Anticancer innovative therapy: Highlights from the ninth annual meeting

The Ninth Annual Conference of "Anticancer Innovative Therapy", organized by Fondazione IRCCS Istituto Nazionale dei Tumori di Milano (Fondazione IRCCS INT) and hosted by Hotel Michelangelo, was held in Milan on 25 January 2019. Cutting-edge science was presented in two main scientific sessions: i) pre-clinical evidences and new targets, and ii) clinical translation. The Keynote lecture entitled "Cancer stem cells (CSCs): metabolic strategies for their identification and eradication" presented by M. Lisanti, was one of the highlights of the conference. One key concept of the meeting was how the continuous advances in our knowledge about molecular mechanisms in various fields of research (cancer metabolism reprogramming, epigenetic regulation, transformation/invasiveness, and immunology, among others) are driving cancer research towards more effective personalized antineoplastic strategies. Specifically, recent preclinical data on the following topics were discussed: 1. Polycomb group proteins in cancer; 2. A d16HER2 splice variant is a flag of HER2 addiction across HER2-positive cancers; 3. Studying chromatin as a nexus between translational and basic research; 4. Metabolomic analysis in cancer patients; 5. CDK4-6 cyclin inhibitors: clinical activity and future perspectives as immunotherapy adjuvant; and 6. Cancer stem cells (CSCs): metabolic strategies for their identification and eradication. In terms of clinical translation, several novel approaches were presented: 1. Developing CAR-T cell therapies: an update of preclinical and clinical development at University of North Carolina; 2. Vγ9Vδ2 T-cell activation and immune suppression in multiple myeloma; 3. Predictive biomarkers for real-world immunotherapy: the cancer immunogram model in the clinical arena; and 4. Mechanisms of resistance to immune checkpoint blockade in solid tumors. Overall, the pre-clinical and clinical findings presented could pave the way to identify novel actionable therapeutic targets to significantly enhance the care of persons with cancer.

Constraints on Sub-GeV Dark-Matter-Electron Scattering from the DarkSide-50 Experiment

We present new constraints on sub-GeV dark-matter particles scattering off electrons based on 6780.0 kg d of data collected with the DarkSide-50 dual-phase argon time projection chamber. This analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. The detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 keVee. We calculate the expected recoil spectra for dark matter-electron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from XENON10 for dark-matter particles with masses between 30 and 100  MeV/c^{2}.

Low-Mass Dark Matter Search with the DarkSide-50 Experiment

We present the results of a search for dark matter weakly interacting massive particles (WIMPs) in the mass range below 20  GeV/c^{2} using a target of low-radioactivity argon with a 6786.0 kg d exposure. The data were obtained using the DarkSide-50 apparatus at Laboratori Nazionali del Gran Sasso. The analysis is based on the ionization signal, for which the DarkSide-50 time projection chamber is fully efficient at 0.1  keVee. The observed rate in the detector at 0.5  keVee is about 1.5  event/keVee/kg/d and is almost entirely accounted for by known background sources. We obtain a 90% C.L. exclusion limit above 1.8  GeV/c^{2} for the spin-independent cross section of dark matter WIMPs on nucleons, extending the exclusion region for dark matter below previous limits in the range 1.8-6  GeV/c^{2}.

Compressive Femoral Neuropathy Associated with Iliopsoas Hematoma Complicating Hip Hemiarthroplasty: A Case Report

Introduction

Femoral nerve compression caused by iliopsoas hematoma is a rare complication after hip surgery. To the best of our knowledge, this is the first case after hemiarthroplasty. In this case, iliacus hematoma resulted from spontaneous bleeding favored by anticoagulant therapy.

Case Report

A 78-year-old female developed left groin pain associated with typical symptoms of femoral nerve palsy about 2weeks after left hip hemiarthroplasty[1, 2, 3]. Computed tomography revealed the presence of a left iliopsoas hematoma that was surgically drained. Inguinal pain was immediately relieved, while nerve palsy recovered only partially, but the quality of life drastically improved and she was able to walk using a walker without pain.

Conclusion

Even if it is a rare condition, the formation of a hematoma of iliopsoas muscle should be considered in patients that present symptoms of femoral nerve palsy, especially if treated with heparin or other anticoagulant drugs. Surgical drainage of the hematoma is indicated when symptoms are severe and disabling, and in this way, surgery could improve quality of life.

ESPEN expert group recommendations for action against cancer-related malnutrition

Patients with cancer are at particularly high risk for malnutrition because both the disease and its treatments threaten their nutritional status. Yet cancer-related nutritional risk is sometimes overlooked or under-treated by clinicians, patients, and their families. The European Society for Clinical Nutrition and Metabolism (ESPEN) recently published evidence-based guidelines for nutritional care in patients with cancer. In further support of these guidelines, an ESPEN oncology expert group met for a Cancer and Nutrition Workshop in Berlin on October 24 and 25, 2016. The group examined the causes and consequences of cancer-related malnutrition, reviewed treatment approaches currently available, and built the rationale and impetus for clinicians involved with care of patients with cancer to take actions that facilitate nutrition support in practice. The content of this position paper is based on presentations and discussions at the Berlin meeting. The expert group emphasized 3 key steps to update nutritional care for people with cancer: (1) screen all patients with cancer for nutritional risk early in the course of their care, regardless of body mass index and weight history; (2) expand nutrition-related assessment practices to include measures of anorexia, body composition, inflammatory biomarkers, resting energy expenditure, and physical function; (3) use multimodal nutritional interventions with individualized plans, including care focused on increasing nutritional intake, lessening inflammation and hypermetabolic stress, and increasing physical activity.

The correlation between preoperative levels of albumin and tlc and mortality in patients with femoral neck fracture

A femoral neck fracture in an elderly patient often represents a major challenge for the orthopaedic surgeon who has to face not only the fracture, but also all the multiple issues related to age. Among others, malnutrition has been recognised as an important factor associated with severe aggravation in these patients. One-hundred-and-forty-seven patients were enrolled to investigate the use of two markers of patient nutritional status, i.e. serum albumin level and total leukocyte count (TLC), as predictors of mortality in the elderly patient suffering from proximal femur fracture. We found that low preoperative values of serum albumin and TLC proved to be directly related to worse outcomes. Therefore, these exams can be useful to identify patients with a femoral neck fracture that have higher risk of malnutrition and consequent higher mortality and that can benefit from some measures, such as albumin or protein nutritional supplement.

Abstract ES2-3: Metabolic asymmetry in breast cancer: Implications for personlised medicine

Over the last decade, strong evidence has accumulated that the tumor micro-environment plays a key role in recurrence, metastasis and poor clinical outcome in breast cancer patients. In this context, more recent discoveries indicate that catabolic cancer-associated fibroblasts (CAFs) produce nutrients (lactate, ketone bodies and glutamine) to fuel anabolic mitochondrial metabolism in cancer cells. This new paradigm is known as metabolic-symbiosis or metabolic asymmetry and reflects the co-existence of multiple metabolic compartments in a given tumor. This type of metabolic co-operation in the tumor ecosystem underlies the metabolic heterogeneity found in human breast cancers, and can be used to more effectively predict tumor recurrence, metastasis, drug-resistance and poor clinical outcome, in breast cancer patients.

In my talk, I will highlight how this metabolic-symbiosis phenotype could be targeted from a therapeutic point of view, bringing us closer to the goal of personalized medicine.

For further information on this topic, please see the following references:

Caveolae and signalling in cancer.

Martinez-Outschoorn UE, Sotgia F, Lisanti MP.

Nat Rev Cancer. 2015 Apr;15(4):225-37.

Metabolic asymmetry in cancer: A balancing act that promotes tumor growth.

Martinez-Outschoorn UE, Sotgia F, Lisanti MP.

Cancer Cell. 2014 Jul 14;26(1):5-7.

Power surge: Supporting cells fuel cancer cell mitochondria.

Martinez-Outschoorn UE, Sotgia F, Lisanti MP.

Cell Metab. 2012 Jan 4;15(1):4-5.

Citation Format: Lisanti MP. Metabolic asymmetry in breast cancer: Implications for personlised medicine. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr ES2-3.

Abstract BS3-2: Targeting mitochrondria with FDA-approved antibiotics may be a new therapeutic strategy to eliminate cancer stem cells

Our recent studies indicate that cancer stem cells (CSCs) have increased mitochondrial mass, which directly reflects an increase in mitochondrial biogenesis and OXPHOS capacity. Thus, we believe that more effective anti-cancer therapy would involve the strategic targeting of CSC mitochondria, to prevent or reverse tumor recurrence, metastasis and drug-resistance. Interestingly, mitochondria are originally derived from aerobic bacteria that were engulfed by eukaryotic cells and adapted over millions of years of evolution. This is known as the 'Endo-symbiotic Theory of Mitochondrial Evolution'. As a consequence, certain antibiotics target mitochondrial protein translation as a manageable side effect. We have recently proposed to harness this side effect and to re-purpose it as a therapeutic effect to target breast CSCs. In accordance with this strategy, we have already experimentally identified 4 to 5 different class of mitochondrial-targeted antibiotics that could be used halt the proliferation and eradicate breast CSCs. These antibiotics included azithromycin and doxycycline, among others. Importantly, these antibiotics showed anti-CSC activity in 12 different cell lines, across 8 different cancer types, that were originally derived from breast, DCIS, ovarian, prostate, pancreatic and lung carcinomas, as well as glioblastoma and melanoma. In this context, doxycycline appeared to be one of the most promising agents, as human clinical trials in MALT lymphoma have already shown very positive results. Similarly, clinical trials with azithromycin in lung cancer patients have also shown positive results. Thus, targeting mitochondrial protein translation, with FDA-approved antibiotics, may be a safe effective strategy for inhibiting mitochondrial function in CSCs, regardless of the tumor type or site of origin.

For further information on this topic, please see the following references:

Antibiotics that target mitochondria effectively eradicate cancer stem cells, across multiple tumor types: Treating cancer like an infectious disease. Lamb R, Ozsvari B, Lisanti CL, Tanowitz HB, Howell A, Martinez-Outschoorn UE, Sotgia F, Lisanti MP. Oncotarget. 2015 Mar 10;6(7):4569-84.

Drug therapy: Can the mitochondrial adverse effects of antibiotics be exploited to target cancer metabolism? Killock D. Nat Rev Clin Oncol. 2015 Apr;12(4):190.

High mitochondrial mass identifies a sub-population of stem-like cancer cells that are chemo-resistant. Farnie G, Sotgia F, Lisanti MP. Oncotarget. 2015 Sep 30. [Epub ahead of print] PMID: 26421710

http://www.ncbi.nlm.nih.gov/pubmed/26421710

Mitochondrial mass, a new metabolic biomarker for stem-like cancer cells: Understanding WNT/FGF-driven anabolic signaling. Lamb R, Bonuccelli G, Ozsvari B, Peiris-Pages M, Fiorillo M, Smith DL, Bevilacqua G, Mazzanti CM, McDonnell LA, Naccarato AG, Chiu M, Wynne L, Martinez-Outschoorn UE, Sotgia F, Lisanti MP. Oncotarget. 2015 Sep 28. [Epub ahead of print] PMID: 26421711

http://www.ncbi.nlm.nih.gov/pubmed/26421711

Citation Format: Lisanti MP. Targeting mitochrondria with FDA-approved antibiotics may be a new therapeutic strategy to eliminate cancer stem cells. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr BS3-2.

Short femoral stem and porous titanium: winning combination?

A lot of different implants are available in hip replacement arthroplasty (THA), stems differ mainly by type of fixation, material, length, diameter, shape, surface coating, modularity, etc. The main quality of a non-cemented stem is to pursuit primary and secondary stability, to preserve bone stock, to be adaptable and modular. The literature shows that the most popular non cemented stems used in THA are metaphyseal femoral stem in which the distal portion has only the action to avoid varus stem placement but can also be a source of complications such as stress shielding. The stability of a short stem is closely dependent on material that must allow a high "scratch fit" and facilitate osteointegration with a generous surface of bone-implant contact. From September 2010 we have performed 287 THA using a modular titanium porous short stem. The article shows the preliminary results, which are very encouraging, showing excellent primary and secondary osteointegration, also slightly undersized implants or in elderly porotic patients.

Abstract P5-07-06: Kinase-independent role of cyclin D1 in chromosomal instability and mammary tumorigenesis

Cyclin D1 is an important molecular driver of human breast cancer but better understanding of its oncogenic mechanisms is needed, especially to enhance efforts in targeted therapeutics. Activation of the cyclin D1 oncogene, often by amplification or rearrangement, is a major driver of multiple types of human tumors including breast and squamous cell cancers, B-cell lymphoma, myeloma, and parathyroid adenoma. The cyclin D1 gene is amplified or overexpressed in up to half of human breast cancers and its mammary-targeted overexpression induces mammary tumorigenesis in mice. Cyclin D1 encodes the regulatory subunit of the cyclin-dependent kinase (CDK) holoenzyme that phosphorylates several substrates including the retinoblastoma protein (pRb) to advance the G1S cell cycle checkpoint, promote DNA synthesis and regulate NRF-1 to inhibit mitochondrial biogenesis thereby coordinating nuclear and mitochondrial functions.

In addition to cyclin D1's function as a regulatory subunit of a CDK holoenzyme, several CDK-independent functions have been identified. Tumors overexpressing cyclin D1 tend to display normal levels of proliferation and expression of E2F target genes, which contrasts with tumors overexpressing cyclin E or an activator for pRb. Breast cancers overexpressing cyclin D1 that are wild type for pRb have relatively normal proliferation rates, in contrast to those caused by genetic inactivation of pRb, which show significantly increased proliferation rates. Furthermore, the alternate splice form of cyclin D1, (cyclin D1b), has potent transforming ability, which does not correlate with the ability to phosphorylate the pRb protein. Several other properties of cyclin D1 have been identified including the induction of cellular migration and enhanced angiogenesis, inhibition of mitochondrial biogenesis, and mediating DNA-damage repair signaling. Cyclin D1 binding proteins participating in these putatively CDK-independent functions include PACSIN2, NRF1, and p27KIP1; binding to p27KIP1 and PACSIN2 contribute to the pro-migratory function of cyclin D1.

Currently, pharmaceutical initiatives to inhibit cyclin D1 are focused on the catalytic component since the transforming capacity is thought to reside in the cyclin D1/CDK activity. We initiated the following study to directly test the oncogenic potential of catalytically inactive cyclin D1 in an in vivo mouse model that is relevant to breast cancer. Herein, transduction of cyclin D1-/- mouse embryonic fibroblasts (MEFs) with the kinase dead KE mutant of cyclin D1 led to aneuploidy, abnormalities in mitotic spindle formation, autosome amplification, and chromosomal instability (CIN) by gene expression profiling. Acute transgenic expression of either cyclin D1WT or cyclin D1KE in the mammary gland was sufficient to induce the CIN signature within 7 days. Sustained expression of cyclin D1KE induced mammary adenocarcinoma with similar kinetics to that of the wild-type cyclin D1. ChIP-Seq studies demonstrated recruitment of cyclin D1WT and cyclin D1KE to the genes governing CIN. We conclude that the CDK-activating function of cyclin D1 is not necessary to induce either chromosomal instability or mammary tumorigenesis.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-07-06.

Abstract P1-07-05: The cell fate factor DACH1 represses YB-1-mediated oncogenic transcription and translation

The epithelial-mesenchymal transition (EMT) enhances cellular invasiveness and confers tumor cells with cancer stem cell like characteristics, through transcriptional and translational mechanisms. The mechanisms maintaining transcriptional and translational repression of EMT and cellular invasion are poorly understood. The Drosophila homologue of DACH1, the Dac gene is a key member of the retinal determination gene network that specifies organismal development. The dachshund (dac), eya1, eyes-absent (eya), twin of eyeless (toy), teashirt (tsh) and sinoculues (so) are expressed in progenitor cells, contributing to development of the eye and genitalia. Loss of DACH1 expression contributes to the expansion of neural progenitors, muscle satellite cell differentiation and breast cancer stem cells. In recent studies Dachshund repressed breast cancer stem cell expansion. DACH1 expression is reduced in a variety of human cancers including prostate, ovarian and human breast cancer.

Herein, the cell fate-determination factor Dachshund (DACH1), suppressed EMT via repression of cytoplasmic translational induction of Snail by inactivating the Y box-binding protein (YB-1). In the nucleus, DACH1 antagonized YB-1-mediated oncogenic transcriptional modules governing cell invasion. DACH1 blocked YB-1-induced mammary tumor growth and EMT in mice. In basal-like breast cancer (BLBC) the reduced expression of DACH1 and increased YB-1, correlated with poor metastasis free survival. The loss of DACH1 suppression of both cytoplasmic translational and nuclear transcriptional events governing EMT and tumor invasion may contribute to poor prognosis in BLBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-07-05.

Abstract P2-06-02: Pparg deacetylation by SIRT1 determines breast tumor lipid synthesis and growth

Peroxisome proliferator-activated receptorg (Pparγ) is a member of the nuclear receptor (NR) superfamily, which regulates diverse biological functions including lipogenesis and differentiation, anti-inflammation, insulin sensitivity, cellular proliferation, and autophagy. Independent lines of evidence support a role for Pparγ as either a collaborative oncogene or as a tumor suppressor. Heterozygous mutations of Pparγ have been detected in 4/55 patients with colon cancer and a chromosomal translocation between PAX8 and Pparγ in follicular thyroid cancer appeared to serve as a dominant inhibitor of endogenous Pparγ expression. Pparγ agonists reduced tumorigenesis in several in vivo models. In contrast, several studies suggest Pparγ may enhance tumor growth. Pparγ ligands increased polyp numbers in the Apc mouse model of familial adenomatosis. Pparγ and its ligands inhibit breast tumor growth; however, constitutively active Pparγ collaborated in mammary oncogenesis with polyoma middle T antigen or oncogenic ErbB2.

Pparγ activation involves post-translational modifications including phosphorylation and sumoylation upon growth factor or ligand stimulus. Mutation of the Pparγ1 sumoylation site at K77 and K365 demonstrated that K77 may either reduce Pparγ-dependent gene induction and enhance repression or reduce repression, depending upon the synthetic reporter gene used. Lysine residues of nuclear receptors also serve as substrates for acetylation and Pparγ binds co-activators and co-repressors with intrinsic or associated histone acetylase or deacetylase activity including NCoR, SMRT, SIRT1, and p300. Initially characterized for the ERα, AR and, subsequently, the orphan nuclear receptor steroidogenic factor 1 (SF-1), acetylation occurs at a conserved lysine motif shared amongst evolutionarily related nuclear receptors. Several nuclear receptors and co-integrators involved in lipid metabolism are regulated by acetylation including p300, PGC1α, FXR, LXR and RAR. Both TSA- and NAD-sensitive HDACs (e.g. SIRT1) regulate Pparγ function and SIRT1 inhibits Pparγ-dependent adipocyte differentiation. Whether Pparγ is acetylated in cancer cells and how Pparγ exerts it's crucial, though controversial, function in tumorigenesis have not been established.

Pparγ induces gene transcription through binding specific NR half-sites and through non-canonical binding sequences (such as CREB/AP-1 sites). Transcriptional repression involves Pparγ sumoylation at lysine 77 (K77). Herein, Pparγ was shown to be acetylated at nine distinct lysine residues. SIRT1 bound and deacetylated Pparγ at K154/155. ChIP-Seq analysis for genome-wide DNA binding demonstrated the acetylation site was required for binding NR half-sites, but was not required for non-canonical site binding. Breast tumor growth, de novo lipid synthesis, induction of autophagy and evasion of apoptosis was promoted by K154/155 and inhibited by K77 in vivo. Pparγ acetylation induced a gene signature that was increased in breast cancer, associated with a reduction in SIRT1 abundance and poor outcome. The Pparγ acetylation site determines binding to autophagy and apoptosis signaling to regulate breast tumor lipid metabolism and growth.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-06-02.

Abstract P5-11-04: Post-translational modification of the cell-fate factor Dachshund determines p53 binding and signaling modules in breast cancer

Breast cancer is a leading form of cancer in the world. Initially cloned as a dominant inhibitor of the hyperactive EGFR, Ellipse, in Drosophila, the mammalian DACH1 regulates expression of target genes in part through interacting with DNA-binding transcription factors (c-Jun, Smads, Six, ERα), and in part through intrinsic DNA-sequence specific binding to Forkhead binding sites. The Drosophila dac gene is a key member of the retinal determination gene network (RDGN), which also includes eyes absent (eya), ey, twin of eyeless (toy), teashirt (tsh) and sin oculis (so), that specifies eye tissue identity.

Several lines of evidence suggest DACH1 may function as a tumor suppressor. Clinical studies have demonstrated a correlation between poor prognosis and reduced expression of the cell-fate determination factor DACH1 in breast cancer, and loss of DACH1 expression has been observed in prostate and endometrial cancer. DACH1 inhibits breast cancer tumor metastasis and reduces breast cancer stem cell expansion via Sox2/Nanog. Although these studies suggest DACH1 may function as a tumor suppressor, the molecular mechanisms remain poorly defined. Herein, endogenous DACH1 co-localized with p53 in a nuclear, extranucleolar compartment and bound to p53 in human breast cancer cell lines, p53 and DACH1 bound common genes in ChIP-Seq. Full inhibition of breast cancer contact-independent growth by DACH1 required p53. The p53 breast cancer mutants R248Q and R273H, evaded DACH1 binding. DACH1 phosphorylation at serine residue (S439) inhibited p53 binding and phosphorylation at p53 amino-terminal sites (S15, S20) enhanced DACH1 binding. DACH1 binding to p53 was inhibited by NAD-dependent deacetylation via DACH1 K628. DACH1 repressed p21CIP1 and induced RAD51, an association found in basal breast cancer. DACH1 inhibits breast cancer cellular growth in an NAD and p53 dependent manner through direct protein-protein association.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-11-04.

Comparison of the POSSUM score and P-POSSUM score in patients with femoral neck fracture

PURPOSE

The ageing of the population in developed countries has led to an increased number of patients with hip fractures all over the world. POSSUM and P-POSSUM scores predict morbidity and mortality of patients who will be undergoing a surgical treatment. The aim of this study was to evaluate accuracy of these two scores in hip-fractured patients.

MATERIALS AND METHODS

Between January and December 2012, in our department 144 patients were hospitalised for femoral neck fractures according to the grade III or IV of Garden's classification treated with total hip arthroplasty or endoprosthesis. POSSUM scores and P-POSSUM scores were calculated for each patient with complete clinical data. We then calculated the observed and the expected ratio.

RESULTS

134 patients were eligible: 110 females and 24 males. The mean age for women was 79 years, and the mean age for men was 84 years. We observed 13 deaths and 66 complications. The POSSUM scores predicted 16 deaths and 60 complications, while P-POSSUM scores predicted 6 deaths. The O/E ratio for POSSUM mortality was 0.81 and for P-POSSUM was 2.17, while POSSUM morbidity was 1.1.

CONCLUSION

In our study, we have shown that on the one hand, the POSSUM score predicted accurately both the mortality and morbidity in patients undergoing surgery for the femoral neck fracture, while on the other hand, the P-POSSUM score underestimated them. For this reason, we believe that the POSSUM is indeed a good audit tool, which can accurately predict both mortality and morbidity in a cohort of patients.

An optimal design for patient-specific templates for pedicle spine screws placement

BACKGROUND

Currently, pedicle screws are positioned using a free-hand technique or under fluoroscopic guidance, with error in the range 10-40%, depending on the skill of the surgeon.

METHODS

After spine CT acquisition, each vertebra is segmented and the surgeon plans screw positioning in a virtual environment, then the template is designed around the chosen trajectories. This design is based on surgical and mechanical considerations to obtain an optimal solution to guarantee template stability, simple positioning and minimized intervention invasiveness. In vitro evaluation on synthetic spine models and ex vivo animal tests on porcine specimens were performed, with the insertion of 28 Kirschner wires.

RESULTS

During the in vitro tests, all the surgeons rendered positive evaluations regarding the device and considered template placement to be easy. Ex vivo tests were evaluated by CT examination, which showed that 96.5% of the Kirschner wires had been correctly inserted.

CONCLUSIONS

The proposed solution is a promising, simple, highly precise, low-cost solution to safely performing posterior stabilization. Such a solution would be of interest even in hospitals in which a few spine interventions are performed per year, and for which it is not reasonable to purchase the equipment required for robotic or navigated approaches.

Abstract P4-01-04: The Impact of the Retinoblastoma Tumor Suppressor Pathway in Her2 Positive Breast Cancer Pathogenesis and Therapeutic Response

Extensive studies have shown that breast cancer is associated with molecular aberrations that underlie the distinct subtypes of disease that exhibit differential prognosis and susceptibility to targeted therapeutic. A critical oncogenic event used to classify breast cancers is the amplification or overexpression of the human epidermal growth factor receptor 2 (Her2). Tumors harboring Her2 overexpression present aggressive characteristics related to metastatic spread and poor overall disease outcome. However, such tumors are also susceptible to targeted therapeutic agents which effectively impinge on this oncogene. Strikingly, those events that cooperate with Her2 and modulate susceptibility to targeted therapeutics remain poorly understood. Here the significance of the retinoblastoma tumor suppressor (RB) pathway in the context of Her2 positive breast cancer pathogenesis and therapeutic response was evaluated. In silico and histological analyses suggested that a subset of Her2 positive tumors exhibit compromised RB function. To model interactions between Her2 and the RB-pathway genetic deletion and knockdown strategies were employed in the context of Her2 driven tumors. These studies revealed that RB loss accelerated disease progression of such models and further enhanced the aggressive tumor phenotype.

To delineate the functionality of the RB-pathway downstream from therapeutic interventions targeting Her2, two complimentary approaches were used. First, the ability to effectively intercede in Her2-positive tumors using drugs that specifically activate the RB-pathway was interrogated. The data revealed that specific CDK4/6 targeted therapies were highly effective at limiting the growth of Her2-positive tumor cells. Second, the impact of RB status on the response the Her2/EGFR antagonist lapatinib was evaluated. These studies demonstrated that loss of RB compromises the effectiveness of lapatinib in the treatment of Her2 positive breast cancer cell lines. Ongoing studies are evaluating the spontaneous mechanisms of resistance to Her2 targeted therapeutics and the significance of reestablishing RB function as a therapeutic alternative in such cancers. Together, these studies underscore the importance of the interplay between Her2 signaling and cell cycle control in breast cancer, and how this crosstalk influences the response to targeted therapeutics in the treatment of breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-01-04.

Postobstructive regeneration of kidney is derailed when surge in renal stem cells during course of unilateral ureteral obstruction is halted

Unilateral ureteral obstruction (UUO), a model of tubulointerstitial scarring (TIS), has a propensity toward regeneration of renal parenchyma after release of obstruction (RUUO). No information exists on the contribution of stem cells to this process. We performed UUO in FVB/N mice, reversed it after 10 days, and examined kidneys 3 wk after RUUO. UUO resulted in attenuation of renal parenchyma. FACS analysis of endothelial progenitor (EPC), mesenchymal stem (MSC) and hematopoietic stem (HSC) cells obtained from UUO kidneys by collagenase-dispersed single-cell suspension showed significant increase in EPC, MSC, and HSC compared with control. After RUUO cortical parenchyma was nearly restored, and TIS score improved by 3 wk. This reversal process was associated with return of stem cells toward baseline level. When animals were chronically treated with nitric oxide synthase (NOS) inhibitor at a dose that did not induce hypertension but resulted in endothelial dysfunction, TIS scores were not different from control UUO, but EPC number in the kidney decreased significantly; however, parenchymal regeneration in these mice was similar to control. Blockade of CXCR4-mediated engraftment resulted in dramatic worsening of UUO and RUUO. Similar results were obtained in caveolin-1-deficient but not -overexpressing mice, reflecting the fact that activation of CXCR4 occurs in caveolae. The present data show increase in EPC, HSC, and MSC population during UUO and a tendency for these cells to decrease to control level during RUUO. These processes are minimally affected by chronic NOS inhibition. Blockade of CXCR4-stromal cell-derived factor-1 (SDF-1) interaction by AMD3100 or caveolin-1 deficiency significantly reduced the UUO-associated surge in stem cells and prevented parenchymal regeneration after RUUO. We conclude that the surge in stem cell accumulation during UUO is a prerequisite for regeneration of renal parenchyma.

Design of an advanced temporary hip prosthesis for an effective recovery of septic mobilizations: a preliminary study

The purpose of this study was the design and preliminary feasibility study of an advanced temporary hip prosthesis acting as an in-site drug dispensing system. An interactive device was designed to improve the recovery of bone infections compared to the mechanical spacers currently used in septic mobilizations. A commercial device was chosen and modified specifically for the purpose. First of all, the device was provided with a hydraulic multi-channel system connected via catheter to a subcutaneous valve, refillable with a drug aqueous solution from the outside. Moreover, since it allows samples of biological fluids for analyses to be drawn directly from the implantation site, this chemical dispensing system was designed to allow the course of infections to be monitored and customized therapies to be dosed. The insertion of biocompatible membranes inside the channel ends was considered essential to prevent their occlusion by fibrous tissue growth, thereby preserving the device functionality. Moreover, a biodegradable spongy ring was designed to be fixed onto the stem in distal position both to give primary stability to the implant and to act simultaneously as a scaffold for bonelike cell growth.

Periosteal chondroma of the proximal radius: a case report

When a chondroma is localized in the superficial region of the bone it is defined periosteal or juxtacortical chondroma. This is a rare and benign cartilaginous lesion that more frequently affects males, and is generally observed in the tubular bones of the hand; it may, however, affect the other major bones, particularly the proximal end of the humerus. Age of onset is the second or third decade of life. Symptoms include moderate local pain. The clinical case presented here has two special features: the first is the site; based on an analysis of the international literature it seems that an analogous lesion at the level of the radial neck has not as yet been described; the second is the symptomatology that brought the patient to our attention.

Caveolinopathies: mutations in caveolin-3 cause four distinct autosomal dominant muscle diseases

The caveolin-3 protein is expressed exclusively in muscle cells. Caveolin-3 expression is sufficient to form caveolae-sarcolemmal invaginations that are 50 to 100 nm in diameter. Monomers of caveolin-3 oligomerize to form high molecular mass scaffolding on the cytoplasmic surface of the sarcolemmal membrane. A mutation in one caveolin-3 allele produces an aberrant protein product capable of sequestering the normal caveolin-3 protein in the Golgi apparatus of skeletal muscle cells. Improper caveolin-3 oligomerization and membrane localization result in skeletal muscle T-tubule system derangement, sarcolemmal membrane alterations, and large subsarcolemmal vesicle formation. To date, there have been eight autosomal dominant caveolin-3 mutations identified in the human population. Caveolin-3 mutations can result in four distinct, sometimes overlapping, muscle disease phenotypes: limb girdle muscular dystrophy, rippling muscle disease, distal myopathy, and hyperCKemia. Thus, the caveolin-3 mutant genotype-to-phenotype relation represents a clear example of how genetic background can influence phenotypic outcome. This review examines in detail the reported cases of patients with caveolin-3 mutations and their corresponding muscle disease phenotypes.

Compression of the lower branch of the suprascapular nerve by a cyst: description of a case and review of the literature

Ganglion cysts responsible for compression syndrome of the lower branch of the suprascapular nerve are described, but they are rare. The authors describe a well-documented case that was treated in a traditional manner by exeresis conducted through posterior access. Pain was relieved immediately, while force in external rotation and electromyographic findings improved as early as two months after surgery. One year after surgery the patient does not complain of the recurrence of symptoms. The literature is analyzed and therapeutic options available are discussed.

Familial isolated hyperCKaemia associated with a new mutation in the caveolin-3 (CAV-3) gene

An 18 year old man and his mother both presented with persistent, isolated raised serum creatine kinase (hyperCKaemia) without muscle symptoms. Analysis of caveolin-3 protein expression in muscle biopsy of the propositus showed a reduction in the protein. Genetic analysis revealed a new heterozygous mutation in the caveolin-3 (CAV-3) gene: a C-->T transition at nucleotide position 83 in exon 1 leading to a substitution of a proline for a leucine at amino acid position 28 (P28L). This is the first pathogenic mutation in the CAV-3 gene associated with isolated familial hyperCKaemia. It expands the genetic heterogeneity in patients with caveolin-3 deficiency and confirms that caveolin-3 deficiency should be considered in the differential diagnosis of isolated hyperCKaemia.

Caveolae-deficient endothelial cells show defects in the uptake and transport of albumin in vivo

The role of endothelial cell caveolae in the uptake and transport of macromolecules from the blood-space to the tissue-space remains controversial. To address this issue directly, we employed caveolin-1 gene knock-out mice that lack caveolin-1 protein expression and caveolae organelles. Here, we show that endothelial cell caveolae are required for the efficient uptake and transport of a known caveolar ligand, i.e. albumin, in vivo. Caveolin-1-null mice were perfused with 5-nm gold-conjugated albumin, and its uptake was followed by transmission electron microscopy. Our results indicate that gold-conjugated albumin is not endocytosed by Cav-1-deficient lung endothelial cells and remains in the blood vessel lumen; in contrast, gold-conjugated albumin was concentrated and internalized by lung endothelial cell caveolae in wild-type mice, as expected. To quantitate this defect in uptake, we next studied the endocytosis of radioiodinated albumin using aortic ring segments from wild-type and Cav-1-null mice. Interestingly, little or no uptake of radioiodinated albumin was observed in the aortic segments from Cav-1-deficient mice, whereas aortic segments from wild-type mice showed robust uptake that was time- and temperature-dependent and competed by unlabeled albumin. We conclude that endothelial cell caveolae are required for the efficient uptake and transport of albumin from the blood to the interstitium.

Prolactin negatively regulates caveolin-1 gene expression in the mammary gland during lactation, via a Ras-dependent mechanism

Caveolin-1 is a 22-kDa integral membrane protein that has been suggested to function as a negative regulator of mitogen-stimulated proliferation in a variety of cell types, including mammary epithelial cells. Because much of our insight into caveolin-1 function has come from the study of human breast tumor-derived cell lines in culture, the normal physiological regulators of caveolin-1 expression in the mammary gland remain unknown. Here, we examine caveolin-1 expression in mice at different stages of mammary gland development. We show that caveolin-1 expression is significantly down-regulated during late pregnancy and lactation. Upon weaning, mammary gland expression of caveolin-1 rapidly returns to non-pregnant "steady-state" levels. Injection of virgin mice with a battery of hormones normally up-regulated during lactation demonstrates that prolactin is the main mediator of caveolin-1 down-regulation. Virtually identical results were obtained with human mammary epithelial cells (hTERT-HME1) in culture. In addition, we demonstrate that prolactin-mediated down-regulation of caveolin-1 expression occurs at the level of transcriptional control and via a Ras-dependent mechanism. Interestingly, in the mammary gland, both mammary epithelial cells and the surrounding mammary adipocytes show prolactin-mediated down-regulation of caveolin-1. This hormone-dependent regulation of caveolin-1 expression is specific to the mammary fat pad. Finally, we employed HC11 cells, a well-established model of mammary epithelial cell differentiation, to study the possible functional effects of caveolin-1 expression. In the presence of lactogenic hormones, recombinant expression of caveolin-1 in HC11 cells dramatically suppresses the induction of the promoter activity and the synthesis of beta-casein, an established reporter of lactogenic differentiation and milk production. These findings may explain why caveolin-1 levels are normally down-regulated during lactation. This report is the first demonstration that caveolin-1 levels are down-regulated during a normal physiological event in vivo, i.e. lactation, because previous reports have only documented that down-regulation of caveolin-1 occurs during cell transformation and tumorigenesis.

Tyrosine phosphorylation of beta-dystroglycan at its WW domain binding motif, PPxY, recruits SH2 domain containing proteins

beta-Dystroglycan is a ubiquitously expressed integral membrane protein that undergoes tyrosine phosphorylation in an adhesion-dependent manner. However, it remains unknown whether tyrosine-phosphorylated beta-dystroglycan interacts with SH2 domain containing proteins. Here, we show that the tyrosine phosphorylation of beta-dystroglycan is constitutively elevated in v-Src transformed cells. We next reconstituted this phosphorylation event in vivo by transiently coexpressing wild-type c-Src with a fusion protein containing full-length beta-dystroglycan. Our results demonstrate that Src-induced tyrosine phosphorylation of beta-dystroglycan is strictly dependent on the presence of a PPxY motif at its extreme C-terminus. In the nonphosphorylated state, this PPxY motif is normally recognized as a ligand by the WW domain; phosphorylation at this site blocks the binding of certain WW domain containing proteins. Using a GST fusion protein carrying the cytoplasmic tail of beta-dystroglycan, we identified five SH2 domain containing proteins that interact with beta-dystroglycan in a phosphorylation-dependent manner, including c-Src, Fyn, Csk, NCK, and SHC. We localized this binding activity to the PPxY motif by employing a panel of beta-dystroglycan-derived phosphopeptides. In addition, tyrosine phosphorylation of beta-dystroglycan in vivo resulted in the coimmunoprecipitation of the same SH2 domain containing proteins, and this binding event required the beta-dystroglycan C-terminal PPxY motif. We discuss the possibility that tyrosine phosphorylation of the PPxY motif within beta-dystroglycan may act as a regulatory switch to inhibit the binding of certain WW domain containing proteins, while recruiting SH2 domain containing proteins.

Rho family GTPases regulate mammary epithelium cell growth and metastasis through distinguishable pathways

BACKGROUND

Relatively few genes have been shown to directly affect the metastatic phenotype of breast cancer epithelial cells in vivo. The Rho family of proteins, incluing the Rho, Rac and Cdc42 subfamilies, are related to the small GTP binding protein Ras and regulated diverse biological processes including gene transcription, cytoskeletal organization, cell proliferation and transformation. The effects of Cdc42, Rac and Rho on the actin cytoskeleton suggested a possible role for Rho proteins in cellular motility and metastasis; however, a formal analysis of the role of Rho proteins in breast cancer cellular growth and metastasis in vivo had not previously been performed.

MATERIALS AND METHODS

We generated a panel of MTLn3 rat mammary adenocarcinoma cells that expressed similar levels of dominant inhibitory mutants of Cdc42-, Rac- and Rho-dependent signaling, to examine the contribution of these GTPases to cell spreading, guided chemotaxis, and metastasis in vivo. The ability of Rho proteins to regulate intravasation into the peripheral blood was determined by implanting MTLn3 cell stable dominant negative lines in nude mice and measuring the formation of breast cancer cell colonies grown from the peripheral blood. Serial sectioning of the lungs was performed to determine the presence of metastasis in mice in which mammary tumors expressing the dominant negative Rho family proteins had grown to a similar size.

RESULTS

Cell spreading of MTLn3 cells was selectively abrogated by N17Rac1. N19RhoA and N17Cdc42 reduced the number of focal contacts (FCs) and disrupted the co-localization of vinculin with phosphotyrosine at FCs. While N17Rac1 and N17Cdc42 preferentially inhibited colony formation in soft agar, all three GTPases affected cell growth in vivo. To distinguish effects on tumorigenicity from intravasation into the bloodstream, implanted tumors were grown to the same size in nude mice. Each dominant inhibitory Rho protein reduced intravasation into the peripheral blood. Lung metastasis of MTLn3 cells was also abrogated by the dominant inhibitory Rho proteins, despite the presence of residual CFU.

CONCLUSIONS

These studies demonstrate for the first time a critical role for the Rho GTPases involving independent signaling pathways to limit mammary tumor cellular growth and metastasis in vivo.

Caveolin-1 null mice are viable but show evidence of hyperproliferative and vascular abnormalities

Caveolin-1 is the principal structural protein of caveolae membranes in fibroblasts and endothelia. Recently, we have shown that the human CAV-1 gene is localized to a suspected tumor suppressor locus, and mutations in Cav-1 have been implicated in human cancer. Here, we created a caveolin-1 null (CAV-1 -/-) mouse model, using standard homologous recombination techniques, to assess the role of caveolin-1 in caveolae biogenesis, endocytosis, cell proliferation, and endothelial nitric-oxide synthase (eNOS) signaling. Surprisingly, Cav-1 null mice are viable. We show that these mice lack caveolin-1 protein expression and plasmalemmal caveolae. In addition, analysis of cultured fibroblasts from Cav-1 null embryos reveals the following: (i) a loss of caveolin-2 protein expression; (ii) defects in the endocytosis of a known caveolar ligand, i.e. fluorescein isothiocyanate-albumin; and (iii) a hyperproliferative phenotype. Importantly, these phenotypic changes are reversed by recombinant expression of the caveolin-1 cDNA. Furthermore, examination of the lung parenchyma (an endothelial-rich tissue) shows hypercellularity with thickened alveolar septa and an increase in the number of vascular endothelial growth factor receptor (Flk-1)-positive endothelial cells. As predicted, endothelial cells from Cav-1 null mice lack caveolae membranes. Finally, we examined eNOS signaling by measuring the physiological response of aortic rings to various stimuli. Our results indicate that eNOS activity is up-regulated in Cav-1 null animals, and this activity can be blunted by using a specific NOS inhibitor, nitro-l-arginine methyl ester. These findings are in accordance with previous in vitro studies showing that caveolin-1 is an endogenous inhibitor of eNOS. Thus, caveolin-1 expression is required to stabilize the caveolin-2 protein product, to mediate the caveolar endocytosis of specific ligands, to negatively regulate the proliferation of certain cell types, and to provide tonic inhibition of eNOS activity in endothelial cells.

Our results in the treatment of fractures dislocations of Lisfranc's joint

The authors report their experience in the treatment of traumatic injuries of Lisfranc's joint based on 30 cases treated by surgery between 1984 and 1999. All of the patients were re-evaluated clinically and radiographically. What emerges from the study is the need for surgical stabilization with percutaneous Kirschner wires or by open procedure in cases where there are doubts or where reduction is impossible. The prognosis is worse in injuries of the medial column and in exposed fractures or when mortification of the soft tissues is present.

Ligand-independent activation of oestrogen receptor alpha by caveolin-1

Expression of caveolin-1 in the human mammary adenocarcinoma cell line MCF-7 causes ligand-independent concentration of oestrogen receptor alpha (ERalpha) in the nucleus, and potentiates ligand-independent and ligand-dependent transcription from an oestrogen response element-driven reporter gene. Furthermore, caveolin-1 co-immunoprecipitates with ERalpha [Schlegel, Wang, Katzenellenbogen, Pestell and Lisanti (1999) J. Biol. Chem. 274, 33551-33556]. In the present study we show that caveolin-1 binds directly to ERalpha. This interaction is mediated by residues 82-101 of caveolin-1 (i.e. the caveolin scaffolding domain) and residues 1-282 of ERalpha. The caveolin-binding domain of ERalpha includes the ligand-independent transactivation domain, activation function (AF)-1, but lacks the hormone-binding domain and the ligand-gated transactivation domain, AF-2. In co-transfection studies, caveolin-1 potentiates the transcriptional activation of ERalpha(1-282), a truncation mutant that has intact AF-1 and DNA-binding domains. Since AF-1 activity is regulated largely by phosphorylation we determined that co-expression with caveolin-1 increased the basal phosphorylation of ERalpha(1-282), but blocked the epidermal growth factor-dependent increase in phosphorylation. Indeed, caveolin-1 interacted with and potentiated the transactivation of an ERalpha mutant that cannot be phosphorylated by extracellular signal-regulated kinase (ERK)1/2 [ERalpha(Ser(118)-->Ala)]. Thus caveolin-1 is a novel ERalpha regulator that drives ERK1/2-independent phosphorylation and activation of AF-1.

Caveolae and caveolin-3 in muscular dystrophy

Caveolae are vesicular invaginations of the plasma membrane, and function as 'message centers' for regulating signal transduction events. Caveolin-3, a muscle-specific caveolin-related protein, is the principal structural protein of caveolar membrane domains in skeletal muscle and in the heart. Several mutations within the coding sequence of the human caveolin-3 gene (located at 3p25) have been identified. Mutations that lead to a loss of approximately 95% of caveolin-3 protein expression are responsible for a novel autosomal dominant form of limb-girdle muscular dystrophy (LGMD-1C) in humans. By contrast, upregulation of the caveolin-3 protein is associated with Duchenne muscular dystrophy (DMD). Thus, tight regulation of caveolin-3 appears essential for maintaining normal muscle health and homeostasis.

Two distinct caveolin-1 domains mediate the functional interaction of caveolin-1 with protein kinase A

Numerous components of the cAMP-based signaling cascade, namely G-proteins and G- protein coupled receptors, adenylyl cyclase, and protein kinase A (PKA) have been localized to caveolae and shown to be regulated by the caveolar marker proteins, the caveolins. In order to gain mechanistic insights into these processes in vivo, we have assessed the functional interaction of caveolin-1 (Cav-1) with PKA using mutational analysis. As two regions of Cav-1 had previously been implicated in PKA signaling in vitro, we constructed Cav-1 molecules with mutations/deletions in one or both of these domains. Examination of these mutants shows that Cav-1 requires the presence of either the scaffolding domain or the COOH-terminal domain (but not both) to functionally interact with and inhibit PKA. Interestingly, in contrast to the wild-type protein, these Cav-1 mutants are not localized to caveolae microdomains. However, upon coexpression with wild-type Cav-1, a substantial amount of the mutants was recruited to the caveolae membrane fraction. Using the Cav-1 double mutant with both disrupted scaffolding and COOH-terminal domains, we show that wild-type Cav-1's inhibition of PKA signaling can be partially abrogated in a dose-responsive manner; i.e., the mutant acts in a dominant-negative fashion. Thus, this dominant-negative caveolin-1 mutant will be extremely valuable for assessing the functional role of endogenous caveolin-1 in regulating a variety of other signaling cascades.

Ulnar nerve entrapment in Guyon's tunnel by an anomalous palmaris longus muscle with a persisting median artery

A case of ulnar nerve entrapment in Guyon's tunnel caused by an aberrant palmaris muscle, associated with a patent median artery and duplication of the median nerve, is reported.

Palmitoylation of caveolin-1 at a single site (Cys-156) controls its coupling to the c-Src tyrosine kinase: targeting of dually acylated molecules (GPI-linked, transmembrane, or cytoplasmic) to caveolae effectively uncouples c-Src and caveolin-1 (TYR-14)

Caveolin-1 was initially identified as a phosphoprotein in Rous sarcoma virus-transformed cells. Previous studies have shown that caveolin-1 is phosphorylated on tyrosine 14 by c-Src and that lipid modification of c-Src is required for this phosphorylation event to occur in vivo. Phosphocaveolin-1 (Tyr(P)-14) localizes within caveolae near focal adhesions and, through its interaction with Grb7, augments anchorage-independent growth and epidermal growth factor-stimulated cell migration. However, the cellular factors that govern the coupling of caveolin-1 to the c-Src tyrosine kinase remain largely unknown. Here, we show that palmitoylation of caveolin-1 at a single site (Cys-156) is required for coupling caveolin-1 to the c-Src tyrosine kinase. Furthermore, upon evaluating a battery of nonreceptor and receptor tyrosine kinases, we demonstrate that the tyrosine phosphorylation of caveolin-1 by c-Src is a highly selective event. We show that Src-induced tyrosine phosphorylation of caveolin-1 can be inhibited or uncoupled by targeting dually acylated proteins (namely carcinoembryonic antigen (CEA), CD36, and the NH(2)-terminal domain of Galpha(i1)) to the exoplasmic, transmembrane, and cytoplasmic regions of the caveolae membrane, respectively. Conversely, when these proteins are not properly targeted or lipid-modified, the ability of c-Src to phosphorylate caveolin-1 remains unaffected. In addition, when purified caveolae preparations are preincubated with a myristoylated peptide derived from the extreme N terminus of c-Src, the tyrosine phosphorylation of caveolin-1 is abrogated; the same peptide lacking myristoylation has no inhibitory activity. However, an analogous myristoylated peptide derived from c-Yes also has no inhibitory activity. Thus, the inhibitory effects of the myristoylated c-Src peptide are both myristoylation-dependent and sequence-specific. Finally, we investigated whether phosphocaveolin-1 (Tyr(P)-14) interacts with the Src homology 2 and/or phosphotyrosine binding domains of Grb7, the only characterized downstream mediator of its function. Taken together, our data identify a series of novel lipid-lipid-based interactions as important regulatory factors for coupling caveolin-1 to the c-Src tyrosine kinase in vivo.

Adenovirus-mediated expression of caveolin-1 in mouse liver increases plasma high-density lipoprotein levels

Caveolae are 50-100 nm plasma membrane invaginations, which function in cell signaling and transcytosis, as well as in regulating cellular cholesterol homeostasis. These subcompartments of the plasma membrane are characterized by the presence of caveolin proteins. Recent studies have indicated that caveolae may be involved in the regulation of cellular cholesterol efflux to HDL, as well as selective uptake mediated by SR-BI. In the present study, we have determined the effect of caveolin-1 overexpression in mouse liver on plasma lipoprotein metabolism. We evaluated this effect using an adenovirus-mediated gene delivery system. C57BL/6J mice were injected with adenoviruses encoding either caveolin-1 (Adcav-1) or green fluorescent protein (AdGFP) together with a transactivator adenovirus (AdtTA). We found that, after adenovirus injection, caveolin-1 was overexpressed in hepatocytes. Moreover, the recombinant protein was localized to the plasma membrane. We also found that caveolin-1 overexpression induced a marked change in the lipoprotein profile of injected animals. In caveolin-1 overexpressing animals, plasma HDL-cholesterol levels were found to be approximately 2-fold elevated, as compared with control animals. To determine the effect of caveolin-1 on SR-BI-mediated selective uptake, we infected murine hepatocytes in culture with an adenoviral vector carrying the caveolin-1 cDNA or GFP as a control protein. We show that, in primary cultures of hepatocytes, caveolin-1 inhibits DiI-HDL uptake mediated by SR-BI. This result would mechanistically explain the increased plasma HDL-cholesterol levels we observed in caveolin-1 adenovirus-injected animals. In addition, caveolin-1 expression increased the secretion of apolipoprotein A-I in cultured hepatocytes and increased apolipoprotein A-I plasma levels in mice. Our study therefore demonstrates an important role for caveolin-1 in regulating HDL metabolism.

Caveolin-1 expression negatively regulates cell cycle progression by inducing G(0)/G(1) arrest via a p53/p21(WAF1/Cip1)-dependent mechanism

Caveolin-1 is a principal component of caveolae membranes in vivo. Caveolin-1 mRNA and protein expression are lost or reduced during cell transformation by activated oncogenes. Interestingly, the human caveolin-1 gene is localized to a suspected tumor suppressor locus (7q31.1). However, it remains unknown whether caveolin-1 plays any role in regulating cell cycle progression. Here, we directly demonstrate that caveolin-1 expression arrests cells in the G(0)/G(1) phase of the cell cycle. We show that serum starvation induces up-regulation of endogenous caveolin-1 and arrests cells in the G(0)/G(1) phase of the cell cycle. Moreover, targeted down-regulation of caveolin-1 induces cells to exit the G(0)/G(1) phase. Next, we constructed a green fluorescent protein-tagged caveolin-1 (Cav-1-GFP) to examine the effect of caveolin-1 expression on cell cycle regulation. We directly demonstrate that recombinant expression of Cav-1-GFP induces arrest in the G(0)/G(1) phase of the cell cycle. To examine whether caveolin-1 expression is important for modulating cell cycle progression in vivo, we expressed wild-type caveolin-1 as a transgene in mice. Analysis of primary cultures of mouse embryonic fibroblasts from caveolin-1 transgenic mice reveals that caveolin-1 induces 1) cells to exit the S phase of the cell cycle with a concomitant increase in the G(0)/G(1) population, 2) a reduction in cellular proliferation, and 3) a reduction in the DNA replication rate. Finally, we demonstrate that caveolin-1-mediated cell cycle arrest occurs through a p53/p21-dependent pathway. Taken together, our results provide the first evidence that caveolin-1 expression plays a critical role in the modulation of cell cycle progression in vivo.

Caveolin-1, a putative tumour suppressor gene

Caveolae ('little caves') are plasma membrane specializations of 50-100 nm in diameter, and the caveolins are structural proteins used by cells to form caveolae. We and other investigators have discovered that caveolae organelles may be important both in normal signal transduction and in the pathogenesis of a number of human diseases, such as cancer. Here we describe the functional roles of the caveolin gene family and summarize the evidence that supports a role for caveolae as mediators of a number of cellular signalling processes, including apoptosis.

Caveolin-3 null mice show a loss of caveolae, changes in the microdomain distribution of the dystrophin-glycoprotein complex, and t-tubule abnormalities

Caveolin-3, a muscle-specific caveolin-related protein, is the principal structural protein of caveolae membrane domains in striated muscle cells. Recently, we identified a novel autosomal dominant form of limb-girdle muscular dystrophy (LGMD-1C) in humans that is due to mutations within the coding sequence of the human caveolin-3 gene (3p25). These LGMD-1C mutations lead to an approximately 95% reduction in caveolin-3 protein expression, i.e. a caveolin-3 deficiency. Here, we created a caveolin-3 null (CAV3 -/-) mouse model, using standard homologous recombination techniques, to mimic a caveolin-3 deficiency. We show that these mice lack caveolin-3 protein expression and sarcolemmal caveolae membranes. In addition, analysis of skeletal muscle tissue from these caveolin-3 null mice reveals: (i) mild myopathic changes; (ii) an exclusion of the dystrophin-glycoprotein complex from lipid raft domains; and (iii) abnormalities in the organization of the T-tubule system, with dilated and longitudinally oriented T-tubules. These results have clear mechanistic implications for understanding the pathogenesis of LGMD-1C at a molecular level.

Direct acetylation of the estrogen receptor alpha hinge region by p300 regulates transactivation and hormone sensitivity

Regulation of nuclear receptor gene expression involves dynamic and coordinated interactions with histone acetyl transferase (HAT) and deacetylase complexes. The estrogen receptor (ERalpha) contains two transactivation domains regulating ligand-independent and -dependent gene transcription (AF-1 and AF-2 (activation functions 1 and 2)). ERalpha-regulated gene expression involves interactions with cointegrators (e.g. p300/CBP, P/CAF) that have the capacity to modify core histone acetyl groups. Here we show that the ERalpha is acetylated in vivo. p300, but not P/CAF, selectively and directly acetylated the ERalpha at lysine residues within the ERalpha hinge/ligand binding domain. Substitution of these residues with charged or polar residues dramatically enhanced ERalpha hormone sensitivity without affecting induction by MAPK signaling, suggesting that direct ERalpha acetylation normally suppresses ligand sensitivity. These ERalpha lysine residues also regulated transcriptional activation by histone deacetylase inhibitors and p300. The conservation of the ERalpha acetylation motif in a phylogenetic subset of nuclear receptors suggests that direct acetylation of nuclear receptors may contribute to additional signaling pathways involved in metabolism and development.

Elevated expression of caveolin-1 in adenocarcinoma of the colon

Caveolins 1, 2, and 3 are the principal proteins of caveolae, the vesicular invaginations of the plasma membrane. Several reports have suggested that caveolin-1 may have a role in cellular transformation and tumorigenesis. We studied the expression of caveolin-1 and caveolin-2 in normal epithelium, adenoma, and adenocarcinoma of the colon and their possible role in tumorigenesis. Formalin-fixed, paraffin-embedded sections of 41 cases of adenocarcinoma and 13 cases of adenoma of the colon were stained immunohistochemically with anti-caveolin-1 and anti-caveolin-2 antibodies. The expression of caveolin-1 was elevated in the overwhelming majority of the adenocarcinomas, while most normal colonic epithelium and adenomas showed little or no staining. There was significant statistical correlation of the expression of caveolin-1 with adenocarcinoma but not with tumor stage. Expression of caveolin-2 was undetectable in all of the normal colonic glands, adenomas, and carcinomas. We discuss the possible clinical implications of our findings within the context of caveolins and signal transduction.

Inhibition of cellular proliferation through IkappaB kinase-independent and peroxisome proliferator-activated receptor gamma-dependent repression of cyclin D1

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-regulated nuclear receptor superfamily member. Liganded PPARgamma exerts diverse biological effects, promoting adipocyte differentiation, inhibiting tumor cellular proliferation, and regulating monocyte/macrophage and anti-inflammatory activities in vitro. In vivo studies with PPARgamma ligands showed enhancement of tumor growth, raising the possibility that reduced immune function and tumor surveillance may outweigh the direct inhibitory effects of PPARgamma ligands on cellular proliferation. Recent findings that PPARgamma ligands convey PPARgamma-independent activities through IkappaB kinase (IKK) raises important questions about the specific mechanisms through which PPARgamma ligands inhibit cellular proliferation. We investigated the mechanisms regulating the antiproliferative effect of PPARgamma. Herein PPARgamma, liganded by either natural (15d-PGJ(2) and PGD(2)) or synthetic ligands (BRL49653 and troglitazone), selectively inhibited expression of the cyclin D1 gene. The inhibition of S-phase entry and activity of the cyclin D1-dependent serine-threonine kinase (Cdk) by 15d-PGJ(2) was not observed in PPARgamma-deficient cells. Cyclin D1 overexpression reversed the S-phase inhibition by 15d-PGJ(2). Cyclin D1 repression was independent of IKK, as prostaglandins (PGs) which bound PPARgamma but lacked the IKK interactive cyclopentone ring carbonyl group repressed cyclin D1. Cyclin D1 repression by PPARgamma involved competition for limiting abundance of p300, directed through a c-Fos binding site of the cyclin D1 promoter. 15d-PGJ(2) enhanced recruitment of p300 to PPARgamma but reduced binding to c-Fos. The identification of distinct pathways through which eicosanoids regulate anti-inflammatory and antiproliferative effects may improve the utility of COX2 inhibitors.

Influence of caveolin-1 on cellular cholesterol efflux mediated by high-density lipoproteins

Caveolin-1 is a principal structural component of caveolae membranes. These membrane microdomains participate in the regulation of signaling, transcytosis, and cholesterol homeostasis at the plasma membrane. In the present study, we determined the effect of caveolin-1 expression on cellular cholesterol efflux mediated by high-density lipoprotein (HDL). We evaluated this effect in parental NIH/3T3 cells as well as in two transformed NIH/3T3 cell lines in which caveolin-1 protein levels are dramatically downregulated. Compared with parental NIH/3T3 cells, these two transformed cell lines effluxed cholesterol more rapidly to HDL. In addition, NIH/3T3 cells harboring caveolin-1 antisense also effluxed cholesterol more rapidly to HDL. However, this effect was not due to changes in total cellular cholesterol content. We further showed that chronic HDL exposure reduced caveolin-1 protein expression in NIH/3T3 cells. HDL exposure also inhibited caveolin-1 promoter activity, suggesting a direct negative effect of HDL on caveolin-1 gene transcription. Moreover, we showed that HDL-induced downregulation of caveolin-1 prevents the uptake of oxidized low-density lipoprotein in human endothelial cells. These data suggest a novel proatherogenic role for caveolin-1, i.e., regarding the uptake and/or transcytosis of modified lipoproteins.