Optical imaging of periostin enables early endoscopic detection and characterization of esophageal cancer in mice

Abstract

Imaging strategies that detect early stage esophageal squamous cell carcinoma (ESCC) could improve clinical outcomes, when combined with endoscopic approaches. Periostin is an integrin-binding protein that is important in the tumor microenvironment. We created a fluorescent-labeled antibody that recognizes periostin and binds specifically to ESCC xenograft tumors in mice. In L2-cre;p120ctnLoxP/LoxP mice, which develop squamous cell cancers that resemble human ESCC, we visualized the probe in preneoplastic and neoplastic esophageal lesions using near-infrared fluorescent imaging with upper-gastrointestinal endoscopy. Periostin might be a biomarker of the esophageal tumor microenvironment that can be used to detect preneoplastic lesions.

FIGURE 1. Periostin is upregulated in invasive human ESCC

A. Schematic of prediction models constructed for evaluation of predicted outcomes based on gene expression signatures. B. Kaplan-Meier plots of the overall survival (OS) of the two predicted groups of patients. The differences between groups were significant, as indicated by the log-rank test. C. Comparison of relative periostin (POSTN) expression in gene expression dataset comparing invading versus non-invading EPC2-hTERT-EGFR-p53^R175H cells grown in OTC to periostin expression in gene expression dataset of matched ESCC tumors in Shanxi cohort. Error bars represent +/− SEM. *p<0.05 D. Immunoblot of POSTN (95 kDa) expression in panel of ESCC cell lines. β-actin was used as a loading control. E. Fluorescent images of periostin optical probe injected into nude mice bearing tumor xenografts of TE-11 and TT (white arrows). TT tumor xenografts were used as a negative control. Sternum is indicated by black arrowheads and bladder is indicated with black arrows. F. Quantification of fluorescent signal from the periostin optical probe detected from TE-11 and TT tumor xenografts (n=5 from each group). Bar graphs represent target-to-background ratios (TBR) +/− SEM *p<0.05. Note that background TBR=1 implies no increased probe uptake in tumor relative to background tissue.

FIGURE 2. Periostin expression is detected with increasing ESCC progression in genetic mouse model of ESCC

A. Immunoblot of periostin expression in mouse sera from three cohorts of mice at different stages of disease: control L2-cre; p120ctn^LoxP/+, L2-cre; p120ctn^LoxP/LoxP with mild dysplasia and L2-cre; p120ctn^LoxP/LoxP with severe dysplasia (n=6 mice from each group). Ponceau S staining of immunoblot was performed as loading control. B. ELISA of periostin levels present in mouse sera from the above three cohorts of mice. (n=6 mice from each cohort). Error bars represent +/− SEM *p<0.05 C. Representative white light (WL), near infra-red (NIR) and overlay images from upper GI endoscopies in mice from the above three cohorts. Color map represents range of fluorescent signal intensities (200–1100) in images. D. Quantification of fluorescent signal from periostin optical probe detected from upper GI endoscopies in mice from the above three cohorts (n=3 from each cohort). Bar graphs represent TBR +/− SEM *p<0.05 E. Histopathological analysis of representative esophagi isolated from mice from the above three cohorts in top to bottom panels. Scale bars are 100 μM.