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Resistin induces multidrug resistance in myeloma by inhibiting cell death and upregulating ABC transporter expression - PubMed

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Resistin induces multidrug resistance in myeloma by inhibiting cell death and upregulating ABC transporter expression

Jianan Pang et al. Haematologica. 2017 Jul.

Abstract

Despite advances in therapy, multiple myeloma remains incurable, with a high frequency of relapse. This suggests the need to identify additional factors that contribute to drug resistance. Our previous studies revealed that bone marrow adipocytes promote resistance to chemotherapy in myeloma through adipocyte-secreted adipokines, but the mechanism underlying this effect and the specific adipokines involved are not well understood. We proposed to determine the role of resistin, an adipokine that is secreted by adipocytes, in chemotherapy resistance in myeloma. We found that resistin abrogated chemotherapy-induced apoptosis in established myeloma cell lines and primary myeloma samples. Resistin inhibited chemotherapy-induced caspase cleavage through the NF-κB and PI3K/Akt pathways. Resistin also increased the expression and drug efflux function of ATP-binding cassette (ABC) transporters in myeloma cells through decreasing the expression of both DNA methyltransferases DNMT1 and DNMT3a and the methylation levels of ABC gene promoters. In vivo studies further demonstrated the protective effect of resistin in chemotherapy-induced apoptosis. Our study thus reveals a new biological function of resistin in the pathogenesis of myeloma, with the implication that targeting resistin could be a potential strategy to prevent or overcome multidrug resistance in myeloma.

Copyright© 2017 Ferrata Storti Foundation.

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Figures

Figure 1.
Figure 1.

Resistin protects myeloma cells from chemotherapy-induced apoptosis. (A) Human myeloma cell lines ARP-1, MM.1S, and U266 were cultured in medium containing melphalan (25 μM) plus resistin (0, 10, 25, 50, 100, or 200 ng/mL) for 24 h; cells without melphalan treatment served as a control. Apoptosis in the cultured cells was determined by using an annexin V binding assay. The percentages of apoptotic cells in each of the three cell lines are shown. (B, C, D) ARP-1, MM.1S, and RPMI8226 cells were cultured in medium containing melphalan (Mel; 25 μM), bortezomib (BTZ; 5 nM), or carfilzomib (CFZ; 20 nM) with or without resistin (50 ng/mL) for 24 h. Cells cultured without the chemotherapy agents or resistin served as controls. Percentages of apoptotic cells are shown. (E) CD138+ plasma cells were isolated from bone marrow aspirates of five patients with multiple myeloma and cultured with melphalan (25 μM) without or with resistin (50 ng/mL) for 24 h. Percentages of apoptotic myeloma cells are shown. Results shown represent three to five independent experiments. *P<0.05; **P<0.01.

Figure 2.
Figure 2.

Resistin activates anti-apoptotic signaling pathways in myeloma cells. (A, B) ARP-1 and MM.1S myeloma cells were treated with melphalan (Mel; 25 μM) and/or resistin (50 ng/mL) for 24 h. Western blot analysis shows (A) the levels of cleaved (c) caspase (Cas)-9, Cas-3, and PARP, and (B) the expression of the mitochondria-related anti-apoptotic proteins Bcl-2 and Bcl-xL and the pro-apoptotic protein Bax in the cells. Cells cultured without treatment served as controls. (C) ARP-1 and MM.1S cells were cultured in medium with or without resistin (0, 50 ng/mL, or 100 ng/mL) for 12 h. Western blot analysis shows the levels of non-phosphorylated and phosphorylated (p) IκBα, Akt, and ERK1/2 in the cells treated with resistin. GAPDH served as a protein loading control. (D–F) ARP-1 or MM.1S cells were pretreated with (D) 1 μM NF-κB inhibitor Ro106, (E) 0.5 μM PI3K inhibitor LY294002, or (F) 1 μM MEK1/2 inhibitor U0126 for 1 h, followed by treatment with melphalan (25 μM) and/or resistin (50 ng/mL) for 24 h. The annexin V binding assay shows the percentages of apoptotic cells for each treatment condition. Cells cultured with none of the inhibitors served as controls. Results shown represent three independent experiments. *P<0.05.

Figure 3.
Figure 3.

Resistin increases the expression of ABC transporters in myeloma cells. ARP-1 and MM.1S myeloma cells were cultured with resistin (50 ng/mL) for 12 h. Some of the cultured cells were labeled with eFluxx-ID gold fluorescent dye and further analyzed by flow cytometry. Others were subjected to RNA or protein extraction for real-time PCR or western blot analysis. (A) Intracellular eFluxx-ID gold fluorescence intensity was quantified. PBS, phosphate-buffered saline solution (controls). (B) Real-time PCR shows relative mRNA expression of ABC transporter genes. (C) Western blot analysis shows expression of ABCG2 and ABCC5 proteins. Cells cultured without resistin served as controls. GAPDH served as a protein loading control. (D) Real-time PCR analysis shows relative expression levels of ABCC5 and ABCG2 mRNA in ARP-1 or MM.1S cells bearing non-targeted siRNA (siCtrl) or the pooled siRNA of ABCC5 (siC5) and ABCG2 (siG2). (E) The percentages of apoptotic cells in siCtrl- or both siC5- and siG2-expressing ARP-1 or MM.1S cells treated with or without resistin or melphalan (Mel) are shown. Results are representative of three independent experiments. *P<0.05; **P<0.01.

Figure 4.
Figure 4.

Resistin reduces the methylation of ABCG2 and ABCC5 gene promoters. ARP-1 and MM.1S myeloma cells were cultured with resistin (50 ng/mL) for 12 h. (A, B) Genomic DNA was extracted from cultured cells for methylation-specific PCR analysis. (A) Representative images of the methylated (M) and un-methylated (U) CpG sites and (B) quantitative data of M/U ratios in the promoters of ABCG2 or ABCC5 genes. PBS, phosphate-buffered saline solution (controls). (C, D) Total RNA and total proteins were extracted from cultured cells for real-time reverse transcriptase-PCR or western blot analysis. (C) Relative DNMT1, DNMT3a, and DNMT3b mRNA expression and (D) DNMT1 and DNMT3a protein expression. Cells cultured without resistin served as controls. GAPDH served as a protein loading control in western blot analysis. Results shown are representative of three independent experiments. *P<0.05; **P<0.01.

Figure 5.
Figure 5.

Resistin protects myeloma from chemotherapy in vivo. SCID mice were injected with ARP-1 myeloma cells (5×105 cells per mouse) directly into the femur (n=5 mice per group). Three weeks after ARP-1 cell injection, mice began intraperitoneal treatment with melphalan (Mel; 50 μg/mouse), resistin (20 μg/mouse), or both every 3 days for 3 weeks. After treatment, the mouse sera were subjected to enzyme-linked immusorbent assay to measure M-protein levels. After the mice had been euthanized, the cells flushed from each mouse’s femoral bone marrow cavity were labeled with an antibody against human CD138, and the CD138+ cells were sorted by flow cytometry. CD138+ cells were subjected to an annexin V binding assay to determine cell apoptosis. The mouse femora were analyzed with an in situ TUNEL assay. Mice that received neither melphalan nor resistin served as controls. (A) Relative levels of M-proteins. (B) Percentages of CD138+ cells. (C) Percentages of apoptotic CD138+ cells. (D) Representative images of TUNEL+ cells in bone marrow. (E) Quantitative analysis of TUNEL staining. Bar: 20 μm. Original magnification × 200. The results shown represent averages ± SD (n = 5 mice/group, 3 replicate studies). *P<0.05.

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