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ABSTRACT: The aromatic fatty acid phenylacetate (PA) and its analogs have come under intense investigation due to their ability to cause the growth arrest of a variety of neoplasia, including human breast cancer. We have determined that PA and its halide derivative 4-chlorophenylacetate (4-CPA) showed marked antiproliferative activity on 3 of 6 human breast cancer cell lines tested. Interestingly, the 3 cell lines that were growth inhibited by PA and 4-CPA were estrogen receptor (ER) positive (T47-D, MCF-7 and ZR-75-1) whereas those that were little affected by these compounds were ER-negative (MDA-MB-157, MDA-MB-231 and SK-Br-3). Dose response studies indicated that 4-CPA inhibited the growth of the sensitive (ER+) cell lines with a potency 3-4 times that of PA. These findings suggest that there is "cross-talk" between the PA and estrogen signaling pathways such that PA can directly inhibit estrogen-dependent events. This hypothesis was directly tested in vitro using ER+ MCF-7 cells that were stably transfected with a luciferase reporter construct driven by the full length (1745 bp) cyclin D1 promoter (MCF-7-D1). Our experiments with MCF-7-D1 cells indicated that PA and 4-CPA inhibited basal and estrogen-induced reporter gene activity by up to 90%, resulting in almost complete elimination of estrogen-dependent cyclin D1 gene activation. Using a reporter gene construct (ERE(V)-tk-Luc) containing a canonical estrogen response element that was transiently transfected into MCF-7 and MDA-MB-231 cells, we have also demonstrated inhibition of promoter activity by PA and 4-CPA that was directly mediated by blockage of activity through the ERE. Taken together, these findings indicate that PA analogs possess potent antiestrogen properties that may, at least partly, account for their antiproliferative effects on ER+ breast cancer cells. The data suggests a novel mechanism of action that might bypass some of the limitations of conventional antiestrogen therapy.
International Journal of Cancer 10/2001; 93(5):687-92. · 5.44 Impact Factor
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ABSTRACT: Aromatic fatty acids, of which phenylacetate is a prototype, constitute a class of low toxicity drugs with demonstrated antitumor activity in experimental models and in humans. Using in vitro models, we show here a tight correlation between tumor growth arrest by phenylacetate and activation of peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear receptor superfamily. In support are the following observations: (a) the efficacy of phenylacetate as a cytostatic agent was correlated with pre-treatment levels of PPARgamma, as documented using established tumor lines and forced expression models; (b) in responsive tumor cells, PPARgamma expression was up-regulated within 2-9 h of treatment preceding increases in p21waf1, a marker of cell cycle arrest; (c) inhibition of mitogen-activated protein kinase, a negative regulator of PPARgamma, enhanced drug activity; and (d) phenylacetate interacted directly with the ligand-binding site of PPARgamma and activated its transcriptional function. The ability to bind and activate PPARgamma was common to biologically active analogues of phenylacetate and corresponded to their potency as antitumor agents (phenylacetate < phenylbutyrate < p-chloro-phenylacetate < p-iodo-phenylbutyrate), whereas an inactive derivative, phenylacetylglutamine, had no effect on PPARgamma. These findings point to PPARgamma as a novel target in cancer therapy and provide the first identification of ligands that have selective antitumor activity in patients.
Clinical Cancer Research 04/2000; 6(3):933-41. · 7.74 Impact Factor
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ABSTRACT: Although Burkitt's lymphoma (BL) is a readily treated malignancy, recurrences, as well as disease arising in immunosuppressed patients, are notoriously resistant to conventional therapeutic approaches. The EBV is associated with a significant proportion of these lymphomas that evade immune surveillance through decreased expression of both viral and cellular antigens. Increasing the immunogenicity of BL cells may, therefore, represent a potentially beneficial therapeutic maneuver. Using in vitro models of EBV-transformed lymphoblastoid as well as BL cell lines, we demonstrate increased expression of genes coding for HLA class I and EBV latent proteins by the differentiation inducer phenylbutyrate (PB). The aromatic fatty acid also caused cytostasis associated with sustained declines in c-myc expression, a direct antitumor effect that was independent of the EBV status. We conclude, therefore, that differentiation therapy of BL with PB may lead to growth arrest with increased tumor immunogenicity in vivo. The findings may have clinical relevance because the in vitro activity has been observed with PB concentrations that are well tolerated and nonimmunosuppressive in humans, a desirable feature for the different patient populations afflicted with this disease.
Clinical Cancer Research 07/1999; 5(6):1509-16. · 7.74 Impact Factor
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ABSTRACT: The aromatic fatty acids phenylacetate (PA) and phenylbutyrate (PB) are novel antitumour agents currently under clinical evaluation. Their ability to induce tumour differentiation in laboratory models and their low clinical toxicity profile makes them promising candidates for combination with conventional therapies. In the present studies, we characterized the interactions between these aromatic fatty acids and radiation, using as a model cell lines derived from cancers of the prostate, breast, brain and colon. Analysis of the radiation response of the tumour lines using the linear-quadratic model, demonstrated that cellular exposure to pharmacological, non-toxic concentrations of either PA or PB resulted in time-dependent and contrasting changes in radiation response. While drug pretreatment for 24 h reduced radiation sensitivity (significant alterations in both alpha and beta parameters), pre treatment for 72 h significantly increased radiosensitivity (significant alterations in alpha and beta parameters). In replicating tumour cells, these changes were accompanied by a gradual G1-phase arrest. Cytostasis alone, however, could not explain radiosensitization, as similar alterations in radiation response were documented also in non-cycling cells. Modulation of tumour radiobiology by PA and PB was tightly correlated with early rise followed by decline in intracellular glutathione levels and the activity of antioxidant enzymes such as catalase, superoxide dismutase, glutathione reductase, glutathione peroxidase and glutathione S-transferase. Although in vitro findings identify the aromatic fatty acids PA and PB as a new class of non-toxic modulators of radiation response, the antagonistic effect of these compounds on radiation response needs further examination. Our data strongly suggest that for PA or PB to have a role in clinical radiotherapy, appropriate scheduling of combination therapies must take into account their time-dependent effects in order to achieve clinical radiosensitization.
International Journal of Radiation Biology 09/1997; 72(2):211-8. · 2.28 Impact Factor
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ABSTRACT: Phenylacetate (PA) and related aromatic fatty acids constitute a novel class of relatively nontoxic antineoplastic agents. These compounds induce tumor cytostasis and growth inhibition and differentiation of cancer cells, but little is known regarding the molecular events mediating these biological effects. Using human breast carcinoma MCF-7 cells as a model, we show here that PA-induced growth arrest is associated with enhanced expression of the cyclin-dependent kinase inhibitor p21Waf1/Cip1 and dephosphorylation of the retinoblastoma protein (pRB). The induction of p21WAF1/CIP1 mRNA by PA was independent of the cellular p53 status. To directly assess the contribution of p21Waf1/Cip1 to PA-mediated cytostasis, we compared the effects of PA in parental MCF-7 cells and cells expressing reduced levels of p21Waf1/Cip1 protein (clones AS.3 and AS.4), accomplished through constitutive expression of antisense p21Waf1/Cip1 transcripts. In contrast to parental cells, AS.3 and AS.4 cells did not show reduced pRB phosphorylation following PA treatment, indicating that p21Waf1/Cip1 induction by PA is required for dephosphorylation (inactivation) of pRB, a known mediator of cell cycle control. A prominent role for p21Waf1/Cip1 in mediating PA-induced growth arrest was further supported by the demonstration that embryonal fibroblasts derived from a p21WAF1/CIP1 knockout mouse (p21-/- mouse embryonal fibroblasts) did not growth arrest following PA treatment, whereas PA effectively induced p21WAF1/CIP1 mRNA and growth inhibition of the wild-type mouse embryonal fibroblasts. Taken together, our findings strongly support a role for p21Waf1/Cip1 in the PA-mediated inhibition of cell growth.
Cell growth & differentiation: the molecular biology journal of the American Association for Cancer Research 01/1997; 7(12):1609-15.
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ABSTRACT: Phenylacetate and analogs represent a new class of pleiotropic growth regulators that alter tumor cell biology by affecting gene expression at both the transcriptional and post transcriptional levels. Based on these findings, NaPA and NaPB entered clinical trials at the National Cancer Institute. Ongoing phase I studies with NaPA, involving adults with prostate and brain cancer, have confirmed that therapeutic levels can be achieved with no significant toxicities, and provide preliminary evidence for benefit to patients with advanced disease (Thibault et al., submitted).
Advances in experimental medicine and biology 01/1997; 400A:501-5. · 1.09 Impact Factor
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Advances in experimental medicine and biology 01/1997; 400B:825-30. · 1.09 Impact Factor
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ABSTRACT: Phenylacetate and phenylbutyrate, two novel inducers of tumor cytostasis and differentiation, are currently in clinical trials for the treatment of cancer in adults. The purpose of our study was to evaluate the plasma protein-binding characteristics of phenylacetate and phenylbutyrate in the plasma of normal volunteers and that of patients with cancer. Drug plasma protein-binding analysis was examined using three separate devices: a micropartition system and two equilibrium dialysis systems, all of which exhibited similar results. Phenylacetate and phenylbutyrate concentrations were determined by high-performance liquid chromatography. Both drugs exhibited concentration-dependent binding. Our results showed sodium phenylacetate to have a higher free fraction than sodium phenylbutyrate at corresponding concentrations (> 0.442 +/- 0.008 and > 0.188 +/- 0.001, respectively). Plasma pH did not greatly affect protein binding of either drug. As albumin concentration decreased, an increase in free fraction of both drugs was observed, however alpha 1-acid glyco-protein showed no change in free fraction as its concentration increased. Patients with cancer with lower levels of albumin showed an increase in free fraction with both phenylacetate and phenylbutyrate. When phenylacetate and phenylbutyrate were added together in plasma, the free fraction of phenylacetate increased, whereas the phenylbutyrate free fraction slightly decreased. We conclude that phenylacetate and phenylbutyrate have high free fractions that change with varying albumin levels and when both phenylacetate and phenylbutyrate are present together in plasma.
Therapeutic Drug Monitoring 12/1996; 18(6):714-20. · 2.49 Impact Factor
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ABSTRACT: Phenylbutyrate has been shown recently to induce fetal hemoglobin (HbF) production in patients with sickle cell anemia and beta thalassemia. We have now examined related aromatic fatty acids in order to define the range of active structures and identify plausible mechanisms of action. Structure-function analysis revealed that for effective stimulation of HbF in erythroid precursors: (1) the ideal length for the aliphatic side chain is four carbons; (2) oxygen or sulfur substitutions in the carboxylic chain are allowed, as evidenced by the equal or increased activity of phenoxypropionate, benzylthioglycolate, and benzyloxyacetate compared with phenylbutyrate; and (3) blocking the carboxylate group by conversion to the amide form greatly reduces potency. Molecular analysis indicated that the prototype agent, phenylbutyrate, increases HbF production through transcriptional activation of the gamma-globin gene. The latter contains a butyrate responsive promoter known to up-regulate transcription in the presence of short-chain fatty acids of three to five carbons. To determine whether stimulation of an element in this promoter by phenylbutyrate and its analogues might contribute to their mechanism of action, we used a transient expression system involving K562 erythroleukemia cells transfected with a luciferase reporter gene driven by the minimum gamma-globin promoter. Transcriptional activation in this experimental system correlated well with the capacity of an aromatic fatty acid to increase HbF production in erythroid precursors (r = 0.94). Our studies identify potent analogues of phenylbutyrate for the treatment of beta-chain hemoglobinopathies, and suggest that stimulation of a butyrate responsive promoter may be responsible for their activity.
Biochemical Pharmacology 11/1996; 52(8):1227-33. · 4.70 Impact Factor
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ABSTRACT: The prostatic-specific antigen (PSA) is the tumor marker most widely relied upon for the monitoring of patients with prostate cancer. Recently, declines in the serum concentrations of PSA have been advocated as a surrogate marker of tumor response in clinical trials of investigational antitumor agents. We examined the hypothesis that this postulate may not apply to the evaluation of drugs such as phenylacetate, a differentiating agent endowed with mechanisms of action different from those of classic cytotoxic chemotherapy. Using human prostatic carcinoma LNCaP cells as a model, we show that phenylacetate induces PSA production despite inhibition of tumor cell proliferation. Incubation of LNCaP cultures with cytostatic doses of phenylacetate (3-10 mM) resulted in a three- to fourfold increase in PSA secretion per cell. This appears to result from upregulation of PSA gene expression, as indicated by elevated PSA mRNA steady-state levels in treated cells. The increase in PSA production per cell was confirmed in rats bearing subcutaneous LNCaP tumor implants that were treated systemically with phenylacetate. Further comparative studies indicate that upregulation of PSA is common to various differentiation inducers, including all-trans-retinoic acid, 1,25-dihydroxyvitamin D3, and butyrate but is not induced by other antitumor agents of clinical interest such as suramin. We conclude that declines in PSA may be treatment specific and that the exclusive use of this criterion as a marker of disease response may mislead the proper evaluation of differentiating agents in prostate cancer patients.
The Prostate 10/1996; 29(3):177-82. · 3.48 Impact Factor
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ABSTRACT: The aromatic fatty acid phenylacetate and its analogs induce tumor cytostasis and differentiation in experimental models. Although the underlying mechanisms of action are not clear, effects on lipid metabolism are evident. We have now examined whether these compounds, structurally similar to the peroxisome proliferator clofibrate, affect the human peroxisome proliferator-activated receptor (hPPAR), a homolog of the rodent PPAR alpha, a transcriptional factor regulating lipid metabolism and cell growth. Gene transfer experiments showed activation of hPPAR, evident by the increased expression of the reporter gene chloramphenicol acetyltransferase linked to PPAR-response element from either the rat acyl-CoA oxidase or rabbit CYP4A6 genes. The relative potency of tested drugs in the co-transfection assay was: 4-iodophenylbutyrate > 4-chlorophenylbutyrate > clofibrate > phenylbutyrate > naphthylacetate > 2,4-D > 4-chlorophenylacetate > phenylacetate > indoleacetate. Phenylacetylglutamine, in which the carboxylic acid is blocked, was inactive. The ability of the aromatic fatty acids to activate PPAR was confirmed in vivo, as CYP4A mRNA levels increased in hepatocytes of treated rats. Further studies using human prostate carcinoma, melanoma, and glioblastoma cell lines showed a tight correlation between drug-induced cytostasis, increased expression of the endogenous hPPAR, and receptor activation documented in the gene-transfer model. These results identify phenylacetate and its analogs as a new class of aromatic fatty acids capable of activating hPPAR, and suggest that this nuclear receptor may mediate tumor cytostasis induced by these drugs.
Biochemical Pharmacology 09/1996; 52(4):659-67. · 4.70 Impact Factor
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ABSTRACT: The refractoriness of prostate cancer to androgen suppression is the landmark of clinically aggressive disease. In this study, the androgen-dependent LNCaP prostate cancer cells were transfected with the mutated c-Ha-ras gene from the T24 human bladder cancer. The derivative clone overexpressing T24-ras (LNCaP(T24-ras)) proliferated in androgen-depleted medium and showed increased growth. Protein isoprenylation and p21ras farnesylation in LNCaP(T24-ras) cells were tested in the presence of phenylacetate to document a possible relationship with the drug-induced inhibition of cell proliferation. Phenylacetate is a differentiation inducer that down-regulates in vitro the expression of the myc oncogene and activates the human peroxisome proliferator-activated nuclear receptor involved in cell growth regulation. The drug inhibited protein isoprenylation and p21ras farnesylation in LNCaP(T24-ras) cells; IC50 values were 3.1 and 3.3 mM, respectively, compared with controls. The drug reduced the cellular levels of endogenous farnesyl-PP (mean IC50 = 3.5 mM) and inhibited activation of the p21ras downstream target, p42(MAPK)/ERK2. LNCaP(T24-ras) was more sensitive than the parental line to both growth inhibition (mean IC50 = 3.01 and 7.1 mM, respectively) and apoptosis by phenylacetate. Exogenous farnesyl- and geranylgeranyl-PP indeed reduced the effects of the drug on proliferation and apoptosis in LNCaP(T24-ras) cells. In conclusion, the inhibition of protein isoprenylation and p21ras farnesylation by phenylacetate resulted in increased chemosensitivity of the androgen-independent LNCaP(T24-ras) cells compared with LNCaP, and this effect might contribute to the pharmacological activity of the drug.
Molecular Pharmacology 07/1996; 49(6):972-9. · 4.88 Impact Factor
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ABSTRACT: Cytotoxic chemotherapies often give rise to multidrug resistance, which remains a major problem in cancer management. In pursuit of alternative treatments for chemoresistant tumor cells, we tested the response of multidrug-resistant (MDR) tumor cell lines to the aromatic fatty acids phenylacetate (PA) and phenylbutyrate (PB), two differentiation inducers currently in clinical trials. Both compounds induced cytostasis and maturation of multidrug-resistant breast, ovarian, and colon carcinoma cells with no significant effect on cell viability. In contrast to their poor response to doxorubicin, the MDR cells were generally more sensitive to growth arrest by PA and PB than their parental counterparts. The aromatic fatty acids, like the differentiation-inducing aliphatic fatty acid butyrate, up-regulated mdr-1 gene expression. However, while butyrate increased multidrug resistance, PA and PB potentiated the cytotoxic activity of doxorubicin against MDR cells. The latter was associated with time-dependent declines in glutathione levels and in the activity of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase, the antioxidant enzymes implicated in cell resistance to free radical-based therapies. Taken together, our in vitro data indicate that PA and PB, differentiation inducers of the aromatic fatty acid class, may provide an alternative approach to the treatment of MDR tumors.
Clinical Cancer Research 06/1996; 2(5):865-72. · 7.74 Impact Factor
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A Thibault, D Samid,
A C Tompkins,
W D Figg,
M R Cooper,
R J Hohl,
J Trepel,
B Liang,
N Patronas,
D J Venzon,
E Reed,
C E Myers
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ABSTRACT: Lovastatin, an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (the major regulatory enzyme of the mevalonate pathway of cholesterol synthesis), displays antitumor activity in experimental models. We therefore conducted a Phase I trial to characterize the tolerability of lovastatin administered at progressively higher doses to cancer patients. From January 1992 to July 1994, 88 patients with solid tumors (median age, 57 +/- 14 years) were treated p.o. with 7-day courses of lovastatin given monthly at doses ranging from 2 to 45 mg/kg/day. The inhibitory effects of lovastatin were monitored through serum concentrations of cholesterol and ubiquinone, two end products of the mevalonate pathway. Concentrations of lovastatin and its active metabolites were also determined, by bioassay, in the serum of selected patients. Cyclical treatment with lovastatin markedly inhibited the mevalonate pathway, evidenced by reductions in both cholesterol and ubiquinone concentrations, by up to 43 and 49% of pretreatment values, respectively. The effect was transient, however, and its magnitude appeared to be dose independent. Drug concentrations reached up to 3.9 micrometer and were in the range associated with antiproliferative activity in vitro. Myopathy was the dose-limiting toxicity. Other toxicities included nausea, diarrhea, and fatigue. Treatment with ubiquinone was associated with reversal of lovastatin-induced myopathy, and its prophylactic administration prevented the development of this toxicity in a cohort of 56 patients. One minor response was documented in a patient with recurrent high-grade glioma. Lovastatin given p.o. at a dose of 25 mg/kg daily for 7 consecutive days is well tolerated. The occurrence of myopathy, the dose-limiting toxicity, can be prevented by ubiquinone supplementation. To improve on the transient inhibitory activity of this dosing regimen on the mevalonate pathway, alternative schedules based on uninterrupted administration of lovastatin should also be studied.
Clinical Cancer Research 04/1996; 2(3):483-91. · 7.74 Impact Factor
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ABSTRACT: Malignant gliomas, the most common form of primary brain tumors, are highly dependent on the mevalonate (MVA) pathway for the synthesis of lipid moieties critical to cell replication. Human glioblastoma cells were found to be uniquely vulnerable to growth arrest by lovastatin, a competitive inhibitor of the enzyme regulating MVA synthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase. The sodium salt of phenylacetic acid (NaPA), an inhibitor of MVA-pyrophosphate decarboxylase, the enzyme that controls MVA use, acted synergistically with lovastatin to suppress malignant growth. When used at pharmacologically attainable concentrations, the two compounds induced profound cytostasis and loss of malignant properties such as invasiveness and expression of the transforming growth factor-beta 2 gene, coding for a potent immunosuppressive cytokine. Supplementation with exogenous ubiquinone, an end product of the MVA pathway, failed to rescue the cells, suggesting that decreased synthesis of intermediary products are responsible for the antitumor effects observed. In addition to blocking the MVA pathway, lovastatin alone and in combination with NaPA increased the expression of the peroxisome proliferator-activated receptor, a transcription factor implicated in the control of lipid metabolism, cell growth, and differentiation. Our results indicate that targeting lipid metabolism with lovastatin, used alone or in combination with the aromatic fatty acid NaPA, may offer a novel approach to the treatment of malignant gliomas.
Journal of Neurochemistry 03/1996; 66(2):710-6. · 4.06 Impact Factor
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ABSTRACT: The aromatic fatty acid phenylacetate, a common metabolite of phenylalanine, shows promise as a relatively non-toxic drug for cancer treatment. This slowly metabolized fatty acid alters tumor cell lipid metabolism causing, among other effects, inhibition of protein prenylation critical to malignant growth. In pursuit of more potent analogues, we have examined the activity of related compounds against tumor cell lines established from patients with advanced prostatic carcinoma, glioblastomas, and malignant melanoma. Like phenylacetate, derivatives containing alpha-carbon or ring substitutions induced cytostasis and phenotypic reversion at non-toxic concentrations. Potency was correlated with the degree of calculated lipophilicity of the aromatic fatty acid, and the extent of inhibition of protein prenylation. Remarkably, a parallel cytostatic activity was reported in embryonic plant cells, which respond to phenylacetate and its analogues in the same concentration range and the same rank order of lipophilicity. These data suggest that phenylacetate and its analogues may act through common mechanisms to inhibit the growth of vastly divergent, undifferentiated cell types, and provide a basis for the development of new agents for the treatment of human malignancies.
Biochemical Pharmacology 11/1995; 50(8):1273-9. · 4.70 Impact Factor
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ABSTRACT: Alterations in the expression of ras oncogenes are characteristic of a wide variety of human neoplasms. Accumulating evidence has linked elevated ras expression with disease progression and with failure of tumors to respond to conventional therapies, including radiotherapy and certain chemotherapies. These observations led us to investigate the response of ras-transformed cells to the differentiation-inducer phenylacetate (PA). Using gene transfer models, we show that PA caused cytostasis in ras-transformed mesenchymal cells, associated with increased expression of 2',5'-oligoadenylate synthetase, an enzyme implicated in negative growth control. PA also induced phenotypic reversion characterized by loss of anchorage-independent growth, reduced invasiveness and increased expression of collagen alpha type I, a marker of cell differentiation. The anti-tumor activity of PA was observed in cases involving either Ha- or Ki-ras and was independent of the mode of oncogene activation. Interestingly, in contrast to their relative resistance to radiation and doxorubicin, ras-transformed cells were significantly more sensitive to PA than their parental cells. The profound changes in tumor cell and molecular biology were associated with reduced isoprenylation of the ras-encoded p21. Our results indicate that PA can suppress the growth of ras-transformed cells, resistant otherwise to free-radical based therapies, through interference with p21ras isoprenylation, critical to signal transduction and maintenance of the malignant phenotype.
International Journal of Cancer 10/1995; 63(1):124-9. · 5.44 Impact Factor
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ABSTRACT: Differentiation inducers selected for their low cytotoxic and genotoxic potential could be of major value in chemoprevention and maintenance therapy. We focus here on phenylacetate, a naturally occurring plasma component recently shown to affect the growth and differentiation of established neoplasms in experimental models. The ability of phenylacetate to prevent carcinogenesis by the chemotherapeutic hypomethylating drug 5-aza-2'-deoxycytidine (5AzadC) was tested in vitro and in mice. Transient exposure of immortalized, but poorly tumorigenic ras-transformed 4C8 fibroblasts to 5AzadC resulted in neoplastic transformation manifested by loss of contact inhibition of growth, acquired invasiveness, and increased tumorigenicity in athymic mice. The latter was associated with elevation in ras expression and a decline in collagen biosynthesis. These profound phenotypic and molecular changes were prevented by a simultaneous treatment with phenylacetate. Protection from 5AzadC carcinogenesis by phenylacetate was: (a) highly efficient despite DNA hypomethylation by both drugs, (b) free of cytotoxic and genotoxic effects, (c) stable after treatment was discontinued, and (d) reproducible in vivo. Whereas athymic mice bearing 4C8 cells developed fibrosarcomas following a single i.p. injection with 5AzadC, tumor development was significantly inhibited by systemic treatment with nontoxic doses of phenylacetate. Phenylacetate and its precursor suitable for oral administration, phenylbutyrate, may thus represent a new class of chemopreventive agents, the efficacy and safety of which should be further evaluated.
Clinical Cancer Research 09/1995; 1(8):865-71. · 7.74 Impact Factor
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ABSTRACT: Cinnamic acid, a naturally occurring aromatic fatty acid of low toxicity, has a long history of human exposure. We now show that cinnamic acid induces cytostasis and a reversal of malignant properties of human tumor cells in vitro. The concentration causing a 50% reduction of cell proliferation (IC50) ranged from 1 to 4.5 mM in glioblastoma, melanoma, prostate and lung carcinoma cells. Using melanoma cells as a model, we found that cinnamic acid induces cell differentiation as evidenced by morphological changes and increased melanin production. Moreover, treated cells had reduced invasive capacity associated with modulation of expression of genes implicated in tumor metastasis (collagenase type IV, and tissue inhibitor metalloproteinase 2) and immunogenicity (HLA-A3, class-I major histocompatibility antigen). Further molecular analysis indicated that the anti-tumor activity of cinnamic acid may be due in part to the inhibition of protein isoprenylation known to block mitogenic signal transduction. The results presented here identify cinnamic acid as a new member of the aromatic fatty acid class of differentiation-inducers with potential use in cancer intervention.
International Journal of Cancer 08/1995; 62(3):345-50. · 5.44 Impact Factor
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ABSTRACT: The aromatic fatty acids phenylacetate (PA) and phenylbutyrate (PB) induce tumour cell differentiation in experimental models and both are currently in clinical trials. The purpose of this study was to determine the effect of these antitumour agents on the expression of transforming growth factor-alpha (TGF-alpha) in neoplastic cells. Treatment of human melanoma 1011 cultures with either PA or PB caused over 40-fold increase in TGF-alpha biosynthesis and secretion into the media. Whereas elevation in TGF-alpha mRNA steady-state levels became evident within 6-12 h and reached peak quantities the following day, the amounts of its coded protein increased gradually over a period of 5 days of treatment. Further molecular analysis revealed that regulation of TGF-alpha expression occurred at the transcriptional level. In contrast to TGF-alpha, expression of its receptor remained below detectable levels, indicating that an autocrine loop involving this growth factor is unlikely. Interestingly, the increase in TGF-alpha production paralleled drug-induced cytostasis and differentiation defined by morphological changes and increased melanogenesis. Like PA and PB, other differentiation inducers such as all-trans-retinoic acid, dimethyl sulfoxide, and 5-aza-2'-deoxycytidine, all induced TGF-alpha expression in the melanoma cells. The close association between enhanced TGF-alpha production and melanoma cell differentiation suggests that this growth factor, often linked to mitogenesis, may play a novel role in tumour differentiation by PA and PB.
Cytokine 08/1995; 7(5):449-56. · 3.02 Impact Factor
