Background: Peroxisome proliferator-activated receptor gamma (PPAR gamma) induces apoptosis by ligand stimulation in various tumor cell lines. In esophageal cancer cell lines, PPAR gamma activation also has suppressed the proliferation.
Methods: In 55 primary esophageal squamous cell carcinomas (ESCCs) we examined the correlation between the expression of PPAR gamma mRNA with prognosis of esophageal cancer patients. The expression of PPAR gamma mRNA was quantified by real-time reverse transcription polymerase chain reaction using LightCycler. Immunohistochemistry was used to study the expression of PPAR gamma protein.
Results: The expression of PPAR gamma mRNA was significantly decreased in esophageal cancer cells compared with normal esophageal mucosa (P = 0.0084). Among the clinical factors, PPAR gamma mRNA expression was lower in the tumors with extensive lymph node metastasis (n4) than those with less extensive lymph node metastasis (n0-3) (P = 0.0059). Patients with low PPAR gamma mRNA expression had significantly shorter postoperative survival time than those with high PPAR gamma mRNA expression (P = 0.0191). In immunohistochemistry, PPAR gamma protein was expressed in the nuclei of cells in some cases and expressed in the nuclei and cytoplasm in others. The expression of PPAR gamma protein is decreased in esophageal cancer tissue compared with normal esophageal squamous epithelium. However, we could not deduce the apparent relation for the expression between PPAR gamma mRNA and PPAR gamma proteins in immunohistochemistry (P = 0.284).
Conclusions: In esophageal cancer tissues, the expression of PPAR gamma was decreased compared with normal esophageal epithelium. The mRNA expression level of PPAR gamma may be a marker of prognosis after operation in esophageal cancer patients.