KEAP1 Mutation Non-Small Cell Lung Cancer

*仅供医学专业人士阅读参考如果用几个四字词语来形容癌细胞之间的“胞际关系”，大家首先能想到哪些？说它们六亲不认可能过了点儿，但至少铁石心肠也合适吧。毕竟竞争乃至死斗，才是癌细胞之间或者说整个肿瘤微环境的主旋律，那么竞争远远大于合作，癌细胞之间的关系还能好嘛。要是大家的认知过去也和奇点糕一样，好了，今天又该跟着《自然》的更新改写一下了：纽约大学研究团队发表的论文显示，癌细胞也会在掠夺营养时相互合作，面对肿瘤微环境缺乏氨基酸的状况，癌细胞可通过分泌氨基肽酶消化细胞外寡肽，并将消化得到的氨基酸与邻近细胞共同享用来促进增殖，可真是癌细胞之间罕见的“有福同享”了！针对性干预该过程中的关键酶CNDP2，切断癌细胞们在营养层面的合作关系，起到的抑癌作用也非常显著[1]。论文首页截图在详细解释本次研究刷新认知的发现之前，请容奇点糕卖个关子，介绍生物学中的一个名词——阿利效应（Allee effect），毕竟论文的开头也在解释它，省流版就是：个体的适应度随着种群密度的增加而提升，而在个体密度极低时，由于不能通过彼此合作来适应环境和应对挑战，种群反而会濒临灭绝，与传统观念里的个体密度越大、越不适合生存恰好相反。不知道论文挑选企鹅群体作为图示有没有更深的用意嗷既往已经有一些研究推测，癌细胞中也有阿利效应存在，如在癌细胞密度较低时，根据阿利效应构建增殖速率模型，能较传统的线性增长模型更贴合实际增殖速率[2]。但既往研究的推测大多还局限在旁分泌调节等已知机制，而本次纽约大学团队的发现，给奇点糕的感觉更像是在食物并不十分充裕的非洲草原上，狮子们协同捕猎再分享猎物一样呢。研究者们首先在实验中初步证实，癌细胞们在利用葡萄糖等营养物时倒不会互帮互助，但当肿瘤微环境缺乏谷氨酰胺时，癌细胞们的增殖速率就非常符合阿利效应存在时的模型，说明它们会通过合作而非竞争应对这种不利局面，而较为可能的解释，就是癌细胞们把细胞外大量存在的多肽，例如丙氨酰谷氨酰胺（Ala-Gln）拿来当成了谷氨酰胺“代餐”。而抑制多肽转运体或自噬、溶酶体蛋白水解等过程中的关键酶，都没能影响癌细胞对Ala-Gln的代谢利用，于是研究者们推测，癌细胞可能是通过分泌氨基肽酶，在细胞外将寡肽类物质水解来获得游离氨基酸，然后再将氨基酸转运到细胞内代谢，抑制谷氨酰转运的抑癌效应证实了这种猜想。经水解得到的这些游离氨基酸也是微环境内的“共享资源”，如果癌细胞密度太低，它们就不能有效水解寡肽，游离氨基酸也就相应少了，表明阿利效应确实存在。癌细胞可在环境缺乏谷氨酰胺时，在细胞外切割寡肽获得游离氨基酸并代谢接下来，研究者们确认CNDP2是癌细胞们合作水解细胞外寡肽过程中的关键酶，缺失它的癌细胞会更难耐受缺乏谷氨酰胺的环境，如果癌细胞还存在Keap1基因突变，突变导致的氨基酸消耗增加就会使情况雪上加霜，癌细胞不得不更加依赖细胞合作，阿利效应也就更明显，因此敲除Cndp2对Keap1突变型肿瘤的抑癌效果更好。研究者们还经筛选，找到了一种可抑制癌细胞利用寡肽的小分子抑制剂bestatin，它曾在日本获批作为辅助抗癌药物。CNDP2是癌细胞合作水解细胞外寡肽过程中的关键酶最后，研究者们让自然界中的阿利效应在癌细胞身上得到了复现：虽然在体外实验中，因Cndp2被敲除而不能合作的癌细胞可以“坐享其成”，借助“合作型癌细胞”（未敲除Cndp2）提供的游离氨基酸具有增殖速率优势，但当实验转移到小鼠体内时，合作型癌细胞就会转而占据上风，凭借对环境更强的适应性，让非合作型癌细胞几乎在肿瘤中灭绝，而两类癌细胞能否共存，就要看肿瘤微环境的营养物质是否充足了，环境越不利，就越需要合作能力。会合作的癌细胞更容易在体内实验中占据上风当然了，奇点糕介绍本次刷新认知的研究，也不是光让大家感叹癌细胞也很懂合作图存道理的，这种现象也完全可以成为抗癌药物针对性干预的新目标，比如关键酶CNDP2就很适合当精准治疗的靶点嘛，发现更多的类似现象也就意味着更多的精准治疗可能性，也许某一天就能在《医学趋势30讲》里看到相关的最新成果，对不对参考文献：[1]Guzelsoy G, Elorza S D, Ros M, et al. Cooperative nutrient scavenging is an evolutionary advantage in cancer[J]. Nature, 2025.[2]Johnson K E, Howard G, Mo W, et al. Cancer cell population growth kinetics at low densities deviate from the exponential growth model and suggest an Allee effect[J]. PLoS Biology, 2019, 17(8): e3000399.本文作者丨谭硕

Over the last two decades we have made significant progress on fighting cancer: Today, 99% of patients with prostate cancer and 89% of patients with breast cancer will survive for more than 10 years. Unfortunately, this has not been true for lung cancer where only 17% of patients with lung adenocarcinomas will survive that same period of time. The extremely toxic chemotherapy, Cisplatin, is often first-line therapy to these patients, however most lung cancers, especially metastasized tumors, often develop resistance quickly. Recent studies suggest that genetic alterations in the NRF2 pathway cause resistance to Cisplatin. Patients with an NRF2-activating mutation have a ten-fold worse survival outcome than patients whose tumors lack such a genetic lesion (Figure 1). NRF2 is a transcription factor that can regulate the mRNA expression of hundreds of genes across our genome, many of which control how our cells respond to oxidative stress. Interestingly, many of today’s chemotherapies work to kill tumors via induction of oxidative stress. By mutating KEAP1 (a negative regulator of the NRF2 transcription factor), lung cancer develops a big survival advantage when it mutates KEAP1, becoming more resilient to the cytotoxicity brought on by chemotherapy. ‍ Figure 1. Patients with lung cancer are far less likely to survive ten years due to alterations in the NRF2-KEAP1 axis that can confer resistance to first-line chemotherapies such as Cisplatin. ‍ NRF2 biology remains an exciting therapeutic mechanism with a potential to dramatically improve the lives of patients living with lung cancer, however transcription factors are notoriously poor pharmacological targets due to their extremely disordered protein nature making traditional medicinal chemistry quite challenging. To identify a small molecule that either directly or indirectly represses NRF2 activity, we turned to our GRETATM technology. GRETATM is an extremely high throughput assay capable of quantitatively measuring the entire transcriptome: the set of more than 20,000 mRNAs and their associated levels. A small subset of these mRNAs are regulated by the NRF2 transcription factor. With this in mind, we can rank compounds by how selective they are at repressing these NRF2 target genes (Figure 2). ‍ Figure 2. At Arpeggio, we screened a focused and high diversity library of small molecules in H2122 lung cancer cell model harboring a KEAP1-mutation for compounds that repress NRF2 target gene expression. ‍ Following identification of a completely novel small molecule that significantly represses NRF2 transcription factor activity, we characterized the mechanism of this compound in great detail. This molecule induces markers of oxidative stress by increasing the production of H2O2, kills multiple cancer models that only bear a KEAP1 genetic mutation, and actually leads to the proteasomal degradation of NRF2 itself. Following a few rounds of SAR, we’ve identified an orally bioavailable analog of this hit compound (ARP-4922) with an in vivo half-life exceeding 12 hours (Figure 3) that rapidly leads to tumor growth regression in a human lung cancer cell model in vivo. The emergence of chemotherapy resistance and ultimate lung cancer relapse remains a terrible and deadly outcome for thousands of patients every year. With our novel NRF2 degrader, we hope to give hope and time back to these people living with this devastating disease. ‍ Figure 3. A new NRF2 degrader. A) A western blot for NRF2 after exposure of ARP-4922 at 10uM for 24 hours. B) Cell viability of lung cancer models as a function of ARP-4922 concentration C) Mouse in vivo PK curve after oral administration of ARP-4922 at 50 mpk. ‍

Calithera started the year by axing a third of its staff after a monumental Phase II flop in renal cell carcinoma. And while CEO Susan Molineaux has refused to give up on the program, she’s going to need an assist if she wants to close the year on a higher note. That’s where Takeda comes in. For two upfront payments of $10 million and $35 million, tiered royalties and an undisclosed amount in biobucks, Takeda is forking over two Phase II-ready cancer programs to Calithera — one of which targets KEAP1/NRF2 mutations, the same ones Calithera is now pursuing with its once-failed glutaminase inhibitor telaglenastat. “We have learned a great deal about the unmet medical need of patients with KEAP1/NRF2 mutations, as well as how to identify and recruit these patients, during the conduct of our KEAPSAKE trial evaluating telaglenastat,” Molineaux said in a statement. “This complementary approach in KEAP1/NRF2-mutant squamous NSCLC demonstrates our commitment to these patients and the pathway.” The first new candidate in Calithera’s basket is Takeda’s dual TORC 1/2 inhibitor sapanisertib. It’s designed to target a key survival mechanism in KEAP1/NRF2-mutated tumor cells, which are found in a considerable amount of patients with solid tumors, according to the companies. If all goes according to plan, the program is heading into a Phase II trial early next year as a monotherapy in patients with squamous NSCLC harboring a NRF2 mutation, with a readout coming in the next 12 to 18 months. The South San Francisco-based biotech is also getting mivavotinib, an SYK inhibitor that’s also expected to enter Phase II next year for patients with diffuse large B-cell lymphoma with and without MyD88 and CD79 mutations. Calithera also sees potential for studies in non-Hodgkin’s lymphoma and blood cancer. That makes five clinical programs now in Calithera’s pipeline, according to the company’s website. Calithera is still reeling from its Phase II failure in renal cell carcinoma, the results of which were read out back in January. Adding telaglenastat to Exelixis’ Cabometyx failed to improve progression-free survival, investigators concluded. In fact, patients on Cabometyx and placebo lived slightly longer — a PFS of 9.3 months compared to 9.2 months for those treated with telaglenastat and Cabometyx, which doesn’t mean much considering the hazard ratio of 0.94 was far off statistical significance (p=0.65). The company’s stock $CALA is still trading at less than half of what it was last December. Shares were up 1% in premarket trading on Tuesday, going for $2.03 apiece. While that was the end of the road for telaglenastat’s Phase II study in renal cell carcinoma, Molineaux is pushing forward with another Phase II study in KEAP1/NRF2 mutant NSCLC patients, dubbed KEAPSAKE, which dosed the first patients last summer.