[Study on effect of tetramethylpyrazine on proliferation and apoptosis of leukemic U937 cells and its mechanism].

OBJECTIVE: To study the proliferation and apoptosis of tetramethylpyrazine (TMP) on leukemic U937 cells and its possible mechanism. METHOD: The inhibitory effect of TMP on the proliferation of U937 cells was detected by CCK-8 assay. The cell apoptosis and cycle distribution were examined by the flow cytometry. The mRNA expressions of bcl-2 and P27 were determined by the Real-time PCR. Western blot was carried out to detect bcl-2, caspase-3, cyclin E1, CDK2 and P27 expressions. RESULT: TMP inhibited the proliferation of U937 cells in a dose-and-time dependent manner, with IC50 value of 160 mg x L(-1) at 48 h. In addition, TMP could induce the apoptosis of U937 cells and block the cell cycle in G0/G1 phase. According to the results of Real-time PCR and Western blot, TMP could down-regulate the expression of apoptosis-related molecule bcl-2, cycle-related protein cyclin E1 and CDK2 and up-regulate caspase-3 and P27. CONCLUSION: TMP shows the effects in inhibiting the proliferation of leukemic U937 cells and inducing the apoptosis. Its mechanism may be related to the impacts on the cell cycle distribution, down-regulation of the bcl-2 expression, which finally activates caspase-3, starts the apoptosis path and causes the cell apoptosis.

Acute Lymphoblastic Leukemia Cells Inhibit the Differentiation of Bone Mesenchymal Stem Cells into Osteoblasts In Vitro by Activating Notch Signaling.

The disruption of normal hematopoiesis has been observed in leukemia, but the mechanism is unclear. Osteoblasts originate from bone mesenchymal stem cells (BMSCs) and can maintain normal hematopoiesis. To investigate how leukemic cells inhibit the osteogenic differentiation of BMSCs and the role of Notch signaling in this process, we cocultured BMSCs with acute lymphoblastic leukemia (ALL) cells in osteogenic induction medium. The expression levels of Notch1, Hes1, and the osteogenic markers Runx2, Osteopontin (OPN), and Osteocalcin (OCN) were assessed by real-time RT-PCR and western blotting on day 3. Alkaline phosphatase (ALP) activity was analyzed using an ALP kit, and mineralization deposits were detected by Alizarin red S staining on day 14. And then we treated BMSCs with Jagged1 and anti-Jagged1 neutralizing Ab. The expression of Notch1, Hes1, and the abovementioned osteogenic differentiation markers was measured. Inhibition of the expression of Runx2, OPN, and OCN and reduction of ALP activity and mineralization deposits were observed in BMSCs cocultured with ALL cells, while Notch signal inhibiting rescued these effects. All these results indicated that ALL cells could inhibit the osteogenic differentiation of BMSCs by activating Notch signaling, resulting in a decreased number of osteoblastic cells, which may impair normal hematopoiesis.

Tetramethylpyrazine inhibits the proliferation of acute lymphocytic leukemia cell lines via decrease in GSK-3ß.

Tetramethylpyrazine (TMP) has been proven to be an anticancer agent in many studies. However, its effectiveness in acute lymphoblastic leukemia (ALL) and its molecular mechanisms are still unclear. The present study aimed to evaluate the effect of TMP against Jurkat and SUP-B15 ALL cell lines and to investigate the possible detailed mechanism of action of TMP. A Cell Counting Kit-8 (CCK-8) assay was employed to examine the proliferation of Jurkat and SUP-B15 cells. Flow cytometric analysis was conducted to detect the cell cycle distribution and apoptotic rate. The expression of total glycogen synthase kinase-3ß (GSK-3ß), cox-2, survivin, bcl-2 and p27 RNA and protein levels was detected by quantitative real-time PCR and western blot assay, respectively. Additionally, western blot analysis was used to determine the whole-cell and nuclear protein levels of GSK-3ß downstream transcription factors, NF-κB (p65) and c-myc. TMP inhibited the proliferation of Jurkat and SUP-B15 cells in a dose- and time-dependent manner, with IC50 values of 120 and 200 µg/ml, respectively at 48 h. TMP induced the apoptosis of Jurkat and SUP-B15 cells and synergistically blocked cell cycle progression at the G0/G1 phase. Cells treated with TMP exhibited significantly attenuated GSK-3ß, NF-κB (p65) and c-myc expression, followed by downregulation of bcl-2, cox-2 and survivin and an upregulation of p27. The results showed that TMP induced apoptosis and caused cell cycle arrest in Jurkat and SUP-B15 cells through the downregulation of GSK-3ß, which may have further prevented the induced translocation of NF-κB and c-myc from the cytoplasm to the nucleus.