Effect of liposomes containing sodium butyrate conjugated with anti-CD19 monoclonal antibody on in vitro and in vivo growth of malignant lymphoma.

ABSTRACT

A differentiation-inducer, sodium butyrate (SB), encapsulated in liposomes conjugated covalently to a monoclonal antibody directed to CD19 antigen, was successfully targeted to human lymphoma cell lines SKLY-18 and Ramos grown in vitro and in vivo in nude mice. Various control liposomes (lacking SB, lacking antibody, containing SB alone, or coupled to irrelevant antibody) were not effective targeters. Growth of tumor cells not expressing the relevant antigen was unaffected by the antibody-SB-liposome complex. Suppression of lymphoma growth in vivo was remarkable, and tumor regression was observed under certain conditions, although changes in morphology were not clearly observed. In view of the practical nonexistence of "tumor-specific" antigens, targeting of differentiation-inducers or growth modifiers, rather than cytotoxic drugs, to tumor cells, as exemplified in these experiments, may provide a useful approach for conversion of highly malignant to less malignant tumors, although the exact mechanism of the growth inhibitory effect on B-cell lymphoma of the anti-CD19 antibody-SB-liposome complex is unknown.