IS2aR, a computational tool to transform voxelized reference phantoms into patient-specific whole-body virtual CTs for peripheral dose estimation

BACKGROUND

The risk of radiogenic cancer induction due to radiotherapy depends on the dose received by the patient's organs. Knowing the position of all organs is needed to assess this dose in a personalized way. However, radiotherapy planning computed tomography (pCT) scans contain truncated patient anatomy, limiting personalized dose evaluation.

PURPOSE

To develop a simple and freely available computational tool that adapts an ICRP reference computational phantom to generate a patient-specific whole-body CT for peripheral dose computations.

METHODS

Various bone-segmentation methods were explored onto fifteen pCTs, and the one with the highest Sørensen-Dice coefficient was implemented. The reference phantom is registered to the pCT, obtaining a registration transform matrix, which is then applied to create the whole-body virtual CT. Additional validation involved a comparison of absorbed doses to organs delineated on both the pCT and the virtual CT.

RESULTS

A dedicated graphical user interface was designed and implemented to house the developed functions for i) selecting a registration region on which automatic bone segmentation and rigid registration will occur, ii) displaying the results of these processes under selectable views, and iii) exporting the final patient-specific whole-body CT. This software was termed IS2aR. The tested whole-body virtual CT generated by IS2aR fulfilled our requirements.

CONCLUSIONS

IS2aR is a user-friendly computational software to create a personalized whole-body CT containing the original structures in the reference phantom. The personalized dose deposited in peripheral organs can be estimated further to assess second cancer induction risk in epidemiological studies.

A simple analytical model for a fast 3D assessment of peripheral photon dose during coplanar isocentric photon radiotherapy

Considering that cancer survival rates have been growing and that nearly two-thirds of those survivors were exposed to clinical radiation during its treatment, the study of long-term radiation effects, especially secondary cancer induction, has become increasingly important. To correctly assess this risk, knowing the dose to out-of-field organs is essential. As it has been reported, commercial treatment planning systems do not accurately calculate the dose far away from the border of the field; analytical dose estimation models may help this purpose. In this work, the development and validation of a new three-dimensional (3D) analytical model to assess the photon peripheral dose during radiotherapy is presented. It needs only two treatment-specific input parameter values, plus information about the linac-specific leakage, when available. It is easy to use and generates 3D whole-body dose distributions and, particularly, the dose to out-of-field organs (as dose–volume histograms) outside the 5% isodose for any isocentric treatment using coplanar beams [including intensity modulated radiotherapy and volumetric modulated arc therapy (VMAT)]. The model was configured with the corresponding Monte Carlo simulation of the peripheral absorbed dose for a 6 MV abdomen treatment on the International Comission on Radiological Protection (ICRP) 110 computational phantom. It was then validated with experimental measurements using thermoluminescent dosimeters in the male ATOM anthropomorphic phantom irradiated with a VMAT treatment for prostate cancer. Additionally, its performance was challenged by applying it to a lung radiotherapy treatment very different from the one used for training. The model agreed well with measurements and simulated dose values. A graphical user interface was developed as a first step to making this work more approachable to a daily clinical application.

Study of out-of-field dose in photon radiotherapy: A commercial treatment planning system versus measurements and Monte Carlo simulations

Purpose

An accurate assessment of out‐of‐field dose is necessary to estimate the risk of second cancer after radiotherapy and the damage to the organs at risk surrounding the planning target volume. Although treatment planning systems (TPSs) calculate dose distributions outside the treatment field, little is known about the accuracy of these calculations. The aim of this work is to thoroughly compare the out‐of‐field dose distributions given by two algorithms implemented in the Monaco TPS, with measurements and full Monte Carlo simulations.

Methods

Out‐of‐field dose distributions predicted by the collapsed cone convolution (CCC) and Monte Carlo (MC_Monaco) algorithms, built into the commercially available Monaco version 5.11 TPS, are compared with measurements carried out on an Elekta Axesse linear accelerator. For the measurements, ion chambers, thermoluminescent dosimeters, and EBT3 film are used. The BEAMnrc code, built on the EGSnrc system, is used to create a model of the Elekta Axesse with the Agility collimation system, and the space phase file generated is scored by DOSXYZnrc to generate the dose distributions (MC_EGSnrc). Three different irradiation scenarios are considered: (a) a 10 × 10 cm² field, (b) an IMRT prostate plan, and (c) a three‐field lung plan. Monaco's calculations, experimental measurements, and Monte Carlo simulations are carried out in water and/or in an ICRP110 phantom.

Results

For the 10 × 10 cm² field case, CCC underestimated the dose, compared to ion chamber measurements, by 13% (differences relative to the algorithm) on average between the 5% and the ≈2% isodoses. MC_Monaco underestimated the dose only from approximately the 2% isodose for this case. Qualitatively similar results were observed for the studied IMRT case when compared to film dosimetry. For the three‐field lung plan, dose underestimations of up to ≈90% for MC_Monaco and ≈60% for CCC, relative to MC_EGSnrc simulations, were observed in mean dose to organs located beyond the 2% isodose.

Conclusions

This work shows that Monaco underestimates out‐of‐field doses in almost all the cases considered. Thus, it does not describe dose distribution beyond the border of the field accurately. This is in agreement with previously published works reporting similar results for other TPSs. Analytical models for out‐of‐field dose assessment, MC simulations or experimental measurements may be an adequate alternative for this purpose.

Cinética de degradación ruminal in situ de ensilado de rastrojo de maíz (Zea mays) con niveles crecientes de urea

Se estudió el efecto de la inclusión de urea sobre la composición y cinética de degradación ruminal in situ en el ensilado de rastrojo de maíz. Se partió de cuatro de tratamientos al adicionar el 0, 1, 2 y 3% de urea a una mezcla de rastrojo de maíz con el 10% de melaza. Se elaboraron 128 microsilos (3 kg/unidad y 4 repeticiones por tratamiento). La apertura de los silos se realizó a los 7, 14, 21, 28, 35, 42, 49 y 56 días. Se determinó el contenido de la materia seca (MS), materia orgánica (MO), proteína bruta (PB), FND y FAD. La degradabilidad in situ se obtuvo mediante el método de Mehrez y Orskov y la degradabilidad de MS y PB mediante el análisis de los residuos con el método Kjeldhal. Los datos se analizaron con el procedimiento GLM y el test de Tukey (P±

Simulation of hypoxia PET-tracer uptake in tumours: Dependence of clinical uptake-values on transport parameters and arterial input function

Poor radiotherapy outcome is in many cases related to hypoxia, due to the increased radioresistance of hypoxic tumour cells. Positron emission tomography may be used to non-invasively assess the oxygenation status of the tumour using hypoxia-specific radiotracers. Quantification and interpretation of these images remains challenging, since radiotracer binding and oxygen tension are not uniquely related. Computer simulation is a useful tool to improve the understanding of tracer dynamics and its relation to clinical uptake parameters currently used to quantify hypoxia. In this study, a model for simulating oxygen and radiotracer distribution in tumours was implemented to analyse the impact of physiological transport parameters and of the arterial input function (AIF) on: oxygenation histograms, time-activity curves, tracer binding and clinical uptake-values (tissue-to-blood ratio, TBR, and a composed hypoxia-perfusion metric, FHP). Results were obtained for parallel and orthogonal vessel architectures and for vascular fractions (VFs) of 1% and 3%. The most sensitive parameters were the AIF and the maximum binding rate (K_max). TBR allowed discriminating VF for different AIF, and FHP for different K_max, but neither TBR nor FHP were unbiased in all cases. Biases may especially occur in the comparison of TBR- or FHP-values between different tumours, where the relation between measured and actual AIF may vary. Thus, these parameters represent only surrogates rather than absolute measurements of hypoxia in tumours.

Building a network for multicenter, prospective research of central nervous system infections in South America: Process and lessons learned

Multicenter collaborative networks are essential for advancing research and improving clinical care for a variety of conditions. Research networks are particularly important for central nervous system infections, which remain difficult to study due to their sporadic occurrence and requirement for collection and testing of cerebrospinal fluid. Establishment of long-term research networks in resource-limited areas also facilitates diagnostic capacity building, surveillance for emerging pathogens, and provision of appropriate treatment where needed. We review our experience developing a research network for encephalitis among twelve hospitals in five Peruvian cities since 2009. We provide practical suggestions to aid other groups interested in advancing research on central nervous system infections in resource-limited areas.

Impact of different biologically-adapted radiotherapy strategies on tumor control evaluated with a tumor response model

Motivated by the capabilities of modern radiotherapy techniques and by the recent developments of functional imaging techniques, dose painting by numbers (DPBN) was proposed to treat tumors with heterogeneous biological characteristics. This work studies different DPBN optimization techniques for virtual head and neck tumors assessing tumor response in terms of cell survival and tumor control probability with a previously published tumor response model (TRM). Uniform doses of 2 Gy are redistributed according to the microscopic oxygen distribution and the density distribution of tumor cells in four virtual tumors with different biological characteristics. In addition, two different optimization objective functions are investigated, which: i) minimize tumor cell survival (OF_surv) or; ii) maximize the homogeneity of the density of surviving tumor cells (OF_std). Several adaptive schemes, ranging from single to daily dose optimization, are studied and the treatment response is compared to that of the uniform dose. The results show that the benefit of DPBN treatments depends on the tumor reoxygenation capability, which strongly differed among the set of virtual tumors investigated. The difference between daily (fraction by fraction) and three weekly optimizations (at the beginning of weeks 1, 3 and 4) was found to be small, and higher benefit was observed for the treatments optimized using OF_surv. This in silico study corroborates the hypothesis that DPBN may be beneficial for treatments of tumors which show reoxygenation during treatment, and that a few optimizations may be sufficient to achieve this therapeutic benefit.

The Challenge of Evaluating the Oral Health Status of Older Persons in Latin America

Knowledge Transfer Statement: This article provides an overview of the oral health status of older people from Latin American countries and the emergence of recent gerodontology research initiatives within the region.

Caracterización de la producción de ovino de carne del estado de Hidalgo, Mexico

La ovinocultura es la principal actividad pecuaria en el Estado de Hidalgo (México), siendo el segundo productor a nivel nacional y el principal proveedor de carne de ovino para la Ciudad de México apoyado también por su cercanía. Sin embargo, se desconocen los aspectos socioeconómicos y tecnológicos de los actores de la cadena agroalimentaria, por esta razón se planteó este trabajo que tiene como objetivo conocer las características de los productores de ovinos y de sus unidades de producción, así como caracterizar los actores y los procesos de transformación y consumo de carne en el estado de Hidalgo. Se diseñaron y aplicaron tres cuestionarios a 114 productores, a 56 transformadores y a 421 consumidores, clasificando en tres clases cada uno de los grupos. Los resultados obtenidos indicaron que existen productores con variantes en uso de tecnología, siendo los sistemas de pastoreo los de menor desarrollo y con mayor empleo familiar, el principal producto consumido es la carne destinada a barbacoa, plato tradicional que se consume principalmente en fiestas y fines de semana. La información generada es de gran utilidad para el diseño de política de apoyo a la producción de ovinos en el estado de Hidalgo.

A voxel-based multiscale model to simulate the radiation response of hypoxic tumors

PURPOSE

In radiotherapy, it is important to predict the response of tumors to irradiation prior to the treatment. This is especially important for hypoxic tumors, which are known to be highly radioresistant. Mathematical modeling based on the dose distribution, biological parameters, and medical images may help to improve this prediction and to optimize the treatment plan.

METHODS

A voxel-based multiscale tumor response model for simulating the radiation response of hypoxic tumors was developed. It considers viable and dead tumor cells, capillary and normal cells, as well as the most relevant biological processes such as (i) proliferation of tumor cells, (ii) hypoxia-induced angiogenesis, (iii) spatial exchange of cells leading to tumor growth, (iv) oxygen-dependent cell survival after irradiation, (v) resorption of dead cells, and (vi) spatial exchange of cells leading to tumor shrinkage. Oxygenation is described on a microscopic scale using a previously published tumor oxygenation model, which calculates the oxygen distribution for each voxel using the vascular fraction as the most important input parameter. To demonstrate the capabilities of the model, the dependence of the oxygen distribution on tumor growth and radiation-induced shrinkage is investigated. In addition, the impact of three different reoxygenation processes is compared and tumor control probability (TCP) curves for a squamous cells carcinoma of the head and neck (HNSSC) are simulated under normoxic and hypoxic conditions.

RESULTS

The model describes the spatiotemporal behavior of the tumor on three different scales: (i) on the macroscopic scale, it describes tumor growth and shrinkage during radiation treatment, (ii) on a mesoscopic scale, it provides the cell density and vascular fraction for each voxel, and (iii) on the microscopic scale, the oxygen distribution may be obtained in terms of oxygen histograms. With increasing tumor size, the simulated tumors develop a hypoxic core. Within the model, tumor shrinkage was found to be significantly more important for reoxygenation than angiogenesis or decreased oxygen consumption due to an increased fraction of dead cells. In the studied HNSSC-case, the TCD50 values (dose at 50% TCP) decreased from 71.0 Gy under hypoxic to 53.6 Gy under the oxic condition.

CONCLUSIONS

The results obtained with the developed multiscale model are in accordance with expectations based on radiobiological principles and clinical experience. As the model is voxel-based, radiological imaging methods may help to provide the required 3D-characterization of the tumor prior to irradiation. For clinical application, the model has to be further validated with experimental and clinical data. If this is achieved, the model may be used to optimize fractionation schedules and dose distributions for the treatment of hypoxic tumors.

A model to simulate the oxygen distribution in hypoxic tumors for different vascular architectures

PURPOSE

As hypoxic cells are more resistant to photon radiation, it is desirable to obtain information about the oxygen distribution in tumors prior to the radiation treatment. Noninvasive techniques are currently not able to provide reliable oxygenation maps with sufficient spatial resolution; therefore mathematical models may help to simulate microvascular architectures and the resulting oxygen distributions in the surrounding tissue. Here, the authors present a new computer model, which uses the vascular fraction of tumor voxels, in principle measurable noninvasively in vivo, as input parameter for simulating realistic PO2 histograms in tumors, assuming certain 3D vascular architectures.

METHODS

Oxygen distributions were calculated by solving a reaction-diffusion equation in a reference volume using the particle strength exchange method. Different types of vessel architectures as well as different degrees of vascular heterogeneities are considered. Two types of acute hypoxia (ischemic and hypoxemic) occurring additionally to diffusion-limited (chronic) hypoxia were implemented as well.

RESULTS

No statistically significant differences were observed when comparing 2D- and 3D-vessel architectures (p>0.79 in all cases) and highly heterogeneously distributed linear vessels show good agreement, when comparing with published experimental intervessel distance distributions and PO2 histograms. It could be shown that, if information about additional acute hypoxia is available, its contribution to the hypoxic fraction (HF) can be simulated as well. Increases of 128% and 168% in the HF were obtained when representative cases of ischemic and hypoxemic acute hypoxia, respectively, were considered in the simulations.

CONCLUSIONS

The presented model is able to simulate realistic microscopic oxygen distributions in tumors assuming reasonable vessel architectures and using the vascular fraction as macroscopic input parameter. The model may be used to generate PO2 histograms, which are needed as input in models predicting the radiation response of hypoxic tumors.

Crosstalk between PKCα and Notch-4 in endocrine-resistant breast cancer cells

The Notch pathway is functionally important in breast cancer. Notch-1 has been reported to maintain an estrogen-independent phenotype in estrogen receptor α (ERα)+ breast cancer cells. Notch-4 expression correlates with Ki67. Notch-4 also plays a key role in breast cancer stem-like cells. Estrogen-independent breast cancer cell lines have higher Notch activity than estrogen-dependent lines. Protein kinase Cα (PKCα) overexpression is common in endocrine-resistant breast cancers and promotes tamoxifen (TAM)-resistant growth in breast cancer cell lines. We tested whether PKCα overexpression affects Notch activity and whether Notch signaling contributes to endocrine resistance in PKCα-overexpressing breast cancer cells.Analysis of published microarray data from ERα+ breast carcinomas shows that PKCα expression correlates strongly with Notch-4. Real-time reverse transcription PCR and immunohistochemistry on archival specimens confirmed this finding. In a PKCα-overexpressing, TAM-resistant T47D model, PKCα selectively increases Notch-4, but not Notch-1, expression in vitro and in vivo. This effect is mediated by activator protein-1 (AP-1) occupancy of the Notch-4 promoter. Notch-4 knockdown inhibits estrogen-independent growth of PKCα-overexpressing T47D cells, whereas Notch-4IC expression stimulates it. Gene expression profiling shows that multiple genes and pathways associated with endocrine resistance are induced in Notch-4IC- and PKCα-expressing T47D cells. In PKCα-overexpressing T47D xenografts, an orally active γ-secretase inhibitor at clinically relevant doses significantly decreased estrogen-independent tumor growth, alone and in combination with TAM. In conclusion, PKCα overexpression induces Notch-4 through AP-1. Notch-4 promotes estrogen-independent, TAM-resistant growth and activates multiple pathways connected with endocrine resistance and chemoresistance. Notch inhibitors should be clinically evaluated in PKCα- and Notch-4-overexpressing, endocrine-resistant breast cancers.

Abstract P6-04-22: Regulation of Notch localization by endocrine therapy in Estrogen Receptor positive breast cancer cells: Clinical implications for endocrine resistance

Background: Estrogen receptors occur in about two-thirds of breast tumors and endocrine therapy is probably the most important systemic therapy for hormone receptor positive breast cancer. However, after an initial response to hormonal therapy, most tumors develop resistance leading to disease progression. Central mechanisms thought to be involved in this process include: 1) alterations in tumor cell physiology causing insensitivity to drug-induced apoptosis or induction of drug-detoxifying mechanisms; 2) expression of energy-dependent transporters that eject anti-cancer drugs from cells and 3) the emergence of cancer stem-like cell clones that are estrogen-independent and/or antiestrogen resistant. We and others have shown that Notch signaling mediates survival signals in ER+ breast cancer cells; induces expression of drug transporter ABCG2 (BCRP), activates ERα in the absence of estrogen and mediates survival of breast cancer stem-like cells. Previously, we demonstrated a crosstalk between ERα and Notch signaling whereby estrogen inhibits Notch activation and estrogen withdrawal or tamoxifen re-activate Notch, a possible mechanism of resistance. The mechanism of these effects has remained elusive.

Methods: we used sub-cellular fractionation and immunofluorescence staining to investigate the total expression and cellular distribution of Notch signaling components in MCF-7 cells treated with 17-β-estradiol, or estrogen-free medium.

Results: Our data shows that in cells treated with estrogen-free medium, Notch1 is located in the Lipid Rafts (LR) in the plasma membrane, along with Notch signaling components such as presenilin 1 (the catalytic subunit of γ-secretase), ADAM10 and Notch negative regulator NUMB. There is published evidence that γ-secretase is most active in lipid rafts.17-β-Estradiol modifies the membrane lipid composition and change the localization of Notch and Notch regulators (such as ADAM10, presenilin-1 and NUMB) at the plasma membrane, thereby altering the activation of Notch. These observations are consistent with a model in which the lipid composition of the plasma membrane is a critical factor in regulating the rate of Notch activation. FDA-approved cholesterol lowering drugs affect Notch signaling in ways consistent with this model.

Conclusions: Our findings indicate that endocrine therapy affects Notch signaling at least in part through alterations in membrane composition and lipid raft localization of Notch signaling components.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-04-22.

Histone genes in trypanosomatids

Histone genes in Trypanosomatids are of considerable interest because these flagellates do not condense their chromatin during mitosis. In contrast to higher eukaryotes, histone genes in Trypanosomatids are found on separate chromosomes, and their transcripts are polyadenylated. Sequence similarity of Trypanosomatid core histones with those of higher eukaryotes is found predominantly in the globular region; the N-terminal is highly divergent. Finally, in general, Trypanosomatid histones H1 are of low molecular weight, bearing closest homology to the C-terminal region of the higher eukaryote histones H1. These features constitute interesting targets for a rational approach to the study of these protozoa, as discussed here by Norbel Galanti and colleagues.

Abstract P4-03-01: Inhibition of Fatty Acid Synthase (FASN) Sensitizes Breast Cancer Cells to Chemotherapy and Disrupts the Lipid Rafts

MN

Background: Breast cancer is the second leading cause of cancer death of women worldwide. One of the major challenges for a better prognosis of breast cancer patients is the ineffectiveness of chemotherapy and drug resistance. To investigate the mechanisms of drug resistance, resistant cancer cell lines have been established with various anticancer agents. We found that FASN, an important metabolic enzyme overexpressed in aggressive carcinomas, is t responsible in part for the drug resistance phenotype of breast cancer cells. Our findings show that blockage of FASN augments the cytotoxicity of the anti-mitotic drug Taxol in breast cancer cells. Moreover, C75 and Taxol have a synergistic effect both drugs are combined. The in vivo effect of C75 and Taxol and the mechanism by which blockage of FASN sensitizes the cells to chemotherapy are unknown. Material and Methods: In this study first we show the effect of C75 plus Taxol in breast tumor growth. BT474 cells were injected into the mammary fat pad of nude mice to generate the tumors. When the tumors were measurable we treated the mice with C75, Taxol or with a combination of both drugs. Second we studied the lipid rafts disruption after treatments by sucrose gradient and immunofluorescence. Results: We found that C75 plus Taxol extensively inhibited the tumor growth 9 fold and reduced the tumor size in 4 fold comparedn to the control mice (no treatement). In comparison C75 alone reduced the tumor growth in 1.5 fold only; and Taxol 2.5 fold compared to the control mice. These results show for first time that blockage of FASN (with C75) sensitizes breast cancer tumors to Taxol treatment in vivo. In addition, we studied the possible mechanism involved in the sensitization of breast cancer cells to Taxol by FASN blockage. Previous studies reported that blockage of FASN or Taxol treatment decrease the sphingolipids synthesis. Sphingolipids and cholesterol are the most abundant fatty acid in the lipid rafts in the plasma membrane. Disruption of lipid rafts has been shown to induce apoptosis in different carcinoma cell lines. Based in these findings, we studied lipid rafts in BT474 cells treated with C75, Taxol or combination of both with sucrose gradient and immunofluorescence microscopy. Discussion: Our results show that C75 and Taxol disrupt the lipid rafts. Thesefindings show that FASN is a new mechanism of drug resistance and may be an ideal target for chemosensitization in breast cancer chemotherapy.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-03-01.

CYR61 Expression Promotes Taxol Resistance: A Molecular Link with the p53 in Breast

CYR61 render human breast cancer cells highly resistance to the microtubule-interfering agent Taxol, a drug of choice for the treatment of metastatic breast cancer. The angiogenic factor CYR61 and its receptor avβ3 are markedly up-regulated in very aggressive breast carcinomas. Integrin signaling has been shown to modulate cancer cell responses to chemotherapy agents. Thus, the signal transduction pathways initiated by integrin may be a potential target for inhibiting cell survival during cytotoxic drug exposure. However, the molecular mechanism for CYR61-induces cytoprotection still unknown. Our data demonstrates that functional blockade of avβ3 with a synthetic chemical peptidomimetic based upon the αvβ3 the RGD (Arg-Gly-Asp) motif, is specifically cytotoxic towards CYR61-overexpressing breast cancer cells and that pharmacological interference of the CYR61/αvβ3 interaction restores Taxol efficacy. This data suggests that a previously unrecognized CYR61/αvβ3-driven cellular signaling actively modulates cell growth, apoptosis and chemosensitivity. To better understand the mechanism by which CYR61 induces Taxol resistance, we studied a series of molecular events and reveal that CYR61 prevents Taxol induction of p53 accumulation, blocks p21WAF1/CIP1 overexpression, and furthermore we demonstrated that CYR61 induces JNK activation. These observations suggest that increased expression of CYR61 could promote a chemoresistance by suppressing a specific pro-apoptotic signaling while still given chemotherapeutic treatments to induce cell damage.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1139.

Knockout of Heregulin (HRG) Expression Reverts Paclitaxel-Resistance and Promotes Mesenchymal Epithelial Transition (MET) of Triple Negative Breast Cancer Cells

The growth factor Heregulin (HRG) is expressed in about 30% of breast cancer tumors, and induces tumorigenicity and metastasis of breast cancer cells. We have demonstrated previously that HRG overexpression renders breast cancer cells resistance to the microtubule-interfering agent Taxol, a drug of choice for the treatment of metastatic breast cancer. The mechanism by which HRG induces Taxol resistance is largely unknown. It is also known that triple negative breast cancer tumors do express high levels of HRG and unfortunately they do not respond to HRG. Our studies were aimed at targeting HRG with the goal of achieving a therapeutic target as well as restoring the response to Taxol, while preventing the formation of metastasis. Thus, we knocked-down HRG expression in three different breast cancer cell lines: MDA-MB-23, HS578T and BT549. Our data demonstrates that HRG expression is an absolute requirement for the anchorage-independent growth for triple negative breast cancer cells, since none of the breast cancer cells MDA-MB-231, HS578T and BT549 stable expressing the silencing (shRNA) for HRG, were capable of forming colony in soft agar. Furthermore, these cells, not only no longer were not anchorage-independent were no longer resistant to Taxol, to the contrary the shRNA/HRG cells were exquisitely sensitive to Taxol, to induce growth inhibition and apoptosis. More importantly, we observed that the disorganized structured observed in 3D matrigel culture observed for triple negative cells, was completely abolished once HRG was knockdown and a very organized structure. These characteristics resembled an EMT (epithelial-mesenchymal epithelial transition (MET). This should be deemed a potential target in developing therapies for triple negative breast carcinomas.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1142.

Heregulin induces Iressa-resistance of breast cancer cells through receptor heterodimerization

Abstract #2016

Background: Heregulins (HRGs) are known as soluble secreted growth factors that are involved via binding and activating HER3 and HER4 cell surface receptors in cell proliferation, metastasis, survival, and differentiation in normal and malignant tissues. We have previously shown that up-regulation of HRG is sufficient for development of mammary tumors independently of estrogen stimulation and HER2 overexpression. Moreover, inhibition of HRG expression suppresses the aggressive phenotype by decreasing HER activation and reducing matrix metalloproteinase-9 activity. Therefore, HRG appears to be a key modulator of tumorigenicity and metastasis in triple negative breast carcinomas. Resistance to anti-epidermal growth factor receptor (anti-EGFR) therapies such as gefitinib is an emerging clinical problem. In this regard we have used MDA231, HS578T and BT549 cells to study potential mechanisms of gefitinib resistance. These cell lines are EGF independent and express high levels of HRG and resistant to gefitinib. Our hypothesis is that HRG signaling through HER3 induces resistance to EGFR blockade. To demonstrate this, we knocked down HRG expression by RNA interference (RNAi) in MDA231, HS578T, and BT549 cells.
 Material and Methods: Down-regulation of HRG is observed in MDA231, HS578T, and BT549 cells transduced with HRG siRNA lentiviral vector pRNAt-U6.2. Sensitivity to gefitinib was determined by MTT assays and soft agar assays. Each experiment was repeated at least 3 times, all data were analyzed by ANOVA. The level of significance was set at p < 0.05.
 Results: Our results show that when comparing to their parental cells, all MDA231/HRGsiRNA, HS578T/HRGsiRNA and BT549/HRGsiRNA cells grew at a lower rate and become sensitive to gefitinib. Our results indicate that HRG can overcome the inhibitory effects of gefitinib on cell growth and HRG signaling allows at least in part, the acquisition of gefitinib-resistant phenotype.
 Discussion: Although the mechanism for the resistance is still under further investigation, our observation has implications for the effectiveness of anti-EGFR therapies in breast cancer where HRG induced receptor heterodimerization in EGFR-positive breast tumors.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2016.

Nonendodontic periapical lesions: a retrospective study in Chile

AIM

To determine the frequency with which the histopathological diagnosis of periapical lesions contributes to a change in the clinical diagnosis.

METHODOLOGY

Cases having a clinical diagnosis of disease resulting from dental pulp necrosis were selected from the database of the Oral Pathology Reference Institute between 1975 and 2005. Cases with different histopathological diagnoses were determined and information about age and gender of the patient, location of associated tooth, pulp status and the histopathological diagnosis were recorded. The percentage of nonendodontic periapical lesions was then determined.

RESULTS

In the 30-year period, 32,423 [corrected] biopsy specimens were received. Overall 4006 (9.13%) had a clinical diagnosis of pulpal necrosis with associated pathosis in the periradicular area. Within this group, 26 cases (0.65%) had a histopathological diagnosis of nonendodontic pathology. Keratocystic odontogenic tumour was the most frequent nonendodontic lesion (11 cases) in the periradicular region followed by central giant cell granuloma (three cases), chronic sinusitis (three cases) and one case each of the following lesions: nasopalatine duct cyst, lateral periodontal cyst, calcifying cystic odontogenic tumour, ameloblastic fibroma, squamous odontogenic tumour, cemental dysplasia, haemangioma, foreign body cell granuloma and amalgam tattoo.

CONCLUSIONS

The histopathological study of periapical pathosis can occasionally reveal nonendodontic lesions. Odontogenic tumours made up the largest group.

Early post-larval development of the endoparasitic platyhelminth Mesocestoides corti: trypsin provokes reversible tegumental damage leading to serum-induced cell proliferation and growth

Mesocestoides corti is a suitable in vitro model for studying the development of human endoparasitic platyhelminthes. Treatment with trypsin, supplemented with fetal bovine serum (FBS), induces M. corti development from larvae (tetrathyridia) to segmented adult worm; however, the role of this protease and of FBS in post-larval development induction remains unknown. To characterize the participation of trypsin enzymatic activity and of FBS in the induction of tetrathyridia growth and development, both stimuli were added to the larvae either together or sequentially. Additionally, specific inhibition of trypsin activity was also monitored. Finally, the effect of the enzyme on the parasite tegument as well as the proliferative activity and location of proliferating cells after induction of tetrathyridia development were also studied. We conclude that trypsin-induced tetrathyridia development to adult worm is FBS-dependent and that the effect of serum factors is dependent upon a previous trypsin-induced reversible damage to the larva tegument. In dividing and non-dividing tetrathyridia, proliferative activity of cells is mainly located within the apical massif in the anterior region and nerve cords of larvae, respectively. In tetrathyridia stimulated to develop to adult worms, an intense proliferative activity is evident along the nerve cords. Our results suggest that in natural infections the tetrathyridia tegument is temporally made permeable to growth factors by proteolytic enzyme activity in the intestine juice of the definitive host, thus leading to development to adult worms.

Prevalence of oral mucosal lesions in elderly people in Santiago, Chile

BACKGROUND

Oral prevalence studies are important to know the state of health and the needs of treatment. Our aim was to determine the prevalence of oral mucosal lesions and associated factors among aging Chileans.

METHODS

A random sample by age, gender, and socioeconomic status was obtained, comprising 889 individuals older than 65 years. Individuals were interviewed and examined in Santiago, the capital of Chile, according to the World Health Organization guidelines.

RESULTS

The prevalence of one or more oral mucosal lesions in the sample was 53%. Logistic regression model revealed that denture use increased the probability of one or more oral mucosal lesions by threefold, while age, gender, smoking, medication use, xerostomia, and social or cultural factors had no effect. The most common lesion was denture stomatitis (22.3%), followed by irritative hyperplasia (9.4%), oral mucosal varicosities (9%), solitary pigmented lesions (4%), traumatic ulcer (3.5%), angular cheilitis (2.9%), multiple pigmented lesions (2.8%), hemangioma (2.3%), lichen planus (2.1%), leukoplakia (1.7%), recurrent aphthous stomatitis (1.4%), nicotine stomatitis (1.3%), median rhomboid glossitis (0.9%), actinic cheilitis (0.9%), pyogenic granuloma (0.7%), oral squamous papiloma (0.6%), and mucocele (0.2%). One case of oral cancer was observed. Different factors increased the probability of specific oral mucosal pathologies.

CONCLUSIONS

We can conclude that oral mucosal lesions are common in elderly people in Santiago, suggesting the necessity for improved standards of prevention, and diagnostic and opportune treatment of these lesions.

Histone H1 and core histones in Leishmania and Crithidia: comparison with Trypanosoma

The Trypanosomatidae family is characterized by flagellated protozoa presenting a kinetoplast. Several genera of this family contain species that are pathogenic to man and domestic animals. Their chromatin is not condensed into chromosomes during cell division. As a contribution to the understanding of basic aspects of their genome organization, we present a systematic characterization of the histones from three genera of the Trypanosomatidae family. Crithidia fasciculata and Leishmania mexicana show core nucleosomal histones with electrophoretic mobilities both similar to and different from those of Trypanosoma cruzi and higher eukaryotes. Another protein is extracted from the chromatin of these organisms by procedures designed to purify histone H1. This protein presents elution profiles by HPLC and amino acid composition of histone H1. Considering these data and the high mobility of this protein in Triton-acetic acid-urea-polyacrylamide gel electrophoresis, as well as its position relative to the nucleosomal core histones in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we postulate that Crithidia and Leishmania possess a histone H1 shorter than that of higher eukaryotes as we have previously shown to be the case for T. cruzi. The possible presence of a shorter histone H1 in these trypanosomatids may explain the absence of chromatin condensation during cell division in these flagellates.