The presence of multiple drug resistance (MDR1) and angiogenic phenotypes negatively affect patients' prognosis with cancer even when treated with drugs that are not transported by the MDR1 gene product. It is possible to suggest a link between the MDR1 and angiogenic phenotypes. Because prostaglandins (PGs) and nitric oxide (NO) have been proposed to be involved in angiogenesis in vivo, the production of PGs and NO and the behavior of inducible NO synthase (iNOS), cyclooxygenase 1 (COX-1), and inducible cyclooxygenase (COX-2) were studied in parental drug-sensitive (P5) liver cancer cell lines and in P5-derived MDR1 cells P1(0.5). Immunohistochemical evaluation, Northern and Western blot analysis of COX-2 and iNOS, and assessment of cell proliferation were performed in basal conditions and after the exposure to stimulants or to specific inhibitors of COX-2 and iNOS. The messenger RNA and protein levels of COX-2 and iNOS were in basal conditions higher in P1(0.5) cells than the parental P5 cells. The exposure to lipopolysaccharide (LPS) or epidermal growth factor (EGF) determined an increase of PG and NO production in both cell lines and this increase was strongly reduced by COX-2 inhibitors such as celecoxib (CLX) and nimesulide (NIME). The inhibition of NO production by COX-2 inhibitors suggests cross-talk between COX-2 and iNOS pathways. CLX and NIME also inhibited cell proliferation, but only in MDR1 cells. A specific inhibitor of iNOS, N 6 -(1-iminoethyl)-L-lysine, had only a mild effect on cell proliferation in both cell lines. In conclusion, these data support the hypothesis that the MDR1 and angiogenic phenotypes are linked to each other in human liver cancer cell lines. (HEPATOLOGY 2002;35:843-852.)

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The focus of this study was to use differential protein expression to investigate operative pathways in early stages of human colon cancer. Colorectal cancer represents an ideal model system to study the development and progression of human tumors, and the proteomic approach avoids overlooking posttranslational modifications not detected by microarray analyses and the limited correlation between transcript and protein levels. Colon cancer samples, confined to the intestinal wall, were analyzed by expression proteomics and compared with matched samples from normal colon tissue. Samples were processed by two-dimensional gel electrophoresis, and spots differentially expressed and consistent across all patients were identified by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry analyses and by Western blot analyses. After differentially expressed proteins and their metabolic pathways were analyzed, the following main conclusions were achieved for tumor tissue: 1) a shift from beta-oxidation, as the main source of energy, to anaerobic glycolysis was observed owed to the alteration of nuclear- versus mitochondrial-encoded proteins and other proteins related to fatty acid and carbohydrate metabolism; 2) lower capacity for Na(+) and K(+) cycling; and 3) operativity of the apoptosis pathway, especially the mitochondrial one. This study of the human colon cancer proteome represents a step toward a better understanding of the metabolomics of colon cancer at early stages confined to the intestinal wall.

In several neoplastic diseases, including hepatocellular carcinoma, the expression of P-glycoprotein and cyclooxygenase-2 (COX-2) are often increased and involved in drug resistance and poor prognosis. P-glycoprotein, in addition to drug resistance, blocks cytochrome c release, preventing apoptosis in tumor cells. Because COX-2 induces P-glycoprotein expression, we evaluated the effect of celecoxib, a specific inhibitor of COX-2 activity, on P-glycoprotein-mediated resistance to apoptosis in cell lines expressing multidrug resistant (MDR) phenotype. Experiments were done using MDR-positive and parental cell lines at basal conditions and after exposure to 10 or 50 Mmol/L celecoxib. We found that 10 Mmol/L celecoxib reduced P-glycoprotein, Bcl-x L , and Bcl-2 expression, and induced translocation of Bax from cytosol to mitochondria and cytochrome c release into cytosol in MDR-positive hepatocellular carcinoma cells. This causes the activation of caspase-3 and increases the number of cells going into apoptosis. No effect was shown on parental drug-sensitive or on MDR-positive hepatocellular carcinoma cells after transfection with MDR1 small interfering RNA. Interestingly, although inhibiting COX-2 activity, 50 Mmol/L celecoxib weakly increased the expression of COX-2 and P-glycoprotein and did not alter Bcl-x L and Bcl-2 expression. In conclusion, these results show that relatively low concentrations of celecoxib induce cell apoptosis in MDR cell lines. This effect is mediated by P-glycoprotein and suggests that the efficacy of celecoxib in the treatment of different types of cancer may depend on celecoxib concentration and P-glycoprotein expression. [Cancer Res 2007;67(10):4915-23]