ABSTRACT
BACKGROUND: Although a high level of thymidylate synthase (TS) expression in malignant tumours has been suggested to be related to a reduced sensitivity to the antifolate drug pemetrexed, no direct evidence for such an association has been demonstrated in non-small cell lung cancer (NSCLC). We have now investigated the effect of TS overexpression on pemetrexed sensitivity in NSCLC cells. METHODS: We established NSCLC cell lines that stably overexpress TS and examined the effects of such overexpression on the cytotoxicity of pemetrexed both in vitro and in xenograft models. We further examined the relation between TS expression in tumour specimens from NSCLC patients and the tumour response to pemetrexed by immunohistochemical analysis. RESULTS: The sensitivity of NSCLC cells overexpressing TS to the antiproliferative effect of pemetrexed was markedly reduced compared with that of control cells. The inhibition of DNA synthesis and induction of apoptosis by pemetrexed were also greatly attenuated by forced expression of TS. Furthermore, tumours formed by TS-overexpressing NSCLC cells in nude mice were resistant to the growth-inhibitory effect of pemetrexed observed with control tumours. Finally, the level of TS expression in tumours of non-responding patients was significantly higher than that in those of responders, suggestive of an inverse correlation between TS expression and tumour response to pemetrexed. CONCLUSION: A high level of TS expression confers a reduced sensitivity to pemetrexed. TS expression is thus a potential predictive marker for response to pemetrexed-based chemotherapy in NSCLC patients.
Subject(s)
Antimetabolites, Antineoplastic/pharmacology , Carcinoma, Non-Small-Cell Lung/drug therapy , Carcinoma, Non-Small-Cell Lung/enzymology , Glutamates/pharmacology , Guanine/analogs & derivatives , Lung Neoplasms/drug therapy , Lung Neoplasms/enzymology , Thymidylate Synthase/biosynthesis , Animals , Carcinoma, Non-Small-Cell Lung/genetics , Cell Line, Tumor , Guanine/pharmacology , Humans , Immunohistochemistry , Lung Neoplasms/genetics , Male , Mice , Mice, Nude , Pemetrexed , Retrospective Studies , Thymidylate Synthase/antagonists & inhibitors , Thymidylate Synthase/geneticsABSTRACT
BACKGROUND: Thymidylate synthase (TS), a key enzyme in the de novo synthesis of thymidine, is an important chemotherapeutic target for malignant tumours including lung cancer. Although inhibition of TS has an antiproliferative effect in cancer cells, the precise mechanism of this effect has remained unclear. METHODS: We examined the effects of TS inhibition with an RNA interference-based approach. The effect of TS depletion on the growth of lung cancer cells was examined using colorimetric assay and flow cytometry. RESULTS: Measurement of the enzymatic activity of TS in 30 human lung cancer cell lines revealed that such activity differs among tumour histotypes. Almost complete elimination of TS activity by RNA interference resulted in inhibition of cell proliferation in all tested cell lines, suggestive of a pivotal role for TS in cell proliferation independent of the original level of enzyme activity. The antiproliferative effect of TS depletion was accompanied by arrest of cells in S phase of the cell cycle and the induction of caspase-dependent apoptosis as well as by changes in the expression levels of cyclin E and c-Myc. Moreover, TS depletion induced downregulation of the antiapoptotic protein X-linked inhibitor of apoptosis (XIAP), and it seemed to activate the mitochondrial pathway of apoptosis. CONCLUSION: Our data provide insight into the biological relevance of TS as well as a basis for clinical development of TS-targeted therapy for lung cancer.
Subject(s)
Lung Neoplasms/drug therapy , Thymidylate Synthase/genetics , Adenocarcinoma/enzymology , Adenocarcinoma/genetics , Adenocarcinoma/pathology , Apoptosis , Carcinoma, Large Cell/enzymology , Carcinoma, Large Cell/genetics , Carcinoma, Large Cell/pathology , Carcinoma, Small Cell/enzymology , Carcinoma, Small Cell/genetics , Carcinoma, Small Cell/pathology , Carcinoma, Squamous Cell/enzymology , Carcinoma, Squamous Cell/genetics , Carcinoma, Squamous Cell/pathology , Caspase 3/metabolism , Cell Cycle/genetics , Cell Division/genetics , Cell Line, Tumor , Cyclin E/genetics , Cytosol/metabolism , Gene Deletion , Gene Expression Regulation, Neoplastic , Humans , Immunoblotting , Lung Neoplasms/enzymology , Lung Neoplasms/genetics , Lung Neoplasms/pathology , Mitochondria/metabolism , Proto-Oncogene Proteins c-myc/genetics , RNA Interference , S Phase/genetics , Thymidylate Synthase/antagonists & inhibitors , Thymidylate Synthase/deficiency , Thymidylate Synthase/metabolismABSTRACT
Chronic idiopathic intestinal pseudo-obstruction is one of the disorders that is most refractory to medical and surgical treatment. Even when patients are given nutritional support, including total parenteral nutrition, obstructive symptoms seldom disappear. We report a case of chronic idiopathic intestinal pseudo-obstruction, due to myopathy, in which hyperbaric oxygenation therapy was strikingly effective. The presence of myopathy was histologically confirmed on the surgically resected jejunal specimen. Hyperbaric oxygenation resulted not only in relief of the patient's obstructive symptoms but also in a rapid decrease of abnormally accumulated intestinal gas. At last, he could resume oral intake without any critical adverse effects. These observations strongly suggest that hyperbaric oxygenation can be an effective therapy in the management of chronic idiopathic intestinal pseudo-obstruction.