AGREGATION DES CELLULES EMBRYONNAIRES CHEZ DROSOPHILA MELANOGASTER

International audienc

A Drosophila RNA helicase gene, pitchoune, is required for cell growth and proliferation and is a potential target of d-Myc.

This article describes the characterization of a new Drosophila gene that we have called pitchoune (pit) (meaning small in Provence) because mutations in this gene produce larvae that cannot grow beyond the first instar larval stage although they can live as long as 7-10 days. All the tissues are equally affected and the perfectly shaped larvae are indistinguishable from first instar wild-type animals. Analysis of mutant somatic clones suggests a function in cell growth and proliferation, which is supported by the fact that cell proliferation is promoted by pit overexpression. Tagged-Pit, when transfected in S2 cells, localizes mainly to the nucleolus, pointing towards a possible role in ribosome biogenesis and, consequently, in protein biosynthesis. pit encodes a DEAD-box RNA helicase, a family of proteins involved in the control of RNA structure in many cellular processes and its closest homologue is a human DEAD-box RNA helicase, MrDb, whose corresponding gene transcription is directly activated by Myc-Max heterodimers (Grandori, C., Mac, J., Siëbelt, F., Ayer, D. E. and Eisenman, R. N. (1996) EMBO J. 15, 4344-4357). The patterns of expression of d-myc and pit are superimposable. Ectopic expression of myc in the nervous system drives an ectopic expression of pit in this tissue indicating that in Drosophila as well, pit is a potential target of d-Myc. These results suggest that myc might promote cell proliferation by activating genes that are required in protein biosynthesis, thus linking cell growth and cell proliferation

Sequential Induction Chemotherapy With Vincristine, Daunorubicin, Cyclophosphamide, and Prednisone in Adult Acute Lymphoblastic-leukemia

Sequential chemotherapy with vincristine, daunorubicin, cyclophosphamide, and prednisone doses was administered to 57 adult patients with acute lymphoblastic leukemia (ALL). Complete remission (CR) was achieved in 51 (89%, 95% confidence intervals, [CI] 78-96%). Among patients achieving CR, 62% were in CR after one sequence of chemotherapy, 23% after two sequences, and 5% after three sequences. Six patients (11%) had resistant disease. All patients experienced profound myelosuppression. Median time to recovery of neutrophils >0.5 x 10(9)/l was 22 days (range: 5-89 days), and of platelets >100 x 10(9)/l 21 days (range: 0-45 days). Nonhematologic WHO grade 3 or more side effects consisted predominantly of hyperbilirubinemia (7%), mucositis (5%), nausea and vomiting (2%), and cutaneous toxicity (1%). Severe infectious complications occurred in only 14% of cases. One patient (2%, 95% CI 0-9%) died of therapy-related toxicity while in early CR. We concluded that sequential use of prednisone seemed at least as effective as continuous administration at the expense of a few adverse side effects