Hypothyroidism Enhances Tumor Invasiveness and Metastasis Development

11 pages, 9 figures.[Background]: Whereas there is increasing evidence that loss of expression and/or function of the thyroid hormone receptors (TRs) could result in a selective advantage for tumor development, the relationship between thyroid hormone levels and human cancer is a controversial issue. It has been reported that hypothyroidism might be a possible risk factor for liver and breast cancer in humans, but a lower incidence of breast carcinoma has been also reported in hypothyroid patients [Methodology/Principal Findings]: In this work we have analyzed the influence of hypothyroidism on tumor progression and metastasis development using xenografts of parental and TRβ1–expressing human hepatocarcinoma (SK-hep1) and breast cancer cells (MDA-MB-468). In agreement with our previous observations tumor invasiveness and metastasis formation was strongly repressed when TRβ–expressing cells were injected into euthyroid nude mice. Whereas tumor growth was retarded when cells were inoculated into hypothyroid hosts, tumors had a more mesenchymal phenotype, were more invasive and metastatic growth was enhanced. Increased aggressiveness and tumor growth retardation was also observed with parental cells that do not express TRs. [Conclusions/Significance]: These results show that changes in the stromal cells secondary to host hypothyroidism can modulate tumor progression and metastatic growth independently of the presence of TRs on the tumor cells. On the other hand, the finding that hypothyroidism can affect differentially tumor growth and invasiveness can contribute to the explanation of the confounding reports on the influence of thyroidal status in human cancer.This work was supported by grants BFU2007-62402 from MEC; RD06/0020/0036 from FIS and from the EU Project CRESCENDO (FP6-018652.Peer reviewe

GLI3 zinc-finger gene interrupted by translocations in Greig syndrome families

No abstract availabl

Leukaemic transformation by CALM–AF10 involves upregulation of Hoxa5 by hDOT1L

Chromosomal translocation is a common cause of leukaemia(1) and the most common chromosome translocations found in leukaemia patients involve the mixed lineage leukaemia (MLL) gene(2,3). AF10 is one of more than 30 MLL fusion partners in leukaemia(4). We have recently demonstrated that the H3K79 methyltransferase hDOT1L contributes to MLL–AF10-mediated leukaemogenesis through its interaction with AF10 (ref. 5). In addition to MLL, AF10 has also been reported to fuse to CALM (clathrin-assembly protein-like lymphoid–myeloid) in patients with T-cell acute lymphoblastic leukaemia (T-ALL) and acute myeloid leukaemia (AML)(6,7). Here, we analysed the molecular mechanism of leukaemogenesis by CALM–AF10. We demonstrate that CALM–AF10 fusion is both necessary and sufficient for leukaemic transformation. Additionally, we provide evidence that hDOT1L has an important role in the transformation process. hDOT1L contributes to CALM–AF10-mediated leukaemic transformation by preventing nuclear export of CALM–AF10 and by upregulating the Hoxa5 gene through H3K79 methylation. Thus, our study establishes CALM–AF10 fusion as a cause of leukaemia and reveals that mistargeting of hDOT1L and upregulation of Hoxa5 through H3K79 methylation is the underlying mechanism behind leukaemia caused by CALM–AF10 fusion