Abstract 5234: CEACAM1 expressing spheroid with a hollow beyond the invasive margin indicates the malignant potential of colorectal cancer

Abstract

Abstract BACKGROUND: Spheroid with hollow (SWH) induced by Carcinoembryonic Antigen-related Cell Adhesion Molecule 1 (CEACAM1) and inner cells apoptosis is observed in three-dimensional (3D) in vitro culture and in an in vivo mouse model. However, it is unclear whether SWH exists in clinical cancer tissue. The aim of the current study is to address which cytoplasmic domain of CEACAM1 is responsible for SWH formation, and to elucidate the existence and the implication of SWH in colorectal cancer. METHODS: To address which cytoplasmic domain of CEACAM1 is responsible for SWH formation, 3D culture was conducted to investigate lumen formation of colorectal cancer cells (LS174T and HT29) transfected with CEACAM1-4L (long cytoplasmic isoform), -4S (short cytoplasmic isoform), or shRNA for CEACAM1. Immunohistochemical analyses were conducted with CEACAM1, CEACAM1-L (long cytoplasmic isoform) and M30 (cleaved cytokeratin 18 fragment) as an apoptosis marker on clinical samples from 164 patients with colorectal cancer. The risk factors for metastases and survival were calculated using univariate and multivariate analyses. RESULTS: In 3D culture experiment, CEACAM1-L is responsible for lumen formation of colorectal cancer cells. Knock down of CEACAM1 or over-expression of CEACAM1-4S inhibited lumen formation, indicating that modulation of CEACAM1 can control SWH structure. Immunohistochemical analyses showed that CEACAM1 expressing spheroid with hollow accompanying with central cells apoptosis shown by M30 staining existed at the invasion front of colorectal cancer tissues. All of SWH was stained by CEACAM1 and CEACAM1-L. It means that SWH at the invasion front has already acquired tumor initiating property. A multivariate analysis showed that the SWH is an independent risk factor for lymph node metastasis (p=0.004) and distant metastasis (p=0.002). The SWH was also identified to be an independent prognostic factor by a Cox proportional hazards model (p=0.020). The Kaplan-Meier evaluation for the overall survival analysis showed that SWH was significantly associated with a shorter survival (p<0.0001). These results suggested that CEACAM1 expressing SWH indicates metastatic and malignant phenotype. CONCLUSIONS: CEACAM1-L expressing SWH was significantly correlated with colorectal cancer metastasis and poor survival, suggesting that the SWH can be metastatic phenotype. SWH at the invasion front of colorectal cancer can be useful for diagnosis of malignancy, and morphological control of SWH by modulation of CEACAM1 may be novel therapeutic strategy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5234. doi:10.1158/1538-7445.AM2011-5234