Exosomal markers (CD63 and CD9) expression using immunohistochemistry (IHC) in patients with right-sided and left-sided colon cancer.

Abstract

e15119 Background: Embryologically, the right colon (cecum, ascending colon, hepatic flexure and proximal two-thirds of the transverse colon) is derived from the midgut, whereas the left colon (sigmoid colon, descending colon, splenic flexure and distal third of the transverse colon) is derived from the hindgut. There are clinical, pathological and molecular differences between patients with right-sided colon cancer (RSCC) and left-sided colon cancer (LSCC). Exosomes mediate intercellular communications and interactions and have pivotal roles in cancer behavior. CD63 and CD9 are widely accepted exosomal markers. Here we explored CD63 and CD9 expression using immunohistochemistry (IHC) in patients with RSCC and LSCC. Methods: Between 2015 and 2018, 63 patients underwent colon surgical resection for whom we had available tissues for CD63 and CD9 IHC staining. Two pathologists independently scored CD63 and CD9 expression in the tumor and adjacent normal mucosa (ANM). Staining intensity was graded from 1-3. Staining percentage was estimated in 10% increments. Mean quick-score (Q-score) was calculated (intensity x percentage). Unpaired t test was used for statistical analysis. Results: Median age was 64 (range 33-78). Females represented 60% of our cohort. Caucasians, African Americans and other Ethnicities represented 55%, 40% and 5% respectively. The sidedness was designated as RSCC in 52% and as LSCC in 48%. The ANM and Tumor CD63 Q scores were 225 vs 191 (p = 0.009) in RSCC and 224 vs 154 (p = 0.0001) in LSCC respectively. The ANM and Tumor CD9 Q scores are 134 vs 152 (p = 0.142) in RSCC and 135 vs 154 (p = 0.137) in LSCC respectively. In patients with RSCC and LSCC, the mean Tumor CD63 Q score is 191 vs 154 (p = 0.024), while the mean ANM CD63 Q score is 225 vs 224 (p = 0.920). The mean Tumor CD9 Q score is 152 and 154 (p = 0.883) and the mean ANM CD9 Q score is 134 vs 135 (p = 0.926). Conclusions: In our cohort of patients with RSCC and LSCC, the exosomal marker CD63 expression is lower in the tumor compared to the ANM. While ANM CD63 expression was similar between RSCC and LSCC, tumor CD63 expression was higher in RSCC compared to LSCC. The exosomal marker CD9 was not found to have significant differential expression between ANM and tumor and between RSCC and LSCC. To our knowledge, this is the first study to explore exosomal markers expression using IHC in patients with RSCC and LSCC.