Synthesis of kappa light chains by cell lines containing an 8;22 chromosomal translocation derived from a male homosexual with Burkitt's lymphoma.

Three cell lines were derived from a homosexual patient with probable acquired immunodeficiency syndrome and Burkitt's lymphoma. The cell lines produce an unusual strain of Epstein-Barr virus which will both transform cord blood lymphocytes and induce early antigens in Raji cells. Translocations between chromosomes 8 and 22 have occurred in all three lines, but the cells synthesize immunoglobulin M with light chains of the kappa type, in contrast to the usual concordance between a translocation involving chromosome 22 and lambda chain synthesis. Both kappa genes and one lambda gene are rearranged. These findings indicate either that translocation may occur as a separate event from immunoglobulin gene rearrangement or that the proposed hierarchical sequence of immunoglobulin gene rearrangements is not always adhered to. The data also imply that in cells containing a translocation between the long arm of chromosome 8 and a chromosome bearing an immunoglobulin gene, alteration of cellular myc expression may occur regardless of the immunoglobulin gene that is expressed.

Flow microfluorometric analysis of P388 murine leukemia after administration of vincristine and maytansine in vivo.

Maytansine is a new drug undergoing clinical investigation. It has functional similarities to vincristine. Maytansine and vincristine were given to CDF1 mice with P388 leukemic ascites, and the cytokinetic response of the tumor cells was analyzed with a flow microfluorometer; mithramycin was used as the DNA fluorochrome. The results indicated a similar series of cytokinetic effects after administration of both drugs, though these effects were greater and more persistent after maytansine was given. Although both drugs produced some degree of multinucleation and endoreduplication, vincristine produced a discrete population of cells with a DNA content (fluorescence) equivalent to octoploidy (8C). Microscopy of the sorted 8C cells at 24 hours indicated 54% multinucleation and 33% mitotic figures. Most cells remained blocked in the G1-phase for at least 96 hours after administration of both drugs, which indicated that rapid DNA content distributions can be used to determine not only the effects of drugs on cell cycle distribution but also the duration of drug action.

Characterization of lymphoma-derived cell lines: comparison of cell lines positive and negative for Epstein-Barr virus nuclear antigen. I. Physical, cytogenetic, and growth characteristics.

Sixteen lymphoid cell lines were derived from patients with undifferentiated lymphoma of Burkitt's or non-Burkitt's type. They were obtained directly from tumor biopsies, from serous effusions, or from bone marrow. In 10 of the cell lines, the Epstein-Barr virus (EBV) nuclear antigen (EBNA) was undetectable; the remaining 6 lines were EBNA-positive (EB-pos). Of the 16 lines, 15 were aneuploid, with detectable chromosome "14q+ markers (11 had +8;14 translocations). These 15 lines, which included the EBNA-negative (EB-neg) lines, were believed to be of tumor cell origin. The remaining line consisted predominantly of diploid cells derived from normal lymphocytes, but some cells of tumor origin were present. Four EB-pos cell lines derived from EB-neg tumors had an aneuploid karyotype consistent with an origin from tumor cells (including no.8;14 translocation in two), which suggested that either tumor cells were infected with EBV in vitro or a tiny fraction of EB-pos tumor cells (or potential tumor cells) present in vivo gave rise to the predominant cell of the line. EB-neg B-cell lines and EB-pos cell lines established from undifferentiated lymphomas differed greatly. EB-neg lines had consistently smaller electronic mean cell volumes and narrow-angle light scatter than did EB-pos lines. This finding correlated with a lower nuclear:cytoplasmic ratio in EB-pos lines. EB-neg lines also had higher saturation cell densities than did EB-pos lines under standard culture conditions. The data indicate either that EBV influences the morphologic and physiologic characteristics of lymphoid cell lines or that EB-neg B-cell lines and EB-pos cell lines are derived ultimately from different lymphocyte subpopulations or that both may apply.

Flow microfluorimetric analysis of sensitive and resistant leukemia L1210 following 1-beta-D-arabinofuranosylcytosine in vivo.

Two groups of BALB/c X DBA/S F1 mice with sensitive and 1-beta-D-arabinofuranosylcytosine-resistant L1210 ascites, respectively, were used to study the cytokinetic effects of a single dose of 750 mg of 1-beta-D-arabinofuranosylcytosine per kg. Sequential DNA histograms, labeling indices, and mitotic indices were obtained from each of five mice at timed intervals from 0 to 72 hr. Each histogram was obtained by flow microfluorimetry, using the DNA-specific fluorochrome, mithramycin. The histograms were then integrated for cell cycle analysis. Cytokinetic perturbations occurred in both groups, but they were greater in the sensitive population where there was a relative accumulation of cells, mainly in early S phase, at 16 hr. This was followed by a relative depletion of S-phase cells. In the resistant population, there were relative accumulation of cells in early S phase at 8 and 24 hr and in mid-S phase at 32 hr, but there was no subsequent relative depletion of S-phase cells. The labeling index was rapidly reduced in both groups but was recovered in the resistant population within 4 hr. In the sensitive population, there was a transient rise in the labeling index at 8 and 16 hr. Sensitive and resistant populations of L1210 cells were rapidly and reliably distinguished by DNA content cell cycle analysis of a single sample taken between 24 and 72 hr following a large dose of 1-beta-D-arabinofuranosylcytosine. This technique has potential clinical application in the rational design and monitoring of chemotherapy.

Influence of microenvironmental pH on adriamycin resistance.

Resistance to Adriamycin (ADR) is frequently dependent upon enhanced efflux associated with the expression of the MDR1-encoded P membrane glycoprotein. Since enhanced expression of the MDR1 gene in ADR-resistant cells may be the result of spontaneous genetic mutation or amplification, it is presumed to be relatively stable and unalterable. Yet, reducing ADR efflux could increase sensitivity, and has been attempted using calcium channel blockers and other drugs. However, since the tumor cell microenvironment varies with respect to pH because of differences in vascularization, oxygenation, and metabolite clearance, the possibility exists that these factors could influence drug transport and the critical biochemical pathways which determine cytotoxicity, even in resistant cells. Using flow cytometric analysis of ADR fluorescence, the influx and efflux of 10 microM ADR dissolved in MES buffer (pH 6.5) and 4-(2-hydroxyethylene)-1-piperazineethanesulfonic acid buffer (pH 7.5 and 8.5) was measured in sensitive P388 and resistant P388/R84 cells in vitro. Substantially enhanced uptake of ADR was detected at alkaline pH in both cell populations, while the proportion of ADR-positive cells and the level of ADR uptake was decreased at lower pH. Acidification reduced ADR efflux, whereas alkalinization increased efflux when the uptake pH was 6.5 or 7.5. At uptake pH 8.5, the pH of the external buffer had little effect, even in resistant cells. In resistant cells in an alkaline microenvironment, ADR transport and retention were superior to that observed in sensitive cells in an acidic microenvironment. No differences were observed in ADR transport when the transmembrane pH gradient was equilibrated. These observations are especially relevant to the effect of ADR on tumor cell subpopulations that are acidic, and in which drug diffusion is inefficient. Efforts to alkalinize tumor cells prior to ADR therapy might reduce ADR resistance, even of genetic origin.

Expression of surface antigens during the cell cycle in different growth phases of American and African Burkitt's lymphoma cell lines.

We have studied the expression of five surface antigens in eight Burkitt's lymphoma cell lines during different phases of the cell cycle and in different growth phases (logarithmic and stationary). Cells were stained simultaneously for surface antigens (fluorescein coupled antibodies) and DNA content (propidium iodide), and dual parameter measurements were performed with a flow cytometer. Analysis of cells in specific cell cycle phases during log-phase growth revealed a 1.6-fold increase in surface antigen expression as cells passaged from G1 to G2/M. This is almost identical to the measured increase in cell surface area which occurs during passage of cells through the cell cycle and indicates that under optimal conditions surface antigen density is maintained during cell doubling. We also observed a consistent reduction, by about 50%, in the expression of surface IgM (mu), k-light chain, and B1 on the cell lines during a 5-day culture period. Cell lines that only weakly expressed surface IgM were found to have a more rapid decrease, and in such cell lines IgM was ultimately completely lost from the cell surface. In contrast, the expression of beta 2-microglobulin and HLA-ABC increased in some cell lines, whereas in others a significant decrease of both beta 2-microglobulin and HLA expression was demonstrated as the cells entered stationary growth phase. Decreased cell volume (and therefore surface area) associated with declining growth rate and fewer late S or G2/M cells could account for 20-30% of the observed reduction in surface IgM, k-light chain, and B1 expression, but the major decrement in fluorescence intensity was due to a reduction in the density of these surface antigens. Thus, the ability to maintain surface antigen densities is frequently lost in suboptimal culture conditions.

Microsatellite instability in aberrant crypt foci from human colons.

Aberrant crypt foci (ACF) are distinct microscopic lesions of the colon thought to be the earliest identifiable precursors of colon cancer. As precursors of colon cancer, ACF may contain mutations in genes that are altered early in colorectal tumorigenesis. Candidates for these genes include APC, K-Ras, and those of the DNA mismatch repair system. Some colon cancers with mutations in DNA mismatch repair genes are characterized by genomic instability at simple repeated sequences, also known as microsatellite instability. In this study, we analyzed 19 ACF (> or = 20 crypts/focus) and adjoining, microscopically normal colonic mucosa from 10 colon cancer patients for the presence of microsatellite instability. DNA from two ACF from two different patients displayed microsatellite instability. None of the DNA samples from normal mucosa displayed microsatellite instability. These observations support the role of ACF as a precursor to colon cancer and provide some evidence that mutations in DNA mismatch repair genes are early somatic events in colon cancer.

Drug-induced changes in DNA fluorescence intensity detected by flow microfluorometry and their implications for analysis of DNA content distributions.

Chicken erythrocytes, which contain less DNA than mammalian diploid cells, were used as an internal standard to control instrumental and staining variables during flow microfluorometric analysis. With the DNA stain, mithramycin, and with an EPICS II flow microfluorometer, ratios between the modal G1 fluorescence of experimental cells and that of chicken erythrocytes were determined. The results indicate that unperturbed cell populations of L1210 and HeLa cells in vitro and L1210 ascites cells in vivo have relatively stable fluorescence ratios, although there is a significant difference between the ratios of one L1210 cell line in vitro and another in vivo. In contrast, L1210 ascites treated in vivo with different schedules of cyclophosphamide and Adriamycin showed wide fluctuations in the fluorescence intensity ratios for 96 hr after treatment. Also, differences in the fluorescence ratios were observed between less advanced and more advanced L1210 ascites after treatment with the same schedule. These effects indicate an alteration in DNA staining with mithramycin, brought about by drug treatment that could seriously affect the interpretation of DNA histogram data. Nevertheless, changes in mithramycin staining may prove to be a very important probe to detect persistent drug effects.

pH dependence of mitomycin C-induced cross-linking activity in EMT6 tumor cells.

Mitomycin C (MC), a quinone-containing bioreductive alkylating agent, is cytotoxic to aerobic EMT6 tumor cells despite the fact that little bioactivation of MC occurs in EMT6 cell homogenates in the presence of O2. Because spontaneous activation of MC at acidic pH has been reported in chemical systems, aerobic EMT6 tumor cells were incubated in serum-free 2-(N-morpholino)ethanesulfonic acid or N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer at pH 5.7, 6.4, and 7.5 and exposed to MC for 2 h. As the extracellular pH was lowered, MC-induced DNA-DNA cross-linking, as measured by alkaline elution techniques, was enhanced. This effect was dose dependent at the three pH values tested. Measurement of intracellular pH by flow cytometric analysis indicated that the decrease in extracellular pH was paralleled by a fall in intracellular pH. The alteration of the extracellular pH had no effect on the colony-forming ability of control cells. The survival of cells treated with MC, however, was decreased as the pH was lowered. These data suggest that the intracellular and/or the extracellular pH is an important determinant of MC activity in aerobic EMT6 tumor cells.

Phagocytic properties of bone marrow fibroblasts.

Phagocytic activity has been observed in cultured marrow derived adherent cells (MDAC). Characterization studies indicate that these populations consist largely of collagen-producing fibroblasts, having failed to reveal markers associated with mononuclear phagocytes (MNP). Phagocytic activity by MDAC was therefore investigated. Characterization studies again failed to demonstrate an Fc receptor and confirmed that human MDAC synthesize collagen in vitro. Phagocytic activity against polystyrene microspheres was observed in 40% of MDAC. Control studies using P-8 and WI-38 fibroblasts yielded similar results. MDAC, P-8 and WI-38 fibroblasts were exposed to fluorescent microspheres and subsequently stained by immunofluorescence for type I collagen. Many cells were seen both to contain fluorescent particles and to stain positively for type I collagen. These results indicate that marrow derived fibroblasts, in common with fibroblasts from other sources, have phagocytic capability under appropriate conditions.

Measurement of cellular DNA mass by flow microfluorometry with use of a biological internal standard.

Use of a biological standard (chicken erythrocytes) mixed with experimental cell populations allows control of all variables in flow microfluorometric determination of DNA content. These variables include both staining and instrument procedures. In addition, the use of a biological standard allows determination of cellular DNA mass in unperturbed cell populations. DNA mass measured by FMF technique correlates closely with values reported in the literature that used biochemical techniques.

Electrolytic degradation of DNA fluorochromes during flow cytometric measurement of electronic cell volume.

Changes in flow cytometric measurement of DNA content can result from electrolytic chemical degradation of mithramycin, ethidium bromide, and propidium iodide during simultaneous measurement of electronic cell volume. Bench electrolysis also degrades these fluorochromes without changing the quantum yields, even when they are complexed to DNA. In the flow cytometer, electrolytic production of chlorine at the anode is the probable cause of this degradation, since exposure of these fluorochromes to chlorine gas produces the same effect. It is therefore advisable to measure the DNA content distribution alone before simultaneously measuring the DNA content and the electronic cell volume. If unavoidable effects on the DNA distribution are present, narrow forward-angle light scatter should be used as the cell size indicator during dual parameter measurements. Modifying instrument design by reversing electrode polarity might eliminate this problem.

Inhibition of progression of aberrant crypt foci and colon tumor development by vitamin E and beta-carotene in rats on a high-risk diet.

In this study we evaluated the effect of dietary administration of a high-fat, low-fiber diet (HRD) supplemented with Vitamin E, beta-carotene or folic acid and wheat bran on the growth of pre-existing aberrant crypt foci (ACF) that had been induced in Fischer-344 rats exposed to azoxymethane (AOM) and a HRD for 10 weeks. The rats (25 rats/dietary group) were fed a HRD for 2 weeks and were then given 2 subcutaneous injections of AOM (15 mg/kg body weight) while the rats continued on the HRD. After 6 weeks, rats were either maintained on the HRD (control) or crossed over to a HRD containing non-toxic levels of either Vitamin E, beta-carotene, folic acid or wheat bran. At 10, 14 and 18 weeks after the initiation of the experiment, 5 rats from each group were killed and the number of aberrant crypt foci (ACF) with different multiplicities were compared between groups. The dietary intervention was continued for 30 weeks to determine whether the inhibitory effect on the growth of ACF influenced the subsequent development of colonic tumors. The results revealed that vitamin E and beta-carotene caused a significant decrease in the number of ACF of different multiplicities when compared to the effect of the HRD alone. The decrease in the number of ACF due to folic acid and wheat bran appeared to be much smaller and in most cases was not significant. However, there was also a significant decrease in the incidence of colonic tumors and tumor multiplicity in both the vitamin E and beta-carotene groups that was not seen in the control group. The reports clearly demonstrates the ability of vitamin E and beta-carotene to inhibit the growth of colonic ACF, even in the presence of the strong promoting effect of high levels of dietary fat, using a post-initiation experimental design.

A rapid dual organ rat carcinogenesis bioassay for evaluating the chemoprevention of breast and colon cancer.

In this study we evaluated the effect of dietary administration of a high fat, low fiber diet (HRD) with or without 2% phytic acid (PA) on the development of mammary cancer and/or colon cancer in rats exposed to methylnitrosourea (MNU), azoxymethane (AOM) or MNU + AOM. The rats were fed a HRD alone or a HRD + 2% PA. At the end of week 2, the rats were given either a s.c. injection of MNU (50 mg/kg body wt) or one of normal saline (vehicle). At the end of weeks 3 and 4, the rats were given either a s.c. injection of AOM (15 mg/kg body wt per week) or one of normal saline (vehicle). Nine weeks after the injection of MNU or saline, 10 rats from each group were sacrificed and the mammary tumor incidence and the number of colonic aberrant crypt foci (ACF) were compared between different groups. The administration of different diets was continued for an additional 21 weeks and the mammary tumor and colon tumor incidence between different groups were compared. Results showed that rats injected with MNU alone did not develop ACF or colon tumors while those injected with AOM alone did not develop mammary tumors. Linear regression analysis of the number of ACF at 11 weeks versus colonic tumor incidence at 32 weeks, and the linear regression analysis of mammary tumor incidence at 11 weeks versus mammary tumor incidence at 32 weeks, both showed good linear correlation. These results demonstrate the potential value of the short term dual organ carcinogenesis bioassay for screening chemopreventive agents for their relative ability to inhibit the development of mammary cancer and/or colon cancer while on high risk diet.

Potential synergism between wheat bran and psyllium: enhanced inhibition of colon cancer.

In this study we compared the influence of high fat (20% w/w) diets that combine low levels of calcium (0.18% w/w) and low (1% w/w), medium (4% w/w) and high (8% w/w) levels of dietary fiber from wheat bran (WB), with high (8% w/w) levels of dietary fiber from psyllium (PS) alone or in various combinations with WB, on the induction of colon tumors in Fischer-344 rats following exposure to azoxymethane (AOM). The rats were fed the experimental diets for 2 weeks, and then were given two s.c. injections of AOM (15 mg/kg body wt./week). Twenty-three weeks following the first injection of AOM, the incidence of colon tumors in the different dietary groups (12 rats/group) was compared. The results clearly showed that by increasing the dietary fiber concentration of WB from 1 to 8% significantly reduced the number of colon tumors/group. When the influence of 8% dietary fiber from WB on the development of colon tumors was compared with that of PS (WB:PS = 0:100), no significant difference was observed. However, combinations of WB and PS showed a greater protective effect than either WB or PS alone, at comparable levels of dietary fiber. The 50:50 combination of WB and PS showed maximum protection, while 25:75 and 75:25 combinations both produced intermediate effects. None of the diets showed any significant effect on the normal growth of rats. The results indicate that WB and PS fiber alone, and to a greater degree in combination, can offer protection against colon cancer promoted by high fat, low calcium diets. Diets that include wheat bran in combination with psyllium could be an effective means of reducing colon cancer risk in human populations addicted to high risk western diets.

Absence of p53 gene mutations in rat colon carcinomas induced by azoxymethane.

The K-ras and p53 genes are two of the most frequently mutated genes found in the human colonic tumors. Since azoxymethane (AOM) induced rat colonic neoplasms are similar to human colonic tumors in their histological features and proliferation characteristics, the rat has been used as an experimental model to study the pathogenesis of colon cancer in humans. Although the presence of K-ras point mutations has been reported in AOM induced rat colonic tumors, there are no reports describing the frequency for mutation of the p53 gene in these tumors. In this study, colon adenocarcinomas induced in rats by AOM were examined for the presence of point mutations in exons 5-8 of the p53 gene, using a combination of single strand conformation (SSCP) analysis, immunohistochemistry and direct DNA sequencing. SSCP analysis showed no differences in banding patterns between the normal mucosa and any of the 20 adenocarcinomas analyzed. Nuclear p53 immunoreactivity was absent in all tumors examined. Since p53 point mutations predominate in malignant colonic tumors, five adenocarcinomas with the greatest local invasiveness were analyzed by direct DNA sequencing of exons 5-8 of the p53 gene. Direct DNA sequencing did not reveal mutations in any of the adenocarcinomas analyzed, within the coding region of p53 gene that were sequenced. The results from the present study indicate that point mutations in the p53 gene, at least in the coding region (exons 5-8) are not involved in the development of colon cancer induced by AOM in the rat.

Absence of p53 gene mutations in rat colon carcinomas induced through the synergistic interaction between methylazoxymethanol and X-irradiation.

p53 is one the most frequently mutated genes found in human colonic tumors. Because colonic neoplasms induced in rats by certain chemical carcinogens are similar to human colonic tumors in their histological features and proliferation characteristics, the rat has been used as an experimental model to study the pathogenesis of colon cancer. However, p53 mutations were not detected in the chemically induced colonic tumors analyzed for p53 mutations. X-irradiation has also been shown to induce colonic neoplasms in rats that resemble human colonic tumors histopathologically. Because the incidence of colonic tumors induced by methylazoxymethanol (MAM) in rats was shown to be enhanced by X-irradiation, we immunohistochemically analyzed these colonic carcinomas for the presence of p53 gene mutations. The immunohistochemical analyses clearly showed the absence of nuclear immunoreactivity in all ten tumors examined. The results from the present study indicate that point mutations in p53, at least in the coding region, are not involved in the development of colon cancer induced by the combination of MAM and X-irradiation. Our observations, together with the data from previous studies, further suggest that rat colon carcinogenesis, unlike human colon cancer, may not involve p53 mutation as an obligatory event.

Dietary fiber and the chemopreventive modelation of colon carcinogenesis.

Comparative international epidemiological data indicate that the difference between the highest and lowest colon cancer incidence is approximately 10-fold. This suggests that the dominant causes of colon cancer are environmental rather than genetic in origin, with the dominant environmental cause being the typical diet of Western industrialized countries. Many epidemiological and experimental studies have suggested an important role for dietary fiber in the prevention of colon cancer. Using the Fischer-344 rat as the experimental model, data clearly demonstrate a strong protective effect of a diet that is low in fat, high in fiber and high in calcium (low-risk diet). Such a diet prevents the development of both preneoplastic aberrant crypt foci (ACF) and colon tumors. Recent experiments have also demonstrated a direct relationship between a ras point mutation in ACF at different stages of rat colon carcinogenesis, and a ras point mutation that is subsequently present in colon tumors. Using wheat bran as the model dietary fiber source, its effects were compared to the effects of psyllium, phytic acid, vitamin E, beta-carotene, folic acid, alone or in combination, for their ability to prevent colon cancer in rats on high-risk Western-style diets. Our studies clearly demonstrated the ability of wheat bran to reduce ACF and colon tumors in rats that consumed high-fat, Western-style diets. Although phytic acid, which is a constituent of wheat bran, alone demonstrated strong cancer-preventive potential, our experiments provided evidence for the cancer-preventive effect of the crude fiber fraction that is independent of the effect of phytic acid. The synergistic combination of wheat bran with the soluble fiber psyllium led to enhanced protection; while the combination of wheat bran with beta-carotene showed only an additive effect. Beta-carotene appeared to show higher protection than wheat bran at an intake level that is nutritionally relevant to humans, suggesting the possibility of using beta-carotene to enhance the effects of dietary fiber in high-risk Western populations. Using ACF as an intermediate endpoint, it was also shown that vitamin E and beta-carotene appear to inhibit progression of ACF to colon cancer, while wheat bran and folic acid appeared to have weak cancer-preventive potential at this late stage of carcinogenesis. In conclusion, wheat bran alone, or in combination with psyllium, appears to have greater potential to inhibit earlier phases of carcinogenesis, while beta-carotene and vitamin E may also inhibit later stages of carcinogenesis. Despite considerable epidemiological and experimental evidence that increasing the fiber and lowering the fat content of the Western diet could substantially reduce the risk of cancer and heart disease, the real challenge is to find effective ways to educate and motivate people to overcome their intrinsic cultural resistance to such changes in their eating habits.

Inhibition by wheat bran cereals of the development of aberrant crypt foci and colon tumours.

As variation in both type of fibre and its physical properties can influence physiological effects, the effects of different dietary levels (1, 4, 8%, w/w) of unprocessed wheat bran (WB) were compared with those of two of its processed commercial formulations used in breakfast cereals, on the formation of aberrant crypt foci (ACF) and colon tumours in Fischer 344 rats following azoxymethane (AOM) administration. All diets were high in fat (20 g/100 g) and low in calcium (0.2%, w/w). The rats were fed the experimental diets for 2 wk before receiving two sc injections of AOM (15 mg/kg body weight/wk). 8 wk following the first injection of AOM, five rats per group were killed and the formation of ACF was measured. 23 wk following the first injection of AOM, 12 rats per group were killed and the colon tumour incidence in different dietary groups was measured. The results showed that increasing the dietary concentration of fibre from 1 to 8% (w/w), using all the wheat bran formulations, significantly reduced the number of ACF per rat. None of the diets showed any significant effect on the normal growth of rats. No statistically significant differences were observed between the protective properties of WB and the two commercial formulations under investigation in terms of the reduction of the number of ACF, or in terms of the reduction of the colon adenocarcinoma incidence. The results suggest that wheat bran and its two commercial formulations can offer protection against colon cancer even when they are consumed with a high-fat/low-calcium diet. The addition of any of these formulations of wheat bran fibre is likely to be equally effective in the prevention of colon cancer in human populations that habitually consume high-fat/low-fibre Western-style diets.

Fecal bile acid excretion and composition in response to changes in dietary wheat bran, fat and calcium in the rat.

The effect and possible interactive influence of different dietary amounts of wheat bran, fat and calcium on the fecal excretion, concentration and composition of bile acids was studied in Fischer-344 rats. The fecal bile acids were analyzed using gas-liquid chromatography. Dietary wheat bran increased both total bile acid excretion and fecal weight without changes in fecal bile acid concentration. The proportion of fecal hyodeoxycholic acid decreased with increasing dietary fiber, whereas that of lithocholic and deoxycholic acids increased significantly with fiber intake. The percent content of fecal chenodeoxycholic acid did not change. Increasing dietary fat led to an increase in bile acid excretion without changes in either fecal weight or bile acid concentration. In contrast, the level of dietary calcium did not affect the total excretion of bile acids. However, since calcium increased the fecal weight, it consequently diluted bile acids and decreased their fecal concentration. Dietary fat and calcium had no influence on fecal bile acid composition. There were no interactive effects of wheat bran, fat and calcium on fecal bile acids. The finding in this study that dietary fiber, fat and calcium induce significant changes in fecal bile acids may be of relevance to the potential of bile acids to promote carcinogenesis.