Clinico-pathological significance of exosome marker CD63 expression on cancer cells and stromal cells in gastric cancer

Abstract

Background: It has been reported that CD63, an exosome marker, is expressed in solid cancer tissues. However, its significance in patients with gastric cancer has not been clarified. Exosomes derived from cancer cells and stromal cells might play an important role in the intracellular communications involved in the development of carcinoma. This study aimed to clarify the relationship between CD63 expression in cancer cells and stromal cells and clinical-pathologic factors.

Methods: A total of 595 gastric cancer patients were enrolled in this study. CD63 expression in cancer cells and stromal cells was analyzed by immunohistochemistry. The correlations between CD63 expression and several clinicopathological factors were investigated.

Results: CD63 expression was mainly observed on the cell membranes of cancer cells, and in the cytoplasm of stromal cells. Of 595 patients, 247 cases had CD63-positive cancer cells, and 107 cases had CD63-positive stromal cells. Cases with CD63-positive cancer cells were significantly correlated with scirrhous-type gastric cancer, tumor depth, lymph node metastasis, lymphatic invasion, and tumor size. Cases with CD63-positive stromal cells were significantly correlated with age (≥65), tumor depth (T3-4), lymphatic invasion, and tumor size (≥ 5 cm). The 5-year survival rate was significantly lower (p<0.001) in patients with CD63-positive than CD63-negative tumors. Multivariate analysis showed that CD63 expression in cancer cells was a significant independent prognostic factor in patients with gastric cancer.

Conclusion: CD63 might be a prognostic marker for patients with gastric cancer. CD63-positive exosomes might be associated with the interaction between stromal cells and cancer cells.

Fig 1. CD63 expression depending on the intensity of the staining.

(A) Representative pictures of CD63 expression on cancer cells depending on the intensity of the staining. CD63 was mainly expressed on the cell membrane of gastric cancer cells, with a smaller amount in the cytoplasm. Pictures of score 0 and 1 are from patients with early gastric cancer, and both are well differentiated tubular adenocarcinoma. Picture of score 2+ and 3+ are from patients with advanced gastric cancer, and histologic type of score 2+ is well differentiated tubular adenocarcinoma, while histologic type of score 3+ is poorly differentiated adenocarcinoma. (B) Representative pictures of CD63 expression on stromal cells depending on the intensity of the staining. CD63 expression was mainly observed in the cytoplasm of stromal cells. Pictures of score 0 are from patients with early gastric cancer, and histologic type is well differentiated tubular adenocarcinoma. Pictures of score 1+ are from patients with advanced gastric cancer, and histologic type is poorly differentiated adenocarcinoma. Pictures of score 2+ are from patients with advanced gastric cancer, and histologic type is well differentiated tubular adenocarcinoma. Pictures of score 3+ are from patients with advanced gastric cancer, and histologic type is moderately differentiated tubular adenocarcinoma.

Fig 2. Survival of patients with gastric cancer.

(A) Survival of gastric cancer patients with CD63 expression in cancer cells. The Kaplan–Meier survival curve indicates that the OS of patients with CD63-positive cancer cells was significantly worse than that of patients with CD63-negative expression (p<0.0001). Among patients with stage III and stage IV disease, the OS was significantly worse in those with CD63-positive cancer cells than those with CD63-negative expression. (B) The OS of patients with CD63-positive expression in stromal cells was not significantly different from that of patients with CD63-negative expression. (C) The OS of patients between four groups; both tumor and stroma positive, only tumor positive, only stroma positive, and both tumor and stroma negative.