The PKCθ pathway participates in the aberrant accumulation of Fra-1 protein in invasive ER-negative breast cancer cells
The PKCθ pathway participates in the aberrant accumulation of Fra-1 protein in invasive ER-negative breast cancer cells
复制标题
DOI：
10.1038/onc.2011.659
复制
发表时间：
2012-11-01
期刊：
影响因子：
8
通讯作者：
Chalbos, D.
中科院分区：
文献类型：
--
作者：
Belguise, K.;Milord, S.;Chalbos, D.
FRA-1在大量的癌细胞和组织中异常表达，新的证据表明这个Fos家族蛋白在肿瘤的发生和许多肿瘤类型的进展或维持中起着重要的作用。在这里，我们表明，在侵袭性雌激素受体(ER-)阴性(ER-)的乳腺癌细胞株中，Fra-1的浓度很高，与其RAS途径状态无关。所有的ER细胞都表达高水平的激活的PKC theta，使用RNA干扰抑制PKC theta的活性或表达显性负突变导致Fra-1丰度显著下降。相反，成分活性PKC theta的异位表达导致低侵袭性ER+细胞中FrA-1的磷酸化和积聚。这种积累是由于通过PKC theta信号稳定了Fra-1蛋白，而PKC家族的其他成员是无效的。与Ste20相关的富含Pro的丙氨酸激酶(SPAK)和ERK1/2的活性都被PKC theta上调，参与了PKC theta驱动的Fra-1的稳定。有趣的是，根据所研究的细胞系，它们的相对贡献似乎是不同的。ERK1/2信号在ER-MDA-MB-231细胞中起主要作用，而FrA-1在ER-BT549细胞中主要通过SPAK信号积累。FRA-1突变分析表明，S265、T223和T230的磷酸化是PKC theta驱动的Fra-1稳定的关键。用针对T223或S265上磷酸化的FrA-1的特异性抗血清证实了该蛋白的磷酸化。此外，Fra-1参与了PKC theta诱导的细胞侵袭，是PKC theta诱导的细胞迁移所必需的。综上所述，我们发现PKC theta信号是ER乳腺癌细胞中FrA-1积聚的重要调节因子。此外，我们的结果表明，PKC theta可能参与了一些乳腺癌的进展，并可能成为新的治疗靶点。
Fra-1 is aberrantly expressed in a large number of cancer cells and tissues, and emerging evidence suggests an important role for this Fos family protein in both oncogenesis and the progression or maintenance of many tumour types. Here, we show that the concentration of Fra-1 is high in invasive oestrogen receptor (ER)-negative (ER-) breast cancer cell lines, regardless of their Ras pathway status. All of the ER-cells express high levels of activated PKC theta, and the inhibition of PKC theta activity using RNA interference or the expression of a dominant-negative mutant results in a dramatic reduction in Fra-1 abundance. Conversely, the ectopic expression of constitutively active PKC theta leads to Fra-1 phosphorylation and accumulation in poorly invasive ER+ cells. This accumulation is due to the stabilisation of the Fra-1 protein through PKC theta signalling, whereas other members of the PKC family are ineffective. Both Ste20-related proline-alanine-rich kinase (SPAK) and ERK1/2, whose activities are upregulated by PKC theta, participate in PKC theta-driven Fra-1 stabilisation. Interestingly, their relative contributions appear to be different depending on the cell line studied. ERK1/2 signalling has a major role in ER- MDA-MB-231 cells, whereas Fra-1 accumulation occurs mainly through SPAK signalling in ER- BT549 cells. Fra-1 mutational analysis shows that the phosphorylation of S265, T223 and T230 is critical for PKC theta-driven Fra-1 stabilisation. Phosphorylation of the protein was confirmed using specific antisera against Fra-1 phosphorylated on T223 or S265. In addition, Fra-1 participates in PKC theta-induced cell invasion and is necessary for PKC theta-induced cell migration. In summary, we identified PKC theta signalling as an important regulator of Fra-1 accumulation in ER- breast cancer cells. Moreover, our results suggest that PKC theta could participate in progression of some breast cancers and could be a new therapeutic target.