FDG-PET for Pharmacodynamic Assessment of the Fatty Acid Synthase Inhibitor C75 in an Experimental Model of Lung Cancer

Purpose Fatty acid synthase (FAS) is an emerging target for anticancer therapy with a variety of new FAS inhibitors being explored in preclinical models. The aim of this study was to use positron emission tomography with [¹⁸F]fluorodeoxyglucose (FDG-PET) to monitor the effects of the FAS inhibitor C75 on tumor glucose metabolism in a rodent model of human A549 lung cancer. Materials and Methods After a baseline FDG-PET scan, C75 was administered and post-treatment scans were performed serially. FAS activity was measured in treated animals ex vivo by [¹⁴C]acetate incorporation in animals euthanized in parallel to those imaged. Results Longitudinally measured metabolic volumes of interest and tumor/background ratios demonstrated a transient, reversible decrease in glucose metabolism and tumor metabolic volume after treatment, with the peak effect seen at 4 h. FDG-PET measurements correlated with changes in tumor FAS activity measured ex vivo. Conclusions Because C75 causes an effect that is shorter in duration than expected, modification of the current weekly dosing regimen should be considered. These results demonstrate the utility of small animal FDG-PET in assessing the pharmacodynamics of new anticancer agents in preclinical models. Jae Sung Lee and Hajime Orita contributed equally to this work     

Variable levels of chromosomal instability and mitotic spindle checkpoint defects in breast cancer

Cytogenetic analyses have revealed that many aneuploid breast cancers have cell-to-cell variations of chromosome copy numbers, suggesting that these neoplasms have instability of chromosome numbers. To directly test for possible chromosomal instability in this disease, we used fluorescent in situ hybridization to monitor copy numbers of multiple chromosomes in cultures of replicating breast cancer-derived cell lines and nonmalignant breast epithelial cells. While most (7 of 9) breast cancer cell lines tested are highly unstable with regard to chromosome copy numbers, others (2 of 9 cell lines) have a moderate level of instability that is higher than the "background" level of normal mammary epithelial cells and MCF-10A cells, but significantly less than that seen in the highly unstable breast cancer cell lines. To evaluate the potential role of a defective mitotic spindle checkpoint as a cause of this chromosomal instability, we used flow cytometry to monitor the response of cells to nocodazole-induced mitotic spindle damage. All cell lines with high levels of chromosomal instability have defective mitotic spindle checkpoints, whereas the cell lines with moderate levels of chromosomal instability (and the stable normal mammary cells and MCF10A cells) arrest in G(2) when challenged with nocodazole. Notably, the extent of mitotic spindle checkpoint deficiency and chromosome numerical instability in these cells is unrelated to the presence or absence of p53 mutations. Our results provide direct evidence for chromosomal instability in breast cancer and show that this instability occurs at variable levels among cells from different cancers, perhaps reflecting different functional classes of chromosomal instability. High levels of chromosomal instability are likely related to defective mitotic checkpoints but not to p53 mutations.     

Promoter hypermethylation of resected bronchial margins: a field defect of changes?

PURPOSE: Histologically positive bronchial margins after resection for non-small cell lung cancer are associated with shortened patient survival due to local recurrence. We hypothesized that DNA promoter hypermethylation changes at bronchial margins could be detected in patients with no histological evidence of malignancy and that they would reflect epigenetic events in the primary tumor. EXPERIMENTAL DESIGN: Bronchial margins, primary tumor, bronchoalveolar fluid, and paired nonmalignant lung were obtained from 20 non-small cell lung cancer patients who underwent a lobectomy or greater resection. Disease-specific recurrence was the primary end point. The methylation status of p16, MGMT, DAPK, SOCS1, RASSF1A, COX2, and RARbeta was examined using methylation-specific polymerase chain reaction. RESULTS: All malignancies had methylation in at least one locus. Concordance of one gene with an identical epigenetic change in the tumor or bronchial margin was observed in 85% of patients. Only one patient had methylation at the bronchial margin for a gene that was not methylated in the corresponding tumor. Median time to recurrence was 37 months (range, 5-71 months). There were two local recurrences and five metastases. There were no significant correlations between DNA methylation in tumor, margins, or bronchoalveolar fluid specimens and either regional recurrence or distant metastases. CONCLUSIONS: Histologically negative bronchial margins of resected non-small cell lung cancer exhibit frequent hypermethylation changes in multiple genes. These hyper-methylation abnormalities are also present in the primary tumor and thus may represent a field defect of preneoplastic changes that occurs early in carcinogenesis.     

Increased fatty acid synthase is a therapeutic target in mesothelioma.

Many common human cancer tissues express high levels of fatty acid synthase (FAS), the primary enzyme for the synthesis of fatty acids, and the differential expression of FAS between normal and neoplastic tissues has led to the consideration of FAS as a target for anticancer therapy. To investigate the potential of targeting FAS for the treatment of pleural mesothelioma, we first determined whether FAS is overexpressed in human mesothelioma. By immunohistochemistry, we found 22 of 30 human mesothelioma tissue samples tested to express significantly increased levels of FAS compared with normal tissues, including mesothelium. To further explore FAS as a therapeutic target in mesothelioma, we established a nude mouse xenograft model for human mesothelioma using the H-Meso cell line. The i.p. xenografts of this cell line have high levels of FAS expression and fatty acid synthesis pathway activity and grow along mesothelial surfaces in a manner similar to the growth pattern of human mesothelioma. Growth of these tumor xenografts was essentially abolished in mice treated with weekly i.p. injections of C75, a synthetic, small molecule inhibitor of FAS, at levels that resulted in no significant systemic toxicity except for reversible weight loss. These results suggest that FAS may be an effective target for pharmacological therapy in a high proportion of human mesotheliomas.     

Classification of small cell lung cancer and pulmonary carcinoid by gene expression profiles.

Small cell lung cancer is a common type of lung cancer that is generally classified within the spectrum of neuroendocrine lung neoplasms. Using high-density cDNA arrays, we profiled gene expression of small cell lung cancers and compared these expression profiles to those of normal bronchial epithelial cells and pulmonary carcinoids, which are classified as benign neuroendocrine tumors. We found the overall expression profiles of two small cell lung cancer cell lines, two microdissected tissue samples of primary small cell lung cancer, and cultured bronchial epithelial cells to be relatively similar to one another, with an average Pearson correlation coefficient for these comparisons of 0.63. However, we found the expression profiles of small cell lung cancers (and bronchial epithelial cells) to be surprisingly dissimilar to those of two samples of pulmonary carcinoid tumors, with an average correlation coefficient for these comparisons of 0.20. We then compared the pulmonary carcinoid expression profiles to those of two samples of infiltrating astrocytic brain cancers (oligodendroglioma and high-grade astrocytoma) and found similarity of gene expression among these four samples (average correlation coefficient, 0.57). These gene expression profiles suggest that small cell lung cancers are closely related to (and possibly derived from) epithelial cells, and that pulmonary carcinoids are related to neural crest-derived brain tumors. More generally, our results suggest that broad profiles of gene expression may reveal similarities and differences between tumors that are not apparent by traditional morphological criteria.     

Family history and recurrence of febrile seizures

To determine the value of a detailed family history for the assessment of the risk of recurrence of febrile seizures, 115 children who visited the emergency room of an academic children's hospital were studied prospectively. The recurrence risk of febrile seizures was analysed in relation to the child's family history and the proportion of relatives affected by febrile seizures using Kaplan-Meier estimates and Cox proportional hazard models. A first degree family history positive for febrile seizures (parents or siblings affected by febrile seizures) increased a child's two year recurrence risk from 27 to 52%. No significant increase of recurrence risk for febrile seizures was found in children with second degree relatives (grandparents and uncles/aunts) or cousins only affected by febrile seizures. Recurrence risk was significantly correlated with the proportion of first degree relatives affected by febrile seizures: risks were 27, 40, and 83% in children whose proportion was 0, 0-0.5, and > or = 0.5 respectively. Analysis of the recurrence risk in relation to a weighted proportion, adjusted for the attained age and sex of first degree relatives, showed similar results. It is concluded that the application of the proportion of first degree relatives affected by febrile seizures generates a more differentiated assessment of the recurrence risk of febrile seizures.