| Cell apoptosis is one of the most important self-stabilization mechanisms for multi-cellular organisms. Apoptosis has diverse yet important roles under both physiological and pathological situation, which is governed by a plethora of relevant genes and gene products that either dicate cell death or prolong cell survival. Of particular importance, inhibition of apoptosis is shown to be a pivotal contributing factor in the pathogenesis of malignant tumors, especially for etiology of leukemia. So, methods intervening cell apoptosis may become new therapeutic strategy for leukemia. Anthracene-9-carboxylic acid (9-AC), an aromatic carboxylate, has been known as a cr channel blocker since 1 970s. Recently, patch-clamp study on the effects of 9-AC on the cAMP-dependent chloride current showed that 9-AC may change the activities of some channel protein by inhibiting a novel phosphatase which distinct from PP-i, PP-2 and PTP. The phosphataseeffects were found to be significantly dependent on the intracellular Mg2+. The activity of enzyme is high at physiological Mg2+ concentration suggests that which may play an important role in dephosphorylation and act on more substrates. However, other functions of 9-AC-sensitive phosphatase and its distribution have not been examined yet. In addition, the study on its properties has been confined to the whole-cell patch-clamp technique. c-myc is a transcriptional activator implicated in the control of cell proliferation, differentiation and transformation, but is also involved in the regulation of programmed cell death, apoptosis. Some studies revealed that the c-myc induced apoptosis is associated with a specific cleavage of poly (ADP ribose) polymerase (PARP), suggesting that a cysteine protease of the ICE/CED-3 family (especially for CPP32/Caspase-3) is involved. The present work was undertaken to study the effects of 9-AC on apoptosis and the expression of oncogene c-myc in HL-60 cells and possible intracellular factors involved in the process in order to give further evidence to the existence and physiological significance of 9-AC-sensitive phosphatase. First, HL-60 cells were treated with 9-AC to induce cell aoptosis for establishing an in vitro model of apoptosis. Three international accepted criteria for monitoring apoptosis were adopted, including transmission electron microscopy examination of ultrastructural changes, agrose gel DNA electrophoresis for detection of DNA ladder, and fluorescence-activated cell sorter (FACS) for detection of apoptosis with respect to cell cycle. Next, reverse transcriptase-polymerase chain reaction (RT-PCR) was also applied to assess the expression of c-myc in HL-60 cells. 9-AC could induce apoptosis of HL-60 cells, with its concentration most optimal at 5 x + O4mol/L. Forty-eight hours treatment of HL-60 cells with 9-AC at the concentration induced remarkable apoptotic phenomena as typified as: Ultrastructural changes like concentration of organells, disappearance of microvilli, margination of chromatin with nucleoli that are crescent-shaped, and condensation of chromatin. Enveloping of condensed or fragmented nuclei by membrane blebbing forms the so-called apoptotic bodies. Typical DNA ladder, symbolizing internucleosomai fragmentation of DNA, was observed by using agarose gel electrophoresis of isolated DNA from I-IL-60 cells. FACS analysis of I-IL-60 cells treated with 9-AC revealed markedly apoptotic peak-subdiploid peak, whereas cells of control group fa...
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