TELOMERASE ACTIVATION IN NASOPHARYNGEAL CARCINOMAS

Nasopharyngeal carcinomas (NPC) are common in Hong Kong and southern C hina but rare in Western countries. Telomerase activation is common in human cancers but has not been reported previously in NPC. Telomerase activation in NPC was determined using the sensitive TRAP (telomerase rapid amplification protocol) assay in 45 nasopharyngeal biopsies (36 NPC, nine normal nasopharyngeal mucosae) in four xenografted NPC tumo urs established in nude mice and in five in vitro NPC cell lines. Telo merase activation is common in NPC and can be detected at high frequen cies (85% in primary tumours and 100% in recurrent tumours). The frequ ency of telomerase activation was lowest in NPC biopsies without lymph node involvement (60%) compared with those with positive lymph node i nvolvement (100%), and the difference is statistically significant (P < 0.05; Fisher exact test). All the xenografted NPC tumours and in vit ro NPC cell lines were strongly positive for telomerase activity. Our results suggest that telomerase activation is common in NPC and it may be useful as a diagnostic marker in the detection of tumour cells in nasopharyngeal biopsies. The high frequency of telomerase activation i n stage I NPC (80% positive) suggests that it is an early event in tum our progression.