Pharmacokinetics (PK) of Tiragolumab in First-in-Human Study in Patients with Mixed Solid Tumors (GO30103)

Tiragolumab is a first-in-class, fully human IgG1/kappa anti-TIGIT monoclonal antibody that blocks the binding of TIGIT to CD155 (the poliovirus receptor). We summarize the pharmacokinetics (PK) data from the phase 1a/1b GO30103 study of Q3W (every 3 weeks) sequential dosing of tiragolumab (2, 8, 30, 100, 400, 600, or 1200 mg) followed by atezolizumab (1200 mg), Q4W (every 4 weeks) sequential dosing (tiragolumab 840 mg followed by atezolizumab 1680 mg), and Q4W co-infusion (tiragolumab 840 mg plus atezolizumab 1680 mg). Serum samples were collected at multiple time points following tiragolumab and atezolizumab intravenous infusion in patients with solid tumors for PK and immunogenicity assessment. The serum PK profile of tiragolumab appeared to be biphasic, with a rapid distribution phase followed by a slower elimination phase when administered alone or in combination with atezolizumab. In phase 1a, across doses of tiragolumab ranging from 2 to 1200 mg (cycle 1), the geometric mean (GM), coefficient of variation (CV%), serum tiragolumab Cmax ranged from 0.682 to 270 µg/mL (18.6% to 36.5%) and Cmin ranged from 0.0125 to 75.3 µg/mL (0.0% to 24.2%). The GM systemic exposure (area under the plasma drug concentration-time curve, AUC0-21) ranged from 310 to 2670 µg day/mL (20.5% to 27.0%); interindividual variability in AUC0-21 ranged from 20.5% to 43.9%. Tiragolumab exposure increased in an approximately dose-proportional manner when administered alone or with atezolizumab at doses ≥100 mg. Postbaseline, 4/207 patients (1.9%) were positive for treatment-emergent antidrug antibodies (ADA) against tiragolumab, each at a single time point. Tiragolumab combined with atezolizumab demonstrated desirable PK properties, with no drug-drug interactions or immunogenicity liability. There were no meaningful differences in tiragolumab or atezolizumab exposure between the Q4W co-infusion and sequential dosing cohorts. ClinicalTrials.gov: NCT02794571 (date of registration June 6, 2016).

Efficacy of octenidine- and chlorhexidine-based wash-mitts against Candida albicans and Candida auris - a comparative study

BACKGROUND

Management of outbreaks of the newly emerging pathogen Candida auris may include use of antimicrobial wash-mitts for decolonization. However, currently there is little clinical evidence to support the wide adoption of 'whole-body decolonization' as part of the protocol to effectively manage C. auris outbreaks. The aim of this study was to investigate the chemical tolerance of C. auris compared with the surrogate test organism Candida albicans as established in the European Standards (EN).

METHODS

Two commercially available antiseptic-impregnated wash-mitts based on either chlorhexidine digluconate (CHG) or octenidine dihydrochloride (OCT) were studied. Comparison of susceptibility of C. auris and C. albicans was investigated based on the standardized test protocol EN 13624. Experiments were conducted using the impregnation liquid squeezed from the wash-mitts at a contact time of 30 s at different concentrations between 0.5% and 97% in the presence of low organic soiling.

FINDINGS

Yeasticidal efficacy according to EN 13624 was found for the OCT wash-mitts at 30 s at ≥10% concentration with C. albicans. In comparison, reduction ≥4 log10 was found at a much lower concentration of ≥1% for both C. auris strains. For the CHG wash-mitts, efficacy against C. albicans was below 2 log10 reduction at 97% concentration within 30 s. Efficacy against the two C. auris strains was around 3 log10 reduction.

CONCLUSION

Both C. auris strains were found to be significantly more susceptible when compared with C. albicans. Data also demonstrate that not all antiseptic-impregnated wash-mitts are equally effective against C. auris with OCT having a higher efficacy compared with CHG.

Comparisons of Clinical Outcomes between Weekday-Only and Full-Time, 24-Hour/7-Day Coverage Hospitalist Systems

BACKGROUND

Since the launch of pilot programs in 2016, varying ranges of hospitalist coverage exist in Korea. We evaluated the effects of differing depths of hospitalist coverage on clinical outcomes.

METHODS

This study retrospectively reviewed the records of 513 patients admitted to a medical hospitalist unit through emergency department at Seoul National University Hospital. The full-time group included patients admitted in 2018 who received 24/7 hospitalist service, whereas the weekday group included patients admitted in 2019 with only weekday hospitalist service. In-hospital clinical outcomes were compared between the two groups.

RESULTS

Unplanned intensive care unit admission rate was lower in the full-time group than in the weekday group (0.4% vs. 2.9%; P = 0.042). Discharges to local hospitals for subacute or chronic care were more frequent in the full-time group than in the weekday group (12.6% vs. 5.8%; P = 0.007). The weekday coverage was a predictive factor of in-ward mortality (odds ratio, 2.00; 95% confidence interval, 1.01-3.99) after adjusting for potential confounding factors.

CONCLUSION

Uninterrupted weekend coverage hospitalist service is helpful for care-plan decision and timely care transitions for acutely and severely ill patients.

Efficacy and tolerability of ramucirumab monotherapy or in combination with paclitaxel in gastric cancer patients from the Expanded Access Program Cohort by the Korean Cancer Study Group (KCSG)

BACKGROUND

Ramucirumab improves survival in gastric cancer patients. The efficacy and safety of ramucirumab outside of a clinical trial were evaluated using an expanded access program (EAP).

METHODS

Advanced gastric cancer patients treated with ramucirumab in combination with paclitaxel or with ramucirumab monotherapy in a Korean EAP were evaluated. Baseline characteristics were assessed for progression-free survival (PFS) and overall survival (OS), and adverse events were evaluated according to the treatment regimen.

RESULTS

Of 265 patients, 228 received ramucirumab plus paclitaxel, and 37 received ramucirumab monotherapy. Grade 3 or 4 neutropenia was more common with ramucirumab plus paclitaxel than with ramucirumab monotherapy (46.7 vs. 8.1%). Gastrointestinal (GI) perforation developed in seven patients (3.1%) in the ramucirumab plus paclitaxel group. The overall response and disease control rates were 16.6 and 66.3% in the ramucirumab plus paclitaxel group, and 5.4 and 37.8% in the ramucirumab monotherapy group, respectively. PFS and OS were 3.8 and 8.6 months in the ramucirumab plus paclitaxel group, and 1.8 and 6.4 months in the ramucirumab monotherapy group, respectively. In multivariate analysis, alkaline phosphatase, albumin, and neutrophil-to-lymphocyte ratio (NLR) were the independent prognostic factors for PFS, while albumin, NLR, number of metastatic sites, and large amount of ascites were independent prognostic factors for OS.

CONCLUSION

In the Korean EAP cohort, ramucirumab showed similar efficacy to the results of the previous trials for gastric cancer. However, the level of GI perforation was slightly increased in the ramucirumab plus paclitaxel group.

Cyclophosphamide, Methotrexate, and 5-Fluorouracil as Palliative Treatment for Heavily Pretreated Patients with Metastatic Breast Cancer: A Multicenter Retrospective Analysis

Purpose

This study aimed to evaluate the efficacy and safety of cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) chemotherapy beyond standard treatment for anthracycline- and taxane-pretreated metastatic breast cancer (MBC).

Methods

We consecutively enrolled 158 MBC patients who underwent CMF chemotherapy in a palliative setting at two academic hospitals in Korea between 2002 and 2016.

Results

The median age of the 158 enrolled patients was 51 years (range, 30-77 years). The enrolled patients were treated with a median of 5 lines of systemic treatment (range, 2-11) before CMF therapy, and the median time from diagnosis of MBC to CMF administration was 36.0 months (range, 7.1-146.7 months). The median number of cycles of CMF treatment was 3 (range, 1-19), and the relative dose intensity was 90.4%. The toxicity profile was mild, with an observed 3.1% of grade 2 and 5.0% of grade 3/4 neutropenia. Among 147 patients (93.0%) whose response to CMF was evaluated, the response rate was 10.9% (16/147), with complete response (CR) in one and partial response (PR) in 15. In addition, the disease control rate (calculated as CR+PR+stable disease) was 44.2% (65/147). The median progression-free survival and overall survival were 3.1 months (95% confidence interval [CI], 2.7-3.6) and 9.4 months (95% CI, 7.1-11.6), respectively.

Conclusion

CMF therapy is effective and tolerable as salvage treatment for heavily pretreated MBC.

Abstract 5869: Resistance mechanism against trastuzumab in HER2-positive cancer cells and its negation by Src inhibition

Background: Trastuzumab in combination with chemotherapy is a standard of care for patients with HER2-positive breast and gastric cancer. Resistance mechanism to trastuzumab, anti-HER2 therapy, includes multiple pathways. Among them, Src is not well known especially in HER2-positive gastric and biliary tract cancers. We investigated the role of Src involved in trastuzumab resistance and explored the potential of Src inhibition as a trastuzumab resistance overcoming strategy.

Methods: Four trastuzumab-resistant (HR) cells (SNU216HR, N87HR, SNU2670HR, SNU2773HR) were established from 2 HER2-amplified gastric cancer cells (SNU216, NCI-N87) and 2 HER2-amplified biliary tract cancer cells (SNU2670, SNU2773). For Src inhibition, bosutinib was used. MTT assay, colony formation assay, cell cycle analysis by FACS Calibur flow cytometer, and cell migration assay were done. Animal experiments were conducted to test anti-tumor effect of bosutinib using SNU2670 and SNU2670HR xenograft models.

Results: SNU2670HR/NCI-N87HR cells showed pSrc activation, in contrast, SNU216HR/SNU2773HR cells exhibited decreased pSrc expression. In these pSrc decreased HR cells, pFAK was elevated. Bosutinib downregulated Src-FAK signaling more obviously in Src activated HR cells than parental cells. In pSrc decreased HR cells, bosutinib reduced Src-dependent FAK phosphorylation to affect cell fate. Bosutinib inhibited the growth of both parental cells and HR cells, and induced apoptosis and G1 arrest in HR cells. Bosutinib suppressed HR cell migration more effectively compared with parental cells. Bosutinib exhibited potent tumor growth inhibition in both SNU2670 and SNU2670HR xenograft models and more significantly suppressed tumor growth in HR models.

Conclusion: Src activation may contribute to trastuzumab resistance in part in HER2-positive gastric and biliary tract cancer cells. Targeting Src might be a candidate strategy to overcome trastuzumab resistance in HER2-positive cancers.

Citation Format: Meihua Jin, Ah Rong Nam, Ji Eun Park, Ju Hee Bang, Yung Jue Bang, Do Youn Oh. Resistance mechanism against trastuzumab in HER2-positive cancer cells and its negation by Src inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5869. doi:10.1158/1538-7445.AM2017-5869

Abstract 1421: Evaluation of DDR-targeting strategy using ATR inhibitor in biliary tract cancer

Background: The DNA damage response (DDR) is a multicomplex network of signaling pathways involved in DNA damage repair, cell cycle checkpoints and apoptosis. The ataxia telangiectasia and Rad3-related (ATR) protein kinase is a key enzyme in the DDR that activates checkpoint kinase 1 (Chk1), resulting in cell cycle arrest. Tumor types with loss of ATM function and/or high replication stress are expected to be more susceptible to DDR targeting. In biliary tract cancer (BTC), DNA repair pathway, which includes BAP1, MSH6, BRCA1, ATM, MLH1, MSH2, is altered in about 20 % of cases. TP53 module is observed in 33.9% of BTC cases (Nat Genet 2015). The purpose of this study is to test DDR targeting strategy using ATR inhibitor in biliary tract cancer.

Methods: Using 9 kinds of BTC cells, MTT assay and colony formation assay were done for determining growth inhibitory effect of AZD6738, an ATR inhibitor. Cell cycle analysis was done by FACS Calibur flow cytometer and the methods described by Chou and Talalay were used to determine whether a synergistic effect existed between AZD6738 and cytotoxic chemotherapeutic agents (cisplatin, 5-FU, gemcitabine). The alkaline comet assay was done to measure of DNA damage in individual cells. Tumor xenografts model was used for in vivo test of AZD6738.

Results: Among 9 BTC cells, SNU478 and SNU869 were most sensitive to AZD6738, which showed low expression of both ATM and p53. AZD6738 blocked ATR-mediated Chk1 phosphorylation and increased rH2AX, a marker of DNA damage, in sensitive cells. AZD6738 significantly increased apoptosis (cleavage of PARP and caspase-7) and G2/M arrest, increased level of p21, and decreased cdc2. In addition, combination of AZD6738 and cytotoxic chemotherapeutic agents demonstrated synergistic effects in colony formation assay, cell cycle analysis and comet assay. In xenograft model of SNU478, AZD6738 monotherapy decreased tumor growth. The combination of AZD6738 and cisplatin showed more potent growth inhibitory effects, decreased Ki67, increased Tunel than monotherapy of each drug.

Conclusion: In BTC, DDR targeting strategy using ATR inhibitor demonstrated promising antitumor activity alone or in combination with cytotoxic chemotherapeutic agents. This supports further clinical development of DDR targeting strategy in BTC.

Citation Format: Ah Rong Nam, Ji Eun Park, Ju Hee Bang, Mei Hua Jin, Do Youn Oh, Yung Jue Bang. Evaluation of DDR-targeting strategy using ATR inhibitor in biliary tract cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1421. doi:10.1158/1538-7445.AM2017-1421

A randomized phase II study of gemcitabine plus Z-360, a CCK2 receptor-selective antagonist, in patients with metastatic pancreatic cancer as compared with gemcitabine plus placebo

Background

We investigated the efficacy and safety of 60, 120, or 240 mg of Z-360, which is a highly potent cholecystokinin2-receptor-selective antagonist, combined with gemcitabine in patients with metastatic pancreatic cancer.

Methods

Patients were randomly assigned in a 1:1:1:1 ratio to one of four treatment groups. Patients received 1000 mg/m² gemcitabine for each cycle and Z-360 tablets of 60 mg (GZ 60 mg group), 120, 240 mg or placebo tablets (Gem group) orally twice daily. The primary endpoint was overall survival (OS).

Results

The median OS was 1.3 months longer in the GZ 60 mg group compared with the Gem group (8.5 vs. 7.2 months) and the risk of death was reduced by 19% compared with the Gem group, although there were no statistically significant differences. The study treatments were well tolerated.

Conclusions

In this Phase II study, no statistically significant differences between the GZ groups and Gem group were detected in any analysis. However, Z-360 in dose of 60 mg tends to improve OS in patients with metastatic pancreatic cancer with low toxic effect. Further exploratory trials with other agents such as gemcitabine plus nab-paclitaxel might be beneficial.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-017-3351-4) contains supplementary material, which is available to authorized users.

First-in-human phase 1 study of margetuximab (MGAH22), an Fc-modified chimeric monoclonal antibody, in patients with HER2-positive advanced solid tumors

Background

Margetuximab is an anti-HER2 antibody that binds with elevated affinity to both the lower and higher affinity forms of CD16A, an Fc-receptor important for antibody dependent cell-mediated cytotoxicity (ADCC) against tumor cells. A Phase 1 study was initiated to evaluate the toxicity profile, maximum tolerated dose (MTD), pharmacokinetics, and antitumor activity of margetuximab in patients with HER2-overexpressing carcinomas.

Patients and methods

Patients with HER2-positive breast or gastric cancer, or other carcinomas that overexpress HER2, for whom no standard therapy was available, were treated with margetuximab by intravenous infusion at doses of 0.1-6.0 mg/kg for 3 of every 4 weeks (Regimen A) or once every 3 weeks (10-18 mg/kg) (Regimen B).

Results

Sixty-six patients received margetuximab (34 patients for Regimen A and 32 patients for Regimen B). The MTD was not reached for either regimen. Treatment was well-tolerated, with mostly Grade 1 and 2 toxicities consisting of constitutional symptoms such as pyrexia, nausea, anemia, diarrhea, and fatigue. Among 60 response-evaluable patients, confirmed partial responses and stable disease were observed in 7 (12%) and 30 (50%) patients, respectively; 26 (70%) of these patients had received prior HER2-targeted therapy. Tumor reductions were observed in over half (18/23, 78%) of response-evaluable patients with breast cancer including durable (>30 weeks) responders. Ex vivo analyses of patient peripheral blood mononuclear cell samples confirmed the ability of margetuximab to support enhanced ADCC compared with trastuzumab.

Conclusions

Margetuximab was well-tolerated and has promising single-agent activity. Further development efforts of margetuximab as single agent and in combination with other therapeutic agents are ongoing.

Trial Registration ID

NCT01148849.

Korean Cancer Patients' Awareness of Clinical Trials, Perceptions on the Benefit and Willingness to Participate

PURPOSE

The purpose of this study was to assess current levels of awareness of clinical trials (CTs), perceptions regarding their benefits and willingness to participate to CTs among Korean cancer patients.

MATERIALS AND METHODS

From December 2012 to August 2015, we distributed questionnaires to cancer patients receiving systemic anti-cancer therapy at Seoul National University Hospital, Seoul, Korea.

RESULTS

A total of 397 out of 520 requested patients (76.3%) responded to the survey. Among the 397 patients, 62.5% were female and the median age was 52 years. Overall, 97.4% (387/397) answered that they have at least heard of CTs. When asked about their level of awareness, 23.8% (92/387) answered that they could more than roughly explain about CTs. The average visual analogue scale score of CT benefit in all patients was 6.43 (standard deviation, 2.20). Patients who were only familiar with the term without detailed knowledge of the contents had the least expectation of benefit from CTs (p=0.015). When asked about their willingness to participate in CTs, 56.7% (225/397) answered positively. Patients with higher levels of awareness of CTs showed higher willingness to participate (p < 0.001). Heavily treated patients and patients with previous experience regarding CTs also showed a higher willingness to participate (p < 0.001). The perceived benefit of CTs was higher in the group willing to participate (p=0.026).

CONCLUSION

The patient's level of awareness regarding CTs was positively related to the positive perception and willingness to participate. Although the general awareness of CTs was high, a relatively large proportion of patients did not have accurate knowledge; therefore, proper and accurate patient education is necessary.

Association between information provision and decisional conflict in cancer patients

BACKGROUND

In this study, we aimed to identify demographic and clinical variables that correlate with perceived information provision among cancer patients and determine the association of information provision with decisional conflict (DC).

PATIENTS AND METHODS

We enrolled a total of 625 patients with cancer from two Korean hospitals in 2012. We used the European Organization for Research and Treatment of Cancer (EORTC) quality-of-life questionnaire (QLQ-INFO26) to assess patients' perception of the information received from their doctors and the Decisional Conflict Scale (DCS) to assess DC. To identify predictive sociodemographic and clinical variables for adequate information provision, backward selective logistic regression analyses were conducted. In addition, adjusted multivariate logistic regression analyses were carried out to identify clinically meaningful differences of perceived level of information subscales associated with high DC.

RESULTS

More than half of patients with cancer showed insufficient satisfaction with medical information about disease (56%), treatment (73%), other services (83%), and global score (80%). In multiple logistic regression analyses, lower income and education, female, unmarried status, type of cancer with good prognosis, and early stage of treatment process were associated with patients' perception of inadequate information provision. In addition, Information about the medical tests with high DCS values clarity [adjusted odds ratio (aOR), 0.54; 95% confidence interval (CI) 0.30-0.97] and support (aOR, 0.53; 95% CI 0.33-0.85) showed negative significance. For inadequate information perception about treatments and other services, all 5 DCS scales (uncertainty, informed, values clarity, support, and effective decision) were negatively related. Global score of inadequate information provision also showed negative association with high DCS effective decision (aOR, 0.43; 95% CI 0.26-0.71) and DCS uncertainty (aOR, 0.46; 95% CI 0.27-0.77).

CONCLUSION

This study found that inadequate levels of perceived information correlated with several demographic and clinical characteristics. In addition, sufficient perceived information levels may be related to low levels of DC.

The role of omega-3 fatty acid receptor GPR120 in insulin resistance

Obesity is the dominant cause of acquired insulin resistance, and it is the epidemic of obesity in the United States that is driving the markedly increasing incidence of type 2 diabetes. Adipocyte dysfunction and chronic low-grade adipose tissue (AT) inflammation are the major causes of insulin resistance. Abnormal accumulation and activation of AT macrophages (ATMs) and abnormal activation of the TLR4-mediated immune responses within ATMs are the key characters of the chronic low-grade AT inflammation associated with insulin resistance. We have recently shown that GPR120 acts as a physiological receptor of omega-3 fatty acid in macrophages and adipocytes, which mediate potent anti-inflammatory and insulin-sensitizing effects. The important role that GPR120 has in the control of inflammation raises the possibility that targeting this receptor could have therapeutic potential in many inflammatory diseases including obesity and type 2 diabetes. In this review paper, we discuss omega-3 fatty acid-sensing GPR120 and highlight the potential outcomes of targeting this receptor in ameliorating disease.

Phase III, multicenter, randomized trial of maintenance chemotherapy versus observation in patients with metastatic breast cancer after achieving disease control with six cycles of gemcitabine plus paclitaxel as first-line chemotherapy: KCSG-BR07-02

PURPOSE

The primary purpose of our study was to evaluate whether maintenance chemotherapy with paclitaxel/gemcitabine (PG) was superior to observation in improving progression-free survival (PFS) in patients with metastatic breast cancer (MBC) who achieved disease control with an initial six cycles of PG as their first-line treatment.

PATIENTS AND METHODS

The study was a prospective, randomized, multicenter, phase III trial. Patients MBC with who achieved disease control after six cycles of PG chemotherapy were randomly assigned to maintenance chemotherapy or observation until progression.

RESULTS

Of 324 patients from 10 centers enrolled, 231 patients with MBC exhibited disease control (complete response + partial response + stable disease) with first-line PG and were randomly assigned to maintenance chemotherapy (n = 116) or observation (n = 115). The median age was 48 years (range, 28 to 76 years), median follow-up was 33 months, and median number of chemotherapy cycles in the maintenance group after random assignment was six. The median PFS time after random assignment was longer in the maintenance group than in the observation group (7.5 v 3.8 months, respectively; P = .026). The median overall survival (OS) time was longer in the maintenance group than in the observation group (32.3 v 23.5 months, respectively; P = .047). The rate of grade 3 or higher neutropenia after random assignment was higher in the maintenance group than in the observation group (61% v 0.9%, respectively; P < .001).

CONCLUSION

In patients with MBC who achieved disease control with an initial six cycles of PG chemotherapy, maintenance PG chemotherapy resulted in better PFS and OS compared with observation.

A phase III, multicenter, randomized trial of maintenance versus observation after achieving clinical response in patients with metastatic breast cancer who received six cycles of gemcitabine plus paclitaxel as first-line chemotherapy (KCSG-BR 0702, NCT00561119)

1003

Background: Chemotherapy provides a survival benefit in patients with metastatic breast cancer (MBC), but the optimal duration of chemotherapy remains controversial. Primary purpose of the study was to evaluate whether the maintenance chemotherapy with gemcitabine/paclitaxel (GP), which is one of the two regimens which showed a survival gain from a randomized trial, is superior to observation in terms of progression free survival (PFS) in responding patients with MBC after 6 cycles of GP as first-line treatment. Methods: This study is a prospective, randomized, multi-center, phase III study. Patients who achieved response (CR+PR+SD) following 6 cycles of GP chemotherapy (gemcitabine 1250 mg/m2 on day 1 and 8 plus paclitaxel 175 mg/m2 on day 1 every 3 weeks) randomized to maintenance till progression or observation arm. The trial was conducted by the Korean Cancer Study Group (KCSG). Results: Among total 324 patients enrolled between 2007 and 2010 from 10 centers, 231 responding patients to were randomly assigned to maintenance chemotherapy (n=116) or observation (n=115). Median age was 49 (range 28-76). The numbers of hormone receptor (HR)+ve and HR-ve patients were 172 (74.5%) and 59 (25.5%), respectively. The median No. of chemotherapy cycles in maintenance group was 12 (range 6-32). During median 33 months of follow-up, median PFS was superior in maintenance than in observation (12.0 vs. 8.3 months, p=0.030). Patients < age 50 years (hazard ratio 0.50, p=0.001) and HR-ve patients (hazard ratio 0.52, p=0.019) received more benefit from maintenance chemotherapy in terms of PFS. Median OS was superior in maintenance than in observation (36.8 vs 28.0 months, p=0.047). Neurotoxicity (≥ grade 2) was more common in maintenance than in observation without statistical significance (41.7% vs 33.3%, p=0.210). Serial assessment of Quality of Life (QoL) did not show any significant difference between two groups. Conclusions: Maintenance GP chemotherapy for responding patients with MBC showed clinical benefit in terms of PFS and OS without impairment of QoL.

Heterodimerization of glycosylated insulin-like growth factor-1 receptors and insulin receptors in cancer cells sensitive to anti-IGF1R antibody

BACKGROUND

Identification of predictive biomarkers is essential for the successful development of targeted therapy. Insulin-like growth factor 1 receptor (IGF1R) has been examined as a potential therapeutic target for various cancers. However, recent clinical trials showed that anti-IGF1R antibody and chemotherapy are not effective for treating lung cancer.

METHODOLOGY/PRINCIPAL FINDINGS

In order to define biomarkers for predicting successful IGF1R targeted therapy, we evaluated the anti-proliferation effect of figitumumab (CP-751,871), a humanized anti-IGF1R antibody, against nine gastric and eight hepatocellular cancer cell lines. Out of 17 cancer cell lines, figitumumab effectively inhibited the growth of three cell lines (SNU719, HepG2, and SNU368), decreased p-AKT and p-STAT3 levels, and induced G 1 arrest in a dose-dependent manner. Interestingly, these cells showed co-overexpression and altered mobility of the IGF1R and insulin receptor (IR). Immunoprecipitaion (IP) assays and ELISA confirmed the presence of IGF1R/IR heterodimeric receptors in figitumumab-sensitive cells. Treatment with figitumumab led to the dissociation of IGF1-dependent heterodimeric receptors and inhibited tumor growth with decreased levels of heterodimeric receptors in a mouse xenograft model. We next found that both IGF1R and IR were N-linked glyosylated in figitumumab-sensitive cells. In particular, mass spectrometry showed that IGF1R had N-linked glycans at N913 in three figitumumab-sensitive cell lines. We observed that an absence of N-linked glycosylation at N913 led to a lack of membranous localization of IGF1R and figitumumab insensitivity.

CONCLUSION AND SIGNIFICANCE

The data suggest that the level of N-linked glycosylated IGF1R/IR heterodimeric receptor is highly associated with sensitivity to anti-IGF1R antibody in cancer cells.

Sunitinib synergizes the antitumor effect of cisplatin via modulation of ERCC1 expression in models of gastric cancer

We evaluated the effects of sunitinib monotherapy and in combination with cisplatin in human gastric cancer cell lines. Sunitinib showed antiproliferative effect in gastric cancer cells line with high PDGFRA expression. Knockdown of PDGFRA showed that sunitinib sensitivity was correlated with the basal expression of PDGFRA. Synergistic growth inhibitory activity in combination with cisplatin was identified. We further explored how sunitinib potentiated the activity of cisplatin. We found that sunitinib treatment resulted in the down-regulation of ERCC1 expression via the modulation of PDGFRA expression in gastric cancer cells. The effect was verified via SNU484 xenograft model. Our data support the rationale of clinical trial using sunitinib in combination of cisplatin in gastric cancer.

Down-regulation of mitogen-inducible gene 6, a negative regulator of EGFR, enhances resistance to MEK inhibition in KRAS mutant cancer cells

Previously, we found that KRAS mutant cancer cells showed variable response to AZD6244, a MEK inhibitor through differential activation of EGFR/AKT. To investigate its mechanism, we performed cDNA microarray using four KRAS mutant cancer cells. We found that treatment with AZD6244 reduced the expression of mitogen-inducible gene 6 (MIG6), a negative feedback regulator for EGFR, in AZD6244-resistant cells, while activity of EGFR and AKT was increased in these cells. Reconstitution or knockdown of MIG6 expression affected cancer cell responses to AZD6244. Treatment with a combination of EGFR inhibitor and AZD6244 inhibited cell proliferation synergistically without activation of AKT in AZD6244-resistant cells. Our study provides a mechanism of differential response to MEK inhibition in KRAS mutant cancer.

Versatility of right gastroepiploic and gastroduodenal arteries for arterial reconstruction in adult living donor liver transplantation

BACKGROUND

In cases where there is severe intimal dissection in the recipient hepatic artery (HA), or if the HA has been used already and additional operations are needed due to graft rejection or arterial occlusion, an alternative is necessary. In the present study, we have reported the feasibility of using the right gastroepiploic artery (RGEA) and gastroduodenal artery (GDA) in various situations where the HA is not a feasible option.

METHODS

Among 463 patients who underwent primary adult-to-adult living donor liver transplantation from January 2002 to July 2010, eight subjects required alternative vessels. Four recipients displayed severe intimal injury associated with previous transarterial chemoembolization (TACE); two, required a salvage operation due to hepatic artery thrombosis (HAT); and two, retransplantations due to chronic rejection. The RGEA was used in five and the GDA in three patients.

RESULTS

Postoperative Doppler ultrasonography and three-dimensional computed tomography showed patent arterial flow in all patients. However, HAT recurred in one patient who underwent a salvage operation with the RGEA; she died 2 months later. Two other patients died due to wound infection and respiratory failure within 3 months despite intact hepatic arterial flow. Four patients had no further complications during follow-up (mean = 33 months).

CONCLUSION

Although there was a discrepancy in the diameter of the HA and the RGEA (or GDA), there was no problem with mobilization and microanastomosis. We therefore believe that these vessels can be good alternatives when the hepatic artery is unavailable.

Individualized tumor response testing for prediction of response to Paclitaxel and Cisplatin chemotherapy in patients with advanced gastric cancer

The purpose of our study was to determine the most accurate analytic method to define in vitro chemosensitivity, using clinical response as reference standard in prospective clinical trial, and to assess accuracy of adenosine triphosphate-based chemotherapy response assay (ATP-CRA). Forty-eight patients with chemo-naïve, histologically confirmed, locally advanced or metastatic gastric cancer were enrolled for the study and were treated with combination chemotherapy of paclitaxel 175 mg/m(2) and cisplatin 75 mg/m(2) for maximum of six cycles after obtaining specimen for ATP-CRA. We performed the receiver operator characteristic curve analysis using patient responses by WHO criteria and ATP-CRA results to define the method with the highest accuracy. Median progression free survival was 4.2 months (95% confidence interval [CI]: 3.4-5.0) and median overall survival was 11.8 months (95% CI: 9.7-13.8) for all enrolled patients. Chemosensitivity index method yielded highest accuracy of 77.8% by ROC curve analysis, and the specificity, sensitivity, positive and negative predictive values were 95.7%, 46.2%, 85.7%, and 75.9%. In vitro chemosensitive group showed higher response rate (85.7% vs. 24.1%) (P=0.005) compared to chemoresistant group. ATP-CRA could predict clinical response to paclitaxel and cisplatin chemotherapy with high accuracy in advanced gastric cancer patients. Our study supports the use of ATP-CRA in further validation studies.

Abstract A252: KRAS mutant lung cancer cells are differentially responsive to MEK inhibition due to AKT or STAT3 activation: Implication for combinatorial approach

KRAS is frequently mutated in non-small cell lung cancer (NSCLC), resulting in the activation of the MEK/ERK pathway. High-throughput mutation profile has shown that lung cancer frequently harbors co-mutation of cancer related genes. Therefore, given that cancer cells have multiple genetic alterations, combinatorial therapeutic strategy is demanded for effective cancer therapy. To address this, we first characterized MEK dependence in four NSCLC cells. Two cells (H358, A549) carried KRAS mutation only, and the other two (H23, H157) harbored co-mutation of KRAS/PTEN. H358 cells with KRAS mutation only were sensitive to MEK inhibition. However, the other KRAS mutant A549 cells were resistant to MEK inhibition. Previously, we have shown that dual inhibition of EGFR and MEK signaling shows a synergistic effect on KRAS mutant gastric cancer cells by suppressing compensatory activation of AKT. Here we also observed that this combination was effective in KRAS mutant A549 cells. However, the combination was ineffective in H23 and 157 cells with co-mutation of KRAS/PTEN. Compared to KRAS mutant/PTEN wild-type cells, STAT3 was significantly activated following MEK inhibition in KRAS/PTEN co-mutant cells. Combined STAT3 inhibition by a JAK2 inhibitor or gene knockdown with MEK inhibition blocked STAT3 activation, synergistically suppressed cell growth, and induced apoptosis in co-mutant cells. Taken together, our study provides molecular insights that help explain the heterogeneous response to MEK inhibition in KRAS mutant lung cancers, and presents a rationale for the clinical investigation of combination of MEK and EGFR inhibitor or MEK and STAT3 inhibitor depending on PTEN status.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A252.

Combination of EGFR and MEK1/2 inhibitor shows synergistic effects by suppressing EGFR/HER3-dependent AKT activation in human gastric cancer cells

EGFR tyrosine kinase inhibitors have shown promising efficacy in the treatment of tumors with EGFR mutations and amplifications. However, tyrosine kinase inhibitors have also proven ineffective against most tumors with EGFR wild-type (WT) alleles. Although some genetic changes, including the KRAS mutation, have been shown to confer resistance to tyrosine kinase inhibitors, novel strategies for the treatment of cancer patients with tumors harboring EGFR WT alleles have yet to be thoroughly delineated. The principal objective of this study was to improve our current understanding of drug interactions between EGFR and MAP/ERK kinase (MEK) inhibitors in an effort to gain insight into a novel therapeutic strategy against EGFR WT tumors. Using a panel of human EGFR WT gastric cancer cell lines, we showed that gastric cancer cells harboring the KRAS mutation were selectively sensitive to MEK inhibition as compared with those cells harboring KRAS and PI3K mutations and KRAS WT alleles. However, all cell lines were found to be resistant to EGFR inhibition. The results from Western blots and phosphoprotein arrays showed that, in MEK inhibitor resistant cell lines, AKT was activated through the EGFR/HER3/PI3K pathway following AZD6244 (ARRY-142886) treatment. Blockade of this feedback mechanism through the targeting of MEK and EGFR resulted in detectable synergistic effects in some cell lines in vitro and in vivo. Our results provide the basis for a rational combination strategy against human EGFR WT gastric cancers, predicated on the understanding of cross-talk between the MEK and EGFR pathways.

Combination chemotherapy with capecitabine and cisplatin for patients with metastatic hepatocellular carcinoma

BACKGROUND

We evaluated the efficacy and toxicity of combination chemotherapy with capecitabine and cisplatin (XP) in patients with metastatic hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

From September 2003 to July 2007, we enrolled patients with HCC who had more than one measurable extrahepatic metastatic lesion. Patients received oral capecitabine (2000 mg/m(2)/day) with a schedule of 2 weeks on and 1 week off and cisplatin (60 mg/m(2)) on the first day of the 3-week cycle.

RESULTS

The study cohort consisted of 32 patients with a median age of 53 years. Overall response rate was 6.3% and disease control rate was 34.4%. The median time to progression (TTP) was 2.0 months [95% confidence interval (CI) 1.5-2.4] and the median overall survival (OS) time was 12.2 months (95% CI 6.5-17.8). The grade 3/4 hematologic toxic effects included thrombocytopenia (7.6%), neutropenia (4.3%) and anemia (2.1%). The grade 3/4 non-hematologic toxic effects included elevated hepatic aminotransferase (12.9%), jaundice (3.2%), mucositis (3.2%) and nausea (3.2%). There was no treatment-related mortality.

CONCLUSIONS

Based on the observed response rate and TTP, XP combination chemotherapy showed modest antitumor efficacy in patients with metastatic HCC as systemic first-line treatment. However, XP combination chemotherapy showed tolerable toxicity and demonstrated favorable OS time.

Simvastatin plus irinotecan, 5-fluorouracil, and leucovorin (FOLFIRI) as first-line chemotherapy in metastatic colorectal patients: a multicenter phase II study

BACKGROUND

Simvastatin has demonstrated anti-tumor activity in preclinical studies via tumor cell senescence, anti-angiogenesis, and apoptosis. This phase II trial evaluated the efficacy and toxicity profile of conventional FOLFIRI chemotherapy plus simvastatin in metastatic colorectal cancer patients.

METHODS

Patients received irinotecan 180 mg/m(2) as a 90-min infusion followed by leucovorin 200 mg/m(2) in a 2-h infusion, and then 5-FU 400 mg/m(2) bolus injection followed by 2,400 mg/m(2) as a 46-h continuous infusion. Treatment cycles were repeated every 2 weeks until documented disease progression, unacceptable toxicity, or patient's refusal. Simvastatin 40 mg tablet was given once daily per oral everyday during the period of chemotherapy without a rest.

RESULTS

From October 2005 to June 2006, 49 patients were enrolled. The overall response rate (ORR) was 46.9% (95% CI, 31.0-58.8) by intent-to-treat analysis and 45.8% (95% CI, 33.3-62.8) by per-protocol analysis. There were one complete response (CR) and 22 partial responses (PRs). Both CR and PRs were confirmed at least 4 weeks later. The disease-control rate was 83.7% (95% CI, 73.4-94.0). The median follow-up duration was 25.6 months (range, 20.9-28.8 months). The median survival of all patients was 21.8 months (95% CI, 14.4, 29.2). The median TTP was 9.9 months (95% CI, 6.4, 13.3). No patients experienced additional adverse effect that was definitely caused by simvastatin drug therapy in this trial.

CONCLUSION

The combination of simvastatin plus FOLFIRI was a feasible regimen with promising antitumor activity.

Trastuzumab inhibits the growth of human gastric cancer cell lines with HER2 amplification synergistically with cisplatin

HER2 has been found to be amplified in 10-20% of gastric cancers, and is correlated with poor outcome. The aims of this study were to recognize HER2 amplification in gastric cancer cell lines via fluorescence in situ hybridization and to evaluate the growth inhibitory effect of trastuzumab in HER2-amplified cell lines. To elucidate the mechanism of the growth inhibition, we performed cell cycle analysis and immunoblotting of downstream molecules. We also conducted drug interaction studies of trastuzumab with other chemotherapeutic agents. HER2 amplification was newly identified only in SNU-216 cells, and trastuzumab moderately inhibited the growth of SNU-216 cells and positive controls. Trastuzumab-mediated G1 arrest occurred with increased expression of p27(KIP1) and decreased cyclins. Phosphorylation of HER2 and downstream molecules, STAT3, AKT, and ERK, was also inhibited by trastuzumab. Treatment of SNU-216 cells with trastuzumab plus cisplatin resulted in a synergistic inhibitory effect, whereas treatment of SNU-216 cells with trastuzumab plus 5-FU, or trastuzumab plus oxaliplatin produced an additive effect. These results suggest that trastuzumab combined with chemotherapeutic agents can be active against gastric cancer with HER2 amplification.

A phase II trial of S-1 and cisplatin in patients with metastatic or relapsed biliary tract cancer

BACKGROUND

Optimal chemotherapy for advanced biliary tract cancer (BTC) is yet to be defined. We carried out this study to evaluate the efficacy and toxicity of combination chemotherapy with S-1 and cisplatin in metastatic or relapsed BTC.

PATIENTS AND METHODS

Patients with pathologically proven BTC were eligible. The chemotherapy regimen consisted of S-1 (40 mg/m(2) p.o. b.i.d. from D1-14) and cisplatin (60 mg/m(2) on D1), repeated every 3 weeks.

RESULTS

Fifty-one BTC patients (metastatic:relapsed = 37:14, Gall-bladder:intrahepatic bile ducts:extrahepatic bile ducts = 16:25:10) were enrolled from January 2005 to December 2006. Median age was 57 years (range, 31-71) and most patients had a good performance status. The overall response rate was 30% [95% confidence interval (CI), 17.3-42.7] and complete response was observed in two patients (4%), partial response in 13 (26%), stable disease in 21 (42%), and progressive disease in 9 (18%). With a median follow-up of 12.4 months, the median time to progression was 4.8 months (95% CI, 3.3-6.3) and median overall survival was 8.7 months (95% CI, 6.0-11.4). Major toxic effects were grade 3/4 neutropenia (8.9% of all cycles) and febrile neutropenia was observed in six cycles (2.7% of all cycles).

CONCLUSION

Combination chemotherapy with S-1 and cisplatin was a moderately effective outpatient-based regimen in BTC patients. Toxic effects were moderate but manageable.

Targeted RNA interference of phosphatidylinositol 3-kinase p110-beta induces apoptosis and proliferation arrest in endometrial carcinoma cells

Phosphatidylinositol 3-kinase (PI3K) signalling plays a pivotal role in intracellular signal transduction pathways involved in cell growth, cellular transformation, and tumourigenesis. PI3K is overexpressed in many human cancers, including endometrial carcinomas, one of the most common female genital tract malignancies. Here, we used small interfering RNA (siRNA) targeted to PI3K p110-beta to determine whether inhibition of the beta isoform could be a potential therapeutic target for endometrial carcinoma. In this study, treatment of HEC-1B endometrial cancer cells with PI3K p110-beta-specific siRNA resulted in increased apoptosis and decreased tumour cell proliferation. Depletion of PI3K p110-beta decreased the protein levels of AKT1, AKT2, pAKT, and mTOR-downstream targets of PI3K. Knock-down of PI3K p110-beta by siRNA also induced decreased expression of cyclin E and Bcl-2, suggesting that PI3K p110-beta stimulates tumour growth, at least in part by regulating cyclin E and Bcl-2. Thus, our results indicate that siRNA-mediated gene silencing of PI3K p110-beta may be a useful therapeutic strategy for endometrial cancers overexpressing PI3K p110-beta.

Artificial nutrition and hydration in terminal cancer patients: the real and the ideal

INTRODUCTION

To better understand current practice relating to artificial nutrition/hydration in terminal cancer patients, we enrolled terminal cancer patients who were admitted at Seoul National University Boramae Hospital for supportive care only and who died with a duration of hospital stay to death of more than 1 week between 2003 and 2004. We detailed oral intake and intravenous nutrition/hydration status on admission, 1 week after admission, and 2 days before death. Administered calories and changes in these according to time and "DNR" (do-not-resuscitate) status were noted.

RESULTS

Of the total 165 patients, oral intake was possible in 84 patients (50.9%) on admission, in 79 patients (47.8%) on 1 week after admission, and in 29 patients (17.5%) 2 days before death (p < 0.01). Intravenous nutrition/hydration was administered to 133 patients (80.6%) on admission, to 125 patients (75.7%) at 1 week, and to 137 patients (83.0%) 2 days before death (p = 0.7). The calories administered to the patient by oral intake were 393 kcal on admission, 353 kcal 1 week after admission, and 89 kcal 2 days before death. In addition, the calories delivered by intravenous fluid were 369, 386 and 465 kcal, respectively. Near to death, calories by oral intake continuously reduced (p < 0.01) and intravenous calories continuously increased (p = 0.04), but total administered calories reduced (p = 0.03). Intravenous nutrition/hydration stopped after the attainment of the advance directive of DNR in 9% of patients.

CONCLUSION

This study showed the high prevalence of artificial nutrition/hydration, especially intravenous infusion, in Korean terminal cancer patients compared with situation in other countries. More studies are needed to verify the efficacy of artificial nutrition/hydration in terminal cancer patients.

Involvement of the ser-glu-pro motif in ligand species-dependent desensitisation of the rat gonadotrophin-releasing hormone receptor

There are two forms of gonadotrophin-releasing hormone (GnRH), GnRH-I and GnRH-II, in the vertebrate brain. Both GnRH-I and GnRH-II are thought to interact with the type-I GnRH receptor (GnRHR). The present study attempted to demonstrate whether GnRH-I and GnRH-II induce differential desensitisation of GnRHR and to identify the motif involved. Time course inositol phosphate (IP) accumulation assay reveals that, in cells expressing the wild-type rat GnRHR, GnRH-I induced continuous increase in IP production, whereas GnRH-II-induced IP production rate at later time points (30-120 min after ligand treatment) became attenuated. However, in cells expressing the mutant receptor in which the Ser-Glu-Pro (SEP) motif in extracellular loop 3 was replaced by Pro-Glu-Val (PEV), IP accumulation rates at later time points were more decreased by GnRH-I than GnRH-II. Ca2+ responses to repetitive GnRH applications reveal that GnRH-II desensitised the wild-type receptor faster than GnRH-I, whereas the opposite situation was observed in the PEV mutant. In addition, cell surface loss of GFP-tagged wild-type receptor was more facilitated by GnRH-II than GnRH-I, whereas that of the GFP-tagged PEV mutant receptor was more enhanced by GnRH-I than GnRH-II. The present study indicates that the SEP motif is potentially responsible for ligand species-dependent receptor desensitisation. Together, these results suggest that GnRH-I and GnRH-II may have different effects on mammalian type-I GnRHR via modulation of desensitisation rates.

Antibiotic use during the last days of life in cancer patients

The purpose of this study is to document infection and to better understand current practice relating to antibiotic use and its effect in terminal cancer patients. We retrospectively reviewed patients with terminal stage cancer who were admitted to Seoul National University Boramae Hospital for symptom control only, and who finally died between March 2003 and April 2004. A total of 141 patients were enrolled. Mean duration from admission to death was 31.2 days. A total of 104 patients (75.2%) experienced a febrile episode, and physicians considered 113 patients (80.1%) developed a clinical infection. Total 119 patients (84.4%) received antibiotics. For 90 patients (63.8%), antibiotics were used until the day of death. After using antibiotics, 48% of fevers were controlled, and 31% of organism-proven cases were resolved. Symptomatic improvement of infection was achieved in 18 patients (15.1%), but 66 patients (55.4%) showed no improvement. Improved leucocytosis was achieved by 17% and C Reactive Protein elevation by 29%. In conclusion, our study reveals a high rate of infection and a high rate of antibiotic prescription during the last month of life in cancer patients. But symptomatic improvement was not achieved in more than half of the patients. Further study should be undertaken to clarify the benefit of antibiotics in terminal stage cancer patients.

Differential effects of gonadotropin-releasing hormone (GnRH)-I and GnRH-II on prostate cancer cell signaling and death

CONTEXT

GnRH is known to directly regulate prostate cancer cell proliferation, but the precise mechanism of action of the peptide is still under investigation.

OBJECTIVE

This study demonstrates differential effects of GnRH-I and GnRH-II on androgen-independent human prostate cancer cells.

RESULTS

Both GnRH-I and GnRH-II increased the intracellular Ca(2+) concentration ([Ca(2+)](i)) either through Ca(2+) influx from external Ca(2+) source or via mobilization of Ca(2+) from internal Ca(2+) stores. Interestingly, the [Ca(2+)](i) increase was mediated by activation of the ryanodine receptor but not the inositol trisphosphate receptor. Trptorelix-1, a novel GnRH-II antagonist but not cetrorelix, a classical GnRH-I antagonist, completely inhibited the GnRH-II-induced [Ca(2+)](i) increase. Concurrently at high concentrations, trptorelix-1 and cetrorelix inhibited GnRH-I-induced [Ca(2+)](i) increase, whereas at low concentrations they exerted an agonistic action, inducing Ca(2+) influx. High concentrations of trptorelix-1 but not cetrorelix-induced prostate cancer cell death, probably through an apoptotic process. Using photoaffinity labeling with (125)I-[azidobenzoyl-D-Lys(6)]GnRH-II, we observed that an 80-kDa protein specifically bound to GnRH-II.

CONCLUSIONS

This study suggests the existence of a novel GnRH-II binding protein, in addition to a conventional GnRH-I receptor, in prostate cancer cells. These data may facilitate the development of innovatory therapeutic drugs for the treatment of prostate cancer.

A new venous conduit utilizing the recipient portal vein branches for segment V in adult partial liver transplantation

Right anterior-medial lobe congestion due to temporary clamping of segment V and/or VIII is common in the operative theater during adult donor right lobe liver transplantation, the most common procedure in our institute. We have used an autogenous saphenous vein conduit to recipient portal vein tributaries in 15 cases, as a "Y-to-I venoplasty" since January 2004. The recipient portal vein is transected 5 mm proximal to its bifurcation and extended to both sides with partial hepatic dissection. The "Y-to-I venoplasty" is made by suture closure of the portal vein transversely to form a tube. The average length is 7.5 cm with a 1.3 cm width. One end of "Y-to-I venoplasty" conduit is anastomosed to the donor segment V branch on the back table. And the other end is anastomosed directly to the IVC via a new window or the middle hepatic vein stump in recipient. The phase distension of the conduit with respiration is noted in the operative field. A 6/15 (40%) patency rate, was observed by CT angiography at the second postoperative week. All-patient conduits showed good flow on serial examinations at the 60th postoperative day. This new venous graft, made of recipient portal vein is a good conduit for segment V decongestion in adult right lobe partial liver transplantation.

Identification of Amino Acid Residues That Direct Differential Ligand Selectivity of Mammalian and Nonmammalian V1a Type Receptors for Arginine Vasopressin and Vasotocin

Arginine vasotocin (VT) is the ortholog in all nonmammalian vertebrates of arginine vasopressin (AVP) in mammals. We have previously cloned an amphibian V1atype vasotocin receptor (VT1R) that exhibited higher sensitivity for VT than AVP, while the mammalian V1a type receptor (V1aR) responded better to AVP than VT. In the present study, we identified the amino acid residues that confer differential ligand selectivity for AVP and VT between rat V1aR and bullfrog VT1R (bfVT1R). A chimeric rat V1aR having transmembrane domain (TMD) VI to the carboxyl-terminal tail (C-tail) of bfVT1R showed a reverse ligand preference for AVP and VT, whereas a chimeric VT1R with TMD VI to the C-tail of rat V1aR showed a great increase in sensitivity for AVP. A single mutation (Ile(315(6.53)) to Thr) in TMD VI of V1aR increased the sensitivity for VT, while a single mutation (Phe(313(6.51)) to Tyr or Pro(334(7.33)) to Thr) reduced sensitivity toward AVP. Interestingly the triple mutation (Phe(313(6.51)) to Tyr, Ile(6.53) to Thr, and Pro(7.33) to Thr) of V1aR increased sensitivity to VT but greatly reduced sensitivity to AVP, behaving like bfVT1R. Further, like V1aR, a double mutant (Tyr(306(6.51)) to Phe and Thr(327(7.33)) to Pro) of bfVT1R showed an increased sensitivity to AVP. These results suggest that Phe/Tyr(6.51), Ile/Thr(6.53), and Pro/Thr(7.33) are responsible for the differential ligand selectivity between rat V1aR and bfVT1R. This information regarding the molecular interaction of VT/AVP with their receptors may have important implications for the development of novel AVP analogs.

Membrane-proximal region of the carboxyl terminus of the gonadotropin-releasing hormone receptor (GnRHR) confers differential signal transduction between mammalian and nonmammalian GnRHRs

Recently, we demonstrated that the mammalian type-I GnRH receptor (GnRHR) has a high preference for the phospholipase C/protein kinase C (PLC/PKC)-linked signaling pathway, whereas non-mammalian bullfrog (bf) GnRHRs couple to both adenylate cyclase/protein kinase A (AC/PKA)- and PLC/PKC-linked signaling pathways. In the pre-sent study, using AC/PKA-specific reporter (cAMP-responsive element-luciferase) and PLC/PKC-specific reporter (serum-responsive element-luciferase) systems, we attempted to identify the motif responsible for this difference. A deletion of the intracellular carboxyl-terminal tail (C tail) of bfGnRHR-1 remarkably decreased its ability to induce the AC/PKA-linked signaling pathway. Further dissection of the C tail indicated that an HFRK motif in the membrane-proximal sequence of bfGnRHR-1 C tail is a minimal requirement for the AC/PKA-linked signaling pathway as the addition of this motif to rat GnRHR or deletion of it from bfGnRHR-1 significantly affected the ability to induce the AC/PKA-linked signaling pathway. Deletion or addition of the HFRK motif, however, did not critically influence the PLC/PKC-linked signaling pathway. These results indicate that the HFRK motif in the membrane-proximal region confers the differential signal transduction pathways between mammalian and nonmammalian GnRHRs.

Molecular cloning, pharmacological characterization, and histochemical distribution of frog vasotocin and mesotocin receptors

The neurohypophysial nonapeptides vasotocin (VT) and mesotocin (MT) are the amphibian counterparts of arginine vasopressin (AVP) and oxytocin (OT). We have here reported the cloning and functional characterization of the receptors for vasotocin (VTR) and mesotocin (MTR) in two species of frog, Rana catesbeiana and Rana esculenta. The frog VTR and MTR cDNAs encode proteins of 419 and 384 amino acids respectively. Frog VTR exhibits a high degree of sequence identity with the mammalian AVP-1a (V1a) receptor while the frog MTR possesses a high degree of sequence identity with the mammalian OT receptor. Activation of VTR induced both c-fos promoter- and cAMP-responsive element (CRE)-driven transcriptional activities, while activation of MTR induced c-fos promoter-driven transcriptional activity but failed to evoke CRE-driven transcriptional activity, suggesting differential G protein coupling between VTR and MTR. The VTR exhibited the highest sensitivity for VT followed by OT>AVP approximately MT, whereas the MTR showed preferential ligand sensitivity for MT>OT>VT>AVP. A V1a agonist but not V2 and OT agonists substantially activated both VTR and MTR with a similar sensitivity. V1a, V2 and OT antagonists inhibited MT-induced MTR activation but not VT-induced VTR activation. In the frog brain, VTR and MTR mRNAs were found to be widely expressed in the telencephalon, diencephalon and mesencephalon, and exhibited very similar regional distribution. In the pituitary, VTR and MTR were expressed in the distal and intermediate lobes but were virtually absent in the neural lobe. Taken together, these data indicated that, although the distribution of VTR and MTR largely overlaps in the frog brain and pituitary, VT and MT may play distinct activities owing to the ligand selectivity and different signaling pathways activated by their receptors.

Granzyme A activates an endoplasmic reticulum-associated caspase-independent nuclease to induce single-stranded DNA nicks

The cytotoxic T lymphocyte protease granzyme A (GzmA) initiates a novel caspase-independent cell death pathway characterized by single-stranded DNA nicking. The previously identified GzmA substrate SET is in a multimeric 270-420-kDa endoplasmic reticulum-associated complex that also contains the tumor suppressor protein pp32. GzmA cleaved the nucleosome assembly protein SET after Lys(176) and disrupted its nucleosome assembly activity. The purified SET complex required only GzmA to reconstitute single-stranded DNA nicking in isolated nuclei. DNA nicking occurred independently of caspase activation. The SET complex contains a 25-kDa Mg(2+)-dependent nuclease that degrades calf thymus DNA and plasmid DNA. Thus, GzmA activates a DNase (GzmA-activated DNase) within the SET complex to produce a novel form of DNA damage during cytotoxic T lymphocyte-mediated death.

Plasma concentrations of haloperidol are related to CYP2D6 genotype at low, but not high doses of haloperidol in Korean schizophrenic patients

AIMS

This study was carried out to evaluate the influence of CYP2D6 genotype on the steady state plasma concentrations of haloperidol and reduced haloperidol in Korean schizophrenic patients.

METHODS

One hundred and twenty Korean schizophrenic patients treated with various, clinically determined, doses of haloperidol (range 3-60, median 20 mg day-1) during monotherapy were recruited. CYP2D6 genotypes were determined by analysis of the CYP2D6*10 allele using allele-specific PCR and the CYP2D6*5 allele by long-PCR. Steady state plasma concentrations of haloperidol and reduced haloperidol were analysed by h.p.l.c.

RESULTS

Twenty-three (19.2%), 60 (50.0%), 1 (0.8%), 33 (27.5%) and 3 patients (2.5%) possessed the CYP2D6 genotypes *1/*1, *1/*10, *1/*5, *10/*10 and *10/*5, respectively. The allele frequencies of CYP2D6*1, *10 and *5 were 44.6%, 53.8% and 1.7%, respectively. Significant relationships between dose and plasma concentrations of haloperidol (linear; r2 = 0.60, P < 0.0001) and reduced haloperidol (quadratic equation; r(2) = 0.67) were observed. Overall, the concentrations normalized for dose (C/D) of haloperidol were significantly different between the CYP2D6*1/*1, *1/*10 and *10/*10 genotype groups (one-way ANOVA; P = 0.028). No significant differences between the genotype groups were found with respect to the C/D of reduced haloperidol (P = 0.755). However, in patients with daily doses less than 20 mg, significant differences in the C/D of haloperidol (P = 0.003), but not of reduced haloperidol, were found between the three major genotype groups. In patients with doses higher than 20 mg, no differences were found between the genotype groups for either haloperidol or reduced haloperidol. 68 patients (57%) used benztropine, an antimuscarinic agent. All four patients with a *5 allele (one together with *1 and three with *10) were found to use benztropine. The patients homozygous for the *1 allele seemed to need less benztropine than the patients with one or two mutated alleles (Fisher's exact test; P = 0.036).

CONCLUSIONS

The dose-corrected steady state plasma concentrations of haloperidol, but not of reduced haloperidol, were significantly different between the CYP2D6*1/*1, *1/*10 and *10/*10 genotype groups when doses lower than 20 mg haloperidol were given. No differences were found at higher doses. These results suggest the involvement of CYP2D6 in the metabolism of haloperidol at low doses of haloperidol (< 20 mg daily), while another enzyme, probably CYP3A4, contributes at higher doses.

Inhibitory activity of alternative splice variants of the bullfrog GnRH receptor-3 on wild-type receptor signaling

Recently we characterized three distinct GnRH receptors in the bullfrog (bfGnRHR-1, bfGnRHR-2, and bfGnRHR-3). In the present study, we further investigated the expression and function of splice variants, generated from the primary bfGnRHR-3 transcript by exon skipping (splice variant 1), intron retention (splice variants 2 and 3), and/or transcriptional slippage (splice variant 4), apart from the constitutively spliced form (wild-type). Cellular expression and function of the splice variants were examined using a transient expression system. Immunoblot analysis revealed that the wild-type receptor and all splice variant proteins were expressed in transfected HeLa cells with no significant differences in expression levels. These splice variants showed a very low binding affinity to ligand and did not induce signal transduction in response to GnRH treatment. Interestingly, cotransfection of the wild-type with splice variants 2--4, but not with splice variant 1, significantly inhibited wild-type receptor-mediated signaling. Subcellular localization analysis of green fluorescent protein-tagged wild-type and splice variant proteins revealed that the wild-type receptor protein was mainly localized in the cell membrane, whereas the splice variant 1 protein was exclusively detected in the cytoplasm. The splice variant 2--4 proteins, however, were found in both the cell membrane and cytoplasm. The inhibition of wild-type receptor signaling by splice variants 2--4 and the subcellular localization of splice variants 2-4 suggest a possible physical interaction of splice variants 2--4 with the wild-type receptor protein. In addition, the ratio of mRNA levels of the wild-type to splice variants 2--4 significantly varied from hibernation (wild-type < splice variants 2--4) to the prebreeding season (wild-type > splice variants 2--4). Collectively, these results suggest that alternative splicing of the bfGnRHR-3 primary transcript plays a role in fine-tuning GnRH receptor function in amphibians.

A role for CD21/CD35 and CD19 in responses to acute septic peritonitis: a potential mechanism for mast cell activation

Although it is now appreciated that mast cell-mediated release of TNF-alpha is critical for resolution of acute septic peritonitis, questions remain as to how mast cells are activated upon peritoneal bacterial infection. Clues to how this may occur have been derived from earlier studies by Prodeus et al. in which complement proteins C3 and C4 were shown to be required for survival following cecal ligation and puncture (CLP), a model for acute septic peritonitis. To evaluate the mechanism for mast cell activation in the CLP model, complement receptor CD21/CD35-deficient mice (Cr2(null)) were examined in the present study. Along with CD19-deficient (CD19(null)) mice, these animals exhibit decreased survival following CLP compared with wild-type littermates. Injection of IgM before CLP does not change survival rates for Cr2(null) mice and only partially improves survival of CD19(null) mice, implicating CD21/CD35 and CD19 in mast cell activation. Interestingly, early TNF-alpha release is also impaired in Cr2(null) and CD19(null) animals, suggesting that these molecules directly affect mast cell activation. Cr2(null) and CD19(null) mice demonstrate an impairment in neutrophil recruitment and a corresponding increase in bacterial load. Examination of peritoneal mast cells by flow cytometry and confocal microscopy reveals the expression and colocalization of CD21/CD35 and CD19. Taken together, these findings suggest that the engagement of complement receptors CD21/CD35 along with CD19 on the mast cell surface by C3 fragments may be necessary for the full expression of mast cell activation in the CLP model.

Neuroleptic drugs alter the dopamine transporter-mediated uptake and release of dopamine: a possible mechanism for drug-induced tardive dyskinesia

A bovine dopamine transporter (bDAT) cDNA was transfected into CV-1 cells, a cell line that lacks vesicular storage and release mechanisms. Using this cell line, the effects of neuroleptic drugs on DAT-mediated uptake and release of dopamine (DA) were examined. All of the neuroleptic drugs tested, inhibited DA uptakes in DAT expressing cells, and most of them were shown to promote spontaneous release of DA at the same time. These results imply that neuroleptic drugs would cause an overflow of DA in the synaptic cleft of extrapyramidal dopaminergic neurons, which could be one of the possible mechanisms of drug-induced tardive dyskinesia.

Plasma t-PA and PAI-1 antigen concentrations in non-insulin dependent diabetic patients: implication for diabetic retinopathy

Parameters of fibrinolysis, including basal plasma tissue type plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) antigen levels were studied in 49 non-insulin dependent diabetic patients (23 men, 26 women: ages 51.3 +/- 14.9 years) and 16 age matched non-diabetic subjects (9 men, 7 women ages 49.8 +/- 12.2 years) as a control group. Compared to a control group, the diabetic patients had a significantly higher mean plasma t-PA antigen (4.94 +/- 2.68 vs 3.20 +/- 2.30 ng/ml) and PAI-1 antigen (34.86 +/- 16.71 vs. 17.60 +/- 15.36 ng/ml) levels (P < 0.05). Significant univariate correlations were observed between t-PA and body mass index (BMI) (P = 0.0009, r = 0.7217), and PAI-1 were positively correlated with BMI and FBS (fasting blood sugar) in the total diabetic patients (P = 0.0003, r = 0.7217; P = 0.0477, r = 0.2858, respectively). In diabetic patients with proliferative diabetic retinopathy, both PAI-1 and t-PA antigen levels were significantly lower than those of diabetic patients with negative or background retinopathy (P = < 0.05). There were no significant differences of the plasma t-PA and PAI-1 levels between diabetic patients with micro- and macroproteinuria. This study conducted on non-insulin dependent diabetic patients suggests that they have significantly higher t-PA and PAI-1 antigen levels than do control subjects, and these findings appear to correlate negatively with proliferative retinopathy observed among the patients studied.

Plasma t-PA and PAl-1 antigen concentrations in non-insulin dependent diabetic patients: effects of treatment modality on fibrinolysis

Basal plasma tissue type plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAl-1) antigen levels were studied in 49 non-insulin dependent diabetic patients (23 men, 26 women: ages 51.3 +/- 14.9 years) and 16 age matched non-diabetic subjects (9 men, 7 women: ages 49.8 +/- 12.2 years) as a control group. Compared to a control group, the diabetic patients had a significantly higher mean t-PA antigen (5.15 +/- 3.02 vs 3.20 +/- 2.30 ng/ml) and PAl-1 antigen (35.89 +/- 18.59 vs 17.60 +/- 15.36 ng/ml) levels (p < 0.05). Plasma t-PA antigen level was not influenced by each treatment modality. There was a significant decrease of plasma PAl-1 antigen level after Metformin administration compared to that of before Metformin administration (39.74 +/- 19.39 vs 25.14 +/- 16.18 ng/ml) (p < 0.05), and the insulin-treated group showed a tendency for a decrease of plasma PAl-1 antigen levels after insulin administration but this did not reach statistical significance (29.93 +/- 15.37 vs 17.32 +/- 10.60 ng/ml). Sulfonylurea did not change both plasma t-PA and PAl-1 antigen levels. In conclusion, diabetic patients have high t-PA and PAl-1 antigen levels. Biguanide reduced plasma PAl-1 antigen levels, which might play some helpful role in the improvement of chronic complications in NIDDM.

Euglobulin fibrinolytic activity in NIDDM patients

The euglobulin fibrinolytic activity was measured in 56 non-insulin-dependent diabetics and 118 age-matched healthy controls before and after venous occlusion for 5 min at 100 mmHg of the left antecubital vein. In the basal state, fibrinolytic activity was impaired in diabetics compared with controls (93.1 +/- 6.7 vs 101.6 +/- 0.9 BAU) (P less than 0.05) and plasma fibrinogen level was increased but this did not reach statistical significance (467.3 +/- 264.1 vs 359.2 +/- 200.2 mg/dl). In diabetics, stimulated fibrinolysis following venous occlusion was depressed compared with controls (110.6 +/- 3.9 vs 121.6 +/- 1.9 BAU) (P less than 0.05). No relation of fibrinolytic activity to age, duration of diabetes, obesity, serum triglyceride, HbA1c, or 24 h proteinuria was demonstrated. In the diabetic retinopathy group, the fibrinolytic activity was lower than in the non-retinopathy group. Diabetics with long-standing diabetes (10 years or more) who remained free from retinopathy had significantly increased fibrinolytic activity than the diabetics with short-standing diabetes (less than 10 years) who have developed retinopathy (P less than 0.05). These findings imply a poor fibrinolytic activity, not in all diabetics, but only in those with retinopathy, and this may play a role in the development of diabetic retinopathy.

Fibrinolytic response to standardized venous occlusion in different age groups

The purpose of this study was to find out the range and distribution of fibrinolytic response to standardized venous occlusion in healthy volunteers and to determine whether there were any differences according to age and sex. In 118 healthy volunteers (55 males, 63 females) of various age groups, the total fibrinolytic activity in euglobulin fractions was measured by a well controlled fibrin plate method before and after venous occlusion of 5 minutes at 100 mmHg. The difference between our method and previous methods is that we occluded for a relatively shorter duration than that of previous studies (15-20 minutes) at constant pressure (100 mmHg), instead of midway between systolic and diastolic pressure. This method was reliable and reproducible as a tool to qualify and assess the fibrinolytic activity capacity of individuals. The results showed that there was no difference in basal fibrinolytic activity and the response to stimuli in various age groups (p greater than 0.25) and in male and female groups (0.1 less than p less than 0.375).