H-ras oncogene mutation in dedifferentiated chondrosarcoma: polymerase chain reaction-restriction fragment length polymorphism analysis

The Rat Sarcoma Virus (RAS) Family of Proteins in Sarcomas

The rat sarcoma virus (RAS) protein family plays a crucial role in facilitating communication both within and between cells, thereby governing fundamental cellular processes such as growth, survival, and differentiation. The RAS family comprises four members of small GTPases, namely Harvey RAS (H-RAS), Kirsten RAS (K-RAS, two splice variants, 4A and 4B), and Neuroblastoma RAS (N-RAS), and these are encoded by three cellular RAS genes. Mutations in these genes play a significant role in cancer development and progression. Accordingly, here we review and discuss currently available literature about the fate and function of the RAS family of proteins in sarcomas.

Dedifferentiated Chondrosarcoma: Diagnostic Controversies and Emerging Therapeutic Targets

PURPOSE OF REVIEW

The pathogenesis of dedifferentiated chondrosarcoma is controversial, and no genetic abnormality has consistently been identified in the disease. Focusing on the diagnostic challenges encountered in dedifferentiated chondrosarcoma, the following review aims at summarizing the tumor's active neoplastic pathways while highlighting therapeutic modalities that could potentially be explored to enhance patient survivorship.

RECENT FINDINGS

Owing to the challenging examination of small needle biopsy sampling as well as the disease's overlapping morphological and immunohistochemical features with other bone and soft-tissue sarcomas, the diagnosis of dedifferentiated chondrosarcoma can be problematic. While combined doxorubicin- and cisplatin-based regimens remain the first-line systemic chemotherapy in the disease, ~50% of tumors carry EXT1/2 or IDH1/2 mutations, advancing EXT or IDH inhibitors as potential alternative therapies, respectively. Despite systemic chemotherapy, dedifferentiated chondrosarcoma remains an aggressive tumor with dismal prognosis and limited survival. A multidisciplinary collaboration across multiple cancer centers is warranted to yield an accurate diagnosis, understand the disease's underlying pathogenesis, develop adequate treatment, and improve patient survivorship.

H3K27me3 deficiency defines a subset of dedifferentiated chondrosarcomas with characteristic clinicopathological features

Dedifferentiated chondrosarcoma is a rare bone sarcoma, whose genetic background remains incompletely understood. Mutations in SUZ12 or EED, which encode polycomb repressive complex 2 (PRC2) components, and resulting deficiency in H3K27me3 are characteristic features of the majority of malignant peripheral nerve sheath tumors. Here, we investigated H3K27me3 and PRC2 status in dedifferentiated chondrosarcoma. Among 19 evaluable dedifferentiated chondrosarcoma cases, six (32%) showed immunohistochemical loss of H3K27me3 only in the dedifferentiated component, whereas the well-differentiated component retained H3K27me3. H3K27me3-deficient dedifferentiated chondrosarcoma occurred in two men and four women with a median age of 66. All of these tumors affected bones of the upper half of the body, with the ribs being preferentially involved, which represented a significantly different distribution compared to that in the 13 H3K27me3-intact dedifferentiated chondrosarcomas. H3K27me3-deficient dedifferentiated chondrosarcomas were histologically different from H3K27me3-intact dedifferentiated chondrosarcomas, as the former invariably demonstrated dedifferentiated histology with a striking similarity to classic malignant peripheral nerve sheath tumor, comprising sweeping to swirling fascicles of relatively uniform spindle cells. Heterologous rhabdomyoblastic differentiation, the focal presence of grade 3 chondrosarcoma histology, and a cartilaginous component in the metastatic sites were exclusively seen in some cases of H3K27me3-deficient dedifferentiated chondrosarcoma. In all three H3K27me3-deficient dedifferentiated chondrosarcomas that contained focal grade 3 histology, dedifferentiated components did not juxtapose to the grade 3 areas but transitioned abruptly from the grade 1-2 components. Targeted next generation sequencing, which was successfully performed on four H3K27me3-deficient dedifferentiated chondrosarcomas, identified an IDH2 mutation in one case and COL2A1 truncations in three cases. The dedifferentiated areas of three cases harbored SUZ12 or EED alterations, which were absent in the well-differentiated component, suggesting a role for PRC2 aberrations in dedifferentiation. H3K27me3 deficiency defines a novel subset of dedifferentiated chondrosarcoma that requires recognition because of its diagnostic and potential clinical implications.

The molecular pathogenesis of dedifferentiated chondrosarcoma

Dedifferentiated chondrosarcomas are cartilaginous tumors that consist of two distinguishable components, a lowgrade chondrosarcoma (chondrogenic) component and a highgrade dedifferentiated (anaplastic) component. The tumor cells in both components seem to originate from a single precursor, but there are a substantial number of genetic alterations in the anaplastic component. The underlying mechanism of dedifferentiation is unknown, but cell cycle regulators p16, p53 and retinoblastoma appear to have important roles in tumor development and dedifferentiation. In this article, molecular pathogenesis of dedifferentiated chondrosarcomas is reviewed.

Regulation of onco and tumor suppressor MiRNAs by mTORC1 inhibitor PRP-1 in human chondrosarcoma

Metastatic chondrosarcoma of mesenchymal origin is the second most common bone malignancy and does not respond either to chemotherapy or radiation; therefore, the search for new therapies is relevant and urgent. This study aimed to reveal the comparative analysis of miRNAs and their targets in human JJ012 chondrosarcoma cell line between control and experimental samples, treated with mTORC1 inhibitor, cytostatic antiproliferative proline-rich polypeptide (PRP-1). Examination of tumor-specific microRNA expression profiles has revealed widespread deregulation of these molecules in diverse cancers. It was reported that microRNAs can function as novel biomarkers for disease diagnostics and therapy, as well as a novel class of oncogenes and tumor suppressor genes. mTORC 1 inhibitor PRP-1 caused significant upregulation of tumor suppressors, such as miR20a, miR125b, and miR192; and downregulation of onco miRNAs, miR509-3p, miR589, miR490-3p, miR 550 in human chondrosarcoma JJ012 cell line.

GISTogram: a graphic presentation of the growing GIST complexity

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. They have represented a paradigm of molecular-targeted therapies for solid tumors since the discovery of KIT mutations and KIT expression in GIST in 1998, which opened the way to the use of imatinib, a tyrosine kinase inhibitor able to inhibit the growth of cells expressing KIT-mutant isoforms. Since then, accumulating evidence revealed the rather heterogeneous nature of GIST, implying possible different diagnostic and therapeutic approaches for each specific case, leading to the development of drugs alternative to imatinib. In this brief commentary, we graphically represent the historical growing of genotype and phenotype evidence on GIST since 1998 in its increasing complexity by building up a graph, which we have called "GISTogram", that visually conveys most of GIST-characterizing features and the probability for each of them, either alone or in combination, to be observed in a single GIST case.

Different expression of Sox9 and Runx2 between chondrosarcoma and dedifferentiated chondrosarcoma cell line

Dedifferentiated chondrosarcoma (DDCS), a highly malignant variant of chondrosarcoma (CCS), is characterized by high-grade sarcoma adjacent to low-grade chondroid tumor. Owing to its complicated composition, the histogenesis of this tumor remains controversial. Earlier, we carried out DNA microarray analysis using chondrosarcomatous tissues, and found that Sox9 and runt-related transcription factor 2 (Runx2) were differentially expressed in CCS compared with DDCS. Here, we analyzed Sox9, Runx2, Col2a1, and Col1a1 in NDCS-1 (DDCS) and SW1353 (CCS) cell lines using reverse transcriptase-polymerase chain reaction, western blot, and immunocytochemistry. The results showed high expression of Runx2 and Col1a1, and low expression of Sox9 and Col2a1 in NDCS-1 cells. In SW1353 cells, however, gene expressions were reversed. These findings provide evidence that Sox9 and Runx2 are involved in the occurrence and development of DDCS.

De novo HRAS and KRAS mutations in two siblings with short stature and neuro-cardio-facio-cutaneous features

Mutations in genes involved in Ras signalling cause Noonan syndrome and other disorders characterised by growth disturbances and variable neuro-cardio-facio-cutaneous features. We describe two sisters, 46 and 31 years old, who presented with dysmorphic features, hypotonia, feeding difficulties, retarded growth and psychomotor retardation early in life. The patients were initially diagnosed with Costello syndrome, and autosomal recessive inheritance was assumed. Remarkably, however, we identified a germline HRAS mutation (G12A) in one sister and a germline KRAS mutation (F156L) in her sibling. Both mutations had arisen de novo. The F156L mutant K-Ras protein accumulated in the active, guanosine triphosphate-bound conformation and affected downstream signalling. The patient harbouring this mutation was followed for three decades, and her cardiac hypertrophy gradually normalised. However, she developed severe epilepsy with hippocampal sclerosis and atrophy. The occurrence of distinct de novo mutations adds to variable expressivity and gonadal mosaicism as possible explanations of how an autosomal dominant disease may manifest as an apparently recessive condition.

Dedifferentiated chondrosarcoma: our clinico-pathological experience and dilemmas in 25 cases

BACKGROUND

Dedifferentiated chondrosarcoma represents a special form of the chondrosarcoma characterized by the presence of well-differentiated cartilaginous component in juxtaposition with the malignant mesenchymal tumor of high-malignancy grade.

METHODS

The study was performed on 25 tissue samples obtained by biopsy of the primary malignant bone tumors.

RESULTS

Out of the total of 25 patients, 13 were males and 12 were females. Their average age was 59.9 years (39-75). Radiological examination verified the presence of the pathological fractures in 14 patients. The skeletal distribution clearly indicates that the femur is the most frequent site of affection (in 15 patients--60%). Morphological analysis verified the presence of "precursor cartilaginous lesion" or low-grade cartilaginous component in all cases. Classification of the high-grade components was based on the immunohistochemical analyses, which evidenced MFH in 18 cases, osteosarcoma in 4, while fibrosarcoma was evidenced in 2 and rhabdomyosarcoma in 1 case. In 20 patients, out of whom 14 had existing fractures, amputation was indicated. In five patients (fracture-free), resection limb-salvage surgical intervention was performed.

CONCLUSION

The lethal outcome ensues within less than 2 years in all patients.

Dedifferentiated chondrosarcoma with leukocytosis and elevation of serum G-CSF. A case report

Background

G-CSF is known to function as a hematopoietic growth factor and it is known to be responsible for leukocytosis. G-CSF-producing tumors associated with leukocytosis include various types of malignancies.

Case presentation

We report the case of a 72-year-old man with dedifferentiated chondrosarcoma characterized by dedifferentiated components of malignant fibrous histiocytoma- or osteosarcoma-like features in addition to conventional chondrosarcoma, arising from his pelvic bone. After hemipelvectomy, when local recurrence and metastasis were identified, leukocytosis appeared and an elevated level of serum granulocyte-colony-stimulating factor (G-CSF) was also recognized. The patient died of multiple organ failure 2 months after surgery. Autopsy specimens showed that the histological specimens of the recurrence and metastasis were dedifferentiated components, without any conventional chondrosarcoma components. G-CSF was expressed only in the dedifferentiated components, not in the chondrosarcoma components, immunohistochemically.

Conclusion

This is the first report of chondrosarcoma, or any other primary bone tumor, with leukocytosis, probably stimulated by tumor-produced G-CSF from the dedifferentiated components.

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.

Mutation analyses of the NFAT1 gene in chondrosarcomas and enchondromas

Mice lacking nuclear factor of activated T cell 1 (NFAT1) showed an abnormal proliferation of chondrocytes in articular cartilage and formed an extraosseous cartilaginous mass resembling a neoplastic lesion, suggesting that the NFAT1 gene is a tumor suppressor gene in cartilaginous neoplasms. Here we performed mutation analyses of the NFAT1 gene in human cartilaginous tumors including 30 chondrosarcomas and 15 enchondromas. Reverse transcription-polymerase chain reaction (PCR) analysis revealed the expression of the NFAT1 gene in 15/15 chondrosarcomas and 12/13 enchondromas. To find subtle alterations, the genomic structure of the NFAT1 gene was determined using human genome draft sequences, and a mutation analysis was performed using the exon-by-exon PCR-single-strand conformation polymorphism method. Two heterozygous missense mutations, A1557T (His446Leu) and C2859T (Pro880Leu), were found in eight tumor samples, but the same mutation was also present in the constitutional cells of corresponding patients. The incidence of the mutant alleles in the patient and control groups showed no significant difference, suggesting that these mutations are rare single nucleotide polymorphisms unrelated with tumorigenesis. These results suggest that the NFAT1 gene is not likely to be a tumor suppressor gene in human cartilaginous tumors.