Fatty acid synthesis suppresses dietary polyunsaturated fatty acid use

Dietary polyunsaturated fatty acids (PUFA) are increasingly recognized for their health benefits, whereas a high production of endogenous fatty acids - a process called de novo lipogenesis (DNL) - is closely linked to metabolic diseases. Determinants of PUFA incorporation into complex lipids are insufficiently understood and may influence the onset and progression of metabolic diseases. Here we show that fatty acid synthase (FASN), the key enzyme of DNL, critically determines the use of dietary PUFA in mice and humans. Moreover, the combination of FASN inhibition and PUFA-supplementation decreases liver triacylglycerols (TAG) in mice fed with high-fat diet. Mechanistically, FASN inhibition causes higher PUFA uptake via the lysophosphatidylcholine transporter MFSD2A, and a diacylglycerol O-acyltransferase 2 (DGAT2)-dependent incorporation of PUFA into TAG. Overall, the outcome of PUFA supplementation may depend on the degree of endogenous DNL and combining PUFA supplementation and FASN inhibition might be a promising approach to target metabolic disease.

Pharmacological induction of membrane lipid poly-unsaturation sensitizes melanoma to ROS inducers and overcomes acquired resistance to targeted therapy

BACKGROUND

One of the key limitations of targeted cancer therapies is the rapid onset of therapy resistance. Taking BRAF-mutant melanoma as paradigm, we previously identified the lipogenic regulator SREBP-1 as a central mediator of resistance to MAPK-targeted therapy. Reasoning that lipogenesis-mediated alterations in membrane lipid poly-unsaturation lie at the basis of therapy resistance, we targeted fatty acid synthase (FASN) as key player in this pathway to evoke an exquisite vulnerability to clinical inducers of reactive oxygen species (ROS), thereby rationalizing a novel clinically actionable combination therapy to overcome therapy resistance.

METHODS

Using gene expression analysis and mass spectrometry-based lipidomics of BRAF-mutant melanoma cell lines, melanoma PDX and clinical data sets, we explored the association of FASN expression with membrane lipid poly-unsaturation and therapy-resistance. Next, we treated therapy-resistant models with a preclinical FASN inhibitor TVB-3664 and a panel of ROS inducers and performed ROS analysis, lipid peroxidation tests and real-time cell proliferation assays. Finally, we explored the combination of MAPK inhibitors, TVB-3664 and arsenic trioxide (ATO, as a clinically used ROS-inducer) in Mel006 BRAF mutant PDX as a gold model of therapy resistance and assessed the effect on tumor growth, survival and systemic toxicity.

RESULTS

We found that FASN expression is consistently increased upon the onset of therapy resistance in clinical melanoma samples, in cell lines and in Mel006 PDX and is associated with decreased lipid poly-unsaturation. Forcing lipid poly-unsaturation in therapy-resistant models by combining MAPK inhibition with FASN inhibition attenuated cell proliferation and rendered cells exquisitely sensitive to a host of ROS inducers. In particular, the triple combination of MAPK inhibition, FASN inhibition, and the clinical ROS-inducing compound ATO dramatically increased survival of Mel006 PDX models from 15 to 72% with no associated signs of toxicity.

CONCLUSIONS

We conclude that under MAPK inhibition the direct pharmacological inhibition of FASN evokes an exquisite vulnerability to inducers of ROS by increasing membrane lipid poly-unsaturation. The exploitation of this vulnerability by combining MAPK and/or FASN inhibitors with inducers of ROS greatly delays the onset of therapy resistance and increases survival. Our work identifies a clinically actionable combinatorial treatment for therapy-resistant cancer.

Therapeutic efficacy of FASN inhibition in preclinical models of HCC

BACKGROUND AND AIMS

Aberrant activation of fatty acid synthase (FASN) is a major metabolic event during the development of HCC. We evaluated the therapeutic efficacy of TVB3664, a FASN inhibitor, either alone or in combination, for HCC treatment.

APPROACH AND RESULTS

The therapeutic efficacy and the molecular pathways targeted by TVB3664, either alone or with tyrosine kinase inhibitors or the checkpoint inhibitor anti-programmed death ligand 1 antibody, were assessed in human HCC cell lines and multiple oncogene-driven HCC mouse models. RNA sequencing was performed to elucidate the effects of TVB3664 on global gene expression and tumor metabolism. TVB3664 significantly ameliorated the fatty liver phenotype in the aged mice and AKT-induced hepatic steatosis. TVB3664 monotherapy showed moderate efficacy in NASH-related murine HCCs, induced by loss of phosphatase and tensin homolog and MET proto-oncogene, receptor tyrosine kinase (c-MET) overexpression. TVB3664, in combination with cabozantinib, triggered tumor regression in this murine model but did not improve the responsiveness to immunotherapy. Global gene expression revealed that TVB3664 predominantly modulated metabolic processes, whereas TVB3664 synergized with cabozantinib to down-regulate multiple cancer-related pathways, especially the AKT/mammalian target of rapamycin pathway and cell proliferation genes. TVB3664 also improved the therapeutic efficacy of sorafenib and cabozantinib in the FASN-dependent c-MYC-driven HCC model. However, TVB3664 had no efficacy nor synergistic effects in FASN-independent murine HCC models.

CONCLUSIONS

This preclinical study suggests the limited efficacy of targeting FASN as monotherapy for HCC treatment. However, FASN inhibitors could be combined with other drugs for improved effectiveness. These combination therapies could be developed based on the driver oncogenes, supporting precision medicine approaches for HCC treatment.

TVB-2640 (FASN Inhibitor) for the Treatment of Nonalcoholic Steatohepatitis: FASCINATE-1, a Randomized, Placebo-Controlled Phase 2a Trial

BACKGROUND & AIMS

Increased de novo lipogenesis creates excess intrahepatic fat and lipotoxins, propagating liver damage in nonalcoholic steatohepatitis. TVB-2640, a fatty acid synthase inhibitor, was designed to reduce excess liver fat and directly inhibit inflammatory and fibrogenic pathways. We assessed the safety and efficacy of TVB-2640 in patients with nonalcoholic steatohepatitis in the United States.

METHODS

3V2640-CLIN-005 (FASCINATE-1) was a randomized, placebo-controlled, single-blind study at 10 US sites. Adults with ≥8% liver fat, assessed by magnetic resonance imaging proton density fat fraction, and evidence of liver fibrosis by magnetic resonance elastography ≥2.5 kPa or liver biopsy were eligible. Ninety-nine patients were randomized to receive placebo or 25 mg or 50 mg of TVB-2640 (orally, once-daily for 12 weeks). The primary end points of this study were safety and relative change in liver fat after treatment.

RESULTS

Liver fat increased in the placebo cohort by 4.5% relative to baseline; in contrast TVB-2640 reduced liver fat by 9.6% in the 25-mg cohort (n = 30; least squares mean: -15.5%; 95% confidence interval, -31.3 to -0.23; P = .053), and 28.1% in the 50-mg cohort (n = 28; least squares mean: -28.0%; 95% confidence interval, -44.5 to -11.6; P = .001). Eleven percent of patients in the placebo group achieved a ≥30% relative reduction of liver fat compared to 23% in the 25-mg group, and 61% in the 50-mg group (P < .001). Secondary analyses showed improvements of metabolic, pro-inflammatory and fibrotic markers. TVB-2640 was well tolerated; adverse events were mostly mild and balanced among the groups.

CONCLUSIONS

TVB-2640 significantly reduced liver fat and improved biochemical, inflammatory, and fibrotic biomarkers after 12 weeks, in a dose-dependent manner in patients with nonalcoholic steatohepatitis. ClinicalTrials.gov, Number NCT03938246.

First-in-human study of the safety, pharmacokinetics, and pharmacodynamics of first-in-class fatty acid synthase inhibitor TVB-2640 alone and with a taxane in advanced tumors

BACKGROUND

We conducted a first-in-human dose-escalation study with the oral FASN inhibitor TVB-2640 to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D), as monotherapy and with a taxane.

METHODS

This completed open-label outpatient study was conducted at 11 sites in the United States and United Kingdom. Patients with previously-treated advanced metastatic solid tumors and adequate performance status and organ function were eligible. TVB-2640 was administered orally daily until PD. Dose escalation initially followed an accelerated titration design that switched to a standard 3 + 3 design after Grade 2 toxicity occurred. Disease-specific cohorts were enrolled at the MTD. Statistical analyses were primarily descriptive. Safety analyses were performed on patients who received at least 1 dose of study drug. (Clinicaltrials.gov identifier NCT02223247).

FINDINGS

The study was conducted from 21 November 2013 to 07 February 2017. Overall, 136 patients received TVB-2640, 76 as monotherapy (weight-based doses of 60 mg/m² to 240 mg/m² and flat doses of 200 and 250 mg) and 60 in combination, (weight-based doses of 60 mg/m² to 100 mg/m² and flat dose of 200 mg) (55 paclitaxel, 5 docetaxel). DLTs with TVB-2640 were reversible skin and ocular effects. The MTD/RP2D was 100 mg/m². The most common TEAEs (n,%) with TVB-2640 monotherapy were alopecia (46; 61%), PPE syndrome (35; 46%), fatigue (28; 37%), decreased appetite (20; 26%), and dry skin (17; 22%), and with TVB-2640+paclitaxel were fatigue (29 ; 53%), alopecia (25; 46%), PPE syndrome (25; 46%), nausea (22; 40%), and peripheral neuropathy (20; 36%). One fatal case of drug-related pneumonitis occurred with TVB-2640+paclitaxel; no other treatment-related deaths occurred. Target engagement (FASN inhibition) and inhibition of lipogenesis were demonstrated with TVB-2640. The disease control rate (DCR) with TVB-2640 monotherapy was 42%; no patient treated with monotherapy had a complete or partial response (CR or PR). In combination with paclitaxel, the PR rate was 11% and the DCR was 70%. Responses were seen across multiple tumor types, including in patients with KRAS^MUT NSCLC, ovarian, and breast cancer.

INTERPRETATION

TVB-2640 demonstrated potent FASN inhibition and a predictable and manageable safety profile, primarily characterized by non-serious, reversible adverse events affecting skin and eyes. Further investigation of TVB-2640 in patients with solid tumors, particularly in KRAS^MUT lung, ovarian, and breast cancer, is warranted.

FUNDING

This trial was funded by 3-V Biosciences, Inc. (now known as Sagimet Biosciences Inc.).

Abstract CT095: A Phase Ib/IIa study of the BET bromodomain inhibitor ZEN-3694 in combination with enzalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC)

Background: Abiraterone (ABI) and enzalutamide (ENZ) have significant activity in mCRPC yet demonstrate frequent cross-resistance limiting efficacy of sequential androgen receptor (AR) targeting. Bromodomain extra terminal (BET) inhibitors (BETi) down-regulate the expression of putative drivers of ABI/ENZ resistance. ZEN-3694 is an orally bioavailable, potent, and selective BETi with significant anti-tumor activity in ENZ-resistant pre-clinical models. The safety and efficacy of ZEN-3694 in combination with ENZ was evaluated in a phase 1b/2a study in mCRPC (NCT02711956).

Methods: Patients (pts) were required to have progressive mCRPC, prior resistance to ABI and/or ENZ, and no prior chemotherapy for mCRPC. A 3 plus 3 dose escalation schema was utilized, with a starting daily oral dose of ZEN-3694 36 mg plus ENZ 160 mg. Dose expansion was conducted in parallel cohorts at low and high-dose ZEN-3694 (48 and 96 mg daily, respectively). The primary objective was determination of maximally tolerated dose (MTD); key secondary endpoints included time to radiographic progression (TTP) and pharmacokinetic (PK) parameters. Pharmacodynamic (PD) markers included whole blood RNA expression of BETi targets including MYC, IL-8, CCR1, and IL1RN.

Results: 64 pts were enrolled. The median age and PSA at study entry was 70 (range 47 - 89) and 25.9 (range 0.1 - 1701.8), respectively. At study entry, 24 (37.5%) of pts were resistant to ABI, 29 (45.3%) were resistant to ENZ, and 11 (17.2%) to both. ZEN-3694 dose levels ranged from 36 mg to 144 mg daily without reaching a MTD. The most common treatment-related adverse events (AEs) (any grade) included transient photophobia (66%), nausea (40%), fatigue (31%), decreased appetite (22%), and dysgeusia (16%). Grade ≥ 3 related AEs (N = 8) and dose-limiting toxicities (N = 1 at 96 mg dose level) were uncommon. No Grade ≥ 3 thrombocytopenia was observed. Exposure to ZEN-3694 increased with dose without significant drug-drug interaction with ENZ. PD analyses demonstrated exposure-dependent, up to 4-fold decrease in expression of BETi targets. RNA-Seq of paired tumor biopsies demonstrated suppression of BET-dependent genes. The overall median TTP was 44.4 weeks, and was similar in subgroups with prior ABI vs. ENZ resistance. Durable responses were observed, including 3 pts with disease primarily refractory to ABI on study treatment for 21.3 +, 20.8 +, and 17.3 months, respectively, with &gt; 90% decline in serum PSA. Early transitory serum PSA increases were associated with longer TTP.

Conclusions: ZEN-3694 demonstrates an acceptable safety and PK profile, robust target modulation, and encouraging disease stabilization in combination with ENZ in ABI/ENZ-refractory mCRPC. Analysis of paired metastatic tumor biopsies, circulating tumor cells and ctDNA is ongoing. Further investigation of the combination is warranted.

Citation Format: Rahul Aggarwal, Wassim Abida, Michael Schweizer, Allan Pantuck, David Nanus, Elisabeth Heath, Sanjay Lakhotia, Henrik Hansen, Michael Silverman, Lisa Bauman, Margo Snyder, Eric Campeau, Karen Norek, Sarah Attwell, Marie O'Farrell, Steve Smith, Philip Wegge, Ravi Jahagirdar, Joshi Alumkal. A Phase Ib/IIa study of the BET bromodomain inhibitor ZEN-3694 in combination with enzalutamide in patients with metastatic castration-resistant prostate cancer (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT095.

Abstract A75: Translational studies of a first-in-class FASN Inhibitor, TVB-2640, linking preclinical studies to clinical laboratory observations in solid tumor patients

Dysregulated expression of FASN is a central mediator of neoplastic lipogenesis. FASN catalyzes the production of palmitate, the building block of long chain fatty acids, providing a mechanism to convert glucose and other carbon sources into lipids needed for production of phospholipids, formation of lipid rafts and the subsequent assembly of receptor tyrosine kinases and other signaling molecules in microdomains juxtaposed to the membrane. Inhibition of FASN in tumor cells leads to disruption of PI3K/Akt/mTOR and other important pathways leading to apoptosis. Targeting this critical nexus between lipogenesis and cellular survival/proliferation signaling pathways makes inhibition of FASN a novel therapeutic approach with a strong biological rationale and 3-V Biosciences has initiated clinical studies with its first-in-class FASN inhibitor.

3-V Bio has developed a series of orally available, reversible, potent, and selective FASN inhibitors that remodel tumor cell membranes, disrupt pAkt and Wnt/beta-catenin pathways, and reprogram gene expression. These effects lead to apoptosis of tumor cells in culture, inhibition of anchorage-independent cell growth under lipid-rich conditions and inhibition of in vivo xenograft tumor growth in mice and rats. We are currently using transcriptomic and metabolomic analyses, including lipidmomic profiling, to explore the fundamental mechanisms resulting in sensitivity to the FASN inhibitor, TVB-3166. These same platforms are used to examine the changes in response to FASN inhibition in tumor and surrogate tissues of xenograft models as well as surrogate tissues of cancer patients.

A panel of tumor and normal cell lines was assembled and lipids were assessed prior to and 72 hours after treatment with TVB-3166. A reduction of saturated fatty acids was observed in all cell lines indicative of FASN inhibition. A similar extent of reduction was observed in media in the presence of 1% or 10% serum; these results demonstrated that the tumor cells did not compensate for FASN inhibition by increasing uptake of saturated fatty acids from the extracellular milieu. An inverse correlation was observed between the pretreatment quantities of saturated fatty acids and the induction of apoptosis resulting from FASN inhibition with TVB-3166; low levels of saturated fatty acids in cell lines such as COLO-205, correlated with a high level of cell killing. Normal, untransformed cells had significantly higher levels of pretreatment saturated fatty acids and a commensurate insensitivity to TVB-3166. These in vitro observations were extended to a COLO-205 rat xenograft model. Significant tumor growth inhibition was measured in these animals in response to FASN inhibition by TVB-3166. Tumor tissues were isolated and a reduction in pAkt and c-Myc expression were observed, the latter consistent with a reduction of Wnt/beta-catenin driven transcription. Further metabolomic analyses of surrogate and tumor tissues from this model continue.

The power of the metabolomic/lipidomic and transcriptomic analyses to evaluate drug responsiveness was applied to surrogate tissues of a small number of cancer patients treated with the FASN inhibitor, TVB-2640. Following 8 days of oral dosing, a preliminary evaluation of aqueous metabolites and lipids in patients' sera demonstrated changes consistent with the mechanism of FASN inhibition. Larger numbers of patients are being evaluated in order better characterize the extent of these changes. Preclinical evaluations of the molecular transformations caused by 3-V Bio's FASN inhibitors are being translated into clinical assessments that may ultimately lead to a more complete understanding of the impact of FASN inhibition in cancer patients and potentially the identification of tumor types that are likely to respond to treatment.

Citation Format: Doug Buckley, Tim Heuer, Marie O'Farrell, Bill McCulloch, George Kemble. Translational studies of a first-in-class FASN Inhibitor, TVB-2640, linking preclinical studies to clinical laboratory observations in solid tumor patients. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr A75.

Abstract A54: First-in-human study of the first-in-class fatty acid synthase (FASN) inhibitor, TVB-2640 as monotherapy or in combination - final results of dose escalation

Introduction

FASN inhibition is a novel approach to cancer treatment involving the selective disruption of palmitate biosynthesis that, in tumor cells, leads to apoptosis. TVB-2640 is an oral, first-in-class, small-molecule reversible inhibitor of FASN that demonstrates in vitro and in vivo anti-tumor effects. We previously reported (EORTC-NCI-AACR 2014: 3 LBA, AACR/ASCO 2015: CT203/ TPS2615) on the design of this trial (NCT02223247) and now report on the final results of the dose escalation phase.

Methods

Patients from 7 US and 4 UK sites with adequate bone marrow, hepatic and renal function were enrolled. Patients with significant cardiovascular or ophthalmological disease and any conditions that might interfere with oral absorption were excluded. In addition to standard safety assessments and pharmacokinetic (PK) sampling, ophthalmological examinations and 24-hour Holter monitoring for QTc assessments were performed. Blood and tumor tissue (archival and/or fresh) for various pharmacodynamic (PD) assessments were obtained.

Results

Thirty-one patients were enrolled in 6 monotherapy cohorts (60 mg/m2 to 250 mg flat dose) and 13 patients were enrolled in 2 combination cohorts (200 and 250 mg flat dose) in combination with weekly paclitaxel (80 mg/m2, days 1, 8 and 15 q 28 days). Plasma TVB-2640 drug levels increased with dose, with a half-life of approximately 15 hr. The MTD was declared at 100 mg/m2 for both schedules. DLTs observed in both mono- and combination patients were reversible and consisted of corneal edema (Grade 3, n = 2), keratitis and iritis (Grade 2 and 3, n = 1 each), probably a consequence of disrupted tear film lipid metabolism, and palmar-plantar erythrodysesthesia or skin peeling (Grade 3, n = 3 and Grade 1, n = 1). Other toxicities were mild (≤ Grade 2) and only minor GI symptoms were observed; alopecia was reported by 63% of patients overall. No enhancement of known paclitaxel toxicity was observed when given in combination with TVB-2640. Of the 7 NSCLC patients accrued so far, 1 achieved SD for 17 weeks with monotherapy and 2 patients treated in combination with paclitaxel had SD for 24 and 21 weeks respectively. One of three breast cancer patients (histology: triple negative) treated in combination had SD for 20 weeks. One confirmed PR was seen in a combination-treated patient who had peritoneal serous carcinoma with a 42% reduction in tumor load and 58% reduction in CA-125 levels. PD biomarkers have been identified in tumor and in serum. In all four patients with paired tumor biopsies, decreased pAKT S473 was observed after 1 cycle compared to pretreatment biopsies. Global metabolic profiling of serum showed increased levels of malonyl carnitine, a malonyl coA derivative, and decreased tripalmitin, a palmitate derivative, in 9 of 10 patients tested, after 8 days of TVB-2640 treatment. These changes are consistent with FASN inhibition.

Summary

Continuously administered, oral TVB-2640 demonstrated a tolerated dose and schedule with a manageable toxicity profile in association with encouraging signs of preliminary activity both as monotherapy and in combination with paclitaxel. PD analyses reveal engagement of the target in both tumor and surrogate tissue. Further exploration of biological activity in various specific tumor types is now underway in expansion cohorts at the MTD using both schedules.

Citation Format: Andrew Brenner, Jeffrey Infante, Manish Patel, Hendrik-Tobias Arkenau, Mark Voskoboynik, Erkut Borazanci, Gerald Falchook, L.R. Molife, Shubham Pant, Emma Dean, Lorraine Pelosof, Suzanne Jones, Chris Rubino, William McCulloch, Valentina Zhukova-Harrill, George Kemble, Marie O'Farrell, Howard A. Burris, III. First-in-human study of the first-in-class fatty acid synthase (FASN) inhibitor, TVB-2640 as monotherapy or in combination - final results of dose escalation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A54.

Abstract B13: Biomarker Analyses from Dose Escalation Phase of FASN Inhibitor TVB-2640 Phase 1 Study Shows Target Engagement in Solid Tumor Patients

TVB-2640 is a potent, reversible and selective fatty acid synthase (FASN) inhibitor currently in Phase 1 in solid tumor patients (study 3V2640-CLIN-002). This study includes biomarker assays to assess pharmacodynamic activity and refine strategies for patient selection. This report focuses on biomarker results from the dose escalation phase to assess pharmacodynamic activity for this first in class agent.

FASN is a central mediator of neoplastic lipogenesis, and uniquely catalyzes the production of palmitate, the building block of long chain fatty acids. Unlike most normal cells, tumor cells frequently have high FASN expression, which correlates with poor prognosis in several tumor types. Tumor cells rely on de novo lipogenesis to produce phospholipids, lipid second messengers, membranes and lipid rafts needed for oncogenic signaling, survival and proliferation, via many pathways including activated RTKs and hormone receptors.

In Phase 1 study 3V2640-CLIN-002 (NCT02223247), 31 patients were enrolled on TVB-2640 monotherapy (oral, once daily) and 13 patients were enrolled in combination with weekly paclitaxel. Plasma TVB-2640 drug levels increased with dose with a half-life of approximately 15 hr. Several complementary biomarker approaches were pursued to investigate FASN pathway inhibition in tumor and surrogate tissues.

(i) Serum was assessed by mass spectrometry-based global metabolomic profiling to screen for changes following TVB-2640 administration. Increased levels of malonyl carnitine were observed after 8 days of TVB-2640 treatment in 9/10 patients tested. The degree of change of malonyl carnitine increased with greater exposure to the drug. Decreased levels of tripalmitin were also observed in 9/10 patients. These changes are consistent with the expected consequences of FASN inhibition. Serum metabolite profiles from rats administered a FASN inhibitor for 5 to 7 days showed similar trends. These data provide evidence of FASN inhibition by TVB-2640, a first in class agent, in the clinic.

(ii) Fresh tumor biopsies were analyzed by immunohistochemistry (IHC) for markers relevant to FASN engagement. In all 4 patients to date with evaluable biopsies, pAKT S473 decreased by 30-50% after 1 cycle of TVB-2640 treatment relative to predose. Total AKT did not change in either of the 2 patients tested. pAKT inhibition has also been observed in preclinical rat xenografts treated with TVB-2640.

(iii) Gene expression analysis by RNA Seq has been initiated in pre and post dose macro-dissected tumor biopsies in a limited number of patients, and in whole blood for up to 13 patients. Preliminary bioinformatics analyses show modulation of several lipid metabolism pathways consistent with preclinical studies.

In conclusion, FASN pathway inhibition has been demonstrated at well tolerated dose levels of TVB-2640 in both tumor and serum from cancer patients. Increased serum malonyl carnitine and decreased levels of palmitate derivatives provide easily accessible biomarkers and show target inhibition. Early tumor biopsy analysis provides evidence of FASN inhibition in the target tissue by IHC and gene expression analysis. These and additional biomarker studies will be conducted in the expansion phase of this study and help guide clinical development of this first in class FASN inhibitor.

Citation Format: Marie O'Farrell, Richard Crowley, Timothy Heuer, Marina Fridlib, Doug Buckley, William McCulloch, George Kemble. Biomarker Analyses from Dose Escalation Phase of FASN Inhibitor TVB-2640 Phase 1 Study Shows Target Engagement in Solid Tumor Patients. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B13.

Abstract 4446: Discovery of tumor types highly susceptible to FASN inhibition and biomarker candidates for clinical analysis

Inhibition of de novo palmitate synthesis by fatty acid synthase (FASN) is a novel cancer therapeutic approach with strong biological rationale. Tumor cells have an increased dependence on FASN-synthesized palmitate compared to non-tumor cells, which obtain many of their required lipids from the extracellular milieu. FASN expression increases with tumor progression in human tumors and associates with chemoresistance, metastasis, and diminished patient survival in many tumor types. Palmitate and palmitate-derived lipids comprise diverse cellular components and function in processes required for tumor cell proliferation and survival.

TVB-2640 and TVB-3166 belong to a series of orally available, reversible, potent, and selective FASN inhibitors discovered and developed by 3-V Biosciences that exhibit anti-tumor activity in diverse preclinical tumor models. FASN inhibition induces tumor cell apoptosis by remodeling tumor cell membranes, blocking signal transduction, and reprogramming gene expression. These effects lead to inhibition of anchorage-independent tumor cell growth under lipid-rich conditions and inhibition of in vivo xenograft tumor growth in mice and rats.

Studies to understand the mechanisms of action and biological consequences of FASN inhibition are guiding the discovery of tumors highly dependent on FASN activity and biomarkers for assessment of pharmacodynamic activity and patient selection. Using quantitative genomics and a variety of directed analytical approaches, we identified lipid, mRNA, and protein profiles in tumor cells that change in response to FASN inhibition. Subsets of the changes show correlation with FASN inhibitor sensitivity. Marker candidates, such as gene expression signatures that classify in vitro sensitivity to FASN inhibition, are being investigated for detection in clinical human tumor data sets. Our studies also identified FASN inhibitor-mediated mechanisms of action that function in specific tumor types and biomarkers with potential utility for selecting responsive patients and measuring tumor response. Inhibition of the Wnt/b-catenin pathway and expression of TCF-promoter-regulated genes such as c-Myc are examples. Tumors dependent on Wnt/b-catenin activity or with lower intracellular palmitate stores prior to drug treatment may be susceptible to FASN inhibitor treatment. Pairing MYC expression with additional markers improves the performance of MYC as a marker to select tumor cell lines highly sensitive to FASN inhibition. Biomarker candidates from in vitro studies have been examined in vivo using xenograft tumor studies. These preclinical data support 3-V Biosciences’ ongoing Phase I clinical study of a first-in-class FASN inhibitor TVB-2640, and help guide the next steps in its development.

Citation Format: Timothy S. Heuer, Richard Ventura, Kasia Mordec, Julie Lai, Joanna Waszczuk, Glenn Hammonds, Marina Fridlib, Russell Johnson, Lily Hu, Allan Wagman, Marie O' Farrell, Douglas Buckley, George Kemble. Discovery of tumor types highly susceptible to FASN inhibition and biomarker candidates for clinical analysis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4446. doi:10.1158/1538-7445.AM2015-4446

Abstract 2675: Biomarker and PK/PD analyses of first in class FASN inhibitor TVB-2640 in a first-in-human phase 1 study in solid tumor patients

TVB-2640 is a potent, reversible and selective fatty acid synthase (FASN) inhibitor currently in its first Phase 1 study (3V2640-CLIN-002) in solid tumor patients. This study includes biomarker assays for this first in class agent to assess pharmacodynamic activity and refine strategies for patient selection. We describe translational approaches and report early Phase 1 data on FASN biomarkers, in tumor, serum and surrogate tissues such as PBMC and whole blood.

FASN is a central mediator of neoplastic lipogenesis. FASN uniquely catalyzes the production of palmitate, the building block of long chain fatty acids, providing a mechanism to convert glucose into lipids needed to support cancer cell signaling and proliferation. Tumor cells have increased dependence on de novo lipogenesis than normal cells, and express higher levels of FASN. Several studies have shown a correlation between high levels of FASN expression and both advanced disease stage and poorer prognosis in patients. FASN plays several roles in cancer cell signaling, including production of phospholipids, alteration of membrane architecture, formation of lipid rafts and the subsequent assembly of signaling molecules in microdomains juxtaposed to the membrane. FASN is upregulated by RTK signaling and also by androgen and estrogen signaling.

The profile of FASN expression was characterized by IHC across several hundred archival human tumors and sera (unmatched) across 8 different tumor types. Highest FASN expression by IHC was observed in colorectal, prostate and bladder tumors, with a similar rank ordering for serum with NSCLC and endometrial also among the highest. Normal donors had significantly lower serum levels. Follow up studies are being conducted to investigate the effect of FASN inhibitors on secreted FASN, and its use as a biomarker.

Seventeen patients have been enrolled in 3V2640-CLIN-002, and four dose levels of TVB-2640 have been tested to date as monotherapy. PK data show a mean half-life of approximately 16.5 hours following oral administration. Plasma Cmax and AUC increase with dose on day 1, with some overlap between the two highest dose levels at steady state. Several exploratory biomarker analyses have been initiated. Tumor IHC data are available for one patient, and decreased pS6 S240/244 and pAKTS473 were observed after TVB-2640 administration. Secreted proteins such as FASN, VEGF and related proteins in serum are being assessed by ELISA and PK/PD analysis will be shown. A serum metabolomics screen has been initiated to assess changes in lipids and related metabolites.

These translational and clinical biomarker assessments inform on FASN biology and clinical development of the first in class FASN inhibitor TVB-2640.

Citation Format: Marie O'Farrell, Richard Crowley, Timothy S. Heuer, Doug Buckley, Chris M. Rubino, William McCulloch, George Kemble. Biomarker and PK/PD analyses of first in class FASN inhibitor TVB-2640 in a first-in-human phase 1 study in solid tumor patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2675. doi:10.1158/1538-7445.AM2015-2675

Abstract 1644: Design and discovery of PWT33597 (VDC-597), a dual inhibitor of PI3-kinase alpha and mTOR

Phosphoinositide-3-kinase (PI3K) is an important mediator of tumor cell growth, survival and proliferation. In particular, PI3K alpha is important for signaling downstream of receptor tyrosine kinases and is also frequently amplified or mutationally

activated in tumors, suggesting that selective inhibitors of this isoform may have therapeutic utility in the treatment of cancer. Downstream of PI3K, the mTOR kinase also plays a critical role in cellular growth and metabolism, and inhibitors of mTOR have demonstrated clinical benefit in several tumor types. We report here the design, discovery and characterization of PWT33597 (VDC-597), a dual inhibitor of PI3K alpha and mTOR, which entered human clinical trials in 2011. Starting with the known pan-Class I PI3-kinase inhibitor ZSTK474, we identified the methanesulfonylpiperazine analogue, 2-(difluoromethyl)-1-[4-[4-(methylsulfonyl)-1-piperazinyl]-6-(4-morpholinyl)-1,3,5-triazin-2-yl]-1H-benzimidazole as a promising lead compound with activity against both PI3K alpha (IC50 = 21 nM) and PI3K delta (IC50 = 18 nM). The addition of a methoxy group at the 4-position of the benzimidazole group led to a more selective inhibitor of PI3K alpha (IC50 = 6 nM versus 41 nM for PI3K delta), although with reduced solubility. A search for more soluble analogues identified SN 32976 as a selective inhibitor of PI3K alpha (IC50 = 28 nM) over both PI3K delta (IC50 = 287 nM) and mTOR (IC50 = 227 nM), with good aqueous solubility. SN 32976 displayed good oral bioavailability and was significantly more active than ZSTK474 against a U87 MG human tumor xenograft model in mice. A search for more metabolically stable analogues subsequently identified PWT33597, which maintained the selectivity for PI3K alpha (IC50 = 26 nM) over PI3K delta (IC50 = 291 nM) but now also displayed activity against mTOR in biochemical assays (IC50 = 21 nM). PWT33597 had good pharmacokinetic properties in multiple preclinical species, was not extensively metabolized in vivo and showed little potential for interaction with cytochrome P450 enzymes. Human clinical trials of PWT33597 were completed in 2012, and it is now undergoing further studies in veterinary cancers (as VDC-597).

Citation Format: Gordon W. Rewcastle, Jack U. Flanagan, Anna C. Giddens, Swarna A. Gamage, Sophia KY Tsang, Jackie D. Kendall, Bruce C. Baguley, Christina M. Buchanan, David J. Matthews, Marie O'Farrell, Stephen MF Jamieson, William A. Denny, Peter R. Shepherd. Design and discovery of PWT33597 (VDC-597), a dual inhibitor of PI3-kinase alpha and mTOR. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1644. doi:10.1158/1538-7445.AM2014-1644

p21-Activated kinase 1 is required for efficient tumor formation and progression in a Ras-mediated skin cancer model

The RAS genes are the most commonly mutated oncogenes in human cancer and present a particular therapeutic dilemma, as direct targeting of Ras proteins by small molecules has proved difficult. Signaling pathways downstream of Ras, in particular Raf/Mek/Erk and PI3K/Akt/mTOR, are dominated by lipid and protein kinases that provide attractive alternate targets in Ras-driven tumors. As p21-activated kinase 1 (Pak1) has been shown to regulate both these signaling pathways and is itself upregulated in many human cancers, we assessed the role of Pak1 in Ras-driven skin cancer. In human squamous cell carcinoma (SCC), we found a strong positive correlation between advanced stage and grade and PAK1 expression. Using a mouse model of Kras-driven SCC, we showed that deletion of the mouse Pak1 gene led to markedly decreased tumorigenesis and progression, accompanied by near total loss of Erk and Akt activity. Treatment of Kras(G12D) mice with either of two distinct small molecule Pak inhibitors (PF3758309 and FRAX597) caused tumor regression and loss of Erk and Akt activity. Tumor regression was also seen in mice treated with a specific Mek inhibitor, but not with an Akt inhibitor. These findings establish Pak1 as a new target in KRAS-driven tumors and suggest a mechanism of action through the Erk, but not the Akt, signaling pathway.

Abstract 3737: The PI3K/mTOR inhibitor PWT33597 regresses 786-0 renal xenografts

PWT33597 is a balanced dual inhibitor of phosphatidylinositol 3-kinase alpha (PI3K alpha) and mTOR, currently in clinical development. Inhibition of signaling downstream of PI3K and mTOR by PWT33597 has been demonstrated, and PWT33597 is strongly efficacious in multiple xenograft models tested to date with different PIK3CA and PTEN genotypes. Inhibitors of mTORC1 (rapalogs) are approved for treatment of advanced renal cell carcinoma (RCC), but their effect is restricted to a subset of patients, and is not sustained. Inhibitors of VEGFR signaling such as sorafenib and sunitinib have also demonstrated clinical activity in RCC and are approved in this indication. Based on the proven role of rapalogs in RCC, we tested PWT33597 in a renal xenograft model with the hypothesis that inhibition of both mTORC1 and mTORC2, as well as PI3K, may offer increased efficacy by direct targeting of multiple signaling nodes including VEGFR signaling. Dual inhibition would also be expected to decrease release of negative feedback loops triggered by either mTOR or PI3K inhibition alone. PWT33597 was tested in 786-0 (VHL -/-, PTEN -/-) xenografts in comparison to rapamycin (mTORC1 inhibitor), and sorafenib (VEGFR/RAF inhibitor). While sorafenib and rapamycin showed tumor growth inhibition (TGI), the maximal effect with sorafenib was 64% TGI, and rapamycin had a largely cytostatic effect. The overall efficacy observed with PWT33597 was superior, with 93% TGI observed. PWT33597 was also tested in comparison to a pan-PI3K inhibitor (GDC-0941, 49% TGI) and demonstrated superior efficacy. Immunohistochemical analysis of tumors for cleaved caspase 3 (CC3) as an indicator of apoptosis showed that a single dose of PWT33597 induced a several fold increase in CC3 staining, and this effect was also apparent after 18 days of dosing. Based on these results we tested the ability of PWT33597 to regress large 786-0 tumors (approx. 500 mm3), and a rapid decrease in tumor size was observed in 100% of animals. Additional cellular and xenograft studies in RCC models are ongoing to further define the mechanism of action of PWT33597, and will be presented. Taken together, these data provide rationale for testing PWT33597 in patients with RCC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3737. doi:1538-7445.AM2012-3737

Abstract B160: PWT33597 promotes apoptosis in tumor cells through balanced dual inhibition of PI3K alpha and mTOR

Phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) serve as critical nodes in an intracellular signaling network that regulates cell growth, proliferation and survival, and dysregulation of this signaling network is frequently found in tumor cells. PWT33597 is a novel, balanced, dual inhibitor of PI3K alpha and mTOR currently in clinical development. To dissect the relative contribution of PI3K and mTOR pathways to activity, we explored the effects of various mono versus dual PI3K and mTOR inhibitors on intracellular signaling pathways, proliferation and apoptosis in cancer cell lines harboring PI3K alpha mutations. The panel of inhibitors used includes compounds that are highly selective for PI3K (GDC-0941), molecules that are highly selective for mTORC1/2 (AZD8055), as well as dual inhibitors such as PWT33597, BEZ235, PF-04691502 and GSK2126453.

Our results indicate that compounds predominantly inhibiting PI3K have modest effects on phosphorylation of pathway proteins downstream of mTOR (in particular 4EBP), and do not lead to sustained induction of apoptosis markers such as PARP. Conversely, compounds that predominantly target mTORC1/2 produce feedback activation of PI3K signaling, resulting in increased phosphorylation of AKT (T308) and very limited effects on cell death. Dual PI3K/mTOR inhibitors produce more significant inhibition across the pathway, in particular leading to sustained inhibition of pAKT (S473 and T308) and p4EBP (T37/46), decreased release of normal feedback loops within the pathway, and an increased percentage of apoptotic cells as measured by percent population in sub-G1 phase of the cell cycle. In particular, PWT33597 produces potent and sustained pathway inhibition both for PI3K and mTOR-dependent readouts (pAKT S473, pAKT T308 and p4EBP T37/46), and maintains induction of apoptotic markers, resulting in cell death.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B160.

Evaluation of a community fissure sealant programme in County Meath, Ireland

OBJECTIVE

To evaluate the fissure sealant programme operated by the North Eastern Health Board Dental Service in County Meath, Republic of Ireland. The fissure sealant programme forms part of the school dental service aimed at children in first class (age group 6-7 years).

DESIGN

Cross sectional study with retrospective analysis of dental records.

CLINICAL SETTING

Schools in County Meath in 1999.

PARTICIPANTS

Children in fourth class (mean age 9.6 years) in the school year 1999/2000 who had participated in the fissure sealant programme in the school year 1996/97.

MAIN OUTCOME MEASURES

Sealant retention using the criteria of Simonsen.

RESULTS

The mean age of sealant was 2.3 years. Fifty six percent of sealants were completely retained, 27% were partially retained and 12.8% were missing. The majority (73%) of children had some sealant on at least one tooth. Caries experience in previously sealed teeth was low (2.9%). Children who had all four first permanent molars sealed had a significantly lower DMFT (visual) than those who had no sealants (Wilcoxan p < 0.0001).

CONCLUSION

Despite lack of maintenance of sealants in this study, retention rates compared favourably with similar international studies and caries experience in previously sealed teeth was low. The use of a written sealant policy and protocol for sealant application and equipment maintenance could further improve retention rates. Children who had no sealants had significantly poorer dental health than children who had all four first permanent molars sealed.

Studies on the mechanism of enhancement of purinergic transmission by caffeine in the guinea-pig isolated vas deferens

1. Purinergic transmission from sympathetic nerves in the guinea-pig vas deferens was monitored using intracellular recording techniques. Stimulation of the hypogastric nerve with trains of 15 pulses at 1 Hz evoked excitatory junction potentials (EJPs) which increased in amplitude from the first pulse and reached a maximum after 6-8 pulses. 2. Caffeine (3 and 10 mm), depolarized cells by 5-10 mV and increased the amplitude of the first few EJPs in each train but reduced the maximum amplitude of EJPs late in the train. 3. The adenosine receptor antagonist 8-p-sulphophenyl-theophylline (8-SPT; 30 microm) had no effect on either the resting membrane potential or the EJP amplitude; however, at 100 microm it reduced the amplitude of all EJPs by 5-10%. 4. Adenosine (10 and 30 microm) reduced the amplitude of EJPs in a concentration-dependent manner. The inhibitory effect of adenosine on EJP amplitude was prevented by pretreatment with either caffeine (3 mm) or 8-SPT (30 microm). 5. Ryanodine (30 microm) did not alter EJP amplitude and did not inhibit the enhancement of the first EJP by caffeine (3 mm). Incubation of the tissue with the cell permeable calcium chelator 1-2-bis(o-aminophenoxy)ethane-N,N-N',N'-tetraacetic acid (BAPT-AM) resulted in a depression of EJP amplitude and a longer time to reach maximum amplitude. In cells that had been exposed to BAPT-AM, caffeine 3 mm still increased amplitude of EJP early in the train. 6. The phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX; 500 microm), hyperpolarized cells and increased the amplitude of EJP throughout the train of stimulation. In the presence of IBMX, caffeine 3 mm still depolarized the cells and enhanced the EJP early in the train of stimulation. 7. The findings in this study confirm that caffeine and 8-SPT are effective inhibitors of the actions of adenosine. However, caffeine has an additional action to enhance EJP early during a train of stimulation, which cannot be attributed to blockade of adenosine receptors, but which may be related to inhibition of phosphodiesterase.

Prevalence of oral lesions among a sample of Bangladeshi medical users aged 40 years and over living in Tower Hamlets, UK

AIM

To collect data on the prevalence of oral mucosal lesions among Bangladeshi medical care users aged 40 years and over and to explore the relationship of oral disease status and tobacco smoking and paan (betel quid) chewing.

DESIGN

Multi-centre cross-sectional study.

SETTING

General medical practitioners' waiting areas in Tower Hamlets, UK.

SUBJECTS

185 Bangladeshi adults aged 40 years old and over.

METHOD

An oral mucosal examination, based on WHO criteria and an interview. Information on tobacco smoking and paan chewing behaviour was collected during the interview.

RESULTS

Out of 185 adults there was a response rate of 74%. Oral mucosal lesions were observed in 40% of participants. The most common lesion was found to be leukoplakia with a prevalence of 25%. Significant relationships were found between smoking and the presence of oral pathology and between paan chewing with tobacco and the presence of leukoplakia.

CONCLUSION

In this study of older Bangladeshi medical care users there was a high prevalence of oral mucosal lesions. Sensitively tailored health promotion interventions, which aim to reduce tobacco use, should be developed for this population.

Dental health and treatment needs among a sample of Bangladeshi medical users aged 40 years and over living in Tower Hamlets, UK

AIM

To assess the dental health status and treatment needs of Bangladeshi medical care users aged 40 years and over and to explore the relationship of oral disease status, tobacco usage and paan (betel quid) chewing.

DESIGN

Multi-centre cross-sectional study.

SETTING

General medical practitioners' waiting areas in Tower Hamlets, UK.

SUBJECTS

185 Bangladeshi adults aged 40 years and over.

INTERVENTION

A clinical examination and an interview schedule.

MEASURES

Dental status, periodontal status, dental plaque, calculus and denture status. Tobacco smoking and paan chewing behaviour.

RESULTS

The response rate was 74%. 85% of participants were dentate with an average number of 24 (SD +/- 5.4) standing teeth. The mean DMFT score was 5.38, with missing teeth (3.81) being the major component. The decayed component was 0.43 and the filled was 1.14. 46% of participants were assessed as being free from gingivitis. Significant relationships between chewing paan and aspects of dental and periodontal status were found. Impacts of oral health were reported by 45% of the respondents. The normative need for dental treatment was 96% with a perceived need of 48%.

CONCLUSION

There was considerable normative dental need. Whilst caries experience was low, there were high levels of periodontal treatment needs. Paan chewing was related to aspects of dental and periodontal status.

Mobilizing store Ca(2+) in the presence of La(3+) evokes exocytosis in bovine chromaffin cells

The effect on exocytosis of La(3+), a known inhibitor of plasma membrane Ca(2+)-ATPases and Na(+)/Ca(2+) exchangers, was studied using cultured bovine adrenal chromaffin cells. At high concentrations (0.3-3 mM), La(3+) substantially increased histamine-induced catecholamine secretion. This action was mimicked by other lanthanide ions (Nd(3+), Eu(3+), Gd(3+), and Tb(3+)), but not several divalent cations. In the presence of La(3+), the secretory response to histamine became independent of extracellular Ca(2+). La(3+) enhanced secretion evoked by other agents that mobilize intracellular Ca(2+) stores (angiotensin II, bradykinin, caffeine, and thapsigargin), but not that due to passive depolarization with 20 mM K(+). La(3+) still enhanced histamine-induced secretion in the presence of the nonselective inhibitors of Ca(2+)-permeant channels SKF96365 and Cd(2+), but the enhancement was abolished by prior depletion of intracellular Ca(2+) stores with thapsigargin. La(3+) inhibited (45)Ca(2+) efflux from preloaded chromaffin cells in the presence or absence of Na(+). It also enhanced and prolonged the rise in cytosolic [Ca(2+)] measured with fura-2 during mobilization of intracellular Ca(2+) stores with histamine in Ca(2+)-free buffer. The results suggest that the efficacy of intracellular Ca(2+) stores in evoking exocytosis is enhanced dramatically by inhibiting Ca(2+) efflux from the cell.

Differential control of tyrosine hydroxylase activation and catecholamine secretion by voltage-operated Ca2+ channels in bovine chromaffin cells

Contributions of L-, N-, and P/Q-type voltage-operated Ca2+ channels to two responses of bovine adrenal chromaffin cells have been studied using the nonreceptor stimulus K+ depolarization. Tyrosine hydroxylase activity and catecholamine secretion were both increased by K+ over a similar concentration range and in a Ca(2+)-dependent manner. At a submaximal concentration of 20 mM K+, tyrosine hydroxylase activation was reduced by nitrendipine but unaffected individually by (+/-)-Bay K 8644, omega-conotoxin GVIA, omega-agatoxin IVA, and omega-conotoxin MVIIC. It was fully blocked by combined inhibition of L-, N-, and P/Q-type channels. With a maximal concentration of 50 mM K+, tyrosine hydroxylase activation was unaffected by nitrendipine as well as by each of the other drugs on its own; however, it was reduced by 71 % by combined inhibition of L-, N-, and P/Q-type channels. In contrast, catecholamine secretion with both 20 and 50 mM K+ was enhanced by (+/-)-Bay K 8644, partially inhibited by nitrendipine and omega-conotoxin MVIIC, and completely blocked by a combination of antagonists for L-, N-, and P/Q-type channels. The results show that Ca2+ entry through voltage-operated Ca2+ channels can differentially regulate distinct chromaffin cell responses and that this is an intrinsic property of the mechanisms by which Ca2+ entry activates these responses. It is not dependent on the parallel activation of other signaling events by receptors.

The prevalence of dental erosion in the maxillary incisors of 14-year-old schoolchildren living in Tower Hamlets and Hackney, London, UK

The purpose of this study was to assess the prevalence of dental erosion in the maxillary incisors of a sample of 14-year-old schoolchildren and to explore the aetiological factors responsible for that erosion. The cross-sectionally design study took place in secondary schools in inner-city London, UK and involved 525, 14-year-old schoolchildren selected at random in a clinical examination and a self-completed questionnaire. The outcomes measures for dental erosion were; the prevalence, the area and depth of lesions and the risk factors. The prevalence of labial and palatal erosion was 16.9 per cent and 12 per cent respectively. Risk factors and behaviours including daily frequency of ingestion of acidic fruits and drinks, food vomiting, toothbrushing frequency, and swimming habits were not shown to have any relationship with the presence of erosion. It was concluded that the prevalence of erosion in the maxillary incisors of this sample was higher labially and lower palatally than in previously reported national figures. The risk factors which were investigated were not shown to have any relationship with the presence of erosion. Further investigations of these issues are necessary to establish whether or not dental erosion is a public health problem in the UK.

Dental service use and the implications for oral cancer screening in a sample of Bangladeshi adult medical care users living in Tower Hamlets, UK

AIM

To assess the use of dental services, barriers to uptake of dental care and attitudes to regular dental examinations and the prevalence of tobacco and paan chewing habits in a group of Bangladeshi medical care users.

DESIGN

Multi-centre cross-sectional study.

SETTING

Four general medical practices' waiting areas in Tower Hamlets.

SUBJECTS

Bangladeshi adults aged 40 years and over.

INTERVENTION

An interview schedule.

MAIN OUTCOME MEASURES

The prevalence of tobacco smoking and paan chewing with or without the addition of tobacco. The use of dental services, barriers to the use of dental services and attitudes to regular dental examinations.

RESULTS

Results were obtained from 158 subjects (response rate 85%). 25% of the whole sample had never visited a dentist. These were significantly (P < 0.05) more likely to be women, who also thought regular check-ups were of little value. In their use of health services 73% experienced language difficulties. 33% of the sample were tobacco smokers. Paan was chewed by 78% of the sample with significantly (P < 0.05) more females than males adding tobacco to their quid and chewing more frequently than males.

CONCLUSION

There are considerable barriers to be overcome if dental practices are to be the site for oral cancer screening and oral health promotion in this population. There are sex differences in reported behaviour and attitudes about use of dental services and in tobacco and paan use in this Bangladeshi sample. Further research is needed to establish why this ethnic minority attend general medical practices but not general dental practices.

Different contributions of voltage-sensitive Ca2+ channels to histamine-induced catecholamine release and tyrosine hydroxylase activation in bovine adrenal chromaffin cells

Histamine stimulates catecholamine release and tyrosine hydroxylase activity in a Ca(2+)-dependent manner in bovine adrenal chromaffin cells. The role of voltage-sensitive Ca2+ channels in these two responses has been investigated. Using an EC50 concentration of histamine, 1 microM, catecholamine release was enhanced by (+/-)BayK8644, and partially inhibited by nitrendipine and omega-agatoxin IVA, blockers of L- and P/Q-type Ca2+ channels. omega-Conotoxin GVIA gave small and variable inhibitory effects. With a maximal histamine concentration, 10 microM, similar results were obtained except that now omega-conotoxin GVIA reliably reduced release. In contrast, neither (+/-)BayK8644 nor any of the individual Ca2+ channel antagonists had any significant effect on tyrosine hydroxylase (TOH) activation induced by either an EC50 or a maximal concentration of histamine. When high concentrations of nitrendipine, omega-conotoxin GVIA and omega-agatoxin IVA were combined with omega-conotoxin MVIIC (a non-selective blocker of N, P and Q channels) to block voltage-sensitive Ca2+ channels in these cells, release induced by K+ depolarization was completely blocked. Release caused by histamine, however, was substantially reduced but not abolished. The combination of antagonists also only partially inhibited TOH activation by histamine. The results show that the G protein-coupled receptor agonist histamine activates several different types of voltage-sensitive Ca2+ channels in chromaffin cells to mediate its cellular effects. Histamine may also activate additional pathways for Ca2+ entry. The results also suggest that the manner by which Ca2+ controls release and TOH activation once it has entered chromaffin cells through these channels are different.

Multiple calcium channels are required for pituitary adenylate cyclase-activating polypeptide-induced catecholamine secretion from bovine cultured adrenal chromaffin cells

The effects of L-, N-, P- and Q-type calcium channel antagonists and (+/-)-BayK-8644 on catecholamine release induced by pituitary adenylate cyclase-activating polypeptide (PACAP-27) were investigated in bovine cultured adrenal chromaffin cells. PACAP-27 induced the release of 4-15% of the total cellular catecholamines over 7 min, with an EC50 of 20 nM and the effect approaching maximum at 100 nM. Catecholamine release was fully dependent on the presence of extracellular calcium. The dihydropyridine nitrendipine which inhibits L-type calcium channels inhibited PACAP-27-induced secretion in a concentration dependent manner with an inhibition of 20-30% at 1 microM. In contrast, (+/-)-BayK-8644, which prolongs the opening of L-type calcium channels produced a concentration-dependent increase in PACAP-27-induced catecholamine release with 1 microM increasing release by 40-60%. Blockade of N-type calcium channels with omega-conotoxin GVIA reduced release by 5-15%. Block of P-type channels with low concentrations of omega-agatoxin IVA (< or = 30 nM) had no significant effect on release, while higher concentrations (100-300 nM) which block Q-type channels reduced release by up to 15%. omega-Conotoxin MVIIC, an antagonist of Q-type calcium channels and also of N- and P-type channels, inhibited release in a concentration-dependent manner with a near maximum effect of 30-50% produced by 300 nM. The combination of omega-conotoxin GVIA and omega-agatoxin IVA reduced release by 40-50%. Addition of omega-conotoxin MVIIC (300 nM) to the combination of omega-conotoxin GVIA (10 nM) and omega-agatoxin IVA (100 nM) did not inhibit catecholamine release more than with omega-conotoxin GVIA and omega-agatoxin IVA alone, indicating that 100 nM omega-agatoxin IVA was sufficient to block the Q-type calcium channels. When nitrendipine was used together with omega-conotoxin GVIA, omega-agatoxin IVA and omega-conotoxin MVIIC, catecholamine release induced by 20 nM or 100 nM PACAP-27 was reduced by 70-85%. Taken together these results suggest that influx of calcium through multiple different voltage-sensitive calcium channels mediate PACAP-27-induced catecholamine release from bovine chromaffin cells, and that L-, N- and Q-channels contribute to this response.

Random mutagenesis of the poly(ADP-ribose) polymerase catalytic domain reveals amino acids involved in polymer branching

Poly(ADP-ribose) polymerase (PARP) is a multifunctional nuclear zinc finger protein which participates in the immediate response of mammalian cells exposed to DNA damaging agents. Given the complexity of the poly(ADP-ribosylation) reaction, we developed a large-scale screening procedure in Escherichia coli to identify randomly amino acids involved in the various aspects of this mechanism. Random mutations were generated by the polymerase chain reaction in a cDNA sequence covering most of the catalytic domain. Out of 26 individual mutations that diversely inactivated the full-length PARP, 22 were found at conserved positions in the primary structure, and 24 were located in the core domain formed by two beta-sheets containing the active site. Most of the PARP mutants were altered in poly(ADP-ribose) elongation and/or branching. The spatial proximity of some residues involved in chain elongation (E988) and branching (Y986) suggests a proximity or a superposition of these two catalytic sites. Other residues affected in branching were located at the surface of the molecule (R847, E923, G972), indicating that protein-protein contacts are necessary for optimal polymer branching. This screening procedure provides a simple and efficient method to explore further the structure-function relationship of the enzyme.

Effects of N- and L-type calcium channel antagonists and (+/-)-Bay K8644 on nerve-induced catecholamine secretion from bovine perfused adrenal glands

1. The effects of N- and L-type calcium channel antagonists and (+/-)-Bay K8644 on catecholamine release from chromaffin cells and acetylcholine release from splanchnic nerve terminals was investigated in bovine perfused adrenal glands. 2. Adrenal glands were perfused retrogradely and preloaded with [3H]-choline. Subsequent efflux of 3H-labelled compounds was taken as an index of acetylcholine release from the splanchnic nerve terminals. Noradrenaline and adrenaline release from the glands was measured by h.p.l.c. with electrochemical detection. 3. A maximally effective frequency of field stimulation of the adrenal nerves, 10 Hz, induced release of catecholamines and 3H-labelled compounds. Tetrodotoxin (1 microM) abolished release of both catecholamines and 3H-labelled compounds. A combination of mecamylamine (5 microM) and atropine (1 microM) inhibited nerve-induced catecholamine release by about 75% but did not inhibit release of 3H-labelled compounds. Reducing the concentration of extracellular calcium 5 fold to 0.5 mM inhibited nerve-induced catecholamine release by 80% and release of 3H-labelled compounds by 50%. 4. (+/-)-Bay K8644 (1 microM), nitrendipine (1 microM), omega-conotoxin-GVIA (10 nM) and the combination of nitrendipine and omega-conotoxin-GVIA each had no effect on nerve-induced release of 3H-labelled compounds. 5. (+/-)-Bay K8644 (1 microM) potentiated nerve-induced catecholamine release by 75%. Nitrendipine (1 microM) reduced release by 20% but this did not reach statistical significance, omega-Conotoxin-GVIA (10 nM) reduced nerve-induced catecholamine release by 75%, while the combination of omega-conotoxin-GVIA and nitrendipine reduced release to the same extent as omega-conotoxin-GVIA alone. 6. Exogenous acetylcholine perfusion through the glands produced a concentration-dependent increase in catecholamine release. The maximally effective concentration of acetylcholine for catecholamine release was > or = 300 microM, while 30 microM acetylcholine gave comparable catecholamine release to that obtained with 10 Hz field stimulation. 7. (+/-)-Bay K8644 (1 microM), nitrendipine (1 microM) and omega-conotoxin-GVIA (10 nM) each had no significant effect on catecholamine release evoked by perfusion of the gland with either a near maximally effective concentration of acetylcholine, 100 microM, or with the lower concentration of 30 microM. 8. The results show that the omega-conotoxin-GVIA-sensitive N-type voltage-sensitive calcium channels located on the chromaffin cells are largely responsible for catecholamine release induced by nerve stimulation in bovine adrenal glands. In contrast, N-type calcium channels are not involved in catecholamine release induced by exogenous acetylcholine. L-type voltage sensitive calcium channels do not play a major role in nerve-induced or exogenously applied acetylcholine-induced catecholamine release. However, the L-type calcium channels do have the potential to augment powerfully nerve-induced catecholamine release. N- and L-type calcium channels do not play a major role in the presynaptic release of acetylcholine.

Caffeine enhances sympathetic purinergic and noradrenergic transmission in the guinea-pig isolated vas deferens

Intracellular recording techniques were used to monitor the resting membrane potential of smooth muscle cells and the excitatory junction potentials (EJPs) evoked by stimulation of the hypogastric nerve. Stimulation with trains of 15 pulses at 1 Hz or 0.33 Hz evoked individual EJPs which increased in amplitude from the first pulse and reached a plateau after 6-8 pulses. Stimulation at 1 Hz resulted in EJPs facilitating to a plateau level of approximately 25 mV, whereas with stimulation at 0.33 Hz the EJPs only facilitated to a plateau level of about 12 mV. With stimulation at 1 Hz, caffeine (3 mM and 10 mM), increased the amplitude of the first few EJPs in each train and decreased the extent of facilitation and reduced the amplitude of fully facilitated EJPs. In comparison, the amplitude of all EJPs evoked by stimulation at 0.33 Hz was increased by caffeine (3 mM and 10 mM). With 0.33 Hz stimulation, facilitation of the first few EJPs was observed in the presence of 3 mM caffeine but not in the presence of 10 mM caffeine. In the presence of the alpha 2-adrenoceptor antagonist idazoxan, caffeine (3 mM and 10 mM) still enhanced the amplitude of EJPs early in trains of stimulation but there was no depression of EJPs later in the trains. Similarly, in reserpine-treated vasa deferentia, caffeine (3 mM) enhanced EJPs early in the train of stimulation at 1 Hz and there was no depression of EJPs at the end of the train. In addition to electrophysiological experiments, the effect of caffeine (0.1-30 mM) on the resting and stimulation-induced (S-I) efflux of radioactivity was investigated in guinea-pig isolated vasa deferentia previously incubated with [3H]-noradrenaline. Caffeine (10 mM) did not affect the resting efflux of [3H]-noradrenaline but significantly enhanced the S-I efflux by 150-160%. The present findings suggest that caffeine enhances sympathetic purinergic and noradrenergic transmission at the sympathetic neuroeffector junction in the guinea-pig vas deferens. Moreover, the increased release of transmitter noradrenaline can modulate purinergic transmission by activation of alpha 2-adrenoceptors located at sympathetic neuroeffector sites.

Characterisation of a gain-of-function mutant of poly(ADP-ribose) polymerase

In order to examine the structure-function relationship of the poly (ADP-ribose) polymerase (PARP) catalytic domain, potential active-site residues in the catalytic domain have previously been described. Here, we have used mutagenesis with hydroxylamine to generate a random library of PARP mutants. The identification, overproduction in insect cells, purification and characterization of a gain-of-function mutant (L713F) is described. We show that the kcat of this mutant is increased over nine times compared to the wild-type enzyme; the Km for NAD+ is unchanged. The size and the branching structure of the ADP-ribose polymers are similar in both the wild-type and the mutant enzyme. This mutation may have an allosteric effect on the catalytic site and could be useful in analyzing the consequences of poly ADP-ribose overproduction in vivo on cell survival following DNA damage.

ADP-ribosylation reactions in plants

Poly ADP-ribosylation is a post-translational modification of protein structure and function that occurs in the nucleus of most eukaryotic cells. Although its function has not been fully elucidated it is thought to have a role in the processing DNA strand breaks. Poly(ADP-ribose) polymerase, a highly conserved enzyme, is well studied in animal cell systems but is less well characterised in plants. Our present understanding of mono and poly ADP-ribosylation reactions in plants is reviewed in this article.

Poly(ADP-ribose) polymerase in plant nuclei

We show that poly(ADP-ribose) polymerase is present in maize, pea and wheat nuclei. We have identified the enzyme product as poly(ADP-ribose) by purification and electrophoresis on a DNA sequencing gel. This reveals a polymer ladder consisting of up to 45 residues. The polymer product from maize, after digestion with snake venom phosphodiesterase, gave only 5'-AMP and (phosphoribosyl)-AMP; the mean chain length of the polymer was 5 and 11 residues in two separate experiments. The optimum pH of the plant enzyme is greater than pH 7.0 in pea, wheat and maize; the optimum temperature for enzyme activity is approximately 15 degrees C. The Km for NAD+ for the enzyme from maize is estimated to be approximately 50 microM under optimal conditions. Several compounds (nicotinamide, deoxythymidine, 3-aminobenzamide, 3-methoxybenzamide and 5-bromodeoxyuridine) that specifically inhibit the animal enzyme also inhibit the enzyme from plants. The ratio of the IC50 for 5-bromodeoxyuridine to the IC50 for 3-aminobenzamide in maize is similar to that of the animal enzyme indicating that the enzyme involved is poly(ADP-ribose) polymerase and not mono(ADP-ribosyl) transferase. SDS gel electrophoresis and gel filtration analysis of a crude extract of maize nuclei indicate a molecular mass for poly(ADP-ribose) polymerase of approximately 114 kDa.

Internal lamin structures within G1 nuclei of human dermal fibroblasts

The nuclear lamina is a mesh-like network of fibres subjacent to the inner nuclear membrane that is believed to be involved in the specific spatial reorganisation of chromatin after mitosis. To determine how the lamina might be involved in chromatin reorganisation, we have performed indirect immunofluorescence studies on quiescent and proliferating human dermal fibroblasts (HDF). Two monoclonal antibodies recognising human lamins A and C and three different fixation methods were employed. In indirect immunofluorescence studies, cultures of quiescent cells displayed a uniform perinuclear distribution of the antibodies. In proliferating cultures two distinct populations of cells were observed: one population displayed a typical perinuclear antibody distribution, while the second population displayed an unusual pattern consisting of a series of spots and fibres within the nucleus. By inducing cell-cycle synchrony in cultures we were able to determine that the unusual internal distribution of the lamin antibodies was restricted to cells in G1. Optical sectioning and 3-D reconstruction of the lamina structures in G1 nuclei was performed with a confocal laser scanning microscope (CLSM). This revealed that the internal lamin structures consisted of small foci and fibres proliferating throughout the nucleus. These structures were shown to be closely associated with areas of condensed chromatin but not nuclear membrane. As cells progress towards S phase the internal lamin foci disappear.

Variation in the length of the lag phase following serum restimulation of mouse 3T3 cells

We have investigated the length of the lag phase (time taken for the first cells to enter S phase) and the kinetics of entry into DNA synthesis after serum restimulation of Swiss mouse 3T3 cell cultures that were allowed to become quiescent under different conditions. Cells were allowed to reach quiescence as a confluent monolayer in medium containing 10% (v/v) calf serum. Alternatively, when serum was reduced to 1% (v/v), cultures became quiescent at about 30% confluency and there was little cell to cell contact. The results show that the lag, or prereplicative phase becomes longer as the time spent in the quiescent state increases. This is the case in both confluent and non-confluent cultures. The rate of entry of cells into the S phase, however, remains the same under all conditions.

Characterization of the protein kinase activity of avian sarcoma virus src gene product

The avian sarcoma virus src gene product, p60src, has been purified 650-fold from cytoplasmic extracts of the rat tumor cell line RR1022 by using ammonium sulfate fractionation, hydrophobic chromatography on omega-aminohexyl agarose, and ion exchange chromatography on phosphocellulose. Partially purified p60src is a monomer, with a native molecular weight of about 60,000 and an apparent pI of 6.0. In immunoprecipitates, p60src catalyzed phosphorylation of anti-p60src IgG heavy chains within the variable (VH) domain, which contains the heavy chain portion of the antigen combining site. Crude preparations of p60src contained phosphatase activity able to cleave phosphate from IgG heavy chains; this activity was removed by the purification procedure, and partially purified p60src could phosphorylate the heavy chain of specific antibody in solution. Furthermore, purified p60src catalyzed phosphorylation in solution of the general protein kinase substrate, alpha-casein, strengthening the hypothesis that it may in fact function as a protein kinase in vivo.