High frequency of chromosome 3p deletion in histologically normal nasopharyngeal epithelia from southern Chinese

We have examined the presence of loss of heterozygosity (LOH) on chromosome 3p in histologically normal nasopharyngeal epithelia (NP), dysplastic lesi ons, and carcinoma of the nasopharynx from different ethnic and geographic regions. Microdissected normal NP from noncancerous individuals and nasopha ryngeal carcinoma (NPC) samples from both the high-risk group (southern Chi nese in Hong Kong) and two low-risk groups for NPC (central/northern Chines e in Anhui/Beijing and Caucasians in Toronto) were included. All NPC sample s showed high incidence of 3p deletion (81-100%), High frequencies of LOH o n 3p were also detected in normal NP (73.9%) and dysplastic lesions (75%) f rom the southern Chinese. Significant tower frequency of LOH on 3p was note d in normal NP from the low-risk groups (20%) than those from high-risk gro ups (P = 0.0003), The presence of such genetic alterations in the histologi cally normal NP and dysplastic lesions suggests that it is an early event i n tumor development. The higher frequency of 3p LOH found in normal NP from southern Chinese compared with those from low-risk groups may be related t o the distinct cancer incidence among these populations.