Lectin staining as a predictive test for radiosensitivity of oral cancers

Owing to their specific carbohydrate binding properties, plant lectins have been used extensively as probes to study the surface architecture of transformed cells. The aim of our study was to evaluate the radiation-induced alterations in the lectin staining of tumour cells in order to see if there is any dose-effect relationship and if it has any predictive value regarding radiosensitivity. Twenty-eight patients with squamous cell carcinoma of oral cavity planned for radical radiotherapy were selected. Serial scrape smears were taken from each tumour before treatment and after the delivery of various fractions, usually 2 (7 Gy), 5 (17.5 Gy), 8 (28 Gy), and 11 (38.5 Gy). The smears were made to react with Jack Fruit Lectin (JFL) and stained with Diaminobenzedine. The nuclei were counterstained with Haematoxylin. A minimum of 100 cells from each sample was evaluated for the presence or absence of membrane staining. The results were expressed as the percentage of the total cells showing membrane staining. The mean percentage of the cells that showed lectin staining before treatment was 88.85 and after the delivery of various doses 7, 17.5, 28, and 38.5 Gy, respectively, they were 70.25 ( P <0.01), 48.46 ( P <0.001), 31.75 ( P <0.001), and 19.53 ( P <0.001). Since lectins bind to specific carbohydrate residues on the cell surface, the decrease in staining reflects the loss of these binding sites due to radiation-induced membrane damage. The different types of change and the treatment results indicate that this might prove to be a useful predictive test of radiosensitivity.