Differences of bone alkaline phosphatase isoforms in metastatic bone disease and discrepant effects of clodronate on different skeletal sites indicated by the location of pain Per Magnusson, 1* Lasse Larsson, 1 Gunnar Englund, 2 Brita Larsson, 1 Peter Strang, 3 and Lena Selin-Sjo ¨ gren 4 We compared clodronate with placebo administration in 42 primarily or secondarily hormone-refractory prostate cancer patients with skeletal metastases and persisting pain. Serum total alkaline phosphatase (ALP), bone ALP isoforms, osteocalcin, cross-linked carboxy-terminal te- lopeptide of type I collagen, and prostate-specific anti- gen were analyzed before and after 1 month of treat- ment. Six ALP isoforms were quantified by HPLC: one bone/intestinal, two bone (B1, B2), and three liver ALP isoforms. The most apparent difference compared with healthy males was observed for the bone ALP isoform B2. Patients and healthy males had a B2 activity corre- sponding to 75% and 35% of the total ALP activity, respectively (P <0.0001). We propose that the different bone ALP isoforms reflect different stages of osteoblast differentiation during the extracellular matrix matura- tion phase of osteogenesis. All bone markers except osteocalcin increased after 1 month of clodronate ad- ministration. These increases were associated with pain only in the upper part of the body. We suggest that the uptake of clodronate by the skeleton was not uniform during our treatment period. Patients with breast, lung, and prostate cancer are partic- ularly prone to develop metastatic bone disease. Most of the prostate cancer patients, 60%, will develop skeletal metastases at some stage of the disease; consequently bone pain is a major problem in these patients (1, 2). The recent development of new biochemical markers of bone turnover has generated interest to use these markers for early detection of bone metastases and to assess efficacy and the response to antiresorptive treatment for patients with metastatic bone disease (3– 6). Two collagen markers of bone turnover, cross-linked carboxy-terminal telopep- tide of type I collagen (ICTP) 5 and carboxy-terminal propeptide of type I procollagen, give some information about the type and activity of bone metastases; moreover, ICTP has been reported to have a prognostic value in prostate cancer (7). Serum alkaline phosphatase (ALP, EC 3.1.3.1) and tartrate-resistant acid phosphatase (EC 3.1.3.2) are increased in prostate cancer patients with bone me- tastases, and the highest predictive value from a positive bone scintigraphy was obtained with bone ALP (0.88) (8). ALP is the most frequently used biochemical marker of osteoblastic bone formation. Four human gene loci are encoding for the ALP isoenzymes: “tissue nonspecific”, placental, germ cell, and small intestinal locus (9). ALP from the tissue nonspecific locus is expressed in tissues such as bone and liver and constitutes 95% of the total ALP activity in serum with a ratio of approximately 1:1 during healthy conditions in adults (10). Because bone 1 Bone and Mineral Metabolic Unit, Division of Clinical Chemistry, De- partment of Biomedicine and Surgery, Linko ¨ ping University Hospital, S-581 85 Linko ¨ ping, Sweden. 2 Department of Mathematical Statistics, Royal Institute of Technology, S-100 44 Stockholm, Sweden. 3 Division of Oncology, Department of Biomedicine and Surgery, Linko ¨p- ing University Hospital, S-581 85 Linko ¨ ping, Sweden. 4 Clinical Research, Medical Department, Astra La ¨kemedel AB, S-151 85 So ¨ derta ¨lje, Sweden. *Author for correspondence. Fax 46-13-223240; e-mail Per.Magnusson@ klk.liu.se. Received January 30, 1998; revision accepted June 2, 1998. 5 Nonstandard abbreviations: ICTP, cross-linked carboxy-terminal te- lopeptide of type I collagen; ALP, alkaline phosphatase; B/I, bone/intestinal alkaline phosphatase; B1, bone 1 alkaline phosphatase; B2, bone 2 alkaline phosphatase; B1/B2 ratio, bone 1 alkaline phosphatase/bone 2 alkaline phos- phatase ratio; L1, liver 1 alkaline phosphatase; L2, liver 2 alkaline phosphatase; L3, liver 3 alkaline phosphatase; PSA, prostate-specific antigen; U, upper body; and L, lower body. Clinical Chemistry 44:8 1621–1628 (1998) Enzymes and Protein Markers 1621 Downloaded from https://academic.oup.com/clinchem/article/44/8/1621/5642908 by guest on 30 June 2022