Apolipoprotein E is a predictive marker for assessing non-small cell lung cancer patients with lymph node metastasis

Background: Apolipoprotein E (APOE) modulates lipid homeostasis in the systemic circulation and induces inflammatory immune responses in the tumor microenvironment. We evaluated APOE expression in order to assess tumor progression in non-small cell lung cancer (NSCLC). Methods: Immunohistochemical staining for APOE was performed on tissue microarray blocks from 148 patients who had undergone surgery for NSCLC. The staining intensity and the proportion of APOE-positive tumor cells (based on distinct membranous and cytoplasmic staining) were scored. The relationships between APOE expression and clinical (age, sex, and smoking history) and pathological (TNM stage and histological type) factors were evaluated. Results: Positive APOE staining was observed in 93 (64.6%) patients. APOE expression patterns differed among NSCLC histological types (p-value = 0.016). Negative APOE expression was significantly associated with lymph node metastasis in NSCLC (p-value = 0.040). Both cases of N2 (stage IIIA) disease showed negative APOE expression. Conclusions: APOE is a useful marker for assessing NSCLC patients with lymph node metastasis.