US researchers have identified 26 genes that are frequently mutated in people who develop adenocarcinoma, the most common form of lung cancer, a discovery that could further lead to individualized therapies to fight the disease.

Lung cancer is the number one killer worldwide, accounting for 1 million deaths annually. Adenocarcinoma accounts for around 40 percent of cases of lung cancer. About 90 percent of those who develop lung cancer are smokers and former smokers and about 10 percent non-smokers.

In the United States, lung cancer kills 150,000 each year. Also, it is estimated that 215,020 men and women will be diagnosed with lung cancer this year, according to the National Cancer Institute. The average 5-year survival rate currently is about 15 percent, with survival being longest among people whose cancer has been detected early. The most common symptoms are shortness of breath, coughing with or without blood and weight loss.

To identify the genes involved in adenocarcinoma, the researchers who are members of the Tumor Sequencing Project (a consortium of scientists from several universities) compared samples of lung cancer tissue to non-cancerous tissue donated by 188 patients with lung adenocarcinoma. The Tumor Sequencing Project has as goal to assemble a genome-wide catalog of all mutations involved in the lung disease.

The researchers screened for genetic mistakes in 623 genes that were already known to be linked to other types of cancers.

Previously, 10 gene mutations had been linked to lung cancer -- and only five of them were known to be mutated at high frequency.

Some genes involved in adenocarcinoma were some also implicated in a number of other cancers such as: Retinoblastoma 1, linked to a childhood eye cancer; Neurofibromatosis 1, linked to a rare genetic disorder of uncontrolled nerve tissue; another with a mouthful of a name -- Ataxia Telengiectasia Mutated -- linked to some leukemias and lymphoma as well as a rare neurological childhood disorder.

The researchers also discovered differences between cancers in people with significant histories of smoking, and those who hadn’t smoked but still got lung cancer. Tumors in smokers contained many more genetic mutations – as many as 49, compared with just five in the tumors of nonsmokers.

Identifying these genes, “we should be able to develop much more effective chemo [chemotherapy] drugs, including drugs that also provide for a much more improved quality of life for the patients,” senior co-author Richard Wilson of Washington University School of Medicine in Saint Louis, Missouri.

"We think that our study may achieve a real impact on the cure of lung cancer patients," Dr. Matthew Meyerson of the Broad Institute of Massachusetts Institute of Technology and Harvard University said.

The study funded by the National Human Genome Research Institute of the National Institutes of Health (NIH) was published in the October 23 issue of the journal Nature.