By a molecular genetic approach using polymorphic DNA markers that detect allelic deletion of specific chromosomal regions, we analyzed for possible loss of chromosomal heterozygosity in five different histological types of lung cancers obtained from 47 patients. In small-cell carcinomas, the incidence of allelic deletions at three different chromosomal loci was extremely high; loss of heterozygosity was detected on chromosomes 3p in 7 of 7 patients (100%), 13q in 10 of 11 patients (91%), and 17p in 5 of 5 patients (100%). The deletions at these loci in small-cell carcinomas were observed even in the tumors without any clinical evidence of metastasis. Furthermore, loss of heterozygosity on chromosomes 3p and 13q occurred prior to NMYC amplification and chromosome 1lp deletion. Loss ofheterozygosity on chromosome 3p was also detected with high frequency in adenocarcinomas [5 of 6 patients (83%)]. Heterozygosity of chromosomes 13q and 17p was lost in 10 of31 patients (32%) and in 3 of 12 patients (25%), respectively, of lung cancers other than small-cell carcinomas. These results indicate that recessive genetic changes involving sequences on chromosomes 3p, 13q, and 17p may play important roles in the genesis of small-cell carcinoma, and those on chromosome 3p may play an important role in the genesis of adenocarcinoma.

A newly cloned gene named wild-type p53-activated fragment 1 (WAF1; also known as p21, Pic-1, Cip-1, or SDI1) is directly regulated by p53 and can itself suppress tumor cell growth in culture. Induction of expression of WAF1 may be an important means by which cells with DNA injury arrest their growth to repair DNA or undergo apoptosis. Based on the hypothesis that mutations of this gene may play a role in carcinogenesis, we have studied 351 DNAs from 14 kinds of malignancies, as well as 36 human transformed cell lines, for alterations of WAF1 gene by single-strand conformation polymorphism analysis of polymerase chain reaction amplification of the DNA coding region of the WAF1 gene. No abnormal band shifts of WAF1 were noted in any of the samples or cell lines, but three major variants in exons 2 and 3 of the gene were found that are consistent with the existence of two different DNA polymorphisms. Sequence analysis of the amplified products producing these three variants in each exon from normal DNAs confirmed the presence of the polymorphisms in the WAF1 gene. Of 290 selected tumor samples previously evaluated for p53 mutations by single-strand conformation polymorphism, 90% had no detectable p53 alterations. In summary, mutations within the coding portion of the WAF1 gene were undetectable in a large series of human tumors, many of which had a normal p53 gene. This suggests that WAF1 alterations are generally caused indirectly, through p53 mutations rather than through intragenic mutation of the WAF1 itself.

The human HSTI gene, previously designated the hst gene, and now assigned the name HSTFI for heparin-binding secretory transforming factor in human gene nomenclature, was originally identified as a transforming gene in DNAs from human stomach cancers by transfection assay with mouse NIH 3T3 cells. The amino acid sequence of the product deduced from DNA sequences of the HSTI cDNA and genomic clones had approximately 40% homology to human basic and acidic fibroblast growth factors and mouse Int-2-encoded protein. We have mapped the human HSTI gene to chromosome 11 at band q13.3 by Southern blot hybridization analysis of a panel of human and mouse somatic cell hybrids and in situ hybridization with an HSTI cDNA probe. The HSTI gene was found to be amplified in DNAs obtained from a stomach cancer and a vulvar carcinoma cell line, A431. In all of these samples of DNA, the INT2 gene, previously mapped to human chromosome 11q13, was also amplified to the same degree as the HSTI gene.

p53 mutations are found in a wide variety of cancers, including hematologic malignancies. These alterations apparently contribute to development of the malignant phenotype. We analyzed a large series of lymphoid (330 cases) and a smaller series of myeloid (29 cases) malignancies of childhood for p53 mutations by single-strand conformational polymorphism (SSCP) following polymerase chain reaction. Samples with abnormal SSCP were reamplified and analyzed by direct sequencing method. p53 mutations were detected within the known mutational hotspots (exons 5 to 8) in 8 of 330 lymphoid malignancies, and in none of 29 myeloid malignancies, showing that the frequency of p53 mutations in childhood lymphoid malignancies was very low (8 of 330 cases [2%]). Four of these patients had very aggressive, fatal acute lymphocytic leukemia (ALL). None of 13 infants and none of 48 patients with T-lineage leukemia had detectable p53 mutations in their ALL cells. Exceptionally, p53 mutations were comparatively frequent in a small sample of B-cell non-Hodgkin's lymphomas (2 of 8 cases). Mutations were detected in samples from two patients with ALL at relapse; these were not detected in samples at initial diagnosis from the same patients, suggesting that p53 mutations may be associated with progression to a more malignant phenotype. Seven of eight alterations of p53 were missense mutations, and seven of eight samples may be heterozygous for the mutant p53, indicating that p53 protein may act in a dominant negative fashion.

The amounts of mRNA for glutathione S transferase π (GST π) were significantly lower in 3 human small cell lung cancer (SCLC) cell lines than in 3 non small cell lung cancer (NSCLC) cell lines. The sensitivities of the 3 SCLC cell lines to cisplatin and carboplatin were much higher than those of the 3 NSCLC cell lines. These results indicate that low levels of GST π mRNA expression in SCLC cell lines inversely correlate to high sensitivity to cisplatin and carboplatin, and further suggest that GST π may play an important role in intracellular inactivation of these drugs.