[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-3β, 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-3β 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.