Dysfunctional KEAP1-NRF2 interaction in non-small-cell lung cancer.
Dysfunctional KEAP1-NRF2 interaction in non-small-cell lung cancer.
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DOI：
10.1371/journal.pmed.0030420
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发表时间：
2006-10
期刊：
影响因子：
15.8
通讯作者：
Biswal S
中科院分区：
文献类型：
--
作者：
Singh A;Misra V;Thimmulappa RK;Lee H;Ames S;Hoque MO;Herman JG;Baylin SB;Sidransky D;Gabrielson E;Brock MV;Biswal S
核因子-红细胞-2相关因子2 （NRF2）是一种氧化还原敏感转录因子，可正向调节编码抗氧化剂、外源解毒酶和药物外排泵的基因表达，并在正常细胞中提供抗氧化应激和外源药物的细胞保护。kelch样ech相关蛋白1 （KEAP1）通过靶向蛋白酶体降解来负性调节NRF2活性。细胞抗氧化剂和外源解毒酶的表达增加与肿瘤细胞对化疗药物的耐药性有关。在这里，我们报告了对肺癌患者和细胞系中KEAP1基因组位点的系统分析，发现KEAP1的功能重要区域存在缺失、插入和错义突变，并且在19p13.2处存在非常高比例的杂合性缺失，这表明肺癌中KEAP1双等位基因失活是一种常见事件。对12个细胞系和54个非小细胞肺癌（NSCLC）样本的KEAP1测序显示，共有6个细胞系和10个肿瘤中KEAP1发生体细胞突变，频率分别为50%和19%。所有突变都位于KEAP1蛋白Kelch或干预区高度保守的氨基酸残基内，表明这些突变可能会破坏KEAP1抑制因子的活性。对19p13.2杂合性缺失的评估显示，61%的NSCLC细胞系和41%的肿瘤样本中存在等位基因缺失。癌细胞中KEAP1活性的降低诱导了NRF2的核积累，从而增强了抗氧化剂、外源代谢酶和药物外排泵的转录诱导。据我们所知，这是第一个证明KEAP1双等位基因失活是NSCLC中常见的遗传改变的研究。KEAP1功能的丧失导致NRF2介导的基因表达在癌症中组成性激活，这表明肿瘤细胞操纵NRF2途径以抵抗化疗药物。keap1双等位基因失活是NSCLC中一种常见的基因改变，它与NRF2通路的激活有关，NRF2通路导致对化疗药物产生耐药性的基因表达。肺癌是全球癌症相关死亡的最常见原因。仅在美国，每年就有超过15万人死于这种疾病，这种疾病可以分为两种基本类型——小细胞肺癌和非小细胞肺癌（NSCLC）。五分之四的肺癌是非小细胞肺癌，但这两种类型主要是由吸烟引起的。暴露于烟雾中的化学物质会使肺部细胞的遗传物质发生变化（或突变），导致细胞不受控制地生长并在体内移动。在半数以上的非小细胞肺癌患者中，癌症在确诊之前就已经扩散出肺部，因此无法通过手术切除。众所周知，IV期非小细胞肺癌通常用化疗治疗，即使用有毒化学物质杀死快速生长的癌细胞。然而，只有2%的IV期NSCLC患者在确诊两年后仍然存活，这主要是因为他们的癌细胞对化疗产生了耐药性。它们通过制造破坏癌症药物（解毒酶）或将它们排出细胞（外排泵）的蛋白质，以及制造抗氧化剂（保护细胞免受许多化疗药物引起的氧化损伤的化学物质）来做到这一点。为了改善肺癌患者的前景，研究人员需要发现癌细胞是如何对化疗药物产生抗药性的。解毒酶、外排泵和抗氧化剂通常保护细胞免受环境毒素和生命化学过程产生的氧化剂的侵害。它们的产生受核因子红细胞2相关因子2 （NRF2）的调控。这种转录因子（一种控制其他蛋白质表达的蛋白质）的活性由kelch样ech相关蛋白1 （KEAP1）控制。当没有氧化剂存在时，KEAP1将NRF2保存在细胞的细胞质中（细胞质包围着细胞核，遗传物质储存在那里），并将其作为目标进行破坏。当氧化剂存在时，KEAP1不再与NRF2相互作用，NRF2进入细胞核，诱导保护细胞免受氧化剂和毒素侵害的蛋白质的表达。在这项研究中，研究人员调查了KEAP1的变化是否可能是肺癌耐药的基础。研究人员仔细观察了从肺肿瘤组织和几种肺癌细胞系（在实验室中培养的肿瘤细胞）中提取的KEAP1基因编码。他们发现，在一半的细胞系和五分之一的肿瘤样本中，已知对其功能起重要作用的KEAP1部分发生了突变。他们还发现，大约一半的样本丢失了KEAP1基因的一个拷贝的一部分——细胞通常每个基因有两个拷贝。6个KEAP1突变的肿瘤中有5个也失去了KEAP1的一个拷贝，遗传学家称之为双等位基因失活。这意味着这些肿瘤应该没有功能性的KEAP1。当研究人员通过对肿瘤进行NRF2染色来检查这一点时，他们发现肿瘤细胞比正常细胞含有更多的NRF2，并且NRF2积聚在细胞核中。此外，肿瘤细胞比正常细胞产生更多的解毒酶、外排蛋白和抗氧化剂。最后，研究人员发现，与正常肺细胞相比，KEAP1突变的肺癌细胞对化疗药物的耐药性更强。这些结果表明，KEAP1双等位基因失活是NSCLC中常见的遗传改变，并提示KEAP1活性的丧失是肺肿瘤增加其NRF2活性并对化疗药物产生耐药性的一种途径。需要检查更多的肺癌样本来证实这一结果，并且需要在其他癌症中进行类似的研究，以确定KEAP1活性的丧失是否是肿瘤对化疗产生耐药性的共同机制。如果这些研究证实高NRF2活性（通过突变或其他途径）通常与肿瘤对化疗的不良反应有关，那么NRF2抑制剂的开发可能有助于改善化疗耐药肿瘤患者的治疗结果。请通过本摘要的在线版本http://dx.doi.org/10.1371/journal.pmed.0030420访问这些网站。美国国家癌症研究所关于肺癌和癌症治疗的信息MedlinePlus关于小细胞肺癌和非小细胞肺癌英国癌症研究中心关于肺癌的信息维基百科关于肺癌和化疗的条目（注意维基百科是一个免费的在线百科全书，任何人都可以编辑）
Nuclear factor erythroid-2 related factor 2 (NRF2) is a redox-sensitive transcription factor that positively regulates the expression of genes encoding antioxidants, xenobiotic detoxification enzymes, and drug efflux pumps, and confers cytoprotection against oxidative stress and xenobiotics in normal cells. Kelch-like ECH-associated protein 1 (KEAP1) negatively regulates NRF2 activity by targeting it to proteasomal degradation. Increased expression of cellular antioxidants and xenobiotic detoxification enzymes has been implicated in resistance of tumor cells against chemotherapeutic drugs. Here we report a systematic analysis of the KEAP1 genomic locus in lung cancer patients and cell lines that revealed deletion, insertion, and missense mutations in functionally important domains of KEAP1 and a very high percentage of loss of heterozygosity at 19p13.2, suggesting that biallelic inactivation of KEAP1 in lung cancer is a common event. Sequencing of KEAP1 in 12 cell lines and 54 non-small-cell lung cancer (NSCLC) samples revealed somatic mutations in KEAP1 in a total of six cell lines and ten tumors at a frequency of 50% and 19%, respectively. All the mutations were within highly conserved amino acid residues located in the Kelch or intervening region domain of the KEAP1 protein, suggesting that these mutations would likely abolish KEAP1 repressor activity. Evaluation of loss of heterozygosity at 19p13.2 revealed allelic losses in 61% of the NSCLC cell lines and 41% of the tumor samples. Decreased KEAP1 activity in cancer cells induced greater nuclear accumulation of NRF2, causing enhanced transcriptional induction of antioxidants, xenobiotic metabolism enzymes, and drug efflux pumps. This is the first study to our knowledge to demonstrate that biallelic inactivation of KEAP1 is a frequent genetic alteration in NSCLC. Loss of KEAP1 function leading to constitutive activation of NRF2-mediated gene expression in cancer suggests that tumor cells manipulate the NRF2 pathway for their survival against chemotherapeutic agents. Biallelic inactivation ofKEAP1, a frequent genetic alteration in NSCLC, is associated with activation of the NRF2 pathway which leads to expression of genes that contribute to resistance against chemotherapeutic drugs. Lung cancer is the most common cause of cancer-related death worldwide. More than 150,000 people in the US alone die every year from this disease, which can be split into two basic types—small cell lung cancer and non-small-cell lung cancer (NSCLC). Four out of five lung cancers are NSCLCs, but both types are mainly caused by smoking. Exposure to chemicals in smoke produces changes (or mutations) in the genetic material of the cells lining the lungs that cause the cells to grow uncontrollably and to move around the body. In more than half the people who develop NSCLC, the cancer has spread out of the lungs before it is diagnosed, and therefore can't be removed surgically. Stage IV NSCLC, as this is known, is usually treated with chemotherapy—toxic chemicals that kill the fast-growing cancer cells. However, only 2% of people with stage IV NSCLC are still alive two years after their diagnosis, mainly because their cancer cells become resistant to chemotherapy. They do this by making proteins that destroy cancer drugs (detoxification enzymes) or that pump them out of cells (efflux pumps) and by making antioxidants, chemicals that protect cells against the oxidative damage caused by many chemotherapy agents. To improve the outlook for patients with lung cancer, researchers need to discover exactly how cancer cells become resistant to chemotherapy drugs. Detoxification enzymes, efflux pumps, and antioxidants normally protect cells from environmental toxins and from oxidants produced by the chemical processes of life. Their production is regulated by nuclear factor erythroid-2 related factor 2 (NRF2). The activity of this transcription factor (a protein that controls the expression of other proteins) is controlled by the protein Kelch-like ECH-associated protein 1 (KEAP1). KEAP1 holds NRF2 in the cytoplasm of the cell (the cytoplasm surrounds the cell's nucleus, where the genetic material is stored) when no oxidants are present and targets it for destruction. When oxidants are present, KEAP1 no longer interacts with NRF2, which moves into the nucleus and induces the expression of the proteins that protect the cell against oxidants and toxins. In this study, the researchers investigated whether changes in KEAP1 might underlie the drug resistance seen in lung cancer. The researchers looked carefully at the gene encoding KEAP1 in tissue taken from lung tumors and in several lung cancer cell lines—tumor cells that have been grown in a laboratory. They found mutations in parts of KEAP1 known to be important for its function in half the cell lines and a fifth of the tumor samples. They also found that about half of the samples had lost part of one copy of the KEAP1 gene—cells usually have two copies of each gene. Five of the six tumors with KEAP1 mutations had also lost one copy of KEAP1—geneticists call this biallelic inactivation. This means that these tumors should have no functional KEAP1. When the researchers checked this by staining the tumors for NRF2, they found that the tumor cells had more NRF2 than normal cells and that it accumulated in the nucleus. In addition, the tumor cells made more detoxification enzymes, efflux proteins, and antioxidants than normal cells. Finally, the researchers showed that lung cancer cells with KEAP1 mutations were more resistant to chemotherapy drugs than normal lung cells were. These results indicate that biallelic inactivation of KEAP1 is a frequent genetic alteration in NSCLC and suggest that the loss of KEAP1 activity is one way that lung tumors can increase their NRF2 activity and develop resistance to chemotherapeutic drugs. More lung cancer samples need to be examined to confirm this result, and similar studies need to be done in other cancers to see whether loss of KEAP1 activity is a common mechanism by which tumors become resistant to chemotherapy. If such studies confirm that high NRF2 activity (either through mutation or by some other route) is often associated with a poor tumor response to chemotherapy, then the development of NRF2 inhibitors might help to improve treatment outcomes in patients with chemotherapy-resistant tumors. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030420. US National Cancer Institute information on lung cancer and on cancer treatment MedlinePlus entries on small cell lung cancer and NSCLC Cancer Research UK information on lung cancer Wikipedia entries on lung cancer and chemotherapy (note that Wikipedia is a free online encyclopedia that anyone can edit)
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DOI：
10.1093/jnci/85.11.897
发表时间：
1993-06-02
期刊：
JOURNAL OF THE NATIONAL CANCER INSTITUTE
影响因子：
--
作者：
TSAI, CM;CHANG, KT;GAZDAR, AF
通讯作者：
GAZDAR, AF
影响因子：
5.3
作者：
Karapetian, RN;Evstafieva, AG;Vartapetian, AB
通讯作者：
Vartapetian, AB
影响因子：
16
作者：
Padmanabhan, B;Tong, KI;Yamamoto, M
通讯作者：
Yamamoto, M
影响因子：
15.9
作者：
Thimmulappa, RK;Lee, H;Biswal, S
通讯作者：
Biswal, S
影响因子：
3.8
作者：
Aoki, Y;Sato, H;Yamamoto, M
通讯作者：
Yamamoto, M