AMPK-Fyn signaling promotes Notch1 stability to potentiate hypoxia-induced breast cancer stemness and drug resistance

Abstract

SummaryHypoxia is a hall mark of solid tumor microenvironment and contributes to tumor progression and therapy failure. The developmentally important Notch pathway is implicated in cellular response of cancer cells to hypoxia. Yet, the mechanisms that potentiate Notch signaling under hypoxia are not fully understood. Hypoxia is also a stimulus for AMP-activated protein kinase (AMPK), a major cellular energy sensor. In this study, we investigated if AMPK interacts with the Notch pathway and influences the hypoxia-response of breast cancer cells. Activating AMPK with pharmacological agent or genetic approaches led to an increase in the levels of cleaved Notch1 and elevated Notch signaling in invasive breast cancer cell lines. In contrast, inhibition or depletion of AMPK reduced the amount of cleaved Notch1. Significantly, we show that the hypoxia-induced increase in cleaved Notch1 levels requires AMPK activation. Probing into the mechanism, we demonstrate that AMPK activation impairs the interaction between cleaved Notch1 and its ubiquitin ligase, Itch/AIP4 through the tyrosine kinase Fyn. Under hypoxia, the AMPK-Fyn axis promotes inhibitory phosphorylation of Itch which abrogates its interaction with substrates, thus stabilizing cleaved Notch1 by reducing its ubiquitination and degradation. We further show that inhibition of AMPK alleviates the hypoxia-triggered, Notch-mediated stemness and drug resistance phenotype. Breast cancer patient samples also showed co-expression of hypoxia/AMPK/Notch gene signature. Our work thus establishes AMPK as a key component in the adaptation of breast cancer cells to hypoxia, and proposes therapeutic inhibition of AMPK to mitigate the hypoxia-triggered aggressiveness.

Molecular pathway analysis indicates a distinct metabolic and immune phenotype in women with right-sided colon cancer

“…Notch 1 known to be essential for maintenance of normal intestinal epithelium and is activated in primary colorectal cancer (CRC) rather than metastatic colon cancer, it may therefore may be more important for early CRC development (Suman et al, 2014). It has also been shown that AMPK depletion can reduce Notch 1 levels (Mohini and Rangarajan, 2018). Although Notch1 is associated with poorer prognosis, our study may imply that Notch1 is not an important factor in RCC versus LCC outcomes.…”

Prolactin-induced AMPK stabilizes alveologenesis and lactogenesis through regulation of STAT5 signaling

“…In the absence of AMPK, there is an aberrant lobuloalveolar expansion which may drive the gland towards tumor formation, thereby supporting the role of AMPK as a metabolic tumor suppressor. However, once tumor is initiated, we and others have shown tumor-promoting roles of AMPK by enhancing breast cancer cell survival under various stress conditions (Hindupur et al, 2014; Jeon and Hay, 2015; Ng et al, 2012; Saha et al, 2018; Sundararaman et al, 2016), as well as by promoting EMT (Saxena et al, 2018) and stemness (Lahiry et al, 2020). Recent murine models have further elaborated on this dual role of AMPK in cancer (Vara-Ciruelos et al, 2020).…”

AMP-activated protein kinase promotes breast cancer stemness and drug resistance

“…We have demonstrated that the inhibition of AMPK depletes the BCSC population and increases chemosensitivity. Further, in the context of hypoxia, a study undertaken by our laboratory demonstrated that AMPK promotes breast cancer stemness by increasing Notch1 stability ( Lahiry et al, 2020 preprint). Our results on the BCSCs, taken together, support the idea that the presence of extracellular stress signals, such as nutrient or anchorage deprivation and hypoxia, can drive an AMPK-dependent adaptive state transition to a stem-like phenotype.…”