Longitudinal profiling identifies co-occurring BRCA1/2 reversions, TP53BP1, RIF1 and PAXIP1 mutations in PARP inhibitor-resistant advanced breast cancer

BACKGROUND

Resistance to therapies that target homologous recombination deficiency (HRD) in breast cancer limits their overall effectiveness. Multiple, preclinically validated, mechanisms of resistance have been proposed, but their existence and relative frequency in clinical disease are unclear, as is how to target resistance.

PATIENTS AND METHODS

Longitudinal mutation and methylation profiling of circulating tumour (ct)DNA was carried out in 47 patients with metastatic BRCA1-, BRCA2- or PALB2-mutant breast cancer treated with HRD-targeted therapy who developed progressive disease-18 patients had primary resistance and 29 exhibited response followed by resistance. ctDNA isolated at multiple time points in the patient treatment course (before, on-treatment and at progression) was sequenced using a novel >750-gene intron/exon targeted sequencing panel. Where available, matched tumour biopsies were whole exome and RNA sequenced and also used to assess nuclear RAD51.

RESULTS

BRCA1/2 reversion mutations were present in 60% of patients and were the most prevalent form of resistance. In 10 cases, reversions were detected in ctDNA before clinical progression. Two new reversion-based mechanisms were identified: (i) intragenic BRCA1/2 deletions with intronic breakpoints; and (ii) intragenic BRCA1/2 secondary mutations that formed novel splice acceptor sites, the latter being confirmed by in vitro minigene reporter assays. When seen before commencing subsequent treatment, reversions were associated with significantly shorter time to progression. Tumours with reversions retained HRD mutational signatures but had functional homologous recombination based on RAD51 status. Although less frequent than reversions, nonreversion mechanisms [loss-of-function (LoF) mutations in TP53BP1, RIF1 or PAXIP1] were evident in patients with acquired resistance and occasionally coexisted with reversions, challenging the notion that singular resistance mechanisms emerge in each patient.

CONCLUSIONS

These observations map the prevalence of candidate drivers of resistance across time in a clinical setting, information with implications for clinical management and trial design in HRD breast cancers.

Current and future diagnostic and treatment strategies for patients with invasive lobular breast cancer

BACKGROUND

Invasive lobular breast cancer (ILC) is the second most common type of breast cancer after invasive breast cancer of no special type (NST), representing up to 15% of all breast cancers.

DESIGN

Latest data on ILC are presented, focusing on diagnosis, molecular make-up according to the European Society for Medical Oncology Scale for Clinical Actionability of molecular Targets (ESCAT) guidelines, treatment in the early and metastatic setting and ILC-focused clinical trials.

RESULTS

At the imaging level, magnetic resonance imaging-based and novel positron emission tomography/computed tomography-based techniques can overcome the limitations of currently used imaging techniques for diagnosing ILC. At the pathology level, E-cadherin immunohistochemistry could help improving inter-pathologist agreement. The majority of patients with ILC do not seem to benefit as much from (neo-)adjuvant chemotherapy as patients with NST, although chemotherapy might be required in a subset of high-risk patients. No differences in treatment efficacy are seen for anti-human epidermal growth factor receptor 2 (HER2) therapies in the adjuvant setting and cyclin-dependent kinases 4 and 6 inhibitors in the metastatic setting. The clinical utility of the commercially available prognostic gene expression-based tests is unclear for patients with ILC. Several ESCAT alterations differ in frequency between ILC and NST. Germline BRCA1 and PALB2 alterations are less frequent in patients with ILC, while germline CDH1 (gene coding for E-cadherin) alterations are more frequent in patients with ILC. Somatic HER2 mutations are more frequent in ILC, especially in metastases (15% ILC versus 5% NST). A high tumour mutational burden, relevant for immune checkpoint inhibition, is more frequent in ILC metastases (16%) than in NST metastases (5%). Tumours with somatic inactivating CDH1 mutations may be vulnerable for treatment with ROS1 inhibitors, a concept currently investigated in early and metastatic ILC.

CONCLUSION

ILC is a unique malignancy based on its pathological and biological features leading to differences in diagnosis as well as in treatment response, resistance and targets as compared to NST.

Defining in Detail and Evaluating Reliability of DSM-5 Criteria for Autism Spectrum Disorder (ASD) Among Children

This paper describes a process to define a comprehensive list of exemplars for seven core Diagnostic and Statistical Manual (DSM) diagnostic criteria for autism spectrum disorder (ASD), and report on interrater reliability in applying these exemplars to determine ASD case classification. Clinicians completed an iterative process to map specific exemplars from the CDC Autism and Developmental Disabilities Monitoring (ADDM) Network criteria for ASD surveillance, DSM-5 text, and diagnostic assessments to each of the core DSM-5 ASD criteria. Clinicians applied the diagnostic exemplars to child behavioral descriptions in existing evaluation records to establish initial reliability standards and then for blinded clinician review in one site (phase 1) and for two ADDM Network surveillance years (phase 2). Interrater reliability for each of the DSM-5 diagnostic categories and overall ASD classification was high (defined as very good .60-.79 to excellent ≥ .80 Kappa values) across sex, race/ethnicity, and cognitive levels for both phases. Classification of DSM-5 ASD by mapping specific exemplars from evaluation records by a diverse group of clinician raters is feasible and reliable. This framework provides confidence in the consistency of prevalence classifications of ASD and may be further applied to improve consistency of ASD diagnoses in clinical settings.

ESMO recommendations on predictive biomarker testing for homologous recombination deficiency and PARP inhibitor benefit in ovarian cancer

BACKGROUND

Homologous recombination repair deficiency (HRD) is a frequent feature of high-grade serous ovarian, fallopian tube and peritoneal carcinoma (HGSC) and is associated with sensitivity to PARP inhibitor (PARPi) therapy. HRD testing provides an opportunity to optimise PARPi use in HGSC but methodologies are diverse and clinical application remains controversial.

MATERIALS AND METHODS

To define best practice for HRD testing in HGSC the ESMO Translational Research and Precision Medicine Working Group launched a collaborative project that incorporated a systematic review approach. The main aims were to (i) define the term 'HRD test'; (ii) provide an overview of the biological rationale and the level of evidence supporting currently available HRD tests; (iii) provide recommendations on the clinical utility of HRD tests in clinical management of HGSC.

RESULTS

A broad range of repair genes, genomic scars, mutational signatures and functional assays are associated with a history of HRD. Currently, the clinical validity of HRD tests in ovarian cancer is best assessed, not in terms of biological HRD status per se, but in terms of PARPi benefit. Clinical trials evidence supports the use of BRCA mutation testing and two commercially available assays that also incorporate genomic instability for identifying subgroups of HGSCs that derive different magnitudes of benefit from PARPi therapy, albeit with some variation by clinical scenario. These tests can be used to inform treatment selection and scheduling but their use is limited by a failure to consistently identify a subgroup of patients who derive no benefit from PARPis in most studies. Existing tests lack negative predictive value and inadequately address the complex and dynamic nature of the HRD phenotype.

CONCLUSIONS

Currently available HRD tests are useful for predicting likely magnitude of benefit from PARPis but better biomarkers are urgently needed to better identify current homologous recombination proficiency status and stratify HGSC management.

A decade of clinical development of PARP inhibitors in perspective

Genomic instability is a hallmark of cancer, and often is the result of altered DNA repair capacities in tumour cells. DNA damage repair defects are common in different cancer types; these alterations can also induce tumour-specific vulnerabilities that can be exploited therapeutically. In 2009, a first-in-man clinical trial of the poly(ADP-ribose) polymerase (PARP) inhibitor olaparib clinically validated the synthetic lethal interaction between inhibition of PARP1, a key sensor of DNA damage, and BRCA1/BRCA2 deficiency. In this review, we summarize a decade of PARP inhibitor clinical development, a work that has resulted in the registration of several PARP inhibitors in breast (olaparib and talazoparib) and ovarian cancer (olaparib, niraparib and rucaparib, either alone or following platinum chemotherapy as maintenance therapy). Over the past 10 years, our knowledge on the mechanism of action of PARP inhibitor as well as how tumours become resistant has been extended, and we summarise this work here. We also discuss opportunities for expanding the precision medicine approach with PARP inhibitors, identifying a wider population who could benefit from this drug class. This includes developing and validating better predictive biomarkers for patient stratification, mainly based on homologous recombination defects beyond BRCA1/BRCA2 mutations, identifying DNA repair deficient tumours in other cancer types such as prostate or pancreatic cancer, or by designing combination therapies with PARP inhibitors.

Implementation and evaluation of a transit dosimetry system for treatment verification

PURPOSE

To evaluate a formalism for transit dosimetry using a phantom study and prospectively evaluate the protocol on a patient population undergoing 3D conformal radiotherapy.

METHODS

Amorphous silicon EPIDs were calibrated for dose and used to acquire images of delivered fields. The measured EPID dose map was back-projected using the planning CT images to calculate dose at pre-specified points within the patient using commercially available software, EPIgray (DOSIsoft, France). This software compared computed back-projected dose with treatment planning system dose. A series of tests were performed on solid water phantoms (linearity, field size effects, off-axis effects). 37 patients were enrolled in the prospective study.

RESULTS

The EPID dose response was stable and linear with dose. For all tested field sizes the agreement was good between EPID-derived and treatment planning system dose in the central axis, with performance stability up to a measured depth of 18cm (agreement within -0.5% at 10cm depth on the central axis and within -1.4% at 2cm off-axis). 126 transit images were analysed of 37 3D-conformal patients. Patient results demonstrated the potential of EPIgray with 91% of all delivered fields achieved the initial set tolerance level of ΔD of 0±5-cGy or %ΔD of 0±5%.

CONCLUSIONS

The in vivo dose verification method was simple to implement, with very few commissioning measurements needed. The system required no extra dose to the patient, and importantly was able to detect patient position errors that impacted on dose delivery in two of cases.

Sleep regulation and sex hormones exposure in men and women across adulthood

This review aims to discuss how endogenous and exogenous testosterone exposures in men and estrogens/progesterone exposures in women interact with sleep regulation. In young men, testosterone secretion peaks during sleep and is linked to sleep architecture. Animal and human studies support the notion that sleep loss suppresses testosterone secretion. Testosterone levels decline slowly throughout the aging process, but relatively few studies investigate its impact on age-related sleep modifications. Results suggest that poorer sleep quality is associated with lower testosterone concentrations and that sleep loss may have a more prominent effect on testosterone levels in older individuals. In women, sex steroid levels are characterized by a marked monthly cycle and reproductive milestones such as pregnancy and menopause. Animal models indicate that estrogens and progesterone influence sleep. Most studies do not show any clear effects of the menstrual cycle on sleep, but sample sizes are too low, and research designs often inhibit definitive conclusions. The effects of hormonal contraceptives on sleep are currently unknown. Pregnancy and the postpartum period are associated with increased sleep disturbances, but their relation to the hormonal milieu still needs to be determined. Finally, studies suggest that menopausal transition and the hormonal changes associated with it are linked to lower subjective sleep quality, but results concerning objective sleep measures are less conclusive. More research is necessary to unravel the effects of vasomotor symptoms on sleep. Hormone therapy seems to induce positive effects on sleep, but key concerns are still unresolved, including the long-term effects and efficacy of different hormonal regimens.

Abstract S4-02: Integrated genomic analyses of members of protein kinase C family identifies subtype specific alterations as novel therapeutic targets

Introduction

Members of the protein kinase C family are serine/threonine kinases that are involved in proliferation, apoptosis, cell survival and migration, and have been implicated in tumorigenesis. Recently PRKCE has been found to be up-regulated in triple-negative (TN) breast cancers and has been proposed as a target for therapeutic intervention. The aims of this study were to determine i) whether different members of the PKC family are dysregulated and/ or mutated in specific subtypes of breast cancer, ii) to investigate the impact of silencing or overexpression of members of the PKC family in cell line models representative of the different breast cancer subtypes.

Material and methods:

We obtained expression and mutational data from the cancer genome atlas (TCGA) project from 567 and 640 samples subjected to microarray-based gene expression profiling and whole exome sequencing, respectively. Pair-wise SAM analysis of TCGA gene expression data was performed to identify differential expression between subgroups (ER+, HER2+ and TN). Potential driver mutations were identified through the algorithm CHASM. Subtype specific dependencies were identified from the re-analysis of publicly available siRNA kinome-wide screens in a panel of 20 breast cancer cell lines. In vitro assessment of gene overexpression was assessed in MCF10A cells by wound healing scratch assays and 3D growth in Matrigel.

Results

PRKCA, B, I and Q were expressed at significantly higher levels in TN breast cancers. Higher expression of PRKCE was significantly associated with ER-negativity, whereas high PRKCD expression was associated with ER-positivity. Analysis of siRNA kinome-wide screen data resulted in a significant reduction in survival associated with PRKCI and PRKCE in ER-negative cells, PRKCQ in triple-negative cells, and PRKCD in ER-positive cells. Furthermore meta-analysis of published exome and whole genome sequencing data identified potentially activating recurrent kinase domain mutations in PRKCB (0.93%), Q (1.25%) and Z (0.93%), with mutations in PRKCZ being associated with higher gene expression. Forced expression of wild-type PRKCQ and PRKCZ in MCF10A cells resulted in the formation of irregular acini in 3D cell culture and expression of wild-type PRKCZ resulted in increased migration.

Conclusions

Differential expression of members of the protein kinase C family, are associated with different molecular subtypes of breast cancer. Furthermore, we have shown that breast cancer cells are dependent upon expression of these family members in vitro, which are associated with different cellular phenotypes.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr S4-02.

A high-throughput screen identifies PARP1/2 inhibitors as a potential therapy for ERCC1-deficient non-small cell lung cancer

Excision repair cross-complementation group 1 (ERCC1) is a DNA repair enzyme that is frequently defective in non-small cell lung cancer (NSCLC). Although low ERCC1 expression correlates with platinum sensitivity, the clinical effectiveness of platinum therapy is limited, highlighting the need for alternative treatment strategies. To discover new mechanism-based therapeutic strategies for ERCC1-defective tumours, we performed high-throughput drug screens in an isogenic NSCLC model of ERCC1 deficiency and dissected the mechanism underlying ERCC1-selective effects by studying molecular biomarkers of tumour cell response. The high-throughput screens identified multiple clinical poly (ADP-ribose) polymerase 1 and 2 (PARP1/2) inhibitors, such as olaparib (AZD-2281), niraparib (MK-4827) and BMN 673, as being selective for ERCC1 deficiency. We observed that ERCC1-deficient cells displayed a significant delay in double-strand break repair associated with a profound and prolonged G₂/M arrest following PARP1/2 inhibitor treatment. Importantly, we found that ERCC1 isoform 202, which has recently been shown to mediate platinum sensitivity, also modulated PARP1/2 sensitivity. A PARP1/2 inhibitor-synthetic lethal siRNA screen revealed that ERCC1 deficiency was epistatic with homologous recombination deficiency. However, ERCC1-deficient cells did not display a defect in RAD51 foci formation, suggesting that ERCC1 might be required to process PARP1/2 inhibitor-induced DNA lesions before DNA strand invasion. PARP1 silencing restored PARP1/2 inhibitor resistance in ERCC1-deficient cells but had no effect in ERCC1-proficient cells, supporting the hypothesis that PARP1 might be required for the ERCC1 selectivity of PARP1/2 inhibitors. This study suggests that PARP1/2 inhibitors as a monotherapy could represent a novel therapeutic strategy for NSCLC patients with ERCC1-deficient tumours.

Applicability of the MoCA-S test in populations with little education in Colombia

OBJECTIVES

The objectives of this study were to report on the use of the Spanish version of the Montreal Cognitive Assessment (MoCA-S) as cognitive screening tool in a population aged 65 to 74 years in the Andes Mountains of Colombia, assessing the influence of education, and to examine its test-retest reliability.

METHODS

We performed a cross-sectional study of 150 subjects aged 65 to 74 years recruited from older community social centers in Manizales, Colombia. The Leganes Cognitive Test (LCT), a cognitive screening test for populations with low education, was used to exclude those who were likely to have dementia. The associations between the MoCA total score and cognitive domains and education were examined in the total sample and in those likely free of dementia. MoCA-S test-retest reliability was estimated by the intraclass correlation coefficient (ICC) between two measurements taken 7 days apart.

RESULTS

Participants had low levels of formal education (mean years of schooling, 4.8). According to the LCT, the proportion of people screening positive for dementia was 16% (n = 24). The mean MoCA-S scores were 16.1/30 among illiterate subjects, 18.2/30 among those with incomplete primary school, and 20.3/30 among those with complete primary school (p < 0.001). Errors were frequent in the cube and clock drawing, attention-serial subtraction, verbal fluency, and abstraction. Test-retest reliability was high, ICC = 0.86, 95% CI (0.76-0.93).

CONCLUSION

The MoCA-S has high reliability in low-educated older Colombians, but scores were strongly dependent on years of education. Social and cultural factors must be considered when interpreting MoCA-S given the high error rates on items that depend on the ability to read and write and on culture.

Hypernatraemic dehydration in Jamaican breastfed neonates: a 12-year review in a baby-friendly hospital

A 12-year retrospective review of neonates admitted with hypernatraemic dehydration to the neonatal unit of the University Hospital of the West Indies was conducted between 1 January 1990 and 31 December 2001. Twenty-four infants fulfilled the criteria for hypernatraemic dehydration. Nineteen (79%) women were either nulliparous or primiparous with a mean (SD) age of 26.9 (4.4) yrs. Modal length of hospital stay for mothers was 24 hrs. Twenty (83.3%) infants were exclusively breastfed. Mean (SD) age at presentation was 7.4 (3.8) days. Mean (SD) percentage weight loss between birth and presentation was 18.9% (6.3). Mean (SD) serum sodium at presentation was 164.8 (13.9) mmol/L. Babies visited at home by nurses had a lower mean serum sodium, were less dehydrated and were significantly less acidiotic. Their mean (SD) length of hospital stay was also significantly less [4.2 (1.4) days] than those who were not visited [7.9 (3.8) days] (p < 0.05). Complications occurred in 19 (79%) of infants and included renal failure (19, 79%), seizures (3, 13%) and intraventricular haemorrhage (1, 4%), and one died (4%). Hypernatraemic dehydration is an uncommon complication of failure to establish breastfeeding but is associated with severe morbidity and mortality. Education programmes are needed to increase awareness amongst health-care workers and mothers in order to prevent the problem.

Cytosine-based nucleoside analogs are selectively lethal to DNA mismatch repair-deficient tumour cells by enhancing levels of intracellular oxidative stress

BACKGROUND

DNA mismatch repair deficiency is present in a significant proportion of a number of solid tumours and is associated with distinct clinical behaviour.

METHODS

To identify the therapeutic agents that might show selectivity for mismatch repair-deficient tumour cells, we screened a pair of isogenic MLH1-deficient and MLH1-proficient tumour cell lines with a library of clinically used drugs. To test the generality of hits in the screen, selective agents were retested in cells deficient in the MSH2 mismatch repair gene.

RESULTS

We identified cytarabine and other related cytosine-based nucleoside analogues as being selectively toxic to MLH1 and MSH2-deficient tumour cells. The selective cytotoxicity we observed was likely caused by increased levels of cellular oxidative stress, as it could be abrogated by antioxidants.

CONCLUSION

We propose that cytarabine-based chemotherapy regimens may represent a tumour-selective treatment strategy for mismatch repair-deficient cancers.

Integrative molecular and functional profiling of ERBB2-amplified breast cancers identifies new genetic dependencies

Overexpression of the receptor tyrosine kinase ERBB2 (also known as HER2) occurs in around 15% of breast cancers and is driven by amplification of the ERBB2 gene. ERBB2 amplification is a marker of poor prognosis, and although anti-ERBB2-targeted therapies have shown significant clinical benefit, de novo and acquired resistance remains an important problem. Genomic profiling has demonstrated that ERBB2+ve breast cancers are distinguished from ER+ve and 'triple-negative' breast cancers by harbouring not only the ERBB2 amplification on 17q12, but also a number of co-amplified genes on 17q12 and amplification events on other chromosomes. Some of these genes may have important roles in influencing clinical outcome, and could represent genetic dependencies in ERBB2+ve cancers and therefore potential therapeutic targets. Here, we describe an integrated genomic, gene expression and functional analysis to determine whether the genes present within amplicons are critical for the survival of ERBB2+ve breast tumour cells. We show that only a fraction of the ERBB2-amplified breast tumour lines are truly addicted to the ERBB2 oncogene at the mRNA level and display a heterogeneous set of additional genetic dependencies. These include an addiction to the transcription factor gene TFAP2C when it is amplified and overexpressed, suggesting that TFAP2C represents a genetic dependency in some ERBB2+ve breast cancer cells.

Estimating the balance between pasture feed supply and demand of grazing livestock in a farmlet experiment

Data from the Cicerone farmlet study were used to quantify the balance between pasture feed supply and the demand from grazing livestock, in terms of metabolisable energy (ME), on three differently managed farmlets (each of 53 ha) on the Northern Tablelands of New South Wales, Australia. Farmlet A had a high level of pasture renovation and higher soil fertility than the other two farmlets and employed flexible grazing management over eight paddocks. Farmlet B was designed to represent management ‘typical’ of the region and had the same grazing management and number of paddocks as farmlet A but moderate levels of pasture renovation and soil fertility. The third farmlet (C) had the same level of inputs as farmlet B but practised intensive rotational grazing over 37 paddocks. Regular measurements of the feed supply, namely herbage mass and quality, pasture growth and supplement fed and of feed demand were assembled to provide monthly estimates of the balance between feed supply and animal demand of all classes of livestock run on the experiment over its duration of 6.5 years. The significantly greater stocking rate, liveweight and reproductive rate of sheep reached on the higher input system (farmlet A) meant higher levels of ME were required to satisfy the nutritional demands of these animals. As only limited measurements were taken of animal intake, it was assumed that the supply of ME was derived from pasture growth and supplement fed. Using key livestock management dates and measurements of liveweights, the changes in the energy requirements of each class of animal were calculated and aggregated to provide an estimate of overall livestock energy demand over time. Subtracting the energy demand from the estimated energy supply provided a partial net energy balance. Measurements of the rates of change of green herbage during grazing events were found to be highly dependent on stock density with farmlets A, B and C recording rates of change of up to –50, –30 and –200 green DM/ha.day, respectively. Over a series of generally drier-than-average years, the ME supplied in pasture growth and through supplementation was at times inadequate to meet the energy demands of the livestock, resulting in periods during winter when the partial energy balance became negative. Similar feed deficits were observed for all three farmlets, suggesting that they were over-stocked to a similar extent. In spite of the divergence in the stocking rate supported by each farmlet, the similarity of the ME balances between farmlets suggests that no farmlet was subjected to bias because of decisions relating to feed supply and demand. The analyses presented suggest there is considerable potential for practical paddock and grazing management to be improved if more timely and regular assessments can be made of changes in the feed energy supply using satellite images of normalised difference vegetation indices and feed energy demand using calculations of the ME required by grazing livestock.

Abstract PD05-08: Genomic characterisation of invasive breast cancers with heterogeneous HER2 gene amplification

Aims: HER2 gene amplification is observed in up to 15% of breast carcinomas. In a rare subset of breast cancers classified as HER2-positive by immunohistochemistry and in situ hybridisation, HER2 overexpression and gene amplification are restricted to a subset of &gt;30% but not all cancer cells. Here we sought to characterise the repertoire of gene copy number aberrations and somatic mutations in the HER2-positive and HER2-negative components of cases with heterogeneous HER2 overexpression and gene amplification.

Material and methods: Cases diagnosed as HER2 positive but with &gt;30% but &lt;100% of cells displaying HER2 overexpression were retrieved from the authors' institutions. HER2 heterogeneity status was re-assessed using immunohistochemistry and chromogenic and/ or fluorescence in situ hybridisation. For cases with confirmed HER2 gene amplification heterogeneity, HER2-positive and HER2-negative components were microdissected from tissue sections stained with the Herceptest antibody. DNA samples extracted from both components of each case were subjected to microarray-based comparative genomic hybridisation (aCGH), using a 32K BAC array platform with 50Kb resolution. The HER2-positive and HER2-negative components of cases with frozen material were also subjected to massively parallel targeted exome sequencing.

Results: Twelve cases yielded sufficient DNA for aCGH analysis. Tumours were preferentially ER positive (83%) and of histological grade 3 (67%). The HER2-positive and HER2-negative components of all cases shared most of the copy number aberrations. A pairwise comparison of the genomic profiles of the two components from each case revealed that in ten of the twelve cases, copy number aberrations in addition to 17q12 amplification encompassing the HER2 gene locus were restricted to one of the two components. Exome sequencing of two cases suggested that the HER2-positive and HER2-negative components from each case harboured &gt;30 somatic mutations in common, including identical TP53 somatic mutations in both components of each case. The HER2-negative component of one of the cases displayed a somatic mutation in NRG2, an ERBB receptor ligand, and the HER2-negative component of the other case harboured a mutation in PTTG1IP, a proto-oncogene with putative oestrogen receptor elements.

Conclusions: Our results demonstrate that in HER2-positive breast cancers with heterogeneous HER2 gene amplification, the HER2-positive and HER2-negative components are clonally related. The distinct genomic profiles of HER2-positive and HER2-negative components, however, suggest that, at least in some of these cases, HER2 amplification may constitute a relatively late event in tumour evolution. Exome sequencing revealed mutations restricted to the HER2-negative components of HER2-positive tumours with heterogeneous HER2 overexpression/gene amplification, which may constitute potential drivers in the absence of HER2 overexpression/gene amplification.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD05-08.

Is a small muscle mass index really detrimental for insulin sensitivity in postmenopausal women of various body composition status?

OBJECTIVES

We sought to determine if a small muscle mass index (MMI) is actually detrimental for insulin sensitivity when studying a large group of postmenopausal women displaying various body composition statuses and when age and visceral fat mass (VFM) are taken into account.

METHODS

A cross-sectional study was conducted in 99 healthy postmenopausal women with a BMI of 28±4 kg/m(2). Fat mass and total fat-free mass (FFM) were obtained from DXA and VFM and MMI were estimated respectively by the equation of Bertin and by: Total FFM (kg)/height (m)(2). Fasting plasma insulin and glucose were obtained to calculate QUICKI and HOMA as an insulin sensitivity index.

RESULTS

Total MMI and VFM were both significantly inversely correlated with QUICKI and positively with HOMA even when adjusted for VFM. A stepwise linear regression confirmed Total MMI and VFM as independent predictors of HOMA and plasma insulin level.

CONCLUSIONS

A small muscle mass might not be detrimental for the maintenance of insulin sensitivity and could even be beneficial in sedentary postmenopausal women. The impact of muscle mass loss on insulin sensitivity in older adults needs to be further investigated.

Femtosecond laser ablation ICP-MS measurement of otolith Sr:Ca and Ba:Ca composition reveal differential use of freshwater habitats for three amphidromous Sicyopterus (Teleostei: Gobioidei: Sicydiinae) species

The use of freshwater habitats was examined in three amphidromous goby species of the genus Sicyopterus using otolith microchemistry. Two species were endemic to either New Caledonia or Vanuatu whilst the other was widely distributed. Depositional patterns of strontium (Sr) and barium (Ba) in the otolith of adults were analysed with femtosecond laser ablation inductively coupled plasma mass spectrometry (ICP-MS). The Sr:Ca and Ba:Ca results uncovered three different adult behaviours within the freshwater habitat. Some fishes stayed in elevated locations (square profile); others undertook back-and-forth migrations between higher and lower reaches (up-and-down profile), and finally, others stayed in the lower reaches (constant profile). The consequences of these movements to larval survival or competition for food and territory are discussed. This work brings new knowledge on amphidromous behaviour, and it highlights the necessity of multi-elemental analysis to study amphidromy in freshwater systems.

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

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

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

Establishment and characterisation of a new breast cancer xenograft obtained from a woman carrying a germline BRCA2 mutation

Background:

The BRCA2 gene is responsible for a high number of hereditary breast and ovarian cancers, and studies of the BRCA2 biological functions are limited by the lack of models that resemble the patient's tumour features. The aim of this study was to establish and characterise a new human breast carcinoma xenograft obtained from a woman carrying a germline BRCA2 mutation.

Methods:

A transplantable xenograft was obtained by grafting a breast cancer sample into nude mice. The biological and genetic profiles of the xenograft were compared with that of the patient's tumour using histology, immunohistochemistry (IHC), BRCA2 sequencing, comparative genomic hybridisation (CGH), and qRT–PCR. Tumour response to standard chemotherapies was evaluated.

Results:

Histological profile identified the tumour as a basal-like triple-negative breast cancer. Targeted BRCA2 DNA sequencing of the xenograft showed the presence of the mutation previously identified in the carrier. Comparative genomic hybridisation array profiles of the primary tumour and the xenograft revealed a high number of similar genetic alterations. The therapeutic assessment of the xenograft showed sensitivity to anthracyclin-based chemotherapy and resistance to docetaxel. The xenograft was also highly sensitive to radiotherapy and cisplatin-based treatments.

Conclusions:

This study describes a new human breast cancer xenograft obtained from a BRCA2-mutated patient. This xenograft provides a new model for the pre-clinical drug development and for the exploration of the drug response biological basis.

Measuring indices of lifelong estrogen exposure: self-report reliability

OBJECTIVE

The utility of clinical markers of lifelong estrogen exposure is established in the understanding of breast cancer, osteoporosis and dementia, among others. However, a good number of studies rely on self-reports to ascertain the involvement of certain estrogen exposure indices. The goal of this study is to assess the reliability of self-reported lifelong estrogen exposure indices by measuring correlation between two repeats.

METHODS

A questionnaire assessing lifelong indices of estrogen exposure was developed (revised version included) and completed by 36 healthy postmenopausal women twice within a 4-year interval (age range from 50 to 79 years). Reliability was tested using Pearson's correlation coefficient.

RESULTS

Strong significant correlations were observed for most estrogen exposure indices and an effect of age was revealed. Age at menopause and age at initiation of hormone therapy were the two variables leading to weaker correlations across time of measurements; no relation was found between Time 1 and Time 2 when looking at the group of older women (over 65 years of age).

CONCLUSIONS

Overall, these results support the use of self-reported measures for most of the lifelong estrogen exposure indices, but they also warn us about the pitfalls of the climacteric period. However, the design of the current study did not allow us to test accuracy; thus, the validity of these self-reported variables needs to be addressed in the future.

Targeting Tankyrase 1 as a therapeutic strategy for BRCA-associated cancer

The BRCA1 and BRCA2 proteins are involved in the maintenance of genome stability and germ-line loss-of-function mutations in either BRCA1 or BRCA2 strongly predispose carriers to cancers of the breast and other organs. It has been demonstrated previously that inhibiting elements of the cellular DNA maintenance pathways represents a novel therapeutic approach to treating tumors in these individuals. Here, we show that inhibition of the telomere-associated protein, Tankyrase 1, is also selectively lethal with BRCA deficiency. We also demonstrate that the selectivity caused by inhibition of Tankyrase 1 is associated with an exacerbation of the centrosome amplification phenotype associated with BRCA deficiency. We propose that inhibition of Tankyrase 1 could be therapeutically exploited in BRCA-associated cancers.

RNA interference screening demystified

Genetic screens, where the effects of modifying gene function on cell behaviour are assessed in a systematic fashion, have for some time provided useful information to those interested in disease pathogenesis and treatment. Genetic screens exploiting the phenomenon of RNA interference (RNAi) are now becoming commonplace. This article explains the different RNAi screen formats and describes some of the applications of RNAi screening that may be pertinent to the research pathologist.

Stress in Women with Postpartum Obsessive-compulsive Disorder: A Neuroimaging Study

Objective:

Postpartum onset of anxiety disorders, particularly of obsessive-compulsive disorder (OCD) are rarely reported in the literature although frequently observed in the clinical setting. The obsessions and compulsions focus on the newborn and create immense distress. Research on the stress response in postpartum psychiatric populations is limited and the neural and neuroendocrine correlates of postpartum OCD is unclear. Few studies investigated the brain circuitry involved in OCD, very few included women and none in the postpartum period, and none of which focus on the stress reactivity underlying network.

The purpose of this study is to examine neural activation in women with postpartum OCD as compared to healthy postpartum women in response to a stress task using functional magnetic resonance imaging (fMRI).

Method:

Subjects are females diagnosed with postpartum OCD and matched healthy controls. During the stress phase, fMRI is recorded to observe brain activity while subjects complete the Montreal Imaging Stress Task (MIST), a psychological stressor. Saliva samples are obtained before and after the stressor to assess the hormonal stress response along with subjective stress rating.

Results:

To date, 9 postpartum OCD women and 10 controls completed the study. Preliminary analyses show that the majority of the subjects demonstrated an increase in subjective stress rating with postpartum OCD women experiencing the MIST more stressful compared to controls. As previously reported we observed deactivation throughout the limbic system in all subjects but only the postpartum OCD women also recruited the orbitofrontal cortex.

Conclusion:

These preliminary observations are consistent with the literature and point toward a distinct stress brain activation pattern in postpartum OCD women. It is hoped that the results of this study will provide further insight into the nature of neurophysiological and neuroendocrinological involvement in postpartum OCD.

Predictors of survival in very low birth weight infants at the University Hospital of the West Indies, Jamaica

The use of prenatal steroids is an effective, simple clinical intervention that can be implemented in developing countries to help decrease mortality in very low birth weight infants.

Outcome of extremely low birthweight infants at the University Hospital of the West Indies, Jamaica

OBJECTIVE

To describe the early outcome of extremely low birthweight infants delivered at the University Hospital of the West Indies.

METHODS

A two-year retrospective review of the charts of all live, inborn extremely low birthweight infants admitted to the neonatal unit between January 1, 2002 and December 31, 2003 was conducted Differences between survivors and non-survivors were determined using analysis of variance and predictors of outcome were determined using multiple regression models.

RESULTS

During the study period, 47 extremely low birthweight infants were admitted to the neonatal unit. The mean +/- SD birthweight and gestational age of these infants were 780 +/- 137 g and 27 +/- 2 weeks respectively. Twenty (43%) infants survived Babies (19; 58%) of gestational age > or = 27 weeks had increased survival compared to those < 27 weeks, (1; 7%; p = 0.001) and babies weighing > or = 750 g had increased survival (17, 65%) compared to those weighing < 750 g, (3, 14%; p < 0.001). Infants delivered by Caesarean section had improved survival 15 (58%) over those delivered vaginally (5, 24%; p = 0.02). All six (100%) infants whose mothers did not receive prenatal steroids died while 18 (50%) infants whose mothers received prenatal steroids died (p = 0.02). Significant factors associated with outcome were offered and gender was entered into a multiple regression model; gestational age and female gender remained independent predictors of survival.

CONCLUSION

Obstetric measures for the prevention of preterm delivery need to be optimized in order to decrease the morbidity and mortality associated with extremely low birthweight infants.