CHROMOSOME-ABNORMALITIES IN ORAL SQUAMOUS-CELL CARCINOMAS

Strong evidence in favour of the somatic mutation theory of cancer, which states that genomic rearrangements are early and essential events in tumour development, has during the past two decades been obtained from both cytogenetic and molecular genetic studies of neoplastic cells. More than 14000 neoplasms with acquired clonal chromosome aberrations have been reported; the majority have, however, been haematological malignancies, whereas still little is known about the karyology of the quantitatively more important carcinomas. For oral squamous cell carcinomas (SCC), which constitute a substantial subset of human malignancies, only 63 short-term cultured tumours with karyotypic aberrations have been described. Simple numerical changes, mostly -Y, +Y, or +7, have been detected as the sole anomalies in 19 tumours, but these aberrations are probably not causally related to the neoplastic process. The remaining 44 SCC have had structural changes of varying complexity, often together with numerical aberrations. An assessment of the karyotypic imbalances resulting from these aberrations reveals that chromosomes 9, 13, 18 and Y are recurrently lost, and that deletions frequently involve chromosome arms 3p, 7q, 8p, 11q, 17p and the short arms of all acrocentric chromosomes. The chromosomal breakpoints in structural rearrangements frequently involve the centromeric regions of chromosomes 1, 3, 8, 14 and 15 as well as bands 1p22, 11q13 and 19p13. At least one of these bands has been rearranged in 70% of SCC with structural aberrations and they probably contain loci of importance in oral squamous cell carcinogenesis. A comparison of data obtained from oral and other types of SCC-laryngeal, oesophageal, lung, cervical, and anal canal-indicates that some of the events in the multistep process of SCC development involve the same genetic pathways irrespective of site of origin.