N-acetylcysteine negatively regulates Notch3 and its malignant signaling

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Notch3 receptor signaling is crucial in various cancers.
• N-acetylcysteine (NAC) is an antioxidant with potential in cancer therapy.
• The precise mechanism of NAC's effect on Notch3 signaling requires elucidation.

Purpose of the Study:

• To investigate the regulatory effect of NAC on Notch3 expression and signaling in cancer cells.
• To determine the mechanism underlying NAC-mediated changes in Notch3 levels.
• To evaluate the therapeutic potential of NAC in Notch3-driven cancers.

Main Methods:

• Treatment of HeLa cells with varying concentrations and durations of NAC.
• Analysis of Notch3, N3ICD, Hes1, and HRT1 protein levels.
• Assessment of reactive oxygen species (ROS) using SOD, catalase, and NAC.
• Investigation of NAC's effect on Notch3 mRNA expression.
• Functional inhibition of lysosomal and proteasomal pathways.
• Notch3 silencing and N3ICD overexpression experiments in multiple cancer cell lines.

Main Results:

• NAC treatment led to a time- and concentration-dependent decrease in Notch3 protein levels and its downstream effectors (Hes1, HRT1) in HeLa cells.
• This effect was independent of f-secretase, glutathione, or ROS suppression by SOD and catalase.
• NAC did not alter levels of Notch1, full-length Notch3 precursor, or overexpressed N3ICD.
• NAC reduced Notch3 protein via lysosome-dependent degradation, not proteasomal degradation.
• NAC demonstrated efficacy in preventing malignant phenotypes by down-regulating Notch3 protein in various cancer cells.

Conclusions:

• NAC negatively regulates Notch3 signaling through lysosome-dependent degradation of Notch3 protein.
• NAC's mechanism of action is independent of its antioxidant properties related to ROS scavenging.
• NAC represents a potential therapeutic agent for sensitizing Notch3-expressing tumors.