Exploitation of the chick embryo chorioallantoic membrane (CAM) as a platform for anti-metastatic drug testing.

The establishment of clinically relevant models for tumor metastasis and drug testing is a major challenge in cancer research. Here we report a physiologically relevant assay enabling quantitative analysis of metastatic capacity of tumor cells following implantation into the chorioallantoic membrane (CAM). Engraftment of as few as 103 non-small cell lung cancer (NSCLC) and prostate cancer (PCa) cell lines was sufficient for both primary tumor and metastasis formation. Standard 2D-imaging as well as 3D optical tomography imaging were used for the detection of fluorescent metastatic foci in the chick embryo. H2228- and H1975-initiated metastases were confirmed by genomic analysis. We quantified the inhibitory effect of docetaxel on LNCaP, and that of cisplatin on A549- and H1299-initiated metastatic growths. The CAM assay also mimicked the sensitivity of ALK-rearranged H2228 and EGFR-mutated H1975 NSCLC cells to tyrosine kinase inhibitors crizotinib and gefitinib respectively, as well as sensitivity of LNCaP cells to androgen-dependent enzalutamide therapy. The assay was suggested to reconstitute the bone metastatic tropism of PCa cells. We show that the CAM chick embryo model may be a powerful preclinical platform for testing and targeting of the metastatic capacity of cancer cells.

ATM-dependent expression of IEX-1 controls nuclear accumulation of Mcl-1 and the DNA damage response.

The early-response gene product IEX-1 (also known as IER3) was recently found to interact with the anti-apoptotic Bcl-2 family member, myeloid cell leukemia-1 (Mcl-1). In this study we show that this interaction specifically and timely controls the accumulation of Mcl-1 in the nucleus in response to DNA damage. The IEX-1 protein is rapidly induced by γ-irradiation, genotoxic agents or replication inhibitors, in a way dependent on ataxia telangiectasia mutated (ATM) activity and is necessary for Mcl-1 nuclear translocation. Conversely, IEX-1 protein proteasomal degradation triggers the return of Mcl-1 to the cytosol. IEX-1 and Mcl-1 are integral components of the DNA damage response. Loss of IEX-1 or Mcl-1 leads to genomic instability and increased sensitivity to genotoxic and replicative stresses. The two proteins cooperate to maintain Chk1 activation and G2 checkpoint arrest. Mcl-1 nuclear translocation may foster checkpoint and improve the tumor resistance to DNA damage-based cancer therapies. Deciphering the pathways involved in IEX-1 degradation should lead to the discovery of new therapeutic targets to increase sensitivity of tumor cells to chemotherapy.