Coordination between the eIF2 kinase GCN2 and p53 signaling supports purine metabolism and the progression of prostate cancer

Cancers invoke various pathways to mitigate external and internal stresses to continue their growth and progression. We previously reported that the eIF2 kinase GCN2 and the integrated stress response are constitutively active in prostate cancer (PCa) and are required to maintain amino acid homeostasis needed to fuel tumor growth. However, although loss of GCN2 function reduces intracellular amino acid availability and PCa growth, there is no appreciable cell death. Here, we discovered that the loss of GCN2 in PCa induces prosenescent p53 signaling. This p53 activation occurred through GCN2 inhibition-dependent reductions in purine nucleotides that impaired ribosome biogenesis and, consequently, induced the impaired ribosome biogenesis checkpoint. p53 signaling induced cell cycle arrest and senescence that promoted the survival of GCN2-deficient PCa cells. Depletion of GCN2 combined with loss of p53 or pharmacological inhibition of de novo purine biosynthesis reduced proliferation and enhanced cell death in PCa cell lines, organoids, and xenograft models. Our findings highlight the coordinated interplay between GCN2 and p53 regulation during nutrient stress and provide insight into how they could be targeted in developing new therapeutic strategies for PCa. To investigate how loss of p53 in combination with GCN2 inhibition affects gene expression in the human prostate cancer cell line LNCaP. We performed RNA-seq on wild-type (WT) and p53 KO LNCaP cells treated with the GCN2 inhibitor GCN2iB.

肿瘤可激活多条通路以抵御内外应激，从而维持其生长与进展。我们此前的研究表明，真核翻译起始因子2激酶（eIF2 kinase）GCN2与整合应激反应（integrated stress response）在前列腺癌（prostate cancer, PCa）中呈组成型激活状态，且二者是维持肿瘤生长所需氨基酸稳态的关键。然而，尽管GCN2功能缺失会降低细胞内氨基酸可用性并抑制前列腺癌生长，但并未引发显著的细胞死亡。本研究发现，前列腺癌细胞中GCN2缺失会诱导促衰老型p53信号通路激活。该p53激活机制依赖于GCN2抑制所导致的嘌呤核苷酸水平降低，后者会损伤核糖体生物发生过程，进而激活受损核糖体生物发生检查点。p53信号通路可诱导细胞周期阻滞与细胞衰老，从而维持GCN2缺陷型前列腺癌细胞的存活。在前列腺癌细胞系、类器官与异种移植模型中，联合敲除GCN2与p53，或采用药物抑制从头嘌呤生物合成，均可降低细胞增殖并加剧细胞死亡。本研究结果揭示了营养应激状态下GCN2与p53调控通路之间的协同互作关系，并为靶向二者开发前列腺癌新型治疗策略提供了理论依据。为探究联合敲除p53与抑制GCN2对人前列腺癌细胞系LNCaP的基因表达的影响，我们对经GCN2抑制剂GCN2iB处理的野生型（wild-type, WT）及p53敲除（p53 KO）LNCaP细胞开展了RNA测序（RNA-seq）分析。