Low-dose combretastatin A4 phosphate enhances the immune response of tumor hosts to experimental colon carcinoma.
OBJECTIVE
Although there is a need to enhance the therapeutic efficiency in cancer by combining immunotherapeutic procedures with other therapy, combination with chemotherapy is complicated due to immunosuppressive effects of most chemotherapeutic drugs. The purpose of this investigation was to study whether combining tumor cell immunization with the vascular targeting drug combretastatin A4 phosphate (CA4P) would enhance tumor retardation and/or affect the antitumor immune response.


METHODS
Rats with intrahepatic colon carcinoma were immunized weekly with IL-18/IFNgamma-transfected tumor cells, starting day 9, and were treated with a low-dose CA4P (2 mg/kg, 5 days a week starting day 7). The effect of CA4P was studied on tumor growth and on immune reactivity in vitro.


RESULTS
Rats with preexisting tumor, immunized and treated with low-dose CA4P, had a significantly retarded tumor growth compared with rats receiving CA4P or immunization alone. Splenocytes from rats treated with this combination had a significantly enhanced antitumor immune response compared with splenocytes from control rats. Exposure of nonadherent splenocytes to CA4P in vitro did not enhance their proliferation. However, 3-hour pretreatment of adherent splenocytes with 0.3 microg/mL CA4P significantly enhanced proliferation and IFNgamma production of admixed nonadherent splenocytes, partly due to nitric oxide reduction. Combining the nitric oxide synthase inhibitor N-nitro-l-arginine methyl ester with CA4P and immunization further retarded tumor growth.


CONCLUSIONS
Concomitant treatment of rats with progressively growing tumor with immunization and low-dose CA4P significantly enhances the therapeutic effect as compared with either treatment alone and results in an enhanced antitumor immune reactivity.
Badn
Wiaam
W
Glioma Immunotherapy Group, The Rausing Laboratory, Division of Neurosurgery, Department of Clinical Sciences, Lund University, Lund, Sweden. wiaam.badn@med.lu.se
Kalliomäki
Suzanne
S
Widegren
Bengt
B
Sjögren
Hans Olov
HO
D000284:Administration, Oral; D000818:Animals; D002277:Carcinoma / Q000188:drug therapy* / Q000276:immunology*; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000276:immunology*; D004305:Dose-Response Relationship, Drug; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007274:Injections, Intraperitoneal; D007371:Interferon-gamma / Q000096:biosynthesis / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000276:immunology; D051381:Rats; D011914:Rats, Inbred BN; D011920:Rats, Inbred WF; D013267:Stilbenes / Q000008:administration & dosage* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014183:Transplantation, Heterologous; D023041:Xenograft Model Antitumor Assays
D013267:Stilbenes; D009569:Nitric Oxide; D007371:Interferon-gamma; C058728:fosbretabulin; D019331:NG-Nitroarginine Methyl Ester