Laura De Gregorio

The FHIT gene at 3p14.2 is abnormal in lung cancer

To determine the role of the FHIT gene, which encompasses the fragile site at 3p14.2, we analyzed 59 tumors of the small cell and non-small cell type by reverse transcription of FHIT mRNA, followed by PCR amplification and sequencing of products. Allelic losses affecting the gene were evaluated by microsatellite polymorphism analysis and genomic alterations by hybridization using cDNA and genomic probes. Small cell lung tumors (80%) and non-small cell lung cancers (40%) showed abnormalities in RNA transcripts of FHIT, and 76% of the tumors exhibited loss of FHIT alleles. Abnormal lung tumor transcripts lack two or more exons of the FHIT gene. Small cell lung cancer tumors and cell lines were analyzed by Southern blotting and showed rearranged BamHI fragments. These data suggest a critical role of the FHIT gene in lung carcinogenesis.

Genetics of liver tumor susceptibility in mice

A good experimental model of genetic predisposition to hepatocellular tumors is the murine strain C3H. These tumors share morphologic similarities with human hepatocellular tumors. After a treatment with a single small dose of chemical carcinogen, the C3H mice show a high susceptibility to the growth of hepatocellular neoplastic lesions, that reach a volume > 100-fold as compared to the corresponding lesions of genetically resistant strains. Genetic linkage analysis experiments were conducted in 2 different crosses, with the C3H as one of the parental strains, and the other parental strains being represented by mice genetically resistant to hepatocarcinogenesis (A/J, M. spretus). Six different regions, on chromosomes 2, 5, 7, 8, 12, and 19 showed a significant linkage with hepatocellular tumor development. These results provide the genetic basis for the strain variations seen in susceptibility to hepatocarcinogenesis, indicating polygenic inheritance of this trait.

Prognostic value of loss of heterozygosity and KRAS2 mutations in lung adenocarcinoma

The prognostic values of loss of heterozygosity (LOH) at loci frequently involved in non‐small cell lung cancer and of KRAS2 gene mutations were studied in lung adenocarcinoma patients. LOHs were relatively common, ranging from 24% at chromosome 10p to 55% at chromosome 17p13. KRAS2 mutations at codon 12 were present in 26% of cases, were more common in male than in female patients and were associated with a smoking habit. No association between LOH at any site and clinical stage or survival rate was found. On the other hand, we observed a trend between the presence of any type of KRAS2 mutations and poor survival. Analysis of specific KRAS2 mutations showed a strong effect of Asp (GAT) and Val (GTT) mutations, resulting in a very poor survival compared with wild type group, whereas the most common mutation (Cys, TGT) was not associated with prognosis. Our results indicate the importance of specific activating mutations of the KRAS2 gene as genetic markers of clinical outcome for patients with lung adenocarcinoma. Int. J. Cancer (Pred. Oncol.) 79:269–272, 1998.© 1998 Wiley‐Liss, Inc.

Predisposition to lung tumorigenesis.

Mouse inbred strains with inherited predisposition and resistance to lung cancer provide an essential tool for the dissection of the genetics of this complex disease. We have previously mapped a major locus (Pulmonary adenoma susceptibility 1, Pas1) affecting inherited predisposition to lung cancer in mice on chromosome 6, near Kras2. Appropriate crosses that include susceptible mice (Pas1(s)) provide a model system for identifying loci that can modify the lung cancer predisposition phenotype caused by Pas1. Using this approach we have mapped the Pulmonary adenoma resistance 1 (Par1) locus that behaves like a modifier locus of Pas1. More recently, we mapped additional lung tumor resistance loci (Par2, and Par4), and a locus specifically involved with lung tumor progression (Papg1). The mapping of Pas1 in mice stimulated us to test the possible association of genetic markers located in the homologous human region (12p12) with risk and prognosis of lung adenocarcinomas in man. In the Italian population, we carried out an association study by genotyping lung adenocarcinoma patients and healthy controls for genetic markers located in the putative region of interest. Homozygosity of the A2 allele at a Kras2/RsaI polymorphism, and allele 2 at a VNTR polymorphism in the PTHLH gene showed borderline statistically significant associations with lung cancer risk. Furthermore, the same alleles were significantly associated with tumor prognosis. Studies on association were then performed in the Japanese and in European populations. In the Japanese population, the KRAS2/RsaI marker was significantly associated with prognosis of lung adenocarcinoma, whereas the European study did not confirm this association. Our results may provide evidence for the existence of the human PAS1 locus, suggesting that the mouse model of inherited predisposition to lung tumorigenesis is predictive of a human genetic mechanism of susceptibility to lung cancer.

ZFP60, A MOUSE ZINC FINGER GENE EXPRESSED TRANSIENTLY DURING IN VITRO MUSCLE DIFFERENTIATION

The complete cDNA coding sequence of the zinc finger gene Zfp60 is reported. The predicted amino acid sequence of the Zfp60 protein has been found to contain 19 zinc finger motives clustered at the C‐terminus. At its N‐terminus, Zfp60 shares with other members of the zinc finger gene family two additional conserved amino acid modules named Kruppel Associated Boxes (KRAB). The expression patterns of Zfp60, MyoD and MHC mRNAs have been followed during in vitro myogenic differentiation of C2 cells. We show that the bacterial produced Zfp60 protein binds DNA only in presence of zinc ions. Zfp60 locus has been mapped in chromosome 7, where other Zfp loci are localised.

Genetic mapping of the mouse Rab7 gene and pseudogene and of the human RAB7 homolog.

Abstract. Rab proteins are small GTP-ases localized to distinct membrane compartments in eukaryotic cells and regulating specific steps of intracellular vesicular membrane traffic. The Rab7 protein is localized to the late endosomal compartment and controls late steps of endocytosis. We have isolated, by library screening, the 5′ region, including the promoter, of the mouse Rab7 gene and a Rab7 pseudogene. We have mapped, by genetic linkage analysis, the mouse Rab7 gene on Chromosome (Chr) 6 and the Rab7-ps1 pseudogene on Chr 9, where the Rab7 gene has been previously reported to map. By radiation hybrid mapping, we have located the human RAB7 gene on Chr 3, in a region homologous to the mouse Chr 6, where the Rab7 gene maps.

Analysis of the retinoic acid receptor α gene as a candidate for the pulmonary adenoma resistance 1 gene

The retinoic acid receptor α (Rara) gene, which maps in the same region as the pulmonary adenoma resistance (Par1) locus on mouse chromosome 11 (Manenti G et al., Nature Genet 12:455–457, 1996), was tested as a candidate gene for Par1. We report here the analysis of loss of heterozygosity, nucleotide sequence comparison, gene expression, and biochemical activity of the Rara gene from the Mus spretus (Par1/+) and A/J (Par1/–) mouse strains. The two Rara alleles were distinguished by two amino‐acid variations but had similar biochemical activity and expression levels, leading to the exclusion of Rara as a candidate Par1 gene. Mol. Carcinog. 21:13–16, 1998.