Giandomenico Russo

The TCL1 gene at 14q32.1 is involved in chromosomal translocations and inversions in mature T cell leukemias. These leukemias are classified either as T prolymphocytic leukemias, which occur very late in life, or as T chronic lymphocytic leukemias, which often arise in patients with ataxia telangiectasia (AT) at a young age. In transgenic animals, the deregulated expression of TCL1 leads to mature T cell leukemia, demonstrating the role of TCL1 in the initiation of malignant transformation in T cell neoplasia. Expression of high levels of Tcl1 have also been found in a variety of human tumor-derived B cell lines ranging from pre-B cell to mature B cell. Here we describe the phenotype of transgenic mice, E mu-TCL1, established with TCL1 under the control of a V(H) promoter-Ig(H)-E mu enhancer to target TCL1 expression to immature and mature B cells. Flow cytometric analysis reveals a markedly expanded CD5(+) population in the peritoneal cavity of E mu-TCL1 mice starting at 2 mo of age that becomes evident in the spleen by 3-5 mo and in the bone marrow by 5-8 mo. Analysis of Ig gene rearrangements indicates monoclonality or oligoclonality in these populations, suggesting a preneoplastic expansion of CD5(+) B cell clones, with the elder mice eventually developing a chronic lymphocytic leukemia (CLL)-like disorder resembling human B-CLL. Our findings provide an animal model for CLL, the most common human leukemia, and demonstrate that deregulation of the Tcl1 pathway plays a crucial role in CLL pathogenesis.

The TCL1 oncogene at 14q32.1 is involved in the development of human mature T-cell leukemia. The mechanism of action of Tcl1 is unknown. Because the virus containing the v-akt oncogene causes T-cell lymphoma in mice and Akt is a key player in transduction of antiapoptotic and proliferative signals in T-cells, we investigated whether Akt and Tcl1 function in the same pathway. Coimmunoprecipitation experiments showed that endogenous Akt1 and Tcl1 physically interact in the T-cell leukemia cell line SupT11; both proteins also interact when cotransfected into 293 cells. Using several AKT1 constructs in cotransfection experiments, we determined that this interaction occurs through the pleckstrin homology domain of the Akt1 protein. We further demonstrated that, in 293 cells transfected with TCL1 , the endogenous Akt1 bound to Tcl1 is 5–10 times more active compared with Akt1 not bound to Tcl1. The intracellular localization of Tcl1 and Akt1 in mouse fibroblasts was investigated by immunofluorescence. When transfected alone, Akt1 was found only in cytoplasm whereas Tcl1 was localized in the cytoplasm and in the nucleus. Interestingly, Akt1 was also found in the nucleus when AKT1 was cotransfected with TCL1 , suggesting that Tcl1 promotes the transport of Akt1 to the nucleus. These findings were supported by the intracellular localization of Akt1 or Tcl1 when Tcl1 or Akt1, respectively, were confined to the specific cellular compartments. Thus, we demonstrate that Tcl1 is a cofactor of Akt1 that enhances Akt1 kinase activity and promotes its nuclear transport.

The TCL1 locus on chromosome 14q32.1 is frequently involved in chromosomal translocations and inversions with one of the T-cell receptor loci in human T-cell leukemias and lymphomas. The chromosome 14 region translocated or rearranged involves approximately 350 kb of DNA at chromosome band 14q32.1. Within this region we have identified a gene coding for a 1.3-kb transcript, expressed only in restricted subsets of cells within the lymphoid lineage and expressed at high levels in leukemic cells carrying a t(14;14)(q11;q32) chromosome translocation or a inv(14)(q11;q32) chromosome inversion. The cognate cDNA sequence reveals an open reading frame of 342 nt encoding a protein of 14 kDa. The TCL1 gene sequence, which, to our knowledge, shows no sequence homology with other human genes, is preferentially expressed early in T- and B-lymphocyte differentiation.

Systemic sclerosis (SSc) is a connective tissue disorder characterized by excessive collagen deposition in the skin and internal organs. Several cytokines and chemokines have been implicated in the induction of fibrosis, but a definitive relationship between specific cytokines and organ involvement has not been established yet. Serum samples, PBMC and T cell lines (TCL) obtained from 54 patients affected by SSc and 20 healthy donors (HD) were examined by ELISA for Interferon-gamma (IFN-gamma ), interleukin (IL)-4, IL-6, IL-10, IL-18, Transforming growth factor (TGF)-beta1, Tumour necrosis factor (TNF)-alpha, sCD30, Macrophage derived chemokine (MDC), Monocyte chemoattractant protein (MCP)-1, Macrophage inflammatory protein (MIP)-1alpha and Regulated on activation normal T-cell expressed and secreted (RANTES). In all the SSc serum samples, we found significantly increased levels of IL6, TNFalpha and MCP-1 but reduced amounts of gamma-IFN and MDC. IL6, IL10, IL18, MIP-1alpha and TNFalpha measured in supernatants from PHA-stimulated PBMC and IL6, MCP-1 and RANTES in supernatants from stimulated TCL were also increased in patients. MDC was decreased in all the biological SSc sources studied. TGF-beta1, IL10, and sCD30 were produced at a significantly lower level by SSc TCL. Serum IL6 and sCD30 levels were significantly increased in dc-SSc patients compared to lc-SSc as were levels of MCP-1 produced by PBMC and IL10 from TCL. We observed a strict relationship between pulmonary fibrosis and IL10, MCP-1 (both from TCL) and serum IL6. Kidney involvement was related to serum MCP-1 levels and IL18 production from PBMC. Oesophageal involvement correlated with MDC production from PBMC and IL10 synthesis by TCL. We showed that IL-6, IL-10, MDC and MCP-1 are variably associated with internal organ involvement and allow the discrimination between limited and diffuse forms of the disease.