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

Abstract

To investigate the effect and possible mechanism of up-regulation of p-Akt by doxycycline (DOX) on myeloma cell line H929. 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. 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. DOX can activate PI3K/Akt signaling pathway in H929 cells, and antagonizing this effect of DOX may enhance its cytotoxicity to myeloma cells.