Miron Prokocimer

Mutant p53 protein expression interferes with p53-independent apoptotic pathways

Loss of normal p53 function was found frequently to interfere with response of cancer cells to conventional anticancer therapies. Since more than half of all human cancers possess p53 mutations, we decided to explore the involvement of mutant p53 in drug induced apoptosis. To further evaluate the relationship between the p53-dependent and p53-independent apoptotic pathways, and to elucidate the function of mutant p53 in modulating these processes, we investigated the role of a p53 temperature-sensitive (ts) mutant in a number of apoptotic pathways induced by chemotherapeutic drugs that are currently used in cancer therapy. To that end, we studied the M1/2, myeloid p53 non-producer cells, and M1/2-derived temperature-sensitive mutant p53 expressing clones. Apoptosis caused by DNA damage induced with γ-irradiation, doxorubicin or cisplatin, was enhanced in cells expressing wild type p53 as compared to that seen in parental p53 non-producer cells; mutant p53 expressing clones were found to be more resistant to apoptosis induced by these factors. Actinomycin D, a potent inhibitor of transcription, as well as a DNA damaging agent, abrogated the restraint apoptosis mediated by mutant p53. These observations suggest that while loss of wild type p53 function clearly reduces the rate of apoptosis, p53 mutations may result in a gain of function which significantly interferes with chemotherapy induced apoptosis. Therefore, to achieve a successful cancer therapy, it is critical to consider the specific relationship between a given mutation in p53 and the chemotherapy selected.

p53 and Human Malignancies

Publisher Summary Neoplastic processes can result from the loss or inactivation of both the copies of a tumor suppressor gene or from the amplification or hyperactivation of one of the two copies of protooncogenes. The p53 gene represents both facets in its biological activity. It was considered to be an oncogene, and recently, it has been shown to function as an antioncogene in normal cells. The mutated p53 tumor antigen was shown to be a functional oncogene product that enhances the malignant process. Employing different experimental approaches, it was shown that overproduction of p53 rendered the cells malignant. Most primary tumors and cell lines expressing p53 were found to overexpress the mutated forms of the p53 protein. In the screening of Burkitts lymphoma (BL) and acute lymphatic leukemia T and B (ALL T and B), human cell lines have shown overexpression of p53 protein. The evidence supporting the notion that overexpression of the mutated p53 gene may enhance the oncogenic process in vivo was provided by generating transgenic mice carrying murine p53 genomic fragments isolated from a mouse Friend erythroleukemia cell line.

Serum CA 125 as a Prognostic factor in non-Hodgkin's lymphoma

Cancer antigen 125 (CA 125) is a glycoprotein expressed in normal tissues originally derived from coelomic epithelia such as peritoneum, pleura, pericardium, fallopian tubes and endometrium. Serum CA 125 levels are elevated in various benign and malignant conditions that involve stimulation of these tissues. Although elevated levels have been reported in patients with non-Hodgkins lymphoma (NHL), its role as a prognostic factor remained uncertain. In this study, serum CA 125 levels were measured prospectively in 108 consecutive patients with NHL: at diagnosis in 106, in remission in 39 and at relapse in 7. Levels were elevated in 43% at diagnosis. This finding was associated with advanced disease stage, bulky tumors, bone marrow involvement, extranodal disease (in stages III and IV), occurrence of B symptoms, pleural or peritoneal effusions, high serum LDH levels, high serum β2 microglobulin (β2-M) levels, elevated International Prognostic Score, poor performance status and partial or no response to treatment. No difference in CA 125 level was found between the indolent and aggressive lymphomas. Serum CA 125 levels at diagnosis had strong association with event-free and overall survival (<formula><italic>p</italic>=0.01</formula> and 0.003, respectively), with the patients with increased levels having worse survival. Patients with high CA 125 levels at diagnosis who achieved remission showed a significant decrease in CA 125 levels in remission. In conclusion, CA 125 is not only a reliable marker for staging and assessing tumor activity in NHL, elevated levels are also predictive of decreased survival.

Molecular alterations in the TP53 gene of peripheral blood cells of patients with chronic myeloid leukemia

The TP53 gene has been extensively studied in patients with chronic myeloid leukemia (CML), both in chronic phase and in blast crisis. Mutations in the gene were found in up to 30% of the patients, especially among those in blast crisis. We report the results of an analysis of 29 blood samples from CML patients: 8 samples from chronic phase patients, 8 from patients in the accelerated phase, and 13 from patients in blast crisis. By using genomic DNA, we sequenced PCR products of the coding exons and most introns of the TP53 gene, finding genetic changes in 30% of the blast crisis samples and 12% in chronic phase. All mutations were found in introns and were previously unreported. Immunocytochemical studies revealed accumulation of TP53 in blood cells of samples both from chronic phase and blast crisis patients. Since these samples had no TP53 mutations, we believe that wild type TP53 accumulates in blood cells of CML patients. Our results, therefore, indicate that molecular changes in coding regions of the TP53 gene are rare. The significance of the abundance of intronic changes should be investigated further. Accumulation of wild type TP53 in CML cells may indicate an additional mechanism involving this gene in the pathogenesis of this disease. Genes Chromosomes Cancer 21:2–7, 1998.

Antiphospholipid antibodies may be a new prognostic parameter in aggressive non‐Hodgkin's lymphoma

Abstract:  Objectives: Patients with malignancies have an increased prevalence of antiphospholipid antibodies (APA). The aim of this study was to determine the prevalence of IgG, IgM, and IgA anticardiolipin antibodies (aCL) and anti‐beta‐2 glycoprotein I antibodies (anti‐β2‐GPI) in patients with non‐Hodgkins lymphoma (NHL), and to investigate their clinical and prognostic significance. Methods: The study group included 86 patients with NHL. Enzyme‐linked immunosorbent assay kits were used to measure the concentrations of aCL and anti‐β2‐GPI, and coagulation tests, to measure lupus anticoagulant (LAC) activity. Blood was collected at diagnosis in all patients and at follow‐up in 15. Median follow‐up time was 1.9 yr. Results: Elevated APA levels were found in 35 patients (41%) at diagnosis: one patient aCL IgG, five patients aCL IgM, five aCL IgA, one anti‐β2‐GPI IgG, 14 anti‐β2‐GPI IgM, and 19 anti‐β2‐GPI IgA; LAC activity was found in three of 67 patients (4.5%). There was no significant correlation between elevated APA levels and patients age or sex, disease stage or grade, bone marrow involvement, B symptoms, serum lactate dehydrogenase levels, serum β2 microglobulin levels, International Prognostic Index (IPI) score, performance status, type of treatment, or response to treatment. There was a correlation between elevated APA and absence of extranodal disease (P = 0.045). A strong negative correlation was found between elevated APA at diagnosis and survival time. Two‐year survival was 90 ± 5% for patients without APA at diagnosis compared with 63 ± 11% for patients with an elevated APA levels (P = 0.0025). APA added to the predictive value of IPI for event‐free and overall survival. Conclusions: APA are elevated in 41% of NHL patients at diagnosis and are correlated with shortened survival. Their level may serve as an independent prognostic variable in aggressive NHL.

Burkitt's lymphoma presenting as acute leukemia (Burkitt's lymphoma cell leukemia). Report of two cases in Israel

Two rare cases of Burkitts lymphoma presenting as acute leukemia are described. Both patients had typical features of Burkitts lymphoma with rapidly growing, extranodal tumor masses which were multifocal. The blasts infiltrating the bone marrow and peripheral blood showed cytologic, cytochemical, immunologic, and ultrastructural features of Burkitts tumor cells. The cells had B‐cell markers but lacked the EBV‐DNA genome and had multiple microvilli as seen by means of scanning electron microscopy. In both cases, the disease was resistant to chemotherapy and rapidly fatal, despite the fact that complete remissions of short duration were obtained.

Establishment of a human T-acute lymphoblastic leukemia cell line with a (16;20) chromosome translocation☆

A new T-cell line, Loucy, was established from the peripheral blood of a patient with T-cell acute lymphoblastic leukemia (T-ALL). The surface marker analysis of the cell line is OKT3+, OKT4+, THB4+, J5 +/-, OKT6-, TdT-, and HLA-DR-, indicating stage IV in T-cell lineage. Karyotype analysis revealed 45,X,5q-,t(16;20)(p12;q13). The translocation between chromosomes 16 and 20 has not been previously detected in ALL. This cell line may be of value in evaluating the role of t(16;20) in the etiology of T-ALL.

Pooled analysis of p53 mutations in hematological malignancies

A computerized database is described that contains information about 507 mutations in the p53 gene of hematologic tumors and corresponding cell lines. Analysis of these mutations indicated the following findings: First, mutational spectrum analysis in these tumors was found to be similar to the pattern found for other solid tumors. However, when the patterns of base substitutions were examined separately according to the types of hematologic malignancies, followed by subgroup analysis, notable differences (in some cases of statistical significance) emerged. Second, mutational pattern analysis indicates that about 48% of base substitutions in hematologic tumors are suspected to be associated with carcinogen exposure. Third, deletions and insertions are localized mainly to exons 5–8 and repeated DNA sequences. However, the unusual profile of variations in frequency within each type of tumor suggests that, in addition to endogenous damage to template DNA, there is the factor of exposure to environmental physical and chemical carcinogens/mutagens. Fourth, p53 protein alterations analysis indicate that most of the changes in the amino acids are “semiconservative,” presumably in order to avoid disrupting the structure of the p53 monomer. Consistent with this notion, structural mutations are more conservative than the binding mutations.

Significance of BCR-ABL Transcripts in Bone Marrow Aspirates of Philadelphia-Negative Essential Thrombocythemia Patients

Philadelphia-negative (Ph-neg) essential thrombocythemia (ET), polycythemia vera (PV) and idiopathic myelofibrosis (IMF) form a syndrome of related chronic myeloproliferative disorders (MPD) characterized by expansion of one or more of the hematopoietic progenitors. Based on our previous finding of BCR-ABL transcripts in bone marrow aspirates of 12/25 Ph-neg ET patients, we have expanded our study up to 40 patients. Here we describe the rational for performing this study and report 19 of 40 patients who have BCR-ABL transcripts in their BM, 11 of them carry b3a2 and 8 carry b2a2. The two groups, BCR-ABL positive and negative, were completely identical with regard to clinical characteristics and laboratory data. We also report preliminary results of our attempt to examine concordance or discordance of BCR-ABL expression in the peripheral blood and bone marrow of Ph-neg ET patients.

Hemophagocytosis Simulating Malignant Histiocytosis: A Terminal Event of the Myelodysplastic Syndrome

We describe a patient with hemophagocytic syndrome resembling malignant histiocytosis which was complicating myelodysplastic disease of 3 years duration. Detailed morphological and ultrastructural studies indicate that the histiocytic component did not demonstrate features of malignancy. A review of other known malignancies ending up in the hemophagocytic syndrome is given, and the significance of this syndrome is discussed.