Department of Surgery, University of Hong Kong, Pokfulam, Hong Kong, SAR, China.
Oncogene. 2013 Aug 29;32(35):4086-99. doi: 10.1038/onc.2012.437. Epub 2012 Oct 8.
Neuroblastoma (NB) is an embryonal tumor and possesses a unique propensity to exhibit either a spontaneous regression or an unrestrained growth. However, the underlying mechanism for this paradoxical clinical outcome remains largely unclear. Quantitative RT-PCR analysis on 102 primary NB tumors revealed that lower Krüppel-like factor 4 (KLF4) expression is frequently found in the unfavorable NB (Mann-Whitney test, P=0.027). In particular with the high-risk factors such as age of patient >1 year, MYCN amplification and low TRKA expression, the decreased expression of KLF4 was significantly associated with an unfavorable NB outcome. Despite knockdown of KLF4 alone is not sufficient to increase tumorigenicity of NB cells in vivo, stable expression of KLF4 short hairpin RNA in Be(2)-C cells significantly promoted growth of NB cells and inhibited cell differentiation toward fibromuscular lineage. In concordant with these observations, overexpression of KLF4 in SH-SY-5Y cells profoundly suppressed cell proliferation by direct upregulation of cell-cycle inhibitor protein p21(WAF1/CIP1), and knocking down p21(WAF1/CIP1) could partially rescue the suppressive effect of KLF4. Importantly, KLF4 overexpressing cells have lost their neuroblastic phenotypes, they were epithelial-like, strongly substrate-adherent, expressing smooth muscle marker and became non-tumorigenic, suggesting that KLF4 expression is crucial for lineage determination of NB cells, probably, favoring spontaneous tumor regression. Subsequent global gene expression profiling further revealed that transforming growth factor beta (TGFβ) and cell-cycle pathways are highly dysregulated upon KLF4 overexpression, and myogenic modulators, MEF2A and MYOD1 were found significantly upregulated. Taken together, we have demonstrated that KLF4 contributes to the favorable disease outcome by directly mediating the growth and lineage determination of NB cells.
神经母细胞瘤（NB）是一种胚胎性肿瘤，具有自发消退或不受控制生长的独特倾向。然而，这种矛盾的临床结果的潜在机制在很大程度上仍不清楚。对 102 例原发性 NB 肿瘤的定量 RT-PCR 分析显示，Krüppel 样因子 4（KLF4）表达降低在不利的 NB 中更为常见（Mann-Whitney 检验，P=0.027）。特别是在高危因素如患者年龄>1 岁、MYCN 扩增和低 TRKA 表达的情况下，KLF4 的表达降低与不利的 NB 预后显著相关。尽管单独敲低 KLF4 不足以增加 NB 细胞在体内的致瘤性，但 Be(2)-C 细胞中 KLF4 短发夹 RNA 的稳定表达显著促进了 NB 细胞的生长，并抑制了向纤维肌肉谱系的细胞分化。与这些观察结果一致，KLF4 在 SH-SY-5Y 细胞中的过表达通过直接上调细胞周期抑制剂蛋白 p21（WAF1/CIP1）强烈抑制细胞增殖，敲低 p21（WAF1/CIP1）可以部分挽救 KLF4 的抑制作用。重要的是，过表达 KLF4 的细胞失去了神经母细胞的表型，它们呈上皮样，强烈贴壁，表达平滑肌标志物，并失去致瘤性，这表明 KLF4 的表达对 NB 细胞的谱系决定至关重要，可能有利于自发肿瘤消退。随后的全基因组表达谱分析进一步表明，KLF4 过表达后转化生长因子β（TGFβ）和细胞周期途径高度失调，肌生成调节剂 MEF2A 和 MYOD1 显著上调。综上所述，我们已经证明 KLF4 通过直接介导 NB 细胞的生长和谱系决定来促进有利的疾病结局。
