Automated 22-kD growth hormone-specific assay without interference from Pegvisomant.

BACKGROUND: Large variability exists among different growth hormone (GH) assays owing to differences in calibration, antibody specificity, isoform recognition, and interference from GH binding protein (GHBP). The GH receptor antagonist Pegvisomant presents a new challenge because Pegvisomant interferes with many GH assays. A recent consensus conference established criteria for standardization and evaluation of GH assays. Following consensus recommendations, we developed a new GH assay on an automated analyzer (IDS-iSYS, Immunodiagnostic Systems). METHODS: A monoclonal antibody not cross-reacting with Pegvisomant was combined with a monoclonal antibody specific for 22-kD GH. Isoform specificity and interference from GHBP was tested and compared to that seen in 2 existing automated GH assays (Siemens Immulite, Diasorin Liaison). We also compared GH concentrations measured by the 3 assays for healthy volunteers and patients with acromegaly receiving different treatments. Using the iSYS assay, we also established nadir GH values during oral glucose load and analyzed changes in endogenous GH during Pegvisomant treatment. RESULTS: Analytical and functional sensitivities were 0.01 µg/L and 0.04 µg/L, with a dynamic range from 0.04 to 100 µg/L. Intraassay CVs were 2%-4%, whereas interassay CVs were 5%-7% at GH concentrations between 1.7 and 27.5 µg/L. The assay was specific for 22-kD GH and not affected by GHBP. The presence of Pegvisomant, which leads to a negative bias on the Immulite and dramatic overestimation of GH on the Liaison, had no impact on the iSYS GH assay. CONCLUSIONS: The new assay fulfils recent consensus recommendations and presents a useful new tool for reliable measurement of GH.

Overexpression of the homeobox gene HOXC8 in human prostate cancer correlates with loss of tumor differentiation.

BACKGROUND: Homeobox (HOX)-containing proteins have been identified as regulators controlling the coordinated expression of genes involved in development and differentiation. Recent data also suggest a possible involvement of HOX genes in malignant transformation and/or progression. We have previously shown that HOXC8 expression was selectively turned on in human cervix cancer cells compared with normal keratinocytes, suggesting that HOXC8 may be involved in the process leading to the transformation of cervix keratinocytes [Alami et al.: Biochem Biophys Res Commun 257:738-745, 1999]. METHODS: RT-PCR and in situ hybridization experiments were performed to investigate the expression and cell type localization of HOXC8 transcripts in human prostate cancer cell lines and tissues. In situ hybridization was performed with the use of an HOXC8 anti-sense digoxigenin-labeled probe to investigate HOXC8 mRNA expression in 27 prostate cancer tissue specimens. RESULTS: Out of the three human prostate cancer cell lines tested, DU-145 and PC3 but not LNCaP cells expressed detectable amount of HOXC8 transcripts. Results from in situ hybridization experiments demonstrated that HOXC8 gene was expressed mainly in malignant epithelial cells. Furthermore, the staining intensity in epithelial cells was significantly increased in high Gleason score carcinomas (scores 7-9, n = 12; labeling intensity 2 + to 3 +) compared with the one observed in low and intermediate Gleason score tumors (scores 3-6, n = 15; labeling intensity 0 and 1 +) (ANOVA test, P < 0.0001). CONCLUSIONS: Our data showing that HOXC8 overexpression is associated with the loss of tumor differentiation in human prostate cancer suggests that HOXC8 may play a role in the acquisition of the invasive and metastatic phenotype of this malignancy.