Biomedical subjects

Hojin Moon

Publications and source records attributed to Hojin Moon.

5 recordsLinked to original sources

PubMed2005

An age-adjusted bootstrap-based Poly-k test.

The assumption of an asymptotic normal distribution of some test statistics may be invalid in certain dose-response trend tests. For instance, the survival-adjusted Cochran-Armitage test, known as the Poly-k test, is asymptotically standard normal under the null hypothesis. However, the asymptotic normality is not valid if there is a deviation from the tumour onset distribution that is assumed in this test or if the competing risks survival rates differ across groups. We develop an age-adjusted bootstrap-based method to assess the significance of assumed asymptotic normal tests for animal carcinogenicity data. The proposed method differs from conventional bootstrap methods in the aspect of preserving the mortality rate in each dose group under the null hypothesis of equal tumour incidence rates among the groups. We investigate an empirical distribution of the Poly-3 (P3) trend test statistic using the proposed age-adjusted bootstrap-based method and compare it with the P3 test statistic referenced to the assumed standard normal distribution. A simulation study is conducted to evaluate the robustness of these tests to various Weibull-family tumour onset distributions. The proposed method is applied to National Toxicology Program data sets to evaluate a dose-related trend of a test substance on the incidence of neoplasms.

Age Factors↗

PubMed2004

Effects of insulin-like growth factor binding protein-3 and farnesyltransferase inhibitor SCH66336 on Akt expression and apoptosis in non-small-cell lung cancer cells.

BACKGROUND: Overexpression of insulin-like growth factor binding protein-3 (IGFBP-3) induces apoptosis in non-small-cell lung cancer (NSCLC) cells in vitro and in vivo. However, Ras-mediated signaling pathways could develop resistance to apoptotic activities of IGFBP-3 in NSCLC cells. We thus evaluated the therapeutic potential of the combination of IGFBP-3 and SCH66336, a farnesyltransferase inhibitor that blocks Ras activation, in NSCLC cell lines. METHODS: The effects of the combination of adenoviral IGFBP-3 (Ad-IGFBP3) and SCH66336 on proliferation and apoptosis of NSCLC cell lines (H1299, H596, A549, H460, H358, H322, and H226B) were assessed in vitro and in vivo by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a flow cytometry-based terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling assay, western blot analyses, and an NSCLC xenograft tumor model. The specific effects of Ad-IGFBP 3 and SCH66336 on mitogen-activated protein kinase and Akt were assessed by using adenoviral vectors that express constitutively active MEK1 or constitutively active Akt. Synergy was assessed by median effect analysis. RESULTS: The combination of Ad-IGFBP3 and SCH66336 had synergistic antiproliferative effects in five cell lines (H1299, H596, A549, H460, and H322). Antiproliferative effects were accompanied by increased apoptosis in H460 cells in vitro. Overexpression of a constitutively active Akt but not a constitutively active MEK-1 rescued H460 cells from apoptosis induced by single or combined treatment of Ad-IGFBP3 and SCH66336. In H1299 tumor xenografts, Ad-IGFBP3 and SCH66336 was associated with decreased tumor volume, increased apoptosis, and decreased Akt levels. CONCLUSIONS: The combination of Ad-IGFBP3 and SCH66336 decreased Akt expression and increased apoptosis in NSCLC cells in vitro and in vivo. Simultaneous treatment with IGFBP-3 and SCH66336 may have the potential to be an effective therapeutic strategy in NSCLC.

Adenoviridae↗

PubMed2004

Phase II study of a multidisciplinary approach with induction chemotherapy, followed by surgical resection, radiation therapy, and consolidation chemotherapy for unresectable malignant thymomas: final report.

PURPOSE: To evaluate tumor resectability after induction chemotherapy and to determine disease-free and overall survival rates of patients with locally advanced unresectable thymoma that received a multimodal treatment regimen. PATIENTS AND METHODS: Twenty-two patients (9 men, 13 women) with histologically confirmed invasive thymoma were treated with a multidisciplinary regimen consisting of three courses of induction chemotherapy, surgical resection, and radiation therapy, followed by three courses of consolidation chemotherapy. The median age was 47 years (range, 25-70). Eleven patients had stage III disease, 10 patients, stage IVA, and one patient, IVB. The most common histologic type was lymphocytic. Induction chemotherapy consisted of 500 mg/m(2) of cyclophosphamide on day 1; doxorubicin (20 mg/m(2) per day) on days 1-3 via continuous infusion (a total of 60 mg/m(2)); cisplatin (30 mg/m(2) per day) on days 1-3 (a total of 90 mg/m(2)); and prednisone (100 mg per day) on days 1-5. This cycle was repeated three times at 3-4-week intervals. Patients then underwent surgery for tumor resection and received radiotherapy. Consolidation chemotherapy given at 80% of the induction chemotherapy doses of cyclophosphamide, doxorubicin, and cisplatin and 100% of the dose of prednisone was then repeated every 3-4 weeks for a total of three courses. RESULTS: Induction chemotherapy produced major responses in 17 (77%) of the 22 patients including 3 (14%) complete responses (CR) and 14 (63%) partial responses (PR). Twenty-one patients underwent surgical exploration: 16 (76%) had complete resection and 5 (24%) had incomplete resection; one patient refused surgery. All 22 patients received radiation therapy. Nineteen of 22 patients completed the planned therapy, and all but one had completed consolidation chemotherapy at the time of analysis. With a median follow-up time of 50.3 months, 18 of the 19 patients who completed the multidisciplinary approach were disease-free. Of the 22 patients originally registered, 20 were alive at the time of analysis (one patient died of endocarditis, and one died of recurrent disease). The overall survival rate was 95% at 5 years (95% confidence interval (CI), 0.87-1.0) and 79% at 7 years (95% CI, 0.55-1.0). The progression-free survival rates were 77% at 5 years (95% CI, 0.58-1.0) and 77% at 7 years (95% CI, 0.58-1.0). The major side effect from induction and consolidation chemotherapy was myelosuppression. Nine patients experienced grade III/IV neutropenia, which included neutropenic fever in two patients, and grade III thrombocytopenia in two patients. The most common nonhematologic side effects were fatigue, nausea and vomiting, and decreased appetite. One patient experienced acute respiratory distress syndrome after surgical resection and required a prolonged hospitalization. No patients developed cardiac toxic effects, and no surgical mortality occurred. CONCLUSIONS: The use of induction chemotherapy to optimize surgical resectability of thymoma followed by radiation therapy and consolidation chemotherapy lead to good control of residual disease and high overall survival rates. We believe that this combined multidisciplinary approach prolongs lives and may cure locally advanced unresectable malignant thymomas. Future prospective multi-institutional studies are needed to further verify or define the best treatment for this patient population.

Adult↗

PubMed2004

A comparison of microbial dose-response models fitted to human data.

A study of eight mathematical dose-response models for microbial risk assessment was conducted using infectivity and illness data on a variety of microbial pathogens from published studies with human volunteers. The purpose was to evaluate variability among the models for human microbial dose-response data in order to determine whether two-parameter models might suffice for most microbial dose-response data or whether three-parameter models should generally be fitted. Model variability was measured in terms of estimated ED01s and ED10s, with the view that these effective dose levels correspond to the lower and upper limits of the 1-10% risk range generally recommended for establishing benchmark doses in risk assessment. An investigation of the ranks of the ED01 and ED10 values among the models led to the conclusion that the two-parameter models captured at least as much uncertainty as the three-parameter models for the data examined. A further evaluation of the two-parameter models did not result in the selection of one "best" model, but it did provide some insights into the models' relative behavior. The model uncertainty analysis proposed by Kang et al. [Regulat. Toxicol. Pharmacol. 32 (2000) 68] using four two-parameter models was reinforced.

Algorithms↗

PubMed2003

Estimation of k for the poly-k test with application to animal carcinogenicity studies.

This paper extends the survival-adjusted Cochran-Armitage test in order to achieve improved robustness to a variety of tumour onset distributions. The Cochran-Armitage test is routinely applied for detecting a linear trend in the incidence of a tumour of interest across dose groups. To improve the robustness to the effects of differential mortality across groups, Bailer and Portier introduced the poly-3 test by a survival adjustment using a fractional weighting scheme for subjects not at full risk of tumour development. The performance of the poly-3 test depends on how closely it represents the correct specification of the time-at-risk weight in the data. Bailer and Portier further suggested that this test can be improved by using a general k reflecting the shape of the tumour onset distribution. In this paper, we propose a method to estimate k by equating the empirical lifetime tumour incidence rate obtained from the data based on the fractional weighting scheme to a separately estimated cumulative lifetime tumour incidence rate. This poly-k test with the statistically estimated k appears to perform better than the poly-3 test which is conducted without prior knowledge of the tumour onset distribution. Our simulation shows that the proposed method improves the robustness to various tumour onset distributions in addition to the robustness to the effects of mortality achieved by the poly-3 test. Large sample properties are shown via simulations to illustrate the consistency of the proposed method. The proposed methods are applied to analyse two real data sets. One is to find a dose-related linear trend on animal carcinogenicity, and the other is to test an effect of calorie restriction on experimental animals.

2-Acetylaminofluorene↗