[Oncogenes and leukemia: history and perspectives]

[The IgH 3'RR: Doctor Jekyll and Mister Hyde of B-cell maturation and lymphomagenesis]

The four transcriptional enhancers located in the 3' regulatory region (3'RR) of the IgH locus control the late phases of B-cell maturation, namely IgH locus transcription, somatic hypermutation and class switch recombination. Doctor Jekyll by nature, the 3'RR acts as Mister Hyde in case of oncogenic translocation at the IgH locus taking under its transcriptional control the translocated oncogene. The aim of this review is to show this duality on the basis of the latest scientific advances in the structure and function of the 3'RR and to hIghlight the targeting of the 3'RR as a potential therapeutic approach in mature B-cell lymphomas.

Des oncogènes à l’interface entre transcription et épissage

Oncogene activity ranges from transduction signals to transcription factors. Altered expression of oncogenes, either by chromosomal translocation, proviral insertion or point mutations, can lead to tumor formation. More specifically, data accumulated through the last two decades have shown that disregulation of oncogenic transcription factors can interfere with regulatory cascades that control the growth, differentiation, and survival of normal cells. There is also evidence that alterations of oncogene activity are associated with pre-mRNA splicing defects. The insights gained from the pivotal role of RNA polymerase II in coupling transcription and splicing have instigated a new line of research regarding the possible role of oncogenic transcription factors in pre-mRNA splicing regulation. This review focuses on recent advances addressing this question. Understanding the impact of alterations in the expression and/or function of oncogenes have important prognostic implications that can guide the design of new therapeutic drugs to promote differentiation and/or apoptosis over cell proliferation.

Targets of fibroblast growth factor 1 (FGF-1) and FGF-2 signaling involved in the invasive and tumorigenic behavior of carcinoma cells

Fibroblast growth factor (FGF)-1 and -2 have potent biological activities implicated in malignant tumor development. Their autocrine and nonautocrine activity in tumor progression of carcinoma was investigated in the NBT-II cell system. Cells were manipulated to either produce and be autocrine for FGF-1 or -2 or to only produce but not respond to these factors. The autocrine cells are highly invasive and tumorigenic and the determination of specific targets of FGF/fibroblast growth factor receptor (FGFR) signaling was assessed. In vitro studies showed that nonautocrine cells behave like epithelial parental cells, whereas autocrine cells have a mesenchymal phenotype correlated with the overexpression of urokinase plasminogen activator receptor (uPAR), the internalization of E-cadherin, and the redistribution of beta-catenin from the cell surface to the cytoplasm and nucleus. uPAR was defined as an early target, whereas E-cadherin and the leukocyte common antigen-related protein-tyrosine phosphatase (LAR-PTP) were later targets of FGF signaling, with FGFR1 activation more efficient than FGFR2 at modulating these targets. Behavior of autocrine cells was consistent with a decrease of tumor-suppressive activities of both E-cadherin and LAR-PTP. These molecular analyses show that the potential of these two growth factors in tumor progression is highly dependent on specific FGFR signaling and highlights its importance as a target for antitumor therapy.

[Chromosomal translocations in human malignant hematopoiesis. Structural and functional consequences]

The improvement of molecular biology techniques and human genome mapping and sequencing boosted the molecular analysis of chromosomal abnormalities observed in human hematological malignancies. The characterization of structural abnormalities (translocation, deletion) has proven particularly seminal. A better understanding of the pathology itself and of its generation arose from the identification of the genes involved in the chromosomal translocations of human leukemia. This work summaries some of the present knowledge regarding human leukemogenesis.