DDAH1 and neoplasm of esophagus: Quantitative (real-time) polymerase chain reaction (PCR) with SYBR Green chemistry was used to determine the relative expression level of ARG1 and ARG2, DDAH1 and DDAH2, NOS2, ODC1, and PRMT1 and PRMT5 in 40 patient-matched samples from esophageal tumors and adjacent, macroscopically normal mucosa.