Loss of Notch1 predisposes oro-esophageal epithelium to tumorigenesis

Area of Science:

• Oncology
• Developmental Biology
• Cell Biology

Background:

• Notch signaling is crucial for cell fate and stem cell renewal.
• Notch1-inactivating mutations are common in skin and oro-esophageal cancers, suggesting a tumor suppressor role.
• Oro-esophageal tumors in mice induced by 4-nitroquinoline-1-oxide (4-NQO) mimic human cancer, showing reduced Notch1 expression.

Purpose of the Study:

• To investigate the specific role of Notch1 deficiency in oro-esophageal tumorigenesis using a mouse model.
• To determine if Notch1-deficient squamous epithelium is more susceptible to tumor development.

Main Methods:

• Generated Notch1 conditional knockout (N1cKO) mice with Notch1 disruption in squamous epithelium.
• Induced tongue and esophageal tumors using 4-NQO in N1cKO and wild-type mice.
• Analyzed tumor onset, incidence, and cellular changes, including telomere length and TERT expression.

Main Results:

• N1cKO mice showed normal epithelial development but increased susceptibility to skin tumors.
• 4-NQO treatment led to earlier tumor onset in N1cKO mice, with tumors originating from Notch1-negative epithelium.
• Notch1 deficiency accelerated age-related telomere erosion in basal cells, linked to TERT regulation.

Conclusions:

• Notch1 deficiency predisposes squamous epithelium to tumor development, despite normal initial formation.
• Accelerated telomere erosion is a key mechanism by which Notch1 deficiency promotes tumorigenesis.
• These findings highlight Notch1's role as a tumor suppressor in oro-esophageal tissues.