Radiation therapy induces circulating serum Hsp72 in patients with prostate cancer.
OBJECTIVE
Hsp72 found in the extracellular milieu has been shown to play an important role in immune regulation. The impact of common cancer therapies on extracellular release of Hsp72 however, has been to date undefined.


METHODS
Serum from 13 patients undergoing radiation therapy (XRT) for prostate cancer with or without hormonal therapy (ADT) was measured for levels of circulating serum Hsp72 and pro-inflammatory cytokines (IL-6 and TNF-alpha) using the classical sandwich ELISA technique and the relative expression of CD8(+) T lymphocytes and natural killer (NK) cells was measured using flow cytometry. Mouse orthotopic xenograft of human prostate cancer tumors (DU-145 and PC-3) were used to validate and further characterize the response noted in the clinical setting. The biological significance of tumor released Hsp72 was studied in human dendritic cells (DC) in vitro.


RESULTS
Circulating serum Hsp72 levels increased an average of 3.5-fold (median per patient 4.8-fold) with XRT but not with ADT (p=0.0002). Increases in IL-6 (3.3-fold), TNF-alpha (1.8-fold), CD8(+) CTL (2.1-fold) and NK cells (3.2-fold) also occurred. Using PC-3 and DU-145 human prostate cancer xenograft models in mice, we confirmed that XRT induces Hsp72 release primarily from implanted tumors. In vitro studies using supernatant recovered from irradiated human prostate cancer cells point to exosomes containing Hsp72 as a possible stimulator of pro-inflammatory cytokine production and costimulatory molecules expression in human DC.


CONCLUSIONS
The current study confirms for the first time in an actual clinical setting elevation of circulating serum Hsp72 with XRT. The accompanying studies in mice and in vitro identify the released exosomes containing Hsp72 as playing a pivotal role in stimulating pro-inflammatory immune responses. These findings, if validated, may lead to new treatment paradigms for common human malignancies.
Hurwitz
Mark D
MD
Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center and Harvard Medical School, Boston, MA, USA.
Kaur
Punit
P
Nagaraja
Ganachari M
GM
Bausero
Maria A
MA
Manola
Judith
J
Asea
Alexzander
A
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D045744:Cell Line, Tumor; D055354:Exosomes / Q000378:metabolism; D055551:HSP27 Heat-Shock Proteins / Q000097:blood; D050884:HSP72 Heat-Shock Proteins / Q000097:blood* / Q000502:physiology; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011471:Prostatic Neoplasms / Q000097:blood / Q000276:immunology / Q000532:radiotherapy*; D014409:Tumor Necrosis Factor-alpha / Q000097:blood; D023041:Xenograft Model Antitumor Assays
D055551:HSP27 Heat-Shock Proteins; D050884:HSP72 Heat-Shock Proteins; D014409:Tumor Necrosis Factor-alpha