title: The Ras signaling pathway mediates cetuximab resistance in nasopharyngeal carcinoma.
abstract: This work aimed to investigate the role of the Ras signaling pathway in cetuximab resistance in human nasopharyngeal carcinoma (hNPC). An hNPC 5-8F cell line was induced by stepwise exposure to increasing doses of cetuximab. Western blot was conducted to detect protein levels. Our results are as follows: cetuximab-resistant hNPC 5-8F/Erbitux cell lines were successfully developed. After treatment with cetuximab for 3 and 5 d, the RI was 1.2 and 1.1, respectively. Compared with the 5-8F cells, the protein expression levels of H-ras, JNK/P-JNK, P-ERK1/2, p38/P-p38, P-AKT, NF-κB p65/P-NF-κB p65 and c-fos were significantly increased in the 5-8F/Erbitux cells (P=0.000 for all); however, the protein expression levels of ERK1/2 and c-jun/P-c-jun were significantly decreased (P=0.000 for all) and AKT protein expression showed no significant change (P=0.176). After the 5-8F/Erbitux cells were transfected with H-ras shRNA, H-ras protein expression was significantly decreased (P=0.000) and cetuximab sensitivity improved. In contrast, in the 5-8F/Erbitux+siH-ras cells, protein expression levels of P-ERK1/2, P-JNK, P-AKT and NF-κB p65/P-NF-κB p65 were significantly decreased (P=0.000 for all). Additionally, protein expression levels of JNK, ERK1/2, p38/P-p38 and c-jun/P-c-jun were significantly increased (P=0.000 for all), but protein expression levels of AKT and c-fos did not change significantly (P=0.061 and P=0.068, respectively). In conclusion, the activation of the H-ras/ERK1/2, H-ras/JNK and PI3K-AKT signaling pathways is closely associated with cetuximab resistance in 5-8F/Erbitux cells. NF-κB is activated in 5-8F/Erbitux cells without activation of c-jun.
authors: Department of Oncology, Nanfang Hospital, Guangzhou 510515, China.
authors: Qiang
authors: Q
authors: Zuo
authors: Min
authors: M
authors: Shi
authors: Jinzhang
authors: J
authors: Chen
authors: Wangjun
authors: W
authors: Liao