Distinct nonrandom patterns of chromosomal aberrations in the progression of squamous cell carcinomas of the head and neck

Abstract

Fifty-one randomly selected primary squamous cell carcinomas of the head and neck, derived from the larynx (n = 18) and pharynx (oropharynx, n = 18, and hypopharynx, n = 15) were analyzed with centromeric probes for chromosomes 1, 7, 9, 11, 17, and 18 to study numerical aberrations, chromosome imbalances, and aneuploidy by fluorescence in situ hybridization. The tumors were grouped into nonmetastasizing (N0) tumors (from patients clinically free of lymph node metastases for at least 18 months after surgery, n = 25) and metastasizing (N1-3) tumors (n = 26). We found a significant association between the tumor ploidy and the nodal status; in the N0 group, diploidy prevailed, and the most common aberration was loss to monosomy for chromosome 9 (44%), whereas in the N1-3 group, aneuploidy predominated (P = 0.002). Specifically, these genomic changes associated with progression to metastasis were: (a) tetrasomic or polysomic chromosomes were detected in 17 of 26 N1-3 tumors but in none of the 25 N0 tumors (P < 0.0001); (b) heterogeneous chromosomal copy numbers (i.e., extensive chromosomal imbalances) were also much more frequent in the N1-3 tumors (69.2% versus 24.0% in the N0 group; P = 0.018); and (c) loss of chromosome 9 (73%) and gains of chromosomes 7 (35%) and 17 (31%) persisted, but in addition, loss of chromosome 18 occurred in 31%. Overexpression of the p53 protein correlated with an increased incidence of chromosomal imbalances and aneuploidy (P < 0.001) and, hence, constituted an additional risk factor. The lower metastatic potential of larynx tumors as compared with tumors from the pharynx was reflected by a lower incidence of these genomic changes. These specific patterns of chromosomal aberrations can characterize and distinguish different stages of tumor progression of squamous cell carcinomas of the head and neck and should be valuable diagnostic and prognostic markers.