Molecular cloning, genomic structure and interactions of the putative breast tumor suppressor TACC2

TACC3: a multi-functional protein promoting cancer cell survival and aggressiveness

TACC3 is the most oncogenic member of the transforming acidic coiled-coil domain-containing protein (TACC) family. It is one of the major recruitment factors of distinct multi-protein complexes. TACC3 is localized to spindles, centrosomes, and nucleus, and regulates key oncogenic processes, including cell proliferation, migration, invasion, and stemness. Recently, TACC3 inhibition has been identified as a vulnerability in highly aggressive cancers, such as cancers with centrosome amplification (CA). TACC3 has spatiotemporal functions throughout the cell cycle; therefore, targeting TACC3 causes cell death in mitosis and interphase in cancer cells with CA. In the clinics, TACC3 is highly expressed and associated with worse survival in multiple cancers. Furthermore, TACC3 is a part of one of the most common fusions of FGFR, FGFR3-TACC3 and is important for the oncogenicity of the fusion. A detailed understanding of the regulation of TACC3 expression, its key partners, and molecular functions in cancer cells is vital for uncovering the most vulnerable tumors and maximizing the therapeutic potential of targeting this highly oncogenic protein. In this review, we summarize the established and emerging interactors and spatiotemporal functions of TACC3 in cancer cells, discuss the potential of TACC3 as a biomarker in cancer, and therapeutic potential of its inhibition.

Unveiling the role of GAS41 in cancer progression

GAS41, a member of the human YEATS domain family, plays a pivotal role in human cancer development. It serves as a highly promising epigenetic reader, facilitating precise regulation of cell growth and development by recognizing essential histone modifications, including histone acetylation, benzoylation, succinylation, and crotonylation. Functional readouts of these histone modifications often coincide with cancer progression. In addition, GAS41 functions as a novel oncogene, participating in numerous signaling pathways. Here, we summarize the epigenetic functions of GAS41 and its role in the carcinoma progression. Moving forward, elucidating the downstream target oncogenes regulated by GAS41 and the developing small molecule inhibitors based on the distinctive YEATS recognition properties will be pivotal in advancing this research field.

Mechanistic insights into genomic structure and functions of a novel oncogene YEATS4

As a novel oncogene, the role of YEATS domain-containing protein 4 (YEATS4) in the occurrence, development, and treatment of tumors is now beginning to be appreciated. YEATS4 plays an important role in regulating DNA repair during replication. The upregulation of YEAST4 promotes DNA damage repair and prevents cell death, whereas its downregulation inhibits DNA replication and induces apoptosis. Additionally, accumulating evidence indicates that the aberrant activation of YEATS4 leads to changes in drug resistance, epithelial-mesenchymal transition and also in the migration and invasion capacity of tumor cells. Therefore, specific inhibition of the expression or activity of YEATS4 protein may be an effective strategy for inhibiting the proliferation, motility, differentiation, and/or survival of tumor cells. Taken together, YEATS4 has emerged as a potential target for multiple cancers and is an attractive protein for the development of small-molecule inhibitors. However, research on YEAST4 in tumor-related fields is limited and its biological functions, metabolism, and the regulatory mechanism of YEATS4 in numerous cancers remain undetermined. This review comprehensively and extensively summarizes the functions, structure and oncogenic roles of YEATS4 in cancer progression and aims to further contribute to the study of its underlying molecular mechanism and targeted drugs.

Nanopore sequencing reveals TACC2 locus complexity and diversity of isoforms transcribed from an intronic promoter

Gene expression is controlled at the transcriptional and post-transcriptional levels. The TACC2 gene was known to be associated with tumors but the control of its expression is unclear. We have reported that activity of the intronic promoter p10 of TACC2 in primary lesion of endometrial cancer is indicative of lymph node metastasis among a low-risk patient group. Here, we analyze the intronic promoter derived isoforms in JHUEM-1 endometrial cancer cells, and primary tissues of endometrial cancers and normal endometrium. Full-length cDNA amplicons are produced by long-range PCR and subjected to nanopore sequencing followed by computational error correction. We identify 16 stable, 4 variable, and 9 rare exons including 3 novel exons validated independently. All variable and rare exons reside N-terminally of the TACC domain and contribute to isoform variety. We found 240 isoforms as high-confidence, supported by more than 20 reads. The large number of isoforms produced from one minor promoter indicates the post-transcriptional complexity coupled with transcription at the TACC2 locus in cancer and normal cells.

Characterization of DSM-IV Opioid Dependence Among Individuals of European Ancestry

OBJECTIVE

The opioid epidemic in the United States has led to unprecedented increases in morbidity and mortality, posing a serious public health crisis. Although twin and family studies, as well as genome-wide association studies (GWAS), all identify significant genetic factors contributing to opioid dependence, no studies to date have estimated marker-based heritability estimates of opioid dependence. The goal of the current study was to use a large, genetically imputed, case/control sample of 4,064 participants (after quality control and imputation) with genome-wide data to estimate the unbiased heritability tagged by single nucleotide polymorphisms (SNPs).

METHOD

Study data were part of the Genome-wide Study of Heroin Dependence obtained via the Database for Genotypes and Phenotypes (dbGaP). Genomic-Relatedness-Matrix Restricted Maximum Likelihood with adjustment for minor allele frequency (MAF) and linkage disequilibrium (LD; GREML-LDMS) was used to determine the variation in opioid dependence attributable to common SNPs from imputed data. Mixed linear models were used in an exploratory GWAS to assess effects of single SNPs.

RESULTS

At least 45% of the variance in opioid dependence according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, was attributable to common SNPs, after stratifying to account for differences in MAF and LD across the genome. Most of the genetic variance was tagged by SNPs in the 1%-9% MAF range and in low LD with other SNPs in the region. Two markers in LOC101927293 survived multiple-testing correction (i.e., q value < .05).

CONCLUSIONS

Nearly half of the variation in opioid dependence can be attributed to common SNPs. Most of this variation is due to rare variants in low LD with other markers in the region.

Cigarette smoke exposure enhances transforming acidic coiled-coil-containing protein 2 turnover and thereby promotes emphysema

Our integrative genomic and functional analysis identified transforming acidic coiled-coil-containing protein 2 (TACC2) as a chronic obstructive pulmonary disease (COPD) candidate gene. Here, we found that smokers with COPD exhibit a marked decrease in lung TACC2 protein levels relative to smokers without COPD. Single cell RNA sequencing reveals that TACC2 is expressed primarily in lung epithelial cells in normal human lungs. Furthermore, suppression of TACC2 expression impairs the efficiency of homologous recombination repair and augments spontaneous and cigarette smoke extract-induced (CSE-induced) DNA damage and cytotoxicity in immortalized human bronchial epithelial cells. By contrast, enforced expression of TACC2 attenuates the CSE effects. We also found that CSE enhances TACC2 degradation via the ubiquitin-proteasome system mediated by the ubiquitin E3 ligase subunit, F box L7. Furthermore, cellularly expressed TACC2 proteins harboring naturally occurring mutations exhibited altered protein lifespan coupled with modified DNA damage repair and cytotoxic responses. CS triggers emphysematous changes accompanied by accumulated DNA damage, apoptosis of alveolar epithelia, and lung inflammation in Tacc2-/- compared with Tacc2+/+ mice. Our results suggest that CS destabilizes TACC2 protein in lung epithelia by the ubiquitin proteasome system, leading to subsequent DNA damage, cytotoxicity, and emphysema.

Pretreatment TACC3 expression in locally advanced rectal cancer decreases the response to neoadjuvant chemoradiotherapy

Chemoradiotherapy combined with surgical resection is the standard treatment for locally advanced rectal cancer, but not all the patients respond to neoadjuvant treatment. Transforming acidic coiled-coil protein-3 (TACC3) is frequently aberrantly expressed in rectal cancer tissue. In this study, we investigated whether TACC3 could serve as a biomarker predictive of the efficacy of chemoradiotherapy. In all, 152 rectal cancer patients with tumor tissue collected at biopsy and set aside before treatment were enrolled in this study. All patients received chemoradiotherapy and surgical resection. Immunohistochemically detected tumoral TACC3 expression significantly decreased sensitivity to chemoradiotherapy [risk ratio (RR) = 2.236, 95% confidence interval (CI): 1.447-3.456; P = 0.001] and thus the pathological complete response rate (P = 0.001). TACC3 knockdown using specific siRNA enhanced radiotherapy-induced decreases in proliferation and colony formation by HCT116 and SW480 cells and increased the incidence of radiotherapy-induced apoptosis. Cox multivariate analysis showed that TACC3 was a significant prognostic factor for overall survival (P = 0.017) and disease-free survival (P = 0.020). These findings suggest TACC3 expression may be predictive of chemoradiotherapy sensitivity and prognosis in locally advanced rectal cancer.

Using metabolite profiling to construct and validate a metabolite risk score for predicting future weight gain

Background

Excess weight gain throughout adulthood can lead to adverse clinical outcomes and are influenced by complex factors that are difficult to measure in free-living individuals. Metabolite profiling offers an opportunity to systematically discover new predictors for weight gain that are relatively easy to measure compared to traditional approaches.

Methods and results

Using baseline metabolite profiling data of middle-aged individuals from the Framingham Heart Study (FHS; n = 1,508), we identified 42 metabolites associated (p < 0.05) with longitudinal change in body mass index (BMI). We performed stepwise linear regression to select 8 of these metabolites to build a metabolite risk score (MRS) for predicting future weight gain. We replicated the MRS using data from the Mexico City Diabetes Study (MCDS; n = 768), in which one standard deviation increase in the MRS corresponded to ~0.03 increase in BMI (kg/m²) per year (i.e. ~0.09 kg/year for a 1.7 m adult). We observed that none of the available anthropometric, lifestyle, and glycemic variables fully account for the MRS prediction of weight gain. Surprisingly, we found the MRS to be strongly correlated with baseline insulin sensitivity in both cohorts and to be negatively predictive of T2D in MCDS. Genome-wide association study of the MRS identified 2 genome-wide (p < 5 × 10⁻⁸) and 5 suggestively (p < 1 × 10⁻⁶) significant loci, several of which have been previously linked to obesity-related phenotypes.

Conclusions

We have constructed and validated a generalizable MRS for future weight gain that is an independent predictor distinct from several other known risk factors. The MRS captures a composite biological picture of weight gain, perhaps hinting at the anabolic effects of preserved insulin sensitivity. Future investigation is required to assess the relationships between MRS-predicted weight gain and other obesity-related diseases.

Promoter-level transcriptome in primary lesions of endometrial cancer identified biomarkers associated with lymph node metastasis

For endometrial cancer patients, lymphadenectomy is recommended to exclude rarely metastasized cancer cells. This procedure is performed even in patients with low risk of recurrence despite the risk of complications such as lymphedema. A method to accurately identify cases with no lymph node metastases (LN-) before lymphadenectomy is therefore highly required. We approached this clinical problem by examining primary lesions of endometrial cancers with CAGE (Cap Analysis Gene Expression), which quantifies promoter-level expression across the genome. Fourteen profiles delineated distinct transcriptional networks between LN + and LN- cases, within those classified as having the low or intermediate risk of recurrence. Subsequent quantitative reverse transcription polymerase chain reaction (qRT-PCR) analyses of 115 primary tumors showed SEMA3D mRNA and TACC2 isoforms expressed through a novel promoter as promising biomarkers with high accuracy (area under the receiver operating characteristic curve, 0.929) when used in combination. Our high-resolution transcriptome provided evidence of distinct molecular profiles underlying LN + /LN- status in endometrial cancers, raising the possibility of preoperative diagnosis to reduce unnecessary operations in patients with minimum recurrence risk.

Xenopus TACC2 is a microtubule plus end-tracking protein that can promote microtubule polymerization during embryonic development

Xenopus TACC2 is a microtubule plus end–tracking protein that localizes in front of EB1 and overlaps with TACC1 and TACC3 in cultured embryonic mesenchymal cells and neuronal growth cones. TACC2 OE can promote increased microtubule polymerization in mesenchymal cells but not growth cones, suggesting cell-type specificity to its function.

Microtubule dynamics is regulated by plus end–tracking proteins (+TIPs), which localize to the plus ends of microtubules (MTs). We previously showed that TACC1 and TACC3, members of the transforming acidic coiled-coil protein family, can act as +TIPs to regulate MT dynamics in Xenopus laevis. Here we characterize TACC2 as a +TIP that localizes to MT plus ends in front of EB1 and overlapping with TACC1 and TACC3 in multiple embryonic cell types. We also show that TACC2 can promote MT polymerization in mesenchymal cells but not neuronal growth cones, thus displaying cell-type specificity. Structure–function analysis demonstrates that the C-terminal region of TACC2 is both necessary and sufficient to localize to MT plus ends and promote increased rates of MT polymerization, whereas the N-terminal region cannot bind to MT plus ends but can act in a dominant-negative capacity to reduce polymerization rates. Finally, we analyze mRNA expression patterns in Xenopus embryos for each TACC protein and observe neural enrichment of TACC3 expression compared with TACC1 and TACC2, which are also expressed in mesodermal tissues, including somites. Overall these data provide a novel assessment of all three TACC proteins as a family of +TIPs by highlighting the unique attributes of each, as well as their collective characteristics.

TACC2 (transforming acidic coiled-coil protein 2) in breast carcinoma as a potent prognostic predictor associated with cell proliferation

Transforming acidic coiled‐coil protein 2 (TACC2) belongs to TACC family proteins and involved in a variety of cellular processes through interactions with some molecules involved in centrosomes/microtubules dynamics. Mounting evidence suggests that TACCs is implicated in the progression of some human malignancies, but significance of TACC2 protein in breast carcinoma is still unknown. Therefore, in this study, we examined the clinical significance of TACC2 in breast carcinoma and biological functions by immunohistochemistry and in vitro experiments. Immunohistochemistry for TACC2 was performed in 154 cases of invasive ductal carcinoma. MCF‐7 and MDA‐MB‐453 breast carcinoma cell lines were transfected with small interfering RNA (siRNA) for TACC2, and subsequently, cell proliferation, 5‐Bromo‐2′‐deoxyuridine (BrdU), and invasion assays were performed. TACC2 immunoreactivity was detected in 78 out of 154 (51%) breast carcinoma tissues, and it was significantly associated with Ki‐67 LI. The immunohistochemical TACC2 status was significantly associated with increased incidence of recurrence and breast cancer‐specific death of the patients, and multivariate analyses demonstrated TACC2 status as an independent prognostic factor for both disease‐free and breast cancer‐specific survival. Subsequent in vitro experiments showed that TACC2 significantly increased the proliferation activity of MCF‐7 and MDA‐MB‐453. These results suggest that TACC2 plays an important role in the cell proliferation of breast carcinoma and therefore immunohistochemical TACC2 status is a candidate of worse prognostic factor in breast cancer cases.

Genetic variation in mitotic regulatory pathway genes is associated with breast tumor grade

Mitotic index is an important component of histologic grade and has an etiologic role in breast tumorigenesis. Several small candidate gene studies have reported associations between variation in mitotic genes and breast cancer risk. We measured associations between 2156 single nucleotide polymorphisms (SNPs) from 194 mitotic genes and breast cancer risk, overall and by histologic grade, in the Breast Cancer Association Consortium (BCAC) iCOGS study (n = 39 067 cases; n = 42 106 controls). SNPs in TACC2 [rs17550038: odds ratio (OR) = 1.24, 95% confidence interval (CI) 1.16-1.33, P = 4.2 × 10(-10)) and EIF3H (rs799890: OR = 1.07, 95% CI 1.04-1.11, P = 8.7 × 10(-6)) were significantly associated with risk of low-grade breast cancer. The TACC2 signal was retained (rs17550038: OR = 1.15, 95% CI 1.07-1.23, P = 7.9 × 10(-5)) after adjustment for breast cancer risk SNPs in the nearby FGFR2 gene, suggesting that TACC2 is a novel, independent genome-wide significant genetic risk locus for low-grade breast cancer. While no SNPs were individually associated with high-grade disease, a pathway-level gene set analysis showed that variation across the 194 mitotic genes was associated with high-grade breast cancer risk (P = 2.1 × 10(-3)). These observations will provide insight into the contribution of mitotic defects to histological grade and the etiology of breast cancer.

Glucocorticoid-induced reversal of interleukin-1β-stimulated inflammatory gene expression in human oviductal cells

Studies indicate that high-grade serous ovarian carcinoma (HGSOC), the most common epithelial ovarian carcinoma histotype, originates from the fallopian tube epithelium (FTE). Risk factors for this cancer include reproductive parameters associated with lifetime ovulatory events. Ovulation is an acute inflammatory process during which the FTE is exposed to follicular fluid containing both pro- and anti-inflammatory molecules, such as interleukin-1 (IL1), tumor necrosis factor (TNF), and cortisol. Repeated exposure to inflammatory cytokines may contribute to transforming events in the FTE, with glucocorticoids exerting a protective effect. The global response of FTE cells to inflammatory cytokines or glucocorticoids has not been investigated. To examine the response of FTE cells and the ability of glucocorticoids to oppose this response, an immortalized human FTE cell line, OE-E6/E7, was treated with IL1β, dexamethasone (DEX), IL1β and DEX, or vehicle and genome-wide gene expression profiling was performed. IL1β altered the expression of 47 genes of which 17 were reversed by DEX. DEX treatment alone altered the expression of 590 genes, whereas combined DEX and IL1β treatment altered the expression of 784 genes. Network and pathway enrichment analysis indicated that many genes altered by DEX are involved in cytokine, chemokine, and cell cycle signaling, including NFκΒ target genes and interacting proteins. Quantitative real time RT-PCR studies validated the gene array data for IL8, IL23A, PI3 and TACC2 in OE-E6/E7 cells. Consistent with the array data, Western blot analysis showed increased levels of PTGS2 protein induced by IL1β that was blocked by DEX. A parallel experiment using primary cultured human FTE cells indicated similar effects on PTGS2, IL8, IL23A, PI3 and TACC2 transcripts. These findings support the hypothesis that pro-inflammatory signaling is induced in FTE cells by inflammatory mediators and raises the possibility that dysregulation of glucocorticoid signaling could contribute to increased risk for HGSOC.

TACC3 deregulates the DNA damage response and confers sensitivity to radiation and PARP inhibition

Deregulation of the transforming acidic coiled-coil protein 3 (TACC3), an important factor in the centrosome-microtubule system, has been linked to a variety of human cancer types. We have recently reported on the oncogenic potential of TACC3; however, the molecular mechanisms by which TACC3 mediates oncogenic function remain to be elucidated. In this study, we show that high levels of TACC3 lead to the accumulation of DNA double-strand breaks (DSBs) and disrupt the normal cellular response to DNA damage, at least in part, by negatively regulating the expression of ataxia telangiectasia mutated (ATM) and the subsequent DNA damage response (DDR) signaling cascade. Cells expressing high levels of TACC3 display defective checkpoints and DSB-mediated homologous recombination (HR) and non-homologous end joining (NHEJ) repair systems, leading to genomic instability. Importantly, high levels of TACC3 confer cellular sensitization to radiation and poly(ADP-ribose) polymerase (PARP) inhibition. Overall, our findings provide critical information regarding the mechanisms by which TACC3 contributes to genomic instability, potentially leading to cancer development, and suggest a novel prognostic, diagnostic and therapeutic strategy for the treatment of cancer types expressing high levels of TACC3.

Chromosome 10, frequently lost in human melanoma, encodes multiple tumor-suppressive functions

Although many DNA aberrations in melanoma have been well characterized, including focal amplification and deletions of oncogenes and tumor suppressors, broad regions of chromosomal gain and loss are less well understood. One possibility is that these broad events are a consequence of collateral damage from targeting single loci. Another possibility is that the loss of large regions permits the simultaneous repression of multiple tumor suppressors by broadly decreasing the resident gene dosage and expression. Here, we test this hypothesis in a targeted fashion using RNA interference to suppress multiple candidate residents in broad regions of loss. We find that loss of chromosome regions 6q, 10, and 11q21-ter is correlated with broadly decreased expression of most resident genes and that multiple resident genes impacted by broad regional loss of chromosome 10 are tumor suppressors capable of affecting tumor growth and/or invasion. We also provide additional functional support for Ablim1 as a novel tumor suppressor. Our results support the hypothesis that multiple cancer genes are targeted by regional chromosome copy number aberrations.

TACC3 is essential for EGF-mediated EMT in cervical cancer

The third member of transforming acidic coiled-coil protein (TACC) family, TACC3, has been shown to be an important player in the regulation of centrosome/microtubule dynamics during mitosis and found to be deregulated in a variety of human malignancies. Our previous studies have suggested that TACC3 may be involved in cervical cancer progression and chemoresistance, and its overexpression can induce epithelial-mesenchymal transition (EMT) by activating the phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated protein kinases (ERKs) signal transduction pathways. However, the upstream mechanisms of TACC3-mediated EMT and its functional/clinical importance in human cervical cancer remain elusive. Epidermal growth factor (EGF) has been shown to be a potent inducer of EMT in cervical cancer and associated with tumor invasion and metastasis. In this study, we found that TACC3 is overexpressed in cervical cancer and can be induced upon EGF stimulation. The induction of TACC3 by EGF is dependent on the tyrosine kinase activity of the EGF receptor (EGFR). Intriguingly, depletion of TACC3 abolishes EGF-mediated EMT, suggesting that TACC3 is required for EGF/EGFR-driven EMT process. Moreover, Snail, a key player in EGF-mediated EMT, is found to be correlated with the expression of TACC3 in cervical cancer. Collectively, our study highlights a novel function for TACC3 in EGF-mediated EMT process and suggests that targeting of TACC3 may be an attractive strategy to treat cervical cancers driven by EGF/EGFR signaling pathways.

Transforming acidic coiled-coil proteins (TACCs) in human cancer

Fine-tuned regulation of the centrosome/microtubule dynamics during mitosis is essential for faithful cell division. Thus, it is not surprising that deregulations in this dynamic network can contribute to genomic instability and tumorigenesis. Indeed, centrosome loss or amplification, spindle multipolarity and aneuploidy are often found in a majority of human malignancies, suggesting that defects in centrosome and associated microtubules may be directly or indirectly linked to cancer. Therefore, future research to identify and characterize genes required for the normal centrosome function and microtubule dynamics may help us gain insight into the complexity of cancer, and further provide new avenues for prognostic, diagnostics and therapeutic interventions. Members of the transforming acidic coiled-coil proteins (TACCs) family are emerging as important players of centrosome and microtubule-associated functions. Growing evidence indicates that TACCs are involved in the progression of certain solid tumors. Here, we will discuss our current understanding of the biological function of TACCs, their relevance to human cancer and possible implications for cancer management.

TACC3 promotes epithelial-mesenchymal transition (EMT) through the activation of PI3K/Akt and ERK signaling pathways

Transforming acidic coiled-coil protein 3 (TACC3) is a member of the TACC family, essential for mitotic spindle dynamics and centrosome integrity during mitosis. Mounting evidence suggests that deregulation of TACC3 is associated with various types of human cancer. However, the molecular mechanisms by which TACC3 contributes to the development of cancer remain largely unknown. Here, we propose a novel mechanism by which TACC3 regulates epithelial-mesenchymal transition (EMT). By modulating the expression of TACC3, we found that overexpression of TACC3 leads to changes in cell morphology, proliferation, transforming capability, migratory/invasive behavior as well as the expression of EMT-related markers. Moreover, phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated protein kinases (ERKs) signaling pathways are critical for TACC3-mediated EMT process. Notably, depletion of TACC3 is sufficient to suppress EMT phenotype. Collectively, our findings identify TACC3 as a driver of tumorigenesis as well as an inducer of oncogenic EMT and highlight its overexpression as a potential therapeutic target for preventing EMT-associated tumor progression and invasion.

TACC2 is an androgen-responsive cell cycle regulator promoting androgen-mediated and castration-resistant growth of prostate cancer

Despite the existence of effective antiandrogen therapy for prostate cancer, the disease often progresses to castration-resistant states. Elucidation of the molecular mechanisms underlying the resistance for androgen deprivation in terms of the androgen receptor (AR)-regulated pathways is a requisite to manage castration-resistant prostate cancer (CRPC). Using a ChIP-cloning strategy, we identified functional AR binding sites (ARBS) in the genome of prostate cancer cells. We discovered that a centrosome- and microtubule-interacting gene, transforming acidic coiled-coil protein 2 (TACC2), is a novel androgen-regulated gene. We identified a functional AR-binding site (ARBS) including two canonical androgen response elements in the vicinity of TACC2 gene, in which activated hallmarks of histone modification were observed. Androgen-dependent TACC2 induction is regulated by AR, as confirmed by AR knockdown or its pharmacological inhibitor bicalutamide. Using long-term androgen-deprived cells as cellular models of CRPC, we demonstrated that TACC2 is highly expressed and contributes to hormone-refractory proliferation, as small interfering RNA-mediated knockdown of TACC2 reduced cell growth and cell cycle progression. By contrast, in TACC2-overexpressing cells, an acceleration of the cell cycle was observed. In vivo tumor formation study of prostate cancer in castrated immunocompromised mice revealed that TACC2 is a tumor-promoting factor. Notably, the clinical significance of TACC2 was demonstrated by a correlation between high TACC2 expression and poor survival rates. Taken together with the critical roles of TACC2 in the cell cycle and the biology of prostate cancer, we infer that the molecule is a potential therapeutic target in CRPC as well as hormone-sensitive prostate cancer.

The transforming acidic coiled coil (TACC1) protein modulates the transcriptional activity of the nuclear receptors TR and RAR

Background

The transcriptional activity of Nuclear hormone Receptors (NRs) is regulated by interaction with coactivator or corepressor proteins. Many of these cofactors have been shown to have a misregulated expression or to show a subcellular mislocalization in cancer cell lines or primary tumors. Therefore they can be factors involved in the process of oncogenesis.

Results

We describe a novel NR coregulator, TACC1, which belongs to the Transforming Acidic Coiled Coil (TACC) family. The interaction of TACC1 with Thyroid Hormone Receptors (TR) and several other NRs has been shown in a yeast two-hybrid screen and confirmed by GST pulldown, colocalization and co-immunoprecipitation experiments. TACC1 interacts preferentially with unliganded NRs. In F9 cells, endogenous TACC1 localized in the chromatin-enriched fraction of the nucleus and interacted with Retinoid Acid Receptors (RARα) in the nucleus. TACC1 depletion in the cell led to decreased RARα and TRα ligand-dependent transcriptional activity and to delocalization of TR from the nucleus to the cytoplasm.

Conclusions

From these experimental studies we propose that TACC1 might be a scaffold protein building up a transcriptional complex around the NRs we studied. This function of TACC1 might account for its involvement in several forms of tumour development.

GHTD-amide: a naturally occurring beta cell-derived peptide with hypoglycemic activity

In the early 1970s, a peptide fraction with insulin potentiating activity was purified from human urine but the identity and origins of the active constituent remained unknown. Here we identify the active component and characterize its origins. The active peptide was identified as an alpha amidated tetrapeptide with the sequence GHTD-amide. The peptide was synthesized and tested for stimulation of glycogen synthesis and insulin potentiation by insulin tolerance testing in insulin-deficient rats, which confirmed GHTD-amide as the active peptide. Tissue localization using a peptide-specific anti-serum and epifluorescent and confocal microscopy showed decoration of pancreatic islets but not other tissues. Confocal microscopy revealed co-localization with insulin and immunogold and electron microscopy showed localization to dense core secretory granules. Consistent with these observations GHTD-amide was found in media conditioned by MIN6 islet beta cells. Sequence database searching found no annotated protein in the human proteome encoding a potential precursor for GHTD-amide. We conclude that the insulin potentiating activity originally described in human urine is attributable to the tetrapeptide GHTD-amide. GHTD-amide is a novel peptide produced by pancreatic beta cells and no precursor protein is present in the annotated human proteome. Stimulation of glycogen synthesis and co-localization with insulin in beta cells suggest that GHTD-amide may play a role in glucose homeostasis by enhancing insulin action and glucose storage in tissues.

The TACC proteins: TACC-ling microtubule dynamics and centrosome function

A major quest in cell biology is to understand the molecular mechanisms underlying the high plasticity of the microtubule network at different stages of the cell cycle, and during and after differentiation. Initial reports described the centrosomal localization of proteins possessing transforming acidic coiled-coil (TACC) domains. This discovery prompted several groups to examine the role of TACC proteins during cell division, leading to indications that they are important players in this complex process in different organisms. Here, we review the current understanding of the role of TACC proteins in the regulation of microtubule dynamics, and we highlight the complexity of centrosome function.

Temporal and spatial expression of TACC1 in the mouse and human

TACC1 is the founding member of the evolutionarily conserved transforming acidic coiled coil genes. These genes play a role in normal development and tumorigenesis through interactions with multiple complexes involved in transcription, translation, and centrosomal dynamics. Despite its importance, detailed examination of the expression of TACC1 and splice variants has not previously been performed. In this study, the spatiotemporal distribution of the Tacc1 protein was examined immunohistochemically in cross-sections of mouse embryonic tissues. We also report the distribution of currently known/predicted TACC1 splice variants in adult humans. These results indicate that Tacc1 is regulated in a dynamic manner during embryogenesis. In adult humans, ubiquitous expression of at least one TACC1 splice variant is noted, although specific combinations of variants are evident in individual differentiated tissues. An important observation is that in the in vivo three-dimensional tissue architecture of the growing organism, both the human and mouse TACC1 protein can be localized to different subcellular compartments in a cell- and tissue-specific manner. This indicates that exploration of TACC1 function must take into account the temporal expression of specific splice variants that may perform different cell-type and tissue-specific functions. Furthermore, this analysis will provide the groundwork from which future Tacc1 knockout strategies can be designed and properly interpreted.

Transforming acidic coiled-coil 3 and Aurora-A interact in human thyrocytes and their expression is deregulated in thyroid cancer tissues

Aurora-A kinase has recently been shown to be deregulated in thyroid cancer cells and tissues. Among the Aurora-A substrates identified, transforming acidic coiled-coil (TACC3), a member of the TACC family, plays an important role in cell cycle progression and alterations of its expression occur in different cancer tissues. In this study, we demonstrated the expression of the TACC3 gene in normal human thyroid cells (HTU5), and its modulation at both mRNA and protein levels during cell cycle. Its expression was found, with respect to HTU5 cells, unchanged in cells derived from a benign thyroid follicular tumor (HTU42), and significantly reduced in cell lines derived from follicular (FTC-133), papillary (B-CPAP), and anaplastic thyroid carcinomas (CAL-62 and 8305C). Moreover, in 16 differentiated thyroid cancer tissues, TACC3 mRNA levels were found, with respect to normal matched tissues, reduced by twofold in 56% of cases and increased by twofold in 44% of cases. In the same tissues, a correlation between the expression of the TACC3 and Aurora-A mRNAs was observed. TACC3 and Aurora-A interact in vivo in thyroid cells and both proteins localized onto the mitotic structure of thyroid cells. Finally, TACC3 localization on spindle microtubule was no more observed following the inhibition of Aurora kinase activity by VX-680. We propose that Aurora-A and TACC3 interaction is important to control the mitotic spindle organization required for proper chromosome segregation.

Interaction of TACC proteins with the FHL family: implications for ERK signaling

The Transforming acidic coiled coil (TACC) proteins play a conserved role in normal development and tumorigenesis through interactions with multiple complexes involved in transcription, translation, and centrosomal dynamics. However, despite significant work on the function of TACC3 in the control of centrosomal mechanics, relatively little functional data is known about the family's founding member, TACC1. From a continued analysis of clones isolated by an unbiased yeast two-hybrid assay, we now show direct physical interactions between the TACC1 and the FHL (Four and a Half LIM-only) family of proteins. The authenticity of these interactions was validated both in vitro and in cellular systems. The FHLs exhibit diverse biological roles such as the regulation of the actin cytoskeleton and are promiscuous coregulators for several transcription factors. The interaction of the endogenous TACC-FHL proteins is primarily localized to the nucleus. However, similar to FHL2, overexpression of TACC1A in HEK293 is able to sequester serum activated ERK to the cytoplasm. This has the effect of reducing the serum induced transcriptional response of the c-fos and c-jun genes. The observation that TACCs can interact with the FHLs and alter their serum induced activities raises the possibility that the TACCs participate in crosstalk between cell signaling pathways important for cancer development and tumor progression. The transforming acidic coiled coil genes are known to be important prognostic indicators for breast, ovarian and lung cancer. In this manuscript, we identify a novel interaction between the TACCs and the FHL protein family. This interaction has an affect on ERK and may in part explain the variable associations and changes in subcellular locations of each family with specific subtypes of malignancy.

Inter-genomic cross talk between mitochondria and the nucleus plays an important role in tumorigenesis

Mitochondrial dysfunction is a hallmark of cancer cells. Consistent with this phenotype mutations in mitochondrial genome have been reported in all cancers examined to date. However, it is not clear whether mitochondrial genomic status in human cells affects nuclear genome stability and whether proteins involved in inter-genomic cross talk are involved in tumorigenesis. Using cell culture model and cybrid cell technology, we provide evidence that mitochondrial genetic status impacts nuclear genome stability in human cells. In particular our studies demonstrate 1) that depletion of mitochondrial genome (rho0) leads to chromosomal instability (CIN) reported to be present in variety of human tumors and 2) rho0 cells show transformed phenotype. Our study also demonstrates that mitochondrial genetic status plays a key role in regulation of a multifunctional protein APE1 (also known as Ref1 or HAP1) involved in transcription and DNA repair in the nucleus and the mitochondria. Interestingly we found that altered expression of APE1 in rho0 cells and tumorigenic phenotype can be reversed by exogenous transfer of wild type mitochondria in rho0 cells. Furthermore, we demonstrate that APE1 expression is altered in variety of primary tumors. Taken together, these studies suggest that inter-genomic cross talk between mitochondria and the nucleus plays an important role in tumorigenesis and that APE1 mediates this process.

Aberrations of TACC1 and TACC3 are associated with ovarian cancer

BACKGROUND

Dysregulation 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.

METHODS

Detection 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.

RESULTS

This 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.

CONCLUSION

When 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.

The centrosomal, putative tumor suppressor protein TACC2 is dispensable for normal development, and deficiency does not lead to cancer

TACC2 is a member of the transforming acidic coiled-coil-containing protein family and is associated with the centrosome-spindle apparatus during cell cycling. In vivo, the TACC2 gene is expressed in various splice forms predominantly in postmitotic tissues, including heart, muscle, kidney, and brain. Studies of human breast cancer samples and cell lines suggest a putative role of TACC2 as a tumor suppressor protein. To analyze the physiological role of TACC2, we generated mice lacking TACC2. TACC2-deficient mice are viable, develop normally, are fertile, and lack phenotypic changes compared to wild-type mice. Furthermore, TACC2 deficiency does not lead to an increased incidence of tumor development. Finally, in TACC2-deficient embryonic fibroblasts, proliferation and cell cycle progression as well as centrosome numbers are comparable to those in wild-type cells. Therefore, TACC2 is not required, nonredundantly, for mouse development and normal cell proliferation and is not a tumor suppressor protein.

Structure-function evolution of the transforming acidic coiled coil genes revealed by analysis of phylogenetically diverse organisms

Background

Examination of ancient gene families can provide an insight into how the evolution of gene structure can relate to function. Functional homologs of the evolutionarily conserved transforming acidic coiled coil (TACC) gene family are present in organisms from yeast to man. However, correlations between functional interactions and the evolution of these proteins have yet to be determined.

Results

We have performed an extensive database analysis to determine the genomic and cDNA sequences of the TACCs from phylogenetically diverse organisms. This analysis has determined the phylogenetic relationship of the TACC proteins to other coiled coil proteins, the resolution of the placement of the rabbit TACC4 as the orthologue of human TACC3, and RHAMM as a distinct family of coiled coil proteins. We have also extended the analysis of the TACCs to the interaction databases of C. elegans and D. melanogaster to identify potentially novel TACC interactions. The validity of this modeling was confirmed independently by the demonstration of direct binding of human TACC2 to the nuclear hormone receptor RXRβ.

Conclusion

The data so far suggest that the ancestral TACC protein played a role in centrosomal/mitotic spindle dynamics. TACC proteins were then recruited to complexes involved in protein translation, RNA processing and transcription by interactions with specific bridging proteins. However, during evolution, the TACC proteins have now acquired the ability to directly interact with components of these complexes (such as the LSm proteins, nuclear hormone receptors, GAS41, and transcription factors). This suggests that the function of the TACC proteins may have evolved from performing assembly or coordination functions in the centrosome to include a more intimate role in the functional evolution of chromatin remodeling, transcriptional and posttranscriptional complexes in the cell.

The transforming acidic coiled coil proteins interact with nuclear histone acetyltransferases

Dysregulation of the human transforming acidic coiled coil (TACC) genes is thought to be important in the development of multiple myeloma, breast and gastric cancer. However, even though these proteins have been implicated in the control of cell growth and differentiation, the mechanism by which they function still remains to be clarified. Using the yeast two-hybrid assay, we have now identified the histone acetyltransferase (HAT) hGCN5L2 as a TACC2-binding protein. GST pull-down analysis subsequently confirmed that all human TACC family members can bind in vitro to hGCN5L2. The authenticity of these interactions was validated by coimmunoprecipitation assays within the human embryonic kidney cell line HEK293, which identified the TACC2s isoform as a component consistently bound to several different members of HAT family. This raises the possibility that aberrant expression of one or more TACC proteins may affect gene regulation through their interaction with components of chromatin remodeling complexes, thus contributing to tumorigenesis.

TACC1-chTOG-Aurora A protein complex in breast cancer

The three human TACC (transforming acidic coiled-coil) genes encode a family of proteins with poorly defined functions that are suspected to play a role in oncogenesis. A Xenopus TACC homolog called Maskin is involved in translational control, while Drosophila D-TACC interacts with the microtubule-associated protein MSPS (Mini SPindleS) to ensure proper dynamics of spindle pole microtubules during cell division. We have delineated here the interactions of TACC1 with four proteins, namely the microtubule-associated chTOG (colonic and hepatic tumor-overexpressed gene) protein (ortholog of Drosophila MSPS), the adaptor protein TRAP (tudor repeat associator with PCTAIRE2), the mitotic serine/threonine kinase Aurora A and the mRNA regulator LSM7 (Like-Sm protein 7). To measure the relevance of the TACC1-associated complex in human cancer we have examined the expression of the three TACC, chTOG and Aurora A in breast cancer using immunohistochemistry on tissue microarrays. We show that expressions of TACC1, TACC2, TACC3 and Aurora A are significantly correlated and downregulated in a subset of breast tumors. Using siRNAs, we further show that depletion of chTOG and, to a lesser extent of TACC1, perturbates cell division. We propose that TACC proteins, which we also named 'Taxins', control mRNA translation and cell division in conjunction with microtubule organization and in association with chTOG and Aurora A, and that these complexes and cell processes may be affected during mammary gland oncogenesis.