Yamaguchi Noritaka, Oyama Tetsunari, Ito Emi, Satoh Hitoshi, Azuma Sakura, Hayashi Mitsuhiro, Shimizu Ken, Honma Reiko, Yanagisawa Yuka, Nishikawa Akira, Kawamura Mika, Imai Jun-ichi, Ohwada Susumu, Tatsuta Kuniaki, Inoue Jun-Ichiro, Semba Kentaro, Watanabe Shinya
Consolidated Research Institute for Advanced Science and Medical Care, Waseda University, Japan.
Cancer Res. 2008 Mar 15;68(6):1881-8. doi: 10.1158/0008-5472.CAN-07-1597.
ErbB2-negative breast tumors represent a significant therapeutic hurdle because of a lack of effective molecular targets. Although NOTCH proteins are known to be involved in mammary tumorigenesis, the functional significance of these proteins in ErbB2-negative breast tumors is not clear. In the present study, we examined the expression of activated NOTCH receptors in human breast cancer cell lines, including ErbB2-negative and ErbB2-positive cell lines. Activated NOTCH1 and NOTCH3 proteins generated by gamma-secretase were detected in most of the cell lines tested, and both proteins activated CSL-mediated transcription. Down-regulation of NOTCH1 by RNA interference had little or no suppressive effect on the proliferation of either ErbB2-positive or ErbB2-negative cell lines. In contrast, down-regulation of NOTCH3 significantly suppressed proliferation and promoted apoptosis of the ErbB2-negative tumor cell lines. Down-regulation of NOTCH3 did not have a significant effect on the ErbB2-positive tumor cell lines. Down-regulation of CSL also suppressed the proliferation of ErbB2-negative breast tumor cell lines, indicating that the NOTCH-CSL signaling axis is involved in cell proliferation. Finally, NOTCH3 gene amplification was detected in a breast tumor cell line and one breast cancer tissue specimen even though the frequency of NOTCH3 gene amplification was low (<1%). Taken together, these findings indicate that NOTCH3-mediated signaling rather than NOTCH1-mediated signaling plays an important role in the proliferation of ErbB2-negative breast tumor cells and that targeted suppression of this signaling pathway may be a promising strategy for the treatment of ErbB2-negative breast cancers.
由于缺乏有效的分子靶点，ErbB2阴性乳腺癌肿瘤构成了一个重大的治疗障碍。尽管已知NOTCH蛋白参与乳腺肿瘤发生，但这些蛋白在ErbB2阴性乳腺癌肿瘤中的功能意义尚不清楚。在本研究中，我们检测了活化的NOTCH受体在人乳腺癌细胞系中的表达，包括ErbB2阴性和ErbB2阳性细胞系。在大多数测试的细胞系中检测到了由γ-分泌酶产生的活化NOTCH1和NOTCH3蛋白，并且这两种蛋白均激活了CSL介导的转录。通过RNA干扰下调NOTCH1对ErbB2阳性或ErbB2阴性细胞系的增殖几乎没有抑制作用。相反，下调NOTCH3显著抑制了ErbB2阴性肿瘤细胞系的增殖并促进了其凋亡。下调NOTCH3对ErbB2阳性肿瘤细胞系没有显著影响。下调CSL也抑制了ErbB2阴性乳腺癌细胞系的增殖，表明NOTCH-CSL信号轴参与细胞增殖。最后，在一个乳腺癌细胞系和一个乳腺癌组织标本中检测到了NOTCH3基因扩增，尽管NOTCH3基因扩增的频率较低（<1%）。综上所述，这些发现表明NOTCH3介导的信号传导而非NOTCH1介导的信号传导在ErbB2阴性乳腺癌细胞的增殖中起重要作用，并且靶向抑制该信号通路可能是治疗ErbB2阴性乳腺癌的一种有前景的策略。
