Further evidence for increased macrophage migration inhibitory factor expression in prostate cancer.
BACKGROUND
Macrophage migration inhibitory factor (MIF) is a cytokine associated with prostate cancer, based on histologic evidence and circulating (serum) levels. Recent studies from another laboratory failed to document these results. This study's aims were to extend and confirm our previous data, as well as to define possible mechanisms for the discrepant results. Additional aims were to examine MIF expression, as well as the location of MIF's receptor, CD74, in human prostatic adenocarcinoma compared to matched benign prostate.


METHODS
MIF amounts were determined in random serum samples remaining following routine PSA screening by ELISA. Native, denaturing and reducing polyacrylamide gels and Western blot analyses determined the MIF form in serum. Prostate tissue arrays were processed for MIF in situ hybridization and immunohistochemistry for MIF and CD74. MIF released into culture medium from normal epithelial, LNCaP and PC-3 cells was detected by Western blot analysis.


RESULTS
Median serum MIF amounts were significantly elevated in prostate cancer patients (5.87 +/- 3.91 ng/ml; +/- interquartile range; n = 115) compared with patients with no documented diagnosis of prostate cancer (2.19 +/- 2.65 ng/ml; n = 158). ELISA diluent reagents that included bovine serum albumin (BSA) significantly reduced MIF serum detection (p < 0.01). MIF mRNA was localized to prostatic epithelium in all samples, but cancer showed statistically greater MIF expression. MIF and its receptor (CD74) were localized to prostatic epithelium. Increased secreted MIF was detected in culture medium from prostate cancer cell lines (LNCaP and PC-3).


CONCLUSIONS
Increased serum MIF was associated with prostate cancer. Diluent reagents that included BSA resulted in MIF serum immunoassay interference. In addition, significant amounts of complexed MIF (180 kDa under denaturing conditions by Western blot) found in the serum do not bind to the MIF capture antibody. Increased MIF mRNA expression was observed in prostatic adenocarcinoma compared to benign tissue from matched samples, supporting our earlier finding of increased MIF gene expression in prostate cancer.
Research and Development Service (151), Bay Pines Veterans' Administration Medical Center, Bay Pines, FL 33744, USA. Katherine.Siegler@med.va.gov
Katherine L
KL
Meyer-Siegler
Kenneth A
KA
Iczkowski
Pedro L
PL
Vera
D000230:Adenocarcinoma / Q000378:metabolism; D000944:Antigens, Differentiation, B-Lymphocyte / Q000096:biosynthesis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004797:Enzyme-Linked Immunosorbent Assay; D004848:Epithelium / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D008263:Macrophage Migration-Inhibitory Factors / Q000096:biosynthesis*; D008297:Male; D011467:Prostate / Q000378:metabolism; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism
D000944:Antigens, Differentiation, B-Lymphocyte; D000949:Histocompatibility Antigens Class II; D008263:Macrophage Migration-Inhibitory Factors; D012333:RNA, Messenger; C045084:invariant chain; D012710:Serum Albumin, Bovine; D017430:Prostate-Specific Antigen