Specific cytotoxic effect of an auristatin nanoconjugate towards cxcr4⁺ diffuse large b-cell lymphoma cells

Background and Purpose: Around 40–50% of diffuse large-B cell lymphoma (DLBCL) patients suffer from refractory disease or relapse after R-CHOP first-line treatment. Many ongoing clinical trials for DLBCL patients involve microtubule targeting agents (MTAs), however, their anticancer activity is limited by severe side effects. Therefore, we chose to improve the therapeutic window of the MTA monomethyl auristatin E developing a nanoconjugate, T22-AUR, that selectively targets the CXCR4 receptor, which is over-expressed in many DLBCL cells (CXCR4⁺) and associated with poor prognosis. Methods: The T22-AUR specificity towards CXCR4 receptor was performed by flow cytometry in different DLBCL cell lines and running biodistribution assays in a subcutaneous mouse model bearing CXCR4⁺ DLBCL cells. Moreover, we determined T22-AUR cytotoxicity using cell viability assays, cell cycle analysis, DAPI staining and immunohistochemistry. Finally, the T22-AUR antineoplastic effect was evaluated in vivo in an extranodal CXCR4⁺ DLBCL mouse model whereas the toxicity analysis was assessed by histopathology in non-infiltrated mouse organs and by in vitro cytotoxic assays in human PBMCs. Results: We demonstrate that the T22-AUR nanoconjugate displays CXCR4-dependent targeting and internalization in CXCR4⁺ DLBCL cells in vitro as well as in a subcutaneous DLBCL mouse model. Moreover, it shows high cytotoxic effect in CXCR4⁺ DLBCL cells, including induction of G2/M mitotic arrest, DNA damage, mitotic catastrophe and apoptosis. Furthermore, the nanoconjugate shows a potent reduction in lymphoma mouse dissemination without histopathological alterations in non-DLBCL infiltrated organs. Importantly, T22-AUR also exhibits lack of toxicity in human PBMCs. Conclusion: T22-AUR exerts in vitro and in vivo anticancer effect on CXCR4⁺ DLBCL cells without off-target toxicity. Thus, T22-AUR promises to become an effective therapy for CXCR4⁺ DLBCL patients.