FOXC1 overexpression is a marker of poor response to anthracycline-based adjuvant chemotherapy in sporadic triple-negative breast cancer

Purpose

Because of its aggressive characteristics and poor prognosis, triple-negative breast cancer (TNBC) has become a hot topic in cancer research. Chemotherapy is currently the only treatment for patients with TNBC. The transcription factor FOXC1 has been associated with TNBC prognosis, but little is known about its effect on chemosensitivity. The aim of this study was to investigate the effects of FOXC1 on chemosensitivity.

Methods

A case–control study was performed on 25 TNBC patients who experienced relapse and/or metastasis. Another 25 patients without relapse or metastasis were randomly selected as controls. Medical records were reviewed for relevant information, and immunohistochemistry was performed to measure FOXC1 levels. The Kaplan–Meier method and Cox analysis were used to analyze differences in disease-free survival (DFS) and overall survival (OS). The correlation of FOXC1 expression with chemosensitivity was analyzed. Data were analyzed using SPSS 21.0 software, and a P value <0.05 was considered to be statistically significant.

Results

In 15 of 22 case patients, FOXC1 was overexpressed, whereas only 8 control patients exhibited FOXC1 overexpression (P < 0.05). FOXC1 expression had no correlation with pathological indicators. An anthracycline-based regimen was administered to 21 study patients and 23 control patients. FOXC1 expression was significantly associated with a worse DFS (HR 2.62, 95% CI 1.05–6.50, P = 0.038) but presented no correlation with OS (HR 2.53, 95% CI 0.76–8.40, P = 0.131) among these 44 patients.

Conclusions

This study shows that FOXC1 is correlated with chemosensitivity to anthracycline and could be used as an indicator of chemosensitivity in sporadic TNBC.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-017-3319-4) contains supplementary material, which is available to authorized users.

S phase arrest in lymphocytes induced by urinary 1-hydroxypyrene and alcohol drinking in coke oven workers

Arrest of the cell cycle after DNA damage is believed to promote DNA repair. We aim to investigate the main factors affecting cell cycle arrest of lymphocytes in coke oven workers. A total of 600 workers were included in this study, and their urinary levels of four polycyclic aromatic hydrocarbons (PAH) metabolites, 8-hydroxydeoxyguanosine (8-OHdG), and cell cycle distribution were determined. Urinary PAH metabolites were significantly increased in coke oven workers ( p < 0.01). It was found that only urinary 2-hydroxynaphthalene and 1-hydroxypyrene showed significant positive linear dose–response effects on 8-OHdG in this study population ( ptrend = 0.025 and 0.017, respectively). The dose–response effect was also observed for smoking and drinking on 8-OHdG ( ptrend < 0.001 and 0.034, respectively). Multivariate logistic regression analysis revealed that high levels of urinary 1-hydroxypyrene were associated with a significantly increased risk of S phase arrest (odds ratio (OR) = 1.32, p = 0.03), so as heavy alcohol drinking (OR = 1.31, p = 0.02). Drinking can significantly modify the effects of urinary 1-hydroxypyrene on S phase arrest, during co-exposure to both heavy drinking and median or high 1-hydroxypyrene levels (OR = 3.31, 95% confidence interval (CI) = 1.21–7.63 and OR = 2.56, 95% CI = 1.08–6.06, respectively). Our findings demonstrate that coke oven workers with heavy drinking will cause S phase arrest so as to repair more serious DNA damage.

Abstract P5-02-05: Biology and long-term prognosis of screening detected non-palpable breast cancer by ultrasound in hospital-based Chinese population (2001-2014)

Background: Milestone studies showed that ultrasound (US) was an effective primary screening test for breast cancer both in the western world and in China [PMID: 26712110, 26715161, and 25668012]. Ultrasound has been officially designated to be the initial imaging test for breast cancer screening in Beijing and several other cities in China, due to its improved sensitivity in Chinese women who usually have denser breasts and develop breast cancer earlier than Caucasian counterparts. Study showed that it would take 40 years to screen each woman in the target age group once [PMID: 26808342].The mainstay modality of breast cancer screening in China is the hospital-based opportunistic screening among asymptomatic self-referred women. However, there is little data about the tumor biology and long-term survival of the US-detected non-palpable breast cancer (NPBC) in hospital-based Chinese population.

Methods: From January 2001 to December 2014, 3,786 asymptomatic women with positive (BI-RADS 4 and 5) initial screening US underwent biopsies in Peking Union Medical College Hospital, and 572 NPBC in 556 women were diagnosed. Women without dense breasts (defined as BI-RADS category C and D) also received screening mammography (MG) after physical examination and ultrasound. 788 patients with positive (BI-RADS 4 and 5) mammogram (MG) and normal US (BI-RADS 1, 2 and 3) underwent MG-guided biopsies and another 127 NPBC were diagnosed in 126 women. The clinicopathological features, treatment choice, 10-year disease-free survival (DFS) and overall survival (OS) were reviewed and compared between the US-detected and MG-detected NPBC. Prognostic factors of NPBC were identified.

Results: Overall, US could detect more invasive NPBC (83.4% vs 54.3%, p&lt;0.001), lymph node positive cancer (19.1% vs 10.2%, p&lt;0.001)and multifocal cancer (19.2% vs 6.3%, p&lt;0.001). In invasive NPBC, US detected more low grade cancer (21.4% vs 10.2%, p=0.001), multifocal cancer (20.7% vs 2.9%, p&lt;0.001), Her2 negative cancer (77.6% vs 62.3%, p=0.001) and larger tumor (pT1c+pT2, 53.3% vs 37.6%, p&lt;0.001). There was no significant difference in immunophenotype/subtype, treatment methods, DFS or OS between US- and MG-NPBC among ductal carcinoma in situ (DCIS), invasive and all NPBC. For all NPBC and the US-NPBC, the common DFS-factors included pT, pN and p53 whereas OS-predictors were pN and immunophenotype/subtype.

Table 1. Kaplan-Meier estimates of DFS and OS between US-NPBC and MG-NPBC§.Patients (No.)10-year DFS (%)P value10-year OS (%)P valueAllUS-NPBC (572)90.60.73896.10.142 MG-NPBC (127)92.7 100.0 DCISUS-NPBC (94)100.00.060100.0- MG-NPBC (58)93.8 100.0 InvasiveUS-NPBC (478)88.60.68095.20.239 MG-NPBC (69)92.0 100.0 § Kaplan-Meier survival curves between each two subgroups would be displayed in the poster.

Conclusion: Compared to MG, US detected more invasive NPBC with positive lymph node in hospital-based asymptomatic self-referred Chinese women, who could achieve comparable 10-year DFS and OS as MG-detected NPBC. US could serve as the feasible initial imaging modality in hospital-based opportunistic screening Chinese women.

Citation Format: Yao R, Pan B, Zhu Q, Xu Q, Zhou Y, Zhang J, Mao F, You S, Lin Y, Shi J, Guan J, Wang X, Zhang Y, Zhang X, Shen S, Zhong Y, Xu Y, Liang Z, Jiang Y, Sun Q. Biology and long-term prognosis of screening detected non-palpable breast cancer by ultrasound in hospital-based Chinese population (2001-2014) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-02-05.

Malignant pericardial mesothelioma : A systematic review of current practice

BACKGROUND

Malignant mesothelioma is a rare but aggressive tumor, with a high misdiagnosis rate and overall bleak prognosis. In 0.7% of all cases, the origin is the pericardium.

METHODS

The present study is a review of the literature published in recent decades focusing on the advances in clinical manifestations, radiological findings, diagnosis, differential diagnosis, and treatment of malignant pericardial mesothelioma (MPM).

RESULTS

No clear relationship has been established between the etiologies and the development of MPM. Clinical symptoms and signs are nonspecific when present. The main presentations are chest pain and dyspnea. Imaging plays an important role in the detection, characterization, staging, and posttreatment follow-up. The definitive diagnosis is made on the basis of pathological findings. Chest radiography and echocardiography are common techniques used initially, but their roles are limited. Computed tomography and magnetic resonance imaging have an advantage in depicting the thickened pericardium, mediastinal lymph node, tumor, and the extension of adjacent structures. Surgery is the most important treatment modality and remains palliative in most cases, while the roles of chemo- and radiotherapy are unsatisfactory.

CONCLUSION

Clinical trials of malignant pleural and peritoneal mesothelioma remain important for MPM management. Multimodality treatment of surgery, chemotherapy, radiotherapy, and immunotherapy is expected to have a role in the treatment of MPM.

Diastolic dysfunction and cardiac troponin I decrease in aging hearts

Cardiac tropnoin I (cTnI) plays a critical role in the regulation of diastolic function, and its low expression may result in cardiac diastolic dysfunction, which is the most common form of cardiovascular disorders in older adults. In this study, cTnI expression levels were determined in mice at various ages and cardiac function was measured and compared between young adult mice (3 and 10 months) and older mice (18 months). The data indicated that the cTnI levels reached a peak high in young adult hearts (3 months), but decreased in older hearts (18 months). Furthermore, the older hearts showed a significant diastolic dysfunction observed by P-V loop and echocardiography measurements. To further define the mechanism underlying the cTnI decrease in aging hearts, we tested DNA methylation and histone acetylation modifications of cTnI gene. We found that acetylation of histone near the promoter region of cTnI gene played an important role in regulation of cTnI expression in the heart at different ages. Our study indicates that epigenetic modification caused cTnI expression decrease is one of the possible causes that result in a reduced cTnI level and diastolic dysfunction in the older hearts.

Abstract P6-08-03: Functional detection and inhibition of the targetable oncogenic kinome of chemotherapy-treated triple-negative breast cancer cells

Background: Triple-negative breast cancer (TNBC) accounts for 10-15% of all breast cancer cases. A major area of innovation in TNBC is identifying potential treatment targets, especially in TNBC cells which survive chemotherapy. Our previous study showed that TNBC cells displayed deregulated kinase-dependent signaling cascades, and uniquely divergent phospho-circuits could be distinguished between TNBC vs non-TNBC cell lines [2014 SABCS abstract 1672, poster P2-05-09]. We further hypothesized that specific dysfunctional phospho-signaling network played a key role in the early adaptive changes in DNA damage response of TNBC cells exposed to DNA damaging chemotherapeutic agents.

Methods: TNBC cell lines MDA-MB-231 and MDA-MB-436 were treated with 5-fluorouracil (5-Fu), carboplatin and doxorubicin at their respective half maximal inhibitory concentrations (ic50s). MiSeq gene sequencing of the untreated vs treated TNBC cells was performed to investigate whether exposure to chemotherapy agents for 3-day's duration would induce additional adaptive genetic mutation. Apoptosis and cell-cycle distribution of the untreated and treated TNBC cells were analyzed with flow cytometry. The functional phospho-signature of each TNBC cell sample was analyzed using a high throughput experimental platform that monitors the level of activity of myriad kinases at once. This technique used over 450 phospho-sensing probes, including over 150 controls in an aqueous-based assay to simultaneously and directly measure the phospho-catalytic activity of phosphorylating enzymes in cell lysates. The kinome activities of the untreated vs treated TNBC cell lines were compared respectively, and the most significantly deranged and functionally altered phospho-signaling cascades and their related kinases were identified as the early adaptive changes of the survived TNBC cells after the 3-day exposure to DNA damage chemotherapies.

Results: Using the two TNBC cell lines treated with the three chemotherapies, we made 8 cell line samples, including 6 treated and 2 untreated as the control. MiSeq gene sequencing showed no significant additional adaptive genetic mutations in the treated TNBC cells after the 3-day short-term exposure to 5-Fu, carboplatin and doxorubicin. 36 phospho-signatures were generated and validated for repeatability and robustness. The kinase activity signature of each TNBC sample was analyzed and compared to each other using unsupervised hierarchical clustering. The phospho-sensing assay revealed that phospho-signaling cascades related to CHK1/2 and IKK kinases were differentially altered in the untreated vs treated TNBC cell lines, which, when respectively inhibited by AZD7762 and IKK16, successfully increased growth inhibition and cell death of TNBCs.

Conclusions: We identified specific phospho-fingerprints of the early adaption of TNBC cell lines and combinatorial targeted therapies that improve treatment outcome. Our next goal is to identify specific phosphorylation cascades in a broader range of cell lines and tumor tissues, to explore the actionable, kinase-dependent mechanisms critical to the DNA damage-induced adaptive reprogramming of TNBCs and early changes driving drug-resistance.

Citation Format: Pan B, Olow A, Sun Q, Mori M, Lee PRE, Hartog M, Wang C, Wolf D, Yau C, van 't Veer L, Coppé J-P. Functional detection and inhibition of the targetable oncogenic kinome of chemotherapy-treated triple-negative breast cancer 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 P6-08-03.

Abstract P6-05-12: Prognosis of subtypes of the mucinous breast carcinoma in Chinese women: A population-based study of 32-year experience (1983-2014)

Background: The heterogeneous nature of the mucinous breast cancer (MBC), with its subtypes of pure (PMBC) and mixed carcinoma (MMBC), calls for more precise individualized prognosis assessment. PMBC showed favorable prognosis in both Chinese and Caucasian women, with nodal status and TNM stage as the prognostic predictors [PMID: 18026874, 22451233]. However, few studies had investigated tumor biology and prognosis of MMBC in Chinese population, especially with respect to the different co-existing cancer components.

Methods: From January 1983 to December 2014, 197 consecutive MBC patients, including 117 PMBC and 80 MMBC, received breast cancer surgery in Peking Union Medical College Hospital. The clinicopathological characteristics, treatment choice, disease-free survival (DFS) and overall survival (OS) were compared both between PMBC vs MMBC, and among subgroups of MMBC according to the mixed entities, including 24 women with ductal caricinoma in situ (DCIS) and 45 with IDC. Univariate and Cox multivariate analyses were performed to identify the prognostic factors.

Results: The 197 MBC comprised 1.9% of contemporary 10,192 breast cancer (BC). Compared to PMBC, MMBC had significantly more lymph node metastasis (p=0.038), Her2 positivity (p=0.036), high Ki-67 index (defined as &gt;20%, p=0.026) and anti-Her2 targeted therapy (p=0.006). All these differences remained significant when the comparison were performed among PMBC, MBC+DCIS and MBC+IDC, and additional significant difference were identified in tumor size (p=0.036), pTNM stage (p=0.003) and chemotherapy (p=0.003). However, no significant difference was found in DFS or OS between any two subtypes/subgroups of MBC, including PMBC, MMBC, MBC+DCIS and MBC+IDC.

Table 1. Comparison of survival outcomes among PMBC, MBC+DCIS and MBC+IDC§SurvivalPMBC (N=117, Median, range, and Mean±SD)MBC+DCIS (N=24, Median, range, and Mean±SD)MBC+IDC (N=45, Median, range, and Mean±SD)P-ValueDFS (months)43 (1-233), 52.7±45.227 (1-84), 34.3±25.326 (1-113), 33.1±26.60.187OS (months)46 (1-312), 56.9±51.827 (1-84), 34.4±25.326 (1-113), 34.8±28.70.628§ Kaplan-Meier survival curves would be displayed in the poster

High Ki-67 index (p=0.046) appeared to be the significant DFS related prognostic factor for PMBC, whereas estrogen receptor (ER) status (univariate p=0.000, multivariate p=0.062) and immunophenotype (luminal, her2, or triple-negative, univariate p=0.000, multivariate p=0.079) might be the potential DFS predictors for MMBC. None of the above-mentioned clinicopathological factors could serve as OS predictors for MBC.

Conclusion: This population-based study showed that there were significant difference in nodal status, Ki-67, Her2 positivity and targeted therapy between PMBC and MMBC, and furthermore in tumor size, stage and chemotherapy among PMBC and subgroups of MMBC such as MBC+DCIS and MBC+IDC. However, survival outcomes were similar between these clinical entities and subgroups, suggesting the intra-tumoral heterogeneity might not interfere with survival outcomes of MBC in Chinese woman. High Ki-67 index was identified as the significant DFS related prognostic factor for PMBC, whereas ER status and immunophenotype as the potential DFS predictors for MMBC.

Citation Format: Yao R, Pan B, Sun Q, Zhou Y, Mao F, Lin Y, Guan J, Wang X, Zhang Y, Zhang X, Shen S, Zhong Y, Xu Y, Shi J, Zhu Q, Cai F, Liang Z. Prognosis of subtypes of the mucinous breast carcinoma in Chinese women: A population-based study of 32-year experience (1983-2014). [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 P6-05-12.

A common polymorphism rs1800247 in osteocalcin gene was associated with serum osteocalcin levels, bone mineral density, and fracture: the Shanghai Changfeng Study

We evaluated the relationship between a common polymorphism rs1800247 in osteocalcin gene and serum osteocalcin levels, bone mineral density and fracture in Chinese. This was a population-based cross-sectional study. We demonstrated that rs1800247 was associated with bone mineral density and fracture in men and serum osteocalcin levels in women.

INTRODUCTION

This study aimed to evaluate the relationship between a common polymorphism rs1800247 in osteocalcin gene and serum total osteocalcin levels, bone mineral density (BMD) and fracture in Chinese middle-aged and elderly men and women.

METHODS

This was a population-based cross-sectional study included 5561 individuals aged 45 years or older. Information on fractures sustained after age of 45 were collected. BMD at the lumbar spine, femoral neck and total hip were measured using dual-energy X-ray absorptiometry. The genotyping of rs1800247 was performed by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy.

RESULTS

rs1800247 was associated with lumbar spine BMD and femoral neck BMD in the dominant model adjusted for age, body mass index (BMI), serum total osteocalcin in men (both P = 0.04). Besides, rs1800247 was associated with fracture adjusted for age, BMI, serum total osteocalcin and total hip BMD in the additive and dominant models in men (P = 0.04 and 0.01). In the dominant model, the carriers of CC and TC genotypes was associated with a lower odds of fracture compared with the carriers of TT genotype (OR = 0.60, 95%CI 0.40-0.88, P = 0.01). In men, rs1800247 was not associated with serum total osteocalcin levels in additive, dominant or recessive models. However, rs1800247 was associated with serum total osteocalcin levels in all models adjusted for age, BMI, menopausal status and total hip BMD in women (all p < 0.001), with osteocalcin levels decreasing across TT, TC and CC genotypes. rs1800247 was not associated with BMD or fracture in all models in women.

CONCLUSIONS

A common polymorphism rs1800247 in osteocalcin gene may affect the risk of osteoporosis and fracture and serum total osteocalcin levels in Chinese, and there may be gender differences underlying these associations.

AMP-activated protein kinase regulates autophagic protection against cisplatin-induced tissue injury in the kidney

Although the nephrotoxicity of cisplatin has been well documented as a major side effect of chemotherapy, the exact mechanism by which prosurvival and apoptotic pathways interplay to determine renal pathology remains elusive. Recent studies suggested that autophagy might serve as an adaptive mechanism to promote cell survival during acute kidney injury (AKI). We have used AKI as a disease model to investigate the mechanism regulating the cytoprotective role of autophagy in cisplatin-induced tissue damage. Pharmacological inhibitors such as chloroquine were used to manipulate autophagy during AKI, and DNA damage was evaluated by using the cellular marker γH2AX. Cisplatin induced extensive DNA damage during AKI. Autophagy activation served as a survival strategy to suppress cisplatin-induced DNA damage in the pathology of AKI both in vitro and in vivo. Interestingly, in the kidney, cisplatin treatment can activate AMP-activated protein kinase (AMPK), a signaling molecule that is also critical for p53-mediated inactivation of mammalian target of rapamycin (mTOR) pathways. As a result, inhibition or knockdown of AMPK can lead to repressed autophagy in cisplatin-induced AKI, resulting in more DNA damage. Activation of AMPK regulates autophagy during cisplatin-induced AKI. Given the fact that p53 can regulate autophagy by inactivating mTOR via AMPK, our results suggest that the p53 pathway may also play a critical role in the pathogenesis of cisplatin-induced renal damage. This study may further our understanding of the physiological roles of autophagy in the pathogenesis of renal injuries, and thus may have pathological implications in the clinical setting.

Isolation of haemolytic bacilli from field-collected Culicoides oxystoma and Culicoides peregrinus: potential vectors of bluetongue virus in West Bengal, India

Two haemolytic bacterial strains of Bacillus pumilus (CU1A, CU1B) and one blood-utilizing strain of Bacillus licheniformis (CU2B) were isolated from relatively low numbers of field-collected females of Culicoides oxystoma and Culicoides peregrinus (Diptera: Ceratopogonidae). A total of 36 females, including 18 of each of C. oxystoma and C. peregrinus (consisting of one and a pool of eight blood-engorged specimens, and one and a pool of eight non-engorged specimens for each species), were tested. In C. oxystoma, all three strains of bacteria were isolated from the one non-engorged, the pool of non-engorged and the pool of blood-engorged females tested, but CU1A and CU2B were not found in the one blood-engorged female tested. In C. peregrinus, all three strains were present in the pool of blood-engorged females. However, the strain CU2B was not found in the pool of non-engorged females. In the one blood-engorged and one non-engorged female tested, CU1A and CU2B were detected. The bacterial strains were identified based on Gram staining, enzyme activity (amylase and protease) and alignment of the 16S rRNA partial gene sequence to that available in the National Center for Biotechnology Information (NCBI) database GenBank. The functional role and significance of these haemolytic and blood-digesting bacteria within the genus Culicoides remain to be determined.

Sustained relief of neuropathic pain by AAV-targeted expression of CBD3 peptide in rat dorsal root ganglion

The Ca²⁺ channel-binding domain 3 (CBD3) peptide, derived from the collapsin response mediator protein 2 (CRMP-2), is a recently discovered voltage-gated Ca²⁺ channel (VGCC) blocker with a preference for Ca_V2.2. Rodent administration of CBD3 conjugated to cell penetrating motif TAT (TAT-CBD3) has been shown to reduce pain behavior in inflammatory and neuropathic pain models. However, TAT-CBD3 analgesia has limitations, including short half-life, lack of cellular specificity and undesired potential off-site effects. We hypothesized that these issues could be addressed by expressing CBD3 encoded by high-expression vectors in primary sensory neurons. We constructed an adeno-associated viral (AAV) vector expressing recombinant fluorescent CBD3 peptide and injected it into lumbar dorsal root ganglia (DRGs) of rats before spared nerve injury (SNI). We show that selective expression of enhanced green fluorescent protein (EGFP)-CBD3 in lumbar 4 (L4) and L5 DRG neurons and their axonal projections results in effective attenuation of nerve injury-induced neuropathic pain in the SNI model. We conclude that AAV-encoded CBD3 delivered to peripheral sensory neurons through DRG injection may be a valuable approach for exploring the role of presynaptic VGCCs and long-term modulation of neurotransmission, and may also be considered for development as a gene therapy strategy to treat chronic neuropathic pain.

Buffering boys and boosting girls: The protective and promotive effects of Early Head Start for children's expressive language in the context of parenting stress

Children's characteristics, including gender, influence their development by eliciting differential responses from their environments, and by influencing differential responses to their environments. Parenting-related stress, associated with poverty environments, negatively influences children's language, likely through its impact on parent-child interactions, but may impact boys' and girls' development differently. Early intervention represents one tool for supporting development in at-risk toddlers, but gender-differences in effects of intervention are rarely described. The current studies assessed the effects of Early Head Start (EHS) on children's productive vocabulary in the context of parenting stress and examined gender differences in program effects on vocbulary. Data were from the national EHS Research and Evaluation (EHSRE) study (Study 1, N = 3,001), and from a dataset associated with one EHSRE site (Study 2, N = 146) where additional data on productive vocabulary were collected. Study 1 found that at 24 months of age, the EHS program protected girls' productive vocabulary from the negative effects of parenting stress, but had little impact on boys' vocabulary. In Study 2, the local EHS site promoted girls' vocabulary development over time from 14 to 36 months despite the negative effects of parenting stress, and protected boys' vocabulary from the negative parenting stress effects. These results suggest differential ways in which at-risk toddlers are affected by early intervention.

Permeation properties of the hair cell mechanotransducer channel provide insight into its molecular structure

Mechanoelectric transducer (MET) channels, located near stereocilia tips, are opened by deflecting the hair bundle of sensory hair cells. Defects in this process result in deafness. Despite this critical function, the molecular identity of MET channels remains a mystery. Inherent channel properties, particularly those associated with permeation, provide the backbone for the molecular identification of ion channels. Here, a novel channel rectification mechanism is identified, resulting in a reduced pore size at positive potentials. The apparent difference in pore dimensions results from Ca(2+) binding within the pore, occluding permeation. Driving force for permeation at hyperpolarized potentials is increased because Ca(2+) can more easily be removed from binding within the pore due to the presence of an electronegative external vestibule that dehydrates and concentrates permeating ions. Alterations in Ca(2+) binding may underlie tonotopic and Ca(2+)-dependent variations in channel conductance. This Ca(2+)-dependent rectification provides targets for identifying the molecular components of the MET channel.

Abstract IA24: Drugging the undruggable: Small-molecule inhibition of Ras oncoprotein

Ras is a nucleotide-dependent switch that converts from an inactive GDP-bound state to an active GTP-bound state when activated by guanine nucleotide exchange factors, such as SOS. Active RasGTP then binds to and activates downstream signaling effectors. Ras is the most frequently mutated oncogene and hyperactive mutant Ras constitutively signals to effectors to promote cell survival, proliferation and metastasis. Thus, Ras oncoprotein has been considered by the cancer community to be one of the most important oncology drug targets. Despite the enormous interest and extensive exploratory efforts in industry and academia, small molecules that bind to Ras in a well-defined manner and exert inhibitory effects have not been uncovered to date. We report here the identification and characterization of small-molecule inhibitors of the Ras oncoprotein.

To explore a new means of directly targeting Ras, we used a fragment-based lead discovery approach via an NMR-based screen. Hits from the fragment screen were characterized for their interactions with Ras by NMR and X-ray crystallography and for their effects on Ras activation and signaling in reconstituted biochemical assays in vitro and in cellular assays in vivo. From the fragment-based screen, we identified a group of small molecules that each bind to a common site adjacent to the switch I/II regions in the Ras protein. X-ray crystallography studies of three compound-Ras complexes indicate that the binding site can be expanded upon ligand binding. Nucleotide exchange factors, notably SOS, are required to convert inactive RasGDP to active RasGTP. We determined that the compound-binding site is located at the interface of Ras and SOS. A subset of our Ras-binding molecules indeed inhibited SOS-mediated nucleotide exchange. Further mechanistic studies revealed that through steric hindrance the compounds block the formation of the Ras-SOS complex, a key intermediate of the exchange reaction. At the cellular level, our compounds inhibit the formation of active RasGTP and prevent Ras signaling to downstream effectors. To define the potential clinic utility of these compounds, we performed biological characterization of Ras-driven tumors and identified a subset of Ras mutant tumors that depend on nucleotide exchange factors for the activation of Ras, suggesting a specific profile for the use of exchange inhibitors.

We conclude that the compounds act as competitive inhibitors of nucleotide exchange to prevent the activation of Ras. The discovery of a binding pocket on Ras with functional significance represents a breakthrough finding that will offer a new direction for therapeutic intervention of Ras. Our findings provide new opportunities to target the “undruggable” Ras oncoprotein.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr IA24.

Observation of the decay B- → D(s)((*)+) K- ℓ- ν(ℓ)

We report the observation of the decay B- → D(s)((*)+) K- ℓ- ν(ℓ) based on 342  fb(-1) of data collected at the Υ(4S) resonance with the BABAR detector at the PEP-II e+ e- storage rings at SLAC. A simultaneous fit to three D(s)(+) decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B- → D(s)((*)+) K- ℓ- ν(ℓ) with a significance greater than 5 standard deviations (including systematic uncertainties) and measure its branching fraction to be B(B- → D(s)((*)+) K- ℓ- ν(ℓ)) = [6.13(-1.03)(+1.04)(stat)±0.43(syst)±0.51(B(D(s)))]×10(-4), where the last error reflects the limited knowledge of the D(s) branching fractions.

Search for production of invisible final states in single-photon decays of Υ(1S)

We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A⁰, or a pair of dark matter particles, χχ. Both A⁰ and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π⁺π⁻Υ(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m(A⁰) ≤ 9.2 GeV and m(χ) ≤ 4.5 GeV in the sample of 98 × 10⁶ Υ(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.

Search for f(J)(2220) in radiative J/ψ decays

We present a search for f(J)(2220) production in radiative J/ψ→γf(J)(2220) decays using 460  fb⁻¹ of data collected with the BABAR detector at the SLAC PEP-II e(+)e⁻ collider. The f(J)(2220) is searched for in the decays to K(+)K⁻ and K(S)⁰K(S)⁰. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for J/ψ→γf(J)(2220) and f(J)(2220)→K(+)K⁻(K(S)⁰K(S)⁰) as a function of spin and helicity are set at the level of 10⁻⁵, below the central values reported by the Mark III experiment.