G1P3 (IFI6), a mitochondrial localised antiapoptotic protein, promotes metastatic potential of breast cancer cells through mtROS

Anne Davenport,Ashjan Khalel,Venugopalan Cheriyath,Jaspreet Kaur,Nobel Chowdhury,Lalitha Gaddipati

doi:10.1038/s41416-018-0137-3

Abstract

BackgroundRedox deregulations are ubiquitous in cancer cells. However, the role of mitochondrial redox deregulation in metastasis remains unclear. In breast cancer, upregulation of mitochondrial antiapoptotic protein G1P3 (IFI6) was associated with poor distance metastasis-free survival (DMFS). Therefore, we tested the hypothesis that G1P3-induced mitochondrial redox deregulation confers metastatic potentials in breast cancer cells.MethodsCell migration and invasion assays; confocal and immunofluorescence microscopy; and Illumina HumanHT-12 BeadChip to assess gene expression.ResultsConsequent to its localisation on inner-mitochondrial membrane, mtROS were higher in G1P3-expressing cells (MCF-7G1P3). G1P3-overexpressing cells migrated and invaded faster than the vector controls with increased number of filopodia and F-actin bundles (p ≤ 0.05). mtROS suppression with H2O2 scavengers and mitochondrial-specific antioxidants significantly decreased migratory structures and reversed G1P3-induced migration and invasion (p ≤ 0.05). Knocking down G1P3 decreased both migration and migratory structures in MCF-7G1P3 cells. Moreover, gene networks involved in redox regulation, metastasis and actin remodelling were upregulated in MCF-7G1P3 cells.ConclusionsG1P3-induced mtROS have a direct role in migratory structure formation and nuclear gene expression to promote breast cancer cell metastasis. Therefore, interrupting mitochondrial functions of G1P3 may improve clinical outcomes in breast cancer patients.

Highlights

G1P3 (ISG 6–16), one of the interferon (IFN)-stimulated genes (ISGs), was reported as antiapoptotic in myeloma, gastric and breast cancers.[1,2,3,4] It belongs to the FAM14 protein family and is localised in mitochondria.[2, 3, 5, 6] In G1P3-overexpressing cells, preservation of mitochondrial membrane potential (ΔΨ) was suggested to antagonise TRAIL, IFNs- and chemotherapeutic-induced intrinsic apoptosis.[6]
Distant metastasis-free survival (DMFS) is reduced in breast cancer patients with high G1P3 expression We previously reported the association between elevated G1P3 expression and poor relapse free (RFS) and overall survival (OS) in ER+ breast cancer patients.[3]
Analyses of the KM plot data sets identified a significant association between high G1P3 expression and poor distance metastasis-free survival (DMFS) in breast cancer with a hazard ratio (HR) of 1.31, p ≤ 0.05 (Fig. 1a, left panel)

Summary

Introduction

G1P3 (ISG 6–16), one of the interferon (IFN)-stimulated genes (ISGs), was reported as antiapoptotic in myeloma, gastric and breast cancers.[1,2,3,4] It belongs to the FAM14 protein family and is localised in mitochondria.[2, 3, 5, 6] In G1P3-overexpressing cells, preservation of mitochondrial membrane potential (ΔΨ) was suggested to antagonise TRAIL-, IFNs- and chemotherapeutic-induced intrinsic apoptosis.[6]. Redox deregulations are ubiquitous in cancer cells. The role of mitochondrial redox deregulation in metastasis remains unclear. We tested the hypothesis that G1P3-induced mitochondrial redox deregulation confers metastatic potentials in breast cancer cells. METHODS: Cell migration and invasion assays; confocal and immunofluorescence microscopy; and Illumina HumanHT-12 BeadChip to assess gene expression. RESULTS: Consequent to its localisation on inner-mitochondrial membrane, mtROS were higher in G1P3-expressing cells (MCF-7G1P3). MtROS suppression with H2O2 scavengers and mitochondrial-specific antioxidants significantly decreased migratory structures and reversed G1P3-induced migration and invasion (p ≤ 0.05). Knocking down G1P3 decreased both migration and migratory structures in MCF-7G1P3 cells. Gene networks involved in redox regulation, metastasis and actin remodelling were upregulated in MCF-7G1P3 cells. CONCLUSIONS: G1P3-induced mtROS have a direct role in migratory structure formation and nuclear gene expression to promote breast cancer cell metastasis. Interrupting mitochondrial functions of G1P3 may improve clinical outcomes in breast cancer patients

Methods

Results

Conclusion