Refined mapping of the region of loss of heterozygosity on the long arm of chromosome 7 in human breast cancer defines the location of a second tumor suppressor gene at 7q22 in the region of the CUTL1 gene

Identification and characterization of the mediator kinase-dependent myometrial stem cell phosphoproteome

OBJECTIVE

To identify, in myometrial stem/progenitor cells, the presumptive cell of origin for uterine fibroids, substrates of Mediator-associated cyclin dependent kinase 8/19 (CDK8/19), which is known to be disrupted by uterine fibroid driver mutations in Mediator complex subunit 12 (MED12).

DESIGN

Experimental study.

SETTING

Academic research laboratory.

PATIENT(S)

Women undergoing hysterectomy for uterine fibroids.

INTERVENTION(S)

Stable isotopic labeling of amino acids in cell culture (SILAC) coupled with chemical inhibition of CDK8/19 and downstream quantitative phosphoproteomics and transcriptomic analyses in myometrial stem/progenitor cells.

MAIN OUTCOME MEASURE(S)

High-confidence Mediator kinase substrates identified by SILAC-based quantitative phosphoproteomics were determined using an empirical Bayes analysis and validated orthogonally by in vitro kinase assay featuring reconstituted Mediator kinase modules comprising wild-type or G44D mutant MED12 corresponding to the most frequent uterine fibroid driver mutation in MED12. Mediator kinase-regulated transcripts identified by RNA sequencing were linked to Mediator kinase substrates by computational analyses.

RESULT(S)

A total of 296 unique phosphosites in 166 proteins were significantly decreased (≥ twofold) upon CDK8/19 inhibition, including 118 phosphosites in 71 nuclear proteins representing high-confidence Mediator kinase substrates linked to RNA polymerase II transcription, RNA processing and transport, chromatin modification, cytoskeletal architecture, and DNA replication and repair. Orthogonal validation confirmed a subset of these proteins, including Cut Like Homeobox 1 (CUX1) and Forkhead Box K1 (FOXK1), to be direct targets of MED12-dependent CDK8 phosphorylation in a manner abrogated by the most common uterine fibroid driver mutation (G44D) in MED12, implicating these substrates in disease pathogenesis. Transcriptome-wide profiling of Mediator kinase-inhibited myometrial stem/progenitor cells revealed alterations in cell cycle and myogenic gene expression programs to which Mediator kinase substrates could be linked directly. Among these, CUX1 is an established transcriptional regulator of the cell cycle whose corresponding gene on chromosome 7q is the locus for a recurrent breakpoint in uterine fibroids, linking MED12 and Mediator kinase with CUX1 for the first time in uterine fibroid pathogenesis. FOXK1, a transcriptional regulator of myogenic stem cell fate, was found to be coordinately enriched along with kinase, but not core, Mediator subunits in myometrial stem/progenitor cells compared with differentiated uterine smooth muscle cells.

CONCLUSION(S)

These studies identify a new catalog of pathologically and biologically relevant Mediator kinase substrates implicated in the pathogenesis of MED12 mutation-positive uterine fibroids, and further uncover a biochemical basis to link Mediator kinase activity with CUX1 and FOXK1 in the regulation of myometrial stem/progenitor cell fate.

CUX1, A Controversial Player in Tumor Development

CUX1 belongs to the homeodomain transcription factor family and is evolutionarily and functionally conserved from Drosophila to humans. In addition to the involvement in various physiological events including tissue development, cell proliferation, differentiation and migration, and DNA damage response, CUX1 has been implicated in tumorigenesis. Interestingly, CUX1 has been recently recognized as a haploinsufficient tumor suppressor, which is paradoxically overexpressed in tumor cells. While loss of heterozygosity and/or mutations of CUX1 have been frequently detected in many types of cancers, genomic amplification, and overexpression of CUX1 have also been reported in cancer tissues and are correlated with higher tumor grade and poor prognosis. Therefore, deciphering the roles of different CUX1 isoforms and in different tumor stages is required to establish a CUX1-based therapeutic strategy for cancer treatment.

CUX2 functions as an oncogene in papillary thyroid cancer

BACKGROUND

In recent years, the incidence of thyroid cancer (TC), the most common endocrine malignancy, has been increasing. Emerging evidence indicates that the CUT/CUX/CDP family of proteins can play an important role in tumor development and progression by regulating many cancer-related functions. However, the molecular functions of CUX2 in TC remain unknown.

METHODS

In this study, we used a series of loss-of-function experiments and Western blot analysis to investigate the function of CUX2 in TC and the mechanisms involved.

RESULTS

Our data revealed that CUX2 expression levels were upregulated in papillary thyroid cancer (PTC). Functionally, CUX2 silencing significantly inhibited PTC cell line (KTC-1 and BCPAP) proliferation, colony formation, migration, invasion, and apoptosis. Furthermore, CUX2 induced epithelial-mesenchymal transition (EMT) and influenced the phosphorylation of AKT and mTOR in the PI3K-AKT-mTOR pathways.

CONCLUSION

In summary, CUX2 may function as a tumor promoter in TC.

Estimation of Serum Butyryl Cholinesterase in Patients with Oral Squamous Cell Carcinoma: A Cross-Sectional Study

INTRODUCTION

Oral cancer is a major global threat to public health. It is one of the most common causes of mortality and morbidity in the modern era. Oral Squamous Cell Carcinoma (OSCC) accounts for over 90% of the malignancies involving the oral cavity. The enzyme- Butyryl Cholinesterase (BChE) is proposed to have a role in cell proliferation, cell adhesion, cell differentiation, apoptosis and tumorigenesis. Few studies have been conducted for understanding the significance of serum BChE as a biomarker in oral cancer patients; however literature available is insufficient to arrive at a conclusion. There is a need of a simple, rapid, convenient, inexpensive and reliable biomarker of oral cancer. So, the present study is an attempt to estimate the level of BChE in oral cancer, prior to definitive therapy.

AIM

To estimate and compare the serum BChE levels in patients with OSCC with age and gender matched healthy controls.

MATERIALS AND METHODS

The study comprised of 80 subjects, of which 40 biopsy proven OSCC patients of either sex were selected as cases and 40 healthy, age and gender matched subjects as controls. Estimation of serum BChE levels was done by colorimetric method using RANDOX RX Imola Auto-Analyzer. The statistical analysis between the OSCC group and the control group were done using unpaired t-test. Comparison between serum BChE levels and TNM stages of OSCC were done using Kruskal-Wallis Test. Comparison between serum BChE levels and histopathological grades of OSCC were done using Mann-Whitney U Test.

RESULTS

There was statistically highly significant decrease in the mean serum BChE levels in the OSCC group compared to the control group (p<0.001). It was revealed that the serum BChE levels were further decreased in moderately differentiated squamous cell carcinoma than well differentiated squamous cell carcinoma and the difference was statistically significant (p <0.05).

CONCLUSION

The decrease in the serum BChE level demonstrates that it as a simple, rapid, convenient, inexpensive and reliable biomarker for oral cancer. Our findings support the concept of role of BChE in apoptosis, cell proliferation, differentiation and its related link in the pathophysiology of oral cancer.

Germline large genomic alterations on 7q in patients with multiple primary cancers

Patients with multiple primary cancers (MPCs) are suspected to have a hereditary cancer syndrome. However, only a small proportion may be explained by mutations in high-penetrance genes. We investigate two unrelated MPC patients that met Hereditary Breast and Ovaria Cancer criteria, both presenting triple negative breast tumors and no mutations in BRCA1, BRCA2 and TP53 genes. Germline rearrangements on chromosome 7q, involving over 40 Mb of the same region, were found in both patients: one with mosaic loss (80% of cells) and the other with cnLOH (copy-neutral loss of heterozygosity) secondary to maternal allele duplication. Five children tested had no alterations on 7q. The patients shared 330 genes in common on 7q22.1-q34, including several tumor suppressor genes (TSGs) previously related to breast cancer risk and imprinted genes. The analysis of the triple negative BC from one patient revealed a mosaic gain of 7q translated for over-expressed cancer-related genes. The involvement of TSGs and imprinted genes, mapped on 7q, has the potential of being associated to MPC risk, as well as cancer progression. To our knowledge, this is the first description of patients with MPCs that harbor constitutive large alterations on 7q.

Epidemiological and genetic clues for molecular mechanisms involved in uterine leiomyoma development and growth

BACKGROUND

Uterine leiomyomas (fibroids) are highly prevalent benign smooth muscle tumors of the uterus. In the USA, the lifetime risk for women developing uterine leiomyomas is estimated as up to 75%. Except for hysterectomy, most therapies or treatments often provide only partial or temporary relief and are not successful in every patient. There is a clear racial disparity in the disease; African-American women are estimated to be three times more likely to develop uterine leiomyomas and generally develop more severe symptoms. There is also familial clustering between first-degree relatives and twins, and multiple inherited syndromes in which fibroid development occurs. Leiomyomas have been described as clonal and hormonally regulated, but despite the healthcare burden imposed by the disease, the etiology of uterine leiomyomas remains largely unknown. The mechanisms involved in their growth are also essentially unknown, which has contributed to the slow progress in development of effective treatment options.

METHODS

A comprehensive PubMed search for and critical assessment of articles related to the epidemiological, biological and genetic clues for uterine leiomyoma development was performed. The individual functions of some of the best candidate genes are explained to provide more insight into their biological function and to interconnect and organize genes and pathways in one overarching figure that represents the current state of knowledge about uterine leiomyoma development and growth.

RESULTS

In this review, the widely recognized roles of estrogen and progesterone in uterine leiomyoma pathobiology on the basis of clinical and experimental data are presented. This is followed by fundamental aspects and concepts including the possible cellular origin of uterine fibroids. The central themes in the subsequent parts are cytogenetic aberrations in leiomyomas and the racial/ethnic disparities in uterine fibroid biology. Then, the attributes of various in vitro and in vivo, human syndrome, rodent xenograft, naturally mutant, and genetically modified models used to study possible molecular mechanisms of leiomyoma development and growth are described. Particular emphasis is placed on known links to fibrosis, hypertrophy, and hyperplasia and genes that are potentially important in these processes.

CONCLUSIONS

Menstrual cycle-related injury and repair and coinciding hormonal cycling appears to affect myometrial stem cells that, at a certain stage of fibroid development, often obtain cytogenetic aberrations and mutations of Mediator complex subunit 12 (MED12). Mammalian target of rapamycin (mTOR), a master regulator of proliferation, is activated in many of these tumors, possibly by mechanisms that are similar to some human fibrosis syndromes and/or by mutation of upstream tumor suppressor genes. Animal models of the disease support some of these dysregulated pathways in fibroid etiology or pathogenesis, but none are definitive. All of this suggests that there are likely several key mechanisms involved in the disease that, in addition to increasing the complexity of uterine fibroid pathobiology, offer possible approaches for patient-specific therapies. A final model that incorporates many of these reported mechanisms is presented with a discussion of their implications for leiomyoma clinical practice.

The transcription factor CUTL1 is associated with proliferation and prognosis in malignant melanoma

The transcription factor CUTL1 (CCAAT displacement protein 1) has been reported to participate in the proliferation of diverse types of cancer. In the present study, we investigated the potential involvement of CUTL1 in the proliferation of malignant melanoma. We found that CUTL1 expression was upregulated in malignant melanoma tissues and cell lines, and CUTL1 expression was selected as a prognostic predictor for malignant melanoma patients by both univariate and multivariate analysis. Knockdown of CUTL1 by short hairpin RNA significantly reduced the colony-forming ability of malignant melanoma cells in vitro and reduced tumor growth in vivo, whereas forced overexpression of CUTL1 produced the opposite results. Consistently, cell cycle progression was impaired upon downregulation of CUTL1 and enhanced when CUTL1 was upregulated. Additional experiments suggested that CUTL1 may regulate the proliferation of malignant melanoma by modulating the expression of cell cycle-related proteins.

CUX1, a haploinsufficient tumour suppressor gene overexpressed in advanced cancers

CUT-like homeobox 1 (CUX1) is a homeobox gene that is implicated in both tumour suppression and progression. The accumulated evidence supports a model of haploinsufficiency whereby reduced CUX1 expression promotes tumour development. Paradoxically, increased CUX1 expression is associated with tumour progression, and ectopic CUX1 expression in transgenic mice increases tumour burden in several tissues. One CUX1 isoform functions as an ancillary factor in base excision repair and the other CUX1 isoforms act as transcriptional activators or repressors. Several transcriptional targets and cellular functions of CUX1 affect tumorigenesis; however, we have yet to develop a mechanistic framework to reconcile the opposite roles of CUX1 in cancer protection and progression.

-7/7q- syndrome in myeloid-lineage hematopoietic malignancies: attempts to understand this complex disease entity

The recurrence of chromosomal abnormalities in a specific subtype of cancer strongly suggests that dysregulated gene expression in the corresponding region has a critical role in disease pathogenesis. -7/7q-, defined as the entire loss of chromosome 7 and partial deletion of its long arm, is among the most frequently observed chromosomal aberrations in myeloid-lineage hematopoietic malignancies such as myelodysplastic syndrome and acute myeloid leukemia, particularly in patients treated with cytotoxic agents and/or irradiation. Tremendous efforts have been made to clarify the molecular mechanisms underlying the disease development, and several possible candidate genes have been cloned. However, the study is still underway, and the entire nature of this syndrome is not completely understood. In this review, we focus on the attempts to identify commonly deleted regions in patients with -7/7q-; isolate the candidate genes responsible for disease development, cooperative genes and the factors affecting disease prognosis; and determine effective and potent therapeutic approaches. We also refer to the possibility that the accumulation of multiple gene haploinsufficiency, rather than the loss of a single tumor suppressor gene, may contribute to the development of diseases with large chromosomal deletions such as -7/7q-.

RAS transformation requires CUX1-dependent repair of oxidative DNA damage

The base excision repair (BER) that repairs oxidative damage is upregulated as an adaptive response in maintaining tumorigenesis of RAS-transformed cancer cells.

The Cut homeobox 1 (CUX1) gene is a target of loss-of-heterozygosity in many cancers, yet elevated CUX1 expression is frequently observed and is associated with shorter disease-free survival. The dual role of CUX1 in cancer is illustrated by the fact that most cell lines with CUX1 LOH display amplification of the remaining allele, suggesting that decreased CUX1 expression facilitates tumor development while increased CUX1 expression is needed in tumorigenic cells. Indeed, CUX1 was found in a genome-wide RNAi screen to identify synthetic lethal interactions with oncogenic RAS. Here we show that CUX1 functions in base excision repair as an ancillary factor for the 8-oxoG-DNA glycosylase, OGG1. Single cell gel electrophoresis (comet assay) reveals that Cux1^+/− MEFs are haploinsufficient for the repair of oxidative DNA damage, whereas elevated CUX1 levels accelerate DNA repair. In vitro base excision repair assays with purified components demonstrate that CUX1 directly stimulates OGG1's enzymatic activity. Elevated reactive oxygen species (ROS) levels in cells with sustained RAS pathway activation can cause cellular senescence. We show that elevated expression of either CUX1 or OGG1 prevents RAS-induced senescence in primary cells, and that CUX1 knockdown is synthetic lethal with oncogenic RAS in human cancer cells. Elevated CUX1 expression in a transgenic mouse model enables the emergence of mammary tumors with spontaneous activating Kras mutations. We confirmed cooperation between Kras^G12V and CUX1 in a lung tumor model. Cancer cells can overcome the antiproliferative effects of excessive DNA damage by inactivating a DNA damage response pathway such as ATM or p53 signaling. Our findings reveal an alternate mechanism to allow sustained proliferation in RAS-transformed cells through increased DNA base excision repair capability. The heightened dependency of RAS-transformed cells on base excision repair may provide a therapeutic window that could be exploited with drugs that specifically target this pathway.

In the context of tumor development and progression, mutations are believed to accumulate owing to compromised DNA repair. Such mutations promote oncogenic growth. Yet cancer cells also need to sustain a certain level of DNA repair in order to replicate their DNA and successfully proliferate. Here we show that cancer cells that harbor an activated RAS oncogene exhibit heightened DNA repair capability, specifically in the base excision repair (BER) pathway that repairs oxidative DNA damage. RAS oncogenes alone do not transform primary cells but rather cause their senescence—that is, they stop dividing. As such, cellular senescence in this context is proposed to function as a tumor-suppressive mechanism. We show that CUX1, a protein that accelerates oxidative DNA damage repair, prevents cells from senescing and enables proliferation in the presence of a RAS oncogene. Consistent with this, RAS-induced senescence is also prevented by ectopic expression of OGG1, the DNA glycosylase that removes 8-oxoguanine, the most abundant oxidized base. Strikingly, CUX1 expression in transgenic mice enables the emergence of tumors with spontaneous activating Kras mutations. Conversely, knockdown of CUX1 is synthetic lethal for RAS-transformed cells, thereby revealing a potential Achilles' heel of these cancer cells. Overall, the work provides insight into understanding the role of DNA repair in cancer progression, showing that while DNA damage-induced mutations promote tumorigenesis, sustained RAS-dependent tumorigenesis requires suppression of DNA damage. The heightened dependency of RAS-transformed cells on base excision repair may provide a therapeutic window that could be exploited with drugs that specifically target this pathway.

Cutl1: a potential target for cancer therapy

CDP, a key transcription regulator encoded by Cutl1 gene, has been demonstrated to be involved in repressing or promoting expression of target genes through its specific DNA-binding, meanwhile, the activity of CDP was influenced by some types of modifications including transcriptional, posttranscriptional, translational and posttranslational modifications. In this review, we systematically analyzed the role of CDP in normal development and tumor progression, and then emphasized its interactors and downstream molecules. Eventually, we concluded that Cut1 could promote cancer progression and its down-regulating expression will be a promising strategy for cancer therapy.

Molecular characterization of the region 7q22.1 in splenic marginal zone lymphomas

Splenic marginal zone lymphomas (SMZL) are an uncommon type of B-cell non-Hodgkin's lymphoma (NHL-B) in which no specific chromosomal translocations have been described. In contrast, the most frequent cytogenetic abnormality is the loss of the long arm of chromosome 7 (7q). Previous reports have located this loss in the 7q32 region. In order to better characterize the genomic imbalances in SMZL, molecular studies were carried out in 73 patients with SMZL. To gain insight into the mapping at 7q a tiling array was also used. The results confirmed the loss of 7q as the most frequent change. In addition, several abnormalities, including 4q22.1, 1q21.3–q22, 6q25.3, 20q13.33, 3q28, 2q23.3–q24.1 and 17p13, were also present. A loss of 7q22.1 at 99925039–101348479 bp was observed in half of the cases. The region of 7q22.1 has not previously been characterised in SMZL. Our results confirmed the presence of a new region of loss on chromosome 7 in these NHL.

Interactions of acetylcholinesterase with caveolin-1 and subsequently with cytochrome c are required for apoptosome formation

Acetylcholinesterase (AChE) is emerging as an important component in leading to apoptosis. Our previous study demonstrated that silencing of the AChE gene blocked the interaction between cytochrome c and apoptotic protease-activating factor-1 (Apaf-1) in etoposide-induced apoptosis of HT-29 cells. We undertook this study to further dissect the molecular role of AChE in apoptosome formation. The present study elicited that small interfering RNA (siRNA) to cytochrome c gene blocked the interaction of AChE with Apaf-1, whereas siRNA to Apaf-1 gene did not block the interaction of AChE with cytochrome c, indicating that the interaction of AChE with cytochrome c is required for the interaction between cytochrome c and protease-activating factor-1. We further observed that AChE is localized to caveolae via interacting with caveolin-1 during apoptosis and that the disruption of caveolae prevented apoptosome formation. These data indicate that the interactions of AChE with caveolin-1 and subsequently with cytochrome c appear to be indispensable for apoptosome formation.

The multiple roles of CUX1: insights from mouse models and cell-based assays

Cux (Cut homeobox) genes are present in all metazoans. Early reports described many phenotypes caused by cut mutations in Drosophila melanogaster. In vertebrates, CUX1 was originally characterized as the CCAAT-displacement protein (CDP). Another line of investigation revealed the presence of CUX1 within a multi-protein complex called the histone nuclear factor D (HiNF-D). Recent studies led to the identification of several CUX1 isoforms with distinct DNA binding and transcriptional properties. While the CCAAT-displacement activity was implicated in the transcriptional repression of several genes, some CUX1 isoforms were found to participate in the transcriptional activation of some genes. The expression and activity of CUX1 was shown to be regulated through the cell cycle and to be a target of TGF-beta signaling. Mechanisms of regulation include alternative transcription initiation, proteolytic processing, phosphorylation and acetylation. Cell-based assays have established a role for CUX1 in the control of cell cycle progression, cell motility and invasion. In the mouse, gene inactivation as well as over-expression in transgenic mice has revealed phenotypes in multiple organs and cell types. While some phenotypes could be explained by the presumed functions of CUX1 in the affected cells, other phenotypes invoked non-cell-autonomous effects that suggest regulatory functions with an impact on cell-cell interactions. The implication of CUX1 in cancer was suggested first from its over-expression in primary tumors and cancer cell lines and was later confirmed in mouse models.

Expression of a tumor-related gene network increases in the mammalian hypothalamus at the time of female puberty

Much has been learned in recent years about the central mechanisms controlling the initiation of mammalian puberty. It is now clear that this process requires the interactive participation of several genes. Using a combination of high throughput, molecular, and bioinformatics strategies, in combination with a system biology approach, we singled out from the hypothalamus of nonhuman primates and rats a group of related genes whose expression increases at the time of female puberty. Although these genes [henceforth termed tumor-related genes (TRGs)] have diverse cellular functions, they share the common feature of having been earlier identified as involved in tumor suppression/tumor formation. A prominent member of this group is KiSS1, a gene recently shown to be essential for the occurrence of puberty. Cis-regulatory analysis revealed the presence of a hierarchically arranged gene set containing five major hubs (CDP/CUTL1, MAF, p53, YY1, and USF2) controlling the network at the transcriptional level. In turn, these hubs are heavily connected to non-TRGs involved in the transcriptional regulation of the pubertal process. TRGs may be expressed in the mammalian hypothalamus as components of a regulatory gene network that facilitates and integrates cellular and cell-cell communication programs required for the acquisition of female reproductive competence.

Structural aberrations of chromosome 7 revealed by a combination of molecular cytogenetic techniques in myeloid malignancies

In bone marrow cells of 33 patients with myelodysplastic syndrome and acute myeloid leukemia, structural rearrangements of chromosome 7 were found with conventional G-banding: 8 with deletions 7q and 25 with translocations. In 29 of the patients, complex karyotypes were confirmed using multicolor fluorescence in situ hybridization (mFISH). Commercial probes (Abbot Molecular) were used for 7q22, 7q31, and 7q35, the regions most frequently deleted in myeloid malignancies. In three cases without deletions, high-resolution multicolor banding (mBAND) for chromosome 7 revealed other aberrations. Five groups of chromosomal rearrangements were established: (a) deletion 7q as a sole aberration (2 cases), (b) deletion 7q and complex karyotypes (6 cases), (c) combined translocations and deletions of 7q (17 cases), (d) combined translocation and deletion 7p (5 cases), and (e) translocation of chromosomes 7 without deletion 7p or 7q (3 cases). Deletions of all three FISH-screened regions were the most frequent, with heterogeneous breakpoints. The region 7p13.2 approximately p15.2 was most commonly deleted. Most of the deletions were cryptic, not detectable with conventional cytogenetics. Aberrations of chromosome 7 are associated with a very poor outcome; survival time in our cohort was short (median 7 months).

CUTL1 is phosphorylated by protein kinase A, modulating its effects on cell proliferation and motility

CUTL1, also known as CDP (CCAAT Displacement Protein), Cut, or Cux-1, is a homeodomain transcription factor known to play an essential role in development and cell cycle progression. Previously, we identified CUTL1 as modulator of cell motility and invasiveness. Here we report that protein kinase A (PKA), known to inhibit tumor progression in various tumor types, directly phosphorylates CUTL1 at serine 1215 in NIH3T3 fibroblasts. The PKA-induced phosphorylation results in decreased DNA binding affinity of CUTL1 and diminished CUTL1-mediated cell cycle progression and cell motility. Furthermore, the expression of several CUTL1 target genes involved in proliferation and migration, such as DNA polymerase A and DKK2, was modulated by PKA-induced phosphorylation. These data identify CUTL1 as a novel target of PKA through which this protein kinase can modulate tumor cell motility and tumor progression.

Homeobox gene expression in cancer: insights from developmental regulation and deregulation

Homeobox genes encode transcription factors that play essential roles in controlling cell growth and differentiation during embryonic development. Many homeobox genes are aberrantly expressed in a wide variety of solid tumours, and their deregulation appears to enhance cell survival and proliferation and to inhibit differentiation. In hematologic malignancies, deregulated homeobox genes profoundly perturb self-renewal and proliferation of hematopoietic stem cells and progenitors. It is increasingly recognised that solid tumours, like hematologic malignancies, could arise from cancer stem cells, and that targeting these cells could be the most effective means of inhibiting tumour progression and disease recurrence. Studying the biological effects and mechanisms of homeobox genes in cancers could provide valuable insights into identifying cancer stem cells and targeting the self-renewal pathways in these cell populations.

CUTL1 is a target of TGF(beta) signaling that enhances cancer cell motility and invasiveness

CUTL1, also known as CDP, Cut, or Cux-1, is a homeodomain transcriptional regulator known to be involved in development and cell cycle progression. Here we report that CUTL1 activity is associated with increased migration and invasiveness in numerous tumor cell lines, both in vitro and in vivo. Furthermore, we identify CUTL1 as a transcriptional target of transforming growth factor beta and a mediator of its promigratory effects. CUTL1 activates a transcriptional program regulating genes involved in cell motility, invasion, and extracellular matrix composition. CUTL1 expression is significantly increased in high-grade carcinomas and is inversely correlated with survival in breast cancer. This suggests that CUTL1 plays a central role in coordinating a gene expression program associated with cell motility and tumor progression.

The homeodomain protein CDP regulates mammary-specific gene transcription and tumorigenesis

The CCAAT-displacement protein (CDP) has been implicated in developmental and cell-type-specific regulation of many cellular and viral genes. We previously have shown that CDP represses mouse mammary tumor virus (MMTV) transcription in tissue culture cells. Since CDP-binding activity for the MMTV long terminal repeat declines during mammary development, we tested whether binding mutations could alter viral expression. Infection of mice with MMTV proviruses containing CDP binding site mutations elevated viral RNA levels in virgin mammary glands and shortened mammary tumor latency. To determine if CDP has direct effects on MMTV transcription rather than viral spread, virgin mammary glands of homozygous CDP-mutant mice lacking one of three Cut repeat DNA-binding domains (DeltaCR1) were examined by reverse transcription-PCR. RNA levels of endogenous MMTV as well as alpha-lactalbumin and whey acidic protein (WAP) were elevated. Heterozygous mice with a different CDP mutation that eliminated the entire C terminus and the homeodomain (DeltaC mice) showed increased levels of MMTV, beta-casein, WAP, and alpha-lactalbumin RNA in virgin mammary glands compared to those from wild-type animals. No differences in amounts of WDNM1, epsilon-casein, or glyceraldehyde-3-phosphate dehydrogenase RNA were observed between the undifferentiated mammary tissues from wild-type and mutant mice, indicating the specificity of this effect. These data show independent contributions of different CDP domains to negative regulation of differentiation-specific genes in the mammary gland.

Acetylcholinesterase plays a pivotal role in apoptosome formation

Although a recent study (Zhang et al. Cell Death Differ 2002; 9; 790-800) presented that acetylcholinesterase (AChE) might be an important common component in leading to various types of apoptosis, the molecular mechanism, by which AChE functions, had remained elusive before that study. We explored the role of AChE in apoptosis by silencing the AChE gene. Silencing of the AChE gene abolished the expression of AChE and prevented caspase-9 activation, decrease of cell viability, nuclear condensation and poly(adenosine diphosphate-ribose) polymerase cleavage but not mitochondrial events. Importantly, silencing of the AChE gene blocked the interaction between apoptotic protease-activating factor-1 and cytochrome c. Here we propose that AChE plays a pivotal role in the formation of apoptosome.

Mutation analysis of CDP, TP53, and KRAS in uterine leiomyomas

Leiomyomas are the most common gynecologic tumors in women, but very little is known about their molecular pathology. We used single-stranded conformational polymorphism/heteroduplex analysis to analyze 42 unselected uterine leiomyomas for somatic mutations in all coding exons of the gene encoding CCAAT displacement protein (CDP), as well as exons 5-8 of TP53 and codons 1-36 and 38-80 of KRAS. No somatic mutations were identified in either TP53 or KRAS, indicating that disregulation of these genes is not required for leiomyomas development. Aberrant band shifts were identified in CDP, but these were all germline nonpathogenic variants that have been reported previously. There is good functional and genetic evidence indicating that CDP is a leiomyoma suppressor, but our data suggested that somatic mutations in this gene were rare in unselected uterine leiomyomas. It is possible that CDP belongs to a class of tumor suppressor in which loss of only one copy of the gene, either by genetic or epigenetic mechanisms, is sufficient to allow tumor growth.

Deletion mapping on the long arm of chromosome 7 in splenic lymphoma with villous lymphocytes

Splenic lymphoma with villous lymphocytes (SLVL) is a low-grade lymphoproliferative disorder characterized by splenomegaly and circulating villous lymphocytes in the peripheral blood. It is considered to be the leukemic form of splenic marginal zone lymphoma (SMZL). The genetic basis of this lymphoma type remains unknown. Conventional cytogenetic studies have identified frequent structural abnormalities of chromosome 7, in the form of translocations, mainly unbalanced, and 7q deletions. In this current study, we undertook deletion mapping of the long arm of chromosome 7 in a series of cases with SLVL. Metaphase fluorescence in situ hybridization (FISH) was used in the first instance, followed by a study of loss of heterozygosity (LOH). The common area of deletion identified by FISH spanned from the YAC clone HSC7E1289 (mapping to 7q32.1) to in between YACs HSC7E195 and HSC7E648 (7q32-3). By application of 50 microsatellite markers mapping to the FISH-CDR and to areas of deletion reported in other studies, four distinct hotspot loci were identified, with abnormalities present in 29-55% cases. In three of them, both LOH and biallelic deletions were found. The LOH in the majority of patients was noncontiguous. The presence of a high incidence of abnormalities in the established hotspot areas and in particular the finding of biallelic deletions is indicative of the existence of genes important for the pathogenesis of SLVL in these areas.

Pre-clinical applications of transgenic mouse mammary cancer models

Breast cancer is a leading cause of cancer morbidity and mortality. Given that the majority of human breast cancers appear to be due to non-genetic factors, identifying agents and mechanisms of prevention is key to lowering the incidence of cancer. Genetically engineered mouse models of mammary cancer have been important in elucidating molecular pathways and signaling events associated with the initiation, promotion, and the progression of cancer. Since several transgenic mammary models of human breast cancer progress through well-defined cancer stages, they are useful pre-clinical systems to test the efficacy of chemopreventive and chemotherapeutic agents. This review outlines several oncogenic pathways through which mammary cancer can be induced in transgenic models and describes several types of preventive and therapeutic agents that have been tested in transgenic models of mammary cancer. The effectiveness of farnesyl inhibitors, aromatase inhibitors, differentiating agents, polyamine inhibitors, anti-angiogenic inhibitors, and immunotherapeutic compounds including vaccines have been evaluated in reducing mammary cancer and tumor progression in transgenic models.

CASP, the alternatively spliced product of the gene encoding the CCAAT-displacement protein transcription factor, is a Golgi membrane protein related to giantin

Large coiled-coil proteins are being found in increasing numbers on the membranes of the Golgi apparatus and have been proposed to function in tethering of transport vesicles and in the organization of the Golgi stack. Members of one class of Golgi coiled-coil protein, comprising giantin and golgin-84, are anchored to the bilayer by a single C-terminal transmembrane domain (TMD). In this article, we report the characterization of another mammalian coiled-coil protein, CASP, that was originally identified as an alternatively spliced product of the CUTL1 gene that encodes CCAAT-displacement protein (CDP), the human homologue of the Drosophila homeodomain protein Cut. We find that the Caenorhabditis elegans homologues of CDP and CASP are also generated from a single gene. CASP lacks the DNA binding motifs of CDP and was previously reported to be a nuclear protein. Herein, we show that it is in fact a Golgi protein with a C-terminal TMD and shares with giantin and golgin-84 a conserved histidine in its TMD. However, unlike these proteins, CASP has a homologue in Saccharomyces cerevisiae, which we call COY1. Deletion of COY1 does not affect viability, but strikingly restores normal growth to cells lacking the Golgi soluble N-ethylmaleimide-sensitive factor attachment protein receptor Gos1p. The conserved histidine is necessary for Coy1p's activity in cells lacking Gos1p, suggesting that the TMD of these transmembrane Golgi coiled-coil proteins is directly involved in their function.

Expression of N-terminally truncated isoforms of CDP/CUX is increased in human uterine leiomyomas

Genetic analyses and mRNA expression studies have implicated CUTL1 as a candidate tumor-suppressor gene in uterine leiomyomas and breast cancers. However, modulation of CDP/Cux, the protein encoded by CUTL1, does not agree with this notion. The activity of CDP/Cux, which is the DNA binding subunit of HiNF-D, was upregulated as normal cells progressed into S phase and constitutively elevated in several tumor cell lines. Activation of CDP/Cux at the G(1)/S transition involved the proteolytic processing of the protein to generate a shorter isoform. Uterine leiomyomas represent a unique reagent for molecular analysis because they are resected as homogeneous tumor tissue together with the adjacent normal myometrium and they are often very large. In the present study, proteins were isolated from 16 pairs of matched tumors and adjacent myometrium and analyzed by Western blot and electrophoretic mobility shift assays. Strikingly, in 11/16 tumors, the steady-state level of small CDP/Cux isoforms was increased compared to normal control tissue. Where tested, a corresponding increase in CDP/Cux stable DNA binding activity was observed. DNA sequencing analysis of CUTL1 cDNAs from 6 leiomyomas, including 4 with LOH of CUTL1, did not reveal any gross rearrangement or point mutations. Altogether these findings suggest that CUTL1 is probably not the tumor suppressor on 7q22. Moreover, the frequent increase in smaller CDP/Cux isoforms indicates that molecular events associated with the truncation of CDP/Cux proteins may be selected in uterine leiomyomas.

Induction of acetylcholinesterase expression during apoptosis in various cell types

Acetylcholinesterase (AChE) plays a key role in terminating neurotransmission at cholinergic synapses. AChE is also found in tissues devoid of cholinergic responses, indicating potential functions beyond neurotransmission. It has been suggested that AChE may participate in development, differentiation, and pathogenic processes such as Alzheimer's disease and tumorigenesis. We examined AChE expression in a number of cell lines upon induction of apoptosis by various stimuli. AChE is induced in all apoptotic cells examined as determined by cytochemical staining, immunological analysis, affinity chromatography purification, and molecular cloning. The AChE protein was found in the cytoplasm at the initiation of apoptosis and then in the nucleus or apoptotic bodies upon commitment to cell death. Sequence analysis revealed that AChE expressed in apoptotic cells is identical to the synapse type AChE. Pharmacological inhibitors of AChE prevented apoptosis. Furthermore, blocking the expression of AChE with antisense inhibited apoptosis. Therefore, our studies demonstrate that AChE is potentially a marker and a regulator of apoptosis.

Transcriptional mechanisms regulating myeloid-specific genes

Myeloid blood cells comprise an important component of the immune system. Proper control of both lineage- and stage-specific gene expression is required for normal myeloid cell development and function. In recent years, a relatively small number of critical transcriptional regulators have been identified that serve important roles both in myeloid cell development and regulation of lineage-restricted gene expression in mature myeloid cells. This review summarizes our current understanding of the regulation of lineage- and stage-restricted transcription during myeloid cell differentiation, how critical transcriptional regulators control myeloid cell development, and how perturbations in transcription factor function results in the development of leukemia.

Lymphoid apoptosis and myeloid hyperplasia in CCAAT displacement protein mutant mice

CCAAT displacement protein (cux/CDP) is an atypical homeodomain protein that represses expression of several developmentally regulated lymphoid and myeloid genes in vitro, including gp91-phox, immunoglobulin heavy chain, the T-cell receptor beta and gamma chains, and CD8. To determine how this activity affects cell development in vivo, a hypomorphic allele of cux/CDP was created by gene targeting. Homozygous mutant mice (cux/CDP(Delta HD/Delta HD)) demonstrated a partial neonatal lethality phenotype. Surviving animals suffered from a wasting disease, which usually resulted in death between 2 and 3 weeks of age. Analysis of T lymphopoiesis demonstrated that cux/CDP(Delta HD/Delta HD) mice had dramatically reduced thymic cellularity due to enhanced apoptosis, with a preferential loss of CD4(+)CD8(+) thymocytes. Ectopic CD25 expression was also observed in maturing thymocytes. B lymphopoiesis was also perturbed, with a 2- to 3-fold reduction in total bone marrow B-lineage cells and a preferential loss of cells in transition from pro-B/pre-BI to pre-BII stages due to enhanced apoptosis. These lymphoid abnormalities were independent of effects related to antigen receptor rearrangement. In contrast to the lymphoid demise, cux/CDP(Delta HD/Delta HD) mice demonstrated myeloid hyperplasia. Bone marrow reconstitution experiments identified that many of the hematopoietic defects were linked to microenvironmental effects, suggesting that underexpression of survival factors or overexpression of death-inducing factors accounted for the phenotypes observed. Tumor necrosis factor (TNF) levels were elevated in several tissues, especially thymus, suggesting that TNF may be a target gene for cux/CDP-mediated repression. These data suggest that cux/CDP regulates normal hematopoiesis, in part, by modulating the levels of survival and/or apoptosis factors expressed by the microenvironment.

Upregulation of the gene encoding a cytoplasmic dynein intermediate chain in senescent human cells

Normal human somatic cells, unlike cancer cells, stop dividing after a limited number of cell divisions through the process termed cellular senescence or replicative senescence, which functions as a tumor-suppressive mechanism and may be related to organismal aging. By means of the cDNA subtractive hybridization, we identified eight genes upregulated during normal chromosome 3-induced cellular senescence in a human renal cell carcinoma cell line. Among them is the DNCI1 gene encoding an intermediate chain 1 of the cytoplasmic dynein, a microtubule motor that plays a role in chromosome movement and organelle transport. The DNCI1 mRNA was also upregulated during in vitro aging of primary human fibroblasts. In contrast, other components of cytoplasmic dynein showed no significant change in mRNA expression during cellular aging. Cell growth arrest by serum starvation, contact inhibition, or gamma-irradiation did not induce the DNCI1 mRNA, suggesting its specific role in cellular senescence. The DNCI1 gene is on the long arm of chromosome 7 where tumor suppressor genes and a senescence-inducing gene for a group of immortal cell lines (complementation group D) are mapped. This is the first report that links a component of molecular motor complex to cellular senescence, providing a new insight into molecular mechanisms of cellular senescence.

Significant correlation between the breakpoints of rare clonal aberrations in benign solid tumors and the assignment of HMGIY retropseudogenes

Recently, we described a mechanism by which a retropseudogene, during evolution, becomes an exon of a pre-existing active gene. Similar mechanisms may account for the activation of processed genes by chromosomal rearrangements in neoplasms. Because genes of the high-mobility group protein family HMGI(Y) are known to be involved in the development of a variety of benign solid tumors, it was the aim of the present study to analyze breakpoints of clonal chromosome abnormalities in that group of benign tumors for a possible correlation with retropseudogenes of the HMGIY gene. Whereas the HMGIYL1 retrospeudogene has recently been mapped to Xp22.1, we assigned a further retropseudogene by FISH to 4q13, and database research allowed us to assign a third retropseudogene to 12q24.1. Sequence analyses of these retropseudogenes revealed high-identity indices to the HMGIY gene and no frame-shift divergences. Breakpoint information was obtained from cytogenetic aberrations in uterine leiomyomas, lipomas, pleomorphic adenomas, and pulmonary chondroid hamartomas because, in all of these tumor entities, cytogenetic subgroups involving genes of the HMGI(Y) family exist. Chromosomal bands harboring HMGIY retropseudogenes were affected with a significantly higher frequency than expected under the assumption of purely randomly occurring breakages. These results support our hypothesis that HMGIY-related retropseudogenes can be affected by chromosomal rearrangements in benign human tumors.

Role of the multifunctional CDP/Cut/Cux homeodomain transcription factor in regulating differentiation, cell growth and development

CDP/Cux/Cut proteins are an evolutionarily conserved family of proteins containing several DNA binding domains: one Cut homeodomain and one, two or three Cut repeats. In Drosophila melanogaster, genetic studies indicated that Cut functions as a determinant of cell-type specification in several tissues, notably in the peripheral nervous system, the wing margin and the Malpighian tubule. Moreover, Cut was found to be a target and an effector of the Notch signaling pathway. In vertebrates, the same functions appear to be fulfilled by two cut-related genes with distinct patterns of expression. Cloning of the cDNA for the CCAAT-displacement protein (CDP) revealed that it was the human homologue of Drosophila Cut. CDP was later found be the DNA binding protein of the previously characterized histone nuclear factor D (HiNF-D). CDP and its mouse counterpart, Cux, were also reported to interact with regulatory elements from a large number of genes, including matrix attachment regions (MARs). CDP/Cut proteins were found generally to function as transcriptional repressors, although a participation in transcriptional activation is suggested by some data. Repression by CDP/Cut involves competition for binding site occupancy and active repression via the recruitment of a histone deacetylase activity. Various combinations of Cut repeats and the Cut homeodomains can generate distinct DNA binding activities. These activities are elevated in proliferating cells and decrease during terminal differentiation. One activity, involving the Cut homeodomain, is upregulated in S phase. CDP/Cut function is regulated by several post-translational modification events including phosphorylation, dephosphorylation, and acetylation. The CUTL1 gene in human was mapped to 7q22, a chromosomal region that is frequently rearranged in various cancers.

Deletion 7p in gastric MALT lymphoma

Deletion of the long arm of chromosome 7 has been related to loss of tumor suppressor genes which may constitute a primary step of carcinogenesis in many kinds of malignancies, including low-grade B-cell lymphoma. However, deletion of the short arm of chromosome 7, del(7p), in low-grade B-cell lymphoma has not been reported. Here, we report a case of gastric MALT lymphoma with the chromosome aberration del(7p) which progressed in spite of eradication of Helicobactor pylori. Deletion 7p may represent a new karyotypic change that is possibly related to autonomous growth of MALT lymphoma.

Exon/intron structure and alternative transcripts of the CUTL1 gene

The human CUTL1 gene (Cut-like 1) is a candidate tumor suppressor gene located on chromosome 7 at band 22, a region that is frequently deleted in several human cancers. The gene spans at least 340kb and contains 33 exons. Synthesis of five different transcripts involves two promoter regions, two polyadenylation sites and seven alternative splicing events. The two polyadenylation sites are located at the ends of exons 24 and 33 and are separated by approximately 40kb. Transcription is initiated in two genomic regions, giving rise to alternate first exons which are spliced to a common exon 2. All transcripts contain exons 2 to 14, but differ in their 3' regions. Exon 14 can be spliced alternatively to the beginning or the middle of exon 15, or to exon 25, generating transcripts with exons 15 to 24 or exons 25 to 33. Moreover, exon 16 can be spliced out from the mature transcripts that contain exons 15 to 24. Overall, five distinct transcripts are generated as a result of alternative transcription initiation, splicing and polyadenylation. We discuss potential mechanisms by which alternate polyadenylation site usage may affect alternative splicing events and vice versa.

Loss of heterozygosity in tumor cells requires re-evaluation: the data are biased by the size-dependent differential sensitivity of allele detection

Normal tissue contamination of tumors may eclipse the detection of loss of heterozygosity (LOH) by microsatellite analysis and may also hamper isolation of tumor suppressor genes. To test the potential impact of this problem, we prepared artificial mixtures of mouse-human microcell hybrid lines that carried different alleles of the same chromosome 3 marker. After performing an allele titration assay, we found a consistent difference between the LOH of a high molecular weight (H) allele and the LOH of a low molecular weight (L) allele of the same CA repeat marker. It follows that normal tissue admixtures will be less of a problem when LOH affects a H allele than with a L allele. Random screening of 100 papers published between 1994 and 1999 revealed that the loss of a L allele was recorded at about half the frequency (52%) of loss of a H allele. To avoid this bias, we have developed rules for the evaluation of LOH data. We suggest that the loss of a L allele should be given more weight than the loss of a H allele in LOH studies using microsatellite markers.