Comparison of mode of action of four hepatocarcinogens: a model-based approach.

Within the scope of the Rat Liver Foci Bioassay the model carcinogens N-nitrosomorpholine (NNM), 2-acetylaminoflouren (2-AAF), phenobarbital (PB), and clofibrate (CF) were analyzed concerning their potency and dose-response relationship to induce foci of altered hepatocytes (FAHs), which are known to be precursor lesions of liver adenoma and carcinoma. The medium-term experiment follows an initiation-promotion protocol using diethylnitrosamine (DEN) as initiator. The present report deals with the application of two biologically based models for hepatocarcinogenesis, the two-stage clonal expansion model (TSCEM), and a color-shift model with beta distributed growth rates (CSMbeta). Both models yield similar conclusions concerning the mode of action of the carcinogens. However, the fit of CSMbeta appears closer to the observations than the fit of TSCEM. The analysis shows that application of a single dose of DEN has a persistent effect on the rate of FAH induction, especially in female rats. Overall, striking differences in the effect of the carcinogens were observed between male and female animals. 2-AAF shows a strong promoting effect in males, whereas in females the initiating effect dominates. NNM has both initiating and promoting effect, but in females, the rate of FAH formation seems to reach saturation at high dose. In the doses applied in the present experiment, PB has the weakest carcinogenic effect. Although PB alone does not induce FAH during the observation period, it increases the rate of FAH formation when applied following initiation with DEN. CF reduces the number and area fraction of GSTP-stained FAH, probably because it suppresses the placental form of glutathione S-transferase-positive phenotype.

Investigating the formation and growth of alpha-particle radiation-induced foci of altered hepatocytes: a model-based approach.

The effect of alpha-particle radiation on the formation and increase in volume of preneoplastic liver lesions was investigated in an animal experiment. Mice were divided into four groups; two groups received different doses of the alpha-particle-labeled antibody (213)Bi-anti CD19 ((213)Bi-CD19), Thorotrast was administered to one group, and one group was left untreated. Hematoxylin and eosin-stained liver sections were evaluated for preneoplastic foci of altered hepatocytes 6, 12 and 17 months after treatment. The density and size distribution of focal transections were described by a mechanistic model for the formation and growth of foci of altered hepatocytes. The negative control and the (213)Bi-CD19 groups were combined to investigate the dose-response relationship for model parameters describing the formation and growth of foci of altered hepatocytes. Although (213)Bi-CD19 was given by single injection, the effect on formation of foci of altered hepatocytes lasted for the entire experiment. Likelihood-ratio tests comparing nested models showed that (213)Bi-CD19 increases the rates of both the formation and growth of foci of altered hepatocytes. Comparing the effects of Thorotrast with those of (213)Bi-CD19 revealed that Thorotrast had an effect similar to that of a low dose of (213)Bi-CD19, but the effect on focus formation was slightly smaller whereas the effect on focus growth was slightly higher for Thorotrast, in contrast to a low dose of (213)Bi-CD19.

Application of a color-shift model with heterogeneous growth to a rat hepatocarcinogenesis experiment.

Several hypotheses are established to describe the formation and progression of foci of altered hepatocytes (FAH). A common model of hepatocarcinogenesis is the mutation model (MM), which is based on the assumption that cells have to undergo multiple successive changes on their way from the normal to the malignant stage. This model describes growth and phenotype change of foci on the cellular level and is based on the assumption that single cells change their phenotype through mutation into the next stage and proliferate according to a linear stochastic birth-death process. In contrast, the color-shift model (CSM) was introduced by Kopp-Schneider et al. to describe that whole colonies of altered hepatocytes simultaneously alter their phenotype. In this paper two modifications of the color-shift model are considered which allow the growth rate to vary from focus to focus. All four models are compared with respect to their ability to predict number and radii of foci in a rat hepatocarcinogenesis experiment, in which rats were treated with the carcinogens N-nitrosomorpholine, 2-acetylaminofluoren and Phenobarbital. Maximum likelihood parameter estimates are given, and predicted and empirical FAH size distributions are visualized. The Cramer-von-Mises distance is used as a measure for the discrepancy between empirical and theoretical size distributions.

Randomized phase II study of the anti-epidermal growth factor receptor monoclonal antibody cetuximab with cisplatin versus cisplatin alone in patients with metastatic triple-negative breast cancer.

PURPOSE: Epidermal growth factor receptor is overexpressed in metastatic triple-negative breast cancers (mTNBCs), an aggressive subtype of breast cancer. Our randomized phase II study investigated cisplatin with or without cetuximab in this setting. PATIENTS AND METHODS: Patients who had received no more than one previous chemotherapy regimen were randomly assigned on a 2:1 schedule to receive no more than six cycles of cisplatin plus cetuximab or cisplatin alone. Patients receiving cisplatin alone could switch to cisplatin plus cetuximab or cetuximab alone on disease progression. The primary end point was overall response rate (ORR). Secondary end points studied included progression-free survival (PFS), overall survival (OS), and safety profiles. Analyses included a significance level of α = .10 with no adjustments for multiplicity. RESULTS: The full analysis set comprised 115 patients receiving cisplatin plus cetuximab and 58 receiving cisplatin alone; 31 patients whose disease progressed on cisplatin alone switched to cetuximab-containing therapy. The ORR was 20% (95% CI, 13 to 29) with cisplatin plus cetuximab and 10% (95% CI, 4 to 21) with cisplatin alone (odds ratio, 2.13; 95% CI, 0.81 to 5.59; P = .11). Cisplatin plus cetuximab resulted in longer PFS compared with cisplatin alone (median, 3.7 v 1.5 months; hazard ratio [HR], 0.67; 95% CI, 0.47 to 0.97; P = .032). Corresponding median OS was 12.9 versus 9.4 months (HR, 0.82; 95% CI, 0.56 to 1.20; P = .31). Common grade 3/4 adverse events included acne-like rash, neutropenia, and fatigue. CONCLUSION: While the primary study end point was not met, adding cetuximab to cisplatin doubled the ORR and appeared to prolong PFS and OS, warranting further investigation in mTNBC.

Application of a two-phenotype color-shift model with heterogeneous growth to a rat hepatocarcinogenesis experiment.

The color-shift model (CSM) was introduced by Kopp-Schneider et al. [1] to describe formation and progression of foci of altered hepatocytes (FAH). It incorporates the field-effect hypothesis which postulates that entire colonies of altered hepatocytes simultaneously alter their phenotype. In the original CSM, FAH grow with deterministic growth rate and change their phenotype after an exponentially distributed waiting time. A modification of the original color-shift model (CSM beta) is presented here in which the growth rate varies from focus to focus according to a beta distribution. The concept of an exponentially distributed waiting time to phenotype change is modified to the concept of a random radius at which phenotype changes and this radius is modelled as beta distributed. The original and the modified CSM are applied to data from an initiation-promotion rat hepatocarcinogenesis experiment with diethylnitrosomorpholine (DEN) and N-nitrosomorpholine (NNM), in which two phenotypes of FAH were observed in hematoxilin/eosin (H&E) stained liver sections. The Cramer-von-Mises Distance is used as a measure for the discrepancy between empirical and theoretical size distributions. Comparisons of model fit show that considerable improvement is obtained for CSM beta compared to the original CSM.