Immunogenic chemotherapy with cyclophosphamide and doxorubicin against established murine carcinoma.
Mitigation of regulatory T cell-mediated immunosuppression and elicitation of immunogenic tumor cell death are crucial events for optimal anti-tumor immune activity in vivo. This study was designed to investigate the potential synergistic activity of the combined use of cyclophosphamide (CP) and doxorubicin (DR), both of which are known to resolve these two issues. BALB/c mice were inoculated subcutaneously with CT-26 carcinoma cells in the bilateral flank and treated with an intraperitoneal injection of a low dose of CP followed by an intratumoral injection of DR into one side of the tumor. We found that, in addition to a significant suppression of growth on the DR-treated side of the tumor, combination therapy suppressed the growth of DR-untreated remote tumors in both tumor-specific and T cell-dependent manners. Mitomycin C showed no such synergistic anti-tumor activity with CP treatment. Combination therapy increased the frequency of interferon (IFN)-gamma-producing T lymphocytes specific to a CT-26-associated class I-binding tumor peptide in the tumor-draining lymph nodes. Real-time PCR analysis revealed that combination therapy led to an increase in IFN-gamma and tumor necrosis factor-alpha mRNA expression; however, levels of Foxp3 and transforming growth factor-beta within the remote tumor tissues were decreased. In addition, knock down of calreticulin expression in CT-26 cells using small interfering RNA attenuated anti-tumor vaccine effects induced by DR-treated CT-26 cells. These results provide an immunological rationale for the combined use of chemotherapeutic drugs, i.e., CP and DR, and further recommend their use with current cancer vaccines.
Tongu
Miki
M
Department of Immunology, Shimane University Faculty of Medicine, Izumo, Japan.
Harashima
Nanae
N
Yamada
Takaya
T
Harada
Takayuki
T
Harada
Mamoru
M
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D015153:Blotting, Western; D002277:Carcinoma / Q000188:drug therapy* / Q000276:immunology*; D003520:Cyclophosphamide / Q000008:administration & dosage; D004317:Doxorubicin / Q000008:administration & dosage; D004357:Drug Synergism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D051858:Forkhead Transcription Factors / Q000096:biosynthesis / Q000187:drug effects; D007371:Interferon-gamma / Q000096:biosynthesis / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000276:immunology*; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000187:drug effects
D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D004317:Doxorubicin; D007371:Interferon-gamma; D003520:Cyclophosphamide