Exome Sequencing Reveals a Sparse Genomic Landscape in Kaposi Sarcoma

Area of Science:

• Oncology
• Virology
• Genetics

Background:

• Kaposi sarcoma (KS) is an aggressive cancer frequently associated with human immunodeficiency virus (HIV) and Kaposi sarcoma herpesvirus (KSHV).
• The role of the cellular genome in KS pathogenesis is not well understood.
• Understanding genetic alterations in KS may offer biological and therapeutic insights.

Purpose of the Study:

• To investigate cellular genetic alterations in Kaposi sarcoma tumors.
• To compare genetic profiles between HIV-associated and HIV-negative KS.
• To explore potential therapeutic targets based on genetic findings.

Main Methods:

• Whole-exome sequencing was performed on 78 KS tumors and matched normal skin samples from 59 adults in Uganda.
• Samples included 46 individuals with HIV-associated KS and 13 with HIV-negative KS.
• Tumor genomes were analyzed for mutations, copy number alterations, and mutational signatures.

Main Results:

• Kaposi sarcoma tumors exhibited an exceptionally low mutational burden, the lowest reported among all cancer types.
• No recurrent mutations were identified; the RTK/RAS pathway was most frequently affected.
• Mutational signatures suggested defective DNA mismatch repair and smoking; viral oncogenes are implicated as primary drivers.

Conclusions:

• Kaposi sarcoma pathogenesis is distinct from other malignancies, primarily driven by KSHV infection and viral oncogene expression.
• Cellular genetic alterations play a limited role in KS development compared to viral factors.
• Further research into viral mechanisms is crucial for understanding and treating Kaposi sarcoma.