[Effect of Doxycycline on Intrinsic Apoptosis of Myeloma Cell Line H929 and Its Mechanism].

OBJECTIVE: To investigate the mechanism of the in vitro toxicity of doxycycline to myeloma cell line H929 and also the possible pathway involved its toxicity. METHODS: Myeloma cell line H929 was treated with DOX, MEK inhibitor U0126 or RAS agonist ML-098, either alone or in combination. Then, the expression of p-MEK, caspase-3, caspase-9 and c-Jun in H929 were used to detected by Western blot; the cells proliferation and apoptosis were detected by CCK-8 assay and flow cytometry, respectively. RESULTS: DOX significantly increased the levels of cleaved caspase-3 and caspase-9, and down-regulated the level of p-MEK in H929 (P<0.05). MEK antagonist U0126 significantly increased the levels of cleaved caspase-3 and caspase-9, and down-regulated the level of p-MEK (P<0.05). After Dox combined with ML-098 treatment of H929 cells, the apoptosis rate of H929 cells was lower than that of DOX alone treatment group(P<0.05). Compared with DOX alone treatment group, the expressions of p-MEK and p-ERK1/2 in DOX+ML-098 combined treatment group were increased, and the levels of cleaved caspase-3,9 in H929 cells were decreased (P<0.05). The levels of c-Jun mRNA and protein increased in H929 when treated by DOX alone (P<0.05). CONCLUSION: DOX can induce apoptosis of H929 via intrinsic apoptosis pathway, and MEK/ERK pathway and c-Jun possibly play a role in this process.

[The Effect of Doxycycline on the Expression of MMP-2 and MMP-9 in Multiple Myeloma].

OBJECTIVE: To investigate the expression of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in multiple myeloma (MM) patients, and analyze the effect of doxycycline (DOX) on the expression of MMP-2 and MMP-9 in MM cells. METHODS: The peripheral blood and bone marrow samples of MM patients were collected, and the patients were divided into three groups: newly diagnosed group, remission group and relapsed/refractory group, while the peripheral blood samples of 34 health people and the bone marrow samples of 17 IDA patients were selected as normal control and control group. The levels of MMP-2 and MMP-9 were detected by ELISA. The protein levels of MMP-2 and MMP-9 in H929 cells treated by different concentrations of DOX were analyzed by Western blot. After H929 cells was treated by Akt inhibitor MK-2206 2HCl in combination with DOX, Western blot was used to detect the levels of MMP-2 and MMP-9. RESULTS: The levels of MMP-2 and MMP-9 in newly diagnosed MM patients were higher than those in control (P<0.05), while for the patients in the remission group were decreased, but still higher than those in control. The levels of MMP-2 and MMP-9 were increased again for the patients in relapsed/refractory group, and showed no significant difference as compared with those in newly diagnosed group. The levels of MMP-2 and MMP-9 could be inhibited by 10 mg/L and 15 mg/L DOX treated by H929 cell. The protein levels of MMP-2 and MMP-9 showed no altered in H929 cells treated by 5 nmol/L MK-2206 2HCl alone. DOX exerted more profound inhibitory effect to MMP-2 and MMP-9 expression in H929 cells when Akt inhibitor MK-2206 2HCl was combined with DOX. CONCLUSION: The levels of MMP-2 and MMP-9 are increased in MM patients and related to the disease status of MM. DOX can inhibit the expression of MMP-2 and MMP-9 in MM cells, and antagonizing its activation of Akt signaling pathway can further enhance the inhibitory effect.

[Up-Regulation of PI3K/Akt Signaling Pathway in H929 Cell Line by Doxycycline Not Beneficial to Its Anti-Myeloma Effect].

OBJECTIVE: To investigate the effect and possible mechanism of up-regulation of p-Akt by doxycycline (DOX) on myeloma cell line H929. METHODS: Multiple myeloma cell line H929 was treated with DOX at different concentrations for different times, and cell proliferation rate was measured by CCK-8 assay. The protein expression level of p-Akt, PTEN, p-PDK1, p-mTOR, p-GSK-3ß, and p-BAD was analyzed by Western blot. The mRNA levels of mTOR, BCL-2, and NF-κB was analyzed by RT-PCR. PI3K inhibitor Wortmannin was used to antagonize the up-regulation of p-Akt, and the cell proliferation and p-Akt protein expression level were analyzed by CCK-8 assay and Western blot respectively. RESULTS: DOX could inhibit the proliferation of H929 cells and up-regulate the expression of p-Akt at the same time. The protein levels of both p-PDK1 and PTEN in H929 cells did not alter significantly during DOX treatment. The expressions of p-BAD and p-GSK-3ß were up-regulated in H929 cells after treated with DOX, but the expression of p-mTOR was not altered. The mRNA levels of mTOR, BCL-2, and NF-κB in H929 were all down-regulated in H929 cells during DOX treatment. The effect up-regulating p-Akt level by DOX was suppressed when DOX combined with PI3K inhibitor Wortmannin and Wortmannin could enhance the inhibitory effect of DOX in H929 cells. CONCLUSION: DOX can activate PI3K/Akt signaling pathway in H929 cells, and antagonizing this effect of DOX may enhance its cytotoxicity to myeloma cells.