CDK4 Amplification Reduces Sensitivity to CDK4/6 Inhibition in Fusion-Positive Rhabdomyosarcoma.
CDK4 Amplification Reduces Sensitivity to CDK4/6 Inhibition in Fusion-Positive Rhabdomyosarcoma.
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DOI：
10.1158/1078-0432.ccr-14-2955
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发表时间：
2015-11-01
期刊：
影响因子：
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通讯作者：
Barr FG
中科院分区：
文献类型：
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作者：
Olanich ME;Sun W;Hewitt SM;Abdullaev Z;Pack SD;Barr FG
横纹肌肉瘤 (RMS) 是最常见的儿科软组织肉瘤，包括 PAX3 或 PAX7-FOXO1 融合阳性亚型。染色体区域 12q13-q14（包含 CDK4 原癌基因）的扩增在融合阳性 RMS 的侵袭性子集中被鉴定。 CDK4/6 抑制剂在 CDK4 扩增的脂肪肉瘤和神经母细胞瘤中具有抗增殖活性，表明 CDK4/6 抑制可作为融合阳性 RMS 的潜在治疗策略。我们研究了 LEE011 在融合阳性 RMS 细胞系和异种移植物中 CDK4 敲低、CDK4 过表达和药理学 CDK4/6 抑制的生物学后果。 CDK4 的敲低通过 G1 期细胞周期停滞消除了 12q13-14 扩增和非扩增融合阳性 RMS 细胞的增殖和转化。这种停滞是通过减少 RB 磷酸化和 E2F 响应基因表达来介导的。在过表达 CDK4 的 RMS 细胞中未观察到 E2F 靶标表达、细胞周期分布、增殖或转化的显着差异。 LEE011 治疗可导致 CDK4 敲低，降低活力、RB 磷酸化和 E2F 响应基因表达，并诱导 G1 期细胞周期停滞。尽管所有融合阳性细胞系均表现出对 CDK4/6 抑制的敏感性，但与 CDK4 扩增和过度表达相关的敏感性降低。这种对 LEE011 的可变反应性在 CDK4 扩增和非扩增融合阳性 RMS 的异种移植模型中得到了重现。我们的数据表明，CDK4 对于 RB-E2F 介导的 G1 期细胞周期进展、增殖和融合阳性 RMS 的转化来说是必要的，但过表达还不够。我们的研究表明，LEE011 在融合阳性 RMS 中具有活性，并表明低 CDK4 表达的融合阳性肿瘤可能特别容易受到 CDK4/6 抑制的影响。
Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma and includes a PAX3- or PAX7-FOXO1 fusion-positive subtype. Amplification of chromosomal region 12q13-q14, which contains the CDK4 proto-oncogene, was identified in an aggressive subset of fusion-positive RMS. CDK4/6 inhibitors have antiproliferative activity in CDK4-amplified liposarcoma and neuroblastoma, suggesting CDK4/6 inhibition as a potential therapeutic strategy in fusion-positive RMS. We examined the biological consequences of CDK4 knockdown, CDK4 overexpression, and pharmacologic CDK4/6 inhibition by LEE011 in fusion-positive RMS cell lines and xenografts. Knockdown of CDK4 abrogated proliferation and transformation of 12q13-14-amplified and non-amplified fusion-positive RMS cells via G1-phase cell cycle arrest. This arrest was mediated by reduced RB phosphorylation and E2F-responsive gene expression. Significant differences in E2F target expression, cell cycle distribution, proliferation, or transformation were not observed in RMS cells overexpressing CDK4. Treatment with LEE011 phenocopied CDK4 knockdown, decreasing viability, RB phosphorylation, and E2F-responsive gene expression and inducing G1-phase cell cycle arrest. Though all fusion-positive cell lines showed sensitivity to CDK4/6 inhibition, there was diminished sensitivity associated with CDK4 amplification and overexpression. This variable responsiveness to LEE011 was recapitulated in xenograft models of CDK4-amplified and non-amplified fusion-positive RMS. Our data demonstrate that CDK4 is necessary but overexpression is not sufficient for RB-E2F-mediated G1-phase cell cycle progression, proliferation, and transformation in fusion-positive RMS. Our studies indicate that LEE011 is active in the setting of fusion-positive RMS and suggest that low CDK4-expressing fusion-positive tumors may be particularly susceptible to CDK4/6 inhibition.