Romain Benoît, Hachet-Haas Muriel, Rohr Serge, Brigand Cécile, Galzi Jean-Luc, Gaub Marie-Pierre, Pencreach Erwan, Guenot Dominique
Université de Strasbourg (UdS), EA 3430 Progression tumorale et microenvironnement, Approches translationnelles et Epidémiologie, Fédération de Médecine Translationnelle de Strasbourg (FMTS), Bâtiment U1113, 3 Avenue Molière, 67200 Strasbourg, France.
Mol Cancer. 2014 Mar 14;13:58. doi: 10.1186/1476-4598-13-58.
HIF-1α and CXCR4/CXCL12 have crucial roles in the metastatic process of colorectal cancer. Our aim was to study the significance of targeting HIF-1α and the CXCR4/CXCL12 axis in colorectal cancer to prevent the dissemination process in vitro.
We investigated CXCR4 and CXCR7 mRNA and protein expression in human colon carcinomas and the modulation of their expression by hypoxia and HIF-1α in colon cancer cell lines. The migration of tumor cells in a Boyden chamber was studied after CXCR4 inhibition with siRNA or the CXCR4/CXCL12 neutraligand, chalcone 4.
Analysis of a cohort of colon polyps and chromosome-unstable carcinomas showed that the expression of CXCR4 and CXCR7 was similar to that of the normal mucosa in the polyps and early-stage carcinomas but significantly increased in late stage carcinomas. Our data demonstrate that hypoxia strongly induced the expression of CXCR4 transcript and protein at the cell membrane, both regulated by HIF-1α, whereas CXCR7 expression was independent of hypoxia. After transient hypoxia, CXCR4 levels remained stable at the cell membrane up to 48 hours. Furthermore, reducing CXCR4 expression impaired CXCL12-induced Akt phosphorylation, whereas Erk activation remained unchanged. In contrast, reducing CXCR7 expression did not affect Akt nor Erk activation. In the presence of CXCR4 or CXCR7 siRNAs, a significant reduction in cell migration occurred (37% and 17%, respectively). Although irinotecan inhibited cell migration by 20% (p <0.001), the irinotecan and chalcone 4 combination further increased inhibition to 40% (p <0.001).
We demonstrated, for the first time, that hypoxia upregulated CXCR4 but not CXCR7 expression in tumor cells and that the CXCR4 receptor protein level remains high at the cell membrane when the tumor cells return to normoxia for up to 48 hours. In addition we showed the interest to inhibit the CXCR4 signaling by inhibiting both the HIF-1α and CXCR4/CXCL12 pathway. CXCR4 seems to be a relevant target because it is continuously expressed and functional both in normoxic and hypoxic conditions in tumor cells.
缺氧诱导因子-1α（HIF-1α）和CXC趋化因子受体4/基质细胞衍生因子1（CXCR4/CXCL12）在结直肠癌转移过程中起关键作用。我们的目的是研究靶向HIF-1α和CXCR4/CXCL12轴在结直肠癌中预防体外播散过程的意义。
我们研究了人结肠癌中CXCR4和CXCR7的mRNA及蛋白表达，以及缺氧和HIF-1α对结肠癌细胞系中它们表达的调节。在用小干扰RNA（siRNA）抑制CXCR4或CXCR4/CXCL12中和配体查耳酮4后，研究了肿瘤细胞在博伊登小室中的迁移情况。
对一组结肠息肉和染色体不稳定癌的分析表明，CXCR4和CXCR7在息肉和早期癌中的表达与正常黏膜相似，但在晚期癌中显著增加。我们的数据表明，缺氧强烈诱导细胞膜上CXCR4转录本和蛋白的表达，二者均受HIF-1α调控，而CXCR7的表达与缺氧无关。短暂缺氧后，CXCR4水平在细胞膜上保持稳定长达48小时。此外，降低CXCR4表达会损害CXCL12诱导的Akt磷酸化，而细胞外信号调节激酶（Erk）激活保持不变。相反，降低CXCR7表达不影响Akt和Erk激活。在存在CXCR4或CXCR7 siRNA的情况下，细胞迁移显著减少（分别为37%和17%）。虽然伊立替康抑制细胞迁移20%（p<0.001），但伊立替康与查耳酮4联合使用进一步将抑制率提高到40%（p<0.001）。
我们首次证明，缺氧上调肿瘤细胞中CXCR4而非CXCR7的表达，并且当肿瘤细胞恢复正常氧合长达48小时时，CXCR4受体蛋白水平在细胞膜上仍保持较高。此外，我们表明通过抑制HIF-1α和CXCR4/CXCL12途径来抑制CXCR4信号传导具有意义。CXCR4似乎是一个相关靶点，因为它在肿瘤细胞的常氧和缺氧条件下均持续表达且具有功能。
