Lysosomes in cancer cells

Abstract

Lysosomal enzyme activities are often higher in tumours than in the corresponding normal cells. This is related in part to the undifferentiated state of tumour cells. Relatively high proportions of lysosomal hydrolases not sedimentable with cytoplasmic particles are often found in tumours. This is related in part to the presence of autophagosomes, which are easily disrupted by homogenization, and to autolysis. Release of hydrolases from tumour cells may facilitate penetration of normal tissues and detachment from tumours of cells that can metastasize. Regression of hormone-dependent tumours is an endocidal event in which autophagosomal digestion plays an important part. Formation of autophagosomes and other lysosomal changes frequently occur during cancer theapy. Proteases, probably acting on membrane glycoproteins, can release cells from growth control.