FREQUENT LOSS OF HETEROZYGOSITY ON CHROMOSOME ARM 18Q IN SQUAMOUS-CELL CARCINOMAS - IDENTIFICATION OF 2 REGIONS OF LOSS - 18Q11.1-Q12.3 AND18Q21.1-Q23

Objectives: To determine the frequency and regions of loss on chromoso me arm 18q in uncultured head and neck squamous cell carcinomas. Desig n: Polymerase chain reaction amplification of DNA extracted from 18 tu mor specimens (1 patient had 2 tumors) and blood samples from 17 patie nts with head and neck squamous cell carcinoma was performed using pri mers flanking 16 microsatellite repeat polymorphisms spanning most of chromosome 18q. DNA was extracted only from specimens with greater tha n 70% tumor nuclei. Setting: Research university. Patients: Seventeen individuals with newly diagnosed head and neck cancer. Main Outcome Me asure: Loss of heterozygosity (LOH). Results: There was LOH at more th an 1 locus in 52% (9/17) of the tumors; 3 tumors had LOH at all inform ative markers. Four had loss at only 1 locus, raising the total with l oss to 12 (75%) of 16. Loss of 18q11.1-q12.3 in 4 tumors without dista l loss defines a proximal region of loss. Loss of heterozygosity affec ting 18q21.1 in 1 tumor, without proximal loss and LOH for 18q21.1, 18 q22, or 18q23 in 9 (52%) of 17 tumors defines a distal region of loss. Conclusions: Loss of heterozygosity on chromosome arm 18q is not an a rtifact of in vitro culture. The finding of 18q LOH in 50% to 70% tumo rs makes 18q an impor tant region for study. Regions 18q11.1-q12.3 and 18q21.1-q23 are common regions of loss, indicating that there may be more than one 18q tumor suppressor gene involved in the genesis and pr ogression of head and neck squamous cell carcinomas.