It is about time that Spain launches a National Cancer Act?
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Academic Medical Centers↗
Biomedical subjects
J C Lacal
Publications and source records attributed to J C Lacal.
Signal transduction and apoptosis pathways as therapeutic targets.
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Antineoplastic Agents↗
QSAR-derived choline kinase inhibitors: how rational can antiproliferative drug design be?
This review presents an overview of Choline Kinase (ChoK) inhibitors with antiproliferative activity. The consideration of ChoK as a novel target for the development of new anticancer drugs is justified. The synthesis of several derivatives based on structural modifications of hemicholinium-3 (HC-3) is not accompanied by potentiation of the neurological toxicity of HC-3. The increment of both ChoK inhibitory and antiproliferative activities was successfully obtained by the two following changes: a) substitution of the oxazonium moiety of HC-3 by several aromatic heterocycles, and b) using the 1,2-ethylene(bisbenzyl) moiety instead of the 4,4'-biphenyl fragment. In an attempt to understand the ChoK inhibitory activity, a quantitative structure-activity relationship was developed. The QSAR equations have described the forces involved in quantitative terms. The electron characteristic of the substituent at position 4 of the heterocycle and the lipophilic character of the whole molecule were found to significantly affect the antitumour activity in compounds 17-95. Trispyridinium compounds 91-95 are more potent than the bispyridinium ones 87-89 as ChoK inhibitors. Nevertheless, 91-95 are less active than 87-89 as antiproliferative agents because the latter show better lipophilicities to cross the cytosolic membranes. Inhibition of the growth of human tumours in nude mice has been demonstrated: Antitumour activity of compound 64 against human HT-29 produced a decrease of up to 70% in the size of the tumour in nude mice. These results indicate that ChoK can be used as a general target for anticancer drug design against Ras-dependent tumourigenesis.
Animals↗
Inhibition of ChoK is an efficient antitumor strategy for Harvey-, Kirsten-, and N-ras-transformed cells.
An increasing amount of evidence suggests that elevated PCho levels are related to the transforming properties of the H-Ras oncoprotein. Based on these observations, we have designed an antitumor strategy using choline kinase, the enzyme responsible of PCho production, as a novel target for drug discovery. However, little relationship between this lipid-related pathway and the other two Ras members, N- and K-ras, has been established. Since N- and K-ras are the most frequently mutated ras genes in human tumors, we have analyzed the PC-PLD/ChoK pathway and the sensitivity to ChoK inhibition of all three ras-transformed cells. Here we demonstrate that transformation by the three Ras oncoproteins results in increased levels of PCho to a similar extent, resulting from a similar constitutive increase of ChoK activity. As well, sensitivity to choline kinase inhibitors as antiproliferative drugs is similar in cell lines transformed by each of the three ras oncogenes, being in all cases higher than parental, nontransformed cells. In addition, H, K and N-ras-induced alterations in PC metabolism is discussed. These results indicate that ChoK can be used as a general target for anticancer drug design against Ras-dependent tumorigenesis.
3T3 Cells↗
Rho signals to cell growth and apoptosis.
Ras and Rho GTPases are among the best studied signaling molecules in molecular biology. Essential cellular processes, such as cell growth, lipid metabolism, cytoarchitecture, membrane trafficking, transcriptional regulation, apoptosis, and response to genotoxic agents, are directly modulated by different members of this superfamily of proteins. Not until recently have we begun to understand the physiological implications of Ras and Rho GTPases, linking them to processes such as embryonic development, tissue remodeling, tumorigenesis and metastasis. In this sense, uncontrolled activation, due to overexpression of different members of the Rho family in a variety of tissues, leads to uncontrolled proliferation and invasiveness of human tumors. In this review, an attempt to briefly integrate recent findings in transcriptional regulation by Rho GTPases in the context of carcinogenesis and metastasis as well as apoptosis is made.
Animals↗
Modulation of phospholipase D by hexadecylphosphorylcholine: a putative novel mechanism for its antitumoral activity.
Hexadecylphosphorylcholine (HePC, D-18506, INN: Mitelfosine) belongs to the family of alkylphosphocholines with anticancer activity. Previous reports have related its antitumoral activity to their ability to interfere with phospholipid metabolism. However a clear mechanism of action has not been established yet. We have investigated the effect of HePC on two enzymes recently reported to play a role in cell growth proliferation, phospholipase D (PLD) and choline kinase (ChoK). Our results demonstrate that treatment with HePC induces a rapid stimulation of PLD, that may be achieved by PKC dependent or independent mechanisms, depending on the cell line investigated. Both PLD1 and PLD2 isoenzymes are sensitive to HePC activation. By contrast, no effect was observed by HePC on ChoK, a new target for anticancer drug development. Furthermore, in all cell lines tested, a chronic exposure of the cells to HePC abrogates PLD activation by either phorbol esters or HePC itself with no effect on total cellular PLD levels. This is reflected in a strong inhibition of PLD activity. We suggest that the inhibitory effects on PLD by HePC may be related to its antitumoral action.
3T3 Cells↗
Searching new targets for anticancer drug design: the families of Ras and Rho GTPases and their effectors.
The Ras superfamily of low-molecular-weight GTPases are proteins that, in response to diverse stimuli, control key cellular processes such as cell growth and development, apoptosis, lipid metabolism, cytoarchitecture, membrane trafficking, and transcriptional regulation. More than 100 genes of this superfamily grouped in six subfamilies have been described so far, pointing to the complexities and specificities of their cellular functions. Dysregulation of members of at least two of these families (the Ras and the Rho families) is involved in the events that lead to the uncontrolled proliferation and invasiveness of human tumors. In recent years, the cloning and characterization of downstream effectors for Ras and Rho proteins have given crucial clues to the specific pathways that lead to aberrant cellular growth and ultimately to tumorigenesis. A direct link between the functions of some of these effectors with the appearance of transformed cells and their ability to proliferate and invade surrounding tissues has been made. Accordingly, drugs that specifically alter their functions display antineoplasic properties, and some of these drugs are already under clinical trials. In this review, we survey the progress made in understanding the underlying molecular connections between carcinogenesis and the specific cellular functions elicited by some of these effectors. We also discuss new drugs with antineoplastic or antimetastatic activity that are targeted to specific effectors for Ras or Rho proteins.
Antineoplastic Agents↗
LUMO energy of model compounds of bispyridinium compounds as an index for the inhibition of choline kinase.
Eleven derivatives of 1,1'-[1,2-ethylenebis(benzene-1,4-diylmethylene)]bis(4-pyridinium) dibromides bearing various groups at C-4 of the pyridinium moiety were synthesized and examined for their inhibition of choline kinase (ChoK) and antiproliferative activities. The C-4 substituents include electron-releasing, neutral or electron-withdrawing groups. A one-parameter regression equation has been derived which satisfactorily describes the ex vivo inhibitory potency of ChoK of the title compounds. The electronic effect plays a critical function in the ex vivo inhibition of ChoK although the role of electrostatic interactions could be altered due to a solvation process of both ChoK and ligands.
Choline Kinase↗
Simultaneous tyrosine and serine phosphorylation of STAT3 transcription factor is involved in Rho A GTPase oncogenic transformation.
Stats (signal transducers and activators of transcription) are latent cytoplasmic transcription factors that on a specific stimulus migrate to the nucleus and exert their transcriptional activity. Here we report a novel signaling pathway whereby RhoA can efficiently modulate Stat3 transcriptional activity by inducing its simultaneous tyrosine and serine phosphorylation. Tyrosine phosphorylation is exerted via a member of the Src family of kinases (SrcFK) and JAK2, whereas the JNK pathway mediates serine phosphorylation. Furthermore, cooperation of both tyrosine as well as serine phosphorylation is necessary for full activation of Stat3. Induction of Stat3 activity depends on the effector domain of RhoA and correlates with induction of both Src Kinase-related and JNK activities. Activation of Stat3 has biological implications. Coexpression of an oncogenic version of RhoA along with the wild-type, nontransforming Stat3 gene, significantly enhances its oncogenic activity on human HEK cells, suggesting that Stat3 is an essential component of RhoA-mediated transformation. In keeping with this, dominant negative Stat3 mutants or inhibition of its tyrosine or serine phosphorylation completely abrogate RhoA oncogenic potential. Taken together, these results indicate that Stat3 is an important player in RhoA-mediated oncogenic transformation, which requires simultaneous phosphorylation at both tyrosine and serine residues by specific signaling events triggered by RhoA effectors.
Animals↗
Targeting new anticancer drugs within signalling pathways regulated by the Ras GTPase superfamily (Review).
A dynamic equilibrium or is responsible for the proper function of a living organism. Physiological events regulating proliferation, apoptosis, differentiation, and cell arrest, modulates the correct homeostasis and functionality of all tissues. Cancer is a consequence of a disorder in these sequential events, which results in the alteration of the ratio between cell death, cell differentiation and cell proliferation that ultimately leads to an increase in the number of dysregulated cells. Most of the processes which control the are regulated by signalling pathways, whose components are currently being explored as potential targets for the design of antitumoral drugs. Many in vivo studies have shown that Ras and Rho proteins are key modulators of mitogenic signalling, and are involved in the carcinogenesis of several human tumors. The development of recent drugs that elicit antitumoral activity by blocking some of the Ras and/or Rho effects, is discussed in this review.
Animals↗
Choline kinase: a novel target for antitumor drugs.
Malignant cells are characterized by the accumulation of genetic alterations, which result in the disregulation of signal transduction pathways that control proliferation, differentiation and apoptosis. The identification of the molecular components involved in these aberrant processes is necessary for the development of chemotherapeutic interventions to restore or selectively destroy the transformed cells. Discovery of new chemotherapeutic agents is probably one of the most reliable ways to improve our success against cancer, and intelligent drug design is a key factor to achieve this goal. Thus, the identification of novel targets for anticancer drug discovery is needed. This review provides evidence to support choline kinase as one such target.
Journal Article↗
The Ras family of GTPases in cancer cell invasion.
The ability of tumoral cells to invade surrounding tissues is a prerequisite for metastasis. This is the most life-threatening event of tumor progression, and so research is intensely focused on elucidating the mechanisms responsible for invasion and metastasis. The Ras superfamily of GTPases comprises several subfamilies of small GTP-binding proteins whose functions include the control of proliferation, differentiation, and apoptosis, as well as cytoskeleton organization. The development of metastasis is a multistep process that requires coordinated activation of proliferation, motility, changes in normal cell-to-cell and cell-to-substrate contacts, degradation of extracellular matrix, inhibition of apoptosis, and adaptation to an inappropriate tissue environment. Several members of the Ras superfamily of proteins have been implicated in these processes. The present review summarizes the current knowledge in this field.
Animals↗
Ras protein is involved in the physiological regulation of phospholipase D by platelet derived growth factor.
Lipid-derived metabolites play an important role in the regulation of cell responses to external stimuli, including cell growth control, transformation and apoptosis. Phospholipase D (PLD) is one of the critical elements in the regulation of lipid metabolism and the generation of second messengers, some of them involved in cell growth control. Oncogenic Ras proteins affect the activity of PLD by two alternate mechanisms, involving a positive activation and a feedback negative loop. Here we investigate the involvement of the proto-oncogenic Ras protein in the physiological activation of PLD induced by platelet-derived growth factor (PDGF). Over-expression of the wild type Ras protein or some of its regulatory components, such as Shc or Grb2, induces an amplification of PLD activation by PDGF challenge. Furthermore, blocking the endogenous Ras by expression of the dominant negative mutant, H-Ras-Asn17 completely eliminated the activation of PLD by PDGF. Thus, PDGF requires a complex system for PLD regulation implying the existence of at least two positive regulatory pathways, a Ras-dependent and a PKC-dependent mechanism. These results imply that PLD is an important element in signaling by Ras proteins that is altered after ras-induced transformation.
3T3 Cells↗
Apoptosis induced by Rac GTPase correlates with induction of FasL and ceramides production.
Rho proteins, members of the Ras superfamily of GTPases, are critical elements in signal transduction pathways governing cell proliferation and cell death. Different members of the family of human Rho GTPases, including RhoA, RhoC, and Rac1, participate in the regulation of apoptosis in response to cytokines and serum deprivation in different cell systems. Here, we have characterized the mechanism of apoptosis induced by Rac1 in NIH 3T3 cells. It requires protein synthesis and caspase-3 activity, but it is independent of the release of cytochrome c from mitochondria. Moreover, an increase in mitochondria membrane potential and the production of reactive oxygen species was observed. Rac1-induced apoptosis was related to the simultaneous increase in ceramide production and synthesis of FasL. Generation of FasL may be mediated by transcriptional regulation involving both c-Jun amino terminal kinase as well as nuclear factor-kappa B-dependent signals. None of these signals, ceramides or FasL, was sufficient to induce apoptosis in the parental cell line, NIH 3T3 cells. However, any of them was sufficient to induce apoptosis in the Rac1-expressing cells. Finally, inhibition of FasL signaling drastically reduced apoptosis by Rac1. Thus, Rac1 seems to induce apoptosis by a complex mechanism involving the generation of ceramides and the de novo synthesis of FasL. These results suggest that apoptosis mediated by Rac1 results from a signaling mechanism that involves biochemical and transcriptional events under control of Rac1.
3T3 Cells↗
In vivo antitumor activity of choline kinase inhibitors: a novel target for anticancer drug discovery.
Transformation by some oncogenes is associated with increased activity of choline kinase (ChoK), resulting in elevated constitutive levels of phosphorylcholine, a proposed second messenger required for DNA synthesis induced by growth factors. Here we describe the characterization of ChoK inhibitors with antiproliferative properties against human tumor-derived cell lines. The new molecules were tolerated in mice at doses that showed in vivo antitumor activity against human tumor xenografts derived from HT-29 and A431 cell lines implanted s.c. in nude mice. This first generation of inhibitors provides in vivo evidence that blockade of phosphorylcholine production is a valid strategy for the development of new anticancer agents, opening a new avenue for the development of antitumor drugs with a novel mechanism of action.
Adenocarcinoma↗
Activation of serum response factor by RhoA is mediated by the nuclear factor-kappaB and C/EBP transcription factors.
The activity of the transcription factor NF-kappaB can be modulated by members of the Rho family of small GTPases (Perona, R., Montaner, S., Saniger, L., Sánchez-Pérez, I., Bravo, R., and Lacal, J. C. (1997) Genes Dev. 11, 463-475). Ectopic expression of RhoA, Rac1, and Cdc42Hs proteins induces the translocation of NF-kappaB dimers to the nucleus, triggering the transactivation of the NF-kappaB-dependent promoter from the human immunodeficiency virus. Here, we demonstrate that activation of NF-kappaB by RhoA does not exclusively promote its nuclear translocation and binding to the specific kappaB sequences. NF-kappaB is also involved in the regulation of the transcriptional activity of the c-fos serum response factor (SRF), since the activation of a SRE-dependent promoter by RhoA can be efficiently interfered by the double mutant IkappaBalphaS32A/S36A, an inhibitor of the NF-kappaB activity. We also present evidence that RelA and p50 NF-kappaB subunits cooperate with the transcription factor C/EBPbeta in the transactivation of the 4 x SRE-CAT reporter. Furthermore, RhoA increases the levels of C/EBPbeta protein, facilitating the functional cooperation between NF-kappaB, C/EBPbeta, and SRF proteins. These results strengthen the pivotal importance of the Rho family of small GTPases in signal transduction pathways which modulate gene expression and reveal that NF-kappaB and C/EBPbeta transcription factors are accessory proteins for the RhoA-linked regulation of the activity of the SRF.
Animals↗
Rho-regulated signals induce apoptosis in vitro and in vivo by a p53-independent, but Bcl2 dependent pathway.
Rho proteins are a branch of GTPases that belongs to the Ras superfamily which are critical elements of signal transduction pathways leading to a variety of cellular responses. This family of small GTPases has been involved in diverse biological functions such as cytoskeleton organization, cell growth and transformation, cell motility, migration, metastasis, and responses to stress. We report that several human Rho proteins including Rho A, Rho C and Rac 1, are capable of inducing apoptosis in different cell systems like murine NIH3T3 fibroblasts and the human erythroleukemia K562 cell line. Since K562 cells are devoid of p53, apoptosis induced by Rho in this system is independent of p53. Rho-dependent apoptosis is mediated by the generation of ceramides, and it is drastically inhibited by ectopic expression of Bcl2, both under in vitro and in vivo conditions. Furthermore, the human oncogenes vav and ost that have been shown to function as guanine exchange factors for Rho proteins, were also able to induce apoptosis under similar conditions. Finally, we also report that the levels of endogenous Rho proteins are increased when U937 myeloid leukemia cells are exposed to apoptosis-inducing conditions such as TNF alpha treatment. Furthermore, TNF alpha-induced apoptosis in these cells is inhibited by expression of a dominant negative mutant of Rac 1 but it is not affected by a similar mutant of Rho A. These results suggest that Rho proteins play an important role in the physiological regulation of the apoptotic response to stress-inducing agents.
3T3 Cells↗
Multiple signalling pathways lead to the activation of the nuclear factor kappaB by the Rho family of GTPases.
Members of the Rho family of small GTPases activate the nuclear factor kappaB (NF-kappaB) (Perona, R., Montaner, S., Saniger, L., Sánchez-Pérez, I., Bravo, R., and Lacal, J. C. (1997), Genes & Dev. 11, 463-475). We have investigated whether different members of the family of exchange factors specific for Rho proteins (Dbl family) could activate the transcription factor NF-kappaB and have explored both their specificity under in vivo conditions and the mechanisms involved. Activated forms of Dbl, Ost, and Vav proteins induce NF-kappaB activation. While the activation induced by the Vav oncogen was efficiently inhibited by a dominant negative mutant of Rac1, the corresponding mutant of Cdc42Hs was able to block selectively NF-kappaB activation mediated by Dbl. Finally, mutants of RhoA and Cdc42Hs, but not that of Rac1, inhibited the activation of NF-kappaB by Ost. Thus, under in vivo conditions, different members of the Dbl family are related to specific Rho GTPases for the regulation of NF-kappaB. Activation of NF-kappaB by Rho or Ras proteins is mutually independent. However, there is a link between the NF-kappaB and the c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) cascades since a dominant negative mutant of MEKK1 is able to inhibit NF-kappaB activation induced by Rac1 and Cdc42Hs proteins, but not by RhoA. These results indicate that, in mammalian cells, multiple pathways coexist for the activation of NF-kappaB, some of which are mediated by specific members of the Ras and Rho families of small GTPases.
Animals↗