Possible involvement of antitumor immunity in the eradication of colon 26 induced by low-voltage electrochemotherapy with bleomycin.
OBJECTIVE
The antitumor efficiency of electrochemotherapy using chemotherapeutic agents and high-voltage electric pulse has been reported. This study was done to define the precise nature of the involvement of antitumor immunity in the regression of tumor nodules in electrochemotherapy, and to evaluate the effectiveness of using low-voltage electroporation.


METHODS
Balb/c mice and Balb/c nu/nu nude mice were inoculated subcutaneously with Colon 26 cells or Meth A cells. Electrochemotherapy using bleomycin and low-voltage electroporation (CUY21) was performed as a treatment against tumor nodules.


RESULTS
Colon 26 tumors were eradicated in the mice given an intratumor (i.t.) injection of 500 microg bleomycin followed by treatment with electric fields ranging from 50 to 150 V/cm, with complete response rates ranging from 80% to 100%. The mice rejected inoculations of rechallenged Colon 26 cells, but not Meth A cells. In the Balb/c nu/nu nude mice, complete regression of the tumor was not seen after electrochemotherapy under the same therapeutic conditions that resulted in almost complete cure in the Balb/c mice.


CONCLUSIONS
Our results suggest that the generation of T-cell-dependent, tumor-specific protective immunity might be involved in the process of tumor nodule regression in low-voltage electrochemotherapy.
Miyazaki
Shinichi
S
Department of Academic Surgery (M9), Graduate School of Medicine, Chiba University School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
Gunji
Yoshio
Y
Matsubara
Hisahiro
H
Shimada
Hideaki
H
Uesato
Masaya
M
Suzuki
Takao
T
Kouzu
Teruo
T
Ochiai
Takenori
T
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage* / Q000494:pharmacology*; D001761:Bleomycin / Q000008:administration & dosage / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000276:immunology*; D004599:Electric Stimulation Therapy; D005260:Female; D007111:Immunity, Cellular; D051379:Mice; D008807:Mice, Inbred BALB C; D009374:Neoplasms, Experimental; D013601:T-Lymphocytes / Q000276:immunology*
D000964:Antimetabolites, Antineoplastic; D001761:Bleomycin