Targeting the proliferative and chemoresistant compartment in chronic lymphocytic leukemia by inhibiting survivin protein

Abstract

Chronic lymphocytic leukemia (CLL) cells located in proliferation centers are constantly stimulated by accessory cells, which provide them with survival and proliferative signals and mediate chemotherapy resistance. Herein, we designed an experimental strategy with the aim of mimicking the microenvironment found in the proliferative centers to specifically target actively proliferating CLL cells. For this, we co-cultured CLL cells and bone marrow stromal cells with concomitant CD40 and Toll-like receptor 9 stimulation. This co-culture system induced proliferation, cell-cycle entry and marked resistance to treatment with fludarabine and bendamustine. Proliferating CLL cells clustered together showed a typical morphology of activated B cells and expressed survivin protein, a member of the inhibitor of apoptosis family that is mainly expressed by CLL cells in the proliferation centers. With the aim of specifically targeting actively proliferating and chemoresistant CLL cells, we investigated the effects of treatment with YM155, a small-molecule survivin inhibitor. YM155 treatment suppressed the co-culture-induced survivin expression and that was sufficient to inhibit proliferation and effectively induce apoptosis particularly in the proliferative subset of CLL cells. Interestingly, sensitivity to YM155 was independent from common prognostic markers, including 17p13.1 deletion. Altogether, these findings provide a rationale for clinical development of YM155 in CLL.

Janus and PI3-kinases mediate glucocorticoid resistance in activated chronic leukemia cells

“…To show the results were not simply model-dependent, the experiments were repeated in a stromal cell coculture model. CLL cells from four patients were cocultured with murine bone marrow stromal cells (OP9) expressing human CD40L [9, 15, 36, 37, 38]. Consistent with results from 2S-stimulated cells, cocultured CLL cells acquired resistance to DEX (30 μM) and were not killed by ruxolitinib, buparlisib or idelalisib alone (Figure 6).…”

High-content screening identifies kinase inhibitors that overcome venetoclax resistance in activated CLL cells

“…[43][44][45][46][47] Venetoclax (10 nM) induced cytotoxicity was significantly decreased in both coculture systems, with an average cell kill of 8% (n 5 6) for CD40L-cocultured cells and 30% (n 5 4) for OP9-cocultured cells compared with 60% kill in unstimulated (suspension) CLL cells (n 5 6) ( Figure 5A, bottom left panel and B; supplemental Figure 4A). In unstimulated cells, the high total kill (.95%) measured for the drug combination can be attributed to the single-agent effect of venetoclax (supplemental Figure 4A, bottom panel).…”

“…Coculture of primary CLL cells with stromal cells confirms resistance to venetoclax and effect of sunitinib As stromal cells have been found to guard CLL cells from drug-induced apoptosis, 3,42,43 CLL cells were cocultured with murine bone marrow stromal cells (OP9) or OP9 cells expressing human CD40L to combine stromal elements with T-cell effects. [43][44][45][46][47] Venetoclax (10 nM) induced cytotoxicity was significantly decreased in both coculture systems, with an average cell kill of 8% (n 5 6) for CD40L-cocultured cells and 30% (n 5 4) for OP9-cocultured cells compared with 60% kill in unstimulated (suspension) CLL cells (n 5 6) ( Figure 5A, bottom left panel and B; supplemental Figure 4A).…”

Inhibition of BCR signaling using the Syk inhibitor TAK-659 prevents stroma-mediated signaling in chronic lymphocytic leukemia cells

“…As we previously described, [15, 25] the co-culture of CLL cells with BMSC, CD40L and CpG ODN induces marked resistance to fludarabine and bendamustine in primary CLL cells. To test whether the addition of TAK-659 might overcome this co-culture-induced chemoresistance, we assessed the effects of the combination of TAK-659 with fludarabine.…”