Hannover Medical School, Centre for Pharmacology and Toxicology, Carl-Neuberg-Str.1, 30625, Hannover, Germany.
Clin Epigenetics. 2023 May 19;15(1):89. doi: 10.1186/s13148-023-01500-1.
Targeting the epigenome of cancerous diseases represents an innovative approach, and the DNA methylation inhibitor decitabine is recommended for the treatment of hematological malignancies. Although epigenetic alterations are also common to solid tumors, the therapeutic efficacy of decitabine in colorectal adenocarcinomas (COAD) is unfavorable. Current research focuses on an identification of combination therapies either with chemotherapeutics or checkpoint inhibitors in modulating the tumor microenvironment. Here we report a series of molecular investigations to evaluate potency of decitabine, the histone deacetylase inhibitor PBA and the cytidine deaminase (CDA) inhibitor tetrahydrouridine (THU) in patient derived functional and p53 null colon cancer cell lines (CCCL). We focused on the inhibition of cell proliferation, the recovery of tumor suppressors and programmed cell death, and established clinical relevance by evaluating drug responsive genes among 270 COAD patients. Furthermore, we evaluated treatment responses based on CpG island density.
Decitabine caused marked repression of the DNMT1 protein. Conversely, PBA treatment of CCCL recovered acetylation of histone 3 lysine residues, and this enabled an open chromatin state. Unlike single decitabine treatment, the combined decitabine/PBA treatment caused > 95% inhibition of cell proliferation, prevented cell cycle progression especially in the S and G2-phase and induced programmed cell death. Decitabine and PBA differed in their ability to facilitate re-expression of genes localized on different chromosomes, and the combined decitabine/PBA treatment was most effective in the re-expression of 40 tumor suppressors and 13 genes typically silenced in cancer-associated genomic regions of COAD patients. Furthermore, this treatment repressed expression of 11 survival (anti-apoptotic) genes and augmented expression of X-chromosome inactivated genes, especially the lncRNA Xist to facilitate p53-mediated apoptosis. Pharmacological inhibition of CDA by THU or its gene knockdown prevented decitabine inactivation. Strikingly, PBA treatment recovered the expression of the decitabine drug-uptake transporter SLC15A1, thus enabling high tumor drug-loads. Finally, for 26 drug responsive genes we demonstrated improved survival in COAD patients.
The combined decitabine/PBA/THU drug treatment improved drug potency considerably, and given their existing regulatory approval, our findings merit prospective clinical trials for the triple combination in COAD patients.
针对癌症的表观基因组学是一种创新的方法，DNA 甲基化抑制剂地西他滨被推荐用于治疗血液恶性肿瘤。虽然表观遗传学改变也常见于实体瘤，但地西他滨在结直肠腺癌（COAD）中的治疗效果并不理想。目前的研究重点是确定与化疗药物或检查点抑制剂联合治疗以调节肿瘤微环境的方法。在这里，我们报告了一系列分子研究，以评估地西他滨、组蛋白去乙酰化酶抑制剂 PBA 和胞嘧啶脱氨酶（CDA）抑制剂四氢尿苷（THU）在患者来源的功能性和 p53 缺失结肠癌细胞系（CCCL）中的功效。我们专注于抑制细胞增殖、恢复肿瘤抑制因子和程序性细胞死亡，并通过评估 270 名 COAD 患者中的药物反应基因来确定临床相关性。此外，我们还根据 CpG 岛密度评估了治疗反应。
地西他滨导致 DNMT1 蛋白明显抑制。相反，CCCL 中 PBA 的治疗恢复了组蛋白 3 赖氨酸残基的乙酰化，从而使染色质处于开放状态。与单独使用地西他滨治疗不同，联合使用地西他滨/PBA 治疗可导致细胞增殖抑制率超过 95%，特别是在 S 和 G2 期阻止细胞周期进程，并诱导程序性细胞死亡。地西他滨和 PBA 在促进定位于不同染色体上的基因重新表达的能力上有所不同，联合使用地西他滨/PBA 治疗在重新表达 40 个肿瘤抑制因子和 13 个通常在 COAD 患者癌症相关基因组区域中沉默的基因方面最为有效。此外，这种治疗还抑制了 11 个生存（抗凋亡）基因的表达，并增强了 X 染色体失活基因的表达，特别是长链非编码 RNA Xist，以促进 p53 介导的凋亡。通过 THU 或其基因敲低抑制 CDA 的药理学抑制可防止地西他滨失活。引人注目的是，PBA 治疗恢复了地西他滨药物摄取转运蛋白 SLC15A1 的表达，从而使肿瘤内药物负荷增加。最后，对于 26 个药物反应基因，我们证明了 COAD 患者的生存得到了改善。
联合使用地西他滨/PBA/THU 药物治疗显著提高了药物功效，鉴于它们现有的监管批准，我们的发现值得在 COAD 患者中进行三药联合的前瞻性临床试验。
