PMBA (2-Pyridin-4-yl-methylene-beta-boswellic acid), screened from among the 21 novel series of semisynthetic analogues of β-boswellic acid, is being presented as a lead compound for integrative management of KRAS mutant colorectal cancer (CRC), upon testing and analysis for its anticancerous activity on a panel of NCI-60 cancer cell lines and in vivo models of the disease. PMBA (1.7–29 μM) exhibited potent proliferation inhibition on the cell lines and showed sensitivity in microsatellite instability and microsatellite stable (GSE39582 and GSE92921) subsets of KRAS gene (Kirsten rat sarcoma viral oncogene homolog)-mutated colon cell lines, as revealed via flow cytometry analysis. A considerable decrease in mitogen-activated protein kinase pathway downstream effectors was observed in the treated cell lines via the western blot and STRING (Search tool for the retrieval of interacting genes/proteins) analysis. PMBA was further found to target KRAS at its guanosine diphosphate site. Treatment of the cell lines with PMBA showed significant reduction in MGMT promoter methylation but restored MGMT (O⁶-methylguanine-DNA methyltransferase) messenger ribonucleic acid expression via significant demethylation of the hypermethylated CpG (Cytosine phosphate guanine) sites in the MGMT promoter. A significant decrease in dimethylated H3K9 (Dimethylation of lysine 9 on histone 3) levels in the MGMT promoter in DNA hypo- and hypermethylated HCT-116^G13D and SW-620^G12V cells was observed after treatment. In the MNU (N-methyl-N-nitrosourea)-induced CRC in vivo model, PMBA instillation restricted and repressed polyp formation, suppressed tumor proliferation marker Ki67 (Marker of proliferation), ablated KRAS-associated cytokine signaling, and decreased mortality. Clinical trial data for the parent molecule revealed its effectiveness against the disease, oral bioavailability, and system tolerance. Comprehensively, PMBA represents a new class of KRAS inhibitors having a therapeutic window in the scope of a drug candidate. The findings suggest that the PMBA analogue could inhibit the growth of human CRC in vivo through downregulation of cancer-associated biomarkers as well as reactivate expression of the MGMT gene associated with increased H3K9 acetylation and H3K4 methylation with facilitated transcriptional activation, which might be important in silencing of genes associated with upregulation in the activity of KRAS.

中文翻译：

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2-Pyridin-4-yl-methylene-beta-boswellic Acid─KRAS G13D─微卫星稳定、G12V─微卫星不稳定突变结肠癌中 O6-甲基鸟嘌呤-DNA 甲基转移酶表观转录重编程的潜在候选物

PMBA（2-Pyridin-4-yl-methylene-beta-boswellic acid），从 21 个新系列的 β-乳香酸半合成类似物中筛选出来，被用作 KRAS 突变结直肠癌综合治疗的先导化合物（ CRC），在一组 NCI-60 癌细胞系和疾病的体内模型上测试和分析其抗癌活性。PMBA (1.7–29 μM) 对细胞系表现出有效的增殖抑制作用，并对 KRAS 基因（Kirsten 大鼠肉瘤病毒癌基因同系物）突变的结肠细胞系的微卫星不稳定性和微卫星稳定（GSE39582 和 GSE92921）亚群表现出敏感性，如通过流式细胞术分析。通过蛋白质印迹和 STRING（用于检索相互作用基因/蛋白质的搜索工具）分析，在处理过的细胞系中观察到丝裂原活化蛋白激酶通路下游效应物显着减少。进一步发现 PMBA 在其鸟苷二磷酸位点靶向 KRAS。用 PMBA 处理细胞系显示 MGMT 启动子甲基化显着减少，但 MGMT 恢复（O^6-甲基鸟嘌呤-DNA 甲基转移酶）通过 MGMT 启动子中高甲基化 CpG（磷酸胞嘧啶鸟嘌呤）位点的显着去甲基化表达信使核糖核酸。处理后观察到DNA 低甲基化和高甲基化 HCT-116 ^G13D和 SW-620 ^G12V细胞中 MGMT 启动子中二甲基化 H3K9（组蛋白 3 上赖氨酸 9 的二甲基化）水平显着降低。在 MNU ( N -甲基 - N-nitrosourea) 诱导的 CRC 体内模型，PMBA 滴注限制和抑制息肉形成，抑制肿瘤增殖标志物 Ki67（增殖标志物），消融 KRAS 相关细胞因子信号，并降低死亡率。母体分子的临床试验数据揭示了其对疾病的有效性、口服生物利用度和系统耐受性。综合而言，PMBA 代表了一类新的 KRAS 抑制剂，在候选药物范围内具有治疗窗口。研究结果表明，PMBA 类似物可以通过下调癌症相关生物标志物以及重新激活与 H3K9 乙酰化和 H3K4 甲基化增加相关的 MGMT 基因的表达来抑制体内人类 CRC 的生长，并促进转录激活，