Chordoma and chondrosarcoma gene profile: implications for immunotherapy

Abstract

Chordoma and chondrosarcoma are malignant bone tumors characterized by the abundant production of extracellular matrix. The resistance of these tumors to conventional therapeutic modalities has prompted us to delineate the gene expression profile of these two tumor types, with the expectation to identify potential molecular therapeutic targets. Furthermore the transcriptional profile of chordomas and chrondrosarcomas was compared to a wide variety of sarcomas as well as to that of normal tissues of similar lineage, to determine whether they express unique gene signatures among other tumors of mesenchymal origin, and to identify changes associated with malignant transformation. A HG-U133A Affymetrix Chip platform was used to determine the gene expression signature in 6 chordoma and 14 chondrosarcoma lesions. Validation of selected genes was performed by qPCR and immunohistochemistry (IHC) on an extended subset of tumors. By unsupervised clustering, chordoma and chondrosarcoma tumors grouped together in a genomic cluster distinct from that of other sarcoma types. They shared overexpression of many extracellular matrix genes including aggrecan, type II & X collagen, fibronectin, matrillin 3, high molecular weight-melanoma associated antigen (HMW-MAA), matrix metalloproteinase MMP-9, and MMP-19. In contrast, T Brachyury and CD24 were selectively expressed in chordomas, as were Keratin 8,13,15,18 and 19. Chondrosarcomas are distinguished by high expression of type IX and XI collagen. Because of its potential usefulness as a target for immunotherapy, the expression of HMW-MAA was analyzed by IHC and was detected in 62% of chordomas and 48% of chondrosarcomas, respectively. Furthermore, western blotting analysis showed that HMW-MAA synthesized by chordoma cell lines has a structure similar to that of the antigen synthesized by melanoma cells. In conclusion, chordomas and chondrosarcomas share a similar gene expression profile of up-regulated extracellular matrix genes. HMW-MAA represents a potential useful target to apply immunotherapy to these tumors.

Figures

Fig. 1

Unsupervised cluster analysis of chondrosarcoma (red), chordoma (green) and soft tissue sarcoma (blue). Chondrosarcoma and chordoma samples form a separate genomic group, readily delineated from soft tissue sarcoma

Fig. 2

This Venn diagram demonstrates genes that show >2-fold change in chordoma (orange circle) and chondrosarcoma (yellow circle) relative to soft tissue sarcomas (white circle). The list on the left demonstrates selected genes that are up-regulated in chordoma relative to soft tissue sarcoma (STS). The list on the right demonstrates selected genes that are up-regulated in chondrosarcoma. The three columns at the top represent selected genes that are up-regulated in both chordoma and chondrosarcoma relative to soft tissue sarcoma

Fig. 3

a Hematoxylin and eosin staining of a chondrosarcoma lesion demonstrating hyaline matrix (H&E, ×200); b Hematoxylin and eosin staining of a chordoma lesion with characteristic mucinous matrix and physaliferous cells (H&E, ×200); c Immunohistochemical staining of a chondrosarcoma sample with HMW-MAA specific mAb demonstrating strong and diffuuse cytoplasmic positivity (×200). d Immunohistochemical staining of a chordoma with HMW-MAA specific mAb demonstrating strong cytoplasmic reactivity (×200)

Fig. 4

Flow cytometric analysis of chondrosarcoma and chordoma cell lines stained with the HMW-MAA-specific mAb 225.28. The irrelevant mouse anti-idiotypic mAb MK2-23 was used as a specificity control