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Cell turnover and colon tumor development
PREVENTIVE
MEDICINE
16, 580-585 (1987)
Cell Turnover
and Colon
ELEANOR Memorial
Sloan-Kettering
Cancer
Tumor
E. DESCHNER, Center,
Development’ PH.D.
1275 York Avenue,
New
York,
New
York
10021
The proliferative characteristics of the large bowel are determined genetically and can vary over a wide range, the lower range being resistant to chemically induced tumors and the upper range expressing susceptibility. Basically, the colon has a relatively high level of cell renewal. It can be further elevated or depressed by a number of dietary and environmental conditions. A hyperproliferative state has been induced by the presence of carrageenan, Citrobacterfreundii, nonspecific injury, or dietary factors such as high levels of bile acids. The effect of high proliferation levels is to produce more S-phase cells, which are sensitive to DNA damage, to increase the risk of neoplastic transformation and to shorten the tumor latency period. In animal models, hyperactivity has meant enhanced tumor incidence. A hypoproliferative state has been induced in the colon of man and mouse. Experimentally, the net effect of lower proliferative levels has been to reduce colon tumor incidence. It remains to be determined whether clinical trials involving hypoproliferation can be maintained chronically and are an effective means of reducing colon tumor incidence in high-risk groups. 0 1987 Academic Press, Inc.
INTRODUCTION
Our understanding of cell proliferation and cancer development has been built on data emerging from many different systems. Chemical hepatogenesis studies have shown that tumor yield is increased significantly by the stimulation of cell division following partial hepatectomy (4). Unlike the liver, the colonic mucosa is characterized by a relatively high level of spontaneous cell proliferation. It thereby complies easily with the requirement that cell proliferation occur if a tissue is to express tumor development and explains very succinctly why, if a malignant cell should arise in the mucosa, the probability is great that a cancer will develop. Factors affecting that probability relate to the genetic character of the mucosa, where or in which segment of the colon the mutation arises, and the environmental conditions which surround it. TISSUE CHARACTERISTICS
Kinetic analysis of the distal colon of several mouse strains with variable susceptibility of 1,Zdimethylhydrazine (DMH) and methylazoxymethanol has revealed a positive correlation between the proliferative characteristics [the labeling index (LI) and distribution of DNA-synthesizing cells] and their degree of tumor incidence. SWR and CFl mice with almost 100% tumor yields had high LIs and wide proliferation compartments (PCs) whereas strains with a low incidence of neoplasia had low LIs and narrow PCs (Fig. 1) (10, 11). The impact of a wide ’ Presented at the Workshop on New Developments on Dietary Fat and Fiber in Carcinogenesis (Optimal Types and Amounts of Fat or Fiber), American Health Foundation, New York, March 25-26, 1986. 580 0091-7435187 $3.00 Copyright All rights
0 1987 by Academic Press, Inc. of reproduction in any form reserved.
CELL TURNOVER CONTROL
MICE
AND NEOPLASIA TREATED
581
MICE
FIG. 1. The control labeling index (LI) values of DMH-sensitive CFl and DMH-resistant AKR mice and the effect of treatment with 10% dietary degraded carrageenan and 6 or 26 injections of DMH (20 mg/kg body wt) on mucosal LI of these strains. In the carrageenan model for inflammatory bowel disease, an extremely large elevation in LI has been induced in CFl mice as has been created when 26 weekly injections of DMH were delivered. Less hyperactivity has been induced with 6 DMH injections and even AKR mice show a widening of the range of LI values, but not nearly so large as that of the DMH-susceptible CFl strain. The number of mice in each group appears in parentheses. Values are given as the means -+ SD.
PC, a high frequency of S-phase cells in the middle one-third of the crypt, and dividing cells close to the region of differentiation would be to maximize the opportunity for S-phase cells or incompletely differentiated cells to escape into the upper regions of the gland. A continued high level of cell proliferation increases the likelihood of a further alteration in DNA character to occur, which can then allow for adenoma development in this upper one-third of the crypt (6). In addition to this difference expressed within the same area of the colon, differences have been found among the various segments of the colon. Those areas with a faster cell cycle time and higher LI, i.e., distal colon, have higher tumor frequencies than areas that turn over more slowly, i.e., ascending colon (27, 31, 32). FACTORS INFLUENCING PROLIFERATION
There are a number of situations described in the literature that alter the proliferative character of the mucosa and affect colon cancer incidence. Four of these situations relate to the induction of a hyperproliferative state. The net effect of this condition within the colon has been to enhance cancer incidence. Hyperproliferation
Providing rats with undegraded treating them with azoxymethane
carrageenan in their food for 2 weeks prior to or methylnitrosourea effectively raised tumor
582
ELEANOR
E. DESCHNER
incidence from 57-68% to 100% in both groups (34). Degraded carrageenan alone has been reported to induce ulcerative colitis (24), metaplasia (14), and even adenomas and adenocarcinomas when given for 24 months (33). Ten percent degraded carrageenan in the drinking water nearly doubled the LI in both proximal and distal colon, thus providing many more cells at the most sensitive phase for carcinogen-induced neoplastic initiation (16) (Fig. 1). Chronic ingestion of the complex polysaccharide which induces hyperplasia (in addition to multiple carcinogen injections) would then allow the fixation and transmittal of the altered genome to proceed extremely rapidly, thus explaining the higher tumor incidence data in azoxymethane- and methylnitrosourea-treated rats. Another case of nonspecific injury involved placing a suture into the cecum of rats prior to injection of DMH. Tumor incidence of 87-96% occurred in the sutured animals compared with only 23% in the DMH control group (27). Clearly, under the influence of the hyperproliferative state, a greater number of DMH-initiated cells were created in the mucosa of the injured rodent, the latent tumor period was compressed, and a higher incidence of damage was expressed. A similar hyperplastic stimulus has been induced in mice by rectal instillation of Citrobacter freundii (1). Under ordinary conditions, early neoplastic lesions arise with an incidence of 70% 3 months after DMH initiation, but in the presence of the transmissable hyperplastic stimulus, these lesions were detectable in equal numbers after only 1 month. Thus, the diffuse mucosal hyperplasia promoted the DMH-initiated cells, thereby significantly reducing the latent period and increasing the expression of neoplasia. The last example of a hyperproliferative state in the colonic mucosa relates to the effect of diet, specifically the effect of bile acids and fiber on epithelial cell proliferation. The damaging detergent action of cholic acid (5, 8) and the abrasive action of wheat bran (20, 21) cause massive cell loss and compensatory cell replacement. Dietary intake prior to and during carcinogen treatment with either agent resulted in significantly greater colonic tumor yield, again suggesting increased numbers of initiated cells being produced and promoted when proliferation was stimulated. The hyperproliferative state then can accomplish several important activities, the end result of which is to elevate tumor yield. If we assume tumor development to be at least a two-step process (25), then by increasing the number of S-phase cells in the colon one can significantly increase the number of neoplastitally initiated cells produced with a chemical carcinogen. A hyperproliferative state can also effectively reduce or compress the time between the time of carcinogen delivery and the appearance of the tumor. Moreover a hyperactive state following a carcinogen treatment can increase the risk for the appearance of the neoplastic transformed cell. Hypoproliferation
This condition would be marked either by a restoration of a more normal LI or by one lower than that normally observed for that colon. A number of dietary agents, i.e., ascorbic acid (7), p-sitosterol(9), and butylated hydroxyanisole (12), have suppressed the characteristic LI for the distal colon of rodents. These sub-
CELL TURNOVER
AND NEOPLASIA
583
stances, in addition to reducing LI, slowed migration of epithelial cells to the surface of crypts, compressed the PC and, most importantly, decreased carcinogen-induced tumorigenesis (28, 29, 35). When provided prior to carcinogen treatment, these nutrients therefore acted to suppress the number of susceptible or sensitive cells capable of being initiated, extended or prolonged the period before a tumor could develop and, lastly, decreased the risk that a neoplastic transformed cell will arise (Fig. 2). HUMAN SITUATIONS
A few additional remarks may be made about some populations that have been examined for kinetic characteristics and that provide further support for the foregoing discussion. Both ends of the proliferative spectrum have received attention. Seventh-Day Adventist vegetarians have perhaps one of the lowest colon cancer rates (26), suggesting that their diet may be instrumental in inhibiting or preventing cancer. The colonic mucosa of these individuals has an extremely low LI and may represent the best example of a hypoproliferative state and its benefits with regard to colon cancer incidence (23). At the opposite end of the proliferative scale, we have the inflammatory bowel disease group. Nonspecific hyperplasia is a characteristic of both ulcerative colitis and Crohn’s disease (19). Both diseases are marked by an increased risk for colon cancer, with risk increasing with the disease duration (15). Labeling indices of 13-26% have been demonstrated in these patients compared with 5- 10% for noncolitics (2, 13, 30), again suggesting that high levels of colonic epithelial cell proliferation increase the risk for the expression of colon cancer. Drug therapy of ulcerative colitis patients has brought about remission of their clinical symptoms, but their cell renewal levels tend to remain high (30). Whether dietary means can reduce proliferative values and indirectly lower risk for adenomas and cancer development remains to be assessed. In the same vein, if colonic epithelial cells in familial polyposis patients can be thought to be “initiated” cells (18), then prevention of a hyperproliferative state HYPOPROLIFERATIVE MUCOSAL STATE I
BW.cokiwn -
Small S Phase Population
NORMAL MUCOSAL STATE
~tirobocter f -
HY PERPROLIFERATIVE MUCOSAL STATE I
Large S Phase Population
FIG. 2. Interaction of diet/environment and heredity. The basic indigenous level of proliferation in the colon may vary over a wide range. The upper range would be more susceptible to tumor formation than would the lower range. Dietary and environmental conditions interact with this basic level, inducing either higher or lower values. High labeling indices (LIs) increase the number of susceptible S-phase cells, escalate the risk for mutation to occur and shorten tumor latency time. Lower LIs reduce risk for mutation by depressing the number of S-phase cells as well as lengthening the tumor latency period.
584
ELEANOR
E. DESCHNER
may successfully prolong tumor latency periods not only for adenoma formation but also for reducing the risk of malignant transformation. With this goal in mind, chemopreventive programs have been established. Chronic ascorbic acid supplementation of patients has depressed the LI of rectal epithelial cells (3), and acute calcium intake in familial colon cancer has produced similar results (22). While the results of clinical studies designed to control colon cancer incidence in high-risk groups by dietary means are not yet available, there are associations that suggest this to be a reasonable approach. Measures that would depress cell proliferation could slow the participation of some initiated cells and their propagation, resulting, at the least, in a longer latency period before neoplasia arises and possibly a reduced tumor incidence. REFERENCES 1. Barthold, S. W., and Jonas, A. M. Morphogenesis of early 1,2-dimethylhydrazine induced lesions and latent period reduction of colon carcinogenesis in mice by a variant of Cirrobacrerfieundii. Cancer Res. 31, 4352-4360 (1977). 2. Bleiberg, H., Mainguet, P., Galand, I?, Chretien, J., and DuPont-Mairesse, N. Cell renewal in human rectum: In vitro autoradiographic study on active ulcerative colitis. Gastroenterology 60, 851-855 (1970). 3. Bussey, H. J. R., DeCosse, J. J., Deschner, E. E., Eyers, A. A., Lesser, M., Morson, B. C., Ritchie, S. M., Thomson, J. P. S., and Wadsorth, J. A randomized trial of ascorbic acid on polyposis coli. Cancer 50, 1434-1439 (1982). 4. Cayama, E., Tsuda, H., Sarma, D. S. R., and Farber, E. Initiation of chemical carcinogenesis requires cell proliferation. Nature (London) 275, 60-62 (1978). 5. Cohen, B. I., Raicht, R. F., Deschner, E. E., Takahashi, M., Sarwal, A. N., and Fazzini, E. Effect of cholic acid feeding on N-methyl-N-nitrosourea induced colon tumors and cell kinetics in rats. J. Nut/. Cancer Inst. 64, 573-578 (1980). 6. Descher, E. E. Early proliferative changes in gastrointestinal neoplasia. Amer. J. Gastroenterol. 77, 207-211 (1982). 7. Deschner, E. E., Alcock, N., Okamura, T., DeCosse, J. J., and Sherlock, P. Tissue concentrations and proliferative effects of massive doses of ascorbic acid in the mouse. Nutr. Cancer 4, 241-246 (1983). 8. Deschner, E. E., Cohen, B. I., and Raicht, R. F. Acute and chronic effect of dietary cholic acid on colonic epithelial cell proliferation. Digestion 21, 290-296 (1981). 9. Deschner, E. E., Cohen, B. I., and Raicht, R. E Kinetics of the protective effect of beta sitosterol against MNU induced colonic neoplasia. .Z. Cancer Res. Clin. Oncol. 103, 49-54 (1982). 10. Deschner, E. E., Long, F. C. Hakissian, M., and Herrmann, S. L. Differential susceptibility of AKR, C57BL/6J and CFl mice to 1,2-dimethylhydrazine induced colonic tumor formation predicted by proliferative characteristics of colonic epithelial cells. J. Natl. Cancer Inst. 70, 279-282 (1983). 11. Deschner, E. E., Long, E C., Hakissian, M., and Cupo, S. H. Differential susceptibility of inbred mouse strains forecast by acute colonic proliferative response to methylazoxymethanol. .Z. Nut/. Cancer Inst. 72, 195-198 (1984). 12. Deschner, E. E., and Wattenberg, L. W. The proliferative effect of butylated hydroxyanisole on MAM treated colonic mucosa. Cancer Lett. 16, 197-202 (1982). 13. Eastwood, G. L., and Trier, J. S. Epithelial cell renewal in cultured rectal biopsies in ulcerative colitis. Gastroenterology 64, 383-390 (1973). 14. Fabian, R. J., Abraham, R., Coulson, F., and Golberg, L. Carrageenan-induced squamous metaplasia of the rectal mucosa in the rat. Gastroenterology 65, 265-276 (1974). 15. Farmer, R. G., Hawk, W. A., and Tumbull, R. B., Jr. Carcinoma associated with mucosal ulcerative colitis and with transmural colitis and enteritis (Crohn’s disease). Cancer 28, 289-292 (1971).
CELL TURNOVER
AND NEOPLASIA
585
16. Fath, R. B., Deschner, E. E., Winawer, S. J., and Dworkin, B. M. Degraded carrageenan-induced colitis in CFl mice: A clinical, histopathological and kinetic analysis. Digestion 29, 197-203 (1984). 17. Fenoglio, C. M., and Pascal, R. R. Adenomatous epithelium, intraepithelial anaplasia and invasive carcinoma in ulcerative colitis. Dig. Dis. 18, 556-562 (1973). 18. Friedman, E., Gillin, S., and Lipkin, M. 12-0-tetradeanoylphorbol-13-acetate stimulation of DNA synthesis in cultured preneoplastic familial polyposis colonic epithelial cells but not in normal colonic epithelial cells. Cancer Res. 44, 4078-4086 (1984). 19. Greenstein, A. J., Sachar, D. B., Smith, H., Janowitz, H. D., and Aufses, A. H. Patterns of neoplasia in Crohn’s disease and ulcerative colitis. Cancer 46, 403-407 (1980). 20. Jacobs, L. R., and Schneeman, B. 0. Effects of dietary wheat bran on rat colonic structure and mucosal cell growth. J. Nufr. 111, 798-803 (1981). 21. Jacobs, L. R., and White, F. A. Modulation of mucosal cell proliferation in the intestine of rats fed a wheat bran diet. Amer. J. C/in. Nutr. 37, 945-953 (1983). 22. Lipkin, M., and Newmark, H. Effect of added dietary calcium on colonic epithelial cell proliferation in subjects at high risk for familial colonic cancer. New Engl. J. Med. 313, 1381- 1384 (1985). 23. Lipkin, M., Uehara, K., Winawer, S., Sanchez, A., Bauer, C., Phillips, R., Lynch, H. T., Blattner, W. A., and Fraumeni, J. F., Jr. Seventh-Day Adventist vegetarians have a quiescent proliferative activity in colonic mucosa. Cancer Lett. 26, 139-144 (1985). 24. Marcus, R., and Watt, J. Colonic ulceration in young rats fed degraded carrageenan. Lancet 2, 765-766 (1971). 25. Maskens, A. P. Mathematical models of carcinogenesis and tumor growth in an experimental rat colon adenocarcinoma, in “Gastrointestinal Cancer” (M. Lipkin and R. A. Good, Eds.), p. 361. Plenum, New York, 1978. 26. Phillips, R. L., Kuzma, J. W., and Lotz, T. M. Cancer mortality among comparable members versus nonmembers of the Seventh-Day Adventist church, in “Cancer Incidence in Defined Populations,” Banbury Report 4 (J. Cairns, J. L. Lyon, and M. Skolnick, Eds.), p. 93. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 1980. 27. Pozharisski, K. M. The significance of nonspecific injury for colon carcinogenesis in rats. Cancer Res. 3.5, 3824-3830 (1975). 28. Raicht, R. F., Cohen, B. I., Fazzini, E. P., Sarwal, A. N., and Takahashi, M. Protective effect of plant sterols against chemically induced colon tumors in rats. Cancer Res. 40, 403-405 (1980). 29. Reddy, B. S., and Hirota, N. Effect of dietary ascorbic acid on 1,2-dimethylhydrazine-induced colon cancer in rats. Fed. Proc. 38, 174 (1979). 30. Serafine, E. P., Kirk, A. P., and Chambers, T. J. Rate and pattern of epithelial cell proliferation in ulcerative colitis. Gut 22, 648-652 (1981). 31. Sunter, J. P., Appleton, D. R., de Rodriguez, M. S. B., Wright, N. A., and Watson, A. J. A comparison of cell proliferation at different sites within the large bowel of the mouse. J. Anat. 129, 833-842 (1979). 32. Sunter, J. P., Watson, A. J., Wright, N. A., and Appleton, D. R. Cell proliferation at different sites along the length of the rat colon. Virchows Arch. B Cell Pathol. 32, 75-87 (1979). 33. Wakabayashi, K., Inagaki, T., Fujimoto, Y., and Fukuda, Y. Induction by degraded carrageenan of colorectal tumors in rats. Cancer Lett. 4, 171-176 (1978). 34. Watanabe, K., Reddy, B. S., Wong, C. O., and Weisburger, J. H. Effect of dietary undegraded carrageenan on colon carcinogenesis in F344 rats treated with azomethane or methylnitrosurea. Cancer Res. 38, 4427-4430 (1978). 35. Wattenberg, L. W., and Sparnins, V. L. Inhibitory effects of butylated hydroxyanisole on methylazoxymethanol acetate-induced neoplasia of the large intestine and on nicotinamide adenine dinucleotide-dependent alcohol dehydrogenase activity in mice. J. Nut/. Cancer Inst. 63, 219-222 (1979).
MEDICINE
16, 580-585 (1987)
Cell Turnover
and Colon
ELEANOR Memorial
Sloan-Kettering
Cancer
Tumor
E. DESCHNER, Center,
Development’ PH.D.
1275 York Avenue,
New
York,
New
York
10021
The proliferative characteristics of the large bowel are determined genetically and can vary over a wide range, the lower range being resistant to chemically induced tumors and the upper range expressing susceptibility. Basically, the colon has a relatively high level of cell renewal. It can be further elevated or depressed by a number of dietary and environmental conditions. A hyperproliferative state has been induced by the presence of carrageenan, Citrobacterfreundii, nonspecific injury, or dietary factors such as high levels of bile acids. The effect of high proliferation levels is to produce more S-phase cells, which are sensitive to DNA damage, to increase the risk of neoplastic transformation and to shorten the tumor latency period. In animal models, hyperactivity has meant enhanced tumor incidence. A hypoproliferative state has been induced in the colon of man and mouse. Experimentally, the net effect of lower proliferative levels has been to reduce colon tumor incidence. It remains to be determined whether clinical trials involving hypoproliferation can be maintained chronically and are an effective means of reducing colon tumor incidence in high-risk groups. 0 1987 Academic Press, Inc.
INTRODUCTION
Our understanding of cell proliferation and cancer development has been built on data emerging from many different systems. Chemical hepatogenesis studies have shown that tumor yield is increased significantly by the stimulation of cell division following partial hepatectomy (4). Unlike the liver, the colonic mucosa is characterized by a relatively high level of spontaneous cell proliferation. It thereby complies easily with the requirement that cell proliferation occur if a tissue is to express tumor development and explains very succinctly why, if a malignant cell should arise in the mucosa, the probability is great that a cancer will develop. Factors affecting that probability relate to the genetic character of the mucosa, where or in which segment of the colon the mutation arises, and the environmental conditions which surround it. TISSUE CHARACTERISTICS
Kinetic analysis of the distal colon of several mouse strains with variable susceptibility of 1,Zdimethylhydrazine (DMH) and methylazoxymethanol has revealed a positive correlation between the proliferative characteristics [the labeling index (LI) and distribution of DNA-synthesizing cells] and their degree of tumor incidence. SWR and CFl mice with almost 100% tumor yields had high LIs and wide proliferation compartments (PCs) whereas strains with a low incidence of neoplasia had low LIs and narrow PCs (Fig. 1) (10, 11). The impact of a wide ’ Presented at the Workshop on New Developments on Dietary Fat and Fiber in Carcinogenesis (Optimal Types and Amounts of Fat or Fiber), American Health Foundation, New York, March 25-26, 1986. 580 0091-7435187 $3.00 Copyright All rights
0 1987 by Academic Press, Inc. of reproduction in any form reserved.
CELL TURNOVER CONTROL
MICE
AND NEOPLASIA TREATED
581
MICE
FIG. 1. The control labeling index (LI) values of DMH-sensitive CFl and DMH-resistant AKR mice and the effect of treatment with 10% dietary degraded carrageenan and 6 or 26 injections of DMH (20 mg/kg body wt) on mucosal LI of these strains. In the carrageenan model for inflammatory bowel disease, an extremely large elevation in LI has been induced in CFl mice as has been created when 26 weekly injections of DMH were delivered. Less hyperactivity has been induced with 6 DMH injections and even AKR mice show a widening of the range of LI values, but not nearly so large as that of the DMH-susceptible CFl strain. The number of mice in each group appears in parentheses. Values are given as the means -+ SD.
PC, a high frequency of S-phase cells in the middle one-third of the crypt, and dividing cells close to the region of differentiation would be to maximize the opportunity for S-phase cells or incompletely differentiated cells to escape into the upper regions of the gland. A continued high level of cell proliferation increases the likelihood of a further alteration in DNA character to occur, which can then allow for adenoma development in this upper one-third of the crypt (6). In addition to this difference expressed within the same area of the colon, differences have been found among the various segments of the colon. Those areas with a faster cell cycle time and higher LI, i.e., distal colon, have higher tumor frequencies than areas that turn over more slowly, i.e., ascending colon (27, 31, 32). FACTORS INFLUENCING PROLIFERATION
There are a number of situations described in the literature that alter the proliferative character of the mucosa and affect colon cancer incidence. Four of these situations relate to the induction of a hyperproliferative state. The net effect of this condition within the colon has been to enhance cancer incidence. Hyperproliferation
Providing rats with undegraded treating them with azoxymethane
carrageenan in their food for 2 weeks prior to or methylnitrosourea effectively raised tumor
582
ELEANOR
E. DESCHNER
incidence from 57-68% to 100% in both groups (34). Degraded carrageenan alone has been reported to induce ulcerative colitis (24), metaplasia (14), and even adenomas and adenocarcinomas when given for 24 months (33). Ten percent degraded carrageenan in the drinking water nearly doubled the LI in both proximal and distal colon, thus providing many more cells at the most sensitive phase for carcinogen-induced neoplastic initiation (16) (Fig. 1). Chronic ingestion of the complex polysaccharide which induces hyperplasia (in addition to multiple carcinogen injections) would then allow the fixation and transmittal of the altered genome to proceed extremely rapidly, thus explaining the higher tumor incidence data in azoxymethane- and methylnitrosourea-treated rats. Another case of nonspecific injury involved placing a suture into the cecum of rats prior to injection of DMH. Tumor incidence of 87-96% occurred in the sutured animals compared with only 23% in the DMH control group (27). Clearly, under the influence of the hyperproliferative state, a greater number of DMH-initiated cells were created in the mucosa of the injured rodent, the latent tumor period was compressed, and a higher incidence of damage was expressed. A similar hyperplastic stimulus has been induced in mice by rectal instillation of Citrobacter freundii (1). Under ordinary conditions, early neoplastic lesions arise with an incidence of 70% 3 months after DMH initiation, but in the presence of the transmissable hyperplastic stimulus, these lesions were detectable in equal numbers after only 1 month. Thus, the diffuse mucosal hyperplasia promoted the DMH-initiated cells, thereby significantly reducing the latent period and increasing the expression of neoplasia. The last example of a hyperproliferative state in the colonic mucosa relates to the effect of diet, specifically the effect of bile acids and fiber on epithelial cell proliferation. The damaging detergent action of cholic acid (5, 8) and the abrasive action of wheat bran (20, 21) cause massive cell loss and compensatory cell replacement. Dietary intake prior to and during carcinogen treatment with either agent resulted in significantly greater colonic tumor yield, again suggesting increased numbers of initiated cells being produced and promoted when proliferation was stimulated. The hyperproliferative state then can accomplish several important activities, the end result of which is to elevate tumor yield. If we assume tumor development to be at least a two-step process (25), then by increasing the number of S-phase cells in the colon one can significantly increase the number of neoplastitally initiated cells produced with a chemical carcinogen. A hyperproliferative state can also effectively reduce or compress the time between the time of carcinogen delivery and the appearance of the tumor. Moreover a hyperactive state following a carcinogen treatment can increase the risk for the appearance of the neoplastic transformed cell. Hypoproliferation
This condition would be marked either by a restoration of a more normal LI or by one lower than that normally observed for that colon. A number of dietary agents, i.e., ascorbic acid (7), p-sitosterol(9), and butylated hydroxyanisole (12), have suppressed the characteristic LI for the distal colon of rodents. These sub-
CELL TURNOVER
AND NEOPLASIA
583
stances, in addition to reducing LI, slowed migration of epithelial cells to the surface of crypts, compressed the PC and, most importantly, decreased carcinogen-induced tumorigenesis (28, 29, 35). When provided prior to carcinogen treatment, these nutrients therefore acted to suppress the number of susceptible or sensitive cells capable of being initiated, extended or prolonged the period before a tumor could develop and, lastly, decreased the risk that a neoplastic transformed cell will arise (Fig. 2). HUMAN SITUATIONS
A few additional remarks may be made about some populations that have been examined for kinetic characteristics and that provide further support for the foregoing discussion. Both ends of the proliferative spectrum have received attention. Seventh-Day Adventist vegetarians have perhaps one of the lowest colon cancer rates (26), suggesting that their diet may be instrumental in inhibiting or preventing cancer. The colonic mucosa of these individuals has an extremely low LI and may represent the best example of a hypoproliferative state and its benefits with regard to colon cancer incidence (23). At the opposite end of the proliferative scale, we have the inflammatory bowel disease group. Nonspecific hyperplasia is a characteristic of both ulcerative colitis and Crohn’s disease (19). Both diseases are marked by an increased risk for colon cancer, with risk increasing with the disease duration (15). Labeling indices of 13-26% have been demonstrated in these patients compared with 5- 10% for noncolitics (2, 13, 30), again suggesting that high levels of colonic epithelial cell proliferation increase the risk for the expression of colon cancer. Drug therapy of ulcerative colitis patients has brought about remission of their clinical symptoms, but their cell renewal levels tend to remain high (30). Whether dietary means can reduce proliferative values and indirectly lower risk for adenomas and cancer development remains to be assessed. In the same vein, if colonic epithelial cells in familial polyposis patients can be thought to be “initiated” cells (18), then prevention of a hyperproliferative state HYPOPROLIFERATIVE MUCOSAL STATE I
BW.cokiwn -
Small S Phase Population
NORMAL MUCOSAL STATE
~tirobocter f -
HY PERPROLIFERATIVE MUCOSAL STATE I
Large S Phase Population
FIG. 2. Interaction of diet/environment and heredity. The basic indigenous level of proliferation in the colon may vary over a wide range. The upper range would be more susceptible to tumor formation than would the lower range. Dietary and environmental conditions interact with this basic level, inducing either higher or lower values. High labeling indices (LIs) increase the number of susceptible S-phase cells, escalate the risk for mutation to occur and shorten tumor latency time. Lower LIs reduce risk for mutation by depressing the number of S-phase cells as well as lengthening the tumor latency period.
584
ELEANOR
E. DESCHNER
may successfully prolong tumor latency periods not only for adenoma formation but also for reducing the risk of malignant transformation. With this goal in mind, chemopreventive programs have been established. Chronic ascorbic acid supplementation of patients has depressed the LI of rectal epithelial cells (3), and acute calcium intake in familial colon cancer has produced similar results (22). While the results of clinical studies designed to control colon cancer incidence in high-risk groups by dietary means are not yet available, there are associations that suggest this to be a reasonable approach. Measures that would depress cell proliferation could slow the participation of some initiated cells and their propagation, resulting, at the least, in a longer latency period before neoplasia arises and possibly a reduced tumor incidence. REFERENCES 1. Barthold, S. W., and Jonas, A. M. Morphogenesis of early 1,2-dimethylhydrazine induced lesions and latent period reduction of colon carcinogenesis in mice by a variant of Cirrobacrerfieundii. Cancer Res. 31, 4352-4360 (1977). 2. Bleiberg, H., Mainguet, P., Galand, I?, Chretien, J., and DuPont-Mairesse, N. Cell renewal in human rectum: In vitro autoradiographic study on active ulcerative colitis. Gastroenterology 60, 851-855 (1970). 3. Bussey, H. J. R., DeCosse, J. J., Deschner, E. E., Eyers, A. A., Lesser, M., Morson, B. C., Ritchie, S. M., Thomson, J. P. S., and Wadsorth, J. A randomized trial of ascorbic acid on polyposis coli. Cancer 50, 1434-1439 (1982). 4. Cayama, E., Tsuda, H., Sarma, D. S. R., and Farber, E. Initiation of chemical carcinogenesis requires cell proliferation. Nature (London) 275, 60-62 (1978). 5. Cohen, B. I., Raicht, R. F., Deschner, E. E., Takahashi, M., Sarwal, A. N., and Fazzini, E. Effect of cholic acid feeding on N-methyl-N-nitrosourea induced colon tumors and cell kinetics in rats. J. Nut/. Cancer Inst. 64, 573-578 (1980). 6. Descher, E. E. Early proliferative changes in gastrointestinal neoplasia. Amer. J. Gastroenterol. 77, 207-211 (1982). 7. Deschner, E. E., Alcock, N., Okamura, T., DeCosse, J. J., and Sherlock, P. Tissue concentrations and proliferative effects of massive doses of ascorbic acid in the mouse. Nutr. Cancer 4, 241-246 (1983). 8. Deschner, E. E., Cohen, B. I., and Raicht, R. F. Acute and chronic effect of dietary cholic acid on colonic epithelial cell proliferation. Digestion 21, 290-296 (1981). 9. Deschner, E. E., Cohen, B. I., and Raicht, R. E Kinetics of the protective effect of beta sitosterol against MNU induced colonic neoplasia. .Z. Cancer Res. Clin. Oncol. 103, 49-54 (1982). 10. Deschner, E. E., Long, F. C. Hakissian, M., and Herrmann, S. L. Differential susceptibility of AKR, C57BL/6J and CFl mice to 1,2-dimethylhydrazine induced colonic tumor formation predicted by proliferative characteristics of colonic epithelial cells. J. Natl. Cancer Inst. 70, 279-282 (1983). 11. Deschner, E. E., Long, E C., Hakissian, M., and Cupo, S. H. Differential susceptibility of inbred mouse strains forecast by acute colonic proliferative response to methylazoxymethanol. .Z. Nut/. Cancer Inst. 72, 195-198 (1984). 12. Deschner, E. E., and Wattenberg, L. W. The proliferative effect of butylated hydroxyanisole on MAM treated colonic mucosa. Cancer Lett. 16, 197-202 (1982). 13. Eastwood, G. L., and Trier, J. S. Epithelial cell renewal in cultured rectal biopsies in ulcerative colitis. Gastroenterology 64, 383-390 (1973). 14. Fabian, R. J., Abraham, R., Coulson, F., and Golberg, L. Carrageenan-induced squamous metaplasia of the rectal mucosa in the rat. Gastroenterology 65, 265-276 (1974). 15. Farmer, R. G., Hawk, W. A., and Tumbull, R. B., Jr. Carcinoma associated with mucosal ulcerative colitis and with transmural colitis and enteritis (Crohn’s disease). Cancer 28, 289-292 (1971).
CELL TURNOVER
AND NEOPLASIA
585
16. Fath, R. B., Deschner, E. E., Winawer, S. J., and Dworkin, B. M. Degraded carrageenan-induced colitis in CFl mice: A clinical, histopathological and kinetic analysis. Digestion 29, 197-203 (1984). 17. Fenoglio, C. M., and Pascal, R. R. Adenomatous epithelium, intraepithelial anaplasia and invasive carcinoma in ulcerative colitis. Dig. Dis. 18, 556-562 (1973). 18. Friedman, E., Gillin, S., and Lipkin, M. 12-0-tetradeanoylphorbol-13-acetate stimulation of DNA synthesis in cultured preneoplastic familial polyposis colonic epithelial cells but not in normal colonic epithelial cells. Cancer Res. 44, 4078-4086 (1984). 19. Greenstein, A. J., Sachar, D. B., Smith, H., Janowitz, H. D., and Aufses, A. H. Patterns of neoplasia in Crohn’s disease and ulcerative colitis. Cancer 46, 403-407 (1980). 20. Jacobs, L. R., and Schneeman, B. 0. Effects of dietary wheat bran on rat colonic structure and mucosal cell growth. J. Nufr. 111, 798-803 (1981). 21. Jacobs, L. R., and White, F. A. Modulation of mucosal cell proliferation in the intestine of rats fed a wheat bran diet. Amer. J. C/in. Nutr. 37, 945-953 (1983). 22. Lipkin, M., and Newmark, H. Effect of added dietary calcium on colonic epithelial cell proliferation in subjects at high risk for familial colonic cancer. New Engl. J. Med. 313, 1381- 1384 (1985). 23. Lipkin, M., Uehara, K., Winawer, S., Sanchez, A., Bauer, C., Phillips, R., Lynch, H. T., Blattner, W. A., and Fraumeni, J. F., Jr. Seventh-Day Adventist vegetarians have a quiescent proliferative activity in colonic mucosa. Cancer Lett. 26, 139-144 (1985). 24. Marcus, R., and Watt, J. Colonic ulceration in young rats fed degraded carrageenan. Lancet 2, 765-766 (1971). 25. Maskens, A. P. Mathematical models of carcinogenesis and tumor growth in an experimental rat colon adenocarcinoma, in “Gastrointestinal Cancer” (M. Lipkin and R. A. Good, Eds.), p. 361. Plenum, New York, 1978. 26. Phillips, R. L., Kuzma, J. W., and Lotz, T. M. Cancer mortality among comparable members versus nonmembers of the Seventh-Day Adventist church, in “Cancer Incidence in Defined Populations,” Banbury Report 4 (J. Cairns, J. L. Lyon, and M. Skolnick, Eds.), p. 93. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 1980. 27. Pozharisski, K. M. The significance of nonspecific injury for colon carcinogenesis in rats. Cancer Res. 3.5, 3824-3830 (1975). 28. Raicht, R. F., Cohen, B. I., Fazzini, E. P., Sarwal, A. N., and Takahashi, M. Protective effect of plant sterols against chemically induced colon tumors in rats. Cancer Res. 40, 403-405 (1980). 29. Reddy, B. S., and Hirota, N. Effect of dietary ascorbic acid on 1,2-dimethylhydrazine-induced colon cancer in rats. Fed. Proc. 38, 174 (1979). 30. Serafine, E. P., Kirk, A. P., and Chambers, T. J. Rate and pattern of epithelial cell proliferation in ulcerative colitis. Gut 22, 648-652 (1981). 31. Sunter, J. P., Appleton, D. R., de Rodriguez, M. S. B., Wright, N. A., and Watson, A. J. A comparison of cell proliferation at different sites within the large bowel of the mouse. J. Anat. 129, 833-842 (1979). 32. Sunter, J. P., Watson, A. J., Wright, N. A., and Appleton, D. R. Cell proliferation at different sites along the length of the rat colon. Virchows Arch. B Cell Pathol. 32, 75-87 (1979). 33. Wakabayashi, K., Inagaki, T., Fujimoto, Y., and Fukuda, Y. Induction by degraded carrageenan of colorectal tumors in rats. Cancer Lett. 4, 171-176 (1978). 34. Watanabe, K., Reddy, B. S., Wong, C. O., and Weisburger, J. H. Effect of dietary undegraded carrageenan on colon carcinogenesis in F344 rats treated with azomethane or methylnitrosurea. Cancer Res. 38, 4427-4430 (1978). 35. Wattenberg, L. W., and Sparnins, V. L. Inhibitory effects of butylated hydroxyanisole on methylazoxymethanol acetate-induced neoplasia of the large intestine and on nicotinamide adenine dinucleotide-dependent alcohol dehydrogenase activity in mice. J. Nut/. Cancer Inst. 63, 219-222 (1979).