TY - JOUR T1 - AMPK promotes Notch1 stability to potentiate hypoxia-induced breast cancer stemness and drug resistance JF - bioRxiv DO - 10.1101/458489 SP - 458489 AU - Lahiry Mohini AU - Annapoorni Rangarajan Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/11/01/458489.abstract N2 - The developmentally important Notch pathway is implicated in the maintenance of cancer stem/progenitor cells in tumor hypoxia. Yet, the mechanisms that lead to Notch activation in hypoxia are not clear. AMP-activated protein kinase (AMPK), a major player in energy homeostasis, is activated by hypoxia. These considerations led us to investigate whether AMPK facilitates cancer progression through the Notch pathway under hypoxia. Our data revealed that activating AMPK through pharmacological agents or genetic approaches led to an increase in the levels of cleaved Notch1 protein, and Notch signaling, in invasive breast cancer cell lines. In contrast, inhibition or depletion of AMPK reduced cleaved Notch1 levels. Significantly, we show that the hypoxia-induced increase in cleaved Notch1 protein levels requires AMPK activation. Furthermore, we show that AMPK modulates cleaved Notch1 protein levels by increasing its stability. Mechanistically, we identified a reduction in interaction between Notch1 and Itch/AIP4, a known ubiquitin ligase for Notch, upon AMPK activation, thus bringing about reduced degradation of cleaved Notch1. This interaction was also disrupted under hypoxia and was influenced by AMPK modulation. Further, we identified AMPK-mediated positive regulation of Fyn activity in turn regulates Itch phosphorylation and its interaction with Notch1. Finally, we observed that inhibition of AMPK under hypoxia affected self-renewal and drug resistance adversely, suggesting that hypoxia-induced AMPK activation might potentiate breast cancer aggressiveness through the Notch pathway. Furthermore, high grade breast cancers that commonly show hypoxic regions revealed an association between AMPK activity and Notch signalling. Altogether, our study sheds light on context-specific oncogenic role of AMPK by reinforcing Notch1 signaling under hypoxia to facilitate breast cancer progression.Financial support This work was majorly supported by grants from the Wellcome Trust-DBT India Alliance (IA) Senior Research Fellowship (500112/Z/09/Z) to AR. ER -