Abstract P4-05-12: Kinetics of endocan in the peripheral blood before and after the resection of primary breast tumors
Authors: Daiki Kentaro , Kanada Yoko , Nagata Aya , Nakamura Seigo , Kato Yoshinori 
Published: March 2022

Abstract
Objectives: This study aims to investigate whether endocan levels in the peripheral blood change after the removal of primary breast tumors and allow predicting postoperative prognosis for breast cancer. Significance: An early prediction of postoperative recurrence and metastases with liquid biopsy will lead to better management and quality of life of breast cancer patients. Background: Cancer recurrence comes down to a poor prognosis in breast cancer patients. Although removal of primary breast cancer can achieve a successful outcome, metastasis and local recurrence remain a critical clinical problem in later years. Although the overall survival of breast cancer patients varies among molecular subtypes, the individual patients have different prognostic outcomes; some patients relapse within a few months, and others have not seen any recurrence for several years. Our previous study indicated that endocan had the potential to be a prognostic biomarker for triple-negative breast cancer. It is critical to show changes in endocan levels in the peripheral blood after the surgical excision of the primary tumor, which, in turn, will corroborate our hypothesis that plasma endocan is a beneficial biomarker for a postoperative prognosis for breast cancer patients. We included all the breast cancer subtypes in this study as the information on endocan levels in the peripheral blood from breast cancer patients has been limited thus far. Methods: To detect metastatic recurrence of breast cancer cells noninvasively, MDA-MB-231BR was transfected with the mVenus-Akaluc gene. MDA-MB-231BR spontaneously overexpresses the ESM1 gene. MDA-MB-231BR/mVenus-Akaluc was inoculated into the mammary fat pad of female athymic nu/nu mice and NSG mice. Once tumors top 200 mm3, they were surgically removed. Metastatic recurrence was visualized by the IVIS imager. Blood was withdrawn from the tail of each mouse before and after the resection of the primary tumors in a timely manner, and plasma samples were stored at -80°C until usage. Endocan in plasma samples was quantitated with a commercial ELISA kit. Tumor burden was estimated from luminescence signals of images obtained by IVIS. We obtained IRB approval from both institutions for the following research. Blood samples were collected from breast cancer patients who had given informed consent at the Breast Cancer, Showa University Hospital, and the plasma samples have been stored at -80°C until usage. Endocan in plasma sample was determined with a commercial ELISA kit. Results and discussion: Before removing primary breast tumors, the median endocan level in plasma was 0.73 ng/mL (range, 0.38-1.54 ng/mL) in nude mice. After the removal, endocan remained below the detection limits even though small metastases were detected by IVIS imager at later time points. These data indicate that loss of primary tumors results in an out-of-detection range in endocan levels in the blood. In contrast, NSG mice displayed inconsistent results: out of eight mice, three mice showed a decrease in endocan, three had an increase in endocan, and two had no change three days postoperatively. IVIS images of NSG mice indicated that distant metastases were already detected even when some mice underwent tumor resection. In NSG mice, the occurrence of tumor metastases was much earlier, and metastatic tumor burdens were much more significant than in nude mice, which might lead to a different outcome. Endocan levels in plasma from breast cancer patients at the postoperative period were not always dropped, which was similar to the results obtained from NSG mice. The rationale behind the inconsistent kinetics of endocan remains to be clarified. Conclusion: Our results from NSG mice and clinical data in patients’ plasma may have more relevance to prognostic outcomes in breast cancer patients.
Citation Format: Kentaro Daiki, Yoko Kanada, Aya Nagata, Seigo Nakamura, Yoshinori Kato. Kinetics of endocan in the peripheral blood before and after the resection of primary breast tumors [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-05-12.