Lectin reactivities as intermediate biomarkers in premalignant colorectal epithelium

Effects of low-to-moderate ethanol consumption on colonic growth and gene expression in young adult and middle-aged male rats

Excessive alcohol consumption is a risk factor associated with colorectal cancer; however, some epidemiological studies have reported that moderate alcohol consumption may not contribute additional risk or may provide a protective effect reducing colorectal cancer risk. Prior research highlights the importance of proliferation, differentiation, and apoptosis as parameters to consider when evaluating colonic cell growth and tumorigenesis. The present study investigated whether chronic low-to-moderate ethanol consumption altered these parameters of colonic cell growth and expression of related genes. Twenty-four nondeprived young adult (109 days old) and 24 nondeprived middle-aged (420 days old) Wistar rats were randomly assigned to an ethanol-exposed or a water control group (n = 12/group). The ethanol group was provided voluntary access to a 20% v/v ethanol solution on alternate days for 13 weeks. Colon tissues were collected for quantitative immunohistochemical analyses of cell proliferation, differentiation and apoptosis using Ki-67, goblet cell and TUNEL, respectively. Gene expression of cyclin D1 (Ccnd1), Cdk2, Cdk4, p21waf1/cip1 (Cdkn1a), E-cadherin (Cdh1) and p53 were determined by quantitative real-time polymerase chain reaction in colonic scraped mucosa. Ethanol treatment resulted in a lower cell proliferation index and proliferative zone, and lower Cdk2 expression in both age groups, as well as trends toward lower Ccnd1 and higher Cdkn1a expression. Cell differentiation was modestly but significantly reduced by ethanol treatment only in older animals. Overall, older rats showed decreases in apoptosis and gene expression of Cdk4, Cdh1, and p53 compared to younger rats, but there was no observed effect of ethanol exposure on these measures. These findings suggest that low-to-moderate ethanol consumption improves at least one notable parameter in colonic tumorigenesis (cell proliferation) and associated gene expression regardless of age, however, selectively decreased cell differentiation among older subjects.

Tumor recognition of peanut agglutinin-immobilized fluorescent nanospheres in biopsied human tissues

We are investigating an imaging agent for early detection of colorectal cancer. The agent, named the nanobeacon, is coumarin 6-encapsulated polystyrene nanospheres whose surfaces are covered with poly(N-vinylacetamide) and peanut agglutinin that reduces non-specific interactions with the normal mucosa and exhibits high affinity for terminal sugars of the Thomsen-Friedenreich antigen, which is expressed cancer-specifically on the mucosa, respectively. We expect that cancer can be diagnosed by detecting illumination of intracolonically administered nanobeacon on the mucosal surface. In the present study, biopsied human tissues were used to evaluate the potential use of the nanobeacon in the clinic. Prior to the clinical study, diagnostic capabilities of the nanobeacon for detection of colorectal cancer were validated using 20 production batches whose characteristics were fine-tuned chemically for the purpose. Ex vivo imaging studies on 66 normal and 69 cancer tissues removed from the colons of normal and orthotopic mouse models of human colorectal cancer, respectively, demonstrated that the nanobeacon detected colorectal cancer with excellent capabilities whose rates of true and false positives were 91% and 5%, respectively. In the clinical study, normal and tumor tissues on the large intestinal mucosa were biopsied endoscopically from 11 patients with colorectal tumors. Histological evaluation revealed that 9 patients suffered from cancer and the rest had adenoma. Mean fluorescence intensities of tumor tissues treated with the nanobeacon were significantly higher than those of the corresponding normal tissues. Correlation of magnitude relation of the intensity in individuals was observed in cancer patients with a high probability (89%); however, the probability reduced to 50% in adenoma patients. There was a reasonable likelihood for diagnosis of colorectal cancer by the nanobeacon applied to the mucosa of the large intestine.

Plant Lectins Targeting O-Glycans at the Cell Surface as Tools for Cancer Diagnosis, Prognosis and Therapy

Aberrant O-glycans expressed at the surface of cancer cells consist of membrane-tethered glycoproteins (T and Tn antigens) and glycolipids (Lewis a, Lewis x and Forssman antigens). All of these O-glycans have been identified as glyco-markers of interest for the diagnosis and the prognosis of cancer diseases. These epitopes are specifically detected using T/Tn-specific lectins isolated from various plants such as jacalin from Artocarpus integrifola, and fungi such as the Agaricus bisporus lectin. These lectins accommodate T/Tn antigens at the monosaccharide-binding site; residues located in the surrounding extended binding-site of the lectins often participate in the binding of more extended epitopes. Depending on the shape and size of the extended carbohydrate-binding site, their fine sugar-binding specificity towards complex O-glycans readily differs from one lectin to another, resulting in a great diversity in their sugar-recognition capacity. T/Tn-specific lectins have been extensively used for the histochemical detection of cancer cells in biopsies and for the follow up of the cancer progression and evolution. T/Tn-specific lectins also induce a caspase-dependent apoptosis in cancer cells, often associated with a more or less severe inhibition of proliferation. Moreover, they provide another potential source of molecules adapted to the building of photosensitizer-conjugates allowing a specific targeting to cancer cells, for the photodynamic treatment of tumors.

Molecular mechanism of anticancer effect of Sclerotium rolfsii lectin in HT29 cells involves differential expression of genes associated with multiple signaling pathways: A microarray analysis

Sclerotium rolfsii lectin (SRL) is a lectin isolated from fungus S. rolfsii and has high binding specificity toward the oncofetal Thomsen-Friedenreich carbohydrate antigen (Galβ1-3GalNAc-α-O-Ser/Thr, T or TF), which is expressed in more than 90% of human cancers. Our previous studies have shown that binding of SRL to human colon, breast and ovarian cancer cells induces cell apoptosis in vitro and suppresses tumor growth in vivo. This study investigated the SRL-mediated cell signaling in human colon cancer HT29 cells by mRNA and miRNA microarrays. It was found that SRL treatment results in altered expression of several hundred molecules including mitogen-activated protein kinase (MAPK) and c-JUN-associated, apoptosis-associated and cell cycle and DNA replication-associated signaling molecules. Pathway analysis using GeneSpring 12.6.1 revealed that SRL treatment induces changes of MAPK and c-JUN-associated signaling pathways as early as 2 h while changes of cell cycle, DNA replication and apoptosis pathways were significantly affected only after 24 h. A significant change of cell miRNA expression was also observed after 12 h treatment of the cells with SRL. These changes were further validated by quantitative real time polymerase chain reaction and immunoblotting. This study thus suggests that the presence of SRL affects multiple signaling pathways in cancer cells with early effects on cell proliferation pathways associated with MAPK and c-JUN, followed by miRNA-associated cell activity and apoptosis. This provides insight information into the molecular mechanism of the anticancer activity of this fungal lectin.

Use of proteins as biomarkers and their role in carcinogenesis

Summary: Improved diagnostic methods and medical therapies are necessary for early detection and treatment and an improved prognosis. It is thus vital to both examine and evaluate the role of the various existing proteins as biomarkers in carcinogenesis and to assess the contribution of these proteins in anti-cancer activity, for consideration in therapeutic strategies. It is essential to both examine and evaluate the role of the various existing proteins as biomarkers in carcinogenesis and to assess the contribution of these proteins in anti-cancer activity, for consideration in therapeutic strategies. The purpose of this review is twofold. Firstly, it is to evaluate recent data about which proteins can be utilized as biomarkers in carcinogenesis. The proteins reviewed include: CPTP, IL-6, CCN, and S100. Secondly, it is to evaluate the contribution of dietary proteins in cancer activity. Specifically, how whey protein, soy proteins and lectin, a phytochemical could be useful in cancer prevention and treatment.

Recent Findings: Whey protein, present in dairy products, is an excellent source of the sulphur amino acid cysteine, the rate limiting substrate in glutathione synthesis. Notably, this protein survives digestion and has been shown to have anti-carcinogenic properties in animal studies. Lectins are phytochemicals present in plant foods, and have active components which alters cancer initiation, promotion and progression. Lectins have been characterized as a useful tool in biochemistry, cell biology, immunology and in diagnostic and therapeutic purposes in cancer research. Soy proteins contain various compounds, including isoflavones, protease inhibitors and protein kinase inhibitors, which have been proven effective in tumor growth inhibition. They have therefore, been greatly emphasized in cancer prevention and treatment. It has been proved that soy food consumption was associated with decreased risk of death and recurrence of breast cancer. CPTP is a recently discovered protein whose main role is to transport C1P, a pro-inflammatory molecule. The discovery of CPTP may shine a light on the mechanism of inflammatory diseases, and hopefully offer a potential target for therapeutic purposes in cancer research. Interleukin-6 is a multifunctional cytokine that affects the activity of cancer cells. It is involved in tumor growth, and elevated levels is associated with an increased risk of cancer. S100B is a well-established biomarker for malignant melanoma, and useful in assessing tumor load, stage and prognosis for patients with this disease. Other members of this family of proteins include S100A4, which has been associated with several malignancies and S100A2, which has been found to be decreased in some cancers. CCN are a group of regulatory proteins, located in the extracellular matrix (maricellular). They are involved in cellular adhesion, mitogenesis, chemotaxis, cell survival, and wound healing. CCN proteins are also able to modulate the signals of several proteins, which may also influence skeletal development and angiogenesis. Many of the functions of these proteins are thus also related to tumor growth. Furthermore, CCN interacts with estrogen in the development of cancer, and is implicated in some breast and ovarian cancers.

Bioactive peptides in cereals and legumes: agronomical, biochemical and clinical aspects

Cereals and legumes are key components of a healthy and balanced diet. Accordingly, many national nutritional guidelines emphasize their health promoting properties by placing them at the base of nutritional food pyramids. This concept is further validated by the observed correlation between a lower risk and occurrence of chronic diseases and the adherence to dietary patterns, like the Mediterranean diet, in which cereal grains, legumes and derived products represent a staple food. In the search for a dietary approach to control/prevent chronic degenerative diseases, protein derived bioactive peptides may represent one such source of health-enhancing components. These peptides may already be present in foods as natural components or may derive from hydrolysis by chemical or enzymatic treatments (digestion, hydrolysis or fermentation). Many reports are present in the literature regarding the bioactivity of peptides in vitro and a wide range of activities has been described, including antimicrobial properties, blood pressure-lowering (ACE inhibitory) effects, cholesterol-lowering ability, antithrombotic and antioxidant activities, enhancement of mineral absorption/bioavailability, cyto- or immunomodulatory effects, and opioid-like activities. However it is difficult to translate these observed effects to human. In fact, the active peptide may be degraded during digestion, or may not be absorbed or reach the target tissues at a concentration necessary to exert its function. This review will focus on bioactive peptides identified in cereals and legumes, from an agronomical and biochemical point of view, including considerations about requirements for the design of appropriate clinical trials necessary for the assessment of their nutraceutical effect in vivo.

Lectin binding and effects in culture on human cancer and non-cancer cell lines: examination of issues of interest in drug design strategies

By using a non-cancer and a cancer cell line originally from the same tissue (colon), coupled with testing lectins for cell binding and for their effects on these cell lines in culture, this study describes a simple multi-parameter approach that has revealed some interesting results that could be useful in drug development strategies. Two human cell lines, CCL-220/Colo320DM (human colon cancer cells, tumorigenic in nude mice) and CRL-1459/CCD-18Co (non-malignant human colon cells) were tested for their ability to bind to agarose microbeads derivatized with two lectins, peanut agglutinin (Arachis hypogaea agglutinin, PNA) and Dolichos biflorus agglutinin (DBA), and the effects of these lectins were assessed in culture using the MTT assay. Both cell lines bound to DBA-derivatized microbeads, and binding was inhibited by N-acetyl-D-galactosamine, but not by L-fucose. Neither cell line bound to PNA-derivatized microbeads. Despite the lack of lectin binding using the rapid microbead method, PNA was mitogenic in culture at some time points and its mitogenic effect displayed a reverse-dose response. This was also seen with effects of DBA on cells in culture. While this is a simple study, the results were statistically highly significant and suggest that: (1) agents may not need to bind strongly to cells to exert biological effects, (2) cell line pairs derived from diseased and non-diseased tissue can provide useful comparative data on potential drug effects and (3) very low concentrations of potential drugs might be initially tested experimentally because reverse-dose responses should be considered.

Lectins as Bioactive Plant Proteins: A Potential in Cancer Treatment

Plant lectins, a unique group of proteins and glycoproteins with potent biological activity, occur in foods like wheat, corn, tomato, peanut, kidney bean, banana, pea, lentil, soybean, mushroom, rice, and potato. Thus, dietary intakes by humans can be significant. Many lectins resist digestion, survive gut passage, and bind to gastrointestinal cells and/or enter the circulation intact, maintaining full biological activity. Several lectins have been found to possess anticancer properties in vitro, in vivo, and in human case studies; they are used as therapeutic agents, preferentially binding to cancer cell membranes or their receptors, causing cytotoxicity, apoptosis, and inhibition of tumor growth. These compounds can become internalized into cells, causing cancer cell agglutination and/or aggregation. Ingestion of lectins also sequesters the available body pool of polyamines, thereby thwarting cancer cell growth. They also affect the immune system by altering the production of various interleukins, or by activating certain protein kinases. Lectins can bind to ribosomes and inhibit protein synthesis. They also modify the cell cycle by inducing non-apoptotic G1-phase accumulation mechanisms, G2/M phase cell cycle arrest and apoptosis, and can activate the caspase cascade. Lectins can also downregulate telomerase activity and inhibit angiogenesis. Although lectins seem to have great potential as anticancer agents, further research is still needed and should include a genomic and proteomic approach.

Lectins: from basic science to clinical application in cancer prevention

Many physiological functions are attributable to lectin-carbohydrate interactions. Lectins are currently being studied for their ability to destroy tumour growth by binding to specific carbohydrate motifs on cancer cells. Cell-surface molecules, including growth factor receptors are often glycosylated, and lectins may act by binding to these. Certain lectins effect the proliferation of intestinal epithelial cells. This effect is cell-type and lectin specific and occurs in the intestine of intact animals, in human colonic explants and colorectal cancer cell lines. Lectins present in mammalian tissue are involved in cell-matrix adhesion, differentiation, lymphocyte circulation and immunomodulation. Mammalian lectins contribute to detection, diagnosis and prognosis of tumour cells, and can be targeted for therapy. New lectins of plant and mammalian origin that have one or more of these functions are currently being developed as tools that could be used to target tumour cells.

Inherited predisposition to cancer: a historical overview

The hereditary predisposition to cancer dates historically to interest piqued by physicians as well as family members wherein striking phenotypic features were shown to cluster in families, inclusive of the rather grotesque cutaneous findings in von Recklinghausen's neurofibromatosis, which date back to the sixteenth century. The search for the role of primary genetic factors was heralded by studies at the infrahuman level, particularly on laboratory mouse strains with strong susceptibility to carcinogen-induced cancer, and conversely, with resistance to the same carcinogens. These studies, developed in the 19th and 20th centuries, continue today. This article traces the historical aspects of hereditary cancer dealing with identification and ultimate molecular genetic confirmation of commonly occurring cancers, particularly of the colon in the case of familial adenomatous polyposis and its attenuated form, both due to the APC germline mutation; the Lynch syndrome due to mutations in mismatch repair genes, the most common of which were found to be MSH2, MLH1, and MSH6 germline mutations; the hereditary breast-ovarian cancer syndrome with BRCA1 and BRCA2 germline mutations; the Li-Fraumeni (SBLA) syndrome due to the p53 mutation; and the familial atypical multiple mole melanoma in association with pancreatic cancer due to the CDKN2A (p16) germline mutation. These and other hereditary cancer syndromes have been discussed in some detail relevant to their characterization, which, for many conditions, took place in the late 18th century and, in the more modern molecular genetic era, during the past two decades. Emphasis has been placed upon the manner in which improved cancer control will emanate from these discoveries.

Aberrant crypt foci as microscopic precursors of colorectal cancer

Since the first detection of aberrant crypt foci (ACF) in carcinogen-treated mice, there have been numerous studies focusing on these microscopically visible lesions both in rodents and in humans. ACF have been generally accepted as precancerous lesions in regard to histopathological characteristics, biochemical and immunohistochemical alterations, and genetic and epigenetic alterations. ACF show variable histological features, ranging from hyperplasia to dysplasia. ACF in human colon are more frequently located in the distal parts than in the proximal parts, which is in accordance with those in colorectal cancer (CRC). The immunohistochemical expressions of carcinoembryonic antigen (CEA), β-catenin, placental cadherin (P-cadherin), epithelial cadherin (E-cadherin), inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2), and P16^INK4a are found to be altered. Genetic mutations of K-ras, APC and p53, and the epigenetic alterations of CpG island methylation of ACF have also been demonstrated. Genomic instabilities due to the defect of mismatch repair (MMR) system are detectable in ACF. Two hypotheses have been proposed. One is the "dysplasia ACF-adenoma-carcinoma sequence", the other is "heteroplastic ACF-adenoma-carcinoma sequence". The malignant potential of ACF, especially dysplastic ACF, makes it necessary to reveal the nature of these lesions, and to prevent CRC from the earliest possible stage. The technique of magnifying chromoscope makes it possible to detect "in vivo" ACF, which is beneficial to colon cancer research, identifying high-risk populations for CRC, and developing preventive procedures.

Patchy field defects of apoptosis resistance and dedifferentiation in flat mucosa of colon resections from colon cancer patients

BACKGROUND

Abnormal areas in normal-appearing flat colonic mucosa (field defects) may predispose individuals to colon cancer. Markers of field defects would indicate cancer risk.

METHODS

We evaluated apoptosis capability, dedifferentiation, frequency of simple aberrant crypts, aberrant crypt foci, microadenomas, and total nicotinamide adenine dinucleotide levels at locations within normal-appearing flat mucosa obtained from colon resections.

RESULTS

Among goblet cells from colonic mucosa samples of individuals without colonic neoplasia, there was a high mean deoxycholate-induced apoptotic index (AI) of 59.1% and high Dolichos biflorus agglutinin (DBA) lectin reactivity (differentiation) in 85.0% of samples. In contrast, flat mucosa samples from colon cancer patients had a significantly (P <.01) lower average AI of 37.4%, and a significantly (P =.03) lower percentage (40.5%) had high DBA reactivity. For colon cancer patients, AI and DBA reactivity values were patchy within a resection. Nicotinamide adenine dinucleotide levels were highly variable among individuals without neoplasia, and aberrant crypt foci and microadenomas were rare.

CONCLUSIONS

AI and aberrant DBA reactivity are promising indicators of colon cancer risk. Our results attest to the importance of obtaining multiple samples to assess colon cancer risk because of the patchy nature of field defects.

Phytic acid in wheat bran affects colon morphology, cell differentiation and apoptosis

Wheat bran (WB) and its component phytic acid (PA) have both been shown to decrease early biomarkers of colon carcinogenesis, i.e. the PCNA labeling index of cell proliferation and certain aberrant crypt foci parameters. However, it is not known how WB and PA alter other biomarkers of colon cancer risk, such as rate of apoptosis and degree of differentiation, or how they affect colon morphology. Thus, the objectives of this study were to determine the effects of WB on these parameters, to see if PA contributes to these effects and whether there is a difference between endogenous and exogenously added PA. Five groups of azoxymethane-treated male Fischer 344 rats were fed a basal control diet (BD) or BD supplemented with either 25% wheat bran, 25% dephytinized wheat bran (DWB), 25% DWB plus 1.0% PA or 1.0% PA for 100 days. The WB, DWB and PA diets significantly increased the rate of apoptosis and cell differentiation in the whole crypt and the top 40% of the crypt. The WB, DWB and PA diets also significantly increased cell apoptosis in the bottom 60% of the crypt, while all the treatment groups significantly increased cell differentiation versus the BD group in the bottom 60% of the crypt. In addition, the WB, DWB and PA diets decreased the number of crypts per millimeter of colon, while the DWB and PA diets also decreased crypt height measured as number of cells. It is concluded that WB, partly due to its dietary fiber and endogenous PA, and exogenous PA when added to a low fiber diet can increase cell apoptosis and differentiation and favorably affect colon morphology.

Grading dysplasia in colorectal adenomas by means of the quantitative binding pattern determination of Arachis hypogaea, Dolichos biflorus, Amaranthus caudatus, Maackia amurensis, and Sambucus nigra agglutinins

The current study deals with the setting up of a new tool that enables the benign versus the malignant nature of colorectal adenomas to be determined accurately. The 2 objectives are to determine (1) whether adenomas should, or should not, be included in a 2- or a 3-tier grading system, and (2) whether severe dysplasias and carcinomas in situ share common or different biological characteristics. The levels of expression of different types of glycoconjugates were characterized in a series of 166 colorectal specimens, including 14 normal, 90 dysplastic, and 62 cancerous cases. The glycoconjugate expressions were demonstrated for 5 lectins, namely, Arachis hypogaea (PNA), Dolichos biflorus (DBA), Amaranthus caudatus (ACA), Maackia amurensis (MAA) and Sambucus nigra (SNA). The glycoconjugates demonstrated by these 5 lectins belong to the family of the Thomsen-Friedenreich antigens. The binding patterns of the 5 lectins were quantitatively determined by means of computer-assisted microscopy. The quantitative data were submitted to discriminant analyses. Our results show that the specific glycochemical staining patterns could be identified unambiguously and without misclassification between benign (normal and low dysplasia) and malignant (ie, either as moderate/severe dysplasia, carcinoma in situ, or cancer) cases. The data also strongly suggested that (1) dysplasias seem to be distinguishable in 2 instead of 3 groups, that is, low versus moderate/severe (high); and (2) moderate/severe dysplasias are biologically distinct from carcinomas in situ. The methodology developed can be applied directly in routine diagnosis to identify moderate/severe dysplasia specimens already exhibiting features common to carcinomas, and which therefore should be treated consistently in view of the fact that our data strongly suggest that most moderate/severe dysplasias are still benign, whereas carcinomas in situ are real carcinomatous lesions.

Lectin binding to human colonocytes is predictive of colonic neoplasia

OBJECTIVE

The aim of this study was to determine whether lectin binding to exfoliated human colonocytes could be used as a noninvasive test for colorectal polyps or cancer.

METHODS

Colonocytes were harvested from 31 patients (10 controls, 10 with adenomatous polyps, and 11 with cancer), incubated with a panel of fluorescent-labeled lectins, and assayed by flow cytometry.

RESULTS

The lectins jacalin (JAC) and wheat germ agglutinin (WGA) were useful in predicting the presence of a colorectal neoplasm (p = 0.0018 for JAC and p = 0.0099 for WGA). For JAC, sensitivity reached 81% with a specificity of 80%, and for WGA the sensitivity and specificity were both 75%.

CONCLUSIONS

Lectin binding to human colonocytes can predict the presence of malignant and premalignant lesions of the colon, and has potential as a noninvasive screening tool for colorectal neoplasms.

Functional food science and gastrointestinal physiology and function

The gut is an obvious target for the development of functional foods, acting as it does as the interface between diet and the metabolic events which sustain life. The key processes in digestive physiology which can be regulated by modifying diet are satiety, the rate and extent of macronutrient breakdown and absorption from the small bowel, sterol metabolism, the colonic microflora, fermentation, mucosal function and bowel habit, and the gut immune system. The intestinal microflora is the main focus of many current functional foods. Probiotics are foods which contain live bacteria which are beneficial to health whilst prebiotics, such as certain non-digestible oligosaccharides which selectively stimulate the growth of bifidobacteria in the colon, are already on the market. Their claimed benefits are to alleviate lactose maldigestion, increase resistance to invasion by pathogenic species of bacteria in the gut, stimulate the immune system and possibly protect against cancer. There are very few reports of well-designed human intervention studies with prebiotics as yet. Certain probiotic species have been shown to shorten the duration of rotavirus diarrhoea in children but much more work is needed on the mechanism of immunomodulation and of competitive exclusion and microflora modification. The development of functional foods for the gut is in its infancy and will be successful only if more fundamental research is done on digestive physiology, the gut microflora, immune system and mucosal function.

Phenotypic and genotypic characteristics of aberrant crypt foci in human colorectal mucosa

Aberrant crypt foci (ACF) in colorectal mucosa are proposed to be the earliest morphological lesion in the development of neoplasia, but their characteristics remain controversial. We therefore studied the epithelial phenotype and genotype of ACF from patients with familial adenomatous polyposis (FAP) and of sporadic ACF by evaluating glycoprotein markers associated with neoplasia (lectins Dolichus biflorus agglutinin and peanut agglutinin; monoclonal antibody CA 19-9 against sialyl Lewis-a blood group substance), expression of proliferating cell nuclear antigen, and ras proto-oncogene mutations. The utility of the markers was established by comparing adenomas and hyperplastic polyps. Most FAP ACF resembled adenomas and were found to differ from sporadic ACF in their high frequency of dysplasia, staining with Dolichus biflorus agglutinin, expression of sialyl Lewis-a, proliferation in the epithelium of upper crypts, and low frequency of ras gene mutations (P = .04 to < .0000001). By contrast, sporadic ACF and a subset of FAP ACF had phenotypic characteristics resembling hyperplastic polyps but usually had ras mutations, which were inversely related to dysplasia (P = .00009). Our findings suggest that "aberrant crypt focus" is a generic term analogous to "polyp" and requires further histopathologic, phenotypic, or genotypic classification into dysplastic and heteroplastic (hetero = other, plasia = form) types. Dysplastic ACF represent potential precursors to colorectal adenomas and adenocarcinomas, but heteroplastic ACF appear to be associated, rather than precursor, lesions.

Lectin histochemistry of astrocytic tumors and in vitro characterization of lectin-induced modifications on the proliferation of the SW1088, U373 and U87 human astrocytic cell lines

The role of lectins as biosignalling molecules or as markers of human astrocytic tumors remains relatively unexplored. The aim of the present work is to investigate (1) whether or not human astrocytic tumors express specific glycans, evidenced experimentally by means of lectin histochemistry, and (2) whether, in turn, these lectins can significantly modulate astrocytic tumor cell proliferation. Using a cell image processor, we therefore began by quantitatively measuring the histochemical binding pattern of 5 lectins (WGA, PNA, PHA-L, GSA-IA4 and Con A) in 5 astrocytomas, 5 anaplastic astrocytomas and 5 glioblastomas. Secondly, we measured the influence of these 5 lectins on the proliferation of 3 astrocytic tumor cell lines (SW1088, U373 and U87) growing in vitro as monolayers. Cell proliferation was assessed by means of the colorimetric MTT assay. The histochemical lectin staining markedly varied intra- and inter-group. However, some constant results were obtained. Indeed, the staining increased markedly from GSA-IA4 and PHA-L through WGA and PNA to ConA in the three histopathological groups. The assessment of cell proliferation demonstrated that WGA, Con A and PHA-L very significantly decreased proliferation in the 3 astrocytic cell lines in a dose-dependent manner. Astrocytic tumor cells in the confluent growth phase were less sensitive to the WGA, Con A and PHA-L lectin-induced effects than cells in the log growth phase. The GSA-IA4 and PNA lectins had globally very weak effects on the proliferation of the astrocytic tumor cell lines. Increasing the fetal calf serum from 1% to 10% in the culture media significantly antagonized the WGA-, Con A- and PHA-L-induced cell proliferation decrease in the 3 astrocytic cell lines. In conclusion, the present data strongly suggest that some lectins (including WGA, Con A and PHA-L) significantly influence the proliferation of astrocytic tumor cells.

Relationship among colonocyte proliferation, differentiation, and apoptosis as a function of diet and carcinogen

To determine the relationship among colonocyte proliferation, differentiation, and apoptosis as a function of fiber and carcinogen, we conducted a 2 x 2 factorial design study with two fibers (pectin or cellulose) and two injection protocols (azoxymethane or saline) in male Sprague-Dawley rats. Rats were killed six weeks after the injections, and in vivo cell proliferation was measured by incorporation of bromodeoxyuridine into DNA, differentiation by binding of the lectin Dolichos biflorus agglutinin, and apoptosis by immunoperoxidase detection of digoxigenin-labeled genomic DNA. In the proximal colon, pectin decreased differentiation and apoptosis, resulting in a greater number of cells per crypt column. In the distal colon, pectin increased cell proliferation, resulting in more crypts per millimeter of colon and a greater number of surface cells. Azoxymethane increased cell proliferation and decreased differentiation and apoptosis in the proximal and the distal colon. This resulted in a greater number of surface cells proximally and more crypts per millimeter of colon distally. These results illustrate the importance of considering all three parameters (proliferation, differentiation, and apoptosis) when evaluating neoplastic growth.

Differential histochemical peanut agglutinin stain in benign and malignant human prostate tumors: relationship with prostatic specific antigen immunostain and nuclear DNA content

The histochemical binding pattern of the peanut (Arachis hypogaea) lectin (PNA) was quantitatively described by means of computer-assisted microscope analysis in 28 benign prostatic hyperplasias (BPH), 15 prostatic intraepithelial neoplasias (PIN), and 119 prostatic adenocarcinomas. PNA exhibits nonimmune but selective binding to glycoproteins with beta-D-galactosyl(1,3)-N-acetyl-D-galactosamine residues. We also investigated whether a relationship existed between the number of histochemical-related PNA acceptors and the histochemical prostate-specific antigen (PSA) stain intensity, and between the number of PNA receptors and DNA ploidy level. The results show that neoplastic prostate tissues and high-grade intraepithelial prostatic neoplasias (PIN2_3) exhibit a significantly higher number of PNA acceptors than benign prostatic hyperplasias and low (PIN1) grade prostatic intraepithelial neoplasias. A statistically significant correlation was observed between the number of histochemically related PNA acceptors and PSA immunostain intensity. Lastly, diploid prostatic tumors, whether benign or malignant, exhibited a significantly higher number of PNA acceptors than aneuploid ones. These results suggest that PNA acceptors play an important role in the biology of prostate tumors.

Inhibition of aberrant crypt growth by non-steroidal anti-inflammatory agents and differentiation agents in the rat colon

Aberrant crypts are aggregates of single to multiple colonic crypts evidencing hallmarks of dysplasia and may be the earliest detectable pathological lesions for colon cancer. The aberrant crypt assay has been developed in 2 protocols. In one, putative chemoprevention agents are tested for inhibitory effects when administered concomitantly with a carcinogen. In the other, the objective of this study, aberrant crypts were induced in F344 rats by parenteral injection of the colon carcinogen azoxymethane (AOM) and allowed to develop for 4 weeks, when an average of 90-100 aberrant crypt foci per colon were found in the methylene blue-stained colon. Then, during the second 4 weeks of the experiment, aberrant crypts were allowed to further develop to a frequency of > 150 foci per colon, a time when multi-crypt foci were observed. During this time we tested the inhibitory effects of 4 analgesic drugs and 2 differentiation agents for effects of aberrant crypt growth and development. We found the non-steroidal anti-inflammatory drugs piroxicam, aspirin and ibuprofen, but not acetaminophen, to be effective in suppressing aberrant crypt formation or the progression to foci of multiple aberrant crypts. Treatment with chemosuppressing agents 13-cis-retinoic acid (13-cRA) and 4-hydroxyphenretinamide (4-HPR), known differentiating agents, however, did suppress expansion of aberrant crypt foci, with 13-cRA being the much more potent agent.

Monoclonal antibody recognizing a determinant on type 2 chain blood group A and B oligosaccharides detects oncodevelopmental changes in azoxymethane-induced rat colon tumors and human colon cancer cell lines

Altered expression of ABH blood group substances is a common feature of human colorectal carcinoma, yet it remains unclear how these structural changes influence the biological properties of tumor cells. Azoxymethane-induced rat colon tumors display many features of the human disease, thereby providing a potentially useful model to study the role of blood group substances in colon cancer progression. We have prepared monoclonal antibodies to a microsomal fraction isolated from an azoxymethane-induced rat colon tumor and selected an antibody that detects cancer-associated changes. Monoclonal antibody (mAb) 3A7 recognizes a determinant on type 2 chain blood group A (GalNAc alpha 1-3[Fuc alpha 1-2]Gal beta 1-4GlcNAc-R) and B (Gal alpha 1-3[Fuc alpha 1-2]Gal beta 1-4GlcNAc-R) oligosaccharides. Expression of the epitope detected by this antibody was developmentally regulated in rat colon, with maximal expression from day 4-21 after birth. Immunohistochemical staining and Western blotting analyses of azoxymethane-induced colon tumors revealed increased expression of the epitope in all of the 21 colonic tumors examined, including preneoplastic glands within transitional mucosa. Conventional and signet-ring adenocarcinomas that had invaded through the muscularis propria (Duke's B2) consistently showed the most intense staining with mAb 3A7, including regions depicting angioinvasion. Some of the lymph node metastases (Duke's C2) stained poorly with the antibody. The epitope was also expressed in blood group A positive human colon carcinoma cell lines, including HT29 and SW480 but not by SW620, a cell line derived from a lymph node metastasis isolated in vivo from the SW480 primary tumor, or in the blood group B cell line SW1417. The glycoproteins detected by mAb 3A7 in rat colon tumors and HT29 cells ranged in size between 50 and 200 kd, including a major species of 140 kd. Affinity chromatography of detergent lysates of normal rat colon on the blood group A specific lectin Dolichos biflorus (DBA)-agarose resulted in nearly quantitative binding of glycoprotein species detected by the antibody. By contrast, immunoreactive glycoproteins from rat colon tumors or HT29 cells bound poorly to DBA-agarose but were retained by another blood group A-binding lectin, Helix-pomatia (HPA)-agarose. These results indicate that colon carcinogenesis results in quantitative as well as qualitative changes in oligosaccharides detected by mAb 3A7 and suggest that the combined use of mAb 3A7 and blood group A-specific lectins may provide a useful tool for early detection of colon cancer.

Carcinoembryonic antigen in human colonic aberrant crypt foci

BACKGROUND/AIMS

Aberrant crypt foci are putative preneoplastic lesions that, by definition, are identified microscopically in whole-mount preparations of colonic mucosa. Because the identification of hexosaminidase as a marker for rat aberrant crypt foci in histological sections facilitated their characterization, a similar marker for human foci in histological sections was sought.

METHODS

Human aberrant crypt foci were marked in whole-mount preparations, embedded in paraffin, and evaluated for their expression of carcinoembryonic antigen with two monoclonal antibodies.

RESULTS

Elevated expression of carcinoembryonic antigen was detected in 39 of 42 (93%) aberrant crypt foci from 15 patients. The expression of carcinoembryonic antigen assisted in the evaluation of longitudinal sections of foci, where dysplasia is more readily detected in these small lesions. The expression of carcinoembryonic antigen was related to the sizes of the foci (P = 0.0085, generalized Fisher's Exact Test) but not to the presence or degree of dysplasia.

CONCLUSIONS

The overexpression of immunohistochemically demonstrable carcinoembryonic antigen is, to date, the only described alteration in most of these putative precursors of human colon cancer that differs from the expression in contiguous, normal crypts at the histological level and thus facilitates the identification of aberrant crypts in histological sections for further characterization.

The lectin Griffonia simplicifolia I-A4 (GS I-A4) specifically recognizes terminal alpha-linked N-acetylgalactosaminyl groups and is cytotoxic to the human colon cancer cell lines LS174t and SW1116

The lectin GS I-A4 binds to terminal alpha-N-acetylgalactosaminyl (GalNAc) groups (which include the Tn antigen), but not to the closely related tumor-associated epitope, sialylated Tn antigen. The lectin also precipitates asialo OSM, but not its native sialylated form. Lectin histochemistry with human colonic tissues showed that GS I-A4 specifically stained specimens of colon cancer and colonic tissues from individuals with FAP; however, normal colonic tissues from patients without colonic disease were rarely stained with this lectin. Glycoconjugates bound by GS I-A4 were observed on the surface membranes of 2 human colon cancer cell lines, LS174t and SW1116, when fluorescein isothiocyanate (FITC)-conjugated GS I-A4 was used. GS I-A4 was toxic to these 2 human colon cancer cell lines in monolayer culture. A dose-response study conducted using 10-160 micrograms/ml, of GS I-A4 demonstrated significant dose-related toxicity against LS174t and SW1116 cells. At concentrations > 80 micrograms/ml, > 99% of LS174t and > 90% of SW1116 cells were killed. Four mM GalNAc specifically inhibited the cytotoxic effect of GS I-A4 (p < 0.001), whereas 4mM N-acetylglucosamine (GlcNAc) had no effect. Two other lectins that recognize terminal alpha-GalNAc residues, DBA and LBL, were significantly less cytotoxic to the colon cancer cells than GS I-A4. In the light of these findings, we speculate that GS I-A4 may have potential use as a diagnostic agent against colorectal cancer.

Dolichos biflorus agglutinin binding in hereditary bowel cancer

Dolichos biflorus agglutinin (DBA) binds specifically to N-acetylgalactosamine (GalNAc), one of the 5 sugars contributing to the oligosaccharide component of human colorectal goblet cell mucin. DBA binds to goblet cells of the upper crypt and surface epithelium within the proximal colon and to the majority of goblet cells of the distal large bowel. DBA therefore serves as a marker of colorectal goblet cell differentiation with a distinct proximal to distal gradient effect. Previous reports indicate significant loss of DBA reactivity within morphologically normal colorectal mucosa derived from at-risk members of hereditary non-polyposis colorectal cancer (HNPCC) families. This finding could not be confirmed in the present study. Reduced binding was a relatively consistent finding in transitional mucosa, hyperplastic polyps and carcinoma, with adenomas displaying a more varied pattern of loss. Reduced binding by DBA may be explained by several mechanisms and may not necessarily reflect loss of GalNAc. The concept that lectins can be used to identify stepwise changes that occur during neoplastic evolution should not be accepted uncritically.