Epidermal growth factor receptor (EGFR) is usually overexpressed in
nasopharyngeal carcinoma (NPC). Our recent in vitro study has demonstrated that
cetuximab (an antibody
drug against EGFR) inhibits the growth of NPC cell lines, HK1 and HONE-1. The present study investigates the effect of
cetuximab on
protein expressions of NPC cell lines. NPC cells were cultured in the absence or presence of
cetuximab at the IC50 concentrations (3 nM for HK1 and 0.3 nM for HONE-1) for 48 h, and total cell lysates were extracted. The cell lysates were then subjected to two-dimensional
polyacrylamide gel electrophoresis (2D PAGE), and the 2D gel images were compared to discover the
protein changes caused by
cetuximab treatment. The common differentially expressed
proteins in NPC cell lines were identified by
peptide mass fingerprinting. We found that
heat shock protein gp96 was down-regulated, while
alpha-enolase,
tumor suppressor protein maspin, and
p97 valosin containing protein were up-regulated after
cetuximab treatment. Reverse-transcription polymerase chain reaction (RT-PCR) analysis confirmed that the changes in
protein levels of gp96,
maspin, and p97 coincided with
mRNA levels, indicating that these
proteins were regulated at transcriptional levels. Up-regulation of gp96 has been observed in various
cancers and reported to have
tumor protective effects. P97 is a multifunctional
AAA (ATPase associated with a variety of activities)
protein and is involved in numerous cellular activities including
membrane transport, protein folding, protein degradation, and cell division.
Maspin has been shown to increase apoptosis, and block the growth, invasion, and metastatic properties of many
tumors. The comparative
tumor suppression effects of
cetuximab and
maspin suggest that
cetuximab might exert its antitumor effects partly by up-regulation of
maspin expression. The study also indicates that proteomic analysis is a promising approach to elucidate the functional mechanisms of anticancer drugs. Pharmacoproteomic study may also help to identify clinical responders for
drug treatment and provide insight for new
drug development.