Bone turnover markers are differentially affected by pre-analytical handling.

Given that bone turnover markers are often shipped to central laboratories, it is essential to be aware of factors that will affect stability. We have evaluated how sample type, time before separation of blood samples, and time between separation and analysis affect the stability of four bone turnover markers. INTRODUCTION: Bone turnover markers are often shipped to central laboratories for analysis, which require knowledge of the stability of the markers of interest in different sample materials. The aim of the current study was to evaluate how time before separation of blood samples and time between separation and analysis affect the stability of four bone turnover markers in serum and plasma samples. METHODS: Serum, EDTA, and Lithium heparin (LiHep) plasma samples from seven osteoporosis patients and three healthy controls were collected and stored at room temperature for up to 72 h before separation and analysis. After separation, samples were stored at room temperature for up to 72 h and re-analyzed. The bone turnover markers N-terminal pro-collagen type 1 extension pro-peptide (P1NP), bone-specific alkaline phosphatase (BAP), C-terminal teleopeptide cross links of collagen type 1 (CTX), and osteocalcin (OC) were analyzed using the automated iSYS IDS platform. RESULTS: P1NP and BAP were stable in both plasma and serum for 72 h before centrifugation. CTX levels were higher in EDTA plasma at all time points compared to LiHep plasma and serum. The use of EDTA plasma prolonged the stability of CTX as compared to LiHep plasma and serum. Osteocalcin showed high tendency to degrade in all sample types and concentrations were significantly lower after 24 h of storage. CONCLUSIONS: For the bone turnover markers P1NP and BAP, the use of both plasma and serum is recommended. Samples for CTX analysis should be taken as EDTA plasma. Samples for osteocalcin analysis can be taken in either type of plasma or serum, but should be analyzed within 3 h or preserved at - 18 °C.

Sequential versus combined treatment of human breast cancer cells with antiestrogens and the vitamin D analogue EB1089 and evaluation of predictive markers for vitamin D treatment.

Development of resistance to antihormonal therapy is a major problem in the treatment of breast cancer patients. Metastatic tumors, which progress after a period of response to treatment, often respond to second line endocrine treatment, but eventually develop estrogen independent growth. Vitamin D analogues are promising new drugs, using alternative mechanisms to inhibit growth of breast cancer cells. The sensitivity to antiestrogens and vitamin D analogues has been proposed to be inverse, indicating that the sensitivity to vitamin D analogues might increase after development of antiestrogen resistance and vice versa. In this study, the inverse sensitivity between antiestrogens and the vitamin D analogue EB1089 was examined in antiestrogen and vitamin D resistant breast cancer cell lines. The majority of the investigated antiestrogen resistant cell lines had increased sensitivity to treatment with the vitamin D analogue EB1089. In addition, growth of a vitamin D resistant cell line was more inhibited by the pure antiestrogen ICI 182,780 than the growth of the parental cells, indicating that the compounds may be used sequentially. An association between the expression level of the vitamin D receptor (VDR) and EB1089 sensitivity was observed, suggesting that VDR is a possible predictive marker for response to vitamin D treatment. Valuation of Bcl-2 gene expression may be useful in combination with VDR to predict the outcome of treatment with EB1089. Furthermore, we observed a synergistic growth inhibition and an abrogated development of resistance upon combined treatment with ICI 182,780 and EB1089. Therefore, antiestrogens and vitamin D analogues may also be used as combined treatment for breast cancer patients in the future.