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Objective: To investigate arsenic trioxide (As(2)O(3))-induced apoptosis and the effects on cell nuclear matrix related protein promyelocytic leukaemia (PML)., Methods: HepG2 cells were cultured in MEM medium and treated with 0.5, 2, 5 and 10 micro mol/L As(2)O(3) for either 24 h or 96 h at each concentration. In situ terminal deoxynucleotidyl transferase (TdT) labeling (TUNEL) and DNA ladders were used to detect apoptosis. Confocal microscopy and Western blotting were used to observe the expression of PML., Results: The growth rates of HepG2 cells were slower in the As(2)O(3) treated than the untreated control group. DNA ladder and TUNEL positive apoptotic cells could be detected in As(2)O(3) treated groups. The expression of PML decreased in HepG2 cells with 2 micro mol/L As(2)O(3) treatment. Confocal images demonstrated that the expression of PML protein in HepG2 cell nuclei decreased after treatment with 2 micro mol/L As(2)O(3), and micropunctates characteristic of PML protein in HepG2 cell nuclei disappeared after treatment with 5 micro mol/L As(2)O(3)., Conclusions: Our results show that arsenic trioxide can significantly inhibit the growth of HepG2 cells in vitro. As(2)O(3) induces apoptosis in HepG2 tumor cells in a time and concentration dependent manner. As(2)O(3) may degrade the PML protein in HepG2 cell nuclei. The decreased expression of PML in As(2)O(3) treated tumor cells is most likely to be caused by apoptosis. Nuclear matrix associated protein PML could be the target of As(2)O(3) therapy.

Anticancer agents interfere with the proliferation and survival of tumor cells by a variety of mechanisms. An important factor in the development of a cytotoxic effect by certain anticancer agents is the localization of drug-induced lesions within the cell nucleus. Drug-target interactions at the level of nuclear matrix (NM) may be critical events in the induction of cell death by some of these agents. Arsenic trioxide (As2O3) was identified as a very potent anti-leukemic agent by inducing apoptosis. The present study shows that As2O3 significantly inhibits the growth of hepatoblastoma cell line, HepG2, changes the composition of nuclear matrix proteins and reduces the expression of Hsc 70 and HNF4 in HepG2, which in turn initiate a cascade of events that compromise multiple nuclear functions and, ultimately, cell survival.

The aims of the present study were to assess the effects of arsenic trioxide on the nuclear matrix protein profiles of mouse neuroblastoma cells. Arsenic trioxide induces apoptosis of acute promyelocytic leukemia cells. Our results demonstrated that 2 microM As2O3 could significantly inhibit the growth of Neuro-2a cells. As early as 24 hours after As2O3 treatment, we began to observe the alteration of nuclear matrix proteins and apoptosis in tumor cells by TUNEL assay but not by DNA ladder. An increase expression of Hsc in nuclear matrix proteins of 2 microM As2O3 treated cells was also noted. Our results also showed that before a mass range of apoptosis occurred, the composition of nuclear matrix proteins had altered. Hence the alteration of nuclear matrix proteins, such as increased expression of Hsc, may be a sensitive indicator for the detection of early apoptosis.

Esophageal cancer is a common cancer among ethnic Chinese. The reported incidence of esophageal cancer has increased many fold in the past decades and is apparently still rising. Nuclear matrix forms the scaffold of the nucleus and participates in various nuclear functions. Cancer specific nuclear matrix proteins have been identified in several tumor systems. 2-D gel analysis shows the presence of novel nuclear matrix proteins in ATRA treated tumor cells and these proteins are cell line specific. Our preliminary study also shows ATRA altered the nuclear matrix density of tumor cells. The significance of these nuclear matrix proteins is discussed.

The association of epidermal growth factor receptor DNA fragments with nuclear matrix in glioblastoma cell lines was investigated. Two different DNA fragments (primer I-III, 940 bp and primer IV-V, 110 bp) were amplified in both genomic DNA and nuclear matrix-associated DNA. It was found that the 110 bp DNA fragment (primer IV-V) from a non-encoding region was more closely associated with the nuclear matrices of cell line U343, U373, A172, and T98 than with U87. The other DNA fragment (primer I-III) was found in both the genomic DNA and NM DNA from cell line of U343 and U87. Another long DNA fragment (primer I-II, 1015 bp) was not detected in the DNA of all cell lines. Our findings suggest that the attachment of the 110 bp DNA fragments to nuclear matrix may contribute to the growth and malignancy of glioblastoma.

The epithelial neoplasia constitute 60% of all primary tumors of the ovary and 90% of these are malignant. Nuclear matrix has been found to be involved in normal and abnormal nuclear activities. Previously, we have identified tumor-associated nuclear matrix proteins in cancers of human liver, nasopharynx and cervix. In this study, we compared nuclear matrices of immortalized ovarian and cancer cell lines by morphometric and 2-D gel electrophoresis analysis.

Human papillomavirus (HPV) is one of the crucial factors in cervical carcinogenesis. High risk HPV16 prototype has been demonstrated in association with the nuclear matrix in a cervical carcinoma cell line(1,2). Nuclear matrix (NM) has been established as playing an important role in various nuclear activities as well as carcinogenic processes. Dexamethasone (DEX) (glucocorticoid hormone) inhibited the growth of CC2/CUHK2 cervical carcinoma cells with concurrent induction of epithelial cell differentiation. 2D- PAGE (IEF and NEPHGE) revealed alternations in NM protein composition. Further demonstration of changes in NM was evidenced by NuMA (a novel NM protein) labelling. The HPV16 E7 oncoprotein was shown to be reduced in total cellular protein as well as in NM protein fractions in response to DEX treatment, and this suppressed expression was confirmed by RT-PCR. Thus, it is suggested that dexamethasone can down-regulate the growth of cervical cancer cells and its induced changes in NM may be a cause of this suppression.

Selective extraction, whole mount cell preparation and DGD embeddment-free section were involved in visualizing the nuclear matrix-lamina-intermediate filament system in PtK 2 cells. After extraction the anaphase chromosome residues adjoined to the cytoplasmic intermediate filament in some areas. Immunofluorescent staining showed us that the intermediate filament reacted with AE 1 and AE 3; McAb 223 could be localized specifically on the lamina while McAb C 23 could crossreact with cytoplasmic intermediate filament beside the lamina location, monoclonal antibody against lamin A (C) could also bind to chromosome residues. Antibody to 280 kD nuclear matrix protein which were positive stained in HeLa cells could not react with the nuclear matrix components of PtK 2 cells. 2-D electrophoresis demonstrated that there were some differences in the composition of the nuclear matrix-lamina-intermediate filament system of HeLa and PtK 2 cells. TdR treatment could lead to alteration of nuclear matrix proteins.

The nucleus of the mammalian sperm is formed after a series of morphological and biochemical changes during spermatogenesis. The human sperm nucleus, after sequential extraction with detergents, nuclease and ammonium sulfate, consists of a fibroskeletal structure which maintains the original nuclear shape. The chromatin-depleted skeleton is formed by thick and thin fibers as well as electron-dense patches of different sizes. These highly branched matrix fibers had average diameters of 35 and 12 nm. Polarization of the fibroskeletal structure is apparent and can be used as a good model to study the function of nuclear matrix in nuclear compartmentation in germ cells.

The nucleus of the mammalian spermatid undergoes a series of changes in its chromatin and nucleoprotein composition during transport from testis to epididymis. The sperm DNA is very tightly packaged by protamines instead of histones in somatic cells. However, the nuclear matrix and its association with DNA have not yet been definitively scrutinized with the electron microscope. The present study reveals that the protamine-depleted sperm nuclear matrix appears as a network of thick and thin filaments with glodular structures attached the these fibers. Monoclonal antibody to single- and doublestranded DNA was used to localize remnant DNA after extraction. By immunofluorescence microscopy, monoclonal antibody against DNA was localized outside the nucleus as a halo. Immuno-electron microscopy showed that gold particles were mainly associated with nuclear matrix surrounding the sperm head. Our results suggest a specific structural organization of sperm DNA with its matrix.

Two cell lines, the less differentiated CC2/CUHK2 and the more differentiated CC3/CUHKE3, were used to study the difference in nuclear matrix stability against DNase 1 digestion. The nuclear matrix was almost totally extracted when the CC3/CUHK3 cells were digested with 100 micrograms/ml DNase 1, while that of the CC2/CUHK2 cells was still present even when 200 micrograms/ml DNase 1 was used. It is suggested that more differentiated cells have a less stable nuclear matrix while the less differentiated ones have a more stable nuclear matrix. The same phenomenon was also observed in normal human and rat cervical epithelia. The nuclear matrix of the poorly differentiated basal cells was more stable than that of the more differentiated superficial cells. This cell differentiation stage dependent stability of the nuclear matrix is probably related to the nuclear activity and gene expression.

The nuclear matrix is a nonchromatin structure of the nucleus normally concealed by a much larger mass of chromatin. Several methods have been developed to remove chromatin from nucleus while preserving the underlying matrix architecture to some degree. The present study showed that after extraction of PtK2 cells and cervical carcinoma cells (CC3) with Triton X-100, ammonium sulfate and DNase, the nucleolar-nuclear matrix-intermediate filament (Nu-Nm-L-IF) network remained. The nucleolus was oval in shape and appeared as a fibrillar mass with an accentric dense fibrillar centre. This nucleolar skeleton was in direct connection with the nuclear matrix which in turn is connected with cytoplasmic intermediate filaments by lamins. It is concluded from these observations that the Nu-NM-L-IF system forms a continuous system which plays an important role in the maintenance of the nucleolar, nuclear and cytoplasmic integrity and cellular function.

The rat sperm nucleus, after sequential extraction with detergents, nuclease and ammonium sulfate, consists of a skeletal structure that resembles the original nuclear shape. This chromatin-depleted skeleton is formed by thick and thin fibers as well as globular structures of different sizes. These fibers form anastomosis. The sperm nuclei obtained from testis and caput epididymis exhibits a loose fibrous network with thin fibers at the center. The entire nucleus of the sperm in the caudal epididymis is formed by a dense network of thick and thin fibers. These highly branched matrix fibers had diameters of 35 and 12 nm. It is concluded that the increase in density of the matrix fibers is related to the condensation of the chromatin in the maturation of the spermatozoa.

Microwave irradiation provides good fixation of human and animal tissues for light and electron microscopy. In this study, microwave irradiation was used for the fixation of cytoplasmic and nuclear matrix in tumor cells. The nuclear matrix appears well preserved and exhibits a network formed by thick and thin filaments. Hence microwave fixation can be used as a quick and effective method for the study of the morphology of nuclear matrix.