The effects of neoadjuvant chemoradiation on exosomal markers (CD63 and CD9) expression in patients with locally advanced rectal adenocarcinoma.

Abstract

101 Background: Exosomes mediate intercellular communications and have pivotal roles in cancer development. CD63 and CD9 are widely accepted exosomal markers. The effect of concurrent chemoradiation on the expression of exosomal markers is unknown. Here we explored the effect of neoadjuvant concurrent chemoradiation (NCCR) on exosomal markers (CD63 and CD9) expression in patients with locally advanced rectal cancer (LARC). Methods: Between 2015 and 2018, 33 patients had LARC treated with NCCR and had pre NCCR biopsy and post NCCR resected rectum examined for exosomal markers expression using immunohistochemistry. Two pathologists independently scored CD63 and CD9 staining in the tumor. Staining intensity was graded from 1-3. Staining percentage was estimated in 10% increments. Mean quick-score (Q-score) was calculated (intensity x percentage). Un-Paired t test was used for statistical analysis. Results: In our cohort, median age was 59 years. Males represented 79% of the patients. Caucasians, African American and other ethnic groups represented 70%, 27% and 3% respectively.The mean tumor CD63 score in pre NCCR biopsy vs post NCCR resected rectum was 106 vs 165 (p = 0.0022). The mean tumor CD9 score in pre NCCR biopsy vs post NCCR resected rectum was 136 vs 215 (p < 0.0001). The exosomal markers expression in the adjacent normal mucosa (ANM) from pre NCCR biopsy and post NCCR resected rectum was only performed in16 out of 33 patients (due to ANM tissue availability). The mean ANM CD63 score in pre NCCR biopsy vs post NCCR resected rectum was 166 vs 183 (p = 0.37). The mean ANM CD9 score in pre NCCR biopsy vs post NCCR resected rectum was 104 vs 145 (p = 0.0897). Conclusions: In patients with LARC, the expression of exosomal markers (CD63 and CD9) increased after treatment with NCCR. Our results show that the expression of CD63 and CD9 is relatively higher in rectal cancer specimens treated with NCCR and thus suggest a possible role of these exosomes in adaptive response to NCCR. Further follow-up and laboratory studies are required to precisely understand the underlying mechanism(s).