DNA damage response as a candidate anti-cancer barrier in early human tumorigenesis

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Cancer evolution involves oncogenic stress, prompting cellular responses to eliminate nascent tumors.
• The exact nature of oncogenic stress and the anti-cancer barriers it induces remain unclear.
• Understanding these early cellular responses is crucial for cancer prevention and treatment.

Purpose of the Study:

• To investigate the DNA damage response in early human tumors.
• To identify the molecular pathways involved in the anti-cancer barrier during tumorigenesis.
• To determine the role of this response in preventing cancer progression.

Main Methods:

• Analysis of clinical specimens from various human tumor types (bladder, breast, lung, colon) at different stages.
• Detection of DNA damage response markers, including phosphorylated ATM, Chk2, histone H2AX, and p53.
• Induction of checkpoint responses in cultured cells expressing oncogenes.
• Genetic analyses, including genome-wide assessment of allelic imbalances.

Main Results:

• Early human tumor precursor lesions commonly express activated DNA damage response markers.
• Oncogene expression in cultured cells induced similar checkpoint responses.
• The ATR/ATM-regulated DNA damage response network was identified as active early in tumorigenesis.
• Mutations in the ATM-Chk2-p53 pathway were linked to increased proliferation, survival, and genomic instability.

Conclusions:

• An activated DNA damage response acts as an early anti-cancer barrier in human tumorigenesis.
• This network, regulated by ATR/ATM, delays or prevents cancer development.
• Compromised checkpoints, particularly involving ATM-Chk2-p53, facilitate tumor progression and genomic instability.