Parathyroid hormone-related Peptide expression in cartilaginous tumors

The Role of Hedgehog Signaling in Tumor Induced Bone Disease

Despite significant progress in cancer treatments, tumor induced bone disease continues to cause significant morbidities. While tumors show distinct mutations and clinical characteristics, they behave similarly once they establish in bone. Tumors can metastasize to bone from distant sites (breast, prostate, lung), directly invade into bone (head and neck) or originate from the bone (melanoma, chondrosarcoma) where they cause pain, fractures, hypercalcemia, and ultimately, poor prognoses and outcomes. Tumors in bone secrete factors (interleukins and parathyroid hormone-related protein) that induce RANKL expression from osteoblasts, causing an increase in osteoclast mediated bone resorption. While the mechanisms involved varies slightly between tumor types, many tumors display an increase in Hedgehog signaling components that lead to increased tumor growth, therapy failure, and metastasis. The work of multiple laboratories has detailed Hh signaling in several tumor types and revealed that tumor establishment in bone can be controlled by both canonical and non-canonical Hh signaling in a cell type specific manner. This review will explore the role of Hh signaling in the modulation of tumor induced bone disease, and will shed insight into possible therapeutic interventions for blocking Hh signaling in these tumors.

Ollier Disease: Pathogenesis, Diagnosis, and Management

Ollier disease (Spranger type I) is a rare bone disease that is characterized by multiple enchondromatosis with a typical asymmetrical distribution and confined to the appendicular skeleton. The pathogenesis of enchondromatosis is not clearly understood. Recently, heterozygous mutations of PTHR1, IDH1 (most common), and/or IDH2 genes have been suggested by various authors as genetic aberrations. Genomic copy number alterations and mutations controlling many vital pathways are responsible for the pathogenesis of Ollier disease. A comprehensive description of all genetic events in Ollier disease is presented in this article. Clinically, Ollier disease has a wide variety of presentations. This article describes the plethora of clinical features, both common and rare, associated with Ollier disease. Multiple enchondromas are most commonly seen in phalanges and metacarpals. Radiologically, Ollier disease presents with asymmetrical osteolytic lesions with well-defined, sclerotic margins. In this article, various radiological features of Ollier disease, including radiographs, computed tomography, and magnetic resonance imaging, are also discussed. Gross pathology, cytological, and histological features of both Ollier disease and its malignant transformation are outlined. Although treatment is conservative in most cases, different possible treatment options for difficult cases are discussed. In the literature, there is a paucity of data about the disease, including diagnosis, management, prognostication, and rehabilitation, necessitating a comprehensive review to further define all of the possible domains related to this disease.

Genetic alterations in chondrosarcomas - keys to targeted therapies?

BACKGROUND

Chondrosarcomas are malignant tumors of chondrocytes and represent the second most common type of primary bone tumors. Within the context of normal chondrogenesis, this review summarizes results from recent research outlining the key molecular changes that occur during the development of this sarcoma type.

RESULTS

Current data support the notion that a two-hit scenario, common to many tumors, also underlies chondrosarcoma formation. First, early-stage mutations alter the normal proliferation and differentiation of chondrocytes, thereby predisposing them to malignant transformation. These early-stage mutations, found in both benign cartilaginous lesions and chondrosarcomas, include alterations affecting the IHH/PTHrP and IDH1/IDH2 pathways. As they are not observed in malignant cells, mutations in the EXT1 and EXT2 genes are considered early-stage events providing an environment that alters IHH/PTHrP signaling, thereby inducing mutations in adjacent cells. Due to normal cell cycle control that remains active, a low rate of malignant transformation is seen in benign cartilaginous lesions with early-stage mutations. In contrast, late-stage mutations, seen in most malignant chondrosarcomas, appear to induce malignant transformation as they are not found in benign cartilaginous lesions. These late-stage mutations primarily involve cell cycle pathway regulators including p53 and pRB, two genes that are also known to be implicated in numerous other human tumor types.

CONCLUSIONS

Now the key genetic alterations involved in both early and late stages of chondrosarcoma development have been identified, focus should be shifted to the identification of druggable molecular targets for the design of novel chondrosarcoma-specific therapies.

Gli1 inhibition suppressed cell growth and cell cycle progression and induced apoptosis as well as autophagy depending on ERK1/2 activity in human chondrosarcoma cells

The transcription factor glioma-associated oncogene 1 (Gli1) has been recognized as a very important nuclear executor at the distal end of the Hedgehog (Hh) signal pathway, which has crucial roles in regulating many developmental processes, such as pattern formation, differentiation, proliferation, and apoptosis. Overexpression of patched 1 protein and Gli1 or constitutively active Indian Hedgehog (IHh)-parathyroid hormone-related protein signal pathway may lead to musculoskeletal tumorigenesis. However, for chondrosarcoma few studies have paid close attention to the IHh-Gli1 signal transduction cascade and more work needs to be carried out to fully elucidate Gli1 protein functions. Here we show that the IHh signal pathway was activated in chondrosarcoma, and knocking down the expression of Gli1 attenuated the disturbed IHh signal pathway, which not only suppressed cell proliferation and promoted G2/M cell cycle arrest but also enhanced cell apoptosis by downregulating Bcl-2 and Bcl-xl expression. Furthermore, Gli1 downregulation, not cyclopamine, induced autophagy by regulating mTOR phosphorylation, and inhibition of autophagy prevented Gli1 small interfering RNA-mediated cell death. We also demonstrated that extracellular signal-regulated kinase 1/2 activity may mediate these antiproliferative events induced by Gli1 inhibition. These results indicate that Gli1 inhibition could ultimately provide a promising new approach for chondrosarcoma treatment.

Chondrosarcomas revisited

Chondrosarcomas are malignant bone tumors with pure hyaline cartilage differentiation; myxoid changes, calcification, or ossification may be present. Several subtypes of chondrosarcomas exist. Behavior patterns vary, ranging from slow-growing nonmetastasizing lesions to aggressive metastasizing sarcomas. Symptoms are usually mild, with duration ranging from several months to years, and usually consist of persistent, dull, aching pain or palpable masses. Radiographic findings include bone expansion with cortical thickening, radiolucent areas with variably distributed punctate or ring-like matrix calcifications, cortical erosion or destruction, endosteal scalloping, and scant or absent periosteal reaction; extension into the soft tissue may be present. Histological differential diagnosis from benign cartilaginous lesions can be achieved by increased cellularity, enlarged plump nuclei, binucleated cells, hyperchromatic nuclear pleomorphism, and permeation of cortical or medullary bone. Atypia is usually mild to moderate; necrosis and mitoses can be seen, particularly in high-grade lesions. Adequate surgery is the mainstay of treatment. High-grade and pelvic chondrosarcomas are best managed with wide resection. Because of the low metastatic potential and low local recurrence rate noted with intralesional surgery, low-grade chondrosarcomas can be treated with curettage (with or without treatment of the defect cavity) with a local adjuvant, such as phenol or cryotherapy. Adjuvant chemotherapy may be considered for mesenchymal and dedifferentiated chondrosarcomas. Radiation therapy can be considered after incomplete resection or if resection is not feasible or would cause unacceptable morbidity.

PTHR1 mutations associated with Ollier disease result in receptor loss of function

PTHR1-signaling pathway is critical for the regulation of endochondral ossification. Thus, abnormalities in genes belonging to this pathway could potentially participate in the pathogenesis of Ollier disease/Maffucci syndrome, two developmental disorders defined by the presence of multiple enchondromas. In agreement, a functionally deleterious mutation in PTHR1 (p.R150C) was identified in enchondromas from two of six unrelated patients with enchondromatosis. However, neither the p.R150C mutation (26 tumors) nor any other mutation in the PTHR1 gene (11 patients) could be identified in another study. To further define the role of PTHR1-signaling pathway in Ollier disease and Maffucci syndrome, we analyzed the coding sequences of four genes (PTHR1, IHH, PTHrP and GNAS1) in leucocyte and/or tumor DNA from 61 and 23 patients affected with Ollier disease or Maffucci syndrome, respectively. We identified three previously undescribed missense mutations in PTHR1 in patients with Ollier disease at the heterozygous state. Two mutations (p.G121E, p.A122T) were present only in enchondromas, and one (p.R255H) in both enchondroma and leukocyte DNA. Assessment of receptor function demonstrated that these three mutations impair PTHR1 function by reducing either the affinity of the receptor for PTH or the receptor expression at the cell surface. These mutations were not found in DNA from 222 controls. Including our data, PTHR1 functionally deleterious mutations have now been identified in five out 31 enchondromas from Ollier patients. These findings provide further support for the idea that heterozygous mutations in PTHR1 that impair receptor function participate in the pathogenesis of Ollier disease in some patients.

Patched-one or smoothened gene mutations are infrequent in chondrosarcoma

Constitutive hedgehog signaling has been implicated in the tumorigenesis of cartilaginous neoplasia; however, a common mutational mechanism remains unknown. Some tumors exhibiting hedgehog pathway activation such as basal cell cancer frequently harbor PATCHED-ONE (PTCH-1) or SMOOTHENED (SMO) gene mutations. We therefore asked whether mutations of the hedgehog receptor genes PTCH-1 or SMO occur in cartilage tumors. Singlestrand conformation polymorphism (SSCP) analysis with subsequent manual sequencing was performed to detect alterations of PTCH-1 and SMO in 46 cartilage tumors. SSCP detected five shifts in the PTCH-1 gene and two shifts in SMO. Direct DNA sequencing revealed the five shifts in PTCH-1 were caused by silent nucleotide alterations. The two SMO shifts were the result of the same missense mutation (783G>A) and occurred in one dedifferentiated chondrosarcoma and a synovial chondromatosis. The patient with chondromatosis also carried this same mutation in the germline. However, this mutation was also identified in leukocyte DNA from three of 127 (2.4%) control subjects without cartilage tumors, suggesting it may represent a rare SMO variant. Constitutive activation of the hedgehog signaling pathway in chondrosarcoma is rarely caused by PTCH-1 or SMO mutations. [corrected]

The clinical approach towards chondrosarcoma

This review provides an overview of the histopathology, classification, diagnostic procedures, and therapy of skeletal chondrosarcoma. Chondrosarcomas that arise de novo are primary chondrosarcomas, whereas chondrosarcomas developing superimposed on pre-existing benign cartilage neoplasms such as enchondromas or osteochondromas are referred to as secondary chondrosarcomas. Conventional chondrosarcomas can be categorized according to their location in bone into central, peripheral, and juxtacortical chondrosarcomas. Histological grading is related to prognosis; however, it is also subject to interobserver variability. Rare subtypes of chondrosarcoma, including dedifferentiated, mesenchymal, and clear cell chondrosarcoma, are discussed as well. Magnetic resonance imaging is necessary to delineate the extent of the intraosseous and soft tissue involvement preoperatively. Computed tomography is especially recommended in the pelvis and other flat bones where it may be difficult to discern the pattern of bone destruction and the presence of matrix mineralization. Wide, en-bloc excision is the preferred surgical treatment in intermediate- and high-grade chondrosarcoma. In low-grade chondrosarcoma confined to the bone, extensive intralesional curettage followed by local adjuvant treatment and filling the cavity with bone graft has promising long-term clinical results and satisfactory local control. Chondrosarcomas are relatively radiotherapy resistant; therefore, doses >60 Gy are needed in attempts to achieve local control after incomplete resection. Irradiation with protons or other charged particles seems beneficial in this curative situation. Chemotherapy is only possibly effective in mesenchymal chondrosarcoma, and is of uncertain value in dedifferentiated chondrosarcoma. Potential new systemic treatment targets are being discussed.

Over-expression of parathyroid hormone Type 1 receptor confers an aggressive phenotype in osteosarcoma

Osteosarcoma is the most common primary bone malignancy in children and is associated with rapid bone growth. Parathyroid hormone-related peptide (PTHrP) signaling via parathyroid hormone Type 1 receptor (PTHR1) is important for skeletal development and is involved in bone metastases in other tumors. The aim of this study was to investigate the status of PTHrP/PTHR1 and its possible role in osteosarcoma. In a preliminary screening, a higher level of PTHR1 mRNA, but not PTHrP, was found in 4 osteosarcoma xenografts as compared with 4 standard cell lines, or 5 patient derived cell lines (p < 0.05) using quantitative RT-PCR. It was therefore extended to 55 patient specimens, in which a significantly higher level of PTHR1 mRNA was detected in metastatic or relapsed samples than those from primary sites (p < 0.01). Cell behavior caused by PTHR1 overexpression was further studied in vitro using PTHR1 transfected HOS cell line as a model. Over-expression of PHTR1 resulted in increased proliferation, motility and Matrigel invasion without addition of exogenous PTHrP suggesting an autocrine effect. Importantly, the aggressiveness in PTHR1-expressing cells was completely reversed by RNAi mediated gene knockdown. In addition, PTHR1 over-expression led to delayed osteoblastic differentiation and upregulation of genes involved in extracellular matrix production, such as TGF-beta1 and connective tissue growth factor. When cocultured with bone marrow derived monocytes, PTHR1 transfected HOS cells induced a greater number of osteoclasts. This study suggests that PTHR1 over-expression may promote osteosarcoma progression by conferring a more aggressive phenotype, and forming a more favorable microenvironment.

Ollier disease

Enchondromas are common intraosseous, usually benign cartilaginous tumors, that develop in close proximity to growth plate cartilage. When multiple enchondromas are present, the condition is called enchondromatosis also known as Ollier disease (WHO terminology). The estimated prevalence of Ollier disease is 1/100,000. Clinical manifestations often appear in the first decade of life. Ollier disease is characterized by an asymmetric distribution of cartilage lesions and these can be extremely variable (in terms of size, number, location, evolution of enchondromas, age of onset and of diagnosis, requirement for surgery). Clinical problems caused by enchondromas include skeletal deformities, limb-length discrepancy, and the potential risk for malignant change to chondrosarcoma. The condition in which multiple enchondromatosis is associated with soft tissue hemangiomas is known as Maffucci syndrome. Until now both Ollier disease and Maffucci syndrome have only occurred in isolated patients and not familial. It remains uncertain whether the disorder is caused by a single gene defect or by combinations of (germ-line and/or somatic) mutations. The diagnosis is based on clinical and conventional radiological evaluations. Histological analysis has a limited role and is mainly used if malignancy is suspected. There is no medical treatment for enchondromatosis. Surgery is indicated in case of complications (pathological fractures, growth defect, malignant transformation). The prognosis for Ollier disease is difficult to assess. As is generally the case, forms with an early onset appear more severe. Enchondromas in Ollier disease present a risk of malignant transformation of enchondromas into chondrosarcomas.

Soft tissue osteochondroma: case report and immunohistochemistry for parathyroid hormone–related protein

Surface lesions of bone usually present little diagnostic dilemma because the majority are conventional osteochondromas. Other surface bone lesions include periosteal chondroma, periosteal chondrosarcoma, and parosteal osteosarcoma. Mineralized soft tissue lesions such as myositis ossificans, synovial chondroma, and synovial sarcoma may present in a similar fashion when they occur in a juxtaarticular position. The soft tissue osteochondroma or paraarticular osteochondroma may simulate some of these more aggressive tumors, and its recognition is important to avoid overtreatment. A case of an 11-year-old male with a soft tissue osteochondroma is reported to illustrate the characteristic radiographic and histological features of this rare entity. No prior reports have examined soft tissue osteochondroma for expression of parathyroid hormone related protein, an established cartilage tumor proliferative mitogen.

Constitutive hedgehog signaling in chondrosarcoma up-regulates tumor cell proliferation

Chondrosarcoma is a malignant cartilage tumor that may arise from benign precursor lesions, such as enchondromas. Some cases of multiple enchondromas are caused by a mutation that results in constitutive activation of Hedgehog-mediated signaling. We found that chondrosarcomas expressed high levels of the Hedgehog target genes PTCH1 and GLI1. Treatment with parathyroid hormone-related protein down-regulated Indian Hedgehog (IHH) expression in normal growth plates but not in chondrosarcoma or enchondroma organ cultures. Treatment of the chondrosarcoma organ cultures with Hedgehog protein increased cell proliferation rate, whereas addition of chemical inhibitors of Hedgehog signaling decreased the proliferation rate. Chondrosarcoma xenografts from 12 different human tumors were established in NOD-SCID mice. Treatment with triparanol, an inhibitor of Hedgehog signaling, resulted in a 60% decrease in tumor volume, a 30% decrease in cellularity, and a 20% reduction in proliferation rate. These results show that Hedgehog signaling is active in chondrosarcoma and benign cartilage tumors and regulates tumor cell proliferation. Our data raise the intriguing possibility that Hedgehog blockade could serve as an effective treatment for chondrosarcoma, a tumor for which there are currently no universally effective nonsurgical management options.

Proinflammatory cytokines and metalloproteases are expressed in the subacromial bursa in patients with rotator cuff disease

PURPOSE

The pathophysiology of subacromial impingement syndrome is poorly understood. We investigated the expression of inflammatory cytokines, metalloproteases, and the cyclooxygenases in the subacromial bursa in control patients and in patients with rotator cuff tear.

TYPE OF STUDY

Basic science evaluation.

METHODS

Eighteen patients undergoing shoulder surgery had a subacromial bursa biopsy examination. Patients were divided into 2 groups. Group I (study group) had 10 patients with a full-thickness rotator cuff tear (RCT). Group II (control group) had 8 patients. Seven of 8 underwent shoulder arthroscopy with anterior capsular reconstruction for instability; 1 of 8 underwent open reduction internal fixation for acute proximal humerus fracture. None of the patients in group II had any history of symptoms or signs consistent with subacromial impingement. H&E and immunohistochemical antibody (MMP-1, MMP-9, IL-1, IL-6, TNF-alpha, COX-1, and COX-2) stained specimens were examined by 2 blinded observers using a histologic scale (grade 0 = no staining to grade 4 = intense staining).

RESULTS

Histologic evidence of inflammation was present in all patients with RCT (group I). No or mild inflammation was noted in group II. The average staining grade for inflammatory cytokines (IL-1, IL-6, TNF-alpha) and proteinases (MMP-1 and MMP-9) was significantly more pronounced in the RCT group (P < .001). Cyclooxygenase enzymes (COX-1 and COX-2) were also increased in group II (P < .001).

CONCLUSIONS

A high level of expression of inflammatory cytokines, proteinases, and cyclooxygenase enzymes, known to produce a catabolic environment, is present in the subacromial bursa of patients with rotator cuff tear.

CLINICAL RELEVANCE

These findings support the role of nonsteroidal anti-inflammatory drugs and corticosteroids in RCT treatment, and emphasize the importance of subacromial bursectomy to reduce inflammation in RCT surgery.

Emerging pathways in the development of chondrosarcoma of bone and implications for targeted treatment

Chondrosarcoma is a malignant cartilage-forming tumour of bone, of which distinct clinicopathological subtypes are known. Conventional chondrosarcoma is notorious for its locally aggressive behaviour as well as for its resistance to chemotherapy and radiotherapy; so far surgery is the only effective therapeutic option. During the past 10 years, substantial new insights have been gained about molecular cell biology, molecular cytogenetics, and immunopathology, leading to better understanding of chondrosarcoma development at the molecular level, which will ultimately lead to better clinical understanding and possibly to the development of targeted treatment.

Absence of IHH and retention of PTHrP signalling in enchondromas and central chondrosarcomas

Enchondromas and conventional central chondrosarcomas are, respectively, benign and malignant hyaline cartilage-forming tumours that originate in the medulla of bone. In order to gain a better understanding of the molecular process underlying malignant transformation of enchondroma, and to investigate whether there is a biological difference between conventional central cartilaginous tumours and those of enchondromatosis or with phalangeal localization, a series of 64 enchondromas (phalanx, n = 21; enchondromatosis, n = 15) and 89 chondrosarcomas (phalanx, n = 17; enchondromatosis, n = 13) was collected. Indian Hedgehog (IHH)/parathyroid hormone related peptide (PTHrP) signalling, an important pathway in chondrocyte proliferation and differentiation within the normal growth plate, was studied by immunohistochemical analysis of the expression of PTHrP, PTHR1, Bcl-2, p21, cyclin D1, and cyclin E. Quantitative real-time PCR for IHH, PTCH, SMO, and GLI2 was performed on a subset of tumours. The data show that IHH signalling is absent in enchondromas and central chondrosarcomas, while PTHrP signalling is active. There was no difference in the expression of any of the molecules between 35 enchondromas and 26 grade I central chondrosarcomas, indicating that PTHrP signalling is not important in malignant transformation of enchondroma. Higher expression of PTHR1 and Bcl-2 was associated with increasing histological grade in chondrosarcoma, suggesting involvement in tumour progression. No difference was found between samples from enchondromatosis patients and solitary cases, suggesting no difference in PTHrP signalling. A small subset of phalangeal chondrosarcomas demonstrated down-regulation of PTHrP, which may be related to its more indolent clinical behaviour. Thus, in both enchondromas and central chondrosarcomas, PTHrP signalling is active and independent of IHH signalling, irrespective of the presence or absence of enchondromatosis.

The use of Bcl-2 and PTHLH immunohistochemistry in the diagnosis of peripheral chondrosarcoma in a clinicopathological setting

Distinguishing osteochondroma from low-grade secondary peripheral chondrosarcoma can be difficult. In osteochondroma, growth-signalling pathways are thought to be downregulated through exostosin (EXT) inactivation. A previous pilot study focusing on expression of putative EXT downstream effectors indicated that progression of osteochondroma towards grade I chondrosarcoma was characterised by upregulation of Bcl-2 and parathyroid hormone-like hormone (PTHLH). We investigated their use as diagnostic markers in a large nationwide series of 71 osteochondromas and 34 chondrosarcomas. Bcl-2 immunohistochemistry proved to be a valuable diagnostic tool: scoring negative in 95% (specificity) of the osteochondromas and positive in 57% (sensitivity) of the chondrosarcomas, reaching a positive predictive value of 84% and negative predictive value of 82%. Positivity was not related to age, hereditary status, gender or thickness of the cartilage cap. Presence of internal controls and verification using mRNA in situ hybridisation strengthened the reliability of the immunohistochemical staining. PTHLH showed more variable staining, being positive in osteochondromas from females or adolescent males, suggesting age- and gender-dependent expression. Thus, in cases where the distinction between osteochondroma and chondrosarcoma is difficult, Bcl-2 is a valuable diagnostic marker for malignancy, regardless of tumour size, patient gender or age, and this can be extended with PTHLH for non-adolescent male patients.

Telomerase reverse transcriptase subunit expression is associated with chondrosarcoma malignancy

Expression of the telomerase reverse transcriptase subunit telomerase reverse transcriptase gene is associated with most human malignancies. Because telomerase reverse transcriptase is rarely expressed in normal tissue, its presence in pathologic specimens is considered a marker of transformed cells. Moreover, high levels of expression have been correlated with poor prognosis in many cancers. Although telomerase activity has been found in chondrosarcomas, its prognostic significance in these malignant cartilage tumors is unknown. Malignancy in cartilage-derived tumors is assessed routinely by histomorphologic grading, but even well differentiated, low-grade lesions can metastasize. This unpredictable behavior greatly complicates the clinical treatment of cartilage tumors, making better prognostic indicators desirable. To address this issue we used immunohistochemistry to compare telomerase reverse transcriptase expression in a collection of 61 tumors consisting of malignant chondrosarcomas of varying grade and benign enchondromas. Associated case histories were reviewed to test the hypothesis that telomerase reverse transcriptase expression levels correlated with subsequent tumor recurrence. We found that the relative abundance of telomerase reverse transcriptase-expressing cells correlated significantly with grade and recurrence. These findings indicate that telomerase reverse transcriptase immunostaining may be a useful adjunct to the conventional three-level grading system.