Characterization Of SOX4 In Chondrosarcoma

[ Background and Objective] Chondrosarcoma is a heterogeneous and malignant primary bone tumor notoriously resistant to radiotherapy and chemotherapy. With surgery being the sole treatment, this local recurrence and unresectable disease inevitably occurred with poor prognosis. Its most common subtype is the conventional central chondrosarcoma. A majority of chondrosarcoma are of low histologic grade, which can however progress to high-grade chondrosarcomas. Therefore, novel prognostic biomarkers and therapeutic approaches need to be identified for chondrosarcoma management.The sex-determining region Y (SRY)-related HMG box (SOX) gene family members, characterized by an HMG DNA-binding domain, have been implicated in various developmental processes including chondrogenesis, such as SOX5, SOX6 and SOX9. Intriguingly, Sekiya et al. showed that SOX4 has been expressed much earlier than SOX5, SOX6 and SOX9, occurring in early chondrogenesis. Meanwhile, Reppe et al. demonstrated that SOX4 was predominantly expressed in the mineralizing cartilage zone of embryonic growth plate. Collectively, these studies suggest that SOX4 played a critical role during chondrogenesis. Besides functioning as transcriptional factors, its overexpression has been detected in many human cancers that could promote cancer progression including, hepatocellular carcinoma, lung cancer, bladder carcinoma and prostate cancer. Furthermore, genome-wide promoter analyses indicated that SOX4 cooperated with several chondrosarcoma genesis transcription factors, such as c-MYC, E2F1 and E2F4, suggesting a potential relevance between SOX4 and chondrosarcoma development. However, so far no study has been conducted on the expression and activity of SOX4 in human chondrosarcoma.MicroRNAs (miRNAs) are a cluster of non-coding, single-stranded and small regulatory RNA molecules of approximately 22 nucleotides in length. The miRNAs mediate translational repression by targeting complementary sites on their 3’UTR of specific messenger RNAs (mRNAs). MiRNA dysregulation serves vital oncogenic or tumor-suppressive functions in carcinogenesis, including chondrosarcoma. Although preliminarily, previous studies have proposed that microRNA-30a (miR-30a) has an important role in cancer development including endometrioid endometrial carcinoma, hepatocellular carcinoma, and chronic myelogenous leukemia. Nevertheless, the contribution of miR-30a to chondrosarcoma progression is unknown. Of note, emerging data on miRNA mechanisms provide novel insight into how SOX4 participate in cancer progression, including miR-129, miR-335, and miR-93. However the exact molecular mechanisms underlying SOX4 overexpression in chondrosarcoma is still not understood.In the current study, this thesis will study from the following three parts. The first is the characterization of SOX4 overexpression in chondrosarcoma, the second is SOX4 molecular characteristics in chondrosarcoma, and the other is the mechanism of SOX4 overexpression in chondrosarcoma.[Materials and methods] Two tissue microarrays (TMAs) were constructed from 107 chondrosarcoma and 59 chondroma patients. The expression of SOX4, c-MYC and P53 as well as Ki67 were detected by immunohistochemistry. Real-time PCR and Western Blotting were used to study transcript and protein expression levels. Cell functions were evaluated by transfection, MTS, Transwell and wound healing assays. Luciferase reporter assay was utilized to examine SOX4 3’UTR binding sites with miR-30a.[Results analysis] SOX4 was remarkably overexpressed in chondrosarcoma compared with chondroma (P=0.003). Its overexpression was significantly associated with the histological grade (P<0.001) and the presence of recurrence (P=0.041). In addition, SOX4 overexpression was notably correlated with the positive expression of c-MYC (P=0.011) and P53 (P=0.029) as well as high Ki67 labeling index (LI) (F 0.001) in our cohort. Intriguingly, we found that SOX4 was an unfavorable independent prognostic factor for chondrosarcoma patients with low histological grade. Functionally, SOX4 silencing in SW1353 significantly suppressed its proliferation, migration and invasion, suggesting an oncogenic role of SOX4 in chondrosarcoma cells. With the continuous studies on miRNAs mechanism, we firstly identified miR-30a as a tumor suppressor directly targeted SOX4 in chondrosarcoma cells. Concomitantly, the miR-30a expression was negatively correlated with SOX4 expression in chondrosarcoma tissues.[ Conclusion ] To the best of our knowledge, we have discovered the oncogenic role of SOX4 in chondrosarcoma for the first time. Moreover, we found that SOX4 was regulated by miR-30a in SW1353. Intriguingly, SOX4 overexpression may serve as a prognostic marker for patients with low histological grade chondrosarcoma.