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CXCR4 and MYC dual targeting in DLBCL
loss of CXCR4 was associated with 30% and 24% decreases in the cytotoxic effect of CPI203 and the CPI203/IQS-01.01RS combination, respectively, confirm- ing that CXCR4 expression was required for the activity of the bromodomain inhibitor alone, as well as for its synergistic activity with IQS-01.01RS. In the case of SUDHL6, although the combination was still active in CXCR4-depleted cells, the loss of the receptor induced a 13% reduction in the synergistic activity of the two agents when compared with the parental CXCR4+ cells.
Thus, these results strongly support a crucial role for CXCR4 in the cooperation between CPI203 and IQS- 01.01RS in malignant B cells.
To assess the efficacy of the drug combination in vivo, NSG mice were subcutaneously injected with SUDHL6- GFP-Luc cells, and given IQS-01.01RS, CPI203, the com- bination of both agents, or the equivalent volume of vehi- cle, for 13 days. Tumor burden was evaluated weekly by bioluminescence signal recording and twice a week by external calipers. At the final time point, tumors were
AB
CD
Figure 4. IQS-01.01RS and CPI203 cooperate to reduce tumor growth in a subcutaneous mouse model of diffuse large B-cell lymphoma. NSG mice were subcuta- neously injected with SUDHL6-GFP+Luc+ cells and tumor-bearing mice were randomly assigned to one of the following treatment arms (4 mice per group): IQS- 01.01RS 2 mg/kg daily (per os), CPI203 1.5 mg/kg BID (intraperitoneally), both agents or equal volume of vehicle, for 2 weeks. (A) Tumor volume was evaluated twice a week using external calipers. (B) Tumor burden was evaluated at week 3 and week 4 by analysis of the bioluminescence signal. Left panel: color maps of two representative animals per group. Right panel: quantification of luciferase activity using Image J software. (C) Mean tumor weight in each treatment group at the final time point. (D) Immunohistochemical labeling of p-histone H3, activated caspase-3, MYC and p-AKT in consecutive tissue sections from four representative tumor specimens (magnification x200). act casp3: activated caspase 3; COMBO/combo: combination treatment with IQS-01.01RS and CPI203; SEM: standard error of mean; ns=not significant; *P<0.05.
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