Interleukin-21 gene transfection into mouse bladder cancer cells results in tumor rejection through the cytotoxic T lymphocyte response.
OBJECTIVE
We developed the genetically modified mouse bladder carcinoma MBT2 (American Type Culture Collection, Manassas, Virginia), which secretes interleukin-21, to investigate the functional activities of interleukin-21 in tumor immunity.


METHODS
The IL-21 gene was cloned from activated T cells by reverse transcriptase-polymerase chain reaction, inserted into an expression vector and then introduced into MBT2 using Lipofectamine. Exogenous interleukin-21 was assayed in culture supernatants from transfectants using sandwich enzyme-linked immunoassay. Direct antitumor and tumor vaccine effects were investigated in syngeneic mice rendered immunodeficient by administration of the corresponding antibody.


RESULTS
MBT2 cells secreting interleukin-21 (MBT2/IL-21) were completely rejected when subcutaneously injected into syngeneic mice. MBT2/IL-21 proliferated only when CD8+ T cells were depleted, whereas MBT2/IL-21 proliferation was totally abrogated in mice depleted of CD4+ T cells, natural killer cells or interferon-gamma. Subcutaneous injection of MBT2/IL-21 treated with mitomycin C remarkably inhibited parental MBT2 tumor growth at the contralateral site. Cytotoxicity assays using splenocytes from mice that rejected MBT2/IL-21 and the immunohistochemical features of MBT2/IL-21 tumors confirmed that in situ production of interleukin-21 can elicit powerful antitumor activity through CD8+ T-cell activation.


CONCLUSIONS
Interleukin-21 production in situ elicits antitumor activity through the activation of CD8+ T cells in vivo.
Furukawa
Junya
J
Divisions of Urology and Dermatology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Japan. urofuru@med.kobe-u.ac.jp
Hara
Isao
I
Nagai
Hiroshi
H
Yao
Akihisa
A
Oniki
Shuntaro
S
Fujisawa
Masato
M
D000818:Animals; D007378:Interleukins / Q000235:genetics*; D051379:Mice; D013602:T-Lymphocytes, Cytotoxic / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000235:genetics* / Q000276:immunology*; D000098546:Interleukin-21
D007378:Interleukins; D000098546:Interleukin-21