Sun exposure causes somatic second-hit mutations and angiofibroma development in tuberous sclerosis complex

Area of Science:

• Genetics
• Dermatology
• Oncology

Background:

• Tuberous sclerosis complex (TSC) involves tumor formation due to mutations in TSC1 or TSC2 tumor suppressor genes.
• The mechanism of somatic second-hit mutations in TSC tumors remains unclear.
• Understanding these mutations is crucial for managing TSC-related growths.

Purpose of the Study:

• To investigate the genetic basis of somatic second-hit events in TSC skin tumors.
• To identify the specific mutations and their origins in TSC-associated lesions.
• To explore the potential role of environmental factors in TSC tumor development.

Main Methods:

• Fibroblast-like cells were cultured from 29 TSC skin tumors across 22 subjects.
• Next-generation sequencing was employed to detect germline and second-hit mutations in TSC1/TSC2.
• Analysis included assessment of mosaicism and mutation patterns in relation to tumor location.

Main Results:

• Mutations in TSC1/TSC2 were identified in 82% of subjects.
• Mosaicism for mutations was present in 44% of affected subjects.
• UV-signature mutations (CC>TT) were found in 50% of somatic point mutations, exclusively in facial angiofibromas from sun-exposed areas, suggesting independent tumor origins.

Conclusions:

• UV-induced DNA damage is implicated as a cause of second-hit mutations in TSC facial angiofibromas.
• These findings suggest that sun protection measures may help reduce the incidence and severity of TSC facial lesions.
• Targeting UV exposure could be a preventative strategy for specific TSC manifestations.