Cigarette smoke and decreased DNA repair by Xeroderma Pigmentosum Group C use a double hit mechanism for epithelial cell lung carcinogenesis

Area of Science:

• Molecular Biology
• Genetics
• Oncology

Background:

• Non-small cell lung cancer (NSCLC) development involves environmental and genetic factors, including DNA repair deficiencies.
• Compromised DNA repair, particularly Nucleotide Excision Repair (NER), is implicated in lung tumorigenesis and diseases like chronic obstructive lung disease (COPD).
• The role of the NER protein Xeroderma Pigmentosum Group C (XPC) in this context requires further elucidation.

Purpose of the Study:

• To investigate the interplay between cigarette smoke, DNA damage, and repair mechanisms, focusing on the XPC protein in NSCLC.
• To determine how XPC deficiency affects cellular responses to cigarette smoke in both non-cancerous and cancerous lung cells.
• To explore the role of XPC in chromosomal stability during lung tumorigenesis.

Main Methods:

• Quantitative analysis of XPC mRNA expression in NSCLC tissues versus matched non-cancerous lung tissues.
• Experimental exposure of non-cancerous bronchial epithelial cells and lung cancer cells to cigarette smoke.
• Assessment of NER activity, total DNA damage, apoptosis, and chromosomal instability in response to cigarette smoke and varying XPC levels.

Main Results:

• XPC mRNA expression was decreased in most NSCLCs compared to non-cancerous lung tissue.
• In non-cancerous cells, cigarette smoke reduced NER, increased DNA damage and apoptosis, effects amplified by XPC deficiency.
• Lung cancer cells showed greater resilience to cigarette smoke, with less reliance on XPC for survival and no protection against chromosomal instability.

Conclusions:

• A 'double hit' mechanism involving reduced XPC expression and cigarette smoke exposure contributes to NSCLC.
• This mechanism leads to the loss of non-malignant epithelial cells (as seen in COPD) and facilitates the transition to NSCLC via altered DNA damage responses.
• XPC plays a protective role against chromosomal instability in benign bronchial cells, but this function is lost in lung cancer cells.