Disruption of gap junctions attenuates acute myeloid leukemia chemoresistance induced by bone marrow mesenchymal stromal cells

Abstract

The bone marrow (BM) niche impacts the progression of acute myeloid leukemia (AML) by favoring the chemoresistance of AML cells. Intimate interactions between leukemic cells and BM mesenchymal stromal cells (BM-MSCs) play key roles in this process. Direct intercellular communications between hematopoietic cells and BM-MSCs involve connexins, components of gap junctions. We postulated that blocking gap junction assembly could modify cell-cell interactions in the leukemic niche and consequently the chemoresistance. The comparison of BM-MSCs from AML patients and healthy donors revealed a specific profile of connexins in BM-MSCs of the leukemic niche and the effects of carbenoxolone (CBX), a gap junction disruptor, were evaluated on AML cells. CBX presents an antileukemic effect without affecting normal BM-CD34 + progenitor cells. The proapoptotic effect of CBX on AML cells is in line with the extinction of energy metabolism. CBX acts synergistically with cytarabine (Ara-C) in vitro and in vivo. Coculture experiments of AML cells with BM-MSCs revealed that CBX neutralizes the protective effect of the niche against the Ara-C-induced apoptosis of leukemic cells. Altogether, these results suggest that CBX could be of therapeutic interest to reduce the chemoresistance favored by the leukemic niche, by targeting gap junctions, without affecting normal hematopoiesis.

Involvement of GPx-3 in the Reciprocal Control of Redox Metabolism in the Leukemic Niche

“…This modification in the redox status of MSCs may impact their functionality, since a defective support of normal hematopoiesis by MSCs stimulated by leukemic cells has been reported [ 57 ]. Our group recently highlighted a specific profile of connexins, which are components of gap junctions, in leukemic MSCs [ 58 ]. The reversed ROS kinetics, namely drop in leukemic cells and rise in MSCs, may be partly explained by a previously described mechanism of ROS transfer between hematopoietic cells and MSCs by Connexin-43 [ 59 ].…”

Remodeling of Bone Marrow Niches and Roles of Exosomes in Leukemia

“…By inhibiting gap junctions, CBX has been reported to synergize the effects of cytarabine to overcome chemoresistance. This indicates that it is possible to develop therapies to overcome the formation of chemoresistance and to eradicate leukemic cells [ 63 ].…”

Crosstalk between AML and stromal cells triggers acetate secretion through the metabolic rewiring of stromal cells

“…These results suggested that AML cells might establish gap junction interactions to transfer ROS to MS-5 cells when in co-culture. To test this hypothesis, we used the calcein-AM dye, which can only be transferred via gap junctions [10]. We labelled stromal cells with calcein-AM, cultured them with unlabelled AML cells and analysed the fluorescence of AML cells after three hours.…”

“…Functional gap junction presence was evaluated using the fluorescent dye Calcein-AM green (Invitrogen, C1430) adapting a previously established protocol [10]. MS-5 cells were stained with 500 nM Calcein-AM dye in complete cell culture medium for 1 hour at 37°C.…”

“…For instance, AML cells are known to interact and modulate niche components for their own support by secreting soluble factors [2–6], via exosomes [7–9] or by establishing direct interactions, mediated by gap junctions [10] or tunnelling nanotubes [11]. These interactions with components of the niche provide AML cells with survival cues, chemoresistance and increase AML relapse [2, 4, 7, 10, 12-14]. Furthermore, it has been reported that adipocytes in the niche secrete fatty acids, which are metabolised by AML cells through β-oxidation to obtain energy, protecting AML cells from apoptosis and ROS [15,16].…”