Studies of hereditary cancer syndromes have contributed greatly to our understanding of molecular events involved in tumorigenesis. Here we investigate the molecular background of the Peutz-Jeghers syndrome (PJS), a rare hereditary disease in which there is predisposition to benign and malignant tumours of many organ systems. A locus for this condition was recently assigned to chromosome 19p. We have identified truncating germline mutations in a gene residing on chromosome 19p in multiple individuals affected by PJS. This previously identified but unmapped gene, LKB1, has strong homology to a cytoplasmic Xenopus serine/threonine protein kinase XEEK1, and weaker similarity to many other protein kinases. Peutz-Jeghers syndrome is therefore the first cancer-susceptibility syndrome to be identified that is due to inactivating mutations in a protein kinase.

The recessively inherited developmental disorder, cartilage-hair hypoplasia (CHH) is highly pleiotropic with manifestations including short stature, defective cellular immunity, and predisposition to several cancers. The endoribonuclease RNase MRP consists of an RNA molecule bound to several proteins. It has at least two functions, namely, cleavage of RNA in mitochondrial DNA synthesis and nucleolar cleaving of pre-rRNA. We describe numerous mutations in the untranslated RMRP gene that cosegregate with the CHH phenotype. Insertion mutations immediately upstream of the coding sequence silence transcription while mutations in the transcribed region do not. The association of protein subunits with RNA appears unaltered. We conclude that mutations in RMRP cause CHH by disrupting a function of RNase MRP RNA that affects multiple organ systems.

By searching the Expressed Sequence Tag (EST) data base, we identified partial cDNA sequences potentially encoding a novel human CC chemokine. We determined the entire cDNA sequence which encodes a highly basic polypeptide of 134 amino acids total with a putative signal peptide of 23 amino acids. The predicted mature protein of 111 amino acids has the four canonical cysteine residues and shows 21-33% identity to other human CC chemokines, but has a unique carboxyl-terminal extension of about 30 amino acids which contains two extra cysteine residues. The mRNA was expressed strongly in tissues such as the lymph nodes, appendix, and spleen. The recombinant protein, which was produced by the baculovirus system and purified to homogeneity, was a highly efficient chemoattractant for certain human T cell lines and a highly potent one for freshly isolated peripheral blood lymphocytes and cultured normal T cells expanded by phytohemagglutinin and interleukin 2. Unlike most other CC chemokines, however, this novel chemokine was not chemotactic for monocytes or neutrophils, suggesting that it is specific for lymphocytes. From these results, we designated this novel CC chemokine as SLC from secondary lymphoidtissue chemokine. SLC fused with the secreted form of alkaline phosphatase (SLC-SEAP) was used to characterize the SLC receptor. Binding of SLC-SEAP to freshly isolated lymphocytes was blocked by SLC (IC 50 , 0.12 nM) but not by any other CC chemokine so far tested, suggesting that resting lymphocytes express a class of receptors highly specific for SLC. By using somatic cell hybrids, radiation hybrids, and selected yeast and bacterial artificial chromosome clones, we mapped the SLC gene (SCYA21) at chromosome 9p13 and between chromosomal markers, D9S1978(WI-8765) and AFM326vd1, where the gene for another novel CC chemokine termed ELC from EBI1-ligand chemokine (SCYA19) also exists. Collectively, SLC is a novel CC chemokine specific for lymphocytes and, together with ELC, constitutes a new group of chemokines localized at chromosome 9p13.

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Pleiotropic, recessively inherited cartilage-hair hypoplasia (CHH) is due to mutations in the untranslated RMRP gene on chromosome 9p13-p12 encoding the RNA component of RNase MRP endoribonuclease. We describe 36 different mutations in this gene in 91 Finnish and 44 non-Finnish CHH families. Based on their nature and localisation, these mutations can be classified into three categories: mutations affecting the promoter region, small changes of conserved nucleotides in the transcript, and insertions and duplications in the 5' end of the transcript. The only known functional region that seemed to avoid mutations was a nucleolar localisation signal region between nucleotides 23 -62. The most common mutation in CHH patients was a base substitution G for A at nucleotide 70. This mutation contributed 92% of the mutations in the Finnish CHH patients. Our results using linkage disequilibrium based maximum likelihood estimates with close markers, genealogical studies, and haplotype data suggested that the mutation was introduced to Finland some 3900 -4800 years ago, and before the expansion of the population. The same major mutation accounted for 48% of the mutations among CHH patients from other parts of Europe, North and South America, the Near East, and Australia. In the non-Finnish CHH families, the A70G mutation segregated with the same major haplotype, although shorter, as in most of the Finnish families. In 23 out of these 27 chromosomes, the common region extended over 60 kb, and, therefore, all the chromosomes most likely arose from a solitary event many thousands of years ago.

We investigated point mutational activation of the ras genes (K-ras codons 12, 13 and 61; N-ras codons 12, 13 and 61; H-ras codons 12 and 61) in primary, resected lung cancer by dot blotting and oligonucleotide hybridization. K-ras mutations were found in 14 (29%) of the 48 lung tumour specimens examined, but no N-ras or H-ras mutations were found. The highest frequency of K-ras mutation was observed in adenocarcinoma: 12 of the 21 samples studied (57%) had a mutation, which is one of the highest frequencies reported for lung adenocarcinoma. The commonest type of mutation in these lung tumour samples consisted of transversions: we observed 11, of which 8 (57% of all mutations) were G to T transversions. Most of the 48 patients studied had a history of heavy smoking, either with or without evidence of occupational exposure to asbestos. Statistical analysis revealed--in addition to the highly significant association between the adenocarcinoma type of lung cancer and K-ras mutation--a clear association of K-ras mutations with heavy life-time smoking (> or = 50 pack-years of cigarette smoking; odds ratio (OR) 4.9, 90% CI 1.2-19.5, multivariate analysis). In addition, occupational asbestos exposure showed an elevated, but non-significant, OR of 2.2 (90% CI 0.6-8.7) with the presence of K-ras mutation. We conclude that the occurrence of K-ras mutations in adenocarcinoma of the lung is frequent, and that such mutations are associated with heavy life-time exposure to tobacco smoke, possibly in combination with occupational exposure to asbestos fibres.

In one-third of families fulfilling the Amsterdam criteria for hereditary nonpolyposis colorectal cancer/Lynch syndrome, and a majority of those not fulfilling these criteria point mutations in DNA mismatch repair (MMR) genes are not found. The role of large genomic rearrangements and germline epimutations in MLH1, MSH2 and MSH6 was evaluated in 2 such cohorts. All 45 index patients were mutation-negative by genomic sequencing and testing for a prevalent population-specific founder mutation, and selectively lacked MMR protein expression in tumor tissue. Eleven patients (''research cohort'') represented 11 mutation-negative families among 81 verified or putative Lynch syndrome families from the nation-wide Hereditary Colorectal Cancer Registry of Finland. Thirty-four patients from 33 families (''clinic-based cohort'') represented suspected Lynch syndrome patients tested for MMR gene mutations in a diagnostic laboratory during [2004][2005][2006][2007]. Multiplex ligation-dependent probe amplification (MLPA) and methylation-specific (MS)-MLPA were used to detect rearrangements and epimutations, respectively. Large genomic deletions occurred in 12/45 patients (27%), being present in 3/25 (12%), 9/16 (56%) and 0/4 (0%) among index patients lacking MLH1, MSH2 or MSH6 expression, respectively. Germline epimutations of MLH1, one of which coexisted with a genomic deletion, occurred in 2 patients (4%) and were accompanied by monoallelic expression in mRNA. Large genomic deletions (mainly MSH2) and germline epimutations (MLH1) together explain a significant fraction of point mutation-negative families suspected of Lynch syndrome and are associated with characteristic clinical and family features. Our findings have important implications in the diagnosis and management of such families.

Cartilage-hair hypoplasia (CHH), or McKusick type metaphyseal chondrodysplasia, was originally described in the Old Order Amish in the United States and subsequently found to be unusually frequent among Finns. The major mutation causing CHH in Finns is a 70A --> G nucleotide substitution in the RMRP gene, which encodes the untranslated RNA that is a component of mitochondrial RNA-processing endoribonuclease. Here we report that the same mutation is the most frequent one, perhaps the only one, in the Amish population in which CHH was first characterized. The fact that the mutation segregates with the same major haplotype in these two populations and others suggests that it is very ancient. Unlike some other ordinarily rare recessive disorders that are limited in their high frequency to a single Amish deme (subisolate), e.g., Ellis-van Creveld syndrome, CHH occurs in high frequency in at least three distinct Amish demes, indicating, along with genealogic data, that there were multiple heterozygotes among the founders, as proposed by McKusick et al. [1965: Bull Johns Hopkins Hosp 116:231-272].