Nuclear structural proteins as biomarkers of cancer

Urine biomarkers in bladder cancer - current status and future perspectives

Urine markers to detect bladder cancer have been the subject of research for decades. The idea that urine - being in continuous contact with tumour tissue - should provide a vector of tumour information remains an attractive concept. Research on this topic has resulted in a complex landscape of many different urine markers with varying degrees of clinical validation. These markers range from cell-based assays to proteins, transcriptomic markers and genomic signatures, with a clear trend towards multiplex assays. Unfortunately, the number of different urine markers and the efforts in research and development of clinical grade assays are not reflected in the use of these markers in clinical practice, which is currently limited. Numerous prospective trials are in progress with the aim of increasing the quality of evidence about urinary biomarkers in bladder cancer to achieve guideline implementation. The current research landscape suggests a division of testing approaches. Some efforts are directed towards addressing the limitations of current assays to improve the performance of urine markers for a straightforward detection of bladder cancer. Additionally, comprehensive genetic analyses are emerging based on advances in next-generation sequencing and are expected to substantially affect the potential application of urine markers in bladder cancer.

Optical detection of the structural properties of tumor tissue generated by xenografting of drug-sensitive and drug-resistant cancer cells using partial wave spectroscopy (PWS)

A mesoscopic physics-based optical imaging technique, partial wave spectroscopy (PWS), has been used for the detection of cancer by probing nanoscale structural alterations in cells/tissue. The development of drug-resistant cancer cells/tissues during chemotherapy is a major challenge in cancer treatment. In this paper, using a mouse model and PWS, the structural properties of tumor tissue grown in 3D structures by xenografting drug-resistant and drug-sensitive human prostate cancer cells having 2D structures, are studied. The results show that the 3D xenografted tissues maintain a similar hierarchy of the degree of structural disorder properties as that of the 2D original drug-sensitive and drug-resistant cells.

The three-dimensional organization of the genome in cellular senescence and age-associated diseases

Recent advances in genomics and imaging technologies have increased our ability to interrogate the 3D conformation of chromosomes and to better understand principles of organization and dynamics, as well as how their alteration can lead to disease. In this review we describe how these technologies have shed new light into the role of the 3D organization of the genome in defining cellular states in aging and age-associated diseases. We compare the genomic organization in cellular senescence and cancer, discuss the role of the lamina in maintaining the structural and functional integrity of the genome, and we highlight the recent findings on how this organization breaks down in disease states.

Laser-emission imaging of nuclear biomarkers for high-contrast cancer screening and immunodiagnosis

Detection of nuclear biomarkers such as nucleic acids and nuclear proteins is critical for early-stage cancer diagnosis and prognosis. Conventional methods relying on morphological assessment of cell nuclei in histopathology slides may be subjective, whereas colorimetric immunohistochemical and fluorescence-based imaging are limited by strong light absorption, broad-emission bands and low contrast. Here, we describe the development and use of a scanning laser-emission-based microscope that maps lasing emissions from nuclear biomarkers in human tissues. 41 tissue samples from 35 patients labelled with site-specific and biomarker-specific antibody-conjugated dyes were sandwiched in a Fabry-Pérot microcavity while an excitation laser beam built a laser-emission image. We observed multiple sub-cellular lasing emissions from cancer cell nuclei, with a threshold of tens of μJ/mm2, sub-micron resolution (<700 nm), and a lasing band in the few-nanometre range. Different lasing thresholds of nuclei in cancer and normal tissues enabled the identification and multiplexed detection of nuclear proteomic biomarkers, with a high sensitivity for early-stage cancer diagnosis. Laser-emission-based cancer screening and immunodiagnosis might find use in precision medicine and facilitate research in cell biology.

Silencing of ST6Gal I enhances colorectal cancer metastasis by down-regulating KAI1 via exosome-mediated exportation and thereby rescues integrin signaling

Aberrant sialylation has long been correlated with human cancer. Increased ST6 Gal I (β-galactoside α 2, 6 sialyltransferase) and consequently higher levels of cell-surface α 2, 6 sialylation has been associated with human colorectal cancer (CRC) metastasis. We have extensive circumstantial data that sialylation is connected to cancer metastasis, but we do not understand in detail how sialylation can switch on/off multiple steps in cancer metastasis. To investigate the molecular mechanism underlying the ST6Gal I-mediated metastasis of CRC, we silenced the ST6Gal I gene in a metastatic SW620 CRC cell line (SW620-shST6Gal I) and examined the metastatic behavior of the cells. We found that various hallmarks of metastatic ability were considerably enhanced in ST6Gal 1-depleted SW620 clones, as assessed both in vitro and in vivo . In particular, the metastasis suppressor, KAI1, was down-regulated in ST6Gal I-deficient SW620 clones. This reflected the increased exosome-mediated exportation of KAI1, and was associated with a decrease in the KAI1-mediated inhibition of integrin. These findings indicate that gene silencing of ST6Gal I could enhance metastasis of CRC by down-regulating KAI1 activity and rescuing its negative effects on integrin signaling.

The evaluation of diagnostic value of the tumor markers: CCSA-2 and CEA in colorectal cancer

Finding the biomarker or biomarkers with high sensitivity and specificity in colorectal cancer, and thus a high diagnostic value will determine their clinical usefulness in clinical practice. An effective noninvasive blood test would be an ideal method to detect colorectal cancer. Discovered in 2007 a novel tumor marker CCSA-2 showes a promising results in patients with colorectal cancer. THE AIM OF THE STUDY was the evaluation of diagnostic and clinical value of a novel marker - colon cancer specific antigen-2 (CCSA-2) in colorectal adenocarcinoma in comparison to carcinoembryonic antigen (CEA) in patients operated during the years 2008 to 2010 at Wrocław Medical University 1st Department and Clinic of General, Gastroenterological and Endocrinologic Surgery.

MATERIAL AND METHODS

The study was performed on 40 patients with colorectal cancer and 40 patients in control group consisted of healthy subjects who had colonoscopy examinations with negative results (no pathology in the colon was found). The obtained results were statistically analyzed using nonparametric tests - Mann Whitney U and Kruskal-Wallis and Spearman's rank correlation coefficients. To determine the clinical value of CCSA-2 and CEA in those groups, their sensitivity and specifity was evaluated using ROC analysis. This analysis determines the accuracy and diagnostic value of both tests.

RESULTS

There was a positive correlation between markers in patients with colorectal cancer and a statistically significant relationship according to which respondents with higher concentrations of CCSA-2 also have higher concentrations of CEA (R=0.754, p<0,001). Concentrations of tumor markers increase and correlate with the clinical progression of the disease. Accuracy of CCSA-2 test using ROC analysis showed a slightly lower measurement of antigen CCSA-2 as diagnostic value in colorectal cancer in comparison to measurement of antigen CEA (accuracy of tests: CCSA-2 - 52%, CEA - 60%).

CONCLUSIONS

CCSA-2 as a single tumor marker has a low diagnostic value in colorectal cancer because of low sensitivity and specifity. The diagnostic value of novel marker is slightly lower than previously understood and accepted in clinical practice - CEA.

Mechanical regulation of nuclear structure and function

Mechanical loading induces both nuclear distortion and alterations in gene expression in a variety of cell types. Mechanotransduction is the process by which extracellular mechanical forces can activate a number of well-studied cytoplasmic signaling cascades. Inevitably, such signals are transduced to the nucleus and induce transcription factor-mediated changes in gene expression. However, gene expression also can be regulated through alterations in nuclear architecture, providing direct control of genome function. One putative transduction mechanism for this phenomenon involves alterations in nuclear architecture that result from the mechanical perturbation of the cell. This perturbation is associated with direct mechanical strain or osmotic stress, which is transferred to the nucleus. This review describes the current state of knowledge relating the nuclear architecture and the transfer of mechanical forces to the nucleus mediated by the cytoskeleton, the nucleoskeleton, and the LINC (linker of the nucleoskeleton and cytoskeleton) complex. Moreover, remodeling of the nucleus induces alterations in nuclear stiffness, which may be associated with cell differentiation. These phenomena are discussed in relation to the potential influence of nuclear architecture-mediated mechanoregulation of transcription and cell fate.

An architectural genetic and epigenetic perspective

The organization and intranuclear localization of nucleic acids and regulatory proteins contribute to both genetic and epigenetic parameters of biological control. Regulatory machinery in the cell nucleus is functionally compartmentalized in microenvironments (focally organized sites where regulatory factors reside) that provide threshold levels of factors required for transcription, replication, repair and cell survival. The common denominator for nuclear organization of regulatory machinery is that each component of control is architecturally configured and every component of control is embedded in architecturally organized networks that provide an infrastructure for integration and transduction of regulatory signals. It is realistic to anticipate emerging mechanisms that account for the organization and assembly of regulatory complexes within the cell nucleus can provide novel options for cancer diagnosis and therapy with maximal specificity, reduced toxicity and minimal off-target complications.

Defining central themes in breast cancer biology by differential proteomics: conserved regulation of cell spreading and focal adhesion kinase

Breast cancer is a highly heterogeneous disease, an observation that underscores the importance of elucidating conserved molecular characteristics, such as gene and protein expression, across breast cancer cell types toward providing a greater understanding of context-specific features central to this disease. Motivated by the goal of defining central biological themes across breast cancer cell subtypes, we conducted a global proteomic analysis of three breast cancer cell lines, MCF7, SK-BR-3, and MDA-MB-231, and compared these to a model of nontransformed mammary cells (MCF10A). Our results demonstrate modulation of proteins localized to the extracellular matrix, plasma membrane, and nucleus, along with coordinate decreases in proteins that regulate "cell spreading," a cellular event previously shown to be dysregulated in transformed cells. Protein interaction network analysis revealed the clustering of focal adhesion kinase (FAK), a fundamental regulator of cell spreading, with several proteins identified as mutually, differentially abundant across breast cancer cell lines that impact expression and activity of FAK, such as neprilysin and keratin 19. These analyses provide insights into conservation of protein expression across breast cancer cell subtypes, a subset of which warrants further investigation for their roles in the regulation of cell spreading and FAK in breast cancer.

Analysis of a serum test for prostate cancer that detects a second epitope of EPCA-2

BACKGROUND

We have previously shown that EPCA-2 can serve as a highly specific and sensitive serum marker for prostate cancer. As a component of our validation of this marker, we have performed an initial evaluation of an assay that detects a distinct epitope of the same protein: EPCA-2.19. The goals of this study are to characterize the sensitivity and specificity of the EPCA-2.19 assay, in a non-screening population, and to demonstrate that such test based has similar characteristics as the initial assay produced.

METHODS

Three hundred twenty-eight serum samples from men with PSA values < and >2.5 ng/ml who had negative biopsies, men with BPH, men with organ-confined and non-organ-confined prostate cancer, as well as control populations were evaluated using the EPCA-2.19 assay.

RESULTS

At a cut-off of 0.5 ng/ml and above, EPCA-2.19 has a specificity of 94% and a sensitivity of 91% in separating normal men with PSA < and >2.5 ng/ml, and men with BPH from those with prostate cancer. Receiver Operator Curve analyses of the EPCA-2.19 assay demonstrate an area under the curve of 0.982 (95% CI 0.952-0.996, P < 0.0001).

CONCLUSIONS

This study confirms our earlier findings that the assay that detects against a second epitope of EPCA-2 yields almost identical results to those obtained for the first published assay (EPCA-2.22). While this provides some validation of our earlier studies, larger multi-institutional studies still need to be performed.

NRP/B mutations impair Nrf2-dependent NQO1 induction in human primary brain tumors

Brain tumors are associated with genetic alterations of oncogenes and tumor suppressor genes. Accumulation of reactive oxygen species (ROS) in cells leads to oxidative stress-induced damage, resulting in tumorigenesis. Here, we showed that the nuclear matrix protein nuclear restricted protein in brain (NRP/B) was colocalized and interacted with NF-E2-related factor 2 (Nrf2). During oxidative stress response, NRP/B expression and its interaction with Nrf2 were upregulated in SH-SY5Y cells. Association of NRP/B with Nrf2 was crucial for NAD(P)H:quinone oxidoreductase 1 (NQO1) expression. NRP/B was localized predominantly in the nucleus of normal brain cells, whereas in primary brain tumors NRP/B was almost exclusively contained in the cytoplasm. In addition, unlike wild-type NRP/B, the expression of NRP/B mutants isolated from primary brain tumors was found in the cytoplasm, and these mutants failed to induce Nrf2-dependent NQO1 transcription. Thus, NRP/B mutations and their altered localization resulted in changes in NRP/B function and deregulation of Nrf2-dependent NQO1 activation in brain tumors. This study provides insights into the mechanism by which the NRP/B modulates Nrf2-dependent NQO1 induction in cellular protection against ROS in brain tumors.

Nuclear structure as a source of cancer specific biomarkers

There are few biomarkers that have been developed which have proven clinical utility for the detection and prognosis of cancer. Cancer is diagnosed today, in large part, by examining cells under the microscope and determining the shape and texture of the nucleus. The molecular underpinnings of this hallmark of cancer are the components of the nuclear matrix. Utilizing proteomics focused on this subset of proteins, biomarkers have been identified that are specific for cancer types including prostate, colon and bladder cancer. These cancer biomarkers now serve as the basis of assays which can specifically identify individuals with cancer by sampling their blood and/or urine. In addition, these may serve as potential therapeutic targeting or imaging approaches.

The potential role of purine-rich element binding protein (PUR) alpha as a novel treatment target for hormone-refractory prostate cancer

BACKGROUND

Hormonal therapy for advanced prostate cancer is typically effective at first, but almost all men suffer refractory disease which often is life threatening. The nuclear matrix comprises not only of the structural elements of the nucleus, but is associated with many components of the molecular machinery. Our aim is to find novel targets for the treatment of hormone-refractory prostate cancer (HRPC) by focusing on the composition of the nuclear matrix proteins (NMPs).

METHODS

LN96 cells were established at our Institution after long-term culturing of LNCaP cells under androgen deprived conditions. The composition of NMPs of LNCaP cells and LN96 cells were analyzed by two-dimensional (2D) electrophoresis and spots differentially expressed were investigated by mass spectrometry for identification. Among the spots identified, we analyzed the potential functional role of the identified proteins in prostate cancer cells by establishing stable overexpressed cells.

RESULTS

We found that purine-rich element binding protein (PUR)alpha was significantly repressed not only in NMPs but also in total protein and mRNA levels of LN96 cells in comparison to LNCaP cells under the same steroid deprived conditions. Moreover, PURalpha was decreased in its expression both at the protein and mRNA levels in the androgen-independent prostate cancer cell lines, PC3 and DU145 in comparison to LNCaP cells. Stably overexpressing PURalpha in PC3 and DU145 cells negatively regulates cell proliferation, resulting in decreases in PCNA expression.

CONCLUSION

Further dissection of the role of PURalpha in cell growth regulation may reveal a novel target for HRPC.

Evaluation of colon cancer-specific antigen 2 as a potential serum marker for colorectal cancer

PURPOSE

A blood test to detect colon cancer at a preventable stage would represent a major advancement. We have previously identified colon cancer-specific markers using focused proteomics analysis of nuclear structural proteins. Two of these markers, colon cancer-specific antigen (CCSA)-3 and CCSA-4, have been developed into blood-based markers that are able to distinguish individuals with colorectal cancer from those without. CCSA-2 is a distinct novel colon cancer marker identified using focused proteomics.

EXPERIMENTAL DESIGN

Using an indirect ELISA on serum samples obtained from two institutions, we evaluated CCSA-2 as a serum-based colon cancer marker. A total of 111 serum samples from individuals who underwent colonoscopy and were subsequently diagnosed as either being normal or having hyperplastic polyps, nonadvanced adenomas, advanced adenomas, and colorectal cancer were evaluated. A diverse control population that consisted of 125 serum samples was also included in this study.

RESULTS

Receiver operating characteristic analyses were used to measure the sensitivity and specificity of CCSA-2. CCSA-2 at a cutoff of 10.8 mug/mL has overall specificity of 78.4% [95% confidence interval (95% CI), 67.3-87.1%] and sensitivity of 97.3% (95% CI, 85.8-99.5%) in separating individuals with advanced adenomas and colorectal cancer from normal, hyperplastic, and nonadvanced adenoma populations. The receiver operating characteristic curve for CCSA-2 has an area under the curve of 0.90 (95% CI, 0.83-0.95).

CONCLUSION

Our initial study shows that CCSA-2 is a potential serum-based marker for colon cancer detection with high sensitivity and specificity.

SELDI protein profiling of dunning R-3327 derived cell lines: identification of molecular markers of prostate cancer progression

BACKGROUND

We recently demonstrated the protein expression profiling of Dunning rat tumor cell lines of varying metastatic potential (G (0%), AT-1 ( approximately 20%), and MLL (100%)) using SELDI-TOF-MS. As a parallel effort, we have been pursuing the identification of the protein(s) comprising the individual discriminatory "peaks" and evaluating their utility as potential biomarkers for prostate cancer progression.

METHODS

To identify the observed SELDI-TOF-MS m/z (mass/charge) values with discriminatory expression between different sublines, we employed a combination of chemical pre-fractionation, liquid chromatography, gel electrophoresis and tandem mass spectroscopy. Identified proteins were then verified by immuno-assay and Western analysis.

RESULTS

A 17.5 K m/z SELDI-TOF-MS peak was found to retain discriminatory value in each of two separate study-sets with an increased expression in the metastatic MLL line. Sequence identification and subsequent immunoassays verified that Histone H2B is the observed 17.5 K m/z SELDI peak. SELDI-based immuno-assay and Western Blotting revealed that Histone H2B is specifically over-expressed in metastatic MLL lines.

CONCLUSIONS

SELDI-TOF MS analysis of the Dunning prostate cancer cell lines confirmed the consistent overexpression of a 17.5 K m/z peak in metastatic MLL subline. The 17.5 kDa protein from MLL has been isolated and identified as Histone H2B.

Initial analyses of colon cancer-specific antigen (CCSA)-3 and CCSA-4 as colorectal cancer-associated serum markers

Colon cancer-specific antigen (CCSA)-3 and CCSA-4 are novel colon cancer markers identified by focused proteomic analysis of nuclear structural proteins. The goal of these studies was to evaluate serum-based CCSA-3 and CCSA-4 in the detection of individuals with preneoplastic and neoplastic lesions using ELISAs. Serum samples from 107 subjects undergoing colonoscopy, 28 subjects with colorectal cancer, and 125 subjects with benign disease or other types of cancer were evaluated. Individuals who underwent colonoscopy were classified into mutually exclusive categories, including normal colon, hyperplastic polyp, nonadvanced adenoma, and advanced adenoma. Sensitivity and specificity for both CCSA-3 and CCSA-4 were evaluated using receiver operating characteristic (ROC) curves. At a cutoff of 2 microg/mL for CCSA-3 and 0.3 microg/mL for CCSA-4, each marker detected all 28 colorectal cancers, for a sensitivity of 100% (lower 95% confidence bound, 89.8%). The sensitivity for detection of the combined end point of colorectal cancer and advanced adenoma for CCSA-3 was 89.1% [95% confidence interval (95% CI), 76.4-96.4%] and for CCSA-4 was 84.8% (95% CI, 71.1-93.7%) and 91.3% (95% CI, 79.2-97.6%) for either marker positive. The specificity in individuals with normal, hyperplastic polyps, or nonadvanced adenomas was 82.0% (95% CI, 72.4-89.4%) and 91.0% (95% CI, 83.0-96.0%) for CCSA-3 and CCSA-4, respectively. ROC curves for CCSA-3 and CCSA-4 reveal an area under the curve of 0.94 (95% CI, 0.90-0.98%). In these initial analyses, CCSA-3 and CCSA-4 show promise as potential serum markers for detection of colorectal cancer and advanced adenomas.

Nuclear microenvironments in biological control and cancer

Nucleic acids and regulatory proteins are compartmentalized in microenvironments within the nucleus. This subnuclear organization may support convergence and the integration of physiological signals for the combinatorial control of gene expression, DNA replication and repair. Nuclear organization is modified in many cancers. There are cancer-related changes in the composition, organization and assembly of regulatory complexes at intranuclear sites. Mechanistic insights into the temporal and spatial organization of machinery for gene expression within the nucleus, which is compromised in tumours, provide a novel platform for diagnosis and therapy.

Survivin expression is associated with bladder cancer presence, stage, progression, and mortality

BACKGROUND

The purpose was to compare the differential expression of Survivin in normal bladder tissue, bladder transitional cell carcinoma (TCC) of different stages, and to determine whether expression of Survivin is associated with TCC clinical outcomes.

METHODS

Immunohistochemical staining for Survivin was carried out on archival bladder specimens from 9 normal controls and 222 consecutive patients who underwent radical cystectomy and bilateral lymphadenectomy. Lymph node tissue involved with TCC from 50 of the 222 cystectomy patients was also evaluated.

RESULTS

Survivin was expressed in none of the normal bladder specimens, 64% of the cystectomy specimens, and 94% of the malignant lymph nodes. Multivariable analyses performed in the cystectomy patients revealed that Survivin expression was associated with disease recurrence (P = .040), disease-specific mortality (P = .037), and all-cause mortality (P = .044).

CONCLUSIONS

The findings of the study provide a rationale for further evaluation of Survivin and its downstream signaling pathways in bladder cancer and raise the potential for Survivin-targeted therapy for bladder cancer.

Mechanistic Analysis of the Role of BLCA-4 in Bladder Cancer Pathobiology

Analysis of alterations in nuclear structure associated with bladder cancer has revealed specific changes associated with the disease. This includes the identification of six bladder cancer-specific proteins and the successful development of urine-based immunoassays for the detection of two of these biomarkers, BLCA-1 and BLCA-4. The purpose of this study is to examine the functional aspects of BLCA-4 and its potential role in bladder cancer pathobiology. Sequence analysis of BLCA-4 reveals that it is a member of the ETS transcription factor family and that it seems to associate with transcription factors. To examine the effects of this protein, the gene encoding BLCA-4 was stably transfected into human urothelial cells. BLCA-4 expression was confirmed by both PCR and Western blot analysis. BLCA-4 overexpressing clones exhibit a 4.3-fold greater proliferation rate than vector only controls or untransfected cells. Microarray analysis comparing gene expression patterns between overexpressing clones and vector only controls revealed that numerous genes were up-regulated in cells that overexpress BLCA-4. Up-regulated genes included interleukin-1alpha (IL-1alpha), IL-8, and thrombomodulin, and the protein expression of these genes was confirmed by immunoblots. This information has provided a potential model of BLCA-4 action. Overexpression of BLCA-4 seems to increase the growth rate in cells and also causes cells to express a more tumorigenic phenotype.

USE OF THE NOVEL MARKER BLCA-1 FOR THE DETECTION OF BLADDER CANCER

PURPOSE

Bladder cancer specific nuclear structural alterations have been identified. We examined the expression pattern of one of these proteins, BLCA-1, in tissue and urine samples from individuals with bladder cancer as well as in samples from normal controls.

MATERIALS AND METHODS

BLCA-1 sequence data were used to produce antibodies to this protein, which were used in immunoblot and enzyme-linked immunosorbent assays.

RESULTS

BLCA-1 was detectable in tissue from patients with bladder cancer but not in normal adjacent areas of the bladder or in normal donor bladder tissue. This protein was also detectable in the urine of patients with bladder cancer by immunoblot and immunoassay. Using a cutoff of 0.025 optical density units (absorbance value) BLCA-1 was detected in 20 of 25 urine samples from patients with bladder cancer but in only 6 of 46 normal, high risk, prostate or renal cancer samples tested, resulting in a test with 80% sensitivity and 87% specificity. Expression of this protein did not appear to correlate with tumor grade.

CONCLUSIONS

This research indicates that BLCA-1 is a urine based marker of bladder cancer which may be useful for the detection of this disease.

p300 Modulates Nuclear Morphology in Prostate Cancer

Alterations in nuclear structure distinguish cancer cells from noncancer cells. These nuclear alterations can be translated into quantifiable features by digital image analysis in a process known as quantitative nuclear morphometry. Recently, quantitative nuclear morphometry has been shown to predict metastasis and biochemical recurrence of prostate cancer. However, little is known about the cellular mechanisms underlying these nuclear morphometric changes. Alterations of nuclear matrix proteins are frequently involved in changes of nuclear structure. A number of co-activators interact with these nuclear structure–related proteins, suggesting that they might be involved in quantitative nuclear morphometry changes. We have shown previously that the transcriptional co-activator p300 is involved in prostate cancer progression. However, the ability of a transcriptional regulator like p300 to modulate nuclear morphology has not been described previously. In the present study, we show that p300 expression in prostate cancer biopsy tissue from 95 patients correlates with quantifiable nuclear alterations. Moreover, we show that transfection of p300 into prostate cancer cells in culture induces quantifiable nuclear alterations, such as diameter, perimeter, and absorbance among others, as assessed by digital image analysis. These alterations correlate individually with aggressive features in prostate cancer, such as expression of the proliferation marker Ki-67 and extraprostatic extension of the tumor. Finally, we found that transfection of p300 into prostate cancer cells specifically increases mRNA and protein levels of nuclear matrix peptides lamins A and C, suggesting that these proteins mediate the p300-induced effects. These findings reveal a new insight into the transcriptional and structural regulation of prostate cancer.

The stability of the nuclear lamina polymer changes with the composition of lamin subtypes according to their individual binding strengths

The nuclear lamina, which provides a structural scaffolding for the nuclear envelope, consists largely of a polymer of the intermediate filament lamin proteins. Although different cell types contain distinctive relative amounts of the major lamin subtypes (A, C, B1, and B2), the functions of this variation are not understood. We have investigated the possibility that subtype variation affects lamina stability. We find that homotypic and heterotypic binding interactions of lamin B2 are substantially less resistant to chemical dissociation in vitro than those between the other lamin subtypes, whereas lamin A interactions are the most stable. Surprisingly, removal of the central four-fifths of the rod domain did not substantially weaken the interactions of lamins A and B2, suggesting that other regions also strongly contribute to their binding interactions. In contrast, this rod deletion strongly destabilizes the binding interactions of lamins B1 and C. Consistent with the binding studies, lamins are more readily solubilized by chemical extraction from cells enriched for lamin B2 than from cells enriched for lamin A. This suggests that the distinctive ensemble of heterotypic lamin interactions in a particular cell type affects the stability of the lamin polymer, and, correspondingly, could be relevant to tissue-specific properties of the lamina including its involvement in disease.

Genetic alterations of the NRP/B gene are associated with human brain tumors

Nearly all brain tumors develop following the progressive accumulation of genetic alterations of oncogenes and tumor suppressor genes (such as p53 and retinoblastoma protein). Furthermore, aberrations in the nuclear matrix often contribute to genomic instabilities and the development of cancer. We have previously shown that nuclear-restricted protein/brain (NRP/B), a member of the BTB/Kelch repeat family, is a nuclear matrix protein normally expressed in neurons but not in astrocytes, and that it is an early and specific marker of neurons during the development of the central nervous system. Here, we show aberrant expression of NRP/B in human brain tissues. NRP/B is expressed in the cytoplasm of human brain tumor cells (glioblastoma, GBM) arising from astrocytes. NRP/B mutations (13 mutations in the Kelch domains, two in the intervening sequence (IVS) domain and two in the BTB domain) were detected in brain tumor cell lines (A-172, CCF-STTG1, SK-N-SH and U87-MG) and in primary human malignant GBM tissues (eight samples). More importantly, we found that NRP/B mutants, but not wild-type (wt) NRP/B, increased the activation of ERK and consequently promoted cell proliferation, attenuated caspase activation and suppressed the cellular apoptosis induced by the stressful stimulus cisplatin (10 microM). These events were observed to occur via a p53-mediated pathway. In addition, while wt NRP/B was associated with actin, mutations in the Kelch domains of NRP/B led to its reduced binding affinity to actin. Thus, alterations and gene mutations within the NRP/B gene may contribute to brain tumorigenesis by promoting cell proliferation, suppressing apoptosis and by affecting nuclear cytoskeleton dynamics.

Nuclear matrix proteins as biomarkers in prostate cancer

The nuclear matrix (NM) is the structural framework of the nucleus that consists of the peripheral lamins and pore complexes, an internal ribonucleic protein network, and residual nucleoli. The NM contains proteins that contribute to the preservation of nuclear shape and its organization. These protein components better known as the NM proteins have been demonstrated to be tissue specific, and are altered in many cancers, including prostate cancer. Alterations in nuclear morphology are hallmarks of cancer and are believed to be associated with changes in NM protein composition. Prostate cancer is the most frequently diagnosed cancer in American men and many investigators have identified unique NM proteins that appear to be specific for this disease. These NM protein changes are associated with the development of prostate cancer, as well as in some cases being indicative of cancer stage. Identification of these NM proteins specific for prostate cancer provides an insight to understanding the molecular changes associated with this disease. This article reviews the role of NM proteins as tumor biomarkers in prostate cancer and the potential application of these proteins as therapeutic targets in the treatment of this disease.

Characterization of the nuclear matrix proteins in a transgenic mouse model for prostate cancer

The nuclear matrix (NM) contains a number of proteins that have been found to be associated with transformation. We have previously identified changes in the NM associated with prostate cancer. In this study, we examine the molecular changes that are associated with prostate cancer development in transgenic adenocarcinoma of mouse prostate (TRAMP) model by studying the differences in the NM proteins (NMPs). We collected prostates from the TRAMP males at six critical time points: 6 weeks (puberty), 11 and 19 weeks (development of mild hyperplasia), 25 weeks (development of severe hyperplasia), 31 and 37 weeks (development of neoplasia). The nuclear matrices from the prostates collected at these time points were then isolated and the NMPs were characterized by high-resolution two-dimensional gel electrophoresis. We found three NMPs (E1A, E1B, and E1C) that were present in the 6-week-old prostate and two NMPs (E2A and E2B) that were present in the 11-week-old prostate. These NMPs were absent in the 31- and 37-week-old prostate. We also found five NMPs (E3A-E3E) that were present in the 31-week-old prostate, but absent in the earlier time points. In addition, three NMPs (Le1, Le2, Le3) were present at higher expression in the 6-, 11-, 19-, and 25-weeks old TRAMP prostates, but they were expressed lower during the development of neoplasia at 31- and 37-weeks old. Identification of these NMPs permits the development of novel markers that can characterize various stages of prostate cancer development as well as potentially therapeutic targets.

Proteome analysis of hepatocellular carcinoma

Development of hepatocellular carcinoma (HCC) is a complex process involving multiple changes in gene expression and usually occurs in the presence of liver cirrhosis. In this research, we observed proteome alterations of three tissue types isolated from livers of HCC patients: normal, cirrhotic, and tumorous tissue. Proteome alterations were observed using two-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Comparing the tissue types with each other, a significant change in expression level was found in 21 proteins. Of these proteins, sarcosine dehydrogenase, liver carboxylesterase, peptidyl-prolyl isomerase A, and lamin B1 are considered novel HCC marker candidates. In particular, lamin B1 may be considered as a marker for cirrhosis, because its expression level changes considerably in cirrhotic tissue compared with normal tissue. The proteins revealed in this experiment can be used in the future for studies pertaining to hepatocarcinogenesis, or as diagnostic markers and therapeutic targets for HCC.

Multiple antibodies to titin immunoreact with AHNAK and localize to the mitotic spindle machinery

Recently, the large filamentous striated-muscle protein titin has been observed in non-muscle cells, and, in one instance, has been proposed to have a nuclear function as a chromosomal component contributing to structure and elasticity. In this study, we sought to further characterize the presumptive nuclear isoform of titin. Immunofluorescence microscopy with multiple titin-specific monoclonal antibodies shows localization to the nucleus in interphase cells and to the spindle machinery in mitotic cells in all cell types examined; localization to condensed chromosomes is not observed. An abundant 700-kDa phosphoprotein is the predominant species immunoprecipitated with these antibodies. Sequencing of peptide fragments of the immunopurified protein reveals identity to AHNAK, a nuclear phosphoprotein, an identification that was confirmed by Western blot analysis with antibodies to AHNAK and peptide fragmentation patterns. Sequence comparison suggests similarities between the repetitive heptad phi+/-phiP+/-phi+/- motif in AHNAK and the PEVK region of titin, potentially explaining the cross-reactivity observed between AHNAK antibodies and titin antibodies. Interestingly, although some AHNAK antibodies stain interphase nuclei, no evidence of mitotic spindle localization is seen, suggesting that the identity of the protein at the latter location is more closely related to titin than AHNAK. This concept is further supported by observations that cell lines not expressing AHNAK have similar antititin antibody localization to the mitotic spindle. We conclude that (1) multiple titin antibodies, particularly those recognizing the PEVK region, cross-react with AHNAK, and (2) the mitotic spindle staining observed with antititin antibodies is most likely due to the association of titin or a titin-like molecule with this structure.

Signal transduction pathways and chromatin structure in cancer cells

Molecular mechanisms controlling gene expression include cell shape, mechanical and chemical signal transduction pathways, chromatin remodeling, and DNA methylation. In this article, we will review the contribution of these molecular mechanisms and structural alterations in the malignant transformation of cells. The mechanical signaling pathway consists of the tissue matrix system that links together the three-dimensional skeletal networks, the extracellular matrix, cytoskeleton, and nuclear matrix. The cytoskeleton array is a dynamic system that transmits signals from the cell exterior to nuclear DNA. The composition and function of this mechanical signaling pathway is altered in cancer cells. Chemical signaling pathways such as the Ras/mitogen-activated protein kinase (MAPK) pathway stimulate the activity of kinases that modify transcription factors, histones, and chromatin remodeling factors. Oncoproteins deregulating this signaling pathway set in motion a series of events that cumulate to chromatin remodeling and aberrant gene expression. J. Cell. Biochem. Suppl. 35:27-35, 2000.

Rearrangement of chromatin domains in cancer and development

Both the accomplishment of developmental programs and neoplastic transformation are linked to changes in the long-range organization of chromatin, in particular, DNA loop domains. The development of new methods that allow the study of interactions between the bases of DNA loops and the proteins of the nuclear matrix will help our understanding of the molecular mechanisms in such changes. These methods should also allow the establishment of a fingerprint "signature" for many cancers that may serve for diagnostic purposes. J. Cell. Biochem. Suppl. 35:54-60, 2000.