Tali Tohami

Overexpression of tetraspanins affects multiple myeloma cell survival and invasive potential

Cellular interactions with microenviron‐mental components are critical in multiple myeloma (MM) and impede effective disease treatment. Mem‐branal‐embedded tetraspanins, associated with metastasis suppression, are underexpressed in MM. We aimed to investigate the consequences of CD81/CD82 tetraspanins over‐expression in MM cell lines. CAG and RPMI 8226 were transfected with pEGFP‐N1/C1 fusion vectors of CD81/CD82. Employing flow cytometry, immunocytochemistry, and activity assays we assessed transfected cells for: morphology, survival, death, caspases, cell cycle, proliferation, oxidative stress, adhesion, motility and invasion. Overexpressed CD81/ CD82 pEGFP‐N1 vectors reduced survival without elevation of pre‐G1 or AnnexinV+/7AAD‐ and independently of caspases. Decreased Ki67 and elevated intracellular glutathione were detected. No perturbations in cell cycle distribution were observed. The pEGFP‐C1 vectors of CD81/CD82 caused reduction of MM cell adherence with/without fibronectin, insulinlike growth factor (IGF)‐I, and matrigel. They also reduced cell motility and attenuated invasion potential’ expressed by reduced secreted MMP‐9 activity. These novel findings delineate the significance of CD81/ CD82 expression to MM cell survival and their negative effects on cell adhesion, motility, and invasion thus, supporting their role as tumor metastasis suppressors.—Tohami T., Drucker L., Shapiro H., Radnay J., and Lishner M. Overexpression of tetraspanins affects multiple myeloma cell survival and invasive potential FASEB J. 21, 691–699 (2007)

Acute Lymphoblastic Leukemia in Early Childhood as the Presenting Sign of Ataxia-Telangiectasia Variant

Ataxia-telangiectasia (A-T), an autosomal recessive disorder is characterized by progressive neurodegeneration, immunodeficiency, sensitivity to ionizing radiation, and predisposition to cancer, especially to lymphoid malignancies. A-T variant is characterized by a milder clinical phenotype and is caused by missense or leaky splice site mutations that produce residual ataxia telangiectasia mutated (ATM) kinase activity. Lymphoid malignancy can precede the diagnosis of A-T, particularly in young children with mild neurological symptoms. We studied a consanguineous family with four A-T variant patients, three of them developed T-ALL at a young age before the diagnosis of A-T was established. ATM mutation analysis detected two new missense mutations both within exon 12: c.1514T>C and c.1547T>C. All four patients are homozygous for the two mutations, while their parents are heterozygous for the mutations. ATM protein level was low in all patients and the response to the radiomimetic agent, neocarzinostatin, was reduced. Leukemic presentation in a young age in three members of consanguineous family led to the identification of a new missense mutation in the ATM gene. The diagnosis of A-T or A-T variant should be considered in children with neurological abnormalities who develop T-ALL at a young age.

Initial exposed phosphatidylserine levels correlate with cellular response to cytotoxic drugs

Abstract: Phosphatidylserines (PS) membranal distribution is associated with an expanding variety of biological processes. We studied the relevance of preliminarily exposed membranal PS levels to cellular effects of cytotoxic agents. PBL of normal controls (n = 18) and patients with doxorubicin‐treated breast carcinoma (n = 27) or 5′‐fluorouracil‐treated colorectal cancer (n = 32) were assayed before and after drug infusion. Membranal expression levels of PS, adhesion molecules (CD18, CD11a–c, CD63) and Fas‐R of leukocyte subtypes were assessed by flow cytometer. Statistical analysis was implemented. Our results demonstrate external expression of PS on all leukocyte subpopulations despite non‐apoptotic light scatter characteristics. Several distinct features were observed of which the more prominent were: leukocyte subtypes each display characteristic PS levels; cancer patients’ PBL display higher preliminary PS levels than normal controls in all cell groups; and existence of negative correlations between initial membranal PS levels and drug‐induced changes in its expression. Our findings underscore the complex involvement of PS in PBL apoptosis and possibly drug resistance.

Hyperphosphatemia during spontaneous tumor lysis syndrome culminate in severe hypophosphatemia at the time of blast crisis of Phneg CML to acute myelomoncytic leukemia.

Extreme swing of phosphor from severe hyperphosphatemia to severe hypophosphatemia in a patient with blast crisis of myeloid origin was the result of imbalance between massive apoptosis of leukemic cells in the context of spontaneous tumor lysis syndrome and massive production of leukemic cells with only 1% of blast in peripheral blood. The mutated p53 protein suggested acting as oncogene in the presented case and possibly affecting phosphor status.