472

ATM

ATM serine/threonine kinase;ATM;ATM serine/threonine kinase

A-T mutated|AT mutated|TEL1, telomere maintenance 1, homolog|ataxia telangiectasia mutated|serine-protein kinase ATM

11q22-q23

protein-coding

The DNA damage response (DDR) is critical for the maintenance of genetic stability and serves as an anti-cancer barrier during early tumorigenesis. However, the role of the DDR in tumor progression and metastasis is less known. Here, we demonstrate that the ATM kinase, one of the critical DDR elements, is hyperactive in late stage breast tumor tissues with lymph-node metastasis and this hyperactivity correlates with elevated expression of the epithelial-mesenchymal transition marker, Snail. At the molecular level, we demonstrate that ATM regulates Snail stabilization by phosphorylation on Serine-100. Using mass spectrometry, we identified HSP90 as a critical binding protein of Snail in response to DNA damage. HSP90 binds to and stabilizes phosphorylated Snail. We further provide in vitro and in vivo evidence that activation of ATM-mediated Snail phosphorylation promotes tumor invasion and metastasis. Finally, we demonstrate that Snail Serine-100 phosphorylation is elevated in breast cancer tissues with lymph-node metastasis, indicating clinical significance of the ATM-Snail pathway. Together, our findings provide strong evidence that the ATM-Snail pathway promotes tumor metastasis, highlighting a previously undescribed role of the DDR in tumor invasion and metastasis.

Many studies have revealed the ATM alterations involved in cancer development and progression. In order to elucidate ATM deficiency in advanced GC and its clinical significance, a total of 20 exons of ATM gene, including frequently reported variations, were screened in 40 advanced primary GC and matched normal tissues using denaturing high performance liquid chromatography (DHPLC) and DNA sequencing analysis. Furthermore, ATM mRNA level was analyzed using Real-time RT-PCR and in situ hybridization, and protein expression and phosphorylation at Ser1981 were measured by immunohistochemical assessment in tissue microarray of GC. Five variants were identified in 6 of 40 cases (15%), but no hot spot of variation was detected. However, decreased expression and phosphorylation of ATM were consistently presented in tumors. In a cohort of 70 GC samples, low level of phosphorylated ATM was significantly correlated with poor differentiation, lymph node metastasis and poor 5-year survival (P<0.05). These results indicated that ATM phosphorylation status might be a prognostic marker for individual therapy in advanced GC patients.

PURPOSE: Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are rare group of tumors with a wide spectrum of clinical behavior. However, there are no known clinically relevant biomarkers to predict metastasis. EXPERIMENTAL DESIGN: To investigate differential gene expression signatures of metastatic vs non-metastatic NETs, we studied cell cycle regulatory genes in 19 metastatic and 22 non-metastatic colorectal NETs by PCR arrays. Immunohistochemistry (IHC) and quantitative real-time RT-PCR were performed to verify the results and another set of 38 GEP-NETs were further studied for validation. RESULTS: We first delineated six candidate genes for metastasis including ATM, CCND2, RBL2, CDKN3, CCNB1, and GTSE1. ATM was negatively correlated with metastatic NETs (p<0.001) with more than 2-fold change compared to non-metastatic NETs. Overexpression of ATM protein by IHC was strongly correlated with high ATM mRNA levels and low Ki-67 labeling index. Patients with ATM-negativity by IHC showed significantly decreased overall survival than patients with ATM-positivity (median OS, metastatic vs non-metastatic NETs; 2.7 years vs not reached; p = 0.003) and 85.7% of metastatic NETs were ATM-negative. In another validation set of GEP-NETs, decreased mRNA of ATM gene was associated with metastasis and remained significant (p = 0.023). CONCLUSIONS: ATM down-regulation was strongly associated with metastatic NETs when compared with non-metastatic NETs and ATM may be a potential predictive marker for metastasis as well as a novel target in metastatic GEP-NETs.