Microsatellite instability detection using BAT-25 and BAT-26 by Real Time PCR and HPLC in colorectal cancer

Colorectal Cancer (CRC) is the third common cancer in the world. One of the pathways in colorectal tumor genesis is Microsatellite Instability (MSI+). MSI is detected in about 15% of all colorectal cancers. Colorectal tumors with MSI have dis-tinctive features compared with Microsatellite Stable (MSS) tumors. Due to the high percentage of MSI+ in patients with CRC in Iran، screening of this type of CRC is im-perative. In current study، two markers (BAT-26 and BAT-25) were used to determine an appropriate screening technique with high sensitivity and specificity to diagnose MSI status in patients with CRC. Allelic variation in two markers (BAT-26 and BAT-25) was analyzed in tis-sues and sera of 44 normal volunteers and tumor and matched normal mucosal tissues as well as sera of 44 patients with sporadic colorectal cancer by Real Time PCR (Hy-bridization probe) and High-Performance Liquid Chromatography (HPLC) techniques. The sensitivity and specificity of Real Time PCR and HPLC compared with sequencing as gold standard. The data were statistically analyzed using Student’s t-test and 2 or fisher exact test، where applicable with (P<0. 05). Receiver-operating-characteristic (ROC) curves were used to evaluate the sensitivity and specificity. The sensitivity and specificity of BAT-26 with Real Time PCR method (Hy-bridization probe) were 100% in comparison with gold standard method. Whereas the sensitivity and specificity of BAT-26 and BAT-25 with HPLC were 83%، 100% and 50%، 97%، respectively. Neither HPLC nor Real time PCR could detect circulating DNA with MSI property in sera. The sensitivity and specificity of real time PCR in MSI detection is the same as sequencing method and more than HPLC. BAT-26 marker is more sensitive than BAT-25 and MSI detection with Real time PCR could be considered as an accu-rate method to diagnose MSI in CRC tissues not sera.