Pathway-based signatures predict patient outcome, chemotherapy benefit and synthetic lethal dependencies in invasive lobular breast cancer

BACKGROUND

Invasive Lobular Carcinoma (ILC) is a morphologically distinct breast cancer subtype that represents up to 15% of all breast cancers. Compared to Invasive Breast Carcinoma of No Special Type (IBC-NST), ILCs exhibit poorer long-term outcome and a unique pattern of metastasis. Despite these differences, the systematic discovery of robust prognostic biomarkers and therapeutically actionable molecular pathways in ILC remains limited.

METHODS

Pathway-centric multivariable models using statistical machine learning were developed and tested in seven retrospective clinico-genomic cohorts (n = 996). Further external validation was performed using a new RNA-Seq clinical cohort of aggressive ILCs (n = 48).

RESULTS AND CONCLUSIONS

mRNA dysregulation scores of 25 pathways were strongly prognostic in ILC (FDR-adjusted P < 0.05). Of these, three pathways including Cell-cell communication, Innate immune system and Smooth muscle contraction were also independent predictors of chemotherapy response. To aggregate these findings, a multivariable machine learning predictor called PSILC was developed and successfully validated for predicting overall and metastasis-free survival in ILC. Integration of PSILC with CRISPR-Cas9 screening data from breast cancer cell lines revealed 16 candidate therapeutic targets that were synthetic lethal with high-risk ILCs. This study provides interpretable prognostic and predictive biomarkers of ILC which could serve as the starting points for targeted drug discovery for this disease.

Atlas of Lobular Breast Cancer Models: Challenges and Strategic Directions

Invasive lobular carcinoma (ILC) accounts for up to 15% of all breast cancer (BC) cases and responds well to endocrine treatment when estrogen receptor α-positive (ER+) yet differs in many biological aspects from other ER+ BC subtypes. Up to 30% of patients with ILC will develop late-onset metastatic disease up to ten years after initial tumor diagnosis and may experience failure of systemic therapy. Unfortunately, preclinical models to study ILC progression and predict the efficacy of novel therapeutics are scarce. Here, we review the current advances in ILC modeling, including cell lines and organotypic models, genetically engineered mouse models, and patient-derived xenografts. We also underscore four critical challenges that can be addressed using ILC models: drug resistance, lobular tumor microenvironment, tumor dormancy, and metastasis. Finally, we highlight the advantages of shared experimental ILC resources and provide essential considerations from the perspective of the European Lobular Breast Cancer Consortium (ELBCC), which is devoted to better understanding and translating the molecular cues that underpin ILC to clinical diagnosis and intervention. This review will guide investigators who are considering the implementation of ILC models in their research programs.

LMD-18. Detection and serial monitoring of CSF ctDNA in breast cancer leptomeningeal disease (BCLM)

Background

CSF cytology is the gold standard diagnostic test for BCLM, but is hampered by a low sensitivity, often necessitating repeated lumbar puncture to confirm or refute the diagnosis. Furthermore, during the treatment of BCLM, there is no robust quantitative response tool to guide treatment decisions.

Material and Methods

cfDNA was obtained from CSF and plasma in patients with breast cancer undergoing investigation for BCLM (n = 28) and during subsequent intrathecal treatment (n = 13). Ultra low pass whole genome sequencing (ulpWGS) and estimation of the ctDNA fraction was performed. Results were validated by mutation-specific digital droplet PCR (ddPCR).

Results

22/28 cases had confirmed BCLM by positive MRI and/or CSF cytology. The remaining 6/28 had suspected but non-confirmed BCLM, and at median 20 months follow up, these patients were BCLM-free.

CSF ctDNA fraction was significantly elevated (median 57.5, IQR 38.3 - 84.9%) in confirmed BCLM compared to 6 non-confirmed BCLM (median 5.0, IQR 0.0 - 6.7%) (p <0.0001). ctDNA fraction was detected in BCLM confirmed cases regardless of negative cytology or MRI. Plasma ctDNA fraction was only detected in extra-cranial disease progression. ctDNA fraction was concordant with mutant allele fraction measured by ddPCR (n = 118 samples).

Serial CSF ctDNA fraction during intrathecal treatment showed dynamic changes, while CSF cytology and MRI were often unchanged or equivocal. Early reduction in CSF ctDNA fraction was associated with longer responses to intrathecal therapy. Further, rising ctDNA fraction during intrathecal chemotherapy could be detected up to 6 weeks before relapse in neurological symptoms, cytology or MRI.

Conclusion

Measuring CSF ctDNA fraction is a sensitive diagnostic test for BCLM and could lead to more timely and accurate diagnosis. During intrathecal chemotherapy, CSF ctDNA also provides a quantitative response biomarker to help guide clinical management in this difficult treatment scenario.

Abstract LB246: E-cadherin loss drives Id2-dependent dampening of cell cycle progression and predicts increased susceptibility to CDK4/6 inhibition in lobular breast cancer

Invasive lobular breast carcinoma (ILC) is a low grade and mostly chemo-refractory luminal-type breast cancer that has been linked to sustained proliferative quiescence and long-term latency relapses (15-20 years). Loss of E-cadherin causes metastatic lobular breast cancer, partly through acquisition of anchorage independence. It is however still unknown how ILC cells control the balance between proliferative indolence and cell cycle re-entry at the metastatic site. We show here that E-cadherin loss leads to upregulation of Id2 through p120-catenin/Kaiso-dependent transcriptional derepression. Anchorage independent conditions further exacerbate p120-driven Id2 expression, leading to a sustained G0/G1 cell cycle arrest through binding of cytosolic Id2 to hypo-phosphorylated Rb. Intriguingly, we find that E-cadherin inactivation causes increased sensitivity to CDK4/6 inhibition in mouse and human breast cancer cell lines and primary tumor organoids. Finally, we find that Id2 expression is elevated in human ILC when compared to ductal breast cancers. Based on these data, we propose that combined E-cadherin loss and cytosolic Id2 expression can be used for the differential diagnosis of ILC and represent a candidate predictive biomarker pair for cell cycle targeting drug efficacy.

Citation Format: Max Antonius Klaus Rätze, Thijs Koorman, Thijmen Sijnesael, Blessing Bassey-Archibong, Robert van de Ven, Lotte Enserink, Daan Visser, Sridevi Jaksani, Elvira Bakker, François Richard, Andrew Tutt, Rebecca Steele, Stephen Pettitt, Christopher J. Lord, Amanda Fitzpatrick, Clare Isacke, Paul J. van Diest, Christine Desmedt, Juliet M. Daniel, Patrick W.B. Derksen. E-cadherin loss drives Id2-dependent dampening of cell cycle progression and predicts increased susceptibility to CDK4/6 inhibition in lobular breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB246.

Abstract PD13-03: Genomic profiling of breast cancer leptomeningeal metastasis (BCLM) reveals a divergent evolution and therapeutic targets

Background: Leptomeningeal metastasis remains a devastating development in breast cancer, with a median survival of 3-4 months, no widely accepted standard treatment, and limited access to trials of novel therapies. In addition, lack of access to leptomeningeal metastatic material hampers the pre-clinical investigation of the disease process and molecular drivers. This project uses CSF as a liquid biopsy to characterise BCLM, through genomic analysis of the cell-free DNA (cfDNA), and the development of pre-clinical BCLM models by the expansion of CSF disseminated tumour cells.

Methods: CSF (surplus to clinical requirements) and blood were collected from patients undergoing evaluation of leptomeningeal metastasis. cfDNA was extracted from CSF and plasma, and subjected to ultra-low pass whole genome sequencing (ulpWGS) to assess tumour-derived cfDNA fraction. Samples with &gt;10% tumour fraction underwent whole exome sequencing, along with matched archival primary tumour, archival extra-cranial metastatic site(s) and germline DNA. CSF cells were expanded in vitro (to establish 3D patient-derived organoids (PDOs).

Results: Cohort demographics are shown in Table 1. Whole exome sequencing (WES) in 21 patients reveals that 65.2% of variants found in CSF cfDNA were not shared with the primary tumour or other matched samples. Phylogenetic analysis shows a divergent evolution from extra-cranial metastatic sites, represented by plasma cfDNA (n = 12) and/or metastatic site tissue DNA (n = 7). The most frequently mutated cancer-associated genes in CSF were MUC16 (12/21), TP53 (11/21), CDH1 (10/21), and KMT2D (7/21). The common occurrence of CDH1 loss-of-function mutations was in keeping with the large number of lobular cases, however were also discovered in CSF of two cases with E-cadherin positive ductal primary tumours. Furthermore, mutations (including frameshift indels) in JAK family proteins (JAK1, JAK3 and TYK2) were present in 5/21 cases, and were private to CSF in 4/21. Potential actionable gene alterations private to CSF include; IDH2 (3/21), GLI1 (3/21), PIK3CA (2/21) and PTCH1 (2/21). Further, there was an enrichment for somatic BRCA1/2 mutations (5/21, 2 private to CSF) indicating potential for platinum and/or PARP inhibitor therapy in these individuals. Patient-derived organoids (PDOs) were established using CSF tumour cells from 3 ER+/HER2- and 2 TNBC BCLM cases. WES of PDOs revealed high concordance with genomic variants identified in the matched CSF cfDNA. Therapeutic compound testing revealed 3/5 PDOs did not display sensitivity to methotrexate, the most commonly used BCLM intrathecal treatment. Patient-derived xenograft (PDX) models have been established by mammary fat pad, intraductal, intracardiac and intracerebroventricular injection routes.

Conclusion/future plans: WES of CSF cfDNA provides insight into genomic changes in BCLM, including the divergent evolution, and BCLM specific alterations, some of which are potentially targetable. Parallel PDO and PDX models are being used to validate potential drivers and therapeutic targets. Treatment options beyond intrathecal methotrexate are urgently needed and in future might be molecularly tailored based on alterations discovered by CSF cfDNA sequencing.

Table 1. Clinical demographicsDemographicsMedian, years (range)Age at BC diagnosis45 (24 – 66)Time from primary BC to BCLM4.7 (0.7 – 14.7)Time from first metastasis to BCLM1.2 (0.0 – 6.5)Histological Typen (%)Lobular10 (48)Ductal8 (38)Mixed ductal/lobular3 (14)Immuno-histochemical phenotypen (%)ER+ HER2-13 (62)TNBC5 (24)ER+ HER2+2 (9)ER- HER2+1 (5)Metastatic sitesn (%)No other metastatic sites (BCLM only)3 (14)Bone12 (57)Serosal8 (38)Brain6 (29)Liver4 (19)Ovary4 (19)

Citation Format: Amanda Fitzpatrick, Marjan Iravani, Adam Mills, Eleanor Knight, Thanussuyah Alaguthurai, Vandna Shah, Alicia Okines, Nick Turner, Mark Harries, Syed Haider, Andrew Tutt, Clare Isacke. Genomic profiling of breast cancer leptomeningeal metastasis (BCLM) reveals a divergent evolution and therapeutic targets [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD13-03.

Abstract P1-19-04: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Fitzpatrick A, Isacke C, Tutt A. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-19-04.

INTEND II randomized clinical trial of intraoperative duct endoscopy in pathological nipple discharge

BACKGROUND

The majority of lesions resulting in pathological nipple discharge are benign. Conventional surgery is undirected and targeting the causative lesion by duct endoscopy may enable more accurate surgery with fewer complications.

METHODS

Patients requiring microdochectomy and/or major duct excision were randomized to duct endoscopy or no duct endoscopy before surgery. Primary endpoints were successful visualization of the pathological lesion in patients randomized to duct endoscopy, and a comparison of the causative pathology between the two groups. The secondary endpoint was to compare the specimen size between groups.

RESULTS

A total of 68 breasts were studied in 66 patients; there were 31 breasts in the duct endoscopy group and 37 in the no-endoscopy group. Median age was 49 (range 19-81) years. Follow-up was 5·4 (i.q.r. 3·3-8·9) years in the duct endoscopy group and 5·7 (3·1-9·0) years in no-endoscopy group. Duct endoscopy had a sensitivity of 80 (95 per cent c.i. 52 to 96) per cent, specificity of 71 (44 to 90) per cent, positive predictive value of 71 (44 to 90) per cent and negative predictive value of 80 (52 to 96) per cent in identifying any lesion. There was no difference in causative pathology between the groups. Median volume of the surgical resection specimen did not differ between groups.

CONCLUSION

Diagnostic duct endoscopy is useful for identifying causative lesions of nipple discharge. Duct endoscopy did not influence the pathological yield of benign or malignant diagnoses nor surgical resection volumes. Registered as INTEND II in CancerHelp UK clinical trials database (https://www.cancerresearchuk.org/about-cancer/find-a-clinical-trial/a-study-looking-at-changes-inside-the-breast-ducts-of-women-who-have-nipple-discharge).

Abstract LB-094: Suppression of inflammatory gene expression overcomes resistance to MEK inhibition in KRAS-mutant colorectal cancer

Despite showing clinical activity in BRAF-mutant melanoma, the MEK inhibitor (MEKi) trametinib failed to show clinical benefit in KRAS-mutant colorectal cancer. To identify mechanisms of resistance to MEK inhibition we identified gene expression differences between MEKi-sensitive and MEKi-resistant colorectal cancer cell lines. Strikingly, inflammation-related gene sets were the most significantly enriched in cell lines exhibiting intrinsic or acquired resistance to MEK inhibition. The bromodomain inhibitor JQ1 suppressed inflammatory gene expression and in combination with MEK inhibitors displayed synergistic anti-proliferative activity, inhibited colony formation and induced apoptosis in colorectal cancer cell lines. NFkB activation was greater in cell lines resistant to MEK inhibition and JQ1 treatment suppressed TNF-induced translocation of NFkB to the nucleus. Resistance to MEK inhibition could be induced by inflammatory cytokines or by conditioned medium from macrophage cultures and was associated with greater NFkB activation. In 2-dimensional cell culture and in 3-dimensional spheroid models of colorectal cancer, resistance to trametinib was readily established; however, co-treatment of cells with JQ1 and trametinib suppressed the emergence of resistant populations. Notably, high inflammatory gene expression was confirmed in patient-derived organoid (PDO) models of colorectal cancer, which displayed resistance to trametinib. JQ1 treatment of PDOs suppressed inflammatory gene expression and showed synergistic anti-proliferative activity in combination with trametinib. Combination treatment of in vivo models of KRAS-mutant colorectal cancer significantly suppressed tumor growth. Our findings provide a potential explanation for the limited response to MEK inhibitors in KRAS-mutant colorectal cancer, where a highly inflammatory environment may prime cells to be resistant to MEK inhibition. Moreover, the high expression of inflammatory genes was associated with significantly reduced survival of colorectal cancer patients. Excitingly, this opens novel therapeutic opportunities to overcome intrinsic and acquired resistance to MEK inhibition in colorectal cancer.

Citation Format: Steve Wagner, George Vlachogiannis, Alexis de Haven Brandon, Melanie Valenti, Gary Box, Liam Jenkins, Caterina Mancusi, Annette Self, Ritika Chauhan, Alistair Rust, Nik Matthews, Kate Eason, Anguraj Sadanandam, Clare Isacke, Vladimir Kirkin, Nicola Valeri, Steven R. Whittaker. Suppression of inflammatory gene expression overcomes resistance to MEK inhibition in KRAS-mutant colorectal cancer [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 LB-094.

Abstract SY21-03: Fibroblast recruitment and activation in breast cancer progression

The tumor microenvironment is characterized by the infiltration and activation of stromal cells and the establishment of reinforcing tumor-stroma crosstalk pathways. There is now strong evidence that these interactions not only promote tumor progression and metastasis, but also influence tumor cell responses to chemotherapy, endocrine therapy and targeted agents. As a consequence, there is an urgent need to identify strategies to efficiently target these crosstalk pathways for the prevention or suppression of metastatic disease and to overcome treatment-resistant tumor progression in advanced breast cancer.

Experimentally, the majority of studies characterizing fibroblast activation in tumors have compared CAFs to normal breast fibroblasts. Consequently, despite the recognition that individual breast cancers display a striking variation in fibroblast infiltration and composition, and that non-activated CAFs and activated CAFs can have distinct functional roles, the mechanisms underlying the tumor-fibroblast crosstalk that drive inter-tumor stromal heterogeneity remain poorly understood.

We have employed cell lines of the orthotopic 4T1 mammary carcinoma series, all of which form primary tumors but differ in their aggressiveness and metastatic potential. By immunohistochemical staining of the primary tumors and gene expression profiling of freshly isolated tumor fibroblasts we have demonstrated that fibroblast infiltration and activation correlate with tumor aggressiveness in this model. Conversely by profiling freshly isolated tumor cells, we identified Wnt7a as a key factor secreted exclusively by aggressive tumor cells that in both in vitro and in vivo models drives the recruitment and activation of stromal fibroblasts. Importantly, using two separate breast cancer patient cohorts, tumor cell Wnt7a expression significantly correlates with the presence of an activated stromal and is an independent prognostic marker of poor patient outcome. Functionally, Wnt7a promotes the fibroblasts' ability to remodel the extracellular matrix as a permissive environment for tumor cell invasion. Surprisingly, Wnt7a-dependent fibroblast activation is not mediated by canonical Wnt signaling, rather, Wnt7a acts to modulate TGFβ signaling. Crosstalk between TGFβ and Wnt signaling in both development and disease has been documented previously, however, the majority of reports have focused on the convergence of Wnt and TGFβ at the level of their respective downstream pathways. In contrast, our data support a model in which Wnt7a potentiates TGFβ receptor signaling and we suggest that a consequence of this is to drive increased autocrine TGFβ expression thus creating an autocrine loop to maintain an activated CAF phenotype.

In conclusion, this study demonstrates a key interaction between two of the major signaling pathways involved in both development and disease. Further, these data highlight a novel level of signaling interplay in tumor fibroblasts that could be exploited in stromally targeted therapies to complement the tumor-targeting regimes used to treat invasive cancers.

Current author addresses: Alexandra Avgustinova (Institute for Research in Biomedicine Barcelona, Spain), Pamela Klingbeil (Evotec AG, Hamburg, Germany).

Citation Format: Alexandra Avgustinova, Marjan Iravani, Fernando Calvo, Erik Sahai, Pamela Klingbeil, Clare Isacke. Fibroblast recruitment and activation in breast cancer progression. [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 SY21-03. doi:10.1158/1538-7445.AM2014-SY21-03

The mesenchymal stem cell marker CD248 (endosialin) is a negative regulator of bone formation in mice

OBJECTIVE

CD248 (tumor endothelial marker 1/endosialin) is found on stromal cells and is highly expressed during malignancy and inflammation. Studies have shown a reduction in inflammatory arthritis in CD248-knockout (CD248(-/-) ) mice. The aim of the present study was to investigate the functional effect of genetic deletion of CD248 on bone mass.

METHODS

Western blotting, polymerase chain reaction, and immunofluorescence were used to investigate the expression of CD248 in humans and mice. Micro-computed tomography and the 3-point bending test were used to measure bone parameters and mechanical properties of the tibiae of 10-week-old wild-type (WT) or CD248(-/-) mice. Human and mouse primary osteoblasts were cultured in medium containing 10 mM β-glycerophosphate and 50 μg/ml ascorbic acid to induce mineralization, and then treated with platelet-derived growth factor BB (PDGF-BB). The mineral apposition rate in vivo was calculated by identifying newly formed bone via calcein labeling.

RESULTS

Expression of CD248 was seen in human and mouse osteoblasts, but not osteoclasts. CD248(-/-) mouse tibiae had higher bone mass and superior mechanical properties (increased load required to cause fracture) compared to WT mice. Primary osteoblasts from CD248(-/-) mice induced increased mineralization in vitro and produced increased bone over 7 days in vivo. There was no decrease in bone mineralization and no increase in proliferation of osteoblasts in response to stimulation with PDGF-BB, which could be attributed to a defect in PDGF signal transduction in the CD248(-/-) mice.

CONCLUSION

There is an unmet clinical need to address rheumatoid arthritis-associated bone loss. Genetic deletion of CD248 in mice results in high bone mass due to increased osteoblast-mediated bone formation, suggesting that targeting CD248 in rheumatoid arthritis may have the effect of increasing bone mass in addition to the previously reported effect of reducing inflammation.

Abstract P5-05-02: Whole Genome In Vivo RNA Interference Screening Identifies the Leukemia Inhibitory Factor Receptor as a Novel Breast Tumor Suppressor

Background: Cancer is caused by mutations in oncogenes and tumor suppressor genes resulting in the deregulation of processes fundamental to the normal behavior of cells. The identification and characterization of oncogenes and tumor suppressors has led to new treatment strategies that have significantly improved cancer outcome. The advent of next generation sequencing has allowed the elucidation of the fine structure of cancer genomes, however, the identification of pathogenic changes is complicated by the inherent genomic instability of cancer cells. Therefore, functional approaches for the identification of novel genes involved in the initiation and development of tumors are critical. Methods: In order to identify functionally important tumor suppressor genes we have conducted the first human whole genome in vivo RNA interference (RNAi) screen. Partially transformed human mammary epithelial cells (HMLEs), which do not form tumors in immunodeficient mice, were infected with the Expression Arrest™ GIPZ lentiviral shRNA library consisting of 62,000 shRNAs targeting the whole human genome, and injected into the mammary fat pad of immunodeficient mice. shRNAs that silenced tumor suppressor genes fully transformed the mammary epithelial cells resulting in tumor formation. Candidate tumor suppressor genes were identified by PCR amplification and sequencing of tumor integrated shRNAs. For validation, candidate tumor suppressor genes were silenced in HMLEs and ectopically expressed in fully transformed breast cancer cells. The effect of modifying gene expression on the transformed phenotype was assessed using soft agar colony formation assays. Clinical significance was determined by comparing expression in normal and cancerous human breast tissue using Oncomine Research. Results and Discussion: Using our novel approach, we identify previously validated tumor suppressor genes including TP53 and MNT, as well as several novel candidate tumor suppressor genes including leukemia inhibitory factor receptor (LIFR). Silencing LIFR expression with multiple shRNA constructs fully transformed human mammary epithelial cells resulting in enhanced colony formation in soft agar (P&lt;0.05). Furthermore, overexpression of LIFR significantly inhibited colony formation in soft agar of fully transformed MDA231 and MCF7 breast cancer cells (P&lt;0.01). In addition, our analysis of clinical data revealed that LIFR expression is significantly decreased in a large percentage of human cancers including breast (P&lt;0.0001), lung (P&lt;0.0001), hepatocellular (P&lt;0.0001) and gastrointestinal tumors (P&lt;0.0001). These results validate LIFR as a previously unidentified highly significant tumor suppressor, and also demonstrate the power of whole genome in vivo RNAi screens as a method for identifying novel genes regulating tumorigenesis.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-05-02.

A surgically induced hypoxic environment causes changes in the metastatic behaviour of tumours in vitro

The use of laparoscopic techniques for curative resections of malignant tumours has been under scrutiny. The potential benefits to the patient in the form of earlier recovery and less immune paresis are countered by the reports of increased tumour recurrence. The biological sequelae of the hypoxic laparoscopic environment on tumour cells is unknown. Components of the metastatic cascade were evaluated under in vitro laparoscopic conditions using a human colonic adenocarcinoma cell line (SW1222). Exposure to the laparoscopic gases carbon dioxide and helium for 4 h, comparable to the duration of a laparoscopic colorectal resection, had no effect on cell viability. A cellular hypoxic insult was demonstrated by the induction of hypoxia inducible factor 1alpha (HIF-1alpha). Exposure also resulted in significant reduction in homotypic adhesion as well as to a variety of extracellular matrix components. These effects were recoverable under re-oxygenation. The changes were reflected at the molecular level by significant down regulation of adhesion molecules known to be involved in tumour progression (E-cadherin, CD44 and beta1 sub-unit). Modulation of adherence has significant implications for laparoscopic oncological surgery, demonstrating that tumours become potentially more friable and easier to disseminate in surgeons who are less experienced or where instrumentation is sub-optimal.

CD molecules 2005: human cell differentiation molecules

The immune system works through leukocytes interacting with each other, with other cells, with tissue matrices, with infectious agents, and with other antigens. These interactions are mediated by cell-surface glycoproteins and glycolipids. Antibodies against these leukocyte molecules have provided powerful tools for analysis of their structure, function, and distribution. Antibodies have been used widely in hematology, immunology, and pathology, and in research, diagnosis, and therapy. The associated CD nomenclature is commonly used when referring to leukocyte surface molecules and antibodies against them. It provides an essential classification for diagnostic and therapeutic purposes. The most recent (8th) Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA), held in Adelaide, Australia, in December 2004, allocated 95 new CD designations and made radical changes to its aims and future operational strategy in order to maintain its relevance to modern human biology and clinical practice.

The NF2 tumor suppressor gene product, merlin, mediates contact inhibition of growth through interactions with CD44

The neurofibromatosis-2 (NF2) gene encodes merlin, an ezrin-radixin-moesin-(ERM)-related protein that functions as a tumor suppressor. We found that merlin mediates contact inhibition of growth through signals from the extracellular matrix. At high cell density, merlin becomes hypo-phosphorylated and inhibits cell growth in response to hyaluronate (HA), a mucopolysaccharide that surrounds cells. Merlin's growth-inhibitory activity depends on specific interaction with the cytoplasmic tail of CD44, a transmembrane HA receptor. At low cell density, merlin is phosphorylated, growth permissive, and exists in a complex with ezrin, moesin, and CD44. These data indicate that merlin and CD44 form a molecular switch that specifies cell growth arrest or proliferation.

Discrete domains within the hyaluronan receptor CD44 regulate membrane localization and cell migration

CD44 is the principle transmembrane receptor for the extracellular matrix glycosaminoglycan, hyaluronan. This receptor: ligand interaction is required for many normal cellular processes including lymphocyte homing into inflammatory sites, assembly of a pericellular matrix during chondrogenesis, wound healing and tissue morphogenesis during development. In order to mediate these diverse events, CD44 expressing cells must be able to regulate, and respond to, interactions with hyaluronan. The mechanisms responsible have been subject to scrutiny over the past few years as it has become clear that their disruption can underlie the progression of both metastatic tumours and chronic inflammatory diseases. Here we describe recent data identifying discrete regions within the transmembrane and cytoplasmic domains of CD44 which regulate this important adhesion receptor.