The BCL-2 protein in precursor B acute lymphoblastic leukemia in children.

The BCL-2 protein plays an important role in controlling apoptosis. Disorders of this process can lead to the emergence and development of acute lymphoblastic leukemia (ALL) and can determine the resistance of leukemic cells to chemotherapy. The levels of BCL-2 mRNA were determined in 20 children with pre-B ALL using RT-polymerase chain reaction and the percentage of BCL-2+ cells in 51 patients using flow cytofluorometry. Similar levels of BCL-2 mRNA (P=0.18) with a higher percentage of cells BCL-2+ (P=0.04) were shown in the bone marrow of patients with pre-B ALL compared to normal peripheral blood mononuclear cells. We could not find any connection between the level of BCL-2 mRNA or the percentage of BCL-2+ cells and selected clinical features. A high percentage of BCL-2+ cells and high levels of BCL-2 mRNA did not affect the 5-year overall survival probability nor the 5-year relapse-free survival probability. These results may indicate a high activity of mechanisms promoting the development of the final form of the BCL-2 protein from mRNA in leukemic cells. A high BCL-2 level does not affect the clinical course or worsen the prognosis in children with ALL.

Polymorphisms of ABCB1, CYP3A4 and CYP3A5 Genes in Ovarian Cancer and Treatment Response in Poles.

BACKGROUND/AIM: Ovarian cancer is a lethal gynecological malignancy, with 5-year survival of only about one third of patients. The ABCB1 gene encodes the P-glycoprotein which is one of the multidrug efflux pumps. Its decreased activity may result in multidrug resistance of cancer cells. Drug-metabolizing enzymes Cyp3A4 and Cyp3A5 may affect success of chemotherapy. In this study we attempted to examine the effects of 12 single nucleotide polymorphisms (SNPs) of the ABCB1 gene and one SNP in each of CYP3A4 and CYP3A5 genes on the incidence of ovarian cancer in Polish women and their response to treatment. MATERIALS AND METHODS: Our study included 276 patients and 369 healthy control women. RESULTS: The results showed no significant differences between patients and controls in allele frequencies of the tested SNPs, with one exception: rs2157926T allele decreased cancer risk by 99.4% (odds ratio, 0.006). Moreover, rs2032582T increased fourfold the risk of metastasis. Finally, rs1128503CC genotype prolonged survival (p=0.024778). CONCLUSION: These findings may contribute to a better prediction of therapy outcome.

Evidence for selective expression of the p53 codon 72 polymorphs: implications in cancer development.

Polymorphism at codon 72 of p53 results in either the arginine or proline form of p53, whose functional significance in carcinogenesis is controversial. We have investigated if the expression of these p53 polymorphs is selectively regulated, using mRNA from peripheral blood of healthy Asian (Chinese) and the Caucasian (Polish) arginine/proline (arg/pro) heterozygote subjects. Asians were found to preferentially express the pro allele whereas the Caucasians preferentially express the arg allele. On the contrary, about 75% of the heterozygote Chinese breast cancer patients preferentially expressed the arg allele, which rarely contained any somatic mutations. Moreover, histologically normal tissues from Chinese heterozygote breast cancer patients showed selective expression of the arg allele, in contrast to the preferential expression of the pro allele in heterozygote healthy normal breast tissues. Together, the data suggest that the expression of the different p53 polymorphs is selectively regulated in different ethnic populations, and that the arg allele is activated during cancer development in Asians. Thus, the expression status of the p53 polymorphs, rather than the genotypic status, might be a useful indicator for cancer susceptibility.

Is p53 intronic variant G13964C associated with predisposition to cancer?

Germline mutations of the p53 gene confer a high risk of diverse malignancies. The highest frequency of inherited p53 defects was noted in Li-Fraumeni syndrome (LFS), but almost half of the mutations were found in families with incomplete Li-Fraumeni-like syndrome (LFL), including familial breast cancer cases. Recently, a germline intronic G13964C base change of the p53 was reported as a high-risk mutation associated with familial breast cancer (LEHMAN et al. 2000). We genotyped Polish cancer patients and healthy control individuals for the G13964C variant. Patients were chosen from cancer families with phenotypes typical for germline mutations of p53 (LFS, LFL), BRCA1 [hereditary breast (ovarian) cancer, HB(O)C] or a complex consistent with both LFL and HB(O)C. Children with leukemia were included in the study as another high risk group (FELIX et al. 1992). The G13964C variant was detected in six of 87 (6.9%) cancer patients (including two ALL children), but also in eight of 96 (8.3%) control individuals (p > 0.4). Thus we found no evidence of the variant's association with a high risk of cancer.

p53 Tetramerization domain mutations: germline R342X and R342P, and somatic R337G identified in pediatric patients with Li-Fraumeni syndrome and a child with adrenocortical carcinoma.

Germline p53 mutations are associated with Li-Fraumeni syndrome (LFS) and other familial cancer phenotypes not fulfilling the definition for LFS. The majority of germline p53 mutations cluster in exons 5-8, corresponding to a DNA binding domain. We report the identification of two germline mutations and a somatic mutation in a tetramerization domain (TD), a rare site for mutations. The germline mutation, R342X (16915C>T), and the novel mutation, R342P (16916G>C), were found in a child with adrenocortical carcinoma and in a LFS pediatric patient with multiple primaries. The novel somatic mutation, R337G (16900C>G), was discovered in myelodysplastic syndrome with transformation to acute myeloblastic leukemia, developing as the third primary in the LFS child. These findings add further information on p53 TD mutations and TD contribution to tumorigenesis.

[Mean level of expression of c-myb gene in leukaemia of children]. / Poziom ekspresji genu c-myb w komórkach nowotworowych u dzieci chorych na ostre bialaczki.

AIM OF THE STUDY: Measurement of c-myb expression in leukaemia cells in children and in normal cells of healthy controls. MATERIAL AND METHODS: 37 patients, 23 boys and 14 girls with acute leukaemia, aged 1-17 years, were included in the study (32 with acute lymphoblastic leukaemia and 5 with acute myeloblasts leukaemia) Control group consisted of 17 healthy children, 8 boys and 9 girls, 4-18 years old. After the isolation of mononuclear cells from bone marrow I peripheral blood mRNA was isolated, then with the use of reverse transcriptase cDNA was synthesized. The level of expression of c-myb was analyzed with polymerase chain reaction method. The final result was analyzed as the ratio between fluorescence of c-myb gene and the control gene. RESULTS: Mean level of expression of c-myb gene in leukaemia cells was statistically significantly higher than in the control group (0.71+/-0.53 vs. 0.51+/-0.22; p=0.05), as well as c-myb level between leukaemia cells in relapse cases and controls (0.83+/-0.23 vs. 0.51+/-0.22; p=0.01). There was no difference between c-myb expression in different diagnosis. The comparison of c-myb expression in good and poor response group was not statistically significant (p=0.33). CONCLUSIONS: Possible influence of increased expression of c-myb gene in the promotion of leukaemia was found. The role of c-myb expression as a prognostic factor in acute leukaemias of children was not confirmed.

Results of p53 analysis in pediatric malignancies in Poland.

BACKGROUND: Mutations of the p53 gene are thought to be causally associated with the development of various neoplasms. In tumors overexpressing the wild-form of p53, its functional inactivation has been suggested, and MDM2 seems to be important in this process. We analyzed p53 in childhood solid tumors, as data on pediatric malignancies are still limited. PROCEDURE: The p53 gene was screened for mutations by the PCR-S SCP method and sequencing. p53, p21, and MDM2 proteins were analyzed by Western blotting. RESULTS: Overall, p53 mutations were found at a low frequency, 7% (9/126); the frequency calculated for sarcomas was also low, 8.6%. Interestingly, three of the nine detected mutations were new ones. p53 protein was demonstrated in all tumor histotypes, overall, in 63% (43/68) of the tumors, with 18% showing marked overexpression. No p21 was found; and the 76 kDa MDM2 protein was demonstrated in 18% (6/33) of the sarcomas. CONCLUSIONS: In the series of pediatric malignancies studied, the frequency of p53 mutations was very low, whereas p53 protein was present in a high fraction of the tumors. Thus, in total, p53 abnormalities were frequent.

A high proportion of founder BRCA1 mutations in Polish breast cancer families.

Three mutations in BRCA1 (5382insC, C61G and 4153delA) are common in Poland and account for the majority of mutations identified to date in Polish breast and breast-ovarian cancer families. It is not known, however, to what extent these 3 founder mutations account for all of the BRCA mutations distributed throughout the country. This question has important implications for health policy and the design of epidemiologic studies. To establish the relative contributions of founder and nonfounder BRCA mutations, we established the entire spectrum of BRCA1 and BRCA2 mutations in a large set of breast-ovarian cancer families with origins in all regions of Poland. We sequenced the entire coding regions of the BRCA1 and BRCA2 genes in 100 Polish families with 3 or more cases of breast cancer and in 100 families with cases of both breast and ovarian cancer. A mutation in BRCA1 or BRCA2 was detected in 66% of breast cancer families and in 63% of breast-ovarian cancer families. Of 129 mutations, 122 (94.6%) were in BRCA1 and 7 (5.4%) were in BRCA2. Of the 122 families with BRCA1 mutations, 119 (97.5%) had a recurrent mutation (i.e., one that was seen in at least 2 families). In particular, 111 families (91.0%) carried one of the 3 common founder mutations. The mutation spectrum was not different between families with and without ovarian cancer. These findings suggest that a rapid and inexpensive assay directed at identifying the 3 common founder mutations will have a sensitivity of 86% compared to a much more costly and labor-intensive full-sequence analysis of both genes. This rapid test will facilitate large-scale national epidemiologic and clinical studies of hereditary breast cancer, potentially including studies of chemoprevention.