Circulating concentrations of IGF-I and IGFBP-3 are not predictive of incidence or clinical behavior of pediatric osteosarcoma

Serum tumor markers in pediatric osteosarcoma: a summary review

Osteosarcoma is the most common primary high-grade bone tumor in both adolescents and children. Early tumor detection is key to ensuring effective treatment. Serum marker discovery and validation for pediatric osteosarcoma has accelerated in recent years, coincident with an evolving understanding of molecules and their complex interactions, and the compelling need for improved pediatric osteosarcoma outcome measures in clinical trials. This review gives a short overview of serological markers for pediatric osteosarcoma, and highlights advances in pediatric osteosarcoma-related marker research within the past year. Studies in the past year involving serum markers in patients with pediatric osteosarcoma can be assigned to one of four categories, i.e., new approaches and new markers, exploratory studies in specialized disease subsets, large cross-sectional validation studies, and longitudinal studies, with and without an intervention.Most of the studies have examined the association of a serum marker with some aspect of the natural history of pediatric osteosarcoma. As illustrated by the many studies reviewed, several serum markers are emerging that show a credible association with disease modification. The expanding pool of informative osteosarcoma-related markers is expected to impact development of therapeutics for pediatric osteosarcoma positively and, it is hoped, ultimately clinical care. Combinations of serum markers of natural immunity, thyroid hormone homeostasis, and bone tumorigenesis may be undertaken together in patients with pediatric osteosarcoma. These serum markers in combination may do better. The potential effect of an intrinsic dynamic balance of tumor angiogenesis residing within a single hormone (tri-iodothyronine) is an attractive concept for regulation of vascularization in pediatric osteosarcoma.

Haplotype effect in the IGF1 promoter accounts for the association between microsatellite and serum IGF1 concentration

OBJECTIVE

Systemic insulin-like growth factor 1 (IGF1) level is an important risk factor for various diseases. The inter-individual variation of serum IGF1 is determined by environmental and genetic factors, which are attributed to a microsatellite in IGF1 promoter. However, the exact nature of the underlying regulatory elements accounting for this association has not been characterized. Here, we defined the haplotype patterns, including both SNPs and the microsatellite, in the Chinese population, and investigated their regulatory effect on serum IGF1 level. This is the first study in which haplotype patterns of the microsatellite and SNPs in the IGF1 promoter are examined together.

METHODS

The linkage disequilibrium (LD) patterns of IGF1 were examined using tagSNPs of the IGF1 regulatory region. The microsatellite, three tagSNPs and haplotypes were correlated with serum IGF1 concentration in 450 normal premenopausal Chinese women.

RESULTS

Common alleles of the microsatellite were in strong LD with the three tagSNPs and were associated with particular haplotypes composed of SNPs. Neither the CA repeat number nor SNPs alone showed a robust association with serum IGF1 concentration. On the other hand, the haplotype T-19-A-T was significantly associated with serum IGF1 level.

CONCLUSION

No association was found between SNPs and microsatellite alone. However, the haplotype showed better correlation with serum IGF1 level. The results indicate that the previously observed correlation with microsatellite was because of a haplotype effect in the IGF1 promoter. Microsatellite or tagSNPs alone are not the primary regulatory elements of IGF1 expression. The exact regulatory genetic variant needs to be defined by functional genetic studies.

Insulin receptor isoform A and insulin-like growth factor II as additional treatment targets in human osteosarcoma

Despite the frequent presence of an insulin-like growth factor I receptor (IGFIR)-mediated autocrine loop in osteosarcoma (OS), interfering with this target was only moderately effective in preclinical studies. Here, we considered other members of the IGF system that might be involved in the molecular pathology of OS. We found that, among 45 patients with OS, IGF-I and IGFBP-3 serum levels were significantly lower, and IGF-II serum levels significantly higher, than healthy controls. Increased IGF-II values were associated with a decreased disease-free survival. After tumor removal, both IGF-I and IGF-II levels returned to normal values. In 23 of 45 patients, we obtained tissue specimens and found that all expressed high mRNA level of IGF-II and >IGF-I. Also, isoform A of the insulin receptor (IR-A) was expressed at high level in addition to IGFIR and IR-A/IGFIR hybrids receptors (HR(A)). These receptors were also expressed in OS cell lines, and simultaneous impairment of IGFIR, IR, and Hybrid-Rs by monoclonal antibodies, siRNA, or the tyrosine kinase inhibitor BMS-536924, which blocks both IGFIR and IR, was more effective than selective anti-IGFIR strategies. Also, anti-IGF-II-siRNA treatment in low-serum conditions significantly inhibited MG-63 OS cells that have an autocrine circuit for IGF-II. In summary, IGF-II rather than IGF-I is the predominant growth factor produced by OS cells, and three different receptors (IR-A, HR(A), and IGFIR) act complementarily for an IGF-II-mediated constitutive autocrine loop, in addition to the previously shown IGFIR/IGF-I circuit. Cotargeting IGFIR and IR-A is more effective than targeting IGF-IR alone in inhibiting OS growth.

Osteosarcoma and acromegaly: a case report and review of the literature

A 72-yr-old acromegalic man, who presented with pain in the left femur, was found to have a metastatic osteosarcoma. Only three cases describing the coexistence of acromegaly and osteosarcoma have been reported by the literature. As the patient didn't have other risk factors for osteosarcoma, the hypothesis that accelerated rate of bone turnover caused by long-term exposure to high GH and IGF-I could act as a predisposing factor in the development of this malignant bone tumor is discussed.

IGF-1 receptor contributes to the malignant phenotype in human and canine osteosarcoma

To further define the role of insulin-like growth factor-1 (IGF-1) and its receptor (IGF-1R) in osteosarcoma (OS), human OS cell lines with low (SAOS-2) and high (SAOS-LM2) metastatic potential and three canine OS-derived cell lines were studied. Cell lines were evaluated for: IGF-1R expression; expression of IGF binding proteins (IGFBPs); effect of IGF-1 on tumor cell growth, invasion, expression of urokinase plasminogen activator (uPA), and soluble uPA receptor (suPAR), and; ectopic and orthotopic tumorigenicity of the canine OS cells in athymic mice. All cell lines exhibited steady-state mRNA expression of IGF-1R. The SAOS-2 and SAOS-LM2 cells expressed 9,138 and 10,234 cell-associated binding sites, respectively. Canine OS cells expressed from 1,728 to 3,883 binding sites. Two IGF-1-treated cell lines displayed enhanced proliferation. Two cell lines formed colonies in semisolid media, and IGF-1 increased colony number. Matrigel invasion was enhanced in one cell line following IGF-1 treatment. uPA and suPAR were unchanged in SAOS-2 and SAOS-LM2 cells following IGF-1 treatment, but the highly metastatic OS line SAOS-LM2 expressed five times more suPAR and displayed enhanced invasion compared to the parental, low metastatic SAOS-2. IGFBP-5 was detected in four of five cell lines, and IGFBP-3 was detected in two canine OS cell lines. Two canine OS lines were tumorigenic, and one metastasized spontaneously. In conclusion, OS cells express IGF-1R, which can contribute to their growth and invasion. There is suggestive evidence that increasing receptor number may contribute to in vivo tumorigenesis. Additional studies are needed to determine how IGF-1/IGF-1R interactions contribute to the malignant phenotype of OS.

Etiology of osteosarcoma

Although the prognosis and quality of life of patients with osteosarcoma were improved significantly during the past decades, the pathogenesis and etiology of this disease remain obscure. Significant interest and effort in this cancer led to the identification of numerous etiologic agents. Several chemical agents such as beryllium, viruses such as FBJ, subsequently found to contain the src-oncogene, and radiation were shown to be potent inducers of osteosarcoma. Paget's disease, electrical burn, or trauma all are thought to be other factors that may contribute to the pathogenesis. More recently, patients with hereditary diseases such as Rothmund-Thomson syndrome, Bloom syndrome, and Li-Fraumeni syndrome were found to have an increased risk of having osteosarcoma develop. During the past few years, the molecular analysis brought a wealth of new information with numerous genes that were associated with osteosarcoma and its clinical disease progression. They can be categorized into self-sufficiency in growth signals, insensitivity to growth inhibitory signals, evasion of apoptosis, limitless replicative potential, sustained angiogenesis, and tissue evasion and metastasis. Although the understanding of these processes in osteosarcoma still is incomplete, it may have the potential to significantly affect the patient care in the future.