The research team found that the Dmp1 gene, which normally works to suppress tumour formation, is non-functional in about 35 percent of human lung cancers.
"Lung cancer is one of the most lethal types of cancer and understanding more about its cause could be a first step to developing new treatments," said senior scientist Kazushi Inoue, M.D., Ph.D., an assistant professor of pathology.
Previous studies in mice found that the gene is involved in activating tumour suppressors known as p53 and Arf. The authors believe that when the Dmp1 gene isn't functional, these tumour suppressors are not available to stop tumor growth by killing cancer cells.
"No one thought it was also involved in human tumours. This was the first study to explore its involvement in human cancer," Inoue said. The authors found that deletion of one copy of Dmp1 was found in 30-40 percent of mice lung tumours as well as in human non-small-cell lung cancers. As with all human genes, there are two copies of Dmp1 - one from each parent. Even with one deleted copy, the effects of the gene are silenced.
For their study, the research team analysed 51 samples of human non-small-cell-lung cancers for Dmp1, Arf and p53 and found that the Dmp1 gene was frequently deleted. In most cases, the genes for Arf and p53 tumour suppressors were present, but the suppressors were not active. Even when just one copy of the Dmp1 gene was deleted, the function of Dmp1 was significantly decreased.
The Dmp1 gene is located on human chromosome 7q21, a region that is often deleted in human malignancies. In addition, abnormality of the p53 gene is one of the most common events in human lung cancers. "This work provides evidence that Dmp1 is a physiological regulator of the Arf-p53 pathway in humans and is primarily involved in lung cancer," Inoue said.
He said that while the research is early basic science, it represents several opportunities to understand more about lung cancer.
"We hope to learn how the gene affects outcome. It's possible that knowing which patients have the gene may be a prognostic factor for how they will respond to chemotherapy. The gene may also be a target for future drug development since high expression of Dmp1 significantly inhibited the growth of some lung cancer cells," Inoue said.
The new study is published in the journal Cancer Cell.