Germline MLH1 and MSH2 mutations in Italian pancreatic cancer patients with suspected Lynch syndrome

Lynch syndrome is an inherited cancer syndrome caused by germline mutations in mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2. LS predisposes to high risk of early-onset colorectal, endometrial and other tumors. Patients with Lynch syndrome have also been shown to have an elevated risk for pancreatic cancer (PC). In this study, we aimed to estimate the frequency of suspected Lynch syndrome among a series of 135 PC patients. Further, we wanted to determine the frequency of MMR gene mutations in the suspected Lynch syndrome cases. We also aimed to verify the pathogenicity of any novel non-truncating variants we might detect with a functional assay. Based on personal and/or familial cancer history, 19 patients were classified as suspected Lynch syndrome cases. DNA material for mutation analysis was available for eleven of them. Four patients were found to carry a total of five MLH1 or MSH2 variants. Of these, MSH2-Q402X, MSH2-G322D, and MLH1-K618A had been previously reported, while the MSH2-E205Q and MSH2-V367I variants were novel. MSH2-Q402X is a known stop mutation and reported here for the first time here in association with PC. MLH1-K618A was found in the unaffected branch of a kindred, suggesting that it may be a polymorphism or a low penetrance variant. MSH2-G322D likely does not cause a MMR defect, although this variant has also been associated with breast cancer as indeed seen in our patient. The novel variants MSH2-E205Q and MSH2-V367I were found in the same patient. Both novel variants were however functional in the applied MMR assay. Our findings suggest that only a small subset of pancreatic cancer patients carry pathogenic MMR mutations.

A genetic model for determining MSH2 and MLH1 carrier probabilities based on family history and tumor microsatellite instability

Mutation-predicting models can be useful when deciding on the genetic testing of individuals at risk and in determining the cost effectiveness of screening strategies at the population level. The aim of this study was to evaluate the performance of a newly developed genetic model that incorporates tumor microsatellite instability (MSI) information, called the AIFEG model, and in predicting the presence of mutations in MSH2 and MLH1 in probands with suspected hereditary non-polyposis colorectal cancer. The AIFEG model is based on published estimates of mutation frequencies and cancer penetrances in carriers and non-carriers and employs the program MLINK of the FASTLINK package to calculate the proband's carrier probability. Model performance is evaluated in a series of 219 families screened for mutations in both MSH2 and MLH1, in which 68 disease-causing mutations were identified. Predictions are first obtained using family history only and then converted into posterior probabilities using information on MSI. This improves predictions substantially. Using a probability threshold of 10% for mutation analysis, the AIFEG model applied to our series has 100% sensitivity and 71% specificity.

Prevalence of the E1317Q variant of the APC gene in Italian patients with colorectal adenomas

Loss of APC is an initial, rate-limiting event in inherited and sporadic colorectal tumorigenesis. Rare germline APC mutations have been identified in patients with multiple colorectal adenomas. Recently, the E1317Q APC variant has been associated with a predisposition to the development of multiple colorectal adenomas. In this study, the prevalence of the E1317Q variant was examined in 182 patients with single or multiple colorectal adenomas, and in 235 controls. In all, E1317Q was identified in two of 182 patients with adenomatous polyps (1.1%) and in two of 235 controls (0.8%) (p = 0.59). The risk of harboring adenoma(s) among subjects bearing the E1317Q variant was 1.29 (95% CI 0.09-18.0). No difference in the prevalence of E1317Q between cases with single (2.0%) or multiple colorectal adenomas (0.7%) and controls (0.8%) was found. None of the subjects with a family history of colorectal cancer carried the E1317Q variant. In conclusion, our results confirm that only a very small fraction of colorectal adenomas may be associated with the presence of E1317Q.

Nine novel APC mutations in Italian FAP patients

Familial adenomatous polyposis (FAP) is a common hereditary syndrome characterized by early development of colorectal cancer consequent to extensive adenomatous polyps of the colon. In addition to the colonic manifestations the syndrome presents several extracolonic features including polyps of the upper gastrointestinal tract, congenital hypertrophy of the retinal pigment, jaw cysts, osteomata and desmoid tumors. In this study the entire APC coding region has been analysed for mutation in a panel of one Turcot and 33 unrelated Italian FAP patients using SSCP analysis, PTT and DNA sequencing. We detected APC mutations in 23 of them and identified nine which, to our knowledge were not previously reported. All of these novel mutations are in exon 15, including two nonsense mutations, 6 deletions or insertions leading to premature termination of the protein and one missense mutation (7697G>A). This last mutation occurs in the EB1-binding domain of the APC protein and segregates in four relatives of the patient with three of them presenting 2-3 adenomatous polyps.

Clinical features and genotype-phenotype correlations in 41 Italian families with adenomatosis coli

BACKGROUND

Familial Adenomatous Polyposis in an autosomal dominant disease in which the large bowel is carpeted by polyps of various dimensions appearing during the second or third decade of life. Several extracolonic manifestations complete the clinical spectrum of Familial Adenomatous Polyposis. If untreated, the disease leads invariably to colorectal cancer. The gene responsible for the disease, adenomatous Polyposis Coli, has been localized at chromosome 5q21.

AIMS

To describe the clinical features of 156 Familial Adenomatous Polyposis patients (from 41 families) and to analyze possible correlations between genotype and phenotype.

PATIENTS AND METHODS

Familial Adenomatous Polyposis was defined as the presence of 100 or more polyps in the large bowel. In 17 families (41%), the proband was the only affected individual (single cases). Adenomatous Polyposis Coli gene mutations were studied on DNA extracted from peripheral white blood cells and evaluated by polymerase chain reaction single strand conformation polymorphism, followed by direct sequencing of samples showing abnormal banding at single strand conformation polymorphism.

RESULTS

The large majority of Familial Adenomatous Polyposis patients underwent surgery; colectomy with ileorectal anastomosis was the most frequent approach, however, cancer of the rectal stump developed in 11.6% of patients submitted to colectomy and ileorectal anastomosis. Adenomas were rare in the stomach (8.8%), but their frequency increased in the duodenum (33.8%) and jejunum (55.0%, chi 2 for trend 23.7, p < 0.001). Desmoid tumours were diagnosed in 17 patients (10.9% of the total) and in 6 families. Mutations of the Adenomatous Polyposis Coli gene were studied in 20 out of 25 families (80%) and on a total of 75 individuals. The most frequent alterations were 1 to 5 bp deletions leading to stop codons and truncated proteins. Desmoid tumours, presence of duodenal or jejunal adenomas were associated with an ample range of mutations, from codon 215 to codon 1464. In contrast, particularly severe polyposis (mean age at appearance of polyps 11-16 years, and of cancer development 27-32 years) was associated with a "hotspot" mutation site at codons 1303-1309.

CONCLUSIONS

In patients with Familial Adenomatous Polyposis, subtotal colectomy with ileorectal anastomosis is still the treatment of choice. Adenomatous lesions seem to show a "gradient" distribution from the stomach to the large bowel. Desmoid tumours are relatively common, though their incidence is limited to some of the families. Constitutional mutations can be detected in 80% of the investigated families. Genotype-phenotype correlations showed a hot-spot at codons 1303-1309, frequently associated with severe polyposis.

STK11 mutations in Peutz-Jeghers syndrome and sporadic colon cancer

A potential tumor suppressor gene, STK11 , encoding a serine threonine kinase, has recently been identified on chromosome 19p13. Germ-line mutations of this gene have been found in patients with Peutz-Jeghers syndrome (PJS). To further investigate the relevance of STK11 mutations in PJS, we analyzed its coding sequence in nine patients and identified two deletions and three missense mutations. Because intestinal carcinomas have been observed to develop in association with PJS, we analyzed tumors from 71 patients for allelic deletions (loss of heterozygosity) and STK11 gene mutations, to elucidate the etiological role of STK11 gene in sporadic colorectal cancer. Loss of heterozygosity, evaluated using the microsatellite D19S886, was observed in 10 of 52 informative cases. No somatic mutations were detected except for a missense alteration in one tumor. Our data indicate the heterogeneity of PJS and the infrequent involvement of the STK11 gene in colorectal cancer.

The familial adenomatous polyposis region exhibits many different haplotypes

In the present study, we used five different polymorphic markers to construct the haplotype at the adenomatous polyposis coli (APC) locus in families with familial adenomatous polyposis (FAP) and in the normal Italian population. Non-ambiguous haplotypes were reconstructed from 246 normal chromosomes and 65 FAP chromosomes. In the control population, the four polymorphisms intragenic to APC gave rise to 16 haplotypes, the most common of which (II and XV) accounted for over 50% of all chromosomes. In FAP patients, 13 haplotypes were found but their distribution was not statistically different from normal subjects. Eighty complete chromosomal haplotypes (many fewer than the theoretical maximum of 208) for the five polymorphic sites assayed were observed in the control population, 35 being found in the FAP patients. We compared the distribution of these haplotypes within the two groups; no statistically significant differences between normal and FAP chromosomes were found. The elevated heterogeneity of FAP chromosomes was clearly confirmed by the observation that 19 patients who carried one or other of the two most common APC mutations (nt 3183 and nt 3927) showed 18 different haplotypes. On the basis of these results, we were not able to identify a founder FAP chromosome. Various mechanisms are presented to explain this observation.

Clinical findings in a family with familial adenomatous polyposis and a missense mutation of the adenomatous polyposis coli gene

BACKGROUND

More than 100 different mutations in the adenomatous polyposis coli (APC) gene have been identified; virtually all lead to the production of a truncated protein. Clinical details of patients with missense mutations undoubtedly cosegregating with the disease have not been reported and may be relevant in understanding the APC protein function.

METHODS

In one family with familial adenomatous polyposis (FAP) the APC gene was analyzed by SSCP and sequencing of the aberrant SSCP band.

RESULTS

A missense mutation in exon 15 at nucleotide 4921 segregating with the disease was observed. This predicts a tryptophan instead of an arginine at amino acid 1641 of the APC protein. No such mutation was present in 100 control subjects.

CONCLUSIONS

In this family the colonic manifestations are as expected for classical FAP. However, the occurrence of congenital hypertrophy of the retinal pigment epithelium is unusual, owing to the inconsistency of this manifestation between family members and because congenital hypertrophy of the retinal pigment epithelium is generally absent when mutations are after codon 1387.

Genetic Counseling in Hereditary Non-Polyposis Colorectal Cancer

Genetic counseling is a medical process aimed at providing information about disease risks for hereditary conditions. For adult-onset diseases, such as cancer, the main purpose consists in formulating probability estimates of disease appearance, along with details on preventive or follow-up measures. The process of genetic counseling has been substantially modified by the availability of molecular tests to identify mutant gene carriers. So far, 16 autosomal dominant genes associated with cancer susceptibility have been cloned. Four of these, which encode for components of the DNA mismatch repair machinery, have been implicated in hereditary non-polyposis colorectal cancer, one of the most common hereditary cancer syndromes. Genetic counseling and testing in hereditary non-polyposis colorectal cancer is associated with several problems that are common to other hereditary conditions (psychologic consequences, confidentiality, genetic “discrimination”, testing of minors, prenatal diagnosis) and peculiar to the specific condition (incomplete penetrance, genotypic and phenotypic heterogeneity, limits of currently available tests). For such reasons, genetic testing should be performed in qualified research laboratories and restricted to highly selected families. In this way, pilot studies, involving both clinicians and researchers, can be undertaken with the aim of providing comprehensive results, potentially applicable to other cancer-predisposing conditions.

Recombinant human erythropoietin for long-term treatment of anemia in paroxysmal nocturnal hemoglobinuria

The long-term effects of recombinant human erythropoietin (rhEPO) administration in two consecutive cases of paroxysmal nocturnal hemoglobinuria (PNH) with severe anemia are reported. In both patients, a 68-year-old woman and a 66-year-old man, a diagnosis of PNH was made on the basis of severe macrocytic anemia associated with hemoglobinuria, hemosiderinuria and positivity for the sucrose and Ham tests. Subcutaneous treatment with rhEPO, 150 U/Kg body weight daily, was followed in both cases by a progressive increase in hemoglobin concentrations, which thereafter were maintained above 10 g/dL with lower doses of rhEPO and without any relevant side effects for 32 and 29 months of continuous treatment, respectively. A clinical response was observed in spite of elevated baseline serum erythropoietin concentrations, appropriate to the degree of anemia in both patients. These results suggest that rhEPO may be appropriately and safely used in the long-term correction of anemia associated with PNH, and that the response to the pharmacologic doses of rHEPO administered was not dependent on the level of endogenous erythropoietin.

Clinical and biologic features of adenomatosis coli in Northern Italy

BACKGROUND

Familial adenomatous polyposis (FAP) is a hereditary disease characterized by more than 100 adenomas scattered in the large bowel and by various extracolonic manifestations. We proposed a) to establish the frequency of the disorder in Northern Italy, b) to describe the most relevant clinical findings, and c) in a subgroup of 21 patients (from 8 families), to evaluate the spectrum of mutations of the APC gene.

METHODS AND RESULTS

Patients with FAP diagnosed between 1961 and 1991 were referred to our Study Group from surgery and gastroenterology units of the region Emilia-Romagna. The incidence of FAP was in the order of 1 in 16,500, with about a third of patients being 'single' cases. Colorectal malignancies were present in 75.6% of symptomatic patients but absent in most (93.75%) of the asymptomatic family members ('call-up' individuals). Gastric, duodenal, and jejunal adenomas were found in 8.2%, 30.6% and 53.3% of the investigated patients, respectively. Congenital hypertrophy of the retinal pigment epithelium and occult jaw lesions were seen in 64.7% and 39.5% of FAP patients but only in 0.5% and 2.5% of a matched, by age and sex, control population. These two clinical markers had a specificity of 99% and 97%, although their sensitivity was 64% and 39%. Finally, mutations of the APC gene were detected in 6 families (16 affected individuals) of the 8 families (21 affected individuals) tested; no correlation could be found between genotype and phenotype.

CONCLUSIONS

This study confirms that early diagnosis is essential for an appropriate management of FAP patients, although this aim remains elusive in single cases. High-risk individuals are ideal candidates for APC gene mutation analysis, which should be offered to all first-degree relatives of affected patients.

Expression and genomic configuration of GM-CSF, IL-3, M-CSF receptor (C-FMS), early growth response gene-1 (EGR-1) and M-CSF genes in primary myelodysplastic syndromes

Peripheral blood mononuclear cells from seventeen patients with primary myelodysplastic syndromes (MDS) in advanced stage were enriched for blasts and tested for (1) karyotype, (2) genomic configuration and (3) expression of IL-3, GM-CSF, FMS and EGR-1 genes which are all located on the long arm of chromosome 5. The expression of the M-CSF gene, that has been recently reassigned to the short arm of chromosome 1 (lp), was also investigated. Aims of the study were to (1) assess the potential role of the expression of these genes in the maintenance and expansion of the neoplastic clones and (2) search for constitutional losses or rearrangements of one allele followed by a deletion of the second allele of the same genes in the leukemic cells. The latter issue was investigated by comparing, in 8 cases, constitutive DNA from skin fibroblasts with leukemic DNA. Eleven of the 17 patients had abnormal karyotypes. The M-CSF gene was expressed in 6 cases and the FMS and the EGR-1 genes were expressed in 2 of the latter cases. An autocrine mechanism of growth could be hypothesized only for the 2 patients whose cells expressed both the M-CSF and FMS genes. No germline changes or rearrangements were observed in any of the genes studied. Thus, deregulation of genes encoding for certain hemopoietic growth factors or receptors does not seem to represent a major mechanism of MDS progression.

Exclusion of the APC gene as the cause of a variant form of familial adenomatous polyposis (FAP)

Familial adenomatous polyposis (FAP) is a premalignant disease inherited as an autosomal dominant trait, characterized by hundreds to thousands of polyps in the colorectal tract. Recently, the syndrome has been shown to be caused by mutations in the APC (adenomatous polyposis coli) gene located on chromosome 5q21. We studied two families that both presented a phenotype different than that of the classical form of FAP. The most important findings observed in these two kindreds are (a) low and variable number of colonic polyps (from 5 to 100) and (b) a slower evolution of the disease, with colon cancer occurring at a more advanced age than in FAP in spite of the early onset of intestinal manifestations. To determine whether mutations of the APC gene are also responsible for this variant syndrome, linkage studies were performed by using a series of markers both intragenic and tightly linked to the APC gene. The results provide evidence for exclusion of the APC gene as the cause of the variant form of polyposis present in the two families described.

Subcutaneous recombinant human erythropoietin for the treatment of anemia in myelodysplastic syndromes

Recombinant human erythropoietin (rhEPO) was administered subcutaneously to 13 anemic (Hb < 10 g/dl) patients with myelodysplasia (MDS). rhEPO was given 3 times a week at doses of 75-250 U/kg body weight, over a maximum period of 24 weeks. Five patients (38%) showed a response to rhEPO treatment. rhEPO was well tolerated and without relevant side effects throughout the study. All responding patients had low but detectable pretreatment circulating erythroid progenitor cells (BFU-E) and the response to rhEPO was associated with a significant increase in BFU-E (p < 0.01); concentrations of serum transferrin receptor (TfR) also consistently rose in all responding patients. Baseline erythropoietin (EPO) concentrations did not significantly differ between responders and nonresponders, although 4 out of the 5 responders had relatively low levels of EPO. In conclusion, subcutaneous rhEPO administration appears to be an effective treatment of anemia in a substantial subset of patients with MDS. Relatively low baseline EPO concentrations, detectable pretreatment circulating BFU-E and an early increase in the serum concentrations of TfR seem to be criteria for predicting response to rhEPO in patients with MDS.

Linkage studies in Italian families with familial adenomatous polyposis

Linkage analysis was performed on 188 subjects belonging to 18 Italian families segregating for familial adenomatous polyposis (FAP) using 7 polymorphic markers (5 restriction fragment length and 2 dinucleotide repeat polymorphisms) mapping in 5q21. A two-point linkage analysis performed with the LINKAGE program gave significant lod scores (> 3) between the Pi227, C11p11, YN5.64, YN5.48 probes and the disease, whereas the ECB27, CB83 and EF5.44 markers showed lower lod scores. Some 11 recombination events were identified from the analysis of 101 meioses. The best map that we could determine confirmed that reported in previous studies. The location of the new marker, CB83, lying between YN5.64 and YN5.48, remains imprecise. No genetic heterogeneity was detected, with all the families showing linkage for at least one of the probes. One 34-year-old individual having an affected haplotype was however classified as healthy after clinical examinations. The results confirm the applicability of the linkage approach for presymptomatic diagnosis of FAP.

Familial adenomatous polyposis: identification of a new frameshift mutation of the APC gene in an Italian family

Familial Adenomatous Polyposis (FAP) is a premalignant disease of the gastrointestinal tract inherited as an autosomal dominant trait assigned to chromosome 5q21. The 15 exons of the APC gene responsible for the defect were amplified from the DNA of one FAP patient. SSCP analysis of the amplified DNA revealed a variant conformer of exon 10. The sequencing of the cloned PCR product showed a 1 base insertion at position 1370, creating a stop codon four nucleotides downstream. SSCP analysis of 20 family members and nucleotide sequencing of exon 10 in three affected members confirmed the Mendelian inheritance of the mutant allele.

Karyotype evolution of Ph positive chronic myelogenous leukemia patients relapsed in advanced phases of the disease after allogeneic bone marrow transplantation

Sixty-eight patients affected by Philadelphia chromosome (Ph) positive chronic myelogenous leukemia (CML) underwent allogeneic bone marrow transplantation (BMT) and were successfully studied from a cytogenetic point of view, before and after the BMT. Nineteen had evidence of cytogenetic and clinical relapse. Cytogenetic analyses of 14 patients who, after the relapse, showed progression to the accelerated or blastic phase of the disease, are presented. Five of these cases had only the Ph chromosome without karyotype evolution; in one case Ph duplication without other anomalies was detected, while in the remaining eight cases cytogenetic analysis showed apparently random clonal structural abnormalities (translocations, inversions, deletions, and marker formations). Therefore, the classical "non-random" abnormalities (+8, i(17q), +Ph, +19, +21) were not as common as in conventionally treated Ph+ CML. From our data, karyotype evolution during advanced phases in Ph+ CML patients after BMT differs from the evolution seen in conventionally treated patients, by the presence of numerous structural unusual abnormalities, possibly related to radiochemotherapy conditioning to BMT. Therefore, BMT treatment is not always able to eradicate the Ph+ clone but can reduce the incidence of the formation and/or expansion of Ph+ clones with additional non-random abnormalities.

Early and long term follow-up with minisatellite probes in bone marrow transplanted patients

Twenty-five patients who received bone marrow transplantation (BMT) for chronic granulocytic leukemia (CGL), acute leukemia and severe aplastic anemia were studied before and after BMT in order to document and characterize the events following transplantation. DNA analysis was performed using minisatellite probes, which give rise to extremely polymorphic Southern blot band patterns specific to each individual and are regarded as "genetic fingerprint." Sensitivity studies using a mixture of donor and recipient cells could distinguish the presence of 1% of cells from one individual. Blood specimens were obtained from donor recipient before BMT and at days 10, 30, 90, and 270 after BMT. Karyotype analysis was also performed in CGL patients at the same time of DNA analysis. Engraftment was identified by DNA analysis as early as 10 days posttransplant and correlated with cytogenetic findings. This confirmed that a single hybridization filter is informative in 100% of patients and is easily applicable for early and long term studies of chimerism in BM transplanted patients.

Molecular analysis of Philadelphia-negative myeloproliferative syndromes with i(17q)

We report two cases of myeloproliferative syndromes in which the only karyotypic abnormality was an isochromosome of the long arm of chromosome 17. Because i(17q) is a nonrandom structural aberration found in nearly 12% of cases of Philadelphia (Ph)-positive chronic myelogenous leukemia (CML), we carried out a molecular analysis of the breakpoint cluster region (bcr) to verify the presence of genomic rearrangements characteristic of CML. The interest of the study was strengthened by the fact that i(17q) is frequently seen in CML and by recent reports showing that genomic changes of c-abl and bcr genes can be present even in the absence of a Ph chromosome. One of the two patients showed the presence of a rearranged fragment within the bcr, suggesting a Ph-positive CML diagnosis.

Translocation t(9;9)(p13;q34) in Philadelphia-negative chronic myeloid leukemia with breakpoint cluster region rearrangement

Chromosome analysis showed a t(9;9)(p13;q34) in a patient with chronic myeloid leukemia (CML) without a Philadelphia (Ph) chromosome in all examined cells. Southern blot analysis of leukocyte DNA revealed rearrangement of breakpoint cluster region (bcr) within the 5.8-kb bcr sequences as in Ph-positive CML patients. The findings confirm that the 9q34 and 22q11 bands are always involved in CML independent of the chromosomal evidence. It is suggested that Ph-negative bcr-positive CML may have variant translocations, as in the case of the t(9;9) reported here.

Cytogenetic follow-up after bone marrow transplantation for Philadelphia-positive chronic myeloid leukemia

Forty-eight consecutive patients affected by chronic myelogenous leukemia (CML) Philadelphia (Ph) chromosome positive during the chronic phase of the disease underwent allogeneic bone marrow transplantation (BMT). Thirty-five patients had a follow-up over 12 months and were included in a cytogenetic study in order to evaluate the Ph clone eradication. In 25 cases, the Ph chromosome disappeared in all cytogenetic studies, and their hematologic picture is at present apparently normal. Ten patients showed cytogenetic relapse. In one case, the cytogenetic relapse was transitory without any clinical sign of the disease; in three cases, after a transitory cytogenetic relapse, a persistent relapse with clinical picture of progression of the disease occurred; in six cases cytogenetic and a clinical relapse were coincident. Structural chromosomal abnormalities other than Ph were temporarily seen in three cases. The so-called "nonrandom" chromosomal changes typical of the blastic phase were never detected. The reappearing Ph-positive clone spontaneously disappeared in three patients, and their hematologic picture reverted to complete chimerism. The present study confirms that the eradication of the Ph clone is often defective with BMT, and cytogenetic analysis can detect the competition between donor and residual host marrow. Furthermore, the karyotype evolution is different from that found in CML patients treated with conventional chemotherapy.

Amplification of c-myc and pvt-1 homologous sequences in acute nonlymphatic leukemia

Leukemic cells with double minute (DM) chromosomes from an ANLL(M1) patient were found to carry 10-15 fold amplified c-myc sequences. The linked pvt-1-like locus was amplified at the same level, suggesting that the c-myc amplicon is at least 300 kb in size.

Acute myelogenous leukemia with translocation t(8;21): a cytogenetic study of seven cases

Seven cases of acute nonlymphoblastic leukemia showing t(8;21)(q22;q22) at diagnosis are described. Involvement of a sex chromosome was found in all patients (in six cases as a loss, and in one as a Y duplication), thus, confirming the suggestion of a correlation between these two chromosomal abnormalities. The constitutional folic acid-sensitive fragile site fra(8)(q22) was not detected, in spite of careful analysis of over 300 metaphases of cells grown in folic acid-free medium. Morphologic diagnoses and clinical aspects are briefly discussed.

Involvement of chromosomal region 9q34 in a case of variant Ph1 translocation t(22;22)

In a patient with chronic myelocytic leukemia chromosome analysis showed a translocation (22;22) (q13;q11). Chromosomes 9 were apparently not involved. Using somatic cell hybrids and a v-abl probe, we demonstrated the translocation of c-abl sequences from chromosome 9 to chromosome 22q-. This confirms the hypothesis that the translocation of c-abl oncogene is essential for the development of Ph1 positive CML.

Favism: looking for an autosomal gene associated with glucose-6-phosphate dehydrogenase deficiency

Favism is a severe, acute haemolytic anaemia which occurs in about 20% of G6PD deficient subjects after ingestion of fava beans. Since not all G6PD deficient subjects are sensitive to fava beans, the possibility has been suggested that extra erythrocytic factors may play an important role in the susceptibility to haemolytic favism. To test the hypothesis that an autosomal enzyme is involved in the pathogenesis of favism, we carried out a beta-glucosidase assay in small intestine biopsies from normal subjects and G6PD deficient subjects with or without favism. Beta-glucosidase might be involved in the absorption and metabolism of fava beans and a quantitative polymorphism could explain the different susceptibility to fava beans of G6PD deficient subjects. Our observation showed no consistent quantitative polymorphism of beta-glucosidase in the subjects examined.

Reexpression of normal stem cells in erythroleukemia during remission

A patient with erythroleukemia and heterozygous for the Mediterranean variant of the X-linked enzyme glucose-6-phosphate dehydrogenase (G6PD) was studied to determine the number and type of progenitor cells in which the disease arose. G6PD mosaicism was assessed by the different rate of utilization of 2-deoxy-glucose-6-phosphate (2dG6P) by normal and Mediterranean variants of G6PD. Erythroleukemia is established as a clonal disease involving a precursor cell common to the erythroid and myeloid lines. After intensive chemotherapy, restoration of nonmonoclonal hemopoiesis is achieved, as indicated by the reappearance of the mosaic phenotype in hemopoietic cell populations.

Regulation of glucose 6-phosphate dehydrogenase expression in CHO-human fibroblast somatic cell hybrids

Human--hamster somatic cell hybrids have been obtained by fusion of a CHO line (NA31) doubly deficient in hypoxanthine guanine phosphoribosyltransferase and glucose 6-phosphate dehydrogenase (G6PD) with normal G6PD(+) human fibroblasts. Analysis of NA31 extracts has revealed that, although G6PD activity is nearly absent, significant activity can be detected with 2-deoxyglucose 6-phosphate as substrate, so that the mutant and normal forms of the enzyme can both be easily detected. The cell hybrids obtained express human G6PD. The human G6PD subunits are distributed in homodimeric molecules as well as in human--hamster heterodimeric molecules. However, whereas the amount of hamster G6PD subunits present in the hybrid is similar to that in the hamster parental cells, the amount of human G6PD subunits is decreased by 3- to 10-fold when compared to the human parental cell. These results indicate that either the expression of the G6PD gene or the stability of the gene product is altered in the hybrid. By mutagenesis and selection in diamide (a substance that oxidizes intracellular glutathione), we have isolated a clone with a 3- to 5-fold increase in human G6PD activity. This derivative may have an increased rate of expression of the human G6PD structural gene.

A new glucose 6-phosphate dehydrogenase variant (G-6-PD Verona) in a patient with myelodysplastic syndrome

A 67-year-old woman investigated because of 'myelodysplastic syndrome' was found to have a 4-fold increase in G-6-PD activity in her erythrocytes. The enzyme was partially purified and characterized. On grounds of: (a) reduced electrophoretic mobility, (b) abnormal cathodic band(s) in isoelectrofocusing, (c) increased Michaelis constant for glucose 6-phosphate, (d) abnormal thermostability, and (e) abnormal interaction with the ligand NADPH, we conclude that this is a new structural variant which we designate G-6-PD Verona. G-6-PD Verona was the sole apparent source of G-6-PD activity in the patient's erythrocytes; by contrast, the patient's fibroblasts had only normal G-6-PH (type B). The patient's haematological course terminated into acute myeloid leukaemia. We believe G-6-PD Verona was the result of a somatic mutation in an X-chromosome which took place in a haemopoietic cell clone which subsequently underwent neoplastic transformation.

Derepression with decreased expression of the G6PD locus on the inactive X chromosome in normal human cells

Studies of a unique clone of skin fibroblasts from a normal 46 XX female reveal that the G6PD locus on the inactive X chromosome has been derepressed. The reactivation event occurs spontaneously, and is associated with normal karyotype, including the presence of a late-replicating X chromosome. Analysis of mouse-human hybrids with the relevant chromosome provides evidence that the derepressed locus is on the inactive X, and that reactivation is not extensive (the PGK locus is not derepressed). Nor is any general change in DNA methylation of this chromosome detectable with Hpa II and an X-specific DNA probe. Studies of the glucose-6-phosphate dehydrogenase phenotype in these heterozygous cells indicate that the reactivated X produces only half the enzyme subunits as are produced by the active X. Although this dosage difference may be related to the mutational event responsible for derepression of the locus, these observations along with other evidence suggest that loci on the inactive X, when expressed, have less activity than corresponding loci on the active X.

Fragile X syndrome: search for phenotypic manifestations at loci for hypoxanthine phosphoribosyltransferase and glucose-6-phosphate dehydrogenase

The subjects of this study were individuals with the form of X-linked mental retardation that is associated with the presence of a cytologically variant X chromosome having a secondary constriction or "fragile site" at Xq 27-28 (Fra X). Studies were carried out to test the hypothesis that deletions or modifications at neighboring loci occur as a consequence of events at the fragile site. Skin fibroblasts and peripheral blood lymphocytes from affected males were analyzed with respect to the expression of two X-lined enzymes: glucose-6-phosphate dehydrogenase (G6PD) and hypoxanthine phosphoribosyltransferase (HPRT); loci for these enzymes are known to be located in the region of the fragile site. Although the number of cells resistant to thioguanine (HPRT-deficient) obtained from some cultures from one Fra X male and blood cells of another was greater than expected, the frequency of these cells was not increased in cultures from other Fra X males. Furthermore, our results indicate that the G6PD activity and electrophoretic mobility in Fra X males is similar to that in normal cells, thus providing no evidence for the loss of the long-arm telomere in the fragile X syndrome.

New genetic variants of glucose 6-phosphate dehydrogenase (G6PD) in Italy

Six new variants of human erythrocyte G6PD have been characterized. All of them were found in Italian males and all were associated with enzyme deficiency, but only two with signs of haemolysis. These and other variants reported in the literature, which must thus far be regarded as sporadic, are found to map in parts of Italy where common types of G6PD deficiency are also prevalent.

Favism: erythrocyte metabolism during haemolysis and reticulocytosis

The reduced activity of glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate; NADP+ 1-oxidoreductase; G6PF) in Mediterranean erythrocytes explains the precarious equilibrium of the hexose monophosphate pathway (HMP) and the susceptibility of these cells to haemolytic agents. G6PD-deficient erythrocytes, in steady-state conditions, have a low NADPH/NADP+ ratio, thus allowing the HMP to operate at its maximal intracellular rate and to compensate the intrinsic erythrocyte enzyme deficiency. Studies started soon after accidental intake of fava beans by sensitive G6PD-deficient subjects demonstrate a decrease of both NADPH/NADP+ ratio and reduced glutathione. The metabolic effects induced by fava beans may be attributed to oxidative stress probably associated with an inhibitor effect of some unknown metabolite on the HMP. The availability of erythrocytes from subjects recovering from haemolysis with high reticulocyte counts and increased G6PD activity, provides new information on the rate of synthesis as well as on the in vivo decay of the mutant enzyme. Correlation of G6PD activity to reticulocyte count and extrapolation to an ideally homogenous population of reticulocytes reveal that the mutant enzyme is synthesized at a nearly normal rate. Furthermore, the present correlation allows an estimate of the in vivo half-life of Mediterranean G6PD. The rate of decline of about 8 d observed in this study well correlates to the intracellular metabolic aspects of G6PD Mediterranean erythrocytes.

Effect of haemolysis on the hexose monophosphate pathway in normal and in glucose-6-phosphate dehydrogenase-deficient erythrocytes

The hexose monophosphate pathway of human glucose-6-phosphate dehydrogenase (EC 1.1.1.49) - deficient erythrocytes is under a severe and unexplained restraint (Gaetani, G.D., Parker, J.C. and Kirkman, H.N. (1974) Proc. Natl. Acad. Sci. U.S. 71, 3584-3587). In this study the hexose monophosphate pathway activity and the NADPH level of normal and glucose-6-phosphate dehydrogenase-deficient erythrocytes were measured soon after haemolysis. The results indicate a prompt increase in 14CO2 evolution and a rise in MADPH levels. Since, in this study, the concentration of the haemolysate is comparable to that of intact erythrocytes, the relief of the restraint on glucose-6-phosphate dehydrogenase through dilution-dependent dissociation from inactivator or inhibitor is excluded. The possibility that the intracellular restraint may result from compartmentalization of glucose-6-phosphate dehydrogenase and substrates or from properties of the intact membrane of the erythrocytes is suggested.

NADP+ and NADPH in glucose-6-phosphate dehydrogenase-deficient erythrocytes under oxidative stimulation

A mild oxidative stimulation of the hexose monophosphate pathway of human glucose-6-phosphate dehydrogenase (EC 1.1.1.49)-deficient erythrocytes (Mediterranean variant) causes a significant drop in NADPH. These results, other than to confirm that glucose-6-phosphate dehydrogenase deficiency is a product deficiency disorder, demonstrate that under oxidative stimulation glutathione reductase may become functionally impaired and GSSG cannot be reduced at a sufficient rate.

Haemolytic effect of two sulphonamides evaluated by a new method

A technique to investigate drugs which could cause haemolysis in subjects deficient in glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP oxidoreductase; G6PD) has been developed. The method is based on the technique of 14CO2 evolution during the incubation of normal erythrocytes in the presence of [I-14C]glucose and their own serum, the latter containing the active metabolites of the drugs received by normal subjects. By this method agents causing a stimulation of the hexosemonophosphate pathway of normal erythrocytes should be regarded as potentially haemolytic for G6PD-deficient subjects. Two sulphonamides, sulphormethoxine and sulphalene, of which until now no haemolytic effects have been reported, together with chloroquine, have been investigated. While chloroquine does not affect the hexosemonophosphate shunt of normal erythrocytes, the two sulphonamides stimulate this pathway. THE RESULTS ARE CONFIrmed by the reduction of the half-life of 51Cr-labelled G6PD-deficient red cells (Mediterranean variant), after administration of the two sulphonamides.

Red cell NADP+ and NADPH in glucose-6-phosphate dehydrogenase deficiency

Extraction in the presence of sodium hydroxide and cysteine allows estimates of NADPH and total NADP in human red cells without the erroneously high values of NADP+ obtained with earlier methods. An application of this technique to G6PD-deficient cells reveals that most of the nucleotide is in the oxidized form. In contrast, normal red cells have nearly all of the nucleotide in the reudced form. In addition to providing information concerning the intracellular regulation of the hexose monophosphate shunt, these findings support the concept that G6PD deficiency is a product-deficiency disorder.