KISS1 expression in osteosarcoma: high in chinese clinical cases, but lower in cell lines. Osteosarcoma is the most common primary bone malignancy with a notorious feature of high metastasis. KISS1 has been identified as a putative human metastasis suppressor gene in numerous types of cancer. This study was aimed to evaluate the relationship between expression of KISS1 and invasion ability in osteosarcoma cell lines, and the relationships between KISS1 expression levels and prognosis of clinical cases.Expression levels of KISS1 in 3 types of osteosarcoma cell lines (MG-63, Saos-2 and U-2 OS) and a normal osteoblast cell line (hF-OB 1.19) were examined using semi-quantitative RT-PCR and immunochemistry staining. Transwell assays were used to detect the cell invasion ability. The osteosarcoma cell lines and specimen sections of osteosarcoma together with control were immuno-stained with KISS1 antibody. The relationship between the clinical data and the expression of KISS1 was evaluated.KISS1 mRNA expression was moderate in U-2 OS, weak in Saos-2 and lost in MG-63. Transwell assays displayed a gradually increased aggressive phenomenon in osteosarcoma cell lines U-2 OS, Saos-2 and MG-63. However, a contrary conclusion was obtained with clinical specimen, a higher positive rate of KISS1 expression being displayed in osteosarcoma patients, especially in metastastic cases, compared to the benign osteochondroma patients. Furthermore, significant earlier distant metastasis was observed in KISS1 positive than negative cases.KISS1 expression levels were found to be decreased with the increasing aggressive ability in osteosarcoma cell lines. However, expression of KISS1 positively correlated with metastasis in osteosarcoma patients.