ROS-generating NADPH oxidase NOX4 is a critical mediator in oncogenic H-Ras-induced DNA damage and subsequent senescence

Area of Science:

• Cellular biology
• Molecular oncology
• Oxidative stress

Background:

• Oncogene activation, such as Ras, can induce DNA-damage response (DDR) and senescence.
• Reactive oxygen species (ROS) production is implicated in oncogene-induced DDR, but the precise molecular links remain unclear.
• NADPH oxidases (NOX) are key sources of ROS, with NOX4 being a potential candidate in this process.

Purpose of the Study:

• To investigate the role of NADPH oxidase system, specifically NOX4, in mediating H-RasV12 oncogene-induced DNA-damage response and senescence.
• To elucidate the molecular mechanisms connecting H-RasV12, ROS production, and DDR.

Main Methods:

• Utilized small interference RNA (siRNA) to knock down NADPH oxidase components.
• Assessed DNA damage using γ-H2A.X foci analysis.
• Quantified hydrogen peroxide (H2O2) levels using the HyPer probe.
• Analyzed senescence markers including senescence-associated heterochromatin foci, PML bodies, HP1β foci, and p21 expression.
• Investigated the regulation of CDC6 expression.

Main Results:

• H-RasV12 positively regulates the NOX4-p22(phox) system, leading to increased H2O2 production.
• Knockdown of NOX4 significantly reduced H-RasV12-induced DNA damage.
• Increased H2O2 levels were detected in the nucleus, correlating with NOX4 perinuclear localization.
• NOX4 inactivation abrogated H-RasV12-mediated regulation of CDC6 expression, impacting DNA replication.
• Downregulation of NOX4 decreased H-RasV12-induced senescence markers.

Conclusions:

• NADPH oxidase NOX4 is a critical mediator of oncogenic H-RasV12-induced DNA-damage response.
• NOX4-dependent ROS production plays a key role in initiating DDR and subsequent senescence following oncogene activation.
• The NOX4-ROS pathway is essential for H-RasV12-driven cellular senescence.