Chromosome abnormalities in human non-small cell lung cancer.
Clonal cytogenetic abnormalities found in 30 non-small cell lung carcinomas (NSCLC), including 28 newly diagnosed primary tumor specimens, are summarized. Multiple chromosome alterations were identified in every case, and 19 of 30 tumors had near-triploid or near-tetraploid karyotypes. Polysomy 7 and partial gains of 7p, including 7p11-p13 (site of the EGFR gene), were particularly frequent, occurring alone or in combination in 26 tumors. Recurrent losses involving 1p, 3p, 6q, 9p, 11p, 15p, and 17p (where the TP53 gene is located) were each seen in 16-25 cases. Five tumors exhibited double minutes, which were associated with amplified MYC1 (1 case) and EGFR (1 case), as determined by Southern analysis. The cytogenetic data were compiled from either short term cultures of tumor tissue harvested within 1-9 days (18 cases) or later harvests performed on long term cultures or cell lines (6 cases); in the other 6 cases results were obtained from both short term and long term cultures. Two studies were performed to validate the use of long term culture for cytogenetic analysis of solid lung tumors. First, in order to determine whether cytogenetic results from cultures are representative of the original tumor, the modal chromosome number of 13 specimens placed into culture was compared to the DNA index of the original tumor tissue, as measured by flow cytometry. The DNA indices of the solid tumor biopsies agreed with the degree of aneuploidy observed by cytogenetic analysis in every case. Second, in 6 cases we performed direct comparisons of karyotypes obtained from cells cultured by both methods. Identical chromosome abnormalities were detected in short term cultures and later harvests of the same specimen. Overall, our findings indicate that tumorigenesis in NSCLC is characterized by the accumulation of multiple chromosome alterations. Furthermore, these data demonstrate that recurrent cytogenetic changes can be identified in NSCLC and that detailed karyotypes from long term cultures are relevant to the original tumor. Chromosome abnormalities detected by these techniques may have clinical and biological significance. However, the complex pattern of karyotypic changes seen in newly diagnosed NSCLC emphasizes the need for future investigations of premalignant bronchial lesions in order to identify primary genetic changes important for early detection and intervention in this aggressive neoplasm.