2-Amino-1,3,4-thiadiazole derivative (FABT) inhibits the extracellular signal-regulated kinase pathway and induces cell cycle arrest in human non-small lung carcinoma cells.

The anticancer potential of 2-amino-1,3,4-thiadiazole compounds has been documented by in vitro and in vivo studies. In our previous research, we described the synthesis as well as the antiproliferative and neuroprotective activities of 2-(4-fluorophenyloamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (FABT). The aim of the present study was to investigate the molecular mechanisms involved in FABT-induced growth inhibition in A549 lung carcinoma cells. Western blotting analysis revealed that FABT inhibited the activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway, and Real-time PCR analysis showed no changes in the expression of P44ERK1 and CREB1 genes. Furthermore, FABT induced cell cycle arrest in the GO/G1 phase and enhanced p27/Kip1 expression. Our results suggest that FABT acts by inhibiting ERK1/2 pathway and cell cycle progression through G1 into S phase in A549 cells. Further studies are needed to completely explain the molecular mechanisms of anticancer action of this 2-aminothiadiazole derivative.

Onconase, an anti-tumor ribonuclease suppresses intracellular oxidative stress.

Onconase (ONC), an antitumor ribonuclease from oocytes of a frog Rana pipiens, capable of inducing apoptosis in many cell lines is synergistic with several other anticancer drugs. Since cytotoxic effects of numerous drugs are modulated by reactive oxygen intermediates (ROI), we have studied effects of ONC on the intracellular level of oxidants in several normal cell types as well as tumor cell lines. It is demonstrated for the first time that ONC substantially decreases the content of ROI in all cell lines studied. This effect depends on the ribonucleolytic activity of the enzyme and is due to both, decreased rate of ROI generation and accelerated rate of their degradation. Onconase decreases the mitochondrial transmembrane potential and consequently, generation of ATP. Simultaneously the enzyme decreases the expression of an antiapoptotic protein Bcl-2, and upregulates the proapoptotic Bax protein. These finding are consistent with the enzyme propensity to induce apoptosis. The observed antioxidant activity of ONC may be an important element of its cytotoxicity towards cancer cells. The enzyme seems to exert its biological activities by interfering with the redox system of cellular regulation.

The degree of lymphocytic mitochondrial transmembrane potential and blood magnesium concentrations during coronary artery bypass grafting.

UNLABELLED: Magnesium (Mg) plays an important role in lymphocyte function. Low blood concentration of Mg may result in intralymphocyte imbalance and in turn may be associated with intensified apoptosis of peripheral blood lymphocytes. Due to its multistage character; extracorporeal circulation (ECC) may augment Mg disorders adding to the above mentioned pathology. The aim of this study was to assess the correlation between lymphocyte apoptosis and Mg concentration in the blood during the course of coronary artery bypass grafting (CABG) and in the early postoperative period. METHOD: Twenty male patients undergoing CABG with ECC under general anaesthesia were included in the study. For detection of apoptotic lymphocytes in the circulation, inner mitochondrial transmembrane potential (deltapsim) was measured with the use of chloromethyl-X-rosamine (CMXRos) and flow cytometry. Spectrophotometry was used for Mg blood concentration measurements. Peripheral blood samples were obtained in seven stages: 1) just before anaesthesia, 2) 2 hours after the beginning of surgery, 3) immediately after surgery, 4) 12 hours after the beginning of surgery, 5) 24 hours after the beginning of surgery, 6) 36 hours after the beginning of surgery, 7) 54 hours after the beginning of surgery. RESULTS: The statistically significant increases of lymphocyte apoptosis were noted in stages from 2 to 7. Blood Mg concentrations decreased in stages 2 and 3. There was negative correlation between Mg blood concentration in stages 2 and 3 and the intensity of lymphocyte apoptosis in the stage 5. CONCLUSIONS: 1) CABG with extracorporeal circulation was associated with a decrease of magnesium concentration in the blood and an increase of lymphocyte apoptosis intensity. 2) The decrease of magnesium blood concentration may increase the degree of lymphocyte apoptosis. 3) Lymphocyte apoptosis after extracorporeal circulation has a two-phase course.

Interactions of fluorochrome-labeled caspase inhibitors with apoptotic cells: a caution in data interpretation.

BACKGROUND: Fluorochrome-labeled inhibitors of caspases (FLICA, e.g., FAM-VAD-FMK, FITC-VAD-FMK) have been designed as affinity labels of the enzyme active center of caspases Their binding by apoptotic cells was interpreted as reflecting activation of caspases. We have recently observed, however, that their binding is more complex and may involve additional mechanisms. Our goal in this study was to clarify the ongoing utility of these probes. METHODS: Apoptosis of HL-60, Jurkat, MCF-7 and T-24 cells was induced by the DNA topoisomerase I inhibitor, topotecan, or by oxidative stress (H(2)O(2)). Lymphocytes were induced by their mitogenic activation. Using multiparameter laser scanning and flow cytometry analysis, the correlation between FLICA binding and the number of known apoptotic indicators was examined. These included: collapse of the mitochondrial transmembrane potential; activation of caspase-3 (detected immunocytochemically); binding of annexin V; chromatin condensation; the presence of DNA strand breaks; and loss of plasma membrane capability to exclude propidium iodide (PI). FLICA binding specificity was tested by pretreatment with z-VAD-FMK or z-DEVD-FMK. RESULTS: FLICA binding was subsequent to the collapse of mitochondrial transmembrane potential, nearly concurrent with caspase-3 activation, and preceded annexin V binding, chromatin condensation, DNA fragmentation and loss of plasma membrane integrity. The predominant portion of FAM-VAD-FMK, FITC-VAD-FMK or FAM-DEVD-FMK binding to apoptotic cells could not be inhibited by z-VAD-FMK or z-DEVD-FMK, respectively, when the unlabeled inhibitors were added post-induction of apoptosis. CONCLUSIONS: FLICA are specific and convenient to use markers of apoptotic cells and they detect very early events of apoptosis associated with caspases activation. Assays that combine their binding with either the loss of mitochondrial potential or with exclusion of PI as a probe of plasma membrane integrity, distinguish sequential stages of apoptosis and are particularly useful to differentiate between apoptosis and necrosis. Our results conform with the published data that unlabeled caspase inhibitors, when added after induction of apoptosis, cannot prevent activation of caspases detected by binding of biotinylated inhibitors or by cleavage of fluorogenic substrates. While FLICA binding by apoptotic cells most likely is a consequence of caspase activation, these binding events may also involve other or additional mechanisms than simply their specific attachment to the active enzyme centers of caspases.

Enhancement of activation-induced apoptosis of lymphocytes by the cytotoxic ribonuclease onconase (Ranpirnase).

Onconase (Onc) is an amphibian ribonuclease of the pancreatic RNase family that is cytostatic and cytotoxic to several tumor lines. It also shows anti-tumor activity in mouse tumor models and is currently in phase III clinical trials. In animal tests and clinical trials Onc shows lesser toxicity and fewer side effects compared to most chemotherapeutic drugs. Intriguingly, repeated infusions of this protein do not cause apparent immunological reactions in patients. The aim of the present study was to investigate sensitivity to Onc of human lymphocytes during their mitogenic stimulation in response to the polyvalent mitogen phytohemagglutinin (PHA), and in mixed allogeneic lymphocyte cultures. Unexpectedly, we observed that frequency of cells undergoing activation-induced apoptosis was markedly increased in all cultures containing Onc. Apoptosis was measured by flow cytometry using markers that detect activation of caspases, the in situ presence of DNA strand breaks, and loss of fragmented DNA ('sub-G1' cell subpopulation). The enhancement of frequency of activation-induced apoptosis (up to 244%) was observed at 4.2-83 nM Onc concentration, which is at least an order magnitude lower than its minimal concentration reported to affect proliferation or induce apoptosis of leukemic and solid tumor cell lines. The cell cycle progression of lymphocytes that responded to PHA mitogenically was not affected at 8.3 or 83 nM Onc concentration. Because activation-induced apoptosis is the key mechanism regulating several in vivo immunological functions including induction of tolerance, the observed effects of Onc may explain the apparent lack of immune reactions to this protein in treated patients. The propensity of Onc to potentiate the activation-induced apoptosis suggests that this drug may have clinical utility as immunomodulating agent, e.g., to suppress transplant rejection or treat autoimmune diseases.

Establishment and preliminary characterization of two cell lines derived from larynx carcinoma.

Two new cell lines, designated as RK-33 and RK-45, have been successfully established by an outgrowth technique from two different larynx tumours obtained from patients after laryngectomy. Both cell lineshave been maintained incultureforover 18 monthsandrecently have reached passage number 220 (RK-33) and 110 (RK-45). The cells display an epithelial morphology and multiply with a population doubling time of about 24 h (RK-33) and about 40 h (RK-45). The epithelial nature of the cells was also confirmed by expression of cytokeratins 8 and 18. Both lines were sensitive to antiproliferative effect of the tested cytostatic agents such as methotrexate. etoposide and thiotepa, with methotrexate being the most effective. We believe that both cell lines: RK-33 and RK-45 could be a suitable model for studying larynx cancer biology, however, further characterization of their properties is needed.

Flow cytometric analysis in diagnosis of thymoma metastases.

Thymomas are relatively rare tumours of the anterior mediastinum, constituting approximately 10-15% of all mediastinal tumours. In contrast to other neoplasms, they rarely present distant metastases. We describe a case of thymoma with long survival and skin metastases diagnosed by two-colour flow cytometry.