Department of Oncogene Regulation, Chittaranjan National Cancer Institute, Kolkata, India.
PLoS One. 2013 May 10;8(5):e63440. doi: 10.1371/journal.pone.0063440. Print 2013.
The aim of this study is to understand the mechanism of EGFR overexpression in head and neck squamous cell carcinoma (HNSCC). For this reason, expression/mutation of EGFR were analyzed in 30 dysplastic head and neck lesions and 148 HNSCC samples of Indian patients along with 3 HNSCC cell lines. In addition, deletion/methylation/mutation/expression of SH3GL2 (associated with EGFR degradation) and CDC25A (associated with dephosphorylation of EGFR) were analyzed in the same set of samples. Our study revealed high frequency of EGFR overexpression (66-84%), low frequency of gene amplification (10-32.5%) and absence of functional mutation in the dysplastic lesions and HNSCC samples. No correlation was found between protein overexpression and mRNA expression/gene amplification status of EGFR. On the other hand, frequent alterations (deletion/methylation) of SH3GL2 (63-77%) and CDC25A (37-64%) were seen in the dysplastic and HNSCC samples. Two novel single nucleotide polymorphism (SNPs) were found in the promoter region of SH3GL2. Reduced expression of these genes showed concordance with their alterations. Overexpression of EGFR and p-EGFR were significantly associated with reduced expression and alterations of SH3GL2 and CDC25A respectively. In-vitro demethylation experiment by 5-aza-2'-deoxycytidine (5-aza-dC) showed upregulation of SH3GL2 and CDC25A and downregulation of EGFR expression in Hep2 cell line. Poor patient outcome was predicted in the cases with alterations of SH3GL2 and CDC25A in presence of human papilloma virus (HPV) infection. Also, low SH3GL2 and high EGFR expression was a predictor of poor patient survival. Thus, our data suggests that overexpression of EGFR due to its reduced degradation and dephosphorylation is needed for development of HNSCC.
本研究旨在探讨表皮生长因子受体（EGFR）在头颈部鳞状细胞癌（HNSCC）中过表达的机制。为此，对 30 例发育不良的头颈部病变和 148 例印度患者的 HNSCC 样本以及 3 种 HNSCC 细胞系进行了 EGFR 的表达/突变分析。此外，还对同一组样本中 SH3GL2（与 EGFR 降解相关）和 CDC25A（与 EGFR 去磷酸化相关）的缺失/甲基化/突变/表达进行了分析。研究结果显示，在发育不良病变和 HNSCC 样本中，EGFR 过表达（66-84%）频率较高，基因扩增频率较低（10-32.5%），且不存在功能突变。蛋白过表达与 EGFR 的 mRNA 表达/基因扩增状态之间无相关性。另一方面，在发育不良和 HNSCC 样本中，SH3GL2（63-77%）和 CDC25A（37-64%）频繁发生改变（缺失/甲基化）。在 SH3GL2 的启动子区域发现了两个新的单核苷酸多态性（SNP）。这些基因表达下调与它们的改变一致。EGFR 和 p-EGFR 的过表达与 SH3GL2 和 CDC25A 的表达下调和改变显著相关。5-氮杂-2'-脱氧胞苷（5-aza-dC）的体外去甲基化实验表明，在 Hep2 细胞系中，SH3GL2 和 CDC25A 的表达上调，而 EGFR 表达下调。在 HPV 感染的情况下，SH3GL2 和 CDC25A 的改变预测患者预后不良。此外，SH3GL2 表达降低和 EGFR 表达升高是患者生存不良的预测因素。因此，我们的数据表明，HNSCC 的发生需要 EGFR 的过度表达，这是由于其降解和去磷酸化减少所致。
