TGF-β signalling and PEG10 are mutually exclusive and inhibitory in chondrosarcoma cells

Abstract

Histological distinction between enchondroma and chondrosarcoma is difficult because of a lack of definitive biomarkers. Here, we found highly active transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) signalling in human chondrosarcomas compared with enchondromas by immunohistochemistry of phosphorylated SMAD3 and SMAD1/5. In contrast, the chondrogenic master regulator SOX9 was dramatically down-regulated in grade 1 chondrosarcoma. Paternally expressed gene 10 (PEG10) was identified by microarray analysis as a gene overexpressed in chondrosarcoma SW1353 and Hs 819.T cells compared with C28/I2 normal chondrocytes, while TGF-β1 treatment, mimicking higher grade tumour conditions, suppressed PEG10 expression. Enchondroma samples exhibited stronger expression of PEG10 compared with chondrosarcomas, suggesting a negative association of PEG10 with malignant cartilage tumours. In chondrosarcoma cell lines, application of the TGF-β signalling inhibitor, SB431542, increased the protein level of PEG10. Reporter assays revealed that PEG10 repressed TGF-β and BMP signalling, which are both SMAD pathways, whereas PEG10 knockdown increased the level of phosphorylated SMAD3 and SMAD1/5/9. Our results indicate that mutually exclusive expression of PEG10 and phosphorylated SMADs in combination with differentially expressed SOX9 is an index to distinguish between enchondroma and chondrosarcoma, while PEG10 and TGF-β signalling are mutually inhibitory in chondrosarcoma cells.

PEG10 as an oncogene: expression regulatory mechanisms and role in tumor progression

“…2 a, PEG10 is relatively highly expressed in placenta, adrenal, ovary, testis and brain, but the expression levels are pretty low in other tissues, which are consistent with the previous literature [ 1 , 7 – 9 ]. As shown in Table 1 , several studies have reported PEG10 is positively expressed in a variety of cancers such as hepatocellular carcinoma (HCC) [ 9 , 16 – 19 ], pancreatic carcinoma [ 20 ], breast cancer [ 10 ], prostate cancer [ 10 ], gallbladder carcinoma [ 21 ], thyroid cancer [ 22 ], oral squamous cell carcinoma [ 23 ], colon cancer [ 24 ], enchondromas [ 25 ] and B-cell chronic lymphocytic leukemia (B-CLL) [ 26 ]. Worth noting was that the amplification of PEG10 gene copy numbers detected in HCC also contributed to PEG10 overexpression [ 17 , 27 – 29 ].…”

“…In HCC, PEG10 was increased after treating HepG2 cells with TGF-β1 [ 44 ]. However, the mutual inhibition effect of PEG10 and TGF-β signaling was found in chondrosarcoma and enchondroma [ 25 ]. Shinohara et al proposed that TGF-β might inhibit PEG10 expression through the downregulation of c-MYC [ 10 , 25 , 35 ].…”

Biomarkers of chondrosarcoma

“… 41 In other report, SOX9 is dramatically decreased in grade 1 chondrosarcoma. 42 Taken these, SOX9 expression level may not be used as a prognostic marker, but can be used as a therapeutic target.…”

“… 43 44 BMPRs and runt-related transcription factor 2 (RUNX2) signalling in bone development and carcinogenesis are well known but not in chondrogenesis. Shinohara et al 42 have revealed that phosphorylated Smad3 and Smad1/5 is increased in chondrosarcoma, and Yang et al 45 have shown that BMPR2 and RUNX2 expression is correlated with poor prognosis in 57 patients with various grades chondrosarcoma. 45 BMPR2 downstream Smad1/5 signal promotes tumour growth of chondrosarcoma cells in vivo.…”

“…Loss of PEG10 suppression causes the increase of phosphorylated Smad3 and Smad1/5. 42 Taken together, BMPR2 and RUNX2 can be used as potential markers for prognosis.…”