Bora-Singhal Namrata, Perumal Deepak, Nguyen Jonathan, Chellappan Srikumar
Department of Tumor Biology, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL, 33612, USA.
Department of Tumor Biology, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL, 33612, USA.
Neoplasia. 2015 Jul;17(7):538-51. doi: 10.1016/j.neo.2015.07.001.
Non-small cell lung cancer (NSCLC) patients have very low survival rates because the current therapeutic strategies are not fully effective. Although EGFR tyrosine kinase inhibitors are effective for NSCLC patients harboring EGFR mutations, patients invariably develop resistance to these agents. Alterations in multiple signaling cascades have been associated with the development of resistance to EGFR inhibitors. Sonic Hedgehog and associated Gli transcription factors play a major role in embryonic development and have recently been found to be reactivated in NSCLC, and elevated Gli1 levels correlate with poor prognosis. The Hedgehog pathway has been implicated in the functions of cancer stem cells, although the underlying molecular mechanisms are not clear. In this context, we demonstrate that Gli1 is a strong regulator of embryonic stem cell transcription factor Sox2. Depletion of Gli1 or inhibition of the Hedgehog signaling significantly abrogated the self-renewal of stem-like side-population cells from NSCLCs as well as vascular mimicry of such cells. Gli1 was found to transcriptionally regulate Sox2 through its promoter region, and Gli1 could be detected on the Sox2 promoter. Inhibition of Hedgehog signaling appeared to work cooperatively with EGFR inhibitors in markedly reducing the viability of NSCLC cells as well as the self-renewal of stem-like cells. Thus, our study demonstrates a cooperative functioning of the EGFR signaling and Hedgehog pathways in governing the stem-like functions of NSCLC cancer stem cells and presents a novel therapeutic strategy to combat NSCLC harboring EGFR mutations.
非小细胞肺癌(NSCLC)患者的生存率很低,因为目前的治疗策略并不完全有效。尽管表皮生长因子受体(EGFR)酪氨酸激酶抑制剂对携带EGFR突变的NSCLC患者有效,但患者最终总会对这些药物产生耐药性。多种信号级联的改变与对EGFR抑制剂耐药性的产生有关。音猬因子(Sonic Hedgehog)及相关的Gli转录因子在胚胎发育中起主要作用,最近发现它们在NSCLC中重新激活,Gli1水平升高与预后不良相关。尽管潜在的分子机制尚不清楚,但Hedgehog信号通路与癌症干细胞的功能有关。在此背景下,我们证明Gli1是胚胎干细胞转录因子Sox2的强调节因子。Gli1的缺失或Hedgehog信号的抑制显著消除了NSCLC中干细胞样侧群细胞的自我更新以及此类细胞的血管生成拟态。发现Gli1通过其启动子区域转录调控Sox2,并且在Sox2启动子上可检测到Gli1。Hedgehog信号的抑制似乎与EGFR抑制剂协同作用,显著降低NSCLC细胞的活力以及干细胞样细胞的自我更新。因此,我们的研究证明了EGFR信号通路和Hedgehog信号通路在调控NSCLC癌症干细胞的干细胞样功能中的协同作用,并提出了一种对抗携带EGFR突变的NSCLC的新治疗策略。