Combination of circulating CXCR4 and Bmi-1 mRNA in plasma: A potential novel tumor marker for gastric cancer - Xu, Wenrong; Zhou, Hongxing; Qian, Hui; Bu, Xuefeng; Chen, Deyu; Gu, Hongbing; Zhu, Wei; Yan, Yongmin; Mao, Fei (Molecular medicine reports, 2009)