Polyethylene glycol inhibits intestinal neoplasia and induces epithelial apoptosis in Apc(min) mice

Development of Donor Recipient Chimeric Cells of bone marrow origin as a novel approach for tolerance induction in transplantation

Background

Cell therapies and chimerism-based strategies are currently the most successful approach for tolerance induction in transplantation. This study aimed to establish and characterize novel Donor Recipient Chimeric Ccell (DRCC) therapy of bone marrow (BM) origin presenting donor-recipient phenotype to support tolerance induction.

Methods

Ex vivo fusions of fully MHC-mismatched BM cells from ACI (RT1^a) and Lewis (RT1^l) rats were performed using polyethylene-glycol (PEG). The creation of rat DRCC was tested by flow cytometry (FC), confocal microscopy and PCR. FC characterized DRCC's phenotype (CD3, CD4, CD8, CD45, CD90, CD11b/c, CD45RA, OX-82, or CD4/CD25) and apoptosis, while mixed lymphocyte reaction assessed DRCC's immunogenicity and colony forming unit assay tested DRCC's differentiation and proliferation. DRCC's polyploidy was evaluated using Hoechst33342 staining and COMET assay tested genotoxicity of fusion procedure. ELISA analyzed the secretion of IL-2, IL-4, IL-10, TGFß1, IFNγ and TNFα by DRCC at day 1, 5 and 14 post-fusion. The DRCC's phenotype after long-term culturing was assessed by reverse-transcription PCR.

Results

The chimeric state of DRCC was confirmed. Fusion did not change the expression of hematopoietic markers compared to BM controls. Although an increased number of early and late apoptotic (Annexin V⁺/Sytox blue^- and Annexin V⁺/Sytox blue⁺, respectively) DRCC was detected at 24h post-fusion, the number significantly decreased at day 5 (38.4%±3.1% and 22.6%±2.5%, vs. 28.3%±2.5% and 13.9%±2.6%, respectively, P<0.05). DRCC presented decreased immunogenicity, increased expression of IL-10 and TGFβ1 and proliferative potential comparable to BM controls. The average percentage of tetraploid DRCC was 3.1%±0.2% compared to 0.96%±0.1% in BM controls. The lack of damage to the DRCC's DNA content supported the DRCC's safety. In culture, DRCC maintained proliferation for up to 28 days while preserving hematopoietic profile.

Conclusions

This study confirmed feasibility of DRCC creation via ex vivo PEG mediated fusion. The created DRCC revealed pro-tolerogenic properties indicating potential immunomodulatory effect of DRCC therapy when applied in vivo to support tolerance induction in solid organ and vascularized composite allograft transplantation.

Prevention of colonic neoplasia with polyethylene glycol: A short term randomized placebo-controlled double-blinded trial

Chemoprevention represents an attractive modality against colorectal cancer (CRC) although widespread clinical implementation of promising agents (e.g. aspirin/NSAIDS) have been stymied by both suboptimal efficacy and concerns over toxicity. This highlights the need for better agents. Several groups, including our own, have reported that the over-the-counter laxative polyethylene glycol (PEG) has remarkable efficacy in rodent models of colon carcinogenesis. In this study, we undertook the first randomized human trial to address the role of PEG in prevention of human colonic neoplasia. This was a double-blind, placebo-controlled, three-arm trial where eligible subjects were randomized to 8g PEG-3350 (n = 27) or 17g PEG-3350 (n = 24), or placebo (n = 24; maltodextrin) orally for a duration of six months. Our initial primary endpoint was rectal aberrant crypt foci (ACF) but this was changed during protocol period to rectal mucosal epidermal growth factor receptor (EGFR). Of the 87 patients randomized, 48 completed study primary endpoints and rectal EGFR unchanged PEG treatment. Rectal ACF had a trend suggesting potentially reduction with PEG treatment (pre-post change 1.7 in placebo versus -0.3 in PEG 8+ 17g doses, p = 0.108). Other endpoints (proliferation, apoptosis, expression of SNAIL and E-cadherin), previously noted to be modulated in rodent models, appeared unchanged with PEG treatment in this clinical trial. We conclude that PEG was generally well tolerated with the trial failing to meet primary efficacy endpoints. However, rectal ACFs demonstrated a trend (albeit statistically insignificant) for suppression with PEG. Moreover, all molecular assays including EGFR were unaltered with PEG underscoring issues with lack of translatability of biomarkers from preclinical to clinical trials. This data may provide the impetus for future clinical trials on PEG using more robust biomarkers of chemoprevention.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00828984.

A Way Forward for Cancer Chemoprevention: Think Local

As cells progress through carcinogenesis, the associated exponential expansion of genetic and molecular aberrations and resultant heterogeneity make therapeutic success increasingly unattainable. Therapeutic intervention at early stages of carcinogenesis that occurs within the primary organ and in the face of a lower burden of molecular aberrations, constitutes a basic tenet of cancer chemoprevention, and provides a situation that favors a greater degree of therapeutic efficacy compared with that of advanced cancer. A longstanding barrier to chemoprevention relates to the requirement for essentially no systemic toxicity, and the fact that when large numbers of people are treated, the emergence of systemic toxicity is almost universal. A rational means to address this in fact relates to a second basic tenet of the chemopreventive strategy: the focus of therapeutic intervention is to disrupt a process that is in essence localized to a single organ. Based upon this consideration, a strategy which is based upon local delivery of therapeutics to an at-risk organ will achieve therapeutic efficacy while avoiding systemic delivery and its associated toxicity. This article will review the rationale for undertaking such an approach, describe successful clinical achievements based on this strategy, describe ongoing efforts to expand the impact of this approach, and together will highlight the high impact that this approach has already had on the field as well as its extremely high potential for future impact. Cancer Prev Res; 10(1); 14-35. ©2016 AACR.

Laxative treatment with polyethylene glycol decreases microbial primary bile salt dehydroxylation and lipid metabolism in the intestine of rats

Polyethylene glycol (PEG) is a frequently used osmotic laxative that accelerates gastrointestinal transit. It has remained unclear, however, whether PEG affects intestinal functions. We aimed to determine the effect of PEG treatment on intestinal sterol metabolism. Rats were treated with PEG in drinking water (7%) for 2 wk or left untreated (controls). We studied the enterohepatic circulation of the major bile salt (BS) cholate with a plasma stable isotope dilution technique and determined BS profiles and concentrations in bile, intestinal lumen contents, and feces. We determined the fecal excretion of cholesterol plus its intestinally formed metabolites. Finally, we determined the cytolytic activity of fecal water (a surrogate marker of colorectal cancer risk) and the amount and composition of fecal microbiota. Compared with control rats, PEG treatment increased the pool size (+51%; P < 0.01) and decreased the fractional turnover of cholate (-32%; P < 0.01). PEG did not affect the cholate synthesis rate, corresponding with an unaffected fecal primary BS excretion. PEG reduced fecal excretion of secondary BS and of cholesterol metabolites (each P < 0.01). PEG decreased the cytolytic activity of fecal water [54 (46-62) vs. 87 (85-92)% erythrocyte potassium release in PEG-treated and control rats, respectively; P < 0.01]. PEG treatment increased the contribution of Verrucomicrobia (P < 0.01) and decreased that of Firmicutes (P < 0.01) in fecal flora. We concluded that PEG treatment changes the intestinal bacterial composition, decreases the bacterial dehydroxylation of primary BS and the metabolism of cholesterol, and increases the pool size of the primary BS cholate in rats.

Topical polyethylene glycol as a novel chemopreventive agent for oral cancer via targeting of epidermal growth factor response

Head and neck squamous cell carcinoma (HNSCC) is a major cause of morbidity and mortality underscoring the need for safe and effective chemopreventive strategies. Targeting epidermal growth factor receptor (EGFR) is attractive in that it is an early critical event in HNSCC pathogenesis. However, current agents lack efficacy or have unacceptable toxicity. Several groups have demonstrated that the over-the-counter medication, polyethylene glycol (PEG) has remarkable chemopreventive efficacy against colon carcinogenesis. Importantly, we reported that this effect is mediated through EGFR internalization/degradation. In the current study, we investigated the chemopreventive efficacy of this agent against HNSCC, using both the well validated animal model 4-NQO (4-nitroquinoline 1-oxide) rat model and cell culture with the human HNSCC cell line SCC-25. We demonstrated that daily topical application of 10% PEG-8000 in the oral cavity (tongue and cavity wall) post 4NQO initiation resulted in a significant reduction in tumor burden (both, tumor size and tumors/tumor bearing rat) without any evidence of toxicity. Immunohistochemical studies depicted decreased proliferation (number of Ki67-positive cells) and reduced expression of EGFR and its downstream effectors cyclin D1 in the tongue mucosa of 4NQO-rats treated with PEG. We showed that EGFR was also markedly downregulated in SCC-25 cells by PEG-8000 with a concomitant induction of G1-S phase cell-cycle arrest, which was potentially mediated through upregulated p21(cip1/waf1). In conclusion, we demonstrate, for the first time, that PEG has promising efficacy and safety as a chemopreventive efficacy against oral carcinogenesis.

Higher molecular weight polyethylene glycol increases cell proliferation while improving barrier function in an in vitro colon cancer model

Polyethylene glycol (PEG) has been previously shown to protect against enteric pathogens and prevent colon cancer invasion. To determine if PEG could indeed protect against previously observed pro-invasive effects of commensal E. coli and EPEC, Caco-2 cells grown in an in vitro model of colon cancer were infected with strains of human commensal E. coli or EPEC and treated with 10% PEG 3350, PEG 8000, and PEG 20,000, respectively. At 24 hours after infection, MMP-1 and MMP-13 activities, cell cluster thickness, depth of invasion, and proliferation were determined using standard molecular biology techniques and advanced imaging. We found that higher molecular weight PEG, especially PEG 8000 and 20,000, regardless of bacterial infection, increased proliferation and depth of invasion although a decrease in cellular density and MMP-1 activity was also noted. Maximum proliferation and depth of invasion of Caco-2 cells was observed in scaffolds treated with a combination of commensal E. coli strain, HS4 and PEG 8000. In conclusion, we found that PEG 8000 increased cell proliferation and led to the preservation of cell density in cells treated with commensal bacteria. This is important, because the preservation of a proliferative response in colon cancer results in a more chemo-responsive tumor.

Polyethylene glycol-mediated colorectal cancer chemoprevention: roles of epidermal growth factor receptor and Snail

Polyethylene glycol (PEG) is a clinically widely used agent with profound chemopreventive properties in experimental colon carcinogenesis. We reported previously that Snail/beta-catenin signaling may mediate the suppression of epithelial proliferation by PEG, although the upstream events remain unclear. We report herein the role of epidermal growth factor receptor (EGFR), a known mediator of Snail and overexpressed in approximately 80% of human colorectal cancers, on PEG-mediated antiproliferative and hence antineoplastic effects in azoxymethane (AOM) rats and HT-29 colon cancer cells. AOM rats were randomized to either standard diet or one with 10% PEG-3350 and euthanized 8 weeks later. The colonic samples were subjected to immunohistochemical or Western blot analyses. PEG decreased mucosal EGFR by 60% (P < 0.001). Similar PEG effects were obtained in HT-29 cells. PEG suppressed EGFR protein via lysosmal degradation with no change in mRNA levels. To show that EGFR antagonism per se was responsible for the antiproliferative effect, we inhibited EGFR by either pretreating cells with gefitinib or stably transfecting with EGFR-short hairpin RNA and measured the effect of PEG on proliferation. In either case, PEG effect was blunted, suggesting a vital role of EGFR. Flow cytometric analysis revealed that EGFR-short hairpin RNA cells, besides having reduced membrane EGFR, also expressed low Snail levels (40%), corroborating a strong association. Furthermore, in EGFR silenced cells, PEG effect on EGFR or Snail was muted, similar to that on proliferation. In conclusion, we show that EGFR is the proximate membrane signaling molecule through which PEG initiates antiproliferative activity with Snail/beta-catenin pathway playing the central intermediary function.

Induction of multinucleated cells and apoptosis in the PC-3 prostate cancer cell line by low concentrations of polyethylene glycol 1000

Polyethylene glycol (PEG) has been reported to inhibit the development of colonic lesions in carcinogen-treated rats when administered orally. However, the precise mechanism for the chemopreventive activity of PEG remains largely elusive. Based on a characteristic feature of PEG as a 'fusogen', we investigated its potential as a chemotherapeutic agent through the induction of multinucleated cell formation and apoptosis induction in PC-3 prostate cancer cells. When PC-3 cells were treated with 0.5 and 1.0% PEG 1000, multinucleated cells were induced at a frequency of 8.4 and 13%, respectively, 36 h after PEG treatment under high cell density (1 x 10(6) cells in 100 microL PEG solution) in vitro. Although abnormality of cell cycle progression was not evident in PEG-treated PC-3 cells, multinucleated cells substantially disappeared at around 38 h due to apoptosis. In contrast, no apparent growth suppression was observed when PC-3 cells were exposed to up to 1.0% PEG at a much lower cell density, namely under ordinary culture conditions. Furthermore, injection of 0.5% PEG solution in vivo into PC-3 xenografts implanted in BALB/c-nu/nu male mice significantly suppressed tumor growth compared to phosphate-buffered saline injection. Multinucleated TdT-mediated dUTP-biotin nick end-labeling (TUNEL)-positive cells were observed inside the PEG-injected tumors. PEG was here demonstrated to have anticell proliferation and antitumor effects via induction of apoptosis, possibly by cell fusion. PEG injection therapy could therefore be adopted as an alternative chemotherapeutic strategy for localized prostate cancers, including those that become refractory to androgen-deprivation therapy.

Polyethylene glycol enhances colonic barrier function and ameliorates experimental colitis in rats

OBJECTIVE

Polyethylene glycol (PEG) has been suggested to protect against pathogen colonization by improving colonic barrier function. We aimed to establish whether PEG 4000 affects colonic barrier function and the development of colitis induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) in rats.

MATERIALS AND METHODS

PEG was included in the drinking water for a period of 48 h before intracolonic administration of TNBS.

RESULTS AND DISCUSSION

PEG increased colonic surface hydrophobicity and diminished luminal bacterial load. Moreover, PEG markedly reduced mucosal damage and inflammation induced by TNBS. This protection effect appeared to be independent of its laxative properties since the laxatives mannitol or senna extracts had no effect on TNBS colitis. Using everted colonic sacs, pretreatment with PEG produced a lasting reduction in epithelial permeability to mannitol and dextran-70 K that correlated with decreased surface hydrophobicity.

CONCLUSION

Our results suggest that the protective effect of PEG on TNBS colitis is associated with reinforcement of the epithelial barrier.

Polyethylene glycol and prevalence of colorectal adenomas

BACKGROUND AND AIM

Dietary polyethylene glycol (PEG) is extraordinarily potent in the chemoprevention of experimental colon carcinogenesis. PEG is used to treat constipation in France and in the USA. French laxatives include Forlax (PEG4000), Movicol and Transipeg (PEG3350), and Idrocol (pluronic F68). This study tests the hypothesis that use of a PEG-based laxative might reduce the prevalence of colorectal tumors.

METHODS

In this population-based study, consecutive patients attending for routine total colonoscopy were enrolled during four months by the gastroenterologists of Indre-et-Loire. They were asked if they had previously taken a laxative or a NSAID. Age, gender, previous polyps, family history of colorectal cancer, constipation, digestive symptoms were also recorded. Tumors found during colonoscopy were categorized histologically.

RESULTS

Records from 1165 patients fulfilled the inclusion criteria, 607 women and 498 men, mean age 58.3. Among those, 813 had no tumor, 329 had adenomas, and 23 had carcinomas. In a univariate analysis, older age, male gender, lack of digestive symptom, and previous polyps were more common in patients with colorectal tumors. In contrast, previous Forlax intake was more common in tumor-free patients (odds ratio (OR) any use/no use, 0.52; 95% confidence interval, 0.27-0.94). More people used Forlax, which contains a higher dose of PEG than the other PEG-laxatives, whose ORs were smaller than one, but did not reach significance. In multivariate analysis, older age and male gender were associated with higher risk, and NSAIDs use with lower risk, of colorectal tumors.

CONCLUSION

Forlax users had a halved risk of colorectal tumors in univariate analysis, which suggests that PEG may prevent carcinogenesis.

Chemoprevention of colon carcinogenesis by polyethylene glycol: suppression of epithelial proliferation via modulation of SNAIL/beta-catenin signaling

Polyethylene glycol (PEG) is one of the most potent chemopreventive agents against colorectal cancer; however, the mechanisms remain largely unexplored. In this study, we assessed the ability of PEG to target cyclin D1-beta-catenin-mediated hyperproliferation in the azoxymethane-treated rat model and the human colorectal cancer cell line, HT-29. Azoxymethane-treated rats were randomized to AIN-76A diet alone or supplemented with 5% PEG-8000. After 30 weeks, animals were euthanized and biopsies of aberrant crypt foci and uninvolved crypts were subjected to immunohistochemical and immunoblot analyses. PEG markedly suppressed both early and late markers of azoxymethane-induced colon carcinogenesis (fractal dimension by 80%, aberrant crypt foci by 64%, and tumors by 74%). In both azoxymethane-treated rats and HT-29 cells treated with 5% PEG-3350 for 24 hours, PEG decreased proliferation (45% and 52%, respectively) and cyclin D1 (78% and 56%, respectively). Because beta-catenin is the major regulator of cyclin D1 in colorectal cancer, we used the T-cell factor (Tcf)-TOPFLASH reporter assay to show that PEG markedly inhibited beta-catenin transcriptional activity. PEG did not alter total beta-catenin expression but rather its nuclear localization, leading us to assess E-cadherin expression (a major determinant of beta-catenin subcellular localization), which was increased by 73% and 71% in the azoxymethane-rat and HT-29 cells, respectively. We therefore investigated the effect of PEG treatment on levels of the negative regulator of E-cadherin, SNAIL, and observed a 50% and 75% decrease, respectively. In conclusion, we show, for the first time, a molecular mechanism through which PEG imparts its antiproliferative and hence profound chemopreventive effect.

Role of polyamines in arginine-dependent colon carcinogenesis in Apc(Min) (/+) mice

We evaluated the role of polyamines in arginine-dependent intestinal tumorigenesis in Apc(Min) (/+) mice. Arginine is a substrate for ornithine synthesis and thus can influence polyamine production. Supplementing the diet with arginine increased intestinal and colonic polyamine levels and colonic carcinogenesis. Inhibiting polyamine synthesis with D,L-alpha-diflouromethylornithine (DFMO) decreased small intestinal and colonic polyamine pools. In mice provided basal diet, but not when supplemented with arginine, DFMO decreased small intestinal tumor number and burden, and increased intestinal apoptosis. In mice provided supplemental arginine in the diet, DFMO induced late apoptosis and decreased tumorigenesis in the colon. DFMO slightly reduced tumor incidence, number, and size while significantly decreasing tumor burden and grade. These changes in colon tumorigenesis did not occur in mice not provided supplemental arginine. Our study indicates that polyamines play unique roles in intestinal and colonic carcinogenesis in Apc(Min) (/+) mice. Inhibition of polyamine synthesis suppresses the arginine-dependent risk of colon tumorigenesis, resulting in apoptosis induction and decreased tumorigenesis, in this murine model.

Polyethylene glycol, unique among laxatives, suppresses aberrant crypt foci, by elimination of cells

OBJECTIVE

Polyethylene glycol (PEG), an osmotic laxative, is a potent inhibitor of colon cancer in rats. In a search for the underling mechanisms, the hypothesis that fecal bulking and moisture decrease colon carcinogenesis was tested. We also investigated the PEG effects on crypt cells in vivo.

MATERIAL AND METHODS

Fischer 344 rats (n=272) were injected with the colon carcinogen, azoxymethane. They were then randomized to a standard AIN76 diet containing one of 19 laxative agents (5% w/w in most cases): PEG 8000 and other PEG-like compounds, carboxymethylcellulose, polyvinylpyrrolidone, sodium polyacrylate, calcium polycarbophil, karaya gum, psyllium, mannitol, sorbitol, lactulose, propylene glycol, magnesium hydroxide, sodium phosphate, bisacodyl, docusate, and paraffin oil. Aberrant crypt foci (ACF) and fecal values were measured blindly after a 30-day treatment regimen. Proliferation, apoptosis, and the removal of cells from crypts were studied in control and PEG-fed rats using various methods, including TUNEL and fluorescein dextran labeling.

RESULTS

PEG 8000 reduced the number of ACF 9-fold in rats (p<0.001). The other PEGs and magnesium hydroxide modestly suppressed ACF, but not the other laxatives. ACF number did not correlate with fecal weight or moisture. PEG doubled the apoptotic bodies per crypt (p<0.05), increased proliferation by 25-50% (p<0.05) and strikingly increased (>40-fold) a fecal marker of epitheliolysis in the gut (p<0.001). PEG normalized the percentage of fluorescein dextran labeled cells on the top of ACF (p<0.001).

CONCLUSIONS

Among laxatives, only PEG afforded potent chemoprevention. PEG protection was not due to increased fecal bulking, but in all likelihood to the elimination of cells from precancerous lesions.

Polyethylene glycol reduces inflammation and aberrant crypt foci in carcinogen-initiated rats

Polyethylene glycol 8000 inhibits the formation of tumors and of aberrant crypt foci (ACF) in carcinogen-initiated rats. We asked: is the inhibition associated with a reduction of colonic inflammation and an increase in colonic cell permeability? Twenty-eight, male F 344 rats were divided into two groups, 10 control animals and 18 animals initiated with azoxymethane. Nine of the rats in the carcinogen-initiated group were given a diet with 5% PEG 8000 in an AIN-93 based, high fat diet. The other nine, and the control group received the diet without the addition of PEG. Nine weeks later, the rats receiving the diet containing PEG had a 43% reduction in ACF (P<0.001) compared with the carcinogen-initiated rats on the control diet, a result confirming earlier observations that PEG inhibits colon carcinogenesis. The animals receiving the diet containing PEG also had a 10-fold reduction in fecal granulocyte marker protein (GMP) (P<0.001) compared with both the carcinogen-treated and the control animals. PEG reduced inflammation below the levels of carcinogen-treated and of untreated animals. Fecal water from the rats receiving PEG did not reduce transepithelial resistance of, or manitol flux through, human Caco-cells grown as monolayers in vitro. PEG may reduce colon carcinogenesis through a mechanism involving colonic inflammation.