Iron-Bound Lipocalin-2 Protects Renal Cell Carcinoma from Ferroptosis.
Julia K MeierMatthias SchnetzSusanne BeckTobias SchmidMonica DominguezSanela KalinovicAndreas DaiberBernhard BrüneMichaela JungPublished in: Metabolites (2021)
While the importance of the iron-load of lipocalin-2 (Lcn-2) in promoting tumor progression is widely appreciated, underlying molecular mechanisms largely remain elusive. Considering its role as an iron-transporter, we aimed at clarifying iron-loaded, holo-Lcn-2 (hLcn-2)-dependent signaling pathways in affecting renal cancer cell viability. Applying RNA sequencing analysis in renal CAKI1 tumor cells to explore highly upregulated molecular signatures in response to hLcn-2, we identified a cluster of genes (SLC7A11, GCLM, GLS), which are implicated in regulating ferroptosis. Indeed, hLcn-2-stimulated cells are protected from erastin-induced ferroptosis. We also noticed a rapid increase in reactive oxygen species (ROS) with subsequent activation of the antioxidant Nrf2 pathway. However, knocking down Nrf2 by siRNA was not sufficient to induce erastin-dependent ferroptotic cell death in hLcn-2-stimulated tumor cells. In contrast, preventing oxidative stress through N-acetyl-l-cysteine (NAC) supplementation was still able to induce erastin-dependent ferroptotic cell death in hLcn-2-stimulated tumor cells. Besides an oxidative stress response, we noticed activation of the integrated stress response (ISR), shown by enhanced phosphorylation of eIF-2α and induction of ATF4 after hLcn-2 addition. ATF4 knockdown as well as inhibition of the ISR sensitized hLcn-2-treated renal tumor cells to ferroptosis, thus linking the ISR to pro-tumor characteristics of hLcn-2. Our study provides mechanistic details to better understand tumor pro-survival pathways initiated by iron-loaded Lcn-2.
Keyphrases
- cell death
- cell cycle arrest
- oxidative stress
- induced apoptosis
- iron deficiency
- reactive oxygen species
- transcription factor
- diabetic rats
- drug delivery
- renal cell carcinoma
- cancer therapy
- anti inflammatory
- endoplasmic reticulum stress
- signaling pathway
- poor prognosis
- genome wide
- single cell
- computed tomography
- ischemia reperfusion injury
- gene expression
- long non coding rna
- wound healing
- cell proliferation
- squamous cell carcinoma
- magnetic resonance imaging
- epithelial mesenchymal transition
- newly diagnosed
- single molecule
- protein kinase
- sensitive detection
- hyaluronic acid
- data analysis
- genome wide analysis