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Kumarasamy V, Atroosh WM, Anbazhagan D, Abdalla MMI, Azzani M. Association of Blastocystis hominis with colorectal cancer: A systematic review of in vitro and in vivo evidences. World J Gastrointest Oncol 2022; 14:734-745. [PMID: 35321272 PMCID: PMC8919012 DOI: 10.4251/wjgo.v14.i3.734] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 07/16/2021] [Accepted: 02/23/2022] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Recently, there have been several findings that showed intestinal colonisation of Blastocystis hominis (Blastocystis) as a risk factor to the worsening of colorectal cancer (CRC). However, studies have shown controversial results in the pathogenicity of Blastocystis.
AIM To review systematically the evidence available on the association between CRC and Blastocystis and the prevalence of Blastocystis in CRC patients and to investigate cytopathic and immunological effects of Blastocystis in in vitro and in vivo studies.
METHODS PRISMA guidelines were utilised in conducting this systematic review. Original articles published before February 2, 2020 were included. PubMed, Science Direct, Scopus and Google scholar databases were searched. Manual searching was carried out to find articles missed during the online search.
RESULTS Out of 12 studies selected for this systematic review, seven studies confirmed the prevalence of Blastocystis and found it to be between 2%-28% in CRC patients, whereby subtype 1 and subtype 3 were predominantly seen. A total of four studies employing in vitro human colorectal carcinoma cell line study models showed significant cytopathic and immunological effects of Blastocystis. In addition, one in vivo experimental animal model study showed that there was a significant effect of infection with Blastocystis on exacerbation of colorectal carcinogenesis.
CONCLUSION Blastocystis is a commonly identified microorganism in CRC patients. These studies have provided supportive data that Blastocystis could exacerbate existing CRC via alteration in host immune response and increased oxidative damage. Future studies of CRC and Blastocystis should attempt to determine the various stages of CRC that are most likely to be associated with Blastocystis and its relationship with other intestinal bacteria.
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Affiliation(s)
- Vinoth Kumarasamy
- Department of Microbiology and Parasitology, Faculty of Medicine, Bioscience and Nursing, MAHSA University, Jenjarom 42610, Selangor, Malaysia
- Department of Preclinical Sciences, Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Kajang 43000, Selangor, Malaysia
| | - Wahib Mohammed Atroosh
- Department of Parasitology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Wilayah Persekutuan, Malaysia
- Department of Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Aden, Aden 00, Yemen
| | - Deepa Anbazhagan
- Department of Microbiology and Parasitology, Faculty of Medicine, Bioscience and Nursing, MAHSA University, Jenjarom 42610, Selangor, Malaysia
| | | | - Meram Azzani
- Department of Community Medicine, Faculty of Medicine, Bioscience and Nursing, MAHSA University, Jenjarom 42610, Selangor, Malaysia
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Aboulthana WM, Ibrahim NES, Osman NM, Seif MM, Hassan AK, Youssef AM, El-Feky AM, Madboli AA. Evaluation of the Biological Efficiency of Silver Nanoparticles Biosynthesized Using Croton tiglium L. Seeds Extract against Azoxymethane Induced Colon Cancer in Rats. Asian Pac J Cancer Prev 2020; 21:1369-1389. [PMID: 32458646 PMCID: PMC7541879 DOI: 10.31557/apjcp.2020.21.5.1369] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Colorectal cancer (CRC) is considered as the most common type of gastrointestinal cancers. Chemotherapy became limited due to the adverse side effects. Therefore, the most effective Croton tiglium extract was selected to be incorporated by silver nanoparticles (Ag-NPs) then evaluated against colon cancer induced by azoxymethane (AOM) in rats. METHODS Different hematological and biochemical measurements were quantified in addition to markers of oxidative stress. Specific tumor and inflammatory markers were assayed. Colonic tissues were examined histopathologically in addition to immunohistochemistry (IHC). Native proteins and isoenzymes patterns were electrophoretically assayed beside expression of Tumor Protein P53 (TP53) and Adenomatous Polyposis Coli (APC) genes in colonic tissues. RESULTS It was found that AOM caused significant (P≤0.05) elevation in the hematological and biochemical measurements. C. tiglium nano-extract restored these measurements to normalcy. Tumor and inflammatory markers elevated significantly (P≤0.05) in sera of AOM induced colon cancer group in addition to increasing peroxidation products with decline in antioxidant enzymes activities in colon tissues. Nano-extract restored these measurements to normalcy in post-treated group. Histopathological study revealed that nano-extract minimized severity of inflammatory reactions in all nano-extract treated groups and prevented anti-Keratin 20 antibody expression in post-treated group. The lowest similarity index (SI%) values were noticed with electrophoretic protein (SI=71.43%), lipid (SI=0.00%) and calcium (SI=75.00%) moieties of protein patterns, catalase (SI=85.71%), peroxidase (SI=85.71%), α-esterase (SI=50.00%) and β-esterase (SI=50.00%) isoenzymes in colon cancer group. Furthermore, AOM altered the relative quantities of total native bands. The nano-extract prevented the alterations that occurred qualitatively in nano-extract post-treated group and quantitatively in all nano-extract treated groups. Levels of TP53 and APC gene expression increased in AOM injected group and nano-extract restored their levels to normalcy in the post-treated group. CONCLUSION C. tiglium nano-extract exhibited ameliorative effect against the biochemical and molecular alterations induced by AOM in nano-extract post-treated group.
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Affiliation(s)
- Wael Mahmoud Aboulthana
- Biochemistry Department, Genetic Engineering and Biotechnology Division, National Research Centre, Dokki, Giza, Egypt.
- For Correspondence:
| | - Noha El-Sayed Ibrahim
- Microbial Biotechnology Department, Genetic Engineering and Biotechnology Division, National Research Centre, Dokki, Giza, Egypt.
| | - Noha Mohamed Osman
- Cell Biology Department, Genetic Engineering and Biotechnology Division, National Research Centre, Dokki, Giza, Egypt.
| | - Mohamed Mahmoud Seif
- Toxicology and Food contaminants, Food Industry and Nutrition Division, National Research Center, Dokki, Giza, Egypt.
| | - Amgad Kamal Hassan
- Biochemistry Department, Genetic Engineering and Biotechnology Division, National Research Centre, Dokki, Giza, Egypt.
| | | | - Amal Mostafa El-Feky
- Pharmacognosy Department, Pharmaceutical and Drug Industries Research Division, National Research Centre, Dokki, Giza, Egypt.
| | - A A Madboli
- Animal Reproduction and Artificial Insemination Department, Veterinary Division, National Research Centre, Dokki, Giza, Egypt .
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Kagemoto K, Okamoto K, Takaoka T, Sato Y, Kitamura S, Kimura T, Sogabe M, Miyamoto H, Muguruma N, Tsuneyama K, Takayama T. Detection of aberrant crypt foci with image-enhanced endoscopy. Endosc Int Open 2018; 6:E924-E933. [PMID: 30123821 PMCID: PMC6095220 DOI: 10.1055/a-0621-8794] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 04/11/2018] [Indexed: 01/01/2023] Open
Abstract
Background and study aims Conventional detection of aberrant crypt foci (ACF) with dye-spraying and magnifying observation is labor- and skill-intensive. We performed a prospective non-inferiority study to investigate the utility of image-enhanced endoscopy (IEE) for detection of ACF. Patients and methods Patients with a history of colorectal neoplasm were eligible. The number of ACF in the lower rectum was counted first using IEE magnification with narrow-band imaging (NBI) or blue-laser imaging (BLI), and subsequently using the methylene blue method. The primary endpoint was the ACF detection rate with IEE, i. e., the number of ACF detected with IEE relative to the number of ACF detected with methylene blue. The secondary endpoints were bowel preparation time, ACF detection time, and the detection rate with NBI or BLI. Results A total of 40 patients were enrolled (NBI 20 and BLI 20). The overall detection rate for ACF with IEE was 81.7 % (503/616; 95 %CI 78.8 - 84.6 %), meeting the primary endpoint. The detection rate for ACF with BLI (84.9 %, 258/304) was significantly higher than with NBI (78.5 %, 245/312; P < 0.05). Both bowel preparation time and ACF detection time were significantly shorter with IEE versus the methylene blue method ( P < 0.01, respectively). The detection rates for dysplastic and non-dysplastic ACF with IEE were 84.4 % (27/32) and 80.3 % (469/584), respectively. Conclusion IEE is able to detect ACF during colonoscopy with sensitivity non-inferior to that of the conventional methylene blue method. IEE is simpler than the methylene blue method and is therefore a potentially useful new tool for ACF detection.
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Affiliation(s)
- Kaizo Kagemoto
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Koichi Okamoto
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Toshi Takaoka
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Yasushi Sato
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Shinji Kitamura
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Tetsuo Kimura
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Masahiro Sogabe
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Hiroshi Miyamoto
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Naoki Muguruma
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Koichi Tsuneyama
- Department of Pathology and Laboratory Medicine, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan
| | - Tetsuji Takayama
- Department of Gastroenterology and Oncology, Institute of Biomedical Sciences, Tokushima University Graduate School, Japan,Corresponding author Tetsuji Takayama MD, PhD Department of Gastroenterology and OncologyInstitute of Biomedical SciencesTokushima University Graduate School3-18-15, Kuramoto-choTokushima City, 770-8503 Japan+81-88-633-9235
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Wali RK, Bianchi L, Kupfer S, De La Cruz M, Jovanovic B, Weber C, Goldberg MJ, Rodriguez LM, Bergan R, Rubin D, Tull MB, Richmond E, Parker B, Khan S, Roy HK. Prevention of colonic neoplasia with polyethylene glycol: A short term randomized placebo-controlled double-blinded trial. PLoS One 2018; 13:e0193544. [PMID: 29617381 PMCID: PMC5884487 DOI: 10.1371/journal.pone.0193544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 01/02/2018] [Indexed: 11/18/2022] Open
Abstract
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.
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Affiliation(s)
- Ramesh K. Wali
- Department of Medicine, Boston University Medical Center, Boston, MA, United States of America
| | - Laura Bianchi
- Department of Medicine, NorthShore University HealthSystem, Evanston, IL, United States of America
| | - Sonia Kupfer
- Department of Medicine, University of Chicago, Chicago, IL, United States of America
| | - Mart De La Cruz
- Department of Medicine, Boston University Medical Center, Boston, MA, United States of America
| | - Borko Jovanovic
- Department of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Christopher Weber
- Department of Medicine, University of Chicago, Chicago, IL, United States of America
| | - Michael J. Goldberg
- Department of Medicine, NorthShore University HealthSystem, Evanston, IL, United States of America
| | - L. M. Rodriguez
- National Cancer Institute, Rockville, MD, United States of America
| | - Raymond Bergan
- Department of Medicine, Oregon Health & Science University, Portland, OR, United States of America
| | - David Rubin
- Department of Medicine, University of Chicago, Chicago, IL, United States of America
| | - Mary Beth Tull
- Department of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Ellen Richmond
- National Cancer Institute, Rockville, MD, United States of America
| | - Beth Parker
- Department of Medicine, Boston University Medical Center, Boston, MA, United States of America
| | - Seema Khan
- Department of Medicine, University of Chicago, Chicago, IL, United States of America
| | - Hemant K. Roy
- Department of Medicine, Boston University Medical Center, Boston, MA, United States of America
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Son YS, Ullah HMA, Elfadl AK, Ghim SG, Chung MJ, Kim YD, Lee EJ, Kang KK, Jeong KS. Inhibition of Formation of Azoxymethane-induced Colonic Aberrant Crypt Foci in Rats by Edible Green Algae Capsosiphon fulvescens and Brown Algae Hizikia fusiforme. In Vivo 2018; 32:101-108. [PMID: 29275305 PMCID: PMC5892625 DOI: 10.21873/invivo.11210] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 10/21/2017] [Accepted: 10/26/2017] [Indexed: 12/14/2022]
Abstract
Capsosiphon fulvescens (green seaweed) and Hizikia fusiforme (brown seaweed) are marine algae consumed as food supplements, especially in Japan, China and Korea, and are considered traditional medicinal tonics for certain ailments. The aim of this study was to investigate the possible inhibitory effects of dietary C. fulvescens and H. fusiforme on azoxymethane (AOM)-induced colorectal cancer (CRC) in rats. F344 male rats (5 weeks, 150 g) were divided into six groups as follows. Group 1: Injected with normal saline solution and fed control diet (untreated control). Group 2: Injected with AOM and fed control diet (treated control). Group 3: Injected with AOM and fed 1% C. fulvescens diet. Group 4: Injected with AOM and fed 2% C. fulvescens diet. Group 5: Injected with AOM and fed 2% H. fusiforme diet. Group 6: Injected with AOM and fed 6% H. fusiforme diet. Test animals received subcutaneous injections of AOM (15 mg/1 ml/kg body weight) once a week for 2 weeks to induce aberrant crypt foci (ACF) in treated control and experimental groups. We evaluated the effects of dietary C. fulvescens and H. fusiforme at two different dose levels: 1 and 2% C. fulvescens, and 2 and 6% H. fusiforme, on colonic carcinogenesis by AOM in rats. Our results suggest that body weights were not significantly different amongst groups. We found that feeding C. fulvescens and H. fusiforme with a control diet significantly (p<0.05) inhibited the development of ACF in experimental groups. C. fulvescens and H. fusiforme in food also significantly (p<0.05) reduced the proliferating cell nuclear antigen labeling index in the colonic tissues of experimental groups. These results demonstrate the chemopreventive potential of C. fulvescens and H. fusiforme against CRC in an AOM-induced rats.
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Affiliation(s)
- Young-Sook Son
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - H M Arif Ullah
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Ahmed K Elfadl
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Soong-Gu Ghim
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Myung-Jin Chung
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Yong Deuk Kim
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Eun-Joo Lee
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Kyung-Ku Kang
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
| | - Kyu-Shik Jeong
- College of Veterinary Medicine and Stem Cell Therapeutic Research Institute, Kyungpook National University, Daegu, Republic of Korea
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Fujii T, Sakai E, Takahashi H, Yamada E, Ohkubo H, Higurashi T, Nakajima A. The distribution of human rectal aberrant crypt foci and criteria for defining the counting area. Oncol Lett 2017; 13:4501-4504. [PMID: 28599450 DOI: 10.3892/ol.2017.6003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 03/29/2017] [Indexed: 12/18/2022] Open
Abstract
Aberrant crypt foci (ACF) are considered as a useful surrogate biomarker for colorectal cancer, although their biological significance still remains controversial. We conducted this study to clarify whether differences in the ACF counting area might have led to the discrepancies in the ACF counts among previous reports. A endoscopist proficient in ACF counting performed high-magnification chromoscopic colonoscopy in 45 subjects and investigated the distribution of ACF in four bowel segments (middle Houston valve to the dentate line and distal rectum 0-5, 5-10 and 10-15 cm). We also investigated whether the patient physique might affect the distance from the middle Houston valve to the dentate line. The prevalence of ACF was 84% and most of the ACF (170/210, 81%) were located in the bowel segment from the middle Houston valve to the dentate line. The number of ACF was significantly correlated with the bowel segment in which the counting was performed: Dentate line to the middle Houston valve and distal rectum within 0-15 cm (r=0.94, P<0.001). The patient physique did not affect the distance from the middle Houston valve to the dentate line. In conclusion, the definition of the ACF counting area may not affect the results of ACF counting.
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Affiliation(s)
- Tetsuro Fujii
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Kanagawa 236-0004, Japan
| | - Eiji Sakai
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Kanagawa 236-0004, Japan
| | - Hirokazu Takahashi
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Kanagawa 236-0004, Japan
| | - Eiji Yamada
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Kanagawa 236-0004, Japan
| | - Hidenori Ohkubo
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Kanagawa 236-0004, Japan
| | - Takuma Higurashi
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Kanagawa 236-0004, Japan
| | - Atsushi Nakajima
- Department of Gastroenterology and Hepatology, Yokohama City University School of Medicine, Yokohama, Kanagawa 236-0004, Japan
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Ku S, Park MS, Ji GE, You HJ. Review on Bifidobacterium bifidum BGN4: Functionality and Nutraceutical Applications as a Probiotic Microorganism. Int J Mol Sci 2016; 17:ijms17091544. [PMID: 27649150 PMCID: PMC5037818 DOI: 10.3390/ijms17091544] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/01/2016] [Accepted: 09/08/2016] [Indexed: 01/20/2023] Open
Abstract
Bifidobacterium bifidum BGN4 is a probiotic strain that has been used as a major ingredient to produce nutraceutical products and as a dairy starter since 2000. The various bio-functional effects and potential for industrial application of B. bifidum BGN4 has been characterized and proven by in vitro (i.e., phytochemical bio-catalysis, cell adhesion and anti-carcinogenic effects on cell lines, and immunomodulatory effects on immune cells), in vivo (i.e., suppressed allergic responses in mouse model and anti-inflammatory bowel disease), and clinical studies (eczema in infants and adults with irritable bowel syndrome). Recently, the investigation of the genome sequencing was finished and this data potentially clarifies the biochemical characteristics of B. bifidum BGN4 that possibly illustrate its nutraceutical functionality. However, further systematic research should be continued to gain insight for academic and industrial applications so that the use of B. bifidum BGN4 could be expanded to result in greater benefit. This review deals with multiple studies on B. bifidum BGN4 to offer a greater understanding as a probiotic microorganism available in functional food ingredients. In particular, this work considers the potential for commercial application, physiological characterization and exploitation of B. bifidum BGN4 as a whole.
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Affiliation(s)
- Seockmo Ku
- Department of Food and Nutrition, Research Institute of Human Ecology, Seoul National University, Seoul 151-742, Korea.
- Laboratory of Renewable Resources Engineering, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907-2022, USA.
| | - Myeong Soo Park
- Department of Hotel Culinary Arts, Yeonsung University, Anyang 430-749, Korea.
| | - Geun Eog Ji
- Department of Food and Nutrition, Research Institute of Human Ecology, Seoul National University, Seoul 151-742, Korea.
- Research Center, BIFIDO Co., Ltd., Hongcheon 250-804, Korea.
| | - Hyun Ju You
- Department of Food and Nutrition, Research Institute of Human Ecology, Seoul National University, Seoul 151-742, Korea.
- Institute of Health and Environment, Graduate School of Public Health, Seoul National University, Seoul 151-742, Korea.
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Preventive Effects of Cocoa and Cocoa Antioxidants in Colon Cancer. Diseases 2016; 4:diseases4010006. [PMID: 28933386 PMCID: PMC5456306 DOI: 10.3390/diseases4010006] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 01/14/2016] [Accepted: 01/15/2016] [Indexed: 01/22/2023] Open
Abstract
Colorectal cancer is one of the main causes of cancer-related mortality in the developed world. Carcinogenesis is a multistage process conventionally defined by the initiation, promotion and progression stages. Natural polyphenolic compounds can act as highly effective antioxidant and chemo-preventive agents able to interfere at the three stages of cancer. Cocoa has been demonstrated to counteract oxidative stress and to have a potential capacity to interact with multiple carcinogenic pathways involved in inflammation, proliferation and apoptosis of initiated and malignant cells. Therefore, restriction of oxidative stress and/or prevention or delayed progression of cancer stages by cocoa antioxidant compounds has gained interest as an effective approach in colorectal cancer prevention. In this review, we look over different in vitro and in vivo studies that have identified potential targets and mechanisms whereby cocoa and their flavonoids could interfere with colonic cancer. In addition, evidence from human studies is also illustrated.
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B-RAF mutation and accumulated gene methylation in aberrant crypt foci (ACF), sessile serrated adenoma/polyp (SSA/P) and cancer in SSA/P. Br J Cancer 2014; 112:403-12. [PMID: 25314065 PMCID: PMC4453443 DOI: 10.1038/bjc.2014.545] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 09/17/2014] [Accepted: 09/20/2014] [Indexed: 01/27/2023] Open
Abstract
Background: Sessile serrated adenomas/polyps (SSA/Ps) are a putative precursor of colon cancer with microsatellite instability (MSI). However, the developmental mechanism of SSA/P remains unknown. We performed genetic analysis and genome-wide DNA methylation analysis in aberrant crypt foci (ACF), SSA/P, and cancer in SSA/P specimens to show a close association between ACF and the SSA/P-cancer sequence. We also evaluated the prevalence and number of ACF in SSA/P patients. Methods: ACF in the right-side colon were observed in 36 patients with SSA/Ps alone, 2 with cancers in SSA/P, and 20 normal subjects and biopsied under magnifying endoscopy. B-RAF mutation and MSI were analysed by PCR–restriction fragment length polymorphism (RFLP) and PCR–SSCP, respectively, in 15 ACF, 20 SSA/P, and 2 cancer specimens. DNA methylation array analysis of seven ACF, seven SSA/P, and two cancer in SSA/P specimens was performed using the microarray-based integrated analysis of methylation by isochizomers (MIAMI) method. Results: B-RAF mutations were frequently detected in ACF, SSA/P, and cancer in SSA/P tissues. The number of methylated genes increased significantly in the order of ACF<SSA/P<cancer. The most commonly methylated genes in SSA/P were PQLC1, HDHD3, RASL10B, FLI1, GJA3, and SLC26A2. Some of these genes were methylated in ACF, whereas all genes were methylated in cancers. Immunohistochemistry revealed their silenced expression. Microsatellite instability and MLH1 methylation were observed only in cancer. The prevalence and number of ACF were significantly higher in SSA/P patients than in normal subjects. A significant correlation was seen between the numbers of SSA/P and ACF in SSA/P patients. Conclusions: Our results suggest that ACF are precursor lesions of the SSA/P-cancer sequence in patients with SSA/P, where ACF arise by B-RAF mutation and methylation of some of the six identified genes and develop into SSA/Ps through accumulated methylation of these genes.
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Freire P, Figueiredo P, Cardoso R, Manuel Donato M, Ferreira M, Mendes S, Silva MR, Cipriano MA, Ferreira AM, Vasconcelos H, Portela F, Sofia C. Predictive value of rectal aberrant crypt foci for intraepithelial neoplasia in ulcerative colitis - a cross-sectional study. Scand J Gastroenterol 2014; 49:1219-29. [PMID: 25157637 DOI: 10.3109/00365521.2014.951390] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Ulcerative colitis (UC) is associated with an increased risk of colorectal cancer (CRC). Aberrant crypt foci (ACF) are important biomarkers of sporadic CRC risk. Their correlation with the risk of intraepithelial neoplasia (IN) in UC remains unclear. AIMS To assess whether ACF are a risk factor for IN in long-standing UC and to investigate any correlation between the clinico-epidemiological characteristics and prevalence/number of ACF in these patients. METHODS Seventy-six patients with long-standing UC were prospectively screened by colonoscopy with chromoendoscopy-guided endomicroscopy. ACF were sought in the lower rectum. RESULTS Eight INs were detected in seven (9.2%) patients. The ACF prevalence and mean number were 60.5% and 2.4 ± 2.8, respectively. The number of ACF was independently associated with the risk of having IN (odds ratio = 1.338; 95% confidence interval 1.030-1.738). ACF number revealed a good calibration (area under the receiver operating characteristic curve = 0.829) and discriminative ability (p = 0.205, Hosmer-Lemeshow test) for the prediction of synchronous IN. Patients with ≥3 ACF have a significantly higher prevalence of IN than patients with <3 ACF (22.6% vs. 0%, p = 0.001). Using this cut-off value, the performance of ACF in predicting the presence of IN was as follows: sensitivity = 100%, specificity = 65.2%, positive predictive value = 22.6%, and negative predictive value = 100%. Age >40 years, family history of CRC, and increased body mass index (BMI) were associated with a significantly higher number of ACF. CONCLUSION Long-standing UC patients with ≥3 ACF have a significantly higher likelihood of having IN. Age >40 years, family history of CRC, and increased BMI have significant positive associations with the number of ACF.
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Affiliation(s)
- Paulo Freire
- Department of Gastroenterology , Centro Hospitalar e Universitário de Coimbra , Coimbra , Portugal
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Sakai E, Nakajima A, Kaneda A. Accumulation of aberrant DNA methylation during colorectal cancer development. World J Gastroenterol 2014; 20:978-987. [PMID: 24574770 PMCID: PMC3921549 DOI: 10.3748/wjg.v20.i4.978] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 11/12/2013] [Accepted: 12/13/2013] [Indexed: 02/06/2023] Open
Abstract
Despite the recent advances in the therapeutic modalities, colorectal cancer (CRC) remains to be one of the most common causes of cancer-related death. CRC arises through accumulation of multiple genetic and epigenetic alterations that transform normal colonic epithelium into adenocarcinomas. Among crucial roles of epigenetic alterations, gene silencing by aberrant DNA methylation of promoter regions is one of the most important epigenetic mechanisms. Recent comprehensive methylation analyses on genome-wide scale revealed that sporadic CRC can be classified into distinct epigenotypes. Each epigenotype cooperates with specific genetic alterations, suggesting that they represent different molecular carcinogenic pathways. Precursor lesions of CRC, such as conventional and serrated adenomas, already show similar methylation accumulation to CRC, and can therefore be classified into those epigenotypes of CRC. In addition, specific DNA methylation already occurs in the normal colonic mucosa, which might be utilized for prediction of the personal CRC risk. DNA methylation is suggested to occur at an earlier stage than carcinoma formation, and may predict the molecular basis for future development of CRC. Here, we review DNA methylation and CRC classification, and discuss the possible clinical usefulness of DNA methylation as biomarkers for the diagnosis, prediction of the prognosis and the response to therapy of CRC.
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Ramos S, Goya L, Martín MA. Antioxidative Stress Actions of Cocoa in Colonic Cancer. Cancer 2014. [DOI: 10.1016/b978-0-12-405205-5.00020-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
AIM Aberrant crypt foci (ACFs) are clusters of colonic crypts that can be identified after staining and that have a different behaviour than the surrounding crypts. They have been hypothesized to be the potential precursors of colonic neoplastic lesions. Since they are detectable in vivo with endoscopic stains, they have been proposed as early biomarkers for colonic carcinogenesis. Our aim was to examine the literature regarding the role of ACFs in the pathogenesis of colorectal cancer (CRC). METHOD An intensive PubMed search was performed with the following terms: aberrant crypt foci, colorectal cancer, biomarker, carcinogenesis. RESULTS Aberrant crypt foci have a variable prevalence and little is known about their natural history. They can be classified as hyperplastic or dysplastic. There is evidence that supports their role as preneoplastic lesions and features detectable by chromoendoscopy have been related to CRC risk. Moreover, ACFs have been shown to harbour genetic and epigenetic alterations common in adenomas and CRC. However, contradictory results have been obtained and difficulties in endoscopic detection and characterization have been described in large-scale studies. CONCLUSION Despite the inconsistencies in ACF detection and characterization, several genetic and epigenetic changes common in both ACFs and CRC have been verified throughout the studies. This evidence is increasingly strong and it grows along with progress in the knowledge of carcinogenesis molecular pathways. Clinical application of ACFs as an intermediate endpoint for colorectal carcinogenesis is under development and a deeper knowledge of cancer mechanisms is needed before it can be applied or discarded.
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Affiliation(s)
- M Lopez-Ceron
- Department of Gastroenterology, Institut de Malalties Digestives i Metabòliques, Hospital Clínic, Barcelona, Spain
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Anderson JC, Swede H, Rustagi T, Protiva P, Pleau D, Brenner BM, Rajan TV, Heinen CD, Levine JB, Rosenberg DW. Aberrant crypt foci as predictors of colorectal neoplasia on repeat colonoscopy. Cancer Causes Control 2011; 23:355-61. [PMID: 22187142 DOI: 10.1007/s10552-011-9884-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 12/07/2011] [Indexed: 12/27/2022]
Abstract
OBJECTIVE To estimate the risk for colorectal neoplasia detected on repeat colonoscopy in relation to aberrant crypt foci (ACF) frequency reported during the previous baseline examination. METHODS From July 2003 until December 2008, patients had a colonoscopy with an ACF study using a magnifying colonoscope. The distal 20 cm section of colon was sprayed with Methylene Blue to ascertain the ACF frequency, the independent variable. Patients were categorized into low and high ACF count using the median as the cut point. Data collected from consenting patients included age, gender, height, weight, ethnicity, smoking history, family history of colorectal cancer (CRC), and personal history of colorectal neoplasia. A follow-up colonoscopy was performed at an interval as dictated by clinical surveillance guidelines. The main outcome was surveillance detected advanced colorectal neoplasia (SDAN) detected on repeat colonoscopy. Logistic Regression was used to calculate risk of SDAN on repeat colonoscopy in relation to baseline ACF count. RESULTS 74 patients had a baseline ACF exam and a repeat surveillance colonoscopy. The median ACF was six and thus a high ACF count was >6 ACF and a low ACF count was ≤6 ACF. Patients diagnosed with SDAN were more likely to have had a high ACF number at baseline compared to patients without these lesions at follow-up (adjusted odds ratio = 12.27; 95% confidence interval: 2.00-75.25) controlling for age, sex, smoking, history of prior adenoma, family history of colon cancer, obesity, and time interval to surveillance exam. A sub analysis of our results demonstrated that this relationship was observed in 48 patients who were undergoing a surveillance colonoscopy for a previous adenoma and not those receiving surveillance for a family history of neoplasia. CONCLUSIONS Increased number of ACF in the distal colorectum was independently associated with substantial risk for future advanced neoplasia. This relationship was observed in patients undergoing surveillance for previous adenomas. Thus, ACF may serve as potential biomarkers in patients with adenomas to help identify patients who may need additional surveillance.
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Affiliation(s)
- Joseph C Anderson
- Carole and Ray Neag Comprehensive Cancer Center, University of Connecticut Health Center, Farmington, CT 06030-1845, USA.
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Sakai E, Takahashi H, Kato S, Uchiyama T, Hosono K, Endo H, Maeda S, Yoneda M, Taguri M, Nakajima A. Investigation of the prevalence and number of aberrant crypt foci associated with human colorectal neoplasm. Cancer Epidemiol Biomarkers Prev 2011; 20:1918-24. [PMID: 21750169 DOI: 10.1158/1055-9965.epi-11-0104] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Aberrant crypt foci (ACF) are considered to be useful as surrogate biomarker for colorectal cancer (CRC), but the biological significance of ACF remains controversial. We attempted to investigate the relationship between the presence of ACF and human colorectal carcinogenesis using a relatively large sample size. METHODS We carried out high-magnification chromoscopic colonoscopy to identify ACFs in 861 subjects undergoing a diagnostic endoscopy at the Yokohama City University Hospital. The present study compared the prevalence and number of ACFs in three subject groups (normal subjects, adenoma cases, and CRC cases). The correlations between the demographic and behavioral characteristics of the subjects and the prevalence of ACFs were also assessed. RESULTS The prevalence of ACF was 64%, 88%, and 95%, and the mean number of ACF was 3.6, 6.2, and 10.1, in normal subjects, adenoma cases, and CRC cases, respectively. When differences in the prevalence and number of ACFs among age- and sex-stratified subject groups were examined, significant stepwise increments from normal subjects to adenoma cases to CRC cases were apparent (P < 0.001). Moreover, an age- and sex-adjusted multiple logistic regression analysis revealed that smoking and alcohol habits had a synergistic effect, increasing the prevalence of ACFs as well as the risk of CRC (P < 0.001). CONCLUSIONS These results suggested that ACF may serve as a reliable surrogate biomarker for human colorectal carcinogenesis. IMPACT The use of ACF as an endpoint may enable the size, duration, and cost of CRC chemoprevention studies to be reduced.
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Affiliation(s)
- Eiji Sakai
- Gastroenterology Division, Yokohama City University School of Medicine, 3-9 Fuku-ura, Kanazawa-ku, Yokohama, 236-0004 Japan
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Takayama T, Nagashima H, Maeda M, Nojiri S, Hirayama M, Nakano Y, Takahashi Y, Sato Y, Sekikawa H, Mori M, Sonoda T, Kimura T, Kato J, Niitsu Y. Randomized double-blind trial of sulindac and etodolac to eradicate aberrant crypt foci and to prevent sporadic colorectal polyps. Clin Cancer Res 2011; 17:3803-11. [PMID: 21385928 DOI: 10.1158/1078-0432.ccr-10-2395] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
PURPOSE On the basis of the results of our preliminary trial suggesting that aberrant crypt foci (ACF) could be eradicated by short-term administration of sulindac, in the present study, we explored the feasibility of using ACF as surrogate markers for chemoprevention of colorectal cancer. EXPERIMENTAL DESIGN Randomly assigned to sulindac (300 mg daily), etodolac (400 mg daily), and placebo groups were 189 subjects without polyps or who had undergone polypectomy. Drugs were administered for 2 months. ACF in the rectal region were counted by magnifying endoscopy. Occurrence of polyps was evaluated at 12 months. A planned interim analysis was conducted. RESULTS ACF number at 2 months was significantly suppressed in the sulindac group (P = 0.0075), but not in the etodolac group (P = 0.73). In the sulindac group, the numbers of adenomas plus hyperplastic polyps (total polyps) and adenomas at 12 months were significantly (P = 0.02) and marginally (P = 0.064) lower, respectively, in comparison with the placebo group; no such difference was observed in the etodolac group. In analysis of only polypectomized subjects, the numbers of total polyps and adenomas in the sulindac group were even more markedly lower, with P values of 0.014 and 0.034, respectively. A similar tendency was confirmed by analyses of the incidence of polyps at 12 months. Suppression rates of total polyps and adenomas in ACF responders to sulindac were significantly greater than in nonresponders. In all groups, compliance was more than 90% and no intolerable adverse effects were observed. CONCLUSIONS ACF may be useful as surrogate lesions for chemoprevention of colorectal cancer.
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Affiliation(s)
- Tetsuji Takayama
- Department of Gastroenterology and Oncology, Institutes of Health Biosciences, University of Tokushima Graduate School, Tokushima, Japan
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Kim J, Rami P, O'Toole J, Llor X, Carroll RE, Benya RV. Extent of prevalence and size of flat neoplasms in a heterogeneous population undergoing routine colorectal cancer screening. Colorectal Dis 2010; 12:471-6. [PMID: 19298579 DOI: 10.1111/j.1463-1318.2009.01822.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND The importance of identifying flat colorectal neoplasms is increasingly appreciated, although the extent of prevalence of these lesions in a general population is not known. OBJECTIVE To determine the extent of prevalence of flat neoplasms in a diverse population undergoing routine endoscopic screening for colorectal cancer. DESIGN Patients referred to the Colorectal Cancer Screening Clinic over a 12-month period (n = 642). RESULTS The patient population was 56% African American and 21% Caucasian; with a mean age of 59 + or - 9 years. Flat neoplasms were detected in 5.5% of all patients, similar to that reported elsewhere, with extent of prevalence being similar regardless of gender or race. Average size of flat neoplasms was of 2.8 + or - 2.3 mm (range 1-20 mm). However, there was no evidence of advanced pathology in any of the flat neoplasms identified. CONCLUSIONS Flat neoplasms are common but may not be associated with advanced pathology in a population undergoing routine screening.
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Affiliation(s)
- J Kim
- Cancer Center and Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA
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Roy HK, Turzhitsky V, Kim Y, Goldberg MJ, Watson P, Rogers JD, Gomes AJ, Kromine A, Brand RE, Jameel M, Bogovejic A, Pradhan P, Backman V. Association between rectal optical signatures and colonic neoplasia: potential applications for screening. Cancer Res 2009; 69:4476-83. [PMID: 19417131 DOI: 10.1158/0008-5472.can-08-4780] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Field carcinogenesis detection represents a promising means for colorectal cancer (CRC) screening, although current techniques (e.g., flexible sigmoidoscopy) lack the requisite sensitivity. The novel optical technology low-coherence enhanced backscattering (LEBS) spectroscopy, allows identification of microscale architectural consequences of the field carcinogenesis in preclinical CRC models with unprecedented accuracy. To investigate the potential clinical translatability of this approach, we obtained biopsies from the normal-appearing rectal mucosa from patients undergoing colonoscopy (n = 219). LEBS signals were recorded through a bench-top instrument. Four parameters characterizing LEBS signal were linearly combined into a single marker. We found that LEBS signal parameters generally mirrored neoplasia progression from patients with no neoplasia, to 5 to 9 mm adenoma and to advanced adenomas. The composite LEBS marker calculated from the LEBS signal paralleled this risk status (ANOVA P < 0.001). Moreover, this was independent of CRC risk factors, benign colonic findings, or clinically unimportant lesions (diminutive adenomas, hyperplastic polyps). For advanced adenomas, the LEBS marker had a sensitivity of 100%, specificity of 80%, and area under the receiver operator characteristic curve of 0.895. Leave-one-out cross-validation and an independent data set (n = 51) supported the robustness of these findings. In conclusion, we provide the first demonstration that LEBS-detectable alterations in the endoscopically normal rectum were associated with the presence of neoplasia located elsewhere in the colon. This study provides the proof of concept that rectal LEBS analysis may potentially provide a minimally intrusive CRC screening technique. Further studies with an endoscopically compatible fiber optic probe are under way for multicenter clinical validation.
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Affiliation(s)
- Hemant K Roy
- Department of Medicine, Evanston-Northwestern Healthcare, Northwestern University, Evanston, IL 60201, USA.
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Abstract
PURPOSE OF REVIEW There is a wealth of literature, both from epidemiological and molecular studies, which support the role of aberrant crypt foci (ACF) as a putative precursor to colorectal adenomas and a potential biomarker for colorectal carcinoma. In this review, we critically examine the evidence on employing ACF as an intermediate endpoint. RECENT FINDINGS Recent, larger-scale, multicenter studies of ACF have raised questions about ACF. The prevalence of ACF has not correlated with colorectal adenomas, and the technique for ACF detection using high-magnification chromoendoscopy has demonstrated considerable variability across endoscopists and over time. Dysplastic ACF, once postulated as the ACF destined for adenomatous transformation, have been rarely identified in US individuals, in contrast to European and Japanese investigations. A substantial percentage of purported, endoscopically detected ACF have not been confirmed on histologic review. Finally, molecular characterization of ACF has been studied on only a limited basis. SUMMARY ACF remain a potential biomarker for colorectal cancer, but similar to other biomarkers under development, additional study of ACF is needed before reliable, clinical application can be assured.
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Raju J. Azoxymethane-induced rat aberrant crypt foci: Relevance in studying chemoprevention of colon cancer. World J Gastroenterol 2008; 14:6632-5. [PMID: 19034964 PMCID: PMC2773303 DOI: 10.3748/wjg.14.6632] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The pathogenesis of colon cancer involves sequential and multistep progression of epithelial cells initiated to a cancerous state with defined precancerous intermediaries. Aberrant crypt foci (ACF) represent the earliest identifiable intermediate precancerous lesions during colon carcinogenesis in both laboratory animals and humans. ACF are easily induced by colon-specific carcinogens in rodents and can be used to learn more about the process of colon carcinogenesis. For over two decades, since its first discovery, azoxymethane (AOM)-induced rodent ACF have served as surrogate biomarkers in the screening of various anticarcinogens and carcinogens. Several dietary constituents and phytochemicals have been tested for their colon cancer chemopreventive efficacy using the ACF system. There has been substantial effort in defining and refining ACF in terms of understanding their molecular make-up, and extensive research in this field is currently in progress. In chemoprevention studies, AOM-induced rat ACF have been very successful as biomarkers, and have provided several standardized analyses of data. There have been several studies that have reported that ACF data do not correlate to actual colon tumor outcome, however, and hence there has been an ambiguity about their role as biomarkers. The scope of this mini-review is to provide valuable insights and limitations of AOM-induced rat ACF as biomarkers in colon cancer chemoprevention studies. The role of the dynamics and biological heterogeneity of ACF is critical in understanding them as biomarkers in chemoprevention studies.
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