ELEVATION OF ACID GLYCOSIDASE ACTIVITIES IN THYROID AND GASTRIC TUMORS

Numerous investigators have suggested that cell glycoconjugates are mo dified by the development of cancer and the progression of this to a m alignant form. Accordingly, in the present work, beta-D-galactosidase, alpha-L-fucosidase, beta-N-acetyl-n-glucosaminidase and beta-N-acetyl -D-galactosaminidase activities were studied in human thyroid and gast ric tumours. Samples were obtained from human gastric mucosa and thyro id gland tumours together with a part of the surrounding normal tissue (control). Enzyme activity was determined spectrophotometrically base d on the release of p-nitrophenol from suitable p-nitrophenyl-derivati ve substrates. Results showed that beta-D-galactosidase, alpha-L-fucos idase, beta-N-acetyl-D-glucosaminidase and beta-N-acetyl-D-galactosami nidase activities were detected in tumour and control samples from thy roid and gastric tissues. The gastric mucosa also showed alpha-L-manno sidase activity. The specific activities of these glycosidases were hi gher (two- or three-fold) in tumour tissues as compared with their con trols. beta-D-galactosidase, beta-N-acetyl-D-glucosaminidase and beta- N-acetyl-D-galactosaminidase activities from thyroid and gastric tumou rs showed a significant increase in V-max as compared with their respe ctive controls (P < 0.05 or P < 0.001). Thyroid alpha-L-fucosidase act ivity showed a statistically and significantly increased affinity (low er K-m) in tumour samples as compared to normal tissue. In conclusion both gastric and thyroid tumours showed enhanced glycosidase activity as compared with enzyme activity observed in normal tissue. These resu lts are in agreement with the notion of a markedly raised degradation within lysosomes of tumour cells. (C) 1996 Elsevier Science Ltd