Frequent loss of heterozygosity on chromosome arm 18q in squamous cell carcinemas: Identification of 2 regions of loss-18q11.1-q12.3 and 18q21.1- q23

Objectives: To determine the frequency and regions of loss on chromosome arm 18q in uncultured head and neck squamous cell carcinomas. Design: Polymerase chain reaction amplification of DNA extracted from 18 tumor specimens (1 patient had 2 tumors) and blood samples from 17 patients with head and neck squamous cell carcinoma was performed using primers flanking 16 microsatellite repeat polymorphisms spanning most of chromosome 18q. DNA was extracted only from specimens with greater than 70% tumor nuclei. Setting: Research university. Patients: Seventeen individuals with newly diagnosed head and neck cancer. Main Outcome Measure: Loss of heterozygosity (LOH). Results: There was LOH at more than I locus in 52% (9/17) of the tumors; 3 tumors had LOH at all informative markers. Four had loss at only 1 locus, raising the total with loss to 12 (75%) of 16. Loss of 18ql 1.1-q12.3 in 4 tumors without distal loss defines a proximal region of loss. Loss of heterozygosity affecting 18q21.1 in 1 tumor, without proximal loss and LOH for 18q21.1, 18q22, 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 artifact of in vitro culture. The finding of 18q LOH in 50% to 70% tumors makes 18q an important region for study. Regions 18ql 1.1-ql 2.3 and 18q21.1q23 are common regions of loss, indicating that there may be more than one 18q tumor suppressor gene involved in the genesis and progression of head and neck squamous cell carcinomas.