Objective: To determine the expression of nucleostemin (NS), epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) mRNA in human esophageal squamous cell carcinoma (ESCC) tissues and their association in a human ESCC cell line.
Methods: The expression of NS, EGF and EGFR mRNA was determined in paired normal esophageal and ESCC tissues of 62 patients using in situ hybridization. The association between NS and EGF or EGFR was examined using immunoblotting and real time polymerase chain reaction in a human ESCC cell line transfected with NS siRNA or treated with a selective EGFR inhibitor.
Results: In normal esophageal and ESCC tissues, the positive detection rates were 21.0% (13/62) and 69.4% (43/62) for NS mRNA staining, 40.3% (25/62) and 77.4% (48/62) for EGF mRNA staining, and 30.6% (19/62) and 75.8% (41/62) for EGFR mRNA staining, respectively. These results indicated that NS, EGF and EGFR mRNA expression was upregulated mostly in ESCC tissues. Moreover, the expression of NS, EGF and EGFR mRNA was positively correlated with tumor grade, invasion and lymphatic metastasis of ESCC cells. NS mRNA was co-expressed with EGF and EGFR mRNA in ESCC tissues. The in vitro studies using a human ESCC cell line showed that knockdown of NS with NS siRNA significantly reduced EGF and EGFR expression. However, inhibition of the EGFR kinase activity with a specific EGFR kinase inhibitor had minimal effect on NS expression.
Conclusion: The upregulation of NS, EGF and EGFR mRNA frequently occurs in ESCC tissues and is associated with malignancy of human esophageal squamous tumors. NS is required for EGF and EGFR expression.