Doctors at the National Cancer Institute in Bethesda reveal more about the origins of lung cancer in people who have never smoked.
In France, theof the lung is the deadliest, although not the most common. The the risk of declaring it increases tenfold, on average around 66 years old. Non-smokers can also be affected. An exhibition at the , atmospheric pollution or even can trigger lung cancer. The link between exposure to an environmental factor and the development of lung cancer in a lifelong non-smoker is not always established. It can appear for no apparent reason.
A US-Canadian team carried out a genomic analysis of cancerous lung tissue taken from people who have never used tobacco. Doctors were thus able to identify three subtypes ofspecific to non-smokers and their origins. .
“Piano”, “half strong” and “strong”
In total, 232 cancerous tissue samples were analyzed. The doctors carried out aof whole (whole genome sequencing) cancer cells and compared the mutational signatures between diseased and healthy tissues. Three subtypes of lung cancer then emerged, classified according to their “noise”, ie the number of changes in the genome.
First, the mutational signatures identified do not match those caused byor passive smoking. They are of origins , due to the natural process of mutation or to the oxidative stress that all cells undergo. To spin the musical metaphor, the three subtypes have been named “piano”, “mezzo forte” and “forte”. The “piano” subtype, the majority in the samples analyzed, is characterized by the presence of several mutated like UAB1 or KRAS, and slow growth.
The second subtype “mezzo forte” presents an amplification of certain genes, that is to say the presence of a copy in addition to said gene, and mutations in the EGFR gene which codes for the EGF receptor. (epidemial growth factor). The mutation of this receptor is associated with several cancers, including that of the lung and. Deregulated, it promotes uncontrolled proliferation of cells. Lung cancers of the “mezzo forte” type grow rapidly. Finally the subtype “strong” is characterized by the . In , the entire genome is duplicated (whole genome doubling). They are no longer (two copies of each gene), but polyploid with at least three copies of the genome.
« We are at the beginning of our understanding of how these tumors evolve. This analysis shows that there is heterogeneity, or diversity, in lung cancers in those who have never smoked »,of National cancer institute of Bethesda (United States) and principal investigator of this study. This research could improve cancer management in non-smokers.