Combining milatuzumab with bortezomib, doxorubicin, or dexamethasone improves responses in multiple myeloma cell lines.
OBJECTIVE
The humanized anti-CD74 monoclonal antibody, milatuzumab, is in clinical evaluation for the therapy of multiple myeloma (MM). The ability of milatuzumab to increase the efficacy of bortezomib, doxorubicin, and dexamethasone was examined in three human CD74+ MM cell lines, CAG, KMS11, KMS12-PE, and one CD74-MM cell line, OPM-2.


METHODS
Activity of milatuzumab as a monotherapy and combined with the drugs was evaluated by studying in vitro cytotoxicity, signaling and apoptotic pathways, and in vivo therapeutic activity in severe combined immunodeficient (SCID) mouse models of MM.


RESULTS
Given as a monotherapy, cross-linked milatuzumab, but not milatuzumab alone, yielded significant antiproliferative effects in CD74+ cells. The combination of cross-linked milatuzumab with bortezomib, doxorubicin, or dexamethasone caused more growth inhibition than either cross-linked milatuzumab or drug alone, producing significant reductions in the IC(50) of the drugs when combined. Efficacy of combined treatments was accompanied by increased levels of apoptosis measured by increases of activated caspase-3 and hypodiploid DNA. Both milatuzumab and bortezomib affect the nuclear factor-kappaB pathway in CAG MM cells. In CAG- or KMS11-SCID xenograft models of disseminated MM, milatuzumab more than doubled median survival time, compared with up to a 33% increase in median survival with bortezomib but no significant benefit with doxorubicin. Moreover, combining milatuzumab and bortezomib increased survival significantly compared with either treatment alone.


CONCLUSIONS
The therapeutic efficacies of bortezomib, doxorubicin, and dexamethasone are enhanced in MM cell lines when given in combination with milatuzumab, suggesting testing these combinations clinically.
Garden State Cancer Center, Center for Molecular Medicine and Immunology, Belleville, New Jersey 07109, USA. rstein@gscancer.org
Rhona
R
Stein
Mitchell R
MR
Smith
Susan
S
Chen
Maria
M
Zalath
David M
DM
Goldenberg
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology / Q000378:metabolism; D000971:Antineoplastic Combined Chemotherapy Protocols; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D001897:Boronic Acids / Q000494:pharmacology / Q000627:therapeutic use*; D000069286:Bortezomib; D053148:Caspase 3 / Q000276:immunology / Q000378:metabolism; D045744:Cell Line, Tumor; D053938:DNA Fragmentation / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology / Q000627:therapeutic use*; D004317:Doxorubicin / Q000494:pharmacology / Q000627:therapeutic use*; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000378:metabolism; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000276:immunology / Q000401:mortality; D011719:Pyrazines / Q000494:pharmacology / Q000627:therapeutic use*
D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000944:Antigens, Differentiation, B-Lymphocyte; D001897:Boronic Acids; D000949:Histocompatibility Antigens Class II; D011719:Pyrazines; C045084:invariant chain; C540932:milatuzumab; D000069286:Bortezomib; D003907:Dexamethasone; D004317:Doxorubicin; D053148:Caspase 3