Molecular Profiling of Giant Cell Tumor of Bone and the Osteoclastic Localization of Ligand for Receptor Activator of Nuclear Factor κB

Abstract

Giant cell tumor of bone (GCT) is a generally benign, osteolytic neoplasm comprising stromal cells and osteoclast-like giant cells. The osteoclastic cells, which cause bony destruction, are thought to be recruited from normal monocytic pre-osteoclasts by stromal cell expression of the ligand for receptor activator of nuclear factor kappaB (RANKL). This model forms the foundation for clinical trials in GCTs of novel cancer therapeutics targeting RANKL. Using expression profiling, we identified both osteoblast and osteoclast signatures within GCTs, including key regulators of osteoclast differentiation and function such as RANKL, a C-type lectin, osteoprotegerin, and the wnt inhibitor SFRP4. After ex vivo generation of stromal- and osteoclast-enriched cultures, we unexpectedly found that RANKL mRNA and protein were more highly expressed in osteoclasts than in stromal cells, as determined by expression profiling, flow cytometry, immunohistochemistry, and reverse transcriptase-polymerase chain reaction. The expression patterns of molecules implicated in signaling between stromal cells and monocytic osteoclast precursors were analyzed in both primary and fractionated GCTs. Finally, using array-based comparative genomic hybridization, neither GCTs nor the derived stromal cells demonstrated significant genomic gains or losses. These data raise questions regarding the role of RANKL in GCTs that may be relevant to the development of molecularly targeted therapeutics for this disease.

Gene expression profiling identifies p63 as a diagnostic marker for giant cell tumor of the bone

“…17,18 Interestingly, TP73L whose protein product is p63 was among the significantly upregulated genes identified for GCTOB even though none of the earlier gene expression profiling studies on GCTOB identified p63 as being highly expressed. 15,16,19 A closer examination of the TP73L expression in this series of tumors revealed that its expression was the highest in four of the six GCTOB whereas the other two GCTOB showed similar levels of TP73L expression as seen in ABC and FD. GCTTS/DTGCT showed a much lower level of TP73L in contrast to GCTOB.…”

“…15,16,19 Thomas and co-workers have recently published the gene expression profile of 9 GCTOB together with a series of undifferentiated pleomorphic sarcomas, liposarcomas, leiomyosarcomas and synovial sarcomas for comparison. 15 Although they found relatively high expression of TP73L in 3 of the 9 GCTOB, they also noted expression in 3 of 11 undifferentiated pleomorphic sarcomas, 3 of 9 leiomyosarcomas and 1 of 4 synovial sarcomas with similarly high expression levels for TP73L. TP73L was therefore not identified as a significant marker for GCTOB in their study.…”

“…When compared to the other specimens, many of the highly expressed genes like CA2, MMP13, CKB, TNFSF11, VNN1 and COL10A1 were found in earlier studies to be highly expressed in GCTOB. 15,16 TNFSF11 or ligand for receptor activator of NFkB (RANKL) is known to be expressed by the mononuclear stromal cells in GCTOB and promotes osteoclast formation. 17 Furthermore, several other ligands including a receptor-ligand pair-FGFR2 and FGF9-were found to be highly expressed in GCTOB.…”

Histogenetic Characterization of Giant Cell Tumor of Bone

“…In agreement with a putative osteogenic origin of SC, osteoid foci may be found both inside and at the periphery of GCT [8,41], and bone formation, but no evidence of osteoclastogenesis has been observed in immunodeficient mice after subcutaneous injection of GCT tissue or cells [2,24]. Molecular profiling of GCT has recently demonstrated RANKL is highly expressed in GC but not in SC, suggesting the GC component of GCT is unlikely to be recruited as a result of RANKL production by SC [35]. Thus, neither cytogenetic nor molecular analysis has provided consistent evidence the SC are the neoplastic element.…”

“…As a result of the presence of a remarkably high number of osteoclast-like GC, early researchers suggested GCT was a neoplasm of the osteoclastic lineage, hence the term ''osteoclastoma'' [7]. However, GC show typical features of normal osteoclasts, including calcitonin and vitronectin receptor expression, tartrate-resistant acid phosphatase (TRACP) activity, and lacunar resorption ability [1,14,30,35]. SC were therefore believed the most likely candidate neoplastic elements of GCT, partly based on their ability to grow both in vitro and in vivo [2,24].…”