Apoptosis was observed in palatine tonsil carcinomas (squamous cell carcinoma; 11 cases) by TUNEL staining. The TUNEL labeling index (TLI) of carcinoma cells had no relation to TNM, staging, pathohistological differentiated grades or the efficiency of radiotherapy. TLI (means: 5.2%) of postradiotherapy cases was higher than that of preradiotherapy cases (1.9%). TUNEL positive cells were found in the tissues surrounding cancers. In the surrounding tissues, the TLI (means: 5.1%) of postradiotherapy cases was higher than that of preradiotherapy cases (2.0%). These findings indicated that apoptosis induced by radiotherapy could suppress cancer development. Reversely, the invasion and metastasis of surviving cancers may be promoted by apoptosis induced in the surrounding tissues.
