ABSTRACT
Nitric oxide [NO] could be pro or anti-apoptotic depending on cell type and caspase-3 activity. We aimed at studying the effect of antimetabolite chemotherapy on the enzymatic activity of nitric oxide synthase [NOS], caspase-3 and iron regulatory protein-1 [IRP-1] in 20 newly diagnosed acute myeloid leukemia [AML] patients and 10 hepatitis C virus infected hepatocellular carcinoma [HCC] patients since they have varied sensitivity to NO. AML patients received 7+3 regimen [combination of cytosine arabinoside [ara-C] and doxorubicin [DOX] and HCC patients received 5-fluorouracil [5-FU] 500 mg/m2 for 5 days every 3 weeks. All patients were followed up for 6 months to assess their response to therapy. The effect of adding S-nitroso-N-acetyl-penicillamine [SNAP], an NO donor, to chemotherapy on malignant cell survival of mononuclear cells [MNC] from AML patients [NO sensitive] and hepatocytes [NO resistant] from HCC patients was studied in vitro. Ten AML patients in remission and 10 patients having chronic hepatitis C [CHC] of matched age and sex served as controls for AML and HCC patients respectively. Results showed a significant decrease in plasma NOS activity in AML than HCC cases. Also, the MNC and hepatocytes were significantly different in cell aconitase activity, iron content and caspase-3 activity. Significantly higher NOS activity at diagnosis in chemosensitive AML patients compared to chemoresistant patients was also shown. Better chemotherapy response has been associated with significant decline in plasma NOS. MNC aconitase activity and iron content and rise of cellular caspase-3 activity compared to their levels at diagnosis. The HCC cells had significantly higher cellular iron content than chronic hepatitis-C infected cells. The former cells were resistant to 5-FU in vivo and in vitro. In vitro 6-h incubation of MNC with ara-C/ DOX/SNAP -combination was associated with lower percent cell surival, higher caspase-3 activity than cells incubated with ara-C or SNAP/ara-C. Conversely, HCC was insignificantly affected by incubation with 5-FU alone or with SNAP. The cytosolic aconitase activity was significantly inhibited in MNC and HCC following incubation with SNAP alone or with chemotherapy compared to corresponding cells in medium. A decline in intracellular iron was a feature that accompanied sensitivity to chemotherapy in AML cells in vivo and in vitro. This denotes that the interplay between NO level, caspase-3 activity and IRP-1 level largely determines antimetabolite chemosensitivity in different cells. NO donor may have a role in increasing chemosensitivity in AML while its value appears limited in HCC