Effects of endoplasmic reticulum stress on autophagy and apoptosis of human leukemia cells via inhibition of the PI3K/AKT/mTOR signaling pathway.

The present study aimed to explore the regulatory effects of endoplasmic reticulum stress (ERS) on the phosphoinositide 3­kinase (PI3K)/AKT serine/threonine kinase 1 (AKT)/mammalian target of rapamycin (mTOR) signaling pathway, and its subsequent effects on autophagy and apoptosis of human leukemia cells. Human leukemia cells were cultured and treated with various concentrations of tunicamycin for 0, 24, 48, 72 and 90 h. Subsequently, human leukemia cells were assigned into the ER activation group, which was treated with 100 ng/ml tunicamycin, the ER activation + TO901317 (PI3K inhibitor) group, and the control group. An MTT assay was conducted to detect cell proliferation. In addition, a monodansylcadaverine (MDC) assay was used to detect the formation of autophagosomes and Annexin V­fluorescein isothiocyanate/propidium iodide double staining was used to examine cell apoptosis. Western blotting was performed to detect the expression levels of 78­kDa glucose­regulated protein (GRP78), phosphorylated (p)­protein kinase R­like endoplasmic reticulum kinase (PERK), p­α subunit of eukaryotic initiation factor 2 (eIF2α), microtubule­associated protein 1A/1B­light chain 3 (LC3), caspase­3, CCAAT­enhancer­binding protein homologous protein (CHOP), PI3K, AKT and mTOR. Treatment with 100 ng/ml tunicamycin for 72 h was considered the optimal condition for further experiments. Compared with in cells prior to treatment, human leukemia cells treated with tunicamycin exhibited increased expression of p­PERK, p­eIF2α and GRP78 after 72 h (P<0.05). In addition, the expression levels of mTOR, AKT and PI3K were decreased in the ER activation group compared with in the control and ER activation + TO901317 groups (P<0.05). Compared with in the control group, cell proliferation was inhibited and MDC fluorescence intensity was increased in the ER activation group (P<0.05). Furthermore, compared with in the control and ER activation + TO901317 groups, western blotting indicated that the expression levels of LC3­II were increased in the ER activation group (P<0.05). The apoptotic rate was also higher in the ER activation group compared with in the control group (P<0.05), and caspase­3 and CHOP expression was elevated in the ER activation group (P<0.05). These findings indicated that ERS may induce autophagy and apoptosis of human leukemia cells via inhibiting the PI3K/AKT/mTOR signaling pathway.

The effects of the long non-coding RNA MALAT-1 regulated autophagy-related signaling pathway on chemotherapy resistance in diffuse large B-cell lymphoma.

OBJECTIVE: Our study aimed to investigate the effects of the long non-coding RNA MALAT-1 (lncRNA MALAT-1) regulated autophagy-related signaling pathway on chemotherapy resistance in diffuse large B-cell lymphoma (DLBCL). METHODS: Human normal B lymphocytes (IM-9I) and DLBCL cell lines (Farage, Pfeiffer, Raji, Daud, Ly1, Ly3, Ly8 and Ly10) were chosen for our experiment. qRT-PCR was applied to detect the expression of lncRNA MALAT-1 in each DLBCL cell line. Farage and Daud cells were induced to be drug-resistant using 0.05µg/ml Adriamycin. LncRNA MALAT-1 interfering stable transfected cell lines were constructed and cells were transfected with lentivirus. The cells were divided into the blank, siNC, and siRNA-MALAT-1 groups. CCK-8 assay, flow cytometry, and Transwell assay were performed to detect cell survival rate, cycle, apoptosis, and invasion, respectively. The autophagosome formation in each group was observed under a transmission electron microscope. Western blotting was used to detect the expressions of the autophagy-related proteins and genes. The in vivo drug sensitivity of the tumor was observed using a subcutaneous tumor xenograft model in nude mice. RESULTS: The expression of lncRNA MALAT-1 in each DLBCL cell line was higher than in the IM-9 cells, with the Farage cells ranking highest (all P<0.05). When compared with the blank and the siNC groups, the siRNA-MALAT-1 group showed a decreased cell survival rate, an increased percentage of cells in G0/G1 phase, a decreased proportion of cells in S and G2/M phases, and a reduced number of migratory cell at each time point (all P<0.05). When compared with the blank and the siNC groups, the formation of autophagosomes, increased LC3-II/LC3-I expression, decreased p62 expression, and increased expression of the autophagy gene ATG5 were observed in the siRNA-MALAT-1 group at each time point (all P<0.05). Also, the siRNA-MALAT-1 group had a decreased tumor volume and weight in the subcutaneous tumor xenograft model in nude mice, and increased LC3-II/LC3-I expression but decreased p62 expression in tumor tissues when compared with the blank group and the siNC group (all P<0.05). CONCLUSION: Our study provides evidence that inhibiting lncRNA MALAT-1 can improve the chemotherapy sensitivity of DLBCL by enhancing autophagy-related proteins.