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Biomedical subjects

B Quesnel

Publications and source records attributed to B Quesnel.

50 records · Page 3Linked to original sources
PubMed1995

c-mpl expression in hematologic disorders.

The c-mpl gene encodes a member of the hematopoietic cytokine receptor superfamily. This gene was discovered through the study of a murine retrovirus which induces an acute myeloproliferative syndrome in mice. MPLV (for myeloproliferative leukemia virus) has transduced a truncated and constitutively activated form of the c-mpl receptor chain. The c-mpl ligand is unknown, but recent data indicate that it could specifically regulate thrombocytopoiesis. This review focuses on the expression of the c-mpl gene in a large series of human hematopoietic pathologies by Northern blot analysis. Barely detectable transcript levels were detected in normal bone marrow (BM) and in BM samples from chronic myeloproliferative disorders, plasmocytoma, Burkitt lymphoma or acute lymphoid leukemia. In contrast, high levels of c-mpl expression were detected in 45% of acute myeloid leukemia (AML). No correlation was found between c-mpl expression and the French-American-British classification subtype of AML. However c-mpl expression correlated with CD34 expression, and unfavorable cytogenetic abnormalities, defining a subgroup of AML with a low rate of complete remission. In myelodysplasia, c-mpl expression was elevated in 44% of chronic myelomonocytic leukemia (CMML), 42% of refractory anemia with excess myeloblasts (RAEB), and RAEB in transformation to acute leukemia (RAEBt), but not in refractory anemia (RA) and RA with ringed sideroblasts (RARS). In CMML, there was no correlation between c-mpl expression and any prognostic factor tested, nor with the course of the disease. The biologic significance of c-mpl expression in RAEB and RAEBt is probably different.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The retinoblastoma gene (RB-1) status in multiple myeloma: a report on 35 cases.

We looked for abnormalities of the retinoblastoma (RB-1) gene and of RB protein expression in 35 patients with multiple myeloma (MM). Mutations in exons 20 to 24 of the RB-1 gene (exons where mutations predominate in retinoblastoma and other solid tumors) were analyzed by single stranded conformation polymorphism (SSCP). RB-1 protein was studied in bone marrow plasma cells by immunocytochemistry (ABC peroxidase technique) with a specific monoclonal antibody. Southern blot analysis of RB-1 gene was also performed in 20 of the patients. Twenty two patients analyzed had advanced disease (stage III or, in one case, plasma cell leukemia) and cytogenetic analysis (performed in 31 cases) found monosomy 13 in 9 patients. No rearrangement of the RB-1 gene was found by Southern analysis. Absent or greatly reduced RB-1 protein level was found in plasma cells in 4 of the patients (11%), whereas normal levels were seen in the remaining cases. No point mutation in exons 20 to 24 and their flanking introns were found in any of the 35 patients. Three of the 4 patients with absent or reduced RB-1 protein expression had advanced MM (stage III: 2 cases; plasma cell leukemia: 1 case); all 4 patients were resistant to treatment (as compared to 7 of the 31 patients with normal RB-1 protein levels); only one of them was subsequently found to have monosomy 13 (as compared to 9 of the 28 other karyotyped patients). Our findings suggest that abnormalities of the RB-1 gene and its expression are rare in MM. Absent or reduced expression of RB-1 protein was not significantly correlated to monosomy 13 and was not associated with gross rearrangements of the RB-1 gene by Southern analysis or point mutations in exons 20 to 24 of the gene. Reduced expression of RB-1 protein may be associated with advanced disease and poor response to treatment, although larger numbers of patients will be required for more adequate conclusions.

Base Sequence↗
PubMed1994

p53 mutations are associated with resistance to chemotherapy and short survival in hematologic malignancies.

We analyzed the prognostic value of p53 mutations for response to chemotherapy and survival in acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and chronic lymphocytic leukemia (CLL). Mutations were detected by single-stranded conformation polymorphism (SSCP) analysis of exons 4 to 10 of the P53 gene, and confirmed by direct sequencing. A p53 mutation was found in 16 of 107 (15%) AML, 20 of 182 (11%) MDS, and 9 of 81 (11%) CLL tested. In AML, three of nine (33%) mutated cases and 66 of 81 (81%) nonmutated cases treated with intensive chemotherapy achieved complete remission (CR) (P = .005) and none of five mutated cases and three of six nonmutated cases treated by low-dose Ara C achieved CR or partial remission (PR) (P = .06). Median actuarial survival was 2.5 months in mutated cases, and 15 months in nonmutated cases (P < 10(-5)). In the MDS patients who received chemotherapy (intensive chemotherapy or low-dose Ara C), 1 of 13 (8%) mutated cases and 23 of 38 (60%) nonmutated cases achieved CR or PR (P = .004), and median actuarial survival was 2.5 and 13.5 months, respectively (P < 10(-5)). In all MDS cases (treated and untreated), the survival difference between mutated cases and nonmutated cases was also highly significant. In CLL, 1 of 8 (12.5%) mutated cases treated by chemotherapy (chlorambucil and/or CHOP and/or fludarabine) responded, as compared with 29 of 36 (80%) nonmutated cases (P = .02). In all CLL cases, survival from p53 analysis was significantly shorter in mutated cases (median 7 months) than in nonmutated cases (median not reached) (P < 10(-5)). In 35 of the 45 mutated cases of AML, MDS, and CLL, cytogenetic analysis or SSCP and sequence findings showed loss of the nonmutated P53 allele. Our findings show that p53 mutations are a strong prognostic indicator of response to chemotherapy and survival in AML, MDS, and CLL. The usual association of p53 mutations to loss of the nonmutated P53 allele, in those disorders, ie, to absence of normal p53 in tumor cells, suggests that p53 mutations could induce drug resistance, at least in part, by interfering with normal apoptotic pathways in tumor cells.

Adult↗
PubMed1994

MDM2 gene amplification in human breast cancer.

The MDM2 gene is a gene whose product binds to p53 and regulates its functions. The amplification of the MDM2 gene has been found in one third of human sarcomas, and a differential expression of MDM2 gene in relation with oestrogen receptor status was recently found in human breast cancer cell lines. We analysed 60 breast cancers for MDM2 gene amplification by Southern blot. This event was observed in 1 case with high levels of oestrogen receptor (ER). Thus, MDM2 gene amplification seems to be a rare event in breast cancer. Further studies are needed to define precisely the relationship between MDM2 amplification and ER status.

Blotting, Southern↗
PubMed1994

Inactivation of the retinoblastoma gene appears to be very uncommon in myelodysplastic syndromes.

Rearrangements of the retinoblastoma (RB) gene have been reported in a few cases of myelodysplastic syndromes (MDS). In addition, low or absent expression of the RB protein is found in 20-30% of cases of acute myeloid leukaemias (AML), particularly in AML with a monocytic component (M4 or M5). We performed Southern blot analysis of the RB gene in 90 cases of MDS, including 37 cases of chronic myelomonocytic leukaemia (CMML). None of them had progressed to AML at the time of study. In 37/90 patients (including 20 CMML) Northern blot analysis, study of RB protein by immunocytochemistry on bone marrow slides, and detection of point mutations in exons 20-24 of the RB gene was also made, using single strand conformation polymorphism analysis (SSCP). No abnormal Southern profile was found in any of the 90 patients. Northern blot and immunocytochemical study of RB protein were normal in the 37 cases studied. SSCP analysis detected a point mutation in 2/37 patients tested. Direct sequencing confirmed the mutation in each case, which involved intron 21 and intron 23, respectively, and was located outside splicing sites of the neighbouring exons. These findings suggest that abnormalities of the RB gene and its expression must be very rare in MDS, and play a minor role, if any, in the pathophysiology of those disorders, at least before progression to AML.

Base Sequence↗
PubMed1994

Over-expression of the MDM2 gene is found in some cases of haematological malignancies.

We looked for MDM2 gene amplification and over-expression by Southern and Northern blot analysis in 135 and 66 cases of haematological malignancies, including ALL, AML, CML in chronic phase, CLL, MDS, PLL, non-Hodgkin's lymphoma (NHL) and myeloma. No amplification of the gene was found. An over-expression of MDM2 RNA was seen in 9/66 (14%) patients tested, including 3/9 ALL, 3/24 AML, 2/4 myelomas, 1/1 PLL, but 0/2 CML, 0/2 NHL and 0/21 MDS. None of the patients over-expressing MDM2 had modifications of P53 gene transcript or p53 mutations. Most of the patients over-expressing MDM2 gene had poor prognostic features (including 'unfavourable' cytogenetic abnormalities), poor response to chemotherapy and short survival. Our findings suggest that over-expression of MDM2 is seen in a relatively small number of haematological malignancies, and is associated with poor prognosis.

Aged↗
PubMed1994

Detection of p53 mutations in hematological malignancies: comparison between immunocytochemistry and DNA analysis.

The wild type p53 protein has a short half-life and cannot be detected by immunohistochemistry on tissue sections. Mutated p53, on the other hand, has a prolonged half-life and becomes detectable by this method, so that its detection by immunohistochemistry in solid tumors is almost synonymous with mutation. We assessed the value of immunocytochemical analysis of p53 protein on blood or bone marrow slides in the detection of p53 mutation in hematological malignancies, by comparison with single-stranded conformation polymorphism (SSCP) analysis of exons 4 to 10 of the P53 gene. One hundred and twenty eight patients with acute myeloid leukemia (AML), acute lymphoid leukemia (ALL), myelodysplastic syndromes (MDS), or chronic lymphocytic leukemia (CLL) were studied by both methods. Immunocytochemistry showed detectable levels of intracellular p53 in 19 cases (including 2/19 AML, 2/21 ALL, 11/48 MDS, 4/40 CLL). Staining by p53 antibodies was restricted to the nucleus of blasts in AML, ALL, and MDS, and of lymphocytes in CLL. In 16 of the 19 cases, SSCP analysis, followed by direct sequencing, showed a p53 missense mutation in exons 4 to 8 of the gene. In the remaining three cases, where the number of cells stained by p53 antibodies was small, no p53 mutation could be detected. On the other hand, SSCP and sequence analysis identified a p53 mutation in two patients who had negative immunocytochemical findings. Both cases had a nonsense mutation, presumably leading to reduced levels of truncated p53. Thus, overall, immunocytochemistry and SSCP gave concordant results in 123 of the 128 (96%) patients analyzed. Our findings show that immunocytochemistry on blood and bone marrow smears is a sensitive method of p53 mutation detection in hematological malignancies, except in the rare patients with chain-terminating mutations. Positive immunocytochemistry is found in some patients with normal SSCP findings, and could correspond to overexpression of a non-mutated p53, but also to p53 mutation in a minor proportion of the malignant cells, undetectable by SSCP.

Anemia↗
PubMed1994

Absence of rearrangement of the neurofibromatosis 1 (NF1) gene in myelodysplastic syndromes and acute myeloid leukemia.

Neurofibromatosis 1 (NF1) disease is associated with an increased incidence of leukemias and the NF1 gene product acts as a negative regulator of the product of RAS genes which are often activated in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) through point mutations. Thus, we looked for abnormalities of the NF1 gene by Southern analysis in 35 cases of MDS and eight cases of AML, using cDNA probes covering the whole coding sequence. Fourteen of the patients had monosomy 17 (i.e. had lost one allele of the NF1 gene, situated in 17q11-2). Neither rearrangement nor deletion was found in any patient, suggesting that gross abnormalities of the NF1 gene must be very rare in MDS and AML. This does not exclude the possibility of more subtle abnormalities, such as point mutations, in some cases.

Adult↗
PubMed1993

Therapy-related acute myeloid leukemia with t(8;21), inv(16), and t(8;16): a report on 25 cases and review of the literature.

PURPOSE: To analyze therapy-related acute myeloid leukemias (tAMLs) with t(8;21), inv(16), or t(8;16). PATIENTS AND METHODS: Twenty-five patients with tAML and t(8;21)(q22;q22), inv(16)(p13;q22), or t(8;16)(p11;p13) from seven centers, along with 23 previously published cases, were studied. RESULTS: Twenty-six, 16, and six patients, respectively, had t(8;21), inv(16), and t(8;16). Prior cancer was a solid tumor in 27 cases, and a hematologic malignancy in all other patients. Five patients had received prior radiotherapy (RT) alone, and 43 had received prior chemotherapy with or without RT. Prior chemotherapy included a drug that directly reacts with DNA (alkylating agent or cisplatin) and/or an agent that targets topoisomerase II (ATTop, an anthracycline or derivative or, less often, epipodophyllotoxin) in most patients. The interval between prior tumor and diagnosis of tAML was less than 3 years in most cases, and only seven patients had a preleukemic phase of disease. Morphology was M2 AML for t(8;21), M4eo for inv(16), and M4 or M5 for t(8;16). Sixteen of 21 (76%), 12 of 14 (86%), and zero of four patients with t(8;21), inv(16), and t(8;16), respectively, achieved complete remission (CR) with intensive chemotherapy. The actuarial disease-free survival rate at 24 months was 47% and 54% in patients with t(8;21) and inv(16), respectively. CONCLUSION: Like other tAMLs with a karyotype specific of de novo AML [balanced 11q23 rearrangement or t(15;17)], tAMLs with t(8;21), inv(16), or t(8;16) are usually characterized by a short latent period, previous treatment often combining a drug that directly reacts with DNA and an ATTop, and absence of preleukemic phase. Hematologic characteristics and response to treatment are also identical to those of de novo AML with the same karyotypes.

Actuarial Analysis↗
PubMed1993

Relationship between p53 gene mutations and multidrug resistance (mdr1) gene expression in myelodysplastic syndromes.

P glycoprotein, the product of multidrug resistance (mdr1) gene, is frequently expressed in advanced myelodysplastic syndromes (MDS) with an excess of bone marrow blasts and could explain their frequent resistance to chemotherapy. P53 gene mutations are also found in 10 to 15% of advanced MDS. Because it has recently been suggested that normal p53 suppressed, but that mutated p53 activated, the mdr1 gene promoter, we tried to correlate p53 mutations and P glycoprotein expression in 34 patients with MDS and an excess of bone marrow blasts (> 5%). P glycoprotein expression was assessed by immunocytochemistry using JSB1 monoclonal antibody and was found positive in 13 out of the 34 patients. p53 mutations were detected both by immunocytochemistry using three different monoclonal antibodies and by single stranded conformation polymorphism (SSCP) analysis of exons 5 to 8 of the P53 gene. Both methods detected a point mutation in 5 out of the 34 patients. Only one out of the 5 patients with a p53 mutation expressed P glycoprotein, as compared to 12 out of the 29 patients without p53 mutations. This suggested the mutant and normal p53 are not major determinants of the regulation of mdr1 expression in vivo, at least in MDS.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Absence of amplification of MDM2 gene, a regulator of p53 function, in myelodysplastic syndromes.

The MDM2 gene is a gene whose product binds to p53 and regulates its function. Amplification of MDM2 has been found in human sarcomas, where it leads to inactivation of p53. In 64 cases of generally advanced myelodysplastic syndromes, we found no amplification or rearrangement of MDM2 gene by Southern analysis. MDM2 RNA was also normal in the 15 cases where Northern analysis was made. Thus, amplification of MDM2 is not seen or must be very rare in myelodysplastic syndrome (MDS). Because P53 gene mutations are not frequent in MDS, inactivation of p53 seems to be, overall, a rare pathogenetic event in MDS.

Blotting, Southern↗