Ultrastructural study of the urothelial lysosomal system in patients with transitional cell carcinoma after transurethral resection and interferon therapy.

The epithelial cells of human bladder urothelium contain a prominent lysosomal system on the surface layer which involves autophagic, phagocytotic and excretory processes. The noninvolved urothelium of tumor-bearing patients, however, does not contain this well-developed lysosomal system. Interferon restores the differentiation of the urothelium. Its action on the lysosomal system, however, has not been investigated. We studied ultrastructurally the noninvolved urothelium of eight patients with transitional cell carcinoma who after transurethral resection and intravesicular interferon instillations for 2 years did not develop recurrence. We noted that the number and size of lysosomes increased, being most numerous within the cells of the surface layer. Characteristic large lysosomes with the morphology of multivesicular bodies were also evident. These multivesicular bodies were almost entirely filled with small vesicles containing a dense core. Our findings show that after 2 years of interferon administration a re-appearance of a highly developed lysosomal system of the noninvolved urothelium was evident. This restoration to the normal morphology with reappearance of the lysosomal system, which could be partly attributed to interferon therapy, may be of clinical significance for prevention of tumor recurrence.