Gene Expression Profiling of Serrated Colorectal Polyps: Identification of Genes That Differentiate Hyperplastic Polyps (HPs) from Sessile Serrated Polyps (SSPs)
David Hernandez Gonzalo, Keith K Lai, Xiuli Liu, Deepa T Patil, Ana E Bennett, John R Goldblum, Walter H Henricks, Erinn Downs-Kelly, Jeanie Na, Lisa A Rybicki, Bonnie L Shadrach, Paula Carver, Rish K Pai. Cleveland Clinic, Cleveland, OH
Background: SSPs are precursors to sporadic MSI-H colon cancers and their presence increases the risk of subsequent advanced neoplasia. Thus, distinguishing SSPs from HPs has important therapeutic implications. This distinction is difficult due to overlapping histologic features, poor orientation, mechanical artifact, and unusual location (eg, SSP located distal to splenic flexure).
Design: 110 serrated polyps were identified, randomized and independently reviewed by 7 GI pathologists. Consensus (defined as at least 6 pathologists agreeing) was achieved in 24 HPs, 21 SSPs, and 9 SSPs with dysplasia/carcinoma (SSPD). Of these consensus polyps, 6 HPs, 6 SSPs and 4 SSPDs were selected for whole genome microarray analysis in addition to 6 normal colonic biopsies (3 right and 3 left colon). RNA was isolated from paraffin-embedded tissue and expression analysis was performed using the Illumina DASL-HT assay. Raw data was analyzed using the R-limma package. Genes were defined as differentially expressed by an Fdr adjusted p value <0.05.
Results: 65 differentially expressed genes (DEGs) were identified when comparing SSPs and HPs. One DEG, Annexin A10 (ANXA10), was evaluated by immunohistochemistry on the following consensus polyps: HPs (19), SSPs (14) and SSPDs (8). Annexin A10 staining was evaluated according to intensity of nuclear staining (0-4) and percentage of nuclei staining (0-4). Staining was mostly present in upper 2/3 of the crypt. Using Wilcoxon rank sum test, staining intensity and percent positive nuclei were compared between groups.
|Polyp type||Mean percentage of positive nuclei (median)*||P-value***||Mean intensity (median)**||P-value***|
|SSP (14)||3.2 (3.5)||---||3.3 (3.5)||---|
|HP-all (19)||1.5 (1)||0.001||1.9 (2)||0.039|
|HP-left (13)||1.2 (0)||<0.001||1.5 (0)||0.014|
|HP-right (6)||2.2 (2.5)||0.1||2.7 (3.5)||0.65|
|SSPD-non dysplastic areas (8)||2.6 (3)||0.38||3.5 (4)||0.62|