RESUMEN
Carnitine is known for its essential role in intermediary metabolism. In vitro studies suggest that its antioxidant and anti-inflammatory properties are potentially beneficial toward cancer prevention. This study tested effects of carnitine on the development of colon cancer in vivo using 2 murine models: azoxymethane (AOM) treatment as a model of carcinogen-induced colon cancer and a genetically induced model using Apc (Min/+) mice. AOM and Apc (Min/+) mice divided into dietary groups varying in lipid content, with or without carnitine supplementation (0.08%). AOM-exposed mice on a high butterfat diet had significantly increased aberrant crypts (ACF) (9.3 ± 0.88 vs. 6.3 ± 0.65), and macroscopic tumors (3.8 ± 0.95 vs. 2.0 ± 0.25) compared to mice on a control diet. In AOM mice fed the high butterfat diet, carnitine supplementation inhibited ACF (4.9 ± 0.7 vs. 9.3 ± 0.88, P < 0.001), crypt multiciplicity (1.6 ± 0.08 vs. 1.92 ± 0.1, P < 0.01) and tumors (1.5 ± 0.38 vs. 3.8 ± 0.95, P < 0.001). Carnitine supplementation resulted in significantly increased tissue carnitine and acylcarnitine levels. Carnitine inhibited the development of precancerous lesions and macroscopic colonic tumors in AOM-treated mice. However, carnitine did not exert protective effects on intestinal tumors in Apc (Min/+) mice.
Asunto(s)
Anticarcinógenos/farmacología , Carnitina/farmacología , Transformación Celular Neoplásica/efectos de los fármacos , Neoplasias del Colon/prevención & control , Animales , Azoximetano , Carnitina/análisis , Carnitina O-Acetiltransferasa/análisis , Carnitina O-Acetiltransferasa/metabolismo , Neoplasias del Colon/etiología , Neoplasias del Colon/patología , Dieta , Modelos Animales de Enfermedad , Genes APC , Intestinos/química , Intestinos/enzimología , Masculino , Ratones , Ratones Endogámicos C57BL , MutaciónRESUMEN
There is a well-documented association of matrix metalloproteinase-9 (MMP-9) and receptor Notch-1 overexpression in colon cancer. We recently showed that MMP-9 is also upregulated in colitis, where it modulates tissue damage and goblet cell differentiation via proteolytic cleavage of Notch-1. In this study, we investigated whether MMP-9 is critical for colitis-associated colon cancer (CAC). Mice that are wild type (WT) or MMP-9 nullizygous (MMP-9(-/-)) were used for in vivo studies and the human enterocyte cell line Caco2-BBE was used for in vitro studies. CAC was induced in mice using an established carcinogenesis protocol that involves exposure to azoxymethane followed by treatment with dextran sodium sulfate. MMP-9(-/-) mice exhibited increased susceptibility to CAC relative to WT mice. Elevations in tumor multiplicity, size, and mortality were associated with increased proliferation and decreased apoptosis. Tumors formed in MMP-9(-/-) mice exhibited expression of p21(WAF1/Cip1) and increased expression of beta-catenin relative to WT mice. In vitro studies of MMP-9 overexpression showed increased Notch-1 activation with a reciprocal decrease in beta-catenin. Notch and beta-catenin/Wnt signaling have crucial roles in determining differentiation and carcinogenesis in gut epithelia. Despite being a mediator of proinflammatory responses in colitis, MMP-9 plays a protective role and acts as a tumor suppressor in CAC by modulating Notch-1 activation, thereby resulting in activation of p21(WAF1/Cip1) and suppression of beta-catenin.
Asunto(s)
Colitis/enzimología , Neoplasias del Colon/enzimología , Metaloproteinasa 9 de la Matriz/fisiología , Animales , Apoptosis/fisiología , Células CACO-2 , Procesos de Crecimiento Celular/fisiología , Colitis/genética , Colitis/metabolismo , Colitis/patología , Neoplasias del Colon/genética , Neoplasias del Colon/metabolismo , Neoplasias del Colon/patología , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/biosíntesis , Ciclooxigenasa 2/biosíntesis , Modelos Animales de Enfermedad , Femenino , Humanos , Masculino , Metaloproteinasa 9 de la Matriz/genética , Metaloproteinasa 9 de la Matriz/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , FN-kappa B/metabolismo , Óxido Nítrico Sintasa de Tipo II/biosíntesis , Transfección , beta Catenina/metabolismoRESUMEN
OBJECTIVE: Epidemiologic studies support an association between diet and the incidence of colorectal cancer. Butyrate, a short-chain fatty acid present in dietary fiber and dairy products, is a potential anticarcinogenic compound. We previously showed that carnitine can enhance the bioavailability of butyrate in vivo. In the present study, we evaluated the effects of butyrate alone and in combination with carnitine on colon cancer cells in vitro, examining proliferation and apoptosis and the molecular mechanisms by which these nutrients may inhibit colon cancer. METHODS: Caco-2 cells, a well-established cell model, were incubated with butyrate (2.5-20mM) with or without carnitine (10mM) for various incubation periods. Proliferation was measured by incorporation of (3)H-thymidine, and apoptosis was detected using flow cytometry, and then confirmed by analyzing the presence of single-strand DNA breaks typical of apoptotic cells. Prostaglandin E(2) production was assayed and Bcl-2 and cyclo-oxygenase-2 expressions were examined by western blotting. RESULTS: Butyrate and carnitine inhibited Caco-2 cell proliferation (P<0.05) and induced apoptosis (P<0.05). Prostaglandin E(2) production was decreased in treated Caco-2 cells. At the molecular level, the expression of proapoptotic Bax and Bak proteins were increased in cells incubated with butyrate and carnitine, whereas expression of antiapoptotic Bcl-x(L) was decreased. Cyclo-oxygenase-2 expression was decreased in cells incubated with butyrate and carnitine. CONCLUSIONS: Butyrate and carnitine inhibit human colon carcinoma cell proliferation and induce apoptosis in human colon carcinoma cells. This is accompanied by an appreciable alteration of the Bax-to-Bcl-x(L) and Bak-to-Bcl-x(L) ratios in favor of apoptosis. This study provides a scientific rationale to study the effects of carnitine and butyrate in colon cancer in vivo.
Asunto(s)
Adenocarcinoma/tratamiento farmacológico , Antineoplásicos/uso terapéutico , Butiratos/uso terapéutico , Carnitina/uso terapéutico , Colon/efectos de los fármacos , Neoplasias del Colon/tratamiento farmacológico , Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Butiratos/farmacología , Células CACO-2 , Carnitina/farmacología , Proliferación Celular/efectos de los fármacos , Ciclooxigenasa 2/metabolismo , Roturas del ADN/efectos de los fármacos , Dinoprostona/antagonistas & inhibidores , Quimioterapia Combinada , Humanos , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Timidina/metabolismo , Proteína Destructora del Antagonista Homólogo bcl-2/metabolismo , Proteína X Asociada a bcl-2/metabolismoRESUMEN
BACKGROUND: The expression of P-glycoprotein (Pgp) is intimately associated with cancer development. In order to explore the therapeutic value of Pgp as a target for chemotherapy, we studied the effect of PSC 833 (PSC), a potent inhibitor of Pgp, on 1,2-dimethylhydrazine (1,2-DMH)-initiated colorectal carcinogenesis in rats. MATERIALS AND METHODS: Male Fischer 344 rats, initiated with 1,2-DMH coupled with partial hepatectomy, were exposed to dietary 1% orotic acid for 22 weeks. They were then fed either the AIN93G basal diet (BD) or BD containing PSC (a daily dose of 15 mg/kg body weight) for 35 weeks. RESULTS: PSC significantly inhibited colorectal tumor multiplicity by 53% and tumor burden by 74%. PSC-mediated inhibition was evident in tumors as small as 2 mm in diameter and remained effective throughout the course of tumor growth. Histological assessment showed that PSC significantly inhibited tumor progression to colorectal adenocarcinoma by 63%. CONCLUSION: Collectively, this study indicates that PSC inhibited experimental colorectal carcinogenesis initiated with 1,2-DMH in rats.
Asunto(s)
1,2-Dimetilhidrazina/antagonistas & inhibidores , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/antagonistas & inhibidores , Adenocarcinoma/prevención & control , Neoplasias Colorrectales/prevención & control , Ciclosporinas/farmacología , Adenocarcinoma/inducido químicamente , Animales , Peso Corporal/efectos de los fármacos , Neoplasias Colorrectales/inducido químicamente , Ingestión de Alimentos/efectos de los fármacos , Masculino , Ratas , Ratas Endogámicas F344RESUMEN
Studies in our laboratory on the role of P-glycoprotein (Pgp, coded by mdr1 gene) have led to the hypothesis that over-expression of Pgp is closely associated with the development of cancer. It was conceived therefore that inhibitors of Pgp should inhibit the development of cancer. We have reported that PSC833 (PSC), a potent inhibitor of Pgp, inhibits the development of liver cancer in rats. Similarly, based on the intrinsic over-expression of Pgp in experimental mammary carcinogenesis, we studied the effect of PSC on N-methyl-N-nitrosourea induced mammary cancer in female Sprague-Dawley rats. The study indicates that PSC at daily dietary doses of 15 (PSC15) and 30 mg/kg (PSC30) body wt resulted in dose-dependent inhibition of the incidence as well as the growth of mammary tumors. Compared with controls, PSC15 and PSC30 inhibited: (i) mean tumor multiplicity by 32 and 67%, (ii) median tumor burden by 46 and 93% and (iii) incidence of ulcerated tumors by 40 and 82%, respectively. Most remarkably, PSC delayed median tumor incidence by 8 weeks, and exerted a 100% inhibitory effect on the incidence of large tumors, 4 cm(3) and greater. In all the cases, although the inhibitory effect of PSC was evident at both doses, only PSC30 exhibited statistical significance. A possible compounding effect that was also observed in PSC30-treated rats was a decrease in body weight gain not attributed to diminished food consumption. All in all, consistent with recent reports, which have demonstrated inhibition of cancer development by compromising Pgp function, this study introduces a novel role for Pgp in breast cancer and potentially an unexplored therapeutic approach in treating the disease.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/antagonistas & inhibidores , Antineoplásicos/farmacología , Ciclosporinas/farmacología , Neoplasias Mamarias Experimentales/tratamiento farmacológico , Animales , Carcinógenos/farmacología , Femenino , Metilnitrosourea/farmacología , RatasRESUMEN
We report a serendipitous finding of urinary calculi in rats fed a semi-synthetic basal diet. This observation was made during ongoing studies to evaluate the inhibitory effect of PSC 833, a potent inhibitor of P-glycoprotein, on development of tumors in rodent tumor model systems. A large number of specific-pathogen-free (SPF) female Sprague-Dawley and SPF male Fischer 344 rats being fed the diet were euthanized when it became evident clinically that they were uremic. At necropsy, the renal pelvis, ureters, and urinary bladder contained numerous calculi. The presence of urinary calculi was determined to be related to the source of a Food Chemical Codex grade of choline bitartrate. Rats being fed the same basal diet containing the United States Pharmacopia grade of choline bitartrate failed to develop urinary calculi. Interestingly, rats treated with the P-glycoprotein inhibitor were at significantly reduced risk of developing urinary calculi. This finding highlights how something seemingly innocuous as a minor dietary constituent can have a profound impact and, thereby, affect experimental outcome.
Asunto(s)
Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/antagonistas & inhibidores , Ciclosporinas/administración & dosificación , Alimentos Formulados/efectos adversos , Enfermedades de los Roedores/etiología , Enfermedades de los Roedores/prevención & control , Cálculos Urinarios/veterinaria , Animales , Colina/administración & dosificación , Colina/efectos adversos , Femenino , Masculino , Ratas , Ratas Endogámicas F344 , Ratas Sprague-Dawley , Organismos Libres de Patógenos Específicos , Cálculos Urinarios/etiología , Cálculos Urinarios/prevención & controlRESUMEN
The present study explores the hypothesis that over-expression of P-glycoprotein (Pgp, product of mdr1) is intimately associated with liver cancer development and therefore inhibitors of Pgp should inhibit the development of liver cancer. Accordingly, we determined the effect of PSC833 (PSC), a potent inhibitor of Pgp, on experimental liver carcinogenesis in rats. To study the effects of PSC on liver cancer development, a daily dose of 30 mg PSC/kg body wt (PSC30) was chosen based on an initial dose-response experiment. Accordingly in experiment 1, PSC30 was fed to rats initiated by 1,2-dimethylhydrazine coupled with two-thirds partial hepatectomy and promoted for 22 weeks with 1% dietary orotic acid. Surprisingly, in contrast to our earlier observations in rats without hepatic nodules, in rats bearing hepatic nodules, PSC30 was found to be toxic. Because of this, PSC30 diet was discontinued after 5 weeks and the rats were transferred to basal diet (BD). The rats were killed 10 and 25 weeks thereafter. Cumulative results indicate that PSC30 exhibited a 40% decrease in the incidence of hepatocellular carcinoma (HCC; 15 of 18 in the BD group compared with eight of 17 in the PSC30 group; P = 0.08) coupled with significant reduction of tumor multiplicity (54%; P < 0.05) and tumor burden (61%; P < 0.005) compared with controls. In experiment 2, 15 mg PSC/kg body wt (PSC15) was fed for 20 weeks to rats similarly initiated and promoted for 35 weeks. PSC15 inhibited the incidence of HCC by 75% (four of four in the BD group compared to one of four in the PSC30 group; P = 0.15) and significantly reduced tumor burden by 55% (P < 0.05). The lack of statistical significance of inhibition on tumor incidence reflects the small sample size. Taken together the results indicate a possible intrinsic role for Pgp in liver cancer development and introduce another promising unexplored therapeutic approach in liver cancer treatment.