21 January 2011
Patients with lung cancer have elevated levels of a specific protein in their blood that could be used as a biomarker for the disease, say scientists from South Korea.
Je-Yoel Cho from Kyungpook National University and colleagues saw that levels of the beta chain form of haptoglobin - a protein produced by the liver when disease is present - increased in blood samples when lung cancer cells were present.
Among cancer types, lung cancer frequently ranks at the top in both incidence and mortality, according to the World Health Organisation. The discovery of novel lung cancer specific biomarkers - substances in the blood whose levels indicate the presence and extent of the disease -is important for early detection. Current techniques to detect cancer aren't able to give an early diagnosis.
High levels of the beta chain form of haptoglobin - a protein produced when disease is present - could be an indicator of lung cancer
Cho and his team identified haptoglobin in human blood serum samples and compared levels of the protein in lung cancer patients' samples with those of healthy people. They found that the levels of one particular form - the alpha form - of the protein were the same in all samples, but the levels of the beta form were four-fold higher in lung cancer patients.
When they compared lung cancer blood samples to samples from other cancer types, such as breast cancer, they saw that the beta form levels in the other cancer types were similar to those in the healthy samples. This data suggests that the beta chain increase could be an indicator of lung cancer, say Cho and the team.
One explanation for the elevated levels of the beta chain in lung cancer patients is that, unlike the alpha chain, it binds to glucose molecules in lung cancer blood sera, say the researchers. 'It's possible that the glycosylated haptoglobin beta chainis more stable and has a longer half-life in lung cancer sera,' they said.
'Since haptoglobin is an inflammatory response protein,'says Paul Huang from the Institute of Cancer Research, London, UK, 'it would be interesting to establish if assessing levels of theprotein hasadditional prognostic value to patient outcome in response to treatment with conventional and targeted therapy.'
Cho aims to continue looking for new lung cancer biomarkers using lung cancer tissue, primary cells, or their secretory proteins, which can be detected in sera or sputum.
'A biomarker panel incorporating the haptoglobinbetachain together with other previously identified lung cancer biomarkers may lead to a more powerful diagnostic test,' says Huang.'This could allow scientists to distinguish different forms and stages of lung cancer using serum measurements.'