Targeting the autophagy in bone marrow stromal cells overcomes resistance to vorinostat in chronic lymphocytic leukemia

Abstract

BackgroundThe bone marrow microenvironment constitutes a sanctuary for leukemia cells. Recent evidence indicates that environment-mediated drug resistance arises from a reciprocal influence between tumor cells and the surrounding stroma. The present study aimed to investigate the effect of chronic lymphocytic leukemia (CLL) cells on the metabolism of bone marrow stroma, to determine the role of this metabolic change in the stroma in vorinostat resistance of CLL cells, and thus to assess a novel strategy to target stroma and achieve the maximum therapeutic effect of vorinostat.MethodsTo evaluate this issue, we used freshly isolated CLL cells from peripheral blood samples of patients with CLL, and co-cultured them with bone marrow stromal cell lines to examine autophagy activity and metabolic changes in both CLL cells and stromal cells after vorinostat treatment.ResultsThe results demonstrated that CLL cells were under intrinsic oxidative stress which was further enhanced by vorinostat treatment, and released H2O2 outside the cells. The adjacent stromal cells took up H2O2 and drove autophagy, mitophagy and glycolysis, resulting in the local production of high-energy mitochondrial fuels, which were then taken up by CLL cells to be effectively utilized through mitochondrial oxidative phosphorylation to enable more ATP production. Notably, targeting autophagic stromal cells with autophagy inhibitor remarkably decreased stromal protection against vorinostat treatment in CLL cells.ConclusionThis study demonstrated that the stroma in the CLL microenvironment is abnormal and undergoes autophagy, and manipulation of autophagic stromal cells could serve as a novel promising strategy to circumvent stroma-mediated drug resistance in CLL cells.

Autophagy Inhibition Potentiates the Anticancer Effects of a Bendamustine Derivative NL-101 in Acute T Lymphocytic Leukemia

“…e autophagy-related protein expression also confirmed that the molecular mechanism is through inhibition of Akt/mTOR signaling. Interestingly, vorinostat or bendamustine alone failed to induce autophagy [29,46], thus suggesting that the induction of autophagy is a special trait of NL-101. Generally speaking, Akt needs phosphorylation of threonine phosphorylation site (thr308) or serine phosphorylation site (ser473) to regulate cell's function.…”

Oxidative resistance of leukemic stem cells and oxidative damage to hematopoietic stem cells under pro-oxidative therapy

“…Leukemic cells can also relieve oxidative injury by interacting with the leukemia niche. Ding et al 74 reported that H 2 O 2 generated by chronic lymphocytic leukemia (CLL) cells under vorinostat treatment was transferred to the surrounding stromal cells and drove autophagy, mitophagy, and glycolysis, resulting in the local production of high-energy mitochondrial fuels, which were then taken up by CLL cells to be effectively utilized through mitochondrial oxidative phosphorylation to enable more ATP production (Fig. 2).…”

<p>Anti-Oxidant and Anti-Endothelial Dysfunctional Properties of Nano-Selenium in vitro and in vivo of Hyperhomocysteinemic Rats</p>

“…Mitochondrial respiration in whole cells was measured by an oxygen consumption assay, as described. 27 Following incubating with 1.5 mM Hcy for 20 hours, HUVECs were resuspended in 1 mL of fresh culture medium pre-equilibrated with 21% oxygen at 37°C, followed by applying the cells to the sealed respiration chamber of a Clark-type oxygen measuring system (Oxytherm; Hansatech Instruments, Cambridge, UK) with constant stirring.…”

“…29 Following incubating with 1.5 mM Hcy for 20 hours, HUVECs were labeled with 50 nM NAO for 15 min and analyzed using flow cytometry, as previously described. 27 A cytochrome c release kit (EMD Millipore, San Diego, CA, USA) and caspase 3 activation assay kit (BD Biosciences, San Jose, CA, USA) were used to measure the loss of mitochondrial cytochrome c and the levels of activated caspase 3, according to the manufacturer's instructions. Rhodamine 123 (Invitrogen Life Technologies) was used to evaluate mitochondrial transmembrane potential.…”

“…Following incubating with 1.5 mM Hcy for 20 hours, HUVECs were labeled with 1 μM Rhodamine 123 for 60 min and analyzed using flow cytometry, as previously described. 27 Western Blot Analysis…”