Cell Growth & Differentiation : the Molecular Biology Journal of the American Association for Cancer Research

Cardiolipin (CL) is essential for the functionality of several mitochondrial proteins. Its distribution between the inner and outer leaflet of the mitochondrial internal membrane is crucial for ATP synthesis. We have investigated alterations in CL distribution during the early phases of apoptosis. Using two classical models (staurosporine-treated HL-60 cells and tumor necrosis factor alpha-treated U937 cells), we found that in apoptotic cells CL moves to the outer leaflet of mitochondrial inner membrane in a time-dependent manner...

Although K-ras is frequently mutated in lung adenocarcinomas, the normal function of K-ras p21 in lung is not known. In two mouse (E10 and C10) and one human (HPL1D) immortalized lung cell lines from peripheral epithelium, we have measured total K-ras p21 and active K-ras p21-GTP during cell proliferation and at growth arrest caused by confluence. In all three cell types, total K-ras p21 increased 2- to 4-fold at confluence, and active K-ras p21-GTP increased 10- to 200-fold. It was estimated that 0.03% of total K-ras p21 was in the active GTP-bound state at 50% confluence, compared with 1...

Defective heme synthesis in mammals has been suspected of causing neuropathy associated with porphyrias and lead poisoning. To determine the molecular action of heme in neuronal cells, we examined the effect of the inhibition of heme synthesis on nerve growth factor (NGF) signaling in PC12 cells. We found that the inhibition of heme synthesis by succinyl acetone interferes with NGF-induced neurite outgrowth in PC12 cells. Furthermore, we show that heme deficiency obliterates the activation of the signaling intermediates of the Ras-mitogen-activated protein kinase signaling pathway and its downstream target, the transcription activator cyclic AMP response element-binding protein...

Changes to cell cycle-regulating machinery that occur during differentiation of cells are thought to be responsible mostly for withdrawal from cycling. Here, embryonal carcinoma (EC) cell lines were found that differ in their basal levels of p27 inhibitor of cyclin-dependent kinases but not in their growth rates, distribution of cells in phases of cell cycle, and their ability to differentiate. High basal levels of p27 did not substitute for up-regulation of p27 that in EC cells normally occurs early after entering a differentiation pathway...

The D-group cyclins play a key role in the progression of cells through the G(1) phase of the cell cycle. Treatment of MCF-7 breast cancer cells with the cyclopentenone prostaglandin 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) results in rapid down-regulation of cyclin D1 protein expression and growth arrest in the G(0)/G(1) phase of the cell cycle. 15d-PGJ(2) also down-regulates the expression of cyclin D1 mRNA; however, this effect is delayed relative to the effect on cyclin D1 protein levels, suggesting that the regulation of cyclin D1 occurs at least partly at the level of translation or protein turnover...

Human chondrosarcomas do not respond to current chemotherapies or radiation therapy, and their size and histological appearance do not reliably predict the risk of local recurrence and metastases, making selection of surgical treatment difficult. Identifying mechanisms responsible for the proliferation and invasive behavior of these tumors would be of immense clinical value. We hypothesized that telomerase expression is one of these mechanisms. We detected telomerase expression in 7 of 16 chondrosarcomas, but cells cultured from telomerase-negative chondrosarcomas acquired strong telomerase activity and lost tumor suppressor activity after their establishment in culture...

Human cancer cells often produce tumors in animal models that incompletely reproduce the histology of the parental tumor. Kaposi's sarcoma (KS) cells, in particular, have not produced durable angiogenic lesions in animal models that resemble those of KS in humans. We investigated the contribution of transformed KS cells, vascular endothelial growth factor (VEGF), and human skin tissue on tumor development in a human skin graft/mouse model. High levels of serum VEGF (322 pg/ml) were seen in HIV-1-infected persons with KS compared with HIV-1-infected persons without KS (115 pg/ml)...

The proliferative effects of gastrin on normal and malignant gastrointestinal tissues have been shown to be mediated by a G protein-coupled receptor (GPCR), the cholecystokinin B receptor. The c-Jun NH(2)-terminal kinase (JNK) pathway has been implicated in the regulation of mitogenesis by growth factors or cytokines. However, the contribution of this signaling cascade to the proliferative effects of GPCR remains largely unknown. Here, we show that cholecystokinin B receptor occupancy by gastrin leads to the activation of the JNK pathway...

Recent studies showed that specific isoprenoid modification may be critical for RhoB subcellular location and function. Therefore, we determined whether the function of the highly related RhoA protein is also critically dependent on specific isoprenoid modification: (a) in contrast to observations with RhoB or Ras proteins, where farnesylated and geranylgeranylated versions showed differences in subcellular location, both prenylated versions of RhoA showed the same plasma membrane and cytosolic location; (b) a farnesylated version of activated RhoA(63L) retained the same diverse functions as the normally geranylgeranylated RhoA(63L) protein, and both proteins show indistinguishable abilities to stimulate gene expression, cause growth transformation of NIH 3T3 mouse fibroblasts, to stimulate the motility of T47D human breast epithelial cells, and to block HIV-1 viral replication and gene expression; and (c) cells expressing farnesylated RhoA retained sensitivity to the growth inhibition caused by inhibition of geranylgeranyltransferase I, indicating that other proteins are critical targets for inhibitors of geranylgeranylation...

Epidermal growth factor receptor (EGFR) is up-regulated and contributes to the loss of growth control in squamous cell carcinoma of the head and neck (SCCHN). Previously, we reported an association between autocrine stimulation of EGFR and constitutive signal transducers and activators of transcription (STAT) 3 activation in SCCHN cells in vitro and in vivo. Here, we evaluated the role of activated STAT3 in tumor progression and EGFR-independent mitogenic signaling. We found that SCCHN cells stably transfected with a dominant active STAT3 construct expressed elevated levels of STAT3 target genes, including Bcl-X(L) and cyclin D1, and demonstrated increased proliferation in vitro and more rapid tumor growth rates in vivo...

A comparison between retinoic acid (RA) differentiation-resistant and differentiation-sensitive SK-N-BE neuroblastoma (NB) cell lines revealed an association between resistance to differentiation, exhibited by N-myc stable transfected SK-N-BE 9N cells, with sensitivity to RA induction of p50/p65 nuclear factor kappaB (NF-kappaB) transcription factor activity and induction of matrix metalloproteinase (MMP)-9 expression leading to enhanced invasive behavior in vitro. These effects were not observed in differentiation-sensitive parental SK-N-BE or control-transfected SK-N-BE 2N counterparts...

Retinoic acid (RA) receptor (RAR) beta2 has been shown to be underexpressed in human breast cancer cells, including MCF-7 cells, and recent reports have suggested that hypermethylation of the RAR beta2 promoter and 5'-UTR is the underlying cause. Here we show that RAR alpha2 is also underexpressed in MCF-7 breast cancer cells, at both the message and the protein level, relative to normal or nontumorigenic breast epithelial cells. Bisulfite sequencing of the CpG island in the RAR alpha2 promoter revealed highly penetrant and uniform cytosine methylation in MCF-7 cells...

Two isoforms of DNA topoisomerase II, alpha and beta, coded by separate genes, are expressed in actively cycling vertebrate cells. Some previous studies have suggested that only topoisomerase II alpha remains associated with chromosomes at mitosis. Here, the distributions of topoisomerase II alpha and beta in mitosis were studied by subcellular fractionation and by immunolocalization. Both isoforms of topoisomerase II were found to remain associated with mitotic chromatin. Topoisomerase II alpha was distributed along chromosome arms throughout mitosis and was highly concentrated at centromeres until mid-anaphase, particularly in some cell types...

Fas/CD95 is a type-I membrane glycoprotein, which inducesapoptotic cell death when ligated by its physiological ligand. We generated previously hyperproliferative sublines derived from the human T-cell leukemia Jurkat, Jurkat-ws and Jurkat-hp, which lost Fas/CD95 surface expression. We have now observed that the total amount of Fas protein is similar in the sublines and in the parental cells, indicating that in the sublines Fas remains in an intracellular compartment. We have found that the protein is directed toward lysosomes in the sublines, where it is degraded...

Recent studies indicate that kinase suppressor of Ras (KSR)is a scaffold protein for the Ras/Raf/MEK/ERK signaling cascade in mammals. To help determine the in vivo function of KSR, we have examined the tissue-specific distribution of this protein in the embryonic and adult mouse using a rat monoclonal antibody raised against the mouse protein. Western blot analysis indicates that the protein is expressed at highest levels in the adult brain. It is also expressed at low levels in bladder, ovary, testis, and lung, but the protein is not detectable in any other adult tissue...

We have demonstrated recently that Wilms' tumor suppressor 1 (Wt1),in addition to its role in genitourinary formation,is required for the differentiation of ganglion cells in the developing retina. Here we provide further evidence that Wt1 is associated with neuronal differentiation. Thus, the retinoblastoma-derived human cell line, Y-79, contained robust amounts of Wt1 mRNA and protein. Wt1 expression was down-regulated upon laminin-induced differentiation of Y-79 into neuron-like cells. Inhibition of Wt1 with antisense oligonucleotides dramatically reduced the capacity of undifferentiated Y-79 cells to undergo neuronal differentiation, whereas sense and missense oligonucleotides had no effect...

In this study, we characterize the function of the tumor suppressor gene PTEN in Jurkat T cells. We established stable clones of Jurkat T cells that inducibly express either wild-type or phosphatase-inactive PTEN. We show here that PTEN potently inhibited the growth and reduced the size of Jurkat cells. The growth-suppressive effect of PTEN was associated with its ability to induce apoptotic cell death with little or no effect on cell cycle. PTEN also rendered Jurkat cells more susceptible to apoptosis induced by various stimuli...

Bryostatin-1 inhibits acute myeloid leukemia (AML) in vitroat doses that stimulate the growth of normal hematopoietic progenitors.Although bryostatin-1 has a number of distinct biological activities, those specifically responsible for its antileukemic activity are unclear. We found that bryostatin-1 (10(-8) M) inhibited cell cycling at G(1), induced phenotypic evidence of differentiation, and limited the clonogenic growth of both AML cell lines and patient specimens. This activity was markedly enhanced by granulocyte/macrophage-colony stimulating factor, whereas growth factor-neutralizing antibodies completely inhibited both the differentiating and antileukemic activities of bryostatin-1...

Liver fibrosis occurs as a consequence of the transdifferentiationof hepatic stellate cells into myofibroblasts and is associated with an increased expression and activation of transforming growth factor (TGF)-beta1. This pluripotent, profibrogenic cytokine stimulates matrix synthesis and decreases matrix degradation, resulting in fibrosis. Thus, blockade of synthesis or sequestering of mature TGF-beta1 is a primary target for the development of antifibrotic approaches. The purpose of this study was to investigate whether the administration of adenoviruses constitutively expressing an antisense mRNA complementary to the 3' coding sequence of TGF-beta1 is able to suppress the synthesis of TGF-beta1 in culture-activated hepatic stellate cells...

Pluripotential human embryonal carcinoma (EC) cell linesundergo differentiation programs resembling those occurring in embryonal stem cells during development. Expression profiling was performed during the terminal differentiation of the EC cell line, NTera2/Clone D1 by all-trans-retinoic acid. Time-response analysis via clustering of >12,000 human transcripts revealed distinct stages in the transition from an EC cell to neuronal progenitor cells expressing patterning markers compatible with posterior hindbrain fates followed by the appearance of immature postmitotic neurons with an evolving synaptic apparatus...