Metabolic reprogramming and epigenetic alterations contribute to the aggressiveness of pancreatic ductal adenocarcinoma (PDAC). Lactate-dependent histone modification is a new type of histone mark, which links glycolysis metabolite to the epigenetic process of lactylation. However, the role of histone lactylation in PDAC remains unclear. The level of histone lactylation in PDAC was identified by western blot and immunohistochemistry, and its relationship with the overall survival was evaluated using a Kaplan-Meier survival plot. The participation of histone lactylation in the growth and progression of PDAC was confirmed through inhibition of histone lactylation by glycolysis inhibitors or lactate dehydrogenase A (LDHA) knockdown both in vitro and in vivo. The potential writers and erasers of histone lactylation in PDAC were identified by western blot and functional experiments. The potential target genes of H3K18 lactylation (H3K18la) were screened by CUT&Tag and RNA-seq analyses. The candidate target genes TTK protein kinase (TTK) and BUB1 mitotic checkpoint serine/threonine kinase B (BUB1B) were validated through ChIP-qPCR, RT-qPCR and western blot analyses. Next, the effects of these two genes in PDAC were confirmed by knockdown or overexpression. The interaction between TTK and LDHA was identified by Co-IP assay. Histone lactylation, especially H3K18la level was elevated in PDAC, and the high level of H3K18la was associated with poor prognosis. The suppression of glycolytic activity by different kinds of inhibitors or LDHA knockdown contributed to the anti-tumor effects of PDAC in vitro and in vivo. E1A binding protein p300 (P300) and histone deacetylase 2 were the potential writer and eraser of histone lactylation in PDAC cells, respectively. H3K18la was enriched at the promoters and activated the transcription of mitotic checkpoint regulators TTK and BUB1B. Interestingly, TTK and BUB1B could elevate the expression of P300 which in turn increased glycolysis. Moreover, TTK phosphorylated LDHA at tyrosine 239 (Y239) and activated LDHA, and subsequently upregulated lactate and H3K18la levels. The glycolysis-H3K18la-TTK/BUB1B positive feedback loop exacerbates dysfunction in PDAC. These findings delivered a new exploration and significant inter-relationship between lactate metabolic reprogramming and epigenetic regulation, which might pave the way toward novel lactylation treatment strategies in PDAC therapy.

中文翻译：

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糖酵解和组蛋白乳酰化之间的正反馈调节驱动胰腺导管腺癌的肿瘤发生

代谢重编程和表观遗传改变导致胰腺导管腺癌（PDAC）的侵袭性。乳酸依赖性组蛋白修饰是一种新型组蛋白标记，它将糖酵解代谢物与乳酰化的表观遗传过程联系起来。然而，组蛋白乳酰化在 PDAC 中的作用仍不清楚。通过蛋白质印迹和免疫组织化学鉴定 PDAC 中的组蛋白乳酰化水平，并使用 Kaplan-Meier 生存图评估其与总生存期的关系。通过体外和体内糖酵解抑制剂或乳酸脱氢酶 A (LDHA) 敲低抑制组蛋白乳酰化，证实了组蛋白乳酰化参与 PDAC 的生长和进展。通过蛋白质印迹和功能实验鉴定了 PDAC 中组蛋白乳酰化的潜在写入者和擦除者。通过CUT&Tag和RNA-seq分析筛选H3K18乳酰化（H3K18la）的潜在靶基因。通过 ChIP-qPCR、RT-qPCR 和蛋白质印迹分析验证了候选靶基因 TTK 蛋白激酶 (TTK) 和 BUB1 有丝分裂检查点丝氨酸/苏氨酸激酶 B (BUB1B)。接下来，通过敲低或过表达来证实这两个基因在PDAC中的作用。通过 Co-IP 测定鉴定了 TTK 和 LDHA 之间的相互作用。 PDAC中组蛋白乳酰化尤其是H3K18la水平升高，H3K18la高水平与不良预后相关。不同种类的抑制剂对糖酵解活性的抑制或LDHA敲低有助于PDAC在体外和体内的抗肿瘤作用。 E1A 结合蛋白 p300 (P300) 和组蛋白脱乙酰酶 2 分别是 PDAC 细胞中组蛋白乳酰化的潜在写入者和擦除者。 H3K18la 在启动子处富集并激活有丝分裂检查点调节因子 TTK 和 BUB1B 的转录。有趣的是，TTK 和 BUB1B 可以提高 P300 的表达，从而增加糖酵解。此外，TTK 在酪氨酸 239 (Y239) 处磷酸化 LDHA 并激活 LDHA，随后上调乳酸和 H3K18la 水平。糖酵解-H3K18la-TTK/BUB1B 正反馈环路加剧了 PDAC 的功能障碍。这些发现提供了新的探索以及乳酸代谢重编程和表观遗传调控之间的重要相互关系，这可能为 PDAC 治疗中新型乳酸化治疗策略铺平道路。