c-Myc dependent expression of pro-apoptotic Bim renders HER2-overexpressing breast cancer cells dependent on anti-apoptotic Mcl-1
c-Myc dependent expression of pro-apoptotic Bim renders HER2-overexpressing breast cancer cells dependent on anti-apoptotic Mcl-1
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DOI：
10.1186/1476-4598-10-110
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发表时间：
2011-09-07
期刊：
影响因子：
37.3
通讯作者：
Juin, Philippe
中科院分区：
文献类型：
--
作者：
Campone, Mario;Noel, Belinda;Juin, Philippe
背景资料：已知HER 2下游诱导的抗凋亡信号有助于对过表达EGFR家族该成员的乳腺癌细胞的当前治疗的抗性。这些信号中的一些是否也通过抵消组成性死亡信号而参与肿瘤维持，还不太清楚。为了解决这个问题，我们研究了抗凋亡和促凋亡Bcl-2家族成员（癌细胞存活的关键调节因子）在HER 2过表达乳腺癌细胞的生存能力中可能发挥的作用。我们使用细胞系作为HER 2过表达细胞的体外模型，以评估抗凋亡Bcl-2、Bcl-xL和Mcl-1以及促凋亡Puma和Bim如何影响它们的存活，并研究这些蛋白质的组成型表达是如何被调节的。使用从HER 2-过表达肿瘤的裂解物，并通过分析公开的RNA表达data.Results：我们发现，Mcl-1的耗竭足以诱导HER 2-过表达乳腺癌细胞的凋亡，确认了感兴趣的蛋白质的表达。这种Mcl-1依赖性是由于Bim表达，并且它直接由致癌信号传导引起，因为癌蛋白c-Myc的耗尽（如ChIP测定中所评估的，其占据Bim启动子的区域）降低了Bim水平并减轻了Mcl-1依赖性。因此，通过抑制mTORC 1活性降低c-Myc表达可消除c-Myc对Bim启动子的占用，降低Bim表达并促进对Mcl-1耗竭的耐受性。Western blot分析证实，幼稚HER 2过表达肿瘤组成型表达可检测水平的Mcl-1和Bim，而表达数据提示富集Mcl-1的成绩单在这些tumors.Conclusions：这项工作确立，在HER 2过表达肿瘤，这是必要的，也许是足够的，治疗影响的Mcl-1/Bim平衡，有效诱导癌细胞死亡。
Background: Anti-apoptotic signals induced downstream of HER2 are known to contribute to the resistance to current treatments of breast cancer cells that overexpress this member of the EGFR family. Whether or not some of these signals are also involved in tumor maintenance by counteracting constitutive death signals is much less understood. To address this, we investigated what role anti-and pro-apoptotic Bcl-2 family members, key regulators of cancer cell survival, might play in the viability of HER2 overexpressing breast cancer cells.Methods: We used cell lines as an in vitro model of HER2-overexpressing cells in order to evaluate how antiapoptotic Bcl-2, Bcl-xL and Mcl-1, and pro-apoptotic Puma and Bim impact on their survival, and to investigate how the constitutive expression of these proteins is regulated. Expression of the proteins of interest was confirmed using lysates from HER2-overexpressing tumors and through analysis of publicly available RNA expression data.Results: We show that the depletion of Mcl-1 is sufficient to induce apoptosis in HER2-overexpressing breast cancer cells. This Mcl-1 dependence is due to Bim expression and it directly results from oncogenic signaling, as depletion of the oncoprotein c-Myc, which occupies regions of the Bim promoter as evaluated in ChIP assays, decreases Bim levels and mitigates Mcl-1 dependence. Consistently, a reduction of c-Myc expression by inhibition of mTORC1 activity abrogates occupancy of the Bim promoter by c-Myc, decreases Bim expression and promotes tolerance to Mcl-1 depletion. Western blot analysis confirms that naive HER2-overexpressing tumors constitutively express detectable levels of Mcl-1 and Bim, while expression data hint on enrichment for Mcl-1 transcripts in these tumors.Conclusions: This work establishes that, in HER2-overexpressing tumors, it is necessary, and maybe sufficient, to therapeutically impact on the Mcl-1/Bim balance for efficient induction of cancer cell death.