Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland.

Cancer immunotherapy refers to an array of strategies intended to treat progressive tumors by augmenting a patient's anti-tumor immune response. As immunotherapy is eventually incorporated into oncology treatment paradigms, it is important to understand how these therapies interact with established cancer treatments such as chemotherapy or Radiotherapy (RT). To address this, we utilized a well-established, autochthonous murine model of prostate cancer to test whether RT could augment (or diminish) the CD4 T cell response to a tumor vaccine.

Transgenic mice that develop spontaneous prostate cancer (TRAMP) which also express a unique tumor associated antigen (Influenza hemagglutinin) under the control of a prostate-specific promoter were given local RT in combination with immunotherapy. The immunological outcome of this combinatorial strategy was assayed by monitoring the effector response of adoptively transferred, prostate-specific CD4 T cells.

Neither RT nor immunotherapy alone was capable of priming an anti-tumor immune response in animals with evolving tumors. The combination of immunotherapy with RT resulted in anti-tumor T cell activation-this effect was profoundly dependent on the relative timing of RT and immunotherapy. Anti-tumor immune responses occurred when immunotherapy was administered 3-5 weeks post-RT, but such responses were undetectable when immunotherapy was administered either earlier (peri-radiothrerapy) or later.

The therapeutic temporal window of immunotherapy post-RT suggests that highly aggressive, immuno-suppressive tumors might be most sensitive to immunotherapy in a fairly narrow time window; these results should help to guide future development of clinical combinatorial strategies.

Written by
Harris TJ, Hipkiss EL, Borzillary S, Wada S, Grosso JF, Yen HR, Getnet D, Bruno TC, Goldberg MV, Pardoll DM, Deweese TL, Drake CG.

Reference
Prostate. 2008 Jun 16. Epub ahead of print.
doi:10.1002/pros.20794

PubMed Abstract
PMID:18561247

UroToday.com Prostate Cancer Section

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