SCIENTISTS say a vaccine for human lung cancers may be ready soon, allowing a therapeutic cure for the disease. Lung cancer is characterised by an abnormal production of hormones, particularly the human chorionic gonadotropin (HCG). Malignancy is indicated by high lev els of HCG and successful surgery in lung cancer is usually marked by low levels of the hormone.

G P Talwar, director of the National Institute of Immunology, New Delhi, his colleague Sanjeev Kumar and Debajit K Biswas from the Harvard School of Dental Medicine in Boston conducted tests on mice using a serum containing anti-HCG antibodies and found it reduced the levels of the hormone (journal of the National Cancer Institute, Vol 84, No 1). The experiments were conducted on a cultured cell line that secretes large amounts of a sub-unit of HCG. The cultured cell unit induced tumour growth in the mice.

When the antibody serum was administered, the scientists found tumour growth was inhibited and prevented. Tests confirmed that the reducing effect was caused by the antibody alone. Experiments also showed the withdrawal of the antibody led to renewed tumour growth. Another confirmation of the specificity of the antibody treatment was its ineffectiveness when administered to combat tumour growth induced by-non-HCG producing tumour cells.

The HCG hormone is also synthesized during the early stages of pregnancy. Vaccines that induce the formation of anti-HCG antibodies are currently under clinical trials studying their antifertility activity. The scientists say if a role for the HCG sub-unit in tumour formation is established, a similar therapeutic approach for the treatment of lung cancer may be feasible in the near future.