Therapeutic study (Systematic review of Level I studies with inconsistent results), Level II.

The c-Met is a receptor tyrosine kinase that is overexpressed in human myeloma cell lines and promotes the survival and drug resistance of myeloma cells. This study aimed to elucidate the mechanisms by which c-Met contributes to the chemoresistance in myeloma. Stable U266 cell line in which c-Met was effectively knockdown was employed and treated with bortezomib. Cytotoxicity was evaluated by MTT assay. Cell cycle profile and apoptosis were examined by cytometry analysis. The expression of cell cycle related proteins, and the activities of caspases and Akt/mTOR were detected by Western blot analysis. The c-Met knockdown in U266 cells decreased the average IC(50) of bortezomib, induced G0/G1 phase arrest, and increased caspase-mediated apoptosis in U266 cells exposed to bortezomib. In addition, c-Met knockdown decreased the level of cyclin D1 and increased the levels of p27 and cleaved caspase 3 and caspase 9. Moreover, the Akt/mTOR activity in U266 cells treated with bortezomib was downregulated upon c-Met knockdown and c-Met knockdown U266 cells recovered chemoresistance upon the overexpression of Akt and mTOR. Our data demonstrate that c-Met is a potential therapeutic target for multiple myeloma, and Akt/mTOR is a key signaling component through which c-Met protects multiple myeloma cells from chemotherapy-induced growth inhibition and apoptosis.

Umbilical cord blood has emerged as an alternative stem cell source to bone marrow or peripheral blood stem cells. Umbilical cord blood transplantation (UCBT) is also potentially curative for acute leukemia. However, the effect of unrelated donor bone marrow transplantation (UBMT) and UCBT on the outcome of patients with acute leukemia has not been systematically reviewed. In the present meta-analysis, we systematically searched Cochrane Library, MEDLINE, EMBASE, and CNKI up to May 2011. Two reviewers extracted data independently. Seven studies totaling 3389 patients have been assessed. Pooled results found that the incidence of engraftment failure and transplantation-related mortality were higher in UCBT than in UBMT, and relative risks (RRs) were 4.27 (95% confidence interval [CI], 2.94-6.21) and 1.27 (95% CI, 1.01-1.59), respectively. The rates of acute and chronic graft-versus-host disease (GVHD) in the UCBT group were significantly lower than that in the UBMT group, and RRs were 0.71 (95% CI, 0.65-0.79) and 0.69 (95% CI, 0.52-0.91), respectively. The relapse rate was similar between the UCBT and UBMT group. The leukemia-free survival (LFS) and overall survival (OS) were significantly lower in the UCBT group than in the UBMT group; RRs were 1.14 (95% CI, 1.07-1.22) and hazard ratios (HRs) were 1.31 (95% CI, 1.16-1.48), respectively. Subgroup analysis showed that in patients with acute lymphoblastic leukemia (ALL), the survival was similar between UCBT and UBMT.

Objective: The present study determined the role of DEP domain containing mTOR-interacting protein (DEPTOR) in the proliferation, apoptosis and chemosensitivity of RPMI-8226 multiple myeloma cells, using small hairpin RNA (shRNA) to knock down DEPTOR gene expression in vitro. Methods: DEPTOR mRNA and protein levels in RPMI-8226 cells treated with DEPTOR-specific shRNA were evaluated by reverse transcription-polymerase chain reaction and Western blotting. Expression of apoptosis-associated proteins (including cleaved caspase-3 and cleaved poly-ADP ribose polymerase [PARP]) and activation of the phosphatidylinositol 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homologue 1 (AKT) signalling pathway were detected by Western blotting. Results: Transfection of DEPTOR-specific shRNA successfully knocked down DEPTOR gene expression in transfected RPMI-8226 cells. These transfected cells, together with control RPMI-8226 cells, were treated with 20 mmol/l melphalan for 24 h. Knockdown of DEPTOR exacerbated melphalan-induced growth inhibition and apoptosis, increased levels of cleaved caspase-3 and cleaved PARP, and reduced levels of phosphor-AKT. Conclusion: Downregulation of DEPTOR inhibited proliferation and increased chemosensitivity to melphalan in human multiple myeloma RPMI-8226 cells via inhibiting the PI3K/AKT pathway.

DEP domain containing mammalian target of rapamycin (mTOR)-interacting protein (DEPTOR) is an mTOR binding protein that is overexpressed in RPMI-8226 human multiple myeloma cells, and plays an important role in maintaining cell survival. However, knowledge on the effects of DEPTOR knockdown on the biological functions of RPMI‑8226 human multiple myeloma cells, is limited. This study aimed to determine the role of DEPTOR in the proliferation, apoptosis and autophagy in these cells and to elucidate the mechanisms by which DEPTOR contributes to the chemosensitivity of myeloma cells. RNA interference was used to reduce the expression of DEPTOR. Cytotoxicity was evaluated by MTT assay. Apoptosis was examined by flow cytometry. DEPTOR mRNA and protein expression in RPMI‑8226 cells treated with DEPTOR-specific short hairpin RNA (shRNA) was evaluated by RT-PCR, quantitative PCR and western blot analysis. The expression of apoptosis‑associated proteins, autophagy‑associated proteins, and the activation of the phosphoinositide 3‑kinase (PI3K)/Akt signaling pathway were detected by western blot analysis. Autophagy was also measured by transmission electron microscopy and monodansylcadaverine (MDC). In this study, RPMI-8226 cells were transfected with the DEPTOR-specific shRNA, which resulted in the significant inhibition of the transcription and expression of DEPTOR. The downregulation of DEPTOR inhibited proliferation, enhanced the doxorubicin‑induced growth inhibitory effects on RPMI-8226 cells, and increased the expression of cleaved caspase‑3 and cleaved poly(ADP-ribose) polymerase (PARP). Moreover, the downregulation of DEPTOR suppressed autophagy and inhibited the activation of the PI3K/Akt signaling in RPMI‑8226 cells. In conclusion, our data demonstrated that the downregulation of DEPTOR induces apoptosis, increases chemosensitivity to doxorubicin, and suppresses autophagy and the activation of the PI3K/Akt signaling pathway in RPMI‑8226 human multiple myeloma cells.