Investigation of bone disease using isomerized and racemized fragments of type I collagen

Early diagnostic value of ECT whole-body bone imaging combined with PINP and β-CTX for bone metastasis of lung cancer

OBJECTIVE

This research was aimed at investigating the early diagnostic value of emission computed tomograph (ECT) whole-body bone imaging combined with PINP and β-CTX for bone metastasis of lung cancer.

METHODS

Case data of 86 lung cancer patients were categorized into lung cancer with bone metastasis (LCWBM, 46 cases) and lung cancer without bone metastasis (LCWOBM, 40 cases) groups according to the presence or absence of bone metastasis. Patients' general information were collected. ECT whole-body bone imaging was used to detect bone metastases and the grading of the extent of disease (EOD) in both groups, and electrochemiluminescence was utilized to detect the serum levels of PINP and β-CTX. Spearman correlation analysis was employed to evaluate the correlation between EOD grading and PINP and β-CTX levels. Logistic univariate and multivariate regression was implemented to analyze the risk factors of bone metastasis of lung cancer. Receiver operating characteristic (ROC) curve was applied to analyze the diagnostic efficacy of the single test of ECT whole-body bone imaging, PINP, or β-CTX and the combination of the three tests.

RESULTS

The differences in pathological type, clinical stage and EOD grading, the number of positive ECT cases, and the expression levels of PINP and β-CTX between the LCWBM and LCWOBM groups were statistically significant. In LCWBM patients with different EOD grading, the trends of the expression of PINP and β-CTX were grade 3 > grade 2 > grade 1 and grade 0. Further correlation analyses revealed that EOD grading showed a significant positive correlation with the PINP and β-CTX expression levels. Univariate logistic regression analysis demonstrated that adenocarcinoma, TNM stage IV, ECT positivity, and high expression of PINP and β-CTX were associated with bone metastasis of lung cancer, and multivariate logistic regression analysis indicated that ECT positivity, high expression of PINP and β-CTX were independent risk factors for bone metastasis of lung cancer. The area under the curve (AUC) of ECT, PINP, and β-CTX alone for the diagnosis of bone metastasis of lung cancer were 0.872, 0.888, and 0.874, respectively, and the AUC for the combined diagnosis of the three was 0.963, which was greater than that of any one of the individual indices, with a sensitivity of 86.96% and a specificity of 97.50% at a Youden index of 0.845.

CONCLUSION

ECT whole-body bone imaging combined with PINP and β-CTX has high diagnostic value for bone metastasis of lung cancer.

Effects of odanacatib on bone-turnover markers in osteoporotic postmenopausal women: a post hoc analysis of the LOFT study

This post hoc analysis and modeling study examined the mechanism of action of odanacatib using a statistical model to explain sCTx response in ODN-treated patients as a function of other bone-turnover biomarkers that, with other observed biomarker changes, showed that odanacatib persistently inhibited osteoclastic bone removal activity without preventing osteoclastogenesis.

INTRODUCTION

Odanacatib (ODN) is an oral selective cathepsin K (CatK) inhibitor, previously in development for osteoporosis treatment. A post hoc analysis examined ODN's mechanism of action on bone-turnover biomarkers.

METHODS

A subset of patients who completed 60 months' treatment in the Long-Term Odanacatib Fracture Trial (LOFT; NCT00529373) (N = 112 [57 ODN, 55 placebo]) were evaluated. Serum (s) and urine (u) samples were assayed at baseline and months 6-60 for 10 known bone-remodeling biomarkers: sCTx, uαα- and uββCTx/Cr, uNTx/Cr, sNTx, uDPD/Cr, sICTP, sTRAP5b, sPINP, and sBSAP. Because the CrossLaps® CTx assay identifies the CTx peptide as well as larger molecular weight CTx-containing peptides, including ICTP, a best-fit model was developed to explain the transient sCTx reduction in ODN-treated patients.

RESULTS

ODN persistently reduced the bone-resorption markers sNTx, uNTx/Cr, uαα- and uββCTx/Cr, and uDPD/Cr, and gradually increased the target-engagement marker sICTP and osteoclast number (sTRAP5b), versus placebo from baseline to month 60. sCTx was transiently reduced with ODN within 12 months, returning to baseline by month 48. Modeling suggested that sCTx changes in the ODN group were primarily due to increased accumulation of larger CTx species, including sICTP. The bone-formation markers sPINP and sBSAP showed partial reductions, versus placebo, in the first 6 months but approached baseline by months 48-60.

CONCLUSION

Observed changes in bone-turnover biomarkers support the persistent efficacy of ODN in direct inhibition of osteoclastic bone-resorption activity, without inhibition of osteoclastogenesis. Long-term evaluation also underscores the unique mechanism of ODN on osteoclastic collagen processing and subsequently osteoblastic bone formation.

TRIAL REGISTRATION

NCT00529373.

Mesenchymal Stem Cell Transplantation for the Treatment of Age-Related Musculoskeletal Frailty

Projected life expectancy continues to grow worldwide owing to the advancement of new treatments and technologies leading to rapid growth of geriatric population. Thus, age-associated diseases especially in the musculoskeletal system are becoming more common. Loss of bone (osteoporosis) and muscle (sarcopenia) mass are conditions whose prevalence is increasing because of the change in population distribution in the world towards an older mean age. The deterioration in the bone and muscle functions can cause severe disability and seriously affects the patients’ quality of life. Currently, there is no treatment to prevent and reverse age-related musculoskeletal frailty. Existing interventions are mainly to slow down and control the signs and symptoms. Mesenchymal stem cell (MSC) transplantation is a promising approach to attenuate age-related musculoskeletal frailty. This review compiles the present knowledge of the causes and changes of the musculoskeletal frailty and the potential of MSC transplantation as a regenerative therapy for age-related musculoskeletal frailty.

Collagens and Cancer associated fibroblasts in the reactive stroma and its relation to Cancer biology

The extracellular matrix (ECM) plays an important role in cancer progression. It can be divided into the basement membrane (BM) that supports epithelial/endothelial cell behavior and the interstitial matrix (IM) that supports the underlying stromal compartment. The major components of the ECM are the collagens. While breaching of the BM and turnover of e.g. type IV collagen, is a well described part of tumorigenesis, less is known regarding the impact on tumorigenesis from the collagens residing in the stroma. Here we give an introduction and overview to the link between tumorigenesis and stromal collagens, with focus on the fibrillar collagens type I, II, III, V, XI, XXIV and XXVII as well as type VI collagen. Moreover, we discuss the impact of the cells responsible for this altered stromal collagen remodeling, the cancer associated fibroblasts (CAFs), and how these cells are key players in orchestrating the tumor microenvironment composition and tissue microarchitecture, hence also driving tumorigenesis and affecting response to treatment. Lastly, we discuss how specific collagen-derived biomarkers reflecting the turnover of stromal collagens and CAF activity may be used as tools to non-invasively interrogate stromal reactivity in the tumor microenvironment and predict response to treatment.

Second-harmonic generation imaging of collagen in ancient bone

Second-harmonic generation imaging (SHG) captures triple helical collagen molecules near tissue surfaces. Biomedical research routinely utilizes various imaging software packages to quantify SHG signals for collagen content and distribution estimates in modern tissue samples including bone. For the first time using SHG, samples of modern, medieval, and ice age bones were imaged to test the applicability of SHG to ancient bone from a variety of ages, settings, and taxa. Four independent techniques including Raman spectroscopy, FTIR spectroscopy, radiocarbon dating protocols, and mass spectrometry-based protein sequencing, confirm the presence of protein, consistent with the hypothesis that SHG imaging detects ancient bone collagen. These results suggest that future studies have the potential to use SHG imaging to provide new insights into the composition of ancient bone, to characterize ancient bone disorders, to investigate collagen preservation within and between various taxa, and to monitor collagen decay regimes in different depositional environments.

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Second-Harmonic Generation (SHG) confocal laser scanning microscopy is used to investigate collagen remnants in ancient bone.

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Four independent techniques confirm the presence of collagen remnants in ancient bone samples with SHG-detected collagen.

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SHG imaging can visualise collagen remnants in ancient bone of various taxa, ages, and settings.

Musculoskeletal ageing and primary prevention

Loss of musculoskeletal mass and function is a natural ageing trait, reinforced by an unhealthy life style. Loss of bone (osteoporosis) and muscle (sarcopaenia) are conditions whose prevalence are increasing because of the change in population distribution in the western world towards an older mean age. Improvements in lifestyle factors, such as diet, smoking and exercise, are the most powerful tools to combat this decline efficiently; however, public health interventions aimed at tackling these problems have shown abysmal success at the population level, mostly due to failure in compliance. With these issues in mind, we believe that the primary prevention modality in coming decades will be pharmacological. We review the basic biology of musculoskeletal ageing and what measures can be taken to prevent ageing-associated loss of musculoskeletal mass and function, with particular emphasis on pharmacological means.

Serum and urine bone resorption markers and pharmacokinetics of the cathepsin K inhibitor ONO-5334 after ascending single doses in post menopausal women

AIMS

To investigate the safety, pharmacokinetics and pharmacodynamics of the new cathepsin K inhibitor, ONO-5334.

METHODS

A double-blind, placebo-controlled, randomized study was carried out in 52 healthy post menopausal females. Single ascending doses of ONO-5334 (3-600 mg) were evaluated in six cohorts. The effect of food was studied at ONO-5334 100 mg.

RESULTS

Across the doses tested, mean ONO-5334 C(max) occurred 0.5-1.0 h after dosing and the the t(1/2) ranged from 9.1 to 22 h. Linear increases in C(max) and AUC(0,∞) were observed in the 3-300 mg and 3-600 mg dose range, respectively. After food, the geometric mean ratio (95% CI) C(max) and AUC(0,∞) for ONO-5334 were 0.78 (0.31, 1.94) and 0.95 (0.67, 1.35)-fold greater than fasted, respectively. ONO-5334 significantly reduced serum bone resorption markers within 4 h vs. placebo. Statistical significance was achieved for ONO-5334 doses ≥30 mg for C-terminal telopeptide of type 1 collagen (CTX) and ≥300 mg for N-terminal telopeptide of type 1 collagen (NTX). Statistical significance was still evident at 24 h for ONO-5334 100 mg with serum CTX and 600 mg with serum NTX. The maximum suppression in serum CTX occurred at 4 h post dose with difference compared with placebo of -32%, -59%, -60% and -66% for 30, 100, 300 and 600 mg ONO-5334, respectively. Second morning urine void 24 h post dose showed statistically significant suppression of urinary CTX and NTX at 100 mg and above vs. placebo. ONO-5334 600 mg showed statistically significant suppression up to 72 h for serum CTX, urinary CTX and urinary NTX and 48 h for serum NTX vs. placebo. Adverse events were transient with no evidence of dose relationship.

CONCLUSIONS

ONO-5334 displayed linear plasma pharmacokinetics over the (predicted therapeutic) dose range, 3-300 mg, with clear suppression of urinary bone resorption markers at doses ≥100 mg for serum markers at 24 h. ONO-5334 was well tolerated up to 600 mg day(-1) when administered to healthy post menopausal women.

Effects of Src kinase inhibition by saracatinib (AZD0530) on bone turnover in advanced malignancy in a Phase I study

Saracatinib (AZD0530) is an orally active once-daily Src kinase inhibitor which modulates key signaling pathways in cancer cells. In a Phase I study in patients with advanced solid malignancies resistant to standard treatment we assessed the effect of saracatinib on bone turnover. Fifty-one patients were randomized into three parallel groups to receive saracatinib 50, 125 or 175 mg/day. After a single dose followed by a 7-day washout, patients received once-daily doses for 21 days. Bone turnover markers were measured in serum and urine samples collected before dosing on days 1, 2, 3, 17 and 28. Samples were available at baseline and more than one other time point for 44 patients. Bone resorption markers were significantly decreased by saracatinib. Serum cross-linked C-terminal telopeptide of type I collagen (sCTX) changed in the 50, 125 and 175 mg/day groups by -36% (95% CI -58, -4), -64% (95% CI -75, -48) and -75% (95% CI -83, -61), respectively, at day 28. Urinary cross-linked N-terminal telopeptide of type I collagen/creatinine ratio (uNTX/Cr) changed in the 50, 125 and 175 mg/day groups by; -13% (95% CI -33, 13), -48% (95% CI -59, -34) and -50% (95% CI -62, -35), respectively, at day 28. The significant decreases in bone resorption markers indicate that suppression of Src kinase inhibits osteoclast activity in patients with advanced cancer. This result suggests that saracatinib may have therapeutic benefit in metastatic bone disease.

Value of C-telopeptide-cross-linked Type I collagen, osteocalcin, bone-specific alkaline phosphatase and procollagen Type I N-terminal propeptide in the diagnosis and prognosis of bone metastasis in patients with malignant tumors

Background

Studies show markers of bone turnover can help the clinician in the diagnosis and follow-up of bone metastases. The present study aimed to investigate the value of biochemical markers of bone turnover in the diagnosis and prognosis of bone metastases of malignant tumors.

Material/Methods

The serum levels of C-Telopeptide-Cross-Linked Type I Collagen (CTx), Procollagen Type I N-Terminal Propeptide (PINP), Bone-Specific Alkaline Phosphatase (B-ALP) and Osteocalcin (OST) in patients with bone metastases and control subjects were measured using radioimmunoassay and immunochemiluminescent assay.

Results

The levels of CTx, PINP, B-ALP and OST in the metastasis group were significantly higher than those in both control groups and correlated with the number of bone metastatic sites. The levels of these markers were higher in prostate cancer patients with bone metastasis. The CTX of >426 ng/ml had the highest sensitivity and NPV, and PINP of >51.21 ng/ml had the highest specificity and PPV in healthy subjects. In addition, CTX of >547 ng/ml had the highest sensitivity and OST of >20.34 ng/ml the highest specificity in the non-metastasis group. Furthermore, both B-ALP of >15.55 ng/ml had relatively high negative predictive value and positive predictive value.

Conclusions

Biochemical markers of bone turnover, including CTx, PINP, B-ALP and OST, play important roles in the diagnosis and prognosis of metastatic bone cancer. CTX had a high sensitivity, and PINP had a high specificity in predicting bone metastasis. B-ALP is an ideal biochemical marker of bone turnover for metastatic bone cancer.

The amino- and carboxyterminal cross-linked telopeptides of collagen type I, NTX-I and CTX-I: a comparative review

Bone diseases such as osteoporosis or bone metastases are a continuously growing problem in the ageing populations across the world. In recent years, great efforts have been made to develop specific and sensitive biochemical markers of bone turnover that could help in the assessment and monitoring of bone turnover. The amino- and carboxyterminal cross-linked telopeptides of type I collagen (NTX-I and CTX-I, respectively) are two widely used bone resorption markers that attracted great attention due to their relatively high sensitivity and specificity for the degradation of type I collagen, and their rapid adaptation to automated analyzers. However, the clinical performance of both markers differs significantly depending on the clinical situation. These differences have caused considerable confusion and uncertainty. If used correctly, both markers have great potential to improve the management of many bone diseases. We here review the biochemistry, analytical background and clinical performance of NTX-I and CTX-I, as documented in the accessible literature until March 2008.

Biochemistry of amino acid racemization and clinical application to musculoskeletal disease

During aging, proteins are subject to numerous forms of damage. Several types of non-enzymatic post-translational modifications have been described in aging proteins, including oxidation, nitration, glycation, and racemization. Racemization of amino acids is the spontaneous conversion of L-enantiomers to the D-form, which is dependent on temperature, pH, and time. Because of the time-dependent nature of racemization, it can be used to determine the relative age and turnover rates of long-lived proteins. There are many such long-lived proteins within the body; they are found in the brain, eye, and heart, but are particularly abundant in proteins found in musculoskeletal tissues such as bone and cartilage. During disease, musculoskeletal tissues have pathologically altered turnover rates. Because turnover rates can be estimated from levels of racemization, racemized musculoskeletal protein fragments may serve as useful biomarkers of disease. This review discusses the biochemistry of amino acid racemization in proteins and its clinical application to musculoskeletal disease.

Alpha CTX as a Biomarker of Skeletal Invasion of Breast Cancer: Immunolocalization and the Load Dependency of Urinary Excretion

We recently showed that increased urinary excretion of the cross-linked, nonisomerized form of the C-telopeptide of collagen type I (alphaalphaCTX) could be a sensitive indicator of the presence of bone metastases in breast cancer patients. The present study was sought to investigate (a) the localization of alphaCTX epitopes in the proximity of a bone metastasis and (b) the relationship between number of metastases and the urinary excretion of alphaalphaCTX. Adjacent bone sections from breast cancer patients were stained for the presence of tumor cells (anti-cytokeratin antibody), osteoclasts (TRAcP activity), and alphaCTX (anti-alphaCTX antibody). The association between the extent of metastatic bone disease and urinary excretion of alphaalphaCTX measured with ELISA was assessed in 90 breast cancer patients (45 with bone metastasis and 45 without bone metastasis). Immunohistochemistry revealed accumulation of TRAcP-positive osteoclasts and intense staining for alphaCTX epitopes in the proximity of cytokeratin-positive bone metastasis. Areas of alphaCTX staining showed unstructured bone tissue under polarized light. In addition, there was a significant linear association between the number of bone metastases and the urinary levels of alphaalphaCTX in breast cancer patients with metastatic bone disease, independent of age and body mass index (r = 0.56, P < 0.001). The estimated relative increases in alphaalphaCTX associated with the presence of one, two, or three metastases are 38%, 57%, and 81%, respectively. Taken into account the 17% intraindividual variation of the assay, alphaalphaCTX could be a sensitive biochemical marker for the close monitoring of cancer patients aiming the facilitation of early metastasis detection.

Bone markers and current laboratory assays

Metastasis of cancer to bone leads to significant alterations in normal bone remodelling that are reflected in changes in bone turnover markers. These markers are classically defined as markers of bone resorption or formation; markers of bone resorption are measures of osteoclastic activity, whereas markers of bone formation are measures of osteoblastic activity. Recently, there has been growing interest in the use of these markers in metastatic bone disease (MBD), and an increasing number of studies have investigated the potential use of these markers in diagnosis, monitoring of disease progression and treatment, and prediction of outcome. In this review, we briefly discuss the biology of bone metastases as well as describe the bone turnover markers and their possible role in aiding clinicians in the treatment of patients with MBD.

The relative use of eight collagenous and noncollagenous markers for diagnosis of skeletal metastases in breast, prostate, or lung cancer patients

The present study was sought to assess the relative use of eight biomarkers for the detection of bone metastases in cancer forms frequently spreading to the skeleton. Participants were 161 patients with either breast, prostate, or lung cancer. The presence and extent of bone metastases was assessed by imaging techniques (computer tomography and/or magnetic resonance imaging) and Technetium-99m scintigraphy. Serum or urinary level of the bone resorption markers (alphaalphaCTX, betabetaCTX, NTX, and ICTP), formation marker (BSAP), and osteoclastogenesis markers (osteoprotegerin, RANKL, and TRAP5b) was measured by commercially available immunoassays. When assessed on a group basis, all biomarkers, except for osteoprotegerin and RANKL, were significantly elevated in patients compared with those without bone metastases (P<0.05). Biomarkers had greater diagnostic value in breast and prostate cancer patients, yet alphaalphaCTX, NTx, and ICTP were able to discriminate lung cancer patients with or without bone metastases (P<0.05). Strong linear associations were seen between the extent of skeletal infiltration and levels of the different biomarkers, except for osteoprotegerin and RANKL. Furthermore, all biomarkers (except for osteoprotegerin and RANKL) were indicative at the early stage of skeletal involvement (one to five metastases). When expressing sensitivity as the percentage increase in biomarker level relative to patients without bone metastases, alphaalphaCTX showed the largest relative increases at each stage of the metastatic disease. These results suggest that closer monitoring of cancer patients with serial measures of biomarkers might facilitate the timely diagnosis of skeletal metastases.

Biochemical Markers of Bone Turnover in the Clinical Development of Drugs for Osteoporosis and Metastatic Bone Disease

Biochemical markers of bone turnover are used increasingly during the clinical development of drugs for the treatment of metabolic bone diseases such as Paget's disease, osteoporosis and cancer that has metastasised to the bone. However, assessing the optimal value of these markers is often complicated, and such an assessment is an obvious prerequisite for rational use of the markers and, consequently, potential improvement of clinical drug development. Biochemical markers of bone turnover are substances in the blood or urine that are produced or released during bone remodelling. They provide semiquantitative information on bone remodelling, and are often the most adequate tool to describe the pharmacodynamics of the drug. Their use has increased considerably because of dose-effect relationships that have been seen with certain drugs, but also because they have proven relationships with clinical outcomes in several metabolic bone diseases. However, there is a lack of information on the kinetics of these markers, and the immunoassays that are frequently used in their monitoring often measure a mixture of fragments rather than a single molecular entity. For drug development it should also be realised that different markers, but also different assays for the same marker, may provide different results, considerably limiting the ability to compare results. In postmenopausal osteoporosis, relationships have been shown between several biochemical markers of bone turnover, and either fracture risk and/or the antifracture efficacy of drugs. Such relationships can be used for the development of drugs with similar mechanisms of action, but also for the development of these drugs for closely related indications, such as corticosteroid-induced osteoporosis. In both of these instances, data on effects on biochemical markers of bone turnover are usually employed in combination with information about effects on bone mineral density. However, the relationships of these parameters with clinical outcomes may be remarkably different for drugs with alternative mechanisms of action, challenging the use of the markers for the development of new drugs for the treatment of patients with osteoporosis. At present, the pharmacological treatment of cancer that has metastasised to the bone is limited to several bisphosphonates. Recent studies have shown relationships between the normalisation of levels of biochemical markers of bone turnover and clinical outcomes, and prospective studies investigating the application of such relationships are ongoing. The markers may play an important role in the optimisation of registered bisphosphonate treatments. However, their role in the development of new drugs is still limited to dose selection, and potential relationships with clinical outcomes remain to be investigated in instances of new mechanisms of action. Biochemical markers of bone turnover are a valuable asset for drug development, but their rational use is determined by a number of variables. Correctly manipulating these may improve clinical development of drugs for the treatment of patients with metabolic bone diseases such as osteoporosis and cancer metastatic to the bone.

Non-isomerized C-telopeptide fragments are highly sensitive markers for monitoring disease activity and treatment efficacy in Paget's disease of bone

A new resorption assay measuring non-isomerized collagen type I C-telopeptide fragments (alpha-alpha CTX) was evaluated in a cohort comprising 32 Pagetic patients and 48 healthy controls. alpha-alpha CTX was found to be a sensitive marker for assessing disease activity and monitoring treatment efficacy in Paget's disease of bone compared with isomerized CTX (beta-beta CTX) and a number of other established bone turnover markers.

INTRODUCTION

Collagen type I fragments are generated by resorbing osteoclasts, and some of them can be measured using a C-telopeptide (CTX) immunoassay. The C-telopeptide of collagen type I comprises a DG-motif susceptible to isomerization. In newly synthesized collagen, this motif is in the native form denoted alpha, but spontaneously converts to an isomerized form (beta) during aging of bone. CTX fragments composed of at least two alpha CTX chains (alpha-alpha CTX) originating from degradation of newly formed bone can be determined in the urine using a newly developed sandwich ELISA. The aim of this study was to assess the ability of this marker to monitor disease activity and treatment efficacy in patients with Paget's disease compared with established bone turnover markers.

MATERIALS AND METHODS

A total of 32 patients diagnosed with Paget's disease of bone was included in the study. All received 400 mg/day of oral tiludronate for 3 months. Urinary alpha-alpha CTX (U alpha-alpha CTX) was measured at baseline and at 1 and 6 months after discontinuation of therapy and in 48 untreated age-matched and healthy controls. Other markers of bone turnover, including urinary beta-beta CTX, N-terminal cross-linking telopeptide of type I collagen, and deoxypyridinoline, were also measured for comparison.

RESULTS AND CONCLUSIONS

The U alpha-alpha CTX marker showed a marked reduction (-82% and -77% at 1 and 6 months of treatment, respectively) in response to antiresorptive therapy in patients with Paget's disease. The response to treatment in this marker exceeded that of the other markers (p < 0.01). The alpha-alpha CTX marker also provided a high correlation (r = 0.89) to disease activity as assessed by scintigraphic activity index. In conclusion, alpha-alpha CTX seems to be a sensitive marker for assessing disease activity and monitoring treatment efficacy in Paget's disease.

Breast cancer patients with bone metastases are characterised by increased levels of nonisomerised type I collagen fragments

BACKGROUND

Fragments of collagen type I containing the epitope AHDGGR (CTX) are generated during bone resorption. The aspartyl-glycine (DG) site within CTX is synthesised in the L-aspartyl peptide (alphaL) form, but converts to the age-modified forms L-isoaspartyl peptide (betaL) and D-aspartyl peptide (alphaD) over time. The purpose of the present study was to test the ability of the various CTX forms to identify breast cancer patients with bone metastases and to investigate whether such patients had an altered CTX excretion pattern.

METHODS

In this cross-sectional study we compared CTX excretion in healthy premenopausal and postmenopausal women with CTX levels in patients with breast cancer. The breast cancer cohort comprised eight hypercalcemic patients with bone metastases (HC+), 100 normocalcemic patients with bone metastases (NC+) and 15 normocalcemic patients without bone metastases (NC-).

RESULTS

In HC+ patients and NC+ patients, the excretion of alphaL CTX was highly increased compared with NC- patients (P < 0.01), with Z scores of 3.4 and 2.0, respectively. The excretion of the age-modified forms (betaL and alphaD CTX) was less increased in HC+ patients and in NC+ patients as compared with NC- patients, with Z scores of 2.2 and 1.0, respectively, for betaL CTX, and of 1.6 and 0.8, respectively, for alphaD CTX.

CONCLUSION

Assays for the various isoforms of CTX have different sensitivities to identify patients affected by bone metastases. The alphaL CTX isoform reflecting resorption of young bone appeared to provide the best differentiation of patients affected by breast cancer-induced bone metastases. In conclusion, patients affected by metastatic bone disease present an altered excretion pattern of CTX isoforms.