Introduction: T-cell based immunotherapy of tumors has gained much prominence in the last years. In this context treatments relying on the administration of recombinant bispecific antibodies (bsAbs) for retargeting effector T-lymphocytes towards cancer cells are of particular interest[1],[2]. However, several challenges with respect to pharmacokinetics, efficiency and safety need to be overcome. Our aim is to develop, test and apply a transplantable cell/biomaterial-based bsAb production platform (immunotherapeutic organoid) ensuring customized sustained release and effective and persistent levels of these T-cell stimulating therapeutic proteins over time with low risk of side effects.
Materials and Methods: Macroporous biohybrid hydrogel matrices (cryogels) were prepared by combining hydrogel network formation via chemical cross-linking of four-arm poly(ethylene glycol) (starPEG) and heparin with the cryogelation technology[3]. The capability of these starPEG-heparin cryogel materials to support the ingrowth, attachment, distribution and proliferation of gene-modified mesenchymal stem cells (MSCs) in vitro was tested by immunostaining/fluorescence microscopy and by using metabolic activity assays. Cell migration experiments were used to verify the attachment between the MSCs and the functionalized biomaterial under various experimental conditions. The production of therapeutic antibodies by the cell/cryogel machinery and their potential to kill tumor cells was quantified by enzyme-linked immunosorbent assays (ELISAs) at different time points and standard T-cell mediated cytotoxicity assays.
Results and Discussion: The unique sponge-like structure of the starPEG-heparin cryogel material with interconnected macropores provides a high surface-to-volume ratio and enabled ingrowth, proliferation and viability of gene-modified bsAb-releasing-MSCs and effective transport of nutrients, metabolites and therapeutic antibodies. Functionalization of the gels with peptide sequences allowed for integrin-mediated adhesion of the modified MSCs. The established cell/cryogel machinery was proved to be feasible for maintaining MSCs in a supporting microenvironment, and for producing recombinant bsAbs for prolonged time spans resulting in specific T-cell mediated tumor cell killing.
Conclusion: The proposed cell/cryogel system is a suitable candidate for developing transplantable immunotherapeutic organoids for future in vivo applications. It ensures the constant delivery of bsAbs to promote customized T-cell activation and efficient killing of tumor cells and paves the way to a safer and more effective tumor-specific strategy for T-cell mediated cancer treatment.
References:
[1] Arndt C, von Bonin M, Cartellieri M, Feldmann A, Koristka S, Michalk I et al. 2013 Redirection of T cells with a first fully humanized bispecific CD33–CD3 antibody efficiently eliminates AML blasts without harming hematopoietic stem cells. Leukemia 27 964–7.
[2] Aliperta R, Cartellieri M, Feldmann A, Arndt C, Koristka S, Michalk I, von Bonin M, Ehninger A, Bachmann J, Ehninger G, Bornhäuser M, Bachmann, M P 2015 Bispecific antibody releasing-mesenchymal stromal cell machinery for retargeting T cells towards acute myeloid leukemia blasts. Blood Cancer Journal 5 e348
[3] Welzel P B, Grimmer M, Renneberg C, Naujox L, Zschoche S, Freudenberg U and Werner C 2012 Macroporous starPEG-heparin cryogels. Biomacromolecules 13 2349–58