A novel synergistic combination of cyclophosphamide and gene transfer of interleukin-12 eradicates colorectal carcinoma in mice.
OBJECTIVE
Interleukin-12 (IL-12) is an immunostimulatory cytokine with potent antitumor effects in several animal models. However, serious toxicity has been associated with its systemic application in humans. Gene transfer has emerged as a tool to specifically express therapeutic genes into the tumor/peritumoral milieu, thus avoiding systemic toxicity. The aim of this study was to analyze whether subtherapeutic doses of an adenovirus encoding IL-12 (AdIL-12) might synergize with low immunopotentiating doses of cyclophosphamide in the treatment of colorectal carcinoma.


METHODS
The antitumor effect of combining a single low dose of cyclophosphamide with an intratumoral injection of AdIL-12 was evaluated in an in vivo murine colorectal carcinoma model. The immune responses achieved with different treatments were monitored, comparing the effect of combining both therapies with individual treatments.


RESULTS
The combined therapy induced a complete tumor regression in >50% of mice in a synergistic fashion, and it significantly prolonged their survival. This strategy was superior to each single treatment in reducing both peripheral and splenic CD4+CD25+Foxp3+ regulatory T cells, increasing the number of activated dendritic cells, and inducing IFN-gamma-secreting CD4-positive T lymphocytes. Importantly, the combined treatment generated a powerful tumor-specific CTL response. Consistently, a significant reduction in IL-10 levels was found. Our data suggest that the combination of nontoxic doses of cyclophosphamide with AdIL-12 allows the generation of good antitumoral responses, thus avoiding undesired side effects of both agents.


CONCLUSIONS
Our data strongly support the use of a combination of cyclophosphamide and AdIL-12 as a novel therapeutic strategy against colorectal carcinoma.
Malvicini
Mariana
M
Gene Therapy Laboratory, Liver Unit, School of Medicine, Austral University, Buenos Aires, Argentina.
Rizzo
Miguel
M
Alaniz
Laura
L
Piñero
Federico
F
García
Mariana
M
Atorrasagasti
Catalina
C
Aquino
Jorge B
JB
Rozados
Viviana
V
Scharovsky
O Graciela
OG
Matar
Pablo
P
Mazzolini
Guillermo
G
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D002277:Carcinoma / Q000188:drug therapy*; D015179:Colorectal Neoplasms / Q000188:drug therapy*; D003520:Cyclophosphamide / Q000494:pharmacology*; D051858:Forkhead Transcription Factors / Q000096:biosynthesis; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D007371:Interferon-gamma / Q000378:metabolism; D016753:Interleukin-10 / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism*; D053645:Interleukin-2 Receptor alpha Subunit / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C
D018906:Antineoplastic Agents, Alkylating; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D053645:Interleukin-2 Receptor alpha Subunit; D016753:Interleukin-10; D018664:Interleukin-12; D007371:Interferon-gamma; D003520:Cyclophosphamide