This is further supported by recent studies that demonstrated colorectal adenocarcinomas characterized by the BRAF V600E mutation have significantly worse overall survival when compared to BRAF wild-type or KRAS mutated adenocarcinomas C646 concentration [3], [14], [15] and [16]. Additionally, SSA/Ps have been reported to be of higher risk of progression [17] and [18]. Our study attempted the further investigation of underlying molecular alterations in serrated colorectal polyps through gene expression profiling. In validation studies, we employed quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and routine immunohistochemical

techniques available in most pathology laboratories using samples from surgical resections and polypectomies. We have identified claudin-1 (CLDN1) as significantly upregulated in polyps bearing the BRAF V600E somatic mutation both on a gene expression level and a protein level, regardless of polyp type. Our results indicate that CLDN1 up-regulation occurs early in the development of SSA/P and its overexpression in a proportion of MVHP suggests a close relation between these two

lesions of the serrated pathway. Polyp samples used in microarray gene expression profiling and qRT-PCR were obtained from surgical resection specimens. The fresh resection specimens were examined and sampled in a hospital immediately after resection or in the pathology laboratory within 30 minutes of resection. Each polyp was divided into equal portions. Portions were either immediately snap-frozen in liquid nitrogen or Volasertib datasheet formalin fixed and paraffin embedded RVX-208 (FFPE). The frozen

sections selected for the study were further verified histologically before analysis. The diagnostic criteria for SSA/P and MVHP are based on published criteria relying mainly on polyp architecture [9]. The architectural features assessed included crypt branching, horizontal dilatation of basal crypt compartments, and presence of serration at the base of the crypts. Polyps were classified as SSA/P when at least two of these features were present, and only lesions with a sessile configuration and a diameter of 10 mm or more from the right colon (up to the splenic flexure) were classified as SSA/P; MVHP were obtained from the left colon and were < 5 mm in diameter. None of the polyps used in microarray gene profiling or RT-PCR contained pericryptal stromal spindle cells, had a conventional adenoma component, or had dysplasia. In addition to morphology, polyps were also characterized by BRAF and KRAS mutation analyses. No polyps that carried both the BRAF and KRAS mutations were identified. Informed consent was obtained from patients before the use of their samples, and the study was approved by the Royal Adelaide Ethics Committee (RAH Protocol No. 001201). DNA was prepared from polyp tissue macro-dissected from FFPE slides using the QIAamp DNA FFPE Tissue Kit (Qiagen, Valencia, CA).