Henan Provincial People's Hospital, 7 Weiwu Road, Zhengzhou, 450003, Henan, China.
The Health Sciences Biomedical Research Facility II, University of California San Diego, La Jolla, CA, 92121, USA.
J Transl Med. 2018 Jul 4;16(1):183. doi: 10.1186/s12967-018-1561-0.
The functions of the protein expressed in the nucleus and cytoplasm were different or opposite. The previous study found that oncogene Klf4 played a role of tumor suppressor in the nasopharyngeal cytoplasm. Cetuximab targeted epidermal growth factor receptor (EGFR) for the treatment of nasopharyngeal carcinoma.
A cohort of 231 cases of advanced nasopharyngeal carcinoma (7th AJCC III-IVa) samples was assessed by immunohistochemistry (IHC), of which, 63 cases were treated with basic treatment without cetuximab, the basic treatment include chemotherapy and radiotherapy, the regent of the chemotherapy include cisplatin and fluorouracil and 168 cases were treated with cetuximab in addition to the basic treatment. The expression of the KLF4 protein was detected in nucleus and cytoplasm, c-Met protein and nuclear EGFR protein (nEGFR) by IHC, and H-Ras and PI3K mutations by an arms-PCR method in vivo. KLF4 was found to specifically express in the cytoplasm by deleting the NES, while H-Ras and PI3K genes were mutated in the nasopharyngeal carcinoma 5-8F and HONE1cell line. The cetuximab resistance in differentially mutated 5-8F and HONE1 cells was analyzed.
The expression of Klf4 in the nucleus was associated with prognosis in 168 patients with cetuximab-treated nasopharyngeal carcinoma, which was found by retrospective analysis. The KLF4 expression in the nucleus was not significantly correlated with the prognosis in 63 nasopharyngeal carcinoma patients treated with basic treatment (P = 0.261). The expression of Klf4 in the nucleus was correlated with mutations of H-Ras and PI3K in 168 cases of nasopharyngeal carcinoma with cetuximab treatment. In vitro experiments showed that Klf4 was specifically expressed in the nucleus of 5-8F and HONE1 cells as assessed by deleting nuclear export signal, which led to cetuximab resistance. H-Ras and PI3K mutations in 5-8F and HONE1 cells also led to the expression of Klf4 in the nucleus and resistance to cetuximab. In HONE1 cells, Klf4 was specifically localized in the cytoplasm by deleting the NES, and the H-Ras and PI3K mutations did not result in an increased expression of Klf4 in the nucleus and cetuximab resistance.
The prognosis of nasopharyngeal carcinoma was not significantly improved by cetuximab treatment when the Klf4 was highly expressed in the nucleus of nasopharyngeal carcinoma tissues. The expression of Klf4 in the nucleus can be used as a biomarker for predicting the effects of cetuximab treatment in nasopharyngeal carcinoma, which might be attributed to the H-RAS and PI3K mutations, leading to cetuximab resistance.
在细胞核和细胞质中表达的蛋白质的功能不同或相反。之前的研究发现，癌基因 Klf4 在鼻咽细胞质中起肿瘤抑制因子的作用。西妥昔单抗靶向表皮生长因子受体（EGFR）用于治疗鼻咽癌。
通过免疫组织化学（IHC）评估了 231 例晚期鼻咽癌（7 期 AJCC III-IVa）样本，其中 63 例未接受西妥昔单抗的基本治疗，基本治疗包括化疗和放疗，化疗的试剂包括顺铂和氟尿嘧啶，168 例在基本治疗的基础上加用西妥昔单抗。通过 IHC 检测核和细胞质中 KLF4 蛋白、c-Met 蛋白和核 EGFR 蛋白（nEGFR）的表达，并通过体内 arms-PCR 方法检测 H-Ras 和 PI3K 突变。通过删除 NES，发现 KLF4 特异性表达在细胞质中，而鼻咽癌细胞系 5-8F 和 HONE1 中的 H-Ras 和 PI3K 基因发生突变。分析差异突变的 5-8F 和 HONE1 细胞中的西妥昔单抗耐药性。
通过回顾性分析发现，在接受西妥昔单抗治疗的 168 例鼻咽癌患者中，细胞核中 Klf4 的表达与预后相关。在接受基本治疗的 63 例鼻咽癌患者中，细胞核中 KLF4 的表达与预后无显著相关性（P=0.261）。在接受西妥昔单抗治疗的 168 例鼻咽癌患者中，细胞核中 Klf4 的表达与 H-Ras 和 PI3K 的突变相关。体外实验表明，通过删除核输出信号，5-8F 和 HONE1 细胞中 KLF4 特异性表达在核内，导致西妥昔单抗耐药。5-8F 和 HONE1 细胞中的 H-Ras 和 PI3K 突变也导致核内 Klf4 的表达和对西妥昔单抗的耐药性。在 HONE1 细胞中，通过删除 NES，Klf4 特异性定位于细胞质，而 H-Ras 和 PI3K 突变不会导致核内 Klf4 表达增加和西妥昔单抗耐药。
当鼻咽癌组织中细胞核 Klf4 高表达时，西妥昔单抗治疗并未显著改善鼻咽癌的预后。细胞核中 Klf4 的表达可作为预测鼻咽癌西妥昔单抗治疗效果的生物标志物，这可能归因于 H-RAS 和 PI3K 突变导致西妥昔单抗耐药。
