ATM kinase sustains breast cancer stem-like cells by promoting ATG4C expression and autophagy
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Martina Antonelli1,2, Flavie Strappazzon1, Ivan Arisi3, Rossella Brandi3, Mara D’Onofrio3, Manolo Sambucci4, Gwenola Manic2, Ilio Vitale2,5, Daniela Barilà1,2, Venturina Stagni1
1Instituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Fondazione Santa Lucia, Rome, Italy
2Department of Biology, University of Rome ‘Tor Vergata’, Rome, Italy
3Genomics Facility, European Brain Research Institute (EBRI) ‘Rita Levi-Montalcini’, Rome, Italy
4Neuroimmunology Unit, Fondazione Santa Lucia, IRCCS, Rome, Italy
5Regina Elena National Cancer Center Institute, Rome, Italy
Venturina Stagni, email: [email protected]
Daniela Barilà, email: [email protected]
Keywords: ATM kinase, breast cancer stem cells (BCSCs), mammospheres, autophagy, ATG4
Received: July 05, 2016 Accepted: January 23, 2017 Published: February 20, 2017
The efficacy of Ataxia-Telangiectasia Mutated (ATM) kinase signalling inhibition in cancer therapy is tempered by the identification of new emerging functions of ATM, which suggests that the role of this protein in cancer progression is complex. We recently demonstrated that this tumor suppressor gene could act as tumor promoting factor in HER2 (Human Epidermal Growth Factor Receptor 2) positive breast cancer. Herein we put in evidence that ATM expression sustains the proportion of cells with a stem-like phenotype, measured as the capability to form mammospheres, independently of HER2 expression levels. Transcriptomic analyses revealed that, in mammospheres, ATM modulates the expression of cell cycle-, DNA repair- and autophagy-related genes. Among these, the silencing of the autophagic gene, autophagy related 4C cysteine peptidase (ATG4C), impairs mammosphere formation similarly to ATM depletion. Conversely, ATG4C ectopic expression in cells silenced for ATM expression, rescues mammospheres growth. Finally, tumor array analyses, performed using public data, identify a significant correlation between ATM and ATG4C expression levels in all human breast cancer subtypes, except for the basal-like one.
Overall, we uncover a new connection between ATM kinase and autophagy regulation in breast cancer. We demonstrate that, in breast cancer cells, ATM and ATG4C are essential drivers of mammosphere formation, suggesting that their targeting may improve current approaches to eradicate breast cancer cells with a stem-like phenotype.
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