Hypoxia-induced reactive oxygen species mediate N-cadherin and SERPINE1 expression, EGFR signalling and motility in MDA-MB-468 breast cancer cells

Oxidative stress-induced miRNAs modulate AKT signaling and promote cellular senescence in uterine leiomyoma

Uterine leiomyomas (ULM) grow under high oxidative stress due to a hypoxic microenvironment and defects in redox metabolism. AKT is one major pathway activated by reactive oxygen species (ROS) that maintains ULM growth and survival. We previously reported that AKT inactivated by AKT inhibitors can significantly induce cellular senescence in ULM cells. Since some miRNAs are induced by AKT inhibitors in an ROS-dependent manner, we proposed that these miRNAs may modulate AKT function and cellular senescence in ULM. We therefore established ex vivo models of a three-dimensional ULM spheroid culture system to study the role of miRNAs in cellular senescence. Four miRNAs, miR-29b, miR-181a, miR-182, and miR-200c, were found to induce cellular senescence in primary ULM and myometrium spheroid cultures when stably overexpressed. miR-181a and miR-182 were found to repress AKT3 and CCND2, respectively. Correspondingly, RNAi of AKT3 or CCND2 also induced cellular senescence and G0/G1 arrest. Thus, miR-181a and miR-182 may drive cellular senescence in ULM by repressing AKT3 and CCND2 activity, respectively. We further demonstrated that senescent ULM cells can be effectively removed by BH3 mimetic ABT263, which provides a new therapeutic venue for the treatment of ULM. Our findings suggest that miRNAs are potent modulators in regulating the ROS-AKT-cell cycle axis in uterine leiomyoma.

KEY MESSAGES

A subset of oxidative stress-induced miRNAs is involved in AKT signaling in uterine leiomyoma. Overexpression of miR-181a and miR-182 resulted in cellular senescence in leiomyoma through repression of AKT3 and CCND2, respectively. Silencing of AKT3 and CCND2 drives leiomyoma cell into senescence and cycle arrest. Application of our newly developed 3D leiomyoma spheroids can provide a quick and reliable ex vivo model for cytopathologic and functional analysis. BH3 mimetics can effectively reduce the viability of miRNA-mediated senescent cells in leiomyoma.

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

BACKGROUND

Redox 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.

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-7^G1P3). 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-7^G1P3 cells. Moreover, gene networks involved in redox regulation, metastasis and actin remodelling were upregulated in MCF-7^G1P3 cells.

CONCLUSIONS

G1P3-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.