---

Background: Leukemia is a malignant and progressive disease. Over-expression of inhibitors of apoptosis proteins (IAPs), such as survivin and its anti-apoptotic variants, including sur-ΔEx3, is the main cause of resistance to apoptotic effects of chemotherapy drugs. In the present study, the effects of CBX on apoptosis and expression level of survivin and sur-ΔEx3 and K562 cells (experimental model of chronic myeloid leukemia) were investigated. Materials and Methods: In this experimental study, human K562 cells were cultured and exposed to CBX. Trypan blue exclusion test was used to evaluate growth inhibitory and viability effects of the drug. Fluorescent microscopy (acridine orange/ ethidium bromide double staining) and DNA electrophoresis were applied to the study of apoptosis. The expression level of survivin and sur-ΔEx3 was studied by semiquantative RT- PCR. Results: The results showed that after the 48 h treatment of K562 cells with 150 µM CBX, significant growth inhibitory and apoptotic effects (up to 50%) were induced. In addition, after 2-4 h of treatment with CBX (150 µM), down-regulation of survivin and sur-∆Ex3 were observed. However, the expression level of survivin and sur-ΔEx3 increased to the level of control cells with longer treatment times (6-12 h). Conclusion: Noticing the apoptotic and down-regulatory effects of CBX on survivin and sur-∆Ex3 expression, this drug can be used as a potential candidate for further studies on CML treatment, especially for inhibition of drug resistance in leukemia cells.

---

Background: To date, several drugs have been proposed for the treatment of acute promyelocytic leukemia (APL) however, none of them has resulted in complete remission. Therefore, many efforts are in progress to find new drugs with the capability of inducing apoptosis. Recently, anti-carcinogenic effects have been reported for a drug named carbenoxolone (CBX) on several cell lines. In the present study, the effects of CBX on NB4 cell line, as an experimental model of APL, were examined. Materials and Methods: In this trial, NB4 cell line was cultured and treated with different concentrations of CBX (50-250µM) in various time intervals (12-48 hours). Trypan blue exclusion test was used to evaluate growth inhibitory and viability effects of the drug on NB4 cell line. Fluorescent microscopy (acridine orange/ethidium bromide double-staining) and agarose gel electrophoresis DNA were used to study apoptosis. Results: CBX induced growth inhibition of NB4 cells so that growth inhibition rates of NB4 cells, after the 48 hour of treatment with 50, 100, 150, 200, and 250 µM CBX were 32.65, 47.52, 60.73, 68.91, and 74.33%, respectively. Furthermore, the results of DNA fragmentation and fluorescent microscopy assays indicated that apoptosis is a major mode of cell death after treatment of NB4 cells with above concentrations of CBX. Conclusion: Noticing the growth inhibitory and apoptotic effects of CBX on human promyelocytic leukemia NB4 cells, it can be considered as a potential candidate for further studies on APL treatment.

---

Background: Nucleostemin plays a critical role in controlling proliferation and self-renewal of stem cells and cancer cells. Thus, inhibition of nucleostemin expression could be a potent therapeutic approach in cancer treatment. In the present study, the effects of nucleostemin gene silencing in K562 cell line were studied. Materials and Methods: In this experimental study, after transfecting NS-specific siRNA into K562 cells, changes in nucleostemin gene expression pattern were determined by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). Trypan blue exclusion test, MTT assay, and fluorescent microscopy were used to evaluate the growth inhibition and apoptosis of K562 cells, respectively. Flow-cytometery was utilized for evaluating the effects of nucleostemin gene silencing on cell cycle. Results: The results showed the high expression of nucleostemin gene in K562 cells. NS-siRNA transfection into K562 cells at 200 nM inhibited the nucleostemin mRNA level up to 55% after 48 hours when compared to corresponding control cells. Forty eight hours after transfection, the cell growth decreased up to 33.7%. In addition, the silencing of nucleostemin induced G1 cell cycle arrest. Furthermore, fluorescent microscopy assays indicated that apoptosis occurred 48 hours after silencing nucleostemin gene expression. Conclusion: Noticing the potent growth inhibitory and apoptotic effects of nucleostemin siRNA in human myeloid leukemia K562 cells, silencing this gene can be a potential target for inhibiting K562 cells as the stem cell model of chronic myeloid leukemia.