Detection Of Aberrant Methylation Of RASSF1A Gene In Osteosarcoma And Its Relationship With Osteosarcoma’s Clinical Diagnosis

Objective:Osteosarcoma is one of the most common types in primary malignant bone tumors, it has an obvious osseous invasion by soft-tissue and a highly metastatic propensity, and it is difficult to diagnose osteosarcoma in early stage in clinical. This subject was to further discusse RASSFIA gene methylation in osteosarcoma cell lines, osteosarcoma tissue, normal bone tissue and plasma samples from the same patient, in order to further know the mechanism involved in pathogenesis of osteosarcoma and to disscuss the feasibility of the methylation status in plasma as a biomarker for clinical detection of osteosarcoma.Methods:1. Methylation-spectific PCR(MSP) was applied to determine RASSFIA methylation in osteosarcoma cell lines such as MG-63.MNNG/HOSCl、Saos-2.2. Methylation-spectific PCR(MSP) was applied to determine RASSFIA methylation in30cases of osteosarcoma tissues and plasma from the same patient,15cases of normal bone tissues and plasma from the healthy volunteers.3. The correlation between methylation of RASSFIA gene and clinicopathological features such as gender, age, tumor location, tumor differentiation and tumor distant metastasis was analyzed.The experimental results:1. RASSF1A methylation was negative in osteosarcoma cell line MG-63, but positive in osteosarcoma cell line MNNG/HOSC1and Saos-2.2. Hypermethylation of RASSF1A was present in26.7%(8/30) of the osteosarcoma plasma samples and40%(12/30) of the osteosarcoma tissues, and of the12cases of positive RASSFIA methylation,8cases were found with RASSFIA methylation both in the cancer tissues and plasma from the same patient, with a positive consistent rate of66.7%(8/12),18cases were observed with negative methylation both in the cancer tissues and plasma.3. The detection rate of RASSFIA methylation both in the normal bone tissue and plasma from healthy volunteers was0. RASSF1A methylation in osteosarcoma tissue was much higher than that in the normal tissue and the difference was significant(p<0.05), RASSF1A methylation in plasma from osteosarcoma patients was much higher than that in the normal plasma and the difference was significant(p<0.05).4. Kappa consistency check showed that methylation of RASSF1A gene in osteosarcoma tissue and plasma had consistency(Kappa value was0.133, p<0.05). The methylation of RASSF1A in plasma and cancer tissue had no obvious relationship with gender, age, tumor location(p>0.05), but had relationship with tumor differentiation and tumor distant metastasis(p<0.05).Conclusion:RASSF1A methylation in separate sources of osteosarcoma cell lines was different. RASSF1A methylation in plasma can partly represent the similar changes in cancer tissue from the same patient, and may be a promising biomarker for clinical detection of osteosarcoma.