Background: Tumors grow in accordance with immunoediting. If we can see the changes of immune characteristics in the microenvironment during tumor growth, we can have much information of the mechanism of immunoediting. Peritoneal tumor cells from colorectal cancers are mostly derived from the shedding of tumor cells exposed on the visceral peritoneum. After the surgical removal of the primary tumors of which cells are exposed on the visceral peritoneum (T4 stage) but without macroscopic tumor seedings in the peritoneal cavity, some patients experience peritoneal recurrence but others do not. This implies that in the patients with future peritoneal recurrences the microscopic tumor cells in the peritoneal cavity have already been immunoedited. In addition, ascites and peritoneal immune cells are components of tumor microenvironment during peritoneal tumor growth if the peritoneal cavity is not contaminated by microorganisms by bowel perforation. And ascites and peritoneal cells are appropriate materials for immediate analysis after collection. Therefore, if we establish peritoneal immune characteristics of each T4 patient and compare those between the recurred and non-recurred patients in the peritoneal cavity afterwards, we can hold the clues of immunoediting during the peritoneal tumor growth. In this study we tested this autologous human growing tumor model for the relevance of research subject for cancer-associated immune response, as a pilot study.
Method: Ascites and peritoneal cells were collected during the operation of colon cancer patients. If blood were mixed during the collection, the ascites and cells were discarded. The patients, whose ascites and peritoneal cells had been harvested, were classified into four groups (PC stages) according to the progression of peritoneal tumor growth on the basis of pathological report. SE-(serosa exposure negative; no tumor cells in peritoneal cavity) is a group of patients without exposure of cancer cells to peritoneal cavity (T3 or lower T stage). SE+(serosa exposure positive; microscopic tumor cells in peritoneal cavity) is a group of patients of T4 lesion without peritoneal seedings. l-PC represents localized peritoneal seedings which could be removed entirely during surgery. g-PC is a group of generalized peritoneal seeding. We performed ELISA and flow cytometry analysis as well as immune cell activation.
Result: Of the 10 cytokines assayed in ascites, IL10, IL6 and TGF-beta increased according to the tumor progression in the peritoneal cavity, while the other cytokines (IL2, IL4, IL5, IL12, IL17, TNF and IFN-gamma) did not show any changes. Of the 42 SE+ patients, eleven experienced peritoneal recurrences. Mean IL10 (42 vs 24 pg/mL) and IL6 (2,092 vs 4472 pg/mL) levels of patients with peritoneal recurrence were higher than those without recurrence although we could not have significance (P = 0.113 and 0.180 each, Mann-Whitney U test). Activation of peritoneal cells by LPS increased IL6 as well as IL10 while activation by antiCD3 and antiCD28 did not. Intracellular IL10 was stained in T cells while IL6 in CD14 cells after LPS stimulation. Moreover, although ascitic IL6 increased up to tens of thousands pg/mL in g-PC patients, the blood level stayed at tens pg/mL. This means the ascites and peritoneal immune cells belong to a microenvironment which is seldom reflected in peripheral blood.
Conclusion: This model showed the possibility of relevance to explore cancer-associated immune response in the tumor microenvironment during tumor growth in colorectal cancer. It is expected that further studies will provide much information of the mechanism of suppression of anti-tumor immune response. And the results derived from this model can help to extend understandings of immunoediting in primary tumors, metastatic tumors and, further, in other cancers.
Citation Format: Seung Chul Heo, Sang Mok Lee, Beonghoon Sohn, Ji-Eun Kim, Rumi Shin. Autologous human growing tumor model and its immunological relevance for cancer immunology research [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B140.
- ©2016 American Association for Cancer Research.