PDF(Pubmed)
Abstract：
UNASSIGNED: Cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors have shown significant activity against several solid tumors by reducing the phosphorylation of the canonical CDK4/6 substrate retinoblastoma (Rb) protein, while the anti-tumor effect of CDK4/6 inhibitors on Rb-deficient tumors is not clear. Most small cell lung cancers (SCLCs) are Rb-deficient and show very modest response to immune checkpoint blockade (ICB) despite recent advances in the use of immunotherapy. Here, we aimed to investigate the direct effect of CDK4/6 inhibition on SCLC cells and determine its efficacy in combination therapy for SCLC.
UNASSIGNED: The immediate impact of CDK4/6 inhibitor abemaciclib on cell cycle, cell viability and apoptosis in four SCLC cell lines was initially checked. To explore the effect of abemaciclib on double-strand DNA (ds-DNA) damage induction and the combination impact of abemaciclib coupled with radiotherapy (RT), western blot, immunofluorescence (IF) and quantitative real-time polymerase chain reaction (qRT-PCR) were performed. An Rb-deficient immunocompetent murine SCLC model was established to evaluate efficacy of abemaciclib in combination therapy. Histological staining, flow cytometry analysis and RNA sequencing were performed to analyze alteration of infiltrating immune cells in tumor microenvironment (TME).
UNASSIGNED: Here, we demonstrated that abemaciclib induced increased ds-DNA damage in Rb-deficient SCLC cells. Combination of abemaciclib and RT induced more cytosolic ds-DNA, and activated the STING pathway synergistically. We further showed that combining low doses of abemaciclib with low-dose RT (LDRT) plus anti-programmed cell death protein-1 (anti-PD-1) antibody substantially potentiated CD8+ T cell infiltration and significantly inhibited tumor growth and prolonged survival in an Rb-deficient immunocompetent murine SCLC model.
UNASSIGNED: Our results define previously uncertain DNA damage-inducing properties of CDK4/6 inhibitor abemaciclib in Rb-deficient SCLCs, and demonstrate that low doses of abemaciclib combined with LDRT inflame the TME and enhance the efficacy of anti-PD-1 immunotherapy in SCLC model, which represents a potential novel therapeutic strategy for SCLC.
UNASSIGNED: The immediate impact of CDK4/6 inhibitor abemaciclib on cell cycle, cell viability and apoptosis in four SCLC cell lines was initially checked. To explore the effect of abemaciclib on double-strand DNA (ds-DNA) damage induction and the combination impact of abemaciclib coupled with radiotherapy (RT), western blot, immunofluorescence (IF) and quantitative real-time polymerase chain reaction (qRT-PCR) were performed. An Rb-deficient immunocompetent murine SCLC model was established to evaluate efficacy of abemaciclib in combination therapy. Histological staining, flow cytometry analysis and RNA sequencing were performed to analyze alteration of infiltrating immune cells in tumor microenvironment (TME).
UNASSIGNED: Here, we demonstrated that abemaciclib induced increased ds-DNA damage in Rb-deficient SCLC cells. Combination of abemaciclib and RT induced more cytosolic ds-DNA, and activated the STING pathway synergistically. We further showed that combining low doses of abemaciclib with low-dose RT (LDRT) plus anti-programmed cell death protein-1 (anti-PD-1) antibody substantially potentiated CD8+ T cell infiltration and significantly inhibited tumor growth and prolonged survival in an Rb-deficient immunocompetent murine SCLC model.
UNASSIGNED: Our results define previously uncertain DNA damage-inducing properties of CDK4/6 inhibitor abemaciclib in Rb-deficient SCLCs, and demonstrate that low doses of abemaciclib combined with LDRT inflame the TME and enhance the efficacy of anti-PD-1 immunotherapy in SCLC model, which represents a potential novel therapeutic strategy for SCLC.
摘要：
■细胞周期蛋白依赖性激酶4和6（CDK4/6）抑制剂通过减少经典CDK4/6底物视网膜母细胞瘤（Rb）蛋白的磷酸化，显示出对几种实体瘤的显着活性，而CDK4/6抑制剂对Rb缺陷型肿瘤的抗肿瘤作用尚不清楚。大多数小细胞肺癌（SCLC）缺乏Rb，尽管最近在使用免疫疗法方面取得了进展，但对免疫检查点阻断（ICB）的反应非常温和。这里,我们旨在研究CDK4/6抑制对SCLC细胞的直接作用,并确定其在SCLC联合治疗中的疗效.
■CDK4/6抑制剂abemaciclib对细胞周期的直接影响，最初检查了四种SCLC细胞系中的细胞活力和凋亡。探讨abemaciclib对双链DNA（ds-DNA）损伤诱导的影响以及abemaciclib与放疗（RT）的联合作用。westernblot,免疫荧光（IF）和定量实时聚合酶链反应（qRT-PCR）。建立了Rb缺陷的免疫活性鼠SCLC模型，以评估abemaciclib在联合治疗中的疗效。组织学染色,流式细胞术分析和RNA测序分析肿瘤微环境（TME）中浸润免疫细胞的变化。
■这里，我们证明了abemaciclib在Rb缺陷型SCLC细胞中诱导增加的ds-DNA损伤。abemaciclib和RT联合诱导更多的细胞质ds-DNA，并协同激活STING途径。我们进一步表明，低剂量的abemaciclib与低剂量RT（LDRT）加抗程序性细胞死亡蛋白-1（抗PD-1）抗体的组合可显著增强CD8+T细胞浸润，并显著抑制肿瘤生长和延长在Rb缺陷型免疫活性鼠SCLC模型中的存活。
■我们的结果定义了先前不确定的CDK4/6抑制剂abemaciclib在Rb缺陷型SCLC中的DNA损伤诱导特性，并证明低剂量的abemaciclib联合LDRT可以刺激TME并增强抗PD-1免疫疗法在SCLC模型中的疗效，这代表了SCLC的潜在新治疗策略。
■CDK4/6抑制剂abemaciclib对细胞周期的直接影响，最初检查了四种SCLC细胞系中的细胞活力和凋亡。探讨abemaciclib对双链DNA（ds-DNA）损伤诱导的影响以及abemaciclib与放疗（RT）的联合作用。westernblot,免疫荧光（IF）和定量实时聚合酶链反应（qRT-PCR）。建立了Rb缺陷的免疫活性鼠SCLC模型，以评估abemaciclib在联合治疗中的疗效。组织学染色,流式细胞术分析和RNA测序分析肿瘤微环境（TME）中浸润免疫细胞的变化。
■这里，我们证明了abemaciclib在Rb缺陷型SCLC细胞中诱导增加的ds-DNA损伤。abemaciclib和RT联合诱导更多的细胞质ds-DNA，并协同激活STING途径。我们进一步表明，低剂量的abemaciclib与低剂量RT（LDRT）加抗程序性细胞死亡蛋白-1（抗PD-1）抗体的组合可显著增强CD8+T细胞浸润，并显著抑制肿瘤生长和延长在Rb缺陷型免疫活性鼠SCLC模型中的存活。
■我们的结果定义了先前不确定的CDK4/6抑制剂abemaciclib在Rb缺陷型SCLC中的DNA损伤诱导特性，并证明低剂量的abemaciclib联合LDRT可以刺激TME并增强抗PD-1免疫疗法在SCLC模型中的疗效，这代表了SCLC的潜在新治疗策略。
