Figure 7

Cancer cell sensitization towards chemotherapy. (a) 334 sensitizes leukemia cells towards chemotherapy. Specific cell death induced in K562, Jurkat, CEM, and vincristine-resistant CEM cells (VCR-CEM) is shown. Cells were treated as indicated with 334 (10 µM), imatinib (IMA; K562) etoposide (ETO; Jurkat), and vincristine (VCR; CEM and VCR-CEM) alone or in combination for 48 h. Cell death was assessed by flow cytometry using Nicoletti assay. Bliss values (BVs) were calculated for combined cytostatic therapies and synergism is illustrated by response additivity (dashed lines). BVs > 1.05 or a combinational drug effect above the dashed lines indicate synergism (n = 3). (b) 334 re-sensitizes sorafenib-resistant HUH7 cells (HUH7-R) cells, which obtained broad chemotherapeutic cross-resistance. HUH7-R were generated from wild-type HUH7 cells (HUH7-WT) by drug exposure and maintained in 10 µM sorafenib. Proliferation rates within 72 h of 334 treatment were assessed by crystal violet staining and normalized to the untreated control (upper panel). Proliferation rates of cytostatic treatment were previously shown⁴⁰. The difference in growth rates obtained by HUH-R and HUH-WT cells was calculated and compared among 334, cisplatin and doxorubicin treatments (lower panel, see also Supplementary Fig. S7c online) (*P < 0.05, ***P < 0.001, One-way ANOVA, Tukey’s Multiple Comparison Test comparing concentrations, t-test comparing cell types, n = 3). (c) 334 overcomes broad chemotherapeutic cross-resistance of sorafenib-resistant HUH7-R cells by impairing the mitochondrial integrity. ATP-production (3 h), apoptosis (24 h) and cell viability (72 h) were assessed upon 334 treatment at the indicated time points (*P < 0.05, ***P < 0.001, One-way ANOVA, Tukey’s Multiple Comparison Test comparing concentrations, n = 3). (d) Low-dose 334 treatment sensitizes PDX leukemia cells towards chemotherapy. Specific cell death of PDX cells treated with 334 (10 µM), etoposide (700 nM)/imatinib (500 nM)/vincristine (5 nM) or a combination of both for 48 h is shown. The specific cell death was quantified by flow cytometry via FSC-SSC scatter plot analysis. BVs were calculated for combined cytostatic therapies and synergism is illustrated by response additivity (dashed lines). BVs > 1.05 or a combinational drug effect above the dashed lines indicate synergism. (*P < 0.05, One-way ANOVA, Tukey’s Multiple Comparison Test, n = 1, duplicates).