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PINK1-deficiency facilitates mitochondrial iron accumulation and colon tumorigenesis
Mariella Arcos1, Lavanya Goodla1, Hyeoncheol Kim1
1Department of Biochemistry and Molecular Biology, University of New Mexico, Albuquerque, NM, USA.
Abstract:
Mitophagy, the process by which cells eliminate damaged mitochondria, is mediated by PINK1 (PTEN induced kinase 1). Our recent research indicates that PINK1 functions as a tumor suppressor in colorectal cancer by regulating cellular metabolism. Interestingly, PINK1 ablation activated the NLRP3 (NLR family pyrin domain containing 3) inflammasome, releasing IL1B (interleukin 1 beta). However, inhibiting the NLRP3-IL1B signaling pathway with an IL1R (interleukin 1 receptor) antagonist or NLRP3 inhibitor did not hinder colon tumor growth after PINK1 loss. To identify druggable targets in PINK1-deficient tumors, ribonucleic acid sequencing analysis was performed on colon tumors from pink1 knockout and wild-type mice. Gene Set Enrichment Analysis highlighted the enrichment of iron ion transmembrane transporter activity. Subsequent qualitative polymerase chain reaction and western blot analysis revealed an increase in mitochondrial iron transporters, including mitochondrial calcium uniporter, in PINK1-deficient colon tumor cells and tissues. Live-cell iron staining demonstrated elevated cellular and mitochondrial iron levels in PINK1-deficient cells. Clinically used drugs deferiprone and minocycline reduced mitochondrial iron and superoxide levels, resulting in decreased colon tumor cell growth in vitro and in vivo. Manipulating the mitochondrial iron uptake protein MCU (mitochondrial calcium uniporter) also affected cell and xenograft tumor growth. This study suggests that therapies aimed at reducing mitochondrial iron levels may effectively inhibit colon tumor growth, particularly in patients with low PINK1 expression.Abbreviation: ANOVA: analysis of variance; APC: adenomatous polyposis coli; cAMP: cyclic adenosine monophosphate; CDX2: caudal type homeobox 2; CGAS: cyclic GMP-AMP synthase; CRC: colorectal cancer; DNA: deoxyribonucleic acid; DFP: deferiprone; DMEM: Dulbecco's modified Eagle medium; DSS: dextran sodium sulfate; ERT2-Cre: Cre recombinase fused to a triple mutant form of the human estrogen receptor; EV: empty vector; GLB: glybenclamide/glyburide; H&E: hematoxylin and eosin; ICP-MS: inductively coupled plasma mass spectrometer; IL1B: interleukin 1 beta; kDa: kilodalton; MCU: mitochondrial calcium uniporter; MKI67: marker of proliferation Ki-67; mRNA: messenger ribonucleic acid; MTT: 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide; NLRP3: NLR family pyrin domain containing 3; OE: overexpression; PBS: phosphate-buffered saline; p-CREB: phosphorylated cAMP responsive element binding protein; PINK1: PTEN induced kinase 1; p-PRKAA/AMPK: phosphorylated protein kinase AMP-activated catalytic subunit alpha; qPCR: qualitative polymerase chain reaction; RNA-seq: ribonucleic acid sequencing; ROS: reactive oxygen species; sg: single guide; sh: short hairpin; SLC25A28: solute carrier family 25 member 28; SLC25A37/MFRN: solute carrier family 25 member 37; STING1: stimulator of interferon response cGAMP interactor 1; TP53/p53: tumor protein p53; TUBA: tubulin alpha; µL: microliter; µm: micrometer; µM: micromolar; mm: millimeter.
Insights
PTEN induced kinase 1 (PINK1) acts as a tumor suppressor in colorectal cancer. Loss of PINK1 increases mitochondrial iron, driving tumor growth. Therapies targeting mitochondrial iron show promise for treating colon tumors with low PINK1 expression.
Area of Science:
- Mitochondrial biology
- Cancer research
- Cellular metabolism
Background:
- PTEN induced kinase 1 (PINK1) mediates mitophagy and acts as a tumor suppressor in colorectal cancer (CRC).
- PINK1 deficiency activates the NLRP3 inflammasome, but inhibiting this pathway does not affect tumor growth.
- This suggests alternative mechanisms driving tumor progression in the absence of PINK1.
Purpose of the Study:
- To identify druggable targets in PINK1-deficient colon tumors.
- To investigate the role of cellular metabolism and iron transport in PINK1-deficient CRC.
- To evaluate the therapeutic potential of targeting mitochondrial iron levels.
Main Methods:
- Ribonucleic acid sequencing (RNA-seq) and Gene Set Enrichment Analysis (GSEA) on tumors from PINK1 knockout and wild-type mice.
- Qualitative polymerase chain reaction (qPCR) and western blot analysis to assess mitochondrial iron transporters.
- Live-cell iron staining, in vitro and in vivo cell growth assays, and xenograft studies.
Main Results:
- RNA-seq revealed enrichment of iron ion transmembrane transporter activity in PINK1-deficient tumors.
- Increased expression of mitochondrial iron transporters, including mitochondrial calcium uniporter (MCU), was observed.
- Elevated cellular and mitochondrial iron levels were detected in PINK1-deficient cells.
- Deferiprone and minocycline reduced mitochondrial iron and superoxide, inhibiting tumor cell growth.
- Manipulation of MCU affected tumor growth.
Conclusions:
- PINK1 deficiency leads to increased mitochondrial iron accumulation in colorectal cancer.
- Targeting mitochondrial iron levels with drugs like deferiprone or minocycline can inhibit colon tumor growth.
- Therapies reducing mitochondrial iron may be effective for patients with low PINK1 expression.
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