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Updated: Apr 17, 2026
Cigarette Smoke Exposure in Mice using a Whole-Body Inhalation System
Published on: October 22, 2020
Molecular damage and lung tumors in cigarette smoke-exposed mice
Alberto Izzotti1, Alessandra Pulliero
1Department of Health Sciences, University of Genoa, Genoa, Italy; IRCCS AOU San Martino IST, Genoa, Italy.
Abstract:
Cigarette smoke (CS) induces lung cancer through a multistep process that is now being depicted by molecular analyses. During the early phase (weeks), DNA damage occurs in nuclear and mitochondrial DNA, triggering adaptive responses activated by transient microRNA downregulation in the expression of defensive genes and proteins. During the intermediate phase (months), damaged cells are removed by apoptosis and the resulting cell loss is counteracted by a recruitment of stem cells that are highly sensitive to genotoxic damage. In parallel, microRNA downregulation becomes irreversible because of an accumulation of molecular damage in DICER. During the late phase (years), apoptosis efficacy is decreased by fragile histidine triad loss, while irreversible microRNA downregulation triggers the expression of mutated oncogenes, resulting in adenoma appearance. Furthermore, deletions occur in microRNA-encoding genes, causing carcinoma formation and uncontrolled growth. All reported pathogenic steps are required to obtain a fully developed lung cancer. This complex pathogenesis develops over a long period of time; therefore, it is difficult to induce cancer in short-living animals exposed to CS, whereas in humans there is a long latency from the start of smoke exposure to the onset of cancer.
Insights
Cigarette smoke causes lung cancer through a multistep process involving DNA damage and microRNA changes. These molecular alterations accumulate over years, leading to irreversible changes and tumor formation in humans.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Cigarette smoke (CS) is a major cause of lung cancer.
- The multistep pathogenesis of CS-induced lung cancer is complex and occurs over a long period.
- Molecular analyses are revealing the intricate processes involved in cancer development.
Purpose of the Study:
- To elucidate the molecular mechanisms and temporal stages of cigarette smoke-induced lung cancer.
- To detail the roles of DNA damage, microRNA dysregulation, and cellular responses in lung carcinogenesis.
- To explain the long latency period observed in human lung cancer development.
Main Methods:
- Molecular analyses of DNA damage and gene expression.
- Investigation of microRNA (miRNA) expression patterns.
- Study of cellular adaptive responses, apoptosis, and stem cell recruitment.
- Examination of key molecular players like DICER and fragile histidine triad (FHIT).
Main Results:
- Early phase (weeks): CS induces DNA damage and transient miRNA downregulation of defensive genes.
- Intermediate phase (months): Apoptosis removes damaged cells, stem cells are recruited, and miRNA downregulation becomes irreversible due to DICER damage.
- Late phase (years): Reduced apoptosis (FHIT loss), irreversible miRNA downregulation, oncogene activation, miRNA gene deletions lead to adenoma and carcinoma formation.
Conclusions:
- Lung cancer development from CS exposure is a lengthy, multistep process requiring sequential molecular and cellular events.
- Irreversible microRNA downregulation and accumulation of genetic damage are critical for sustained cancer growth.
- The long latency in humans is attributed to the time required for these cumulative pathogenic steps, making animal models challenging.
