Screening for the FIG-ROS1 fusion in biliary tract carcinomas by nested PCR

ROS1 rearrangements have been detected in a variety of tumors and are considered as suitable targets of anticancer therapies. We developed a new, quick, specific, and sensitive PCR test to screen for the FIG‐ROS1 fusion and applied it to a series of Italian patients with bile duct carcinoma (BTC). Formalin‐fixed, paraffin‐embedded tissues, derived from 65 Italian BTC patients, and six cell lines were analyzed by nested PCR to investigate the prevalence of a previously reported FIG‐ROS1 fusion. The specificity and sensitivity of nested PCR were investigated in FIG‐ROS1 positive U118MG cells in reconstitution experiments with peripheral blood mononuclear cells. We found that six out of 65 (9%) BTC patients were positive for the FIG‐ROS1 fusion, comprising two out of 14 (14%) gallbladder carcinoma (GBC) patients and four out of 25 (16%) extrahepatic cholangiocarcinoma (ECC) patients. None of the 26 intrahepatic cholangiocarcinoma cases harbored the FIG‐ROS1 fusion. All the cell lines were negative for this variant. In conclusion, 14–16% of GBC and ECC were positive for FIG‐ROS1. This may have clinical implications, since these patients will potentially benefit from the treatment with specific ROS1 inhibitors. © 2014 Wiley Periodicals, Inc.