Expression of the nuclear protein mitotin in differentiating in vitro HL 60 cells

Minichromosome maintenance proteins 2 and 5 in non-benign epithelial ovarian tumours: relationship with cell cycle regulators and prognostic implications

Minichromosome maintenance proteins (MCM) have recently emerged as novel proliferation markers with prognostic implications in several tumour types. This is the first study investigating MCM-2 and MCM-5 immunohistochemical expression in a series of ovarian adenocarcinomas and low malignant potential (LMP) tumours aiming to determine possible associations with clinicopathological parameters, the conventional proliferation index Ki-67, cell cycle regulators (p53, p27(Kip1), p21(WAF1) and pRb) and patients' outcome. Immunohistochemistry was applied in a series of 43 cases of ovarian LMP tumours and 85 cases of adenocarcinomas. Survival analysis was restricted to adenocarcinomas. The median MCM-2 and MCM-5 labelling indices (LIs) were significantly higher in adenocarcinomas compared to LMP tumours (P<0.0001 for both associations). In adenocarcinomas, the levels of MCM-2 and MCM-5 increased significantly with advancing tumour stage (P=0.0052 and P=0.0180, respectively), whereas both MCM-2 and MCM-5 increased significantly with increasing tumour grade (P=0.0002 and P=0.0006, respectively) and the presence of bulky residual disease (P<0.0001 in both relationships). A strong positive correlation was established between MCM-2 or MCM-5 expression level and Ki-67 LI (P<0.0001) as well as p53 protein (P=0.0038 and P=0.0500, respectively). Moreover, MCM-2 LI was inversely correlated with p27(Kip-1) LI (P=0.0068). Finally, both MCM-2 and MCM-5 were associated significantly with adverse patients' outcome in both univariate (> or =20 vs >20%, P=0.0011 and > or =25 vs <25%, P=0.0100, respectively) and multivariate (P=0.0001 and 0.0090, respectively) analysis. An adequately powered independent group of 45 patients was used in order to validate our results in univariate survival analysis. In this group, MCM-2 and MCM-5 expression retained their prognostic significance (P<0.0001 in both relationships). In conclusion, MCM-2 and MCM-5 proteins appear to be promising as prognostic markers in patients with ovarian adenocarcinomas.

A Differential Phosphoproteomic Analysis of Retinoic Acid-Treated P19 Cells

External stimuli trigger internal signaling events within a cell that may represent either a temporary or permanent shift in the phosphorylation state of its proteome. Numerous reports have elucidated phosphorylation sites from a variety of biological samples and more recent studies have monitored the temporal dynamics of protein phosphorylation as a given system is perturbed. Understanding which proteins are phosphorylated as well as when they are phosphorylated may indicate novel functional roles within a system and allow new therapeutic avenues to be explored. To elucidate the dynamics of protein phosphorylation within differentiating murine P19 embryonal carcinoma cells, we induced P19 cells to differentiate using all-trans-retinoic acid and developed a strategy that combines isotopically labeled methyl esterification, immobilized metal affinity chromatography, mass spectrometric analysis, and a rigorous and unique data evaluation approach. We present the largest differential phosphoproteomic analysis using isotopically labeled methyl esterification to date, identifying a total of 472 phosphorylation sites on 151 proteins; 56 of these proteins had altered abundances following treatment with retinoic acid and approximately one-third of these have been previously associated with cellular differentiation. A series of bioinformatic tools were used to extract information from the data and explore the implications of our findings. This study represents the first global gel-free analysis that elucidates protein phosphorylation dynamics during cellular differentiation.

Minichromosome maintenance proteins 2 and 5 expression in muscle-invasive urothelial cancer: a multivariate survival study including proliferation markers and cell cycle regulators

Evaluation of cell cycle regulators has gained special interest in the effort to increase the amount of prognostic information in malignant tumors. Minichromosome maintenance proteins (MCMs) drive the formation of prereplicative complexes, which is the first key event during G1 phase. Therefore, altered MCM expression may be a hallmark of cell cycle deregulation, which is supposed to be the most essential mechanism in the development and progression of bladder cancer. Our aim was to investigate the value of MCMs as proliferation markers and prognostic indicators in detrusor muscle-invasive urothelial bladder carcinomas. We analyzed immunohistochemically the expression of MCM-2 and MCM-5 in 65 patients with detrusor muscle-invasive urothelial bladder carcinomas in relation with clinicopathologic parameters, patients' overall and disease-free survival, and the expression of the conventional proliferation index Ki-67 and other cell cycle modulators (p53, pRb, p21(WAF1), and p27(Kip1)). The levels of MCM-2 and MCM-5 were significantly higher in high-grade (P < .0001), advanced-stage (P = .001), and nonpapillary tumors (P < .0001). The expression of MCM-2 and MCM-5 significantly associated with the conventional proliferation index Ki-67 (P = .0001 for each protein). The expression of MCM-2 or MCM-5 positively correlated with p53 labeling index (P = .014 and P = .009, respectively). Also, median p21(WAF1) labeling index was higher in MCM-5 high expressors (P = .028). Finally, both MCM-2 and MCM-5 associated significantly with adverse patients' outcome in both univariate (P = .0072 and P = .0074, respectively) and multivariate (P = .0001) analysis. In conclusion, MCM-2 and MCM-5 appear to be reliable proliferation indexes and useful prognostic markers in patients with muscle-invasive urothelial bladder carcinomas.

Expression of replication-licensing factors MCM2 and MCM3 in normal, hyperplastic, and carcinomatous endometrium: correlation with expression of Ki-67 and estrogen and progesterone receptors

Minichromosome maintenance (MCM) proteins are essential for cell cycling due to their function as replication-licensing factors. The aim of the present study was to investigate the clinicopathologic implications of the MCM2 and MCM3 in endometrial carcinogenesis. The authors investigated the immunohistochemical expression of MCM2 and MCM3, Ki-67, estrogen receptor, and progesterone receptor in 23 normal endometria, 9 endometrial hyperplasias, and 60 endometrial carcinomas. In the normal endometrial glands, the expression of MCM2 and MCM3 was significantly higher in the proliferative phase than in the secretory phase and was strongly correlated with Ki-67 expression. Similar correlation between the expression of MCMs and Ki-67 was also found in endometrial hyperplasia. In endometrial carcinomas, however, the expression of MCM2 and MCM3 was significantly lower than that in the normal proliferative endometrium. There was only a weak correlation between MCM2 and Ki-67, and no significant correlation between MCM3 and Ki-67 expression. These findings suggest that the expression of MCM2 and MCM3 directly reflects cell proliferation in normal and hyperplastic endometria. In endometrial carcinomas, however, there is a discrepancy between the expression of MCMs and cell proliferation, suggesting that the replication-licensing system may be aberrant in endometrial carcinomas.

Minichromosome maintenance 2 expression is correlated with mode of invasion and prognosis in oral squamous cell carcinomas

BACKGROUND

This study examined the immunohistochemical expression of cell-cycle related molecules as well as cell proliferation and pathologic findings in oral squamous cell carcinoma (SCC) in order to clarify their pathobiologic and prognostic significance.

METHODS

A total of 46 oral SCC specimens were analyzed using Ki-67, minichromosome maintenance 2 (MCM2), p53, p27, p21, and TUNEL. Aspects including tumor differentiation, mode of carcinoma invasion, tumor metastasis, and patient prognosis were compared among the specimens.

RESULTS

A significantly higher MCM2 labeling index (LI) was observed in the moderately differentiated SCCs when compared to the well-differentiated SCCs (P<0.05). The higher MCM2 LI was correlated with mode of invasion Grade 4 (infiltrative growth) and patient prognosis. In contrast, the LIs of Ki-67, TUNEL-signal, p53, p27, and p21 were not correlated with patient prognosis.

CONCLUSION

Higher MCM2 LI provides useful information for patient prognosis in oral SCCs.

Nuclear matrix proteins as structural and functional components of the mitotic apparatus

The eukaryotic nucleus is a membrane-enclosed compartment containing the genome and associated organelles supported by a complex matrix of nonhistone proteins. Identified as the nuclear matrix, this component maintains spatial order and provides the structural framework needed for DNA replication, RNA synthesis and processing, nuclear transport, and steroid hormone action. During mitosis, the nucleoskeleton and associated chromatin is efficiently dismantled, packaged, partitioned, and subsequently reassembled into daughter nuclei. The dramatic dissolution of the nucleus is accompanied by the assembly of a mitotic apparatus required to facilitate the complex events associated with nuclear division. Until recently, little was known about the fate or disposition of nuclear matrix proteins during mitosis. The availability of specific molecular probes and imaging techniques, including confocal microscopy and improved immunoelectron microscopy using resinless sections and related procedures, has enabled investigators to identify and map the distribution of nuclear matrix proteins throughout the cell cycle. This chapter will review the structure, function, and distribution of the protein NuMA (nuclear matrix mitotic apparatus) and other nuclear matrix proteins that depart the nucleus during the interphase/mitosis transition to become structural and functional components within specific domains of the mitotic apparatus.

What really cures in autologous bone marrow transplantation? A possible role for dimethylsulfoxide

Dimethylsulfoxide has long been known to be a potent inducer of differentiation of various malignant cells in animals and human beings. It is a toxic agent, and high concentrations are needed to induce differentiation. Other compounds that also have methylene groups and a polar/apolar architecture, and are needed in much smaller concentrations to induce differentiation, like hexamethylene bisacetamide have been developed. They are already used in trials in human beings. However dimethylsulfoxide still has a very important role in bone marrow transplantation, being added to the frozen marrow as a cryoprotectant. We suggest that dimethylsulfoxide may induce differentiation of malignant cells present in the marrow or alternatively in the body when it is infused back with the transplanted marrow. This may be an additional factor contributing to the success rate achieved in various malignancies treated by transplantation, especially autologous, complementing the traditional explanations which are based mainly on the high dose chemotherapy and the immunological manipulations that occur during transplantation.

Detection of the 125-kDa nuclear protein mitotin in centrosomes, the poles of the mitotic spindle, and the midbody

Mitotin is a nuclear protein detectable in all proliferating cells investigated so far, including human and plant cells. In interphase cells the protein is localized mainly in the nucleoplasm. In G2/M phase it displays a characteristic redistribution and a marked increase which initiated the name mitotin. This study presents the precise localization of mitotin in cytoplasmic structures in two cell types, the potoroo rat kangaroo PtK2 cell and the human lung cancer EPLC 65 cell. In addition to its nuclear localization the antigen is detectable in centrosomes, in the poles of the mitotic spindle, and along spindle fibers. During the last mitotic stages, cytokinesis and reconstitution of nuclei, mitotin displays a rapid decrease and another redistribution. A significant amount of the antigen is retained in the bridge connecting the dividing cells, the midbody.