Opposing effects of TIGAR- and RAC1-derived ROS on Wnt-driven proliferation in the mouse intestine

Area of Science:

• Cell Biology
• Cancer Research
• Molecular Biology

Background:

• Reactive oxygen species (ROS) play complex roles in cell functions like proliferation and DNA damage, leading to conflicting therapeutic strategies in cancer.
• The precise mechanisms determining cellular ROS responses remain unclear.
• APC loss in the Wnt pathway influences ROS levels, but the net effect on proliferation is not fully understood.

Purpose of the Study:

• To investigate how ROS signaling is modulated following APC loss in a cancer model.
• To elucidate the distinct roles of RAC1 and TIGAR in controlling ROS and cell proliferation.
• To understand how the Wnt pathway integrates opposing ROS signals.

Main Methods:

• Utilized three-dimensional (3D) cell cultures and in vivo models.
• Examined the effects of Apc deletion and subsequent changes in Wnt target genes Myc, RAC1, and TIGAR.
• Manipulated ROS levels by targeting NADPH oxidase (NOX)-derived ROS and TIGAR activity.

Main Results:

• APC loss up-regulates Myc, which increases RAC1 and promotes proliferative ROS via NOX.
• APC loss also increases TIGAR, a ROS-limiting enzyme.
• TIGAR deletion exacerbated ROS damage and inhibited proliferation, while limiting damaging ROS suppressed these effects.
• Loss of TIGAR and RAC1 synergistically suppressed intestinal proliferation after APC loss.

Conclusions:

• The pro- and anti-proliferative effects of ROS can be independently controlled within the same cell.
• The Wnt pathway integrates distinct ROS signals through targets like RAC1 and TIGAR to regulate cell proliferation.
• This provides a framework for understanding ROS dynamics in cancer and developing targeted therapies.