Abstract: Expression of TRAIL and Ki-67 in Human Osteosarcoma and Its Correlation with Apoptosisand Proliferation of Tumor CellsWenjuan FU1, Qijia LI2, Hongquan GAN2, Fangchu SUN1, Lianli WANG1Correspondence to: Qijia LI, E-mail: qjl1222@hotmail.com1Department of Radio-chemotherapy, Tangshan People's Hospital, Tangshan 063000, China2Experimental Center, North China Coal Medical College,Tangshan 063000, ChinaThis work was supported by Hebei Provincial Bureau of Personnel Funds for Scientific Activities of Returned Overseas Stu-dent (No. 2009-11)Abstract Objective: To investigate the expression and distribution of TRAIL and Ki-67 proteins, as well as the relation-ship between these proteins and the proliferation and apoptosis of human osteosarcoma cells. Methods: Immunohistochem-istry was used to evaluate the distribution of TRAIL and Ki-67 proteins in groups of patients with either osteosarcoma or os-teochondroma. Apoptosis was detected by In Situ Terminal Deoxy-nucleotide Transferase Labeling (TUNEL), and apoptoticcells could be seen when FITC labeling was examined with confocal laser scanning microscopy. The proliferation indexand apoptosis index were then calculated. Results: The positive expression of TRAIL protein in osteosarcoma was signifi-cantly lower than that in osteochondroma ( t = -5.51, P < 0.05), while the positive expression of Ki-67 protein was signifi-cantly higher in the osteosarcoma group than in the osteochondroma group ( t = 17.69, P < 0.05). There was a significantnegative correlation between TRAIL and Ki-67 protein expression in osteosarcoma ( r = -0.8444, P < 0.01). The apoptosisindex (AI) was lower in the osteosarcoma group than in the osteochondroma group ( P < 0.01). The proliferation index (PI)was higher in the osteosarcoma group than in the osteochondroma group ( P < 0.01). There was a negative correlation be-tween Ki-67 protein expression and the AI ( r = -0.5622, P < 0.01). There was a positive correlation between TRAIL proteinexpression and the AI ( r = 0.6350, P < 0.01) and a negative correlation between TRAIL protein expression and the PI (r = -0.5530, P < 0.01). Conclusion: TRAIL protein is important in inducing apoptosis of osteosarcoma cells and it takes partin the process of cellular apoptosis. Ki-67 protein plays an important role in the proliferation and apoptosis of osteosarco-ma. The significant overexpression of Ki-67 and underexpression of TRAIL protein in osteosarcoma may be closely relatedto the occurrence and development of osteosarcoma. Lowering Ki-67 overexpression and raising TRAIL underexpressionmay increase apoptosis in osteosarcoma cells.Key words Osteosarcoma; TRAIL; Ki-67; Apoptosis