SMALL-CELL LUNG-CANCER IS CHARACTERIZED BY A HIGH-INCIDENCE OF DELETIONS ON CHROMOSOMES 3P, 4Q, 5Q, 10Q, 13Q AND 17P

The genetic mechanisms that define the malignant behaviour of small-ce ll lung cancer (SCLC) are poorly understood. We performed comparative genomic hybridization (CGH) on 22 autoptic SCLCs to screen the tumour genome for genomic imbalances. DNA loss of chromosome 3p was a basic a lteration that occurred in all tumours. Additionally, deletions were o bserved on chromosome 10q in 94% of tumours and on chromosomes 4q, 5q, 13q and 17p in 86% of tumours. DNA loss was confirmed by loss of hete rozygosity (LOH) analysis for chromosomes 3p, 5q and 10q. Simultaneous mutations of these six most abundant genetic changes were found in 12 cases. One single tumour carried at least five deletions. DNA under-r epresentations were observed less frequently on chromosome 15q (55%) a nd chromosome 16q (45%). The prevalent imbalances were clearly indicat ed by the superposition of the 22 tumours to a CGH superkaryogram. In our view, the high incidence of chromosomal loss is an indication that SCLC is defined by a pattern of deletions and that the inactivation o f multiple growth-inhibitory pathways contributes in particular to the aggressive phenotype of that type of tumour.