We recently showed that the Drosophila transforming acidic coiled-coil (D-TACC) protein is located in the centrosome, interacts with microtubules, and is required for mitosis in the Drosophila embryo. There are three known human TACC proteins that share a conserved, C-terminal, coiled-coil region with D-TACC. These proteins have all been implicated in cancer, but their normal functions are unknown. We show that all three human TACC proteins are concentrated at centrosomes, but with very different characteristics: TACC1 is weakly concentrated at centrosomes during mitosis; TACC2 is strongly concentrated at centrosomes throughout the cell cycle; and TACC3 is strongly concentrated in a more diffuse region around centrosomes during mitosis. When the C-terminal TACC domain is overexpressed in HeLa cells, it forms large polymers in the cytoplasm that can interact with both microtubules and tubulin. The full-length TACC proteins form similar polymers when overexpressed, but their interaction with microtubules and tubulin is regulated during the cell cycle. At least one of the human TACC proteins appears to increase the number and͞or stability of centrosomal microtubules when overexpressed during mitosis. Thus, the TACC domain identifies a family of centrosomal proteins that can interact with microtubules. This may explain the link between the TACC genes and cancer.centrosome ͉ cancer ͉ mitosis B oth centrosomes and the microtubules they organize play crucial roles in many cell processes (1-3). Despite their importance, however, surprisingly little is known about how centrosomes interact with microtubules at the molecular level.Considerable progress has been made recently in understanding how ␥-tubulin ring complexes in the centrosome are involved in microtubule nucleation (4, 5). The interaction between centrosomes and microtubules, however, appears to be more complicated than just a simple nucleation (6-9). To understand better how centrosomes interact with microtubules, we and others have biochemically isolated a number of proteins from Drosophila embryos that interact with microtubules in vitro and concentrate at centrosomes in vivo (10-13). We have previously shown that one of these proteins, Drosophila transforming acidic coiled-coil (D-TACC), is essential for mitotic spindle function in the early Drosophila embryo (14). In embryos where D-TACC function is perturbed, spindle and astral microtubules are abnormally short and weak, and this leads to failures in nuclear migration and chromosome segregation.The C-terminal region of D-TACC is predicted to form a coiled-coil that is similar to that found in the mammalian TACCcontaining proteins. The normal functions of the three known mammalian TACC proteins are unknown, but several observations suggest that the proteins may contribute to cancer: the human TACC genes are all in genomic regions that are rearranged in certain cancer cells; TACC3 is up-regulated in some cancer cell lines; and the overexpression of TACC1 transforms mouse fibroblasts (15, 16). Very recently, ...

Ampli®cation of several chromosomal regions have been observed in human breast carcinomas. One such region, 8p11, is ampli®ed in 10 ± 15% of tumor samples. Although the FGFR1 gene is located close to this region, and is often included within the amplicon, the observation that tumors exhibiting 8p11 ampli®cation do not always overexpress FGFR1 suggests that another gene located close to FGFR1 is involved in the tumorigenic process. We now report the precise location of four expressed sequence tags (ESTs) within this region and the cloning of a novel gene, designated TACC1 (transforming acidic coiled coil gene 1), which encodes an 8 kb transcript and which is expressed at high levels during early embryogenesis. Constitutive expression of this gene under the control of the cytomegalovirus (CMV) promoter in mouse ®broblasts, results in cellular transformation and anchorage independent growth, suggesting that inappropriate expression can impart a proliferative advantage. This observation raises the possibility that ampli®cation of TACC1 could promote malignant growth, thereby making TACC1 an attractive candidate for the gene promoting tumorigenicity as a result of the 8p11 ampli®cation in human breast cancers.

No abstract

No abstract

Human mitochondrial DNA (mtDNA) encodes 13 proteins involved in oxidative phosphorylation (OXPHOS). In order to investigate the role of mitochondrial OXPHOS genes in breast tumorigenesis, we have developed a breast epithelial cell line devoid of mtDNA (ρ 0 cells). Our analysis revealed that depletion of mtDNA in breast epithelial cells results in in vitro tumorigenic phenotype as well as breast tumorigenesis in a xenograft model. We identified two major gene networks which were differentially regulated between parental and ρ 0 epithelial cells. The focal proteins in these networks include (i) FN1 (fibronectin) and (ii) p53. Bioinformatic analyses of FN1 network identified laminin, integrin and 3 of 6 members of peroxiredoxin whose expression were altered in ρ 0 epithelial cells. In the p53 network, we identified SMC4 and WRN whose changes in expression suggest that this network may affect chromosomal stability. Consistent with above finding our study revealed an increase in DNA double strand breaks and unique chromosomal rearrangements in ρ 0 breast epithelial cells. Additionally, we identified tight junction proteins claudin-1 and claudin-7 in p53 network. To determine the functional relevance of altered gene expression, we focused on detailed analyses of claudin-1 and -7 proteins in breast tumorigenesis. Our study determined that (i) claudin-1 and 7 were indeed downregulated in ρ 0 breast epithelial cells, (ii) downregulation of claudin-1 or -7 led to neoplastic transformation of breast epithelial cells, and (iii) claudin-1 and -7 were also downregulated in primary breast tumors. Together, our study suggest that mtDNA encoded OXPHOS genes play a key role in transformation of breast epithelial cells and that multiple pathway involved in mitochondria-to-nucleus retrograde regulation contribute to transformation of breast epithelial cells.

BackgroundDysregulation of the human Transforming Acidic Coiled Coil (TACC) genes is thought to be important in the development and progression of multiple myeloma, breast and gastric cancer. Recent, large-scale genomic analysis and Serial Analysis of Gene Expression data suggest that TACC1 and TACC3 may also be involved in the etiology of ovarian tumors from both familial and sporadic cases. Therefore, the aim of this study was to determine the occurrence of alterations of these TACCs in ovarian cancer.MethodsDetection and scoring of TACC1 and TACC3 expression was performed by immunohistochemical analysis of the T-BO-1 tissue/tumor microarray slide from the Cooperative Human Tissue Network, Tissue Array Research Program (TARP) of the National Cancer Institute, National Institutes of Health, Bethesda, MD, USA. Tumors were categorized as either positive (greater than 10% of cells staining) or negative. Statistical analysis was performed using Fisher's exact test and p < 0.05 (single comparisons), and p < 0.02 (multiple comparisons) were considered to be significant. Transgenomics WAVE high performance liquid chromatography (dHPLC) was used to pre-screen the TACC3 gene in constitutional DNA from ovarian cancer patients and their unaffected relatives from 76 families from the Gilda Radner Familial Ovarian Cancer Registry. All variant patterns were then sequenced.ResultsThis study demonstrated absence of at least one or both TACC proteins in 78.5% (51/65) of ovarian tumors tested, with TACC3 loss observed in 67.7% of tumors. The distribution pattern of expression of the two TACC proteins was different, with TACC3 loss being more common in serous papillary carcinoma compared with clear cell carcinomas, while TACC1 staining was less frequent in endometroid than in serous papillary tumor cores. In addition, we identified two constitutional mutations in the TACC3 gene in patients with ovarian cancer from the Gilda Radner Familial Ovarian Cancer Registry. These patients had previously tested negative for mutations in known ovarian cancer predisposing genes.ConclusionWhen combined, our data suggest that aberrations of TACC genes, and TACC3 in particular, underlie a significant proportion of ovarian cancers. Thus, TACC3 could be a hitherto unknown endogenous factor that contributes to ovarian tumorigenesis.

No abstract

No abstract