A new study has shown that it takes just 15 cigarettes to increase the risk of developing lung cancer.
The research team led by Peter Campbell of the Wellcome Trust Sanger Institute in Cambridge insists that the new discovery may lead to new drugs that target the specific changes to the gene that helps to trigger the disease
The study suggests that a person may develop one mutation for every 15 cigarettes smoked.
Using new DNA sequencing technology called "massively parallel sequencing," the researchers cracked the entire cell genome and found more than 23,000 mutations that the tumor cells had acquired.
The mutations were linked with exposure to the toxins found in cigarette smoke and had accumulated over the lifetime.
"The profile of mutations we observed [in the lung-cancer patient] is exactly that expected from tobacco, suggesting that the majority of the 23,000 we found are caused by the cocktail of chemicals found in cigarettes," the Independent quoted Campbell as saying.
"On the basis of average estimates, we can say that one mutation is fixed in the genome for every 15 cigarettes smoked," he added.
Similarly, the study conducted on patient with skin cancer showed that malignant skin cells contained changes that resulted from exposure to ultraviolet light.
"With these genome sequences, we have been able to explore deep into the past of each tumour, uncovering with remarkable clarity the imprints of these environmental mutagens [mutation-causing agents] on DNA, which occurred years before the tumour became apparent," said Professor Mike Stratton at the Sanger Institute.
The study appears in journal Nature.