of hematogenous- and lymphatic-mediated tumor cell spread is not understood. The purpose of this study was to 1) assess intratumoral lymphatic density in this same cohort, 2) determine if TMEM-like structures associated with lymphatics exist, and 3) determine if lymphaticTMEM-like structures correlate with systemic metastatic risk. Cases were stained with a triple immunostain identical to that used in the Robinson et al. study except that D2-40 (a lymphatic marker) was used, rather than CD31 (a blood vessel marker). The marker for macrophages (CD68) and invasive tumor cells (Mena) remained the same. Two pathologists, blinded to outcome, evaluated for the presence or absence of intratumoral lymphatics and quantitated the number of TMEM-like structures per 10 high power (400x) fields in areas of highest intratumoral lymphatic density. A TMEM-like structure was defined as the direct apposition of a lymphatic (D2-40) endothelial cell with a macrophage and invasive tumor cell. Intratumoral lymphatics were absent in a majority of tumors in each of the 2 groups (18 of 30 non-metastatic, 16 of 30 metastatic; p=0.6). TMEM-like structures were rare and were equally present in the 2 groups (3 metastatic and 3 non-metastatic cases). Using the Wilcoxon (paired) signed-rank test, we found no significant difference in the density of these structures between the two groups (p = 0.4). Furthermore, TMEM-like structures did not correlate with the presence of lymph node metastases (p=0.8). We conclude that lymphatic vessels do not participate in the TMEM assembly that has been associated with hematogenous metastasis. TMEM density assessment reflects a hematogenous intravasation ME and offers a novel approach to the assessment of metastatic risk.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1410. doi:1538-7445.AM2012-1410

Correlated immunohistochemical and cytological assays for the prediction of hematogenous dissemination of breast cancer

Although metastasis is a major cause of death from breast cancer, our ability to predict which tumors will metastasize is limited (American Cancer Society 2010). Proper assessment of metastatic risk and elucidating the underlying mechanisms of metastasis will help personalize therapy and may provide insight into potential therapeutic targets. Traditionally, histologic grading, staging, hormone receptors, HER2/Neu, and proliferation assays have been the gold standard on which oncologists based their treatment decisions. However, all of these are indirect measures of metastatic risk. Recent insights from intravital imaging directly address questions of mechanism and have led to a new way of using histologic and cytologic material to assess metastatic risk. This review describes the tumor microenvironment model of invasion and intravasation, as well as an emerging histopathologic application based on this model. In particular, the authors describe a new immunohistochemical approach to the assessment of metastatic risk based on the density of intravasation microenvironment sites called the tumor microenvironment of metastasis. In addition, they describe an isoform assay for the actin regulatory protein Mena using fine needle aspiration samples and the details about how these 2 assays may be applied in clinical practice in a synergistic way to assess the risk of metastasis.

A Cohort Study of p53 Mutations and Protein Accumulation in Benign Breast Tissue and Subsequent Breast Cancer Risk

Mutations in the p53 tumor suppressor gene and accumulation of its protein in breast tissue are thought to play a role in breast carcinogenesis. However, few studies have prospectively investigated the association of p53 immunopositivity and/or p53 alterations in women with benign breast disease in relation to the subsequent risk of invasive breast cancer. We carried out a case-control study nested within a large cohort of women biopsied for benign breast disease in order to address this question. After exclusions, 491 breast cancer cases and 471 controls were available for analysis. Unconditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Neither p53 immunopositivity nor genetic alterations in p53 (either missense mutations or polymorphisms) was associated with altered risk of subsequent breast cancer. However, the combination of both p53 immunopositivity and any p53 nucleotide change was associated with an approximate 5-fold nonsignificant increase in risk (adjusted OR 4.79, 95% CI 0.28-82.31) but the confidence intervals were extremely wide. Our findings raise the possibility that the combination of p53 protein accumulation and the presence of genetic alterations may identify a group at increased risk of breast cancer.

Mena invasive (Mena(INV)) and Mena11a isoforms play distinct roles in breast cancer cell cohesion and association with TMEM

Mena, an actin regulatory protein, functions at the convergence of motility pathways that drive breast cancer cell invasion and migration in vivo. The tumor microenvironment spontaneously induces both increased expression of the Mena invasive (Mena(INV)) and decreased expression of Mena11a isoforms in invasive and migratory tumor cells. Tumor cells with this Mena expression pattern participate with macrophages in migration and intravasation in mouse mammary tumors in vivo. Consistent with these findings, anatomical sites containing tumor cells with high levels of Mena expression associated with perivascular macrophages were identified in human invasive ductal breast carcinomas and called TMEM. The number of TMEM sites positively correlated with the development of distant metastasis in humans. Here we demonstrate that mouse mammary tumors generated from EGFP-Mena(INV) expressing tumor cells are significantly less cohesive and have discontinuous cell-cell contacts compared to Mena11a xenografts. Using the mouse PyMT model we show that metastatic mammary tumors express 8.7 fold more total Mena and 7.5 fold more Mena(INV) mRNA than early non-metastatic ones. Furthermore, Mena(INV) expression in fine needle aspiration biopsy (FNA) samples of human invasive ductal carcinomas correlate with TMEM score while Mena11a does not. These results suggest that Mena(INV) is the isoform associated with breast cancer cell discohesion, invasion and intravasation in mice and in humans. They also imply that Mena(INV) expression and TMEM score measure related aspects of a common tumor cell dissemination mechanism and provide new insight into metastatic risk.

Impaired insulin stimulation of muscular ATP production in patients with type 1 diabetes

OBJECTIVE

in type 2 diabetic patients and their first-degree relatives, insulin resistance (IR) is associated with impairment of insulin-stimulated myocellular glucose-6-phosphate (g6p) and unidirectional flux through ATP synthase (fATP), suggesting the presence of inherited abnormal mitochondrial oxidative fitness. We hypothesized that patients with long-standing type 1 diabetes may also exhibit insulin resistance as well as lower fATP.

DESIGN

this single-centre trial was registered at ClinicalTrials.gov (NCT00481598).

SUBJECTS

we included eight nonobese type 1 diabetic patients (mean diabetes duration: 17 years) with near-target glycaemic control [haemoglobin A1c (HbA1c): 6.8 ± 0.4%] during treatment with continuous subcutaneous insulin infusion pumps and eight healthy volunteers (HbA1c: 5.4 ± 0.2%) of comparable age, body mass and level of physical activity.

OUTCOME MEASURES

myocellular fATP, g6p and intramyocellular lipid content (IMCL) were measured with (1) H/(31) P magnetic resonance spectroscopy during fasting and hyperinsulinaemic-euglycaemic clamp tests.

RESULTS

fasting fATP, g6p and IMCL did not differ between groups. During stimulation by insulin, type 1 diabetic patients exhibited approximately 50% (P < 0.001) lower whole-body glucose disposal along with approximately 42% (P = 0.003) lower intramyocellular g6p and approximately25% (P = 0.024) lower fATP. Insulin-stimulated fATP correlated positively with whole-body insulin sensitivity (R = 0.706, P = 0.002) and negatively with HbA1c (R = -0.675, P = 0.004).

CONCLUSIONS

despite documented near-target glycaemic control for 1 year, nonobese patients with long-standing type 1 diabetes can exhibit insulin resistance. This associates with lower insulin-stimulated flux through muscular ATP synthase which could result from glucose toxicity.

Abstract P3-10-16: Quantitative Subtractive Immunofluorescence To Develop a Surrogate for Mena Inv(asive) Isoform Is Associated with Poor Outcome in Breast Cancer

Introduction:

Previous work has shown that the inv isoform of Mena, an actin binding protein, is associated with invasion at the cellular level and metastasis in the context of the microenvironment in both animal models and humans (Robinson, B.D. et al. Clin Cancer Res 15, 2433-2441 (2009). However, the prognostic value for metastasis of MenaINV itself is unknown because there is no antibody that directly recognizes this isoform. Here we describe a method to assess a surrogate for MenaINV by measuring total Mena and subtracting the levels of the 11a (non-invasive) isoform. Method: Total Mena and Mena11a were measured in two independent retrospective breast cancer cohorts with 20 year follow-up using tissue microarray and quantitative immunofluorescence (AQUA) technology in a previously described multiplexed mode. AQUA scores for each marker were converted into z scores followed by subtraction of Mena 11a (noninvasive form of Mena) from total Mena (invasive and non-invasive) = Mena(inv) surrogate. This was calculated for each patient and correlated with clinical and pathological characteristics as well as disease-free survival in both cohorts.

Results: In the older Yale cohort, Kaplan Meier analysis dividing the Mena(inv) surrogate by quartiles suggested collapse of the top three quartiles followed by comparison to the fourth quartile (log rank p= 0.0003, n=501). The 4th quartile was also significant in node positive (log rank p=0.0047, n=267) and estrogen negative (ER) patient subgroups (log rank p=0.0003, n=234). Cox multivariate analysis showed Mena(inv) was independent of age, tumor size, nuclear grade, nodal status, ER, PR, Her2 (HR=0.636, 95% CI=0.47-0.86, p=0.0038, n=420). The newer Yale cohort showed similar results, but that cohort also had data on local vs. distant recurrence. The relative risk of distant recurrence in this cohort is 2.56 (p=0.011) for patients with high Mena (inv) compared to 1.96 (p=0.055) for any recurrence.

Conclusions: High Mena (inv) surrogate shows prognostic value for poor survival in two independent breast cancer cohorts with some suggestion of preferential prognostic value for distant recurrence.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-10-16.

Subsistence economy of el paraiso, an early peruvian site

Studies of food remains from the Preceramic monumental site of E1 Paraíso, Peru (1800 to 1500 B.C.), have shed new light on a debate regarding the relative importance of seafood versus terrestrial resources and the role of cultigens in subsistence economies during the early development of Peruvian civilization. Fish was the primary animal food at the site whereas plant foods consisted of a mixture of cultivated resources (squashes, beans, peppers, and jicama) with an additional reliance on fruits (guava, lucuma, and pacae). Wild plants, especially the roots of sedges and cat-tail, also may have accounted for a substantial part of the diet. Cotton was a chief crop, used in making fishing tackle and the textiles that served as clothing and items of high value and status. As an example of the beginnings of civilization, El Paraíso is a case in which impressive architecture was built on a relatively simple subsistence economy and energy was expended in the production of resources useful in local and regional exchange systems.

High-frequency mutations in a plasmid-encoded gas vesicle gene in Halobacterium halobium

Gas vesicle-deficient mutants of Halobacterium halobium arise spontaneously at high frequency (about 1%). The mutants are readily detected, forming translucent colonies on agar plates in contrast to opaque wild-type colonies. To investigate the mechanism of this mutation, we recently cloned a plasmid-encoded gas vesicle protein gene, gvpA, from H. halobium. In the wild-type NRC-1 strain the gvpA gene is encoded by a multicopy plasmid of approximately 150 kilobase pairs (kb). We have now characterized 18 gas vesicle-deficient mutants and 4 revertants by phenotypic and Southern hybridization analyses. Our results indicate that the mutants fall into three major classes. Class I mutants are partially gas vesicle-deficient (Vac(delta-)) and unstable, giving rise to completely gas vesicle-deficient (Vac(-)) derivatives and Vac(+) revertants at frequencies of 1-5%. The restriction map of the gvpA gene region in class I mutants is unchanged but the gene copy number is reduced compared to the Vac(+) strains. Class II mutants can be either Vac(delta-) or completely Vac(-) but are relatively stable. They contain insertion sequences within or upstream of the gvpA gene. A Vac(-) class II mutant, R1, contains the 1.3-kb insertion sequence, ISH3, within the gvpA gene, whereas four Vac(delta-) class II mutants contain other insertion sequences upstream of the gene. Class III mutants are stable Vac(-) derivatives of either the wild-type or class I mutants and have no detectable copies of the gvpA gene. Based on these results, we discuss the mechanisms of gas vesicle mutations in H. halobium.

Ecophysiological Evidence that Achromatium oxaliferum Is Responsible for the Oxidation of Reduced Sulfur Species to Sulfate in a Freshwater Sediment

Achromatium oxaliferum is a large, morphologically conspicuous, sediment-dwelling bacterium. The organism has yet to be cultured in the laboratory, and very little is known about its physiology. The presence of intracellular inclusions of calcite and sulfur have given rise to speculation that the bacterium is involved in the carbon and sulfur cycles in the sediments where it is found. Depth profiles of oxygen concentration and A. oxaliferum cell numbers in a freshwater sediment revealed that the A. oxaliferum population spanned the oxic-anoxic boundary in the top 3 to 4 cm of sediments. Some of the A. oxaliferum cells resided at depths where no oxygen was detectable, suggesting that these cells may be capable of anaerobic metabolism. The distributions of solid-phase and dissolved inorganic sulfur species in the sediment revealed that A. oxaliferum was most abundant where sulfur cycling was most intense. The sediment was characterized by low concentrations of free sulfide. However, a comparison of sulfate reduction rates in sediment cores incubated with either oxic or anoxic overlying water indicated that the oxidative and reductive components of the sulfur cycle were tightly coupled in the A. oxaliferum-bearing sediment. A positive correlation between pore water sulfate concentration and A. oxaliferum numbers was observed in field data collected over an 18-month period, suggesting a possible link between A. oxaliferum numbers and the oxidation of reduced sulfur species to sulfate. The field data were supported by laboratory incubation experiments in which sodium molybdate-treated sediment cores were augmented with highly purified suspensions of A. oxaliferum cells. Under oxic conditions, rates of sulfate production in the presence of sodium molybdate were found to correlate strongly with the number of cells added to sediment cores, providing further evidence for a role for A. oxaliferum in the oxidation of reduced sulfur.

A simplified method for deriving shunt and reduced VA/Q in infants

BACKGROUND

Right to left shunt and regional hypoventilation (reduced ventilation/perfusion ratio (V(A)/Q)) have different effects on the curve relating inspired oxygen (P(I)O(2)) to oxygen saturation measured by pulse oximetry (SpO(2)) and can be derived non-invasively from measurements of SpO(2) and inspired oxygen pressure (P(I)O(2)) using complex models of gas exchange. We developed a simpler computerised "slide-rule" method of making these derivations.

AIMS

To describe the slide-rule method and determine agreement between measurements derived with this and a more complex algorithm.

METHODS

Series of P(I)O(2) versus SpO(2) data points obtained during 43 studies in 16 preterm infants with bronchopulmonary dysplasia were analysed. Percentage shunt and the degree of right shift (kPa) of the P(I)O(2) versus SpO(2) curve compared with the oxyhaemoglobin dissociation curve (a measure of V(A)/Q) were determined for each dataset with both methods, and the results were compared using the method of Bland and Altman.

RESULTS

The computer slide-rule method produced results for all 43 datasets. The more complex model could derive results for 40/43 datasets. The mean differences (95% limits of agreement) between the two methods for measurements of shunt were -1.7% (-6.5 to +3.5%) and for measurements of right shift were 0.3 kPa (-2.9 to +3.6 kPa).

CONCLUSION

The slide-rule method was reliable for deriving shunt and right shift (reduced V(A)/Q) of the P(I)O(2) versus SpO(2) curve when compared with the more complex algorithm. The new method should enable wider clinical application of these measurements of oxygen exchange.

Sources of hepatic triglyceride accumulation during high-fat feeding in the healthy rat

Hepatic triglyceride (HTG) accumulation from peripheral dietary sources and from endogenous de novo lipogenesis (DNL) was quantified in adult Sprague-Dawley rats by combining in vivo localized (1)H MRS measurement of total hepatic lipid with a novel ex vivo (2)H NMR analysis of HTG (2)H enrichment from (2)H-enriched body water. The methodology for DNL determination needs further validation against standard methodologies. To examine the effect of a high-fat diet on HTG concentrations and sources, animals (n = 5) were given high-fat chow for 35 days. HTG accumulation, measured by in vivo (1)H MRS, increased significantly after 1 week (3.85 +/- 0.60% vs 2.13 +/- 0.34% for animals fed on a standard chow diet, P < 0.05) and was maintained until week 5 (3.30 +/- 0.60% vs 1.12 +/- 0.30%, P < 0.05). Animals fed on a high-fat diet were glucose intolerant (13.3 +/- 1.3 vs 9.4 +/- 0.8 mM in animals fed on a standard chow diet, for 60 min glycemia after glucose challenge, P < 0.05). In control animals, DNL accounted for 10.9 +/- 1.0% of HTG, whereas in animals given the high-fat diet, the DNL contribution was significantly reduced to 1.0 +/- 0.2% (P < 0.01 relative to controls). In a separate study to determine the response of HTG to weaning from a high-fat diet, animals with raised HTG (3.33 +/- 0.51%) after 7 days of a high-fat diet reverted to basal HTG concentrations (0.76 +/- 0.06%) after an additional 7 days of weaning on a standard chow diet. These studies show that, in healthy rats, HTG concentrations are acutely influenced by dietary lipid concentrations. Although the DNL contribution to HTG content is suppressed by a high-fat diet in adult Sprague-Dawley rats, this effect is insufficient to prevent overall increases in HTG concentrations.

Tumor microenvironment of metastasis in human breast carcinoma: a potential prognostic marker linked to hematogenous dissemination

PURPOSE

Multiphoton-based intravital imaging has shown that invasive carcinoma cells in mouse and rat mammary tumors intravasate when associated with perivascular macrophages, identifying a potential tumor microenvironment of metastasis (TMEM). We define TMEM as the tripartite arrangement of an invasive carcinoma cell, a macrophage, and an endothelial cell. The aim of this study was to determine if TMEM density in human breast carcinoma samples predicts the development of systemic, hematogenous metastases.

EXPERIMENTAL DESIGN

A case-control study of 30 patients who developed metastatic breast cancer and 30 patients without metastatic disease was done. Cases were matched to controls based on currently used prognostic criteria. Paraffin-embedded primary breast cancer samples were stained using a triple immunohistochemical method allowing simultaneous identification of carcinoma cells, macrophages, and endothelial cells. Two pathologists, blinded to outcome, evaluated the number of TMEM per 20 high-power fields.

RESULTS

No association was seen between TMEM density and tumor size or grade, lymph node metastasis, lymphovascular invasion, or hormone receptor status. TMEM density was greater in the group of patients who developed systemic metastases compared with the patients with only localized breast cancer (median, 105 versus 50, respectively; P = 0.00006). For every 10-unit increase in TMEM density, the odds ratio for systemic metastasis was 1.9 (95% confidence interval, 1.1-3.4).

CONCLUSIONS

TMEM density predicted the development of systemic, hematogenous metastases. The ability of TMEM to predict distant metastasis was independent of lymph node status and other currently used prognosticators. Quantitation of TMEM may be a useful new prognostic marker for breast cancer patients.

Sources of endogenous glucose production in the Goto–Kakizaki diabetic rat

Plasma glucose, insulin and glucose tolerance were quantified in diabetic Goto-Kakizaki (GK) rats (342+/-45 g, n = 5) and compared with weight-matched non-diabetic Wistars (307+/-30 g, n = 8). Compared to Wistars, GK rats had higher fasting plasma insulin (219+/-50 versus 44+/-14 pmol/l, P<0.002) and glucose (9.2+/-2.3 versus 5.5+/-0.5 mmol/l, P<0.025). GK rats showed impaired glucose tolerance (IPGTT 2 h plasma glucose=14+/-1.5 versus 6.4+/-0.1 mmol/l, P<0.001). Endogenous glucose production (EGP) from glycogenolysis, phosphoenolpyruvate (PEP) and glycerol after 6 hours of fasting was quantified by a primed infusion of [U-(13)C]glucose and (2)H(2)O tracers and (2)H/(13)C NMR analysis of plasma glucose. EGP was higher in GK compared to Wistar rats (191+/-16 versus 104+/-27 mumol/kg per min, P<0.005). This was sustained by increased gluconeogenesis from PEP (85+/-12 versus 35+/-4 mumol/kg per min, P<0.02). Gluconeogenesis from glycerol was not different (20+/-3 in Wistar versus 30+/-6 mumol/kg per min for GK), and glycogenolysis fluxes were also not significantly different (76+/-23 mumol/kg per min for GK versus 52+/-19 mumol/kg per min for Wistar). The Cori cycle accounted for most of PEP gluconeogenesis in both Wistar and GK rats (85+/-15% and 77+/-10%, respectively). Therefore, increased gluconeogenesis in GK rats is largely sustained by increased Cori cycling while the maintenance of glycogenolysis indicates a failure in hepatic autoregulation of EGP.