Expression of stress response protein Grp78 is associated with the development of castration-resistant prostate cancer.
BACKGROUND
Induction of molecular chaperone Grp78 (78-kDa glucose-regulated protein) occurs in stress conditions that often characterize tumor microenvironments. We investigated the role of Grp78 in prostate cancer progression and the development of castration resistance, where cancer cells continue to survive despite the stress of an androgen-starved environment.


METHODS
Immunohistochemistry was done to examine Grp78 expression in 219 prostate cancers from patients with pathologic stage T3N0M0 disease [androgen ablation naive (untreated) and androgen ablation exposed (treated)] and castration-resistant prostate cancer. Classification of tumors was based on intensity of Grp78 cytoplasmic immunoreactivity and percentage of immunoreactive tumor cells. The associations of Grp78 expression with prostate cancer recurrence (clinical and/or serum prostate-specific antigen) and survival were examined in the untreated stage T3N0M0 group. Grp78 expression was also analyzed in the androgen-dependent LNCaP and castration-resistant C42B cell lines.


RESULTS
The percentage of tumor cells expressing Grp78 was strongly associated with castration-resistant status (P = 0.005). Increased Grp78 expression was consistently associated with greater risk of prostate cancer recurrence and worse overall survival in patients who had not undergone prior hormonal manipulation. Grp78 expression was also increased in the castration-resistant LNCaP-derived cell line C42B and in LNCaP cells grown in androgen-deprived conditions compared with LNCaP cells grown in androgen-rich media.


CONCLUSIONS
Our findings show that up-regulation of Grp78 is associated with the development of castration resistance, possibly in part by augmenting cell survival as previously suggested, and may serve as an important prognostic indicator of recurrence in a subset of patients with T3N0M0 disease.
Pootrakul
Llana
L
Department of Pathology, University of Southern California, Keck School of Medicine/USC Norris Comprehensive Cancer Center, Los Angeles, CA 90033, USA.
Datar
Ram H
RH
Shi
Shan-Rong
SR
Cai
Jie
J
Hawes
Debra
D
Groshen
Susan G
SG
Lee
Amy S
AS
Cote
Richard J
RJ
D015331:Cohort Studies; D000091342:Endoplasmic Reticulum Chaperone BiP; D015972:Gene Expression Regulation, Neoplastic; D006360:Heat-Shock Proteins / Q000235:genetics*; D006801:Humans; D008297:Male; D018832:Molecular Chaperones / Q000235:genetics*; D009367:Neoplasm Staging; D009919:Orchiectomy; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D013312:Stress, Physiological; D014407:Tumor Cells, Cultured
D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones