Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate the role of RhoA on the intracellular membrane dynamics of lysosomes in rat hepatoma cells (MM1), we analyzed the localization of lysosomal aspartic proteinase cathepsin D by confocal immunofluorescence microscopy in the dominant active RhoA-transfected cells. Here we show that the transfection of the dominant active form of human small guanosine triphosphatase (GTPase) RhoA in MMI cells, a highly invasive cell line, causes the redistribution and spreading of small punctate structures stained for cathepsin D throughout the cytoplasm. We found that the microtubule organization was markedly different in the two cell lines: uniformly developed and polymerized microtubule filaments were seen in the mock transfectants; however, the dynamic organization of microtubules was less pronounced in the active RhoA transfectants. Furthermore, we found for the first time that a selective inhibitor of Rho-associated kinase (p160ROCK), Y-27632, impeded the subcellular spreading of cathepsin D staining and promoted reclustering of cathepsin D toward the perinuclear region in the active RhoA-transfected cells. To our knowledge, this is the first indication that the RhoA/ROCK-mediated signaling pathway is involved in the intracellular membrane dynamics of lysosomes by regulating the cytoskeletal microtubule organization as well as the actin cytoskeletons.
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PMID:Small guanosine triphosphatase Rho/Rho-associated kinase as a novel regulator of intracellular redistribution of lysosomes in invasive tumor cells. 1099 80

1-Oleoyl lysophosphatidic acid (LPA) induces transmonolayer migration (in vitro invasion) of rat ascites hepatoma MM1 cells and their morphological changes leading to the migration. We have previously shown that an LPA analog, palmitoyl cyclic phosphatidic acid (Pal-cPA), suppresses transmonolayer migration of MM1 cells by rapidly increasing the intracellular cyclic AMP (cAMP) concentration. We report here that various cAMP-elevating agents, including dibutyryl cAMP, forskolin, cholera toxin and 3-isobutyl-1-methylxanthine, consistently inhibited LPA-induced transmonolayer migration of MM1 cells. Moreover, pull-down assays for GTP-bound, active RhoA demonstrated that the blockage by cAMP-elevating agents of morphological changes leading to the migration was probably mediated through inhibiting RhoA activation.
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PMID:Hepatoma cell migration through a mesothelial cell monolayer is inhibited by cyclic AMP-elevating agents via a Rho-dependent pathway. 1106 34

We demonstrated previously that rat ascites hepatoma MM1 cells require both lysophosphatidic acid (LPA) and fibronectin (FN) for phagokinetic motility and transcellular migration and that these events are regulated through the RhoA-ROCK pathway. It remains to be elucidated, however, how the signals from both LPA and FN are integrated into cell migration. To examine this, total cellular lysates after stimulation with LPA or FN were subjected to time-course immunoblot analysis with anti-phosphotyrosine antibodies (Abs). Consequently, tyrosine-phosphorylation of paxillin was obviously persistent after stimulation with FN + LPA as compared to after stimulation with either alone. Tyrosine-phosphorylated paxillin comprised 2 components; slowly and fast migrating ones. Immunoblotting of anti-paxillin immunoprecipitates with phosphorylation site-specific Abs revealed the following: tyrosine-phosphorylation was enhanced preferentially on a slowly migrating component after stimulation with FN + LPA; this component contained phosphorylation at both tyrosine residue (Y) 31 and Y118; and phosphorylation of paxillin at Y181 was constitutive and not augmented by stimulation with either FN or LPA. Amiloride, an inhibitor of the Na+/H+ antiporter downstream of ROCK, suppressed cell motility and correspondingly paxillin tyrosine-phosphorylation at both Y31 and Y118. Paxillin phosphorylation weakly induced by FN alone, insufficient for cell migration, was not inhibited by amiloride. These results demonstrate that LPA collaborates with FN for persistent tyrosine phosphorylation of paxillin at both Y31 and Y118, regulated by the Na+/H+ antiporter downstream of ROCK and that this phosphorylated paxillin is essential for MM1 cancer cell migration.
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PMID:Involvement of phosphorylation of Tyr-31 and Tyr-118 of paxillin in MM1 cancer cell migration. 1177 84

We demonstrated previously that rat ascites hepatoma MM1 cells require both lysophosphatidic acid (LPA) and fibronectin (FN) for phagokinetic motility and transcellular migration and that these events are regulated through the RhoA-ROCK pathway and tyrosine phosphorylation of proteins including focal adhesion kinase (FAK). Moreover, we reported that palmitoyl-cyclic phosphatidic acid (Pal-cPA), a structural analogue of LPA, inhibits LPA-induced migration of MM1 cells and experimental metastasis of B16 murine melanoma cells. However, the molecular mechanisms of action of Pal-cPA remains to be clarified. To examine this, total cellular lysates after stimulation with LPA or FN were subjected to time-course immunoblot analysis with anti-phophotyrosine and anti-pY397-FAK antibodies. Tyrosine-phosphorylation of FAK especially at Tyr-397 was obviously persistent after stimulation with LPA + FN compared to after stimulation with LPA alone. This persistent phosphorylation was necessary for MM1 cell migration and inhibited by Pal-cPA as by C3 exoenzyme Rho inhibitor. RhoA activity (GTP-bound RhoA) was also measured by the pull down assay using the Rho binding domain of Rhotekin. LPA-induced RhoA-activation of MM1 cells was completely inhibited by Pal-cPA. Moreover, we demonstrated that autophosphorylation of FAK at Tyr-397, downstream of RhoA, contributed to formation of focal adhesions and was critical in LPA-induced MM1 cell migration by developing autophosphorylation-deficient (Y397F) FAK-transfectants. Collectively, Pal-cPA hampered LPA-induced morphological changes and transcellular migration of MM1 cells through downregulating active RhoA and inhibiting its downstream events including autophosphorylation of FAK. Pal-cPA also inhibited endogenous (LPA-independent) activation of RhoA in human fibrosarcoma HT-1080 cells. Pal-cPA may potentially provide a new therapy for the treatment of cancer invasion and metastasis.
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PMID:Cyclic phosphatidic acid inhibits RhoA-mediated autophosphorylation of FAK at Tyr-397 and subsequent tumor-cell invasion. 1273 90

The mevalonate metabolic pathway is necessary for the isoprenylation of a number of small GTPases. We have previously presented that Rho plays a pivotal role in 1-oleoyl-lysophosphatidic acid (LPA)-induced invasion of rat ascites hepatoma MM1 cells. Herein we report the effect of HMG-CoA reductase inhibitors, fluvastatin and lovastatin, on the in vitro invasion of MM1 cells. Fluvastatin and lovastatin inhibited LPA-induced MM1 cell invasion in a dose-dependent manner. Fluvastatin inhibited LPA-induced translocation of RhoA protein from the cytosol to the membrane and RhoA activation which was measured by pull-down assay for GTP-bound RhoA. Fluvastatin also inhibited the translocation of both endogenous and dominant-active RhoA from the cytosol to the membrane, actin stress fiber assembly and in vitro invasion of the cells expressing dominant-active RhoA (Val14-RhoA). These results indicate that HMG-CoA reductase inhibitors have the potential to reduce RhoA activation and cancer cell invasion by targeting the Rho protein isoprenylation.
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PMID:Inhibition of lysophosphatidic acid-induced RhoA activation and tumor cell invasion by 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors. 1296 1

Tumor hypoxia in a solid tumor mass has long been recognized as a cause of resistance to current cancer therapies, and has also been suggested to be a potent driving force towards malignancy. Recent progress in the understanding of the molecular mechanism of the tumor response to hypoxia has increased attention on targeting hypoxia for cancer therapy. We have generated a hypoxia-targeting fusion protein, TOP3, which is composed of a protein transduction domain (PTD) of HIV TAT, an oxygen-dependent degradation domain (ODD) of HIF-1 alpha, and procaspase-3. Here, we examine the effects of TOP3 in a rat ascites model. First, we clarified that the fluid in ascites from MM1 cells, which are derivatives of AH130 rat ascites hepatoma cells, was highly hypoxic. In vitro, MM1 cells retained protein degradation machinery through the ODD domain, and TOP3 effectively impaired MM1 cell growth in culture under hypoxic conditions by inducing apoptosis. Intraperitoneal administration of TOP3 prolonged the life span of rats bearing a significant amount of malignant ascites, and 60% of the treated animals were cured without recurrence of ascites. Thus, TOP3 had a dramatic effect on malignant ascites and, hence, we propose that rodent malignant ascites is an appropriate platform for testing hypoxia-targeted drugs.
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PMID:Targeting hypoxic cancer cells with a protein prodrug is effective in experimental malignant ascites. 1528 74

We have previously shown that transforming growth factor-beta1 (TGF-beta1) markedly stimulates the invasive capacity of rat ascites hepatoma AH130 W1 cells in vitro and in vivo. A differential hybridization procedure was used to isolate genes that were specifically up-regulated in TGF-beta1 treated W1 cells. Among ten independent cDNA clones, we focused on LMO7 and a variant isoform, LMO7S, that was generated by alternative splicing. LMO7 had PDZ and LIM domains, while LMO7S had only PDZ domain. TGF-beta1 up-regulated expression levels of LMO7 and LMO7S. LMO7 expression was up-regulated in the highly metastatic clone MM1.
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PMID:Transforming growth factor-beta1 induces LMO7 while enhancing the invasiveness of rat ascites hepatoma cells. 1573 92

In solid tumors, cancer cells are exposed to various microenvironmental stresses such as hypoxia, nutritional depletion, and low pH. Cancer cells adapt to these stresses and circumvent cell death. When the antiapoptotic signals overcome the stress, cancer cells might acquire physiologic functions, such as invasiveness, instead of cell death. Here, we report that tumor cells acquire an invasive capacity from apoptotic signals through caspase activation. We treated rat ascites hepatoma MM1 cells with an apoptosis-inducing drug, etoposide, or hypoxia, and assessed the invasion capacity with an in vitro bioassay. Although MM1 cells hardly showed invasiveness in serum-free medium, under stress conditions, invasive capacity accompanied with morphologic change was induced with caspase-3 activation. Such stress-induced invasion as well as morphologic change was suppressed by blocking caspase-3 activity with caspase inhibitors or by RNA interference of caspase-3. In contrast, lysophosphatidic acid-induced invasiveness was not affected by caspase-3 inhibition. These results suggest that caspase-3 activation contributes to the stress-induced invasive capacity of these cancer cells.
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PMID:Cross talk between apoptosis and invasion signaling in cancer cells through caspase-3 activation. 1623 Mar 65

Transforming growth factor-beta1 (TGF-beta1) is a multifunctional growth factor that plays a role in cell proliferation, differentiation, extracellular matrix production, apoptosis, and cell motility. We show here that TGF-beta1 increased the invasiveness of MM1 cells, which are a highly invasive clone of rat ascites hepatoma cells. Both mRNA and protein levels of RhoC but not RhoA in TGF-beta1-treated MM1 cells increased. In parallel with this increase in expression, RhoC activity was induced by TGF-beta1 treatment. When RhoC was overexpressed in MM1 cells, the invasive capacity increased. The RhoC-overexpressing cells formed more nodules than did mock cells when injected into rat peritoneum. Furthermore, when RhoC expression was reduced by transfection with shRNA/RhoC, the invasiveness of MM1 cells decreased with concomitant suppression of RhoC expression. Thus, the induced expression of RhoC by TGF-beta1 in MM1 cells plays a critical role in TGF-beta1-induced cell migration.
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PMID:RhoC is essential for TGF-beta1-induced invasive capacity of rat ascites hepatoma cells. 1675 Jan 70

Actin cytoskeletal reorganization is essential for tumor cell migration, adhesion, and invasion. Cofilin and actin-depolymerizing factor (ADF) act as key regulators of actin cytoskeletal dynamics by stimulating depolymerization and severing of actin filaments. Cofilin/ADF are inactivated by phosphorylation of Ser-3 by LIM kinase-1 (LIMK1) and reactivated by dephosphorylation by Slingshot-1 (SSH1) and -2 (SSH2) protein phosphatases. In this study, we examined the roles of cofilin/ADF, LIMK1, and SSH1/SSH2 in tumor cell invasion, using an in vitro transcellular migration assay. In this assay, rat ascites hepatoma (MM1) cells were overlaid on a primary-cultured rat mesothelial cell monolayer and the number of cell foci that transmigrated underneath the monolayer in the presence of lysophosphatidic acid (LPA) was counted. The knockdown of cofilin/ADF, LIMK1, or SSH1/SSH2 expression by small interfering RNAs (siRNAs) significantly decreased the LPA-induced transcellular migration of MM1 cells and their motility in two-dimensional culture. Knockdown of LIMK1 also suppressed fibronectin-mediated cell attachment and focal adhesion formation. Our results suggest that both LIMK1-mediated phosphorylation and SSH1/SSH2-mediated dephosphorylation of cofilin/ADF are critical for the migration and invasion of tumor cells and that LIMK1 is involved in the transcellular migration of tumor cells by enhancing both adhesion and motility of the cells.
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PMID:Suppression of the invasive capacity of rat ascites hepatoma cells by knockdown of Slingshot or LIM kinase. 1817 79


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