aberrant crypts: potential preneoplastic lesions in the murine … · aberrant crypts: potential...

[CANCER RESEARCH 48.6187-6192. November 1, 1988]

Aberrant Crypts: Potential Preneoplastic Lesions in the Murine ColonElizabeth A. McLellan and Ranjana P. Bird1

Ludwig Institute for Cancer Research Toronto Branch, Toronto, Ontario, Canada M4Y ÃŒM4and the Department of Nutritional Sciences, University of Toronto, Toronto,Ontario, Canada M5S IAS

ABSTRACT

Murine colons treated with the colon carcinogen azoxymethane(AOM) have been reported to contain aberrant crypts (AC), which arecharacterized by their larger size and wider pericryptal zones. Themethodology used to visualize AC consists of staining the fixed, unsec-tioned colonie mucosa with mÃ©thylÃ¨neblue and transillumination of theluminal surface at a magnification of 40x. The objective of the presentstudies was to determine if AC demonstrate characteristics to supportour hypothesis that they are putative preneoplastic lesions. Studies weredesigned to determine the time of occurrence of AC (Study I), theinduction of AC in response to varying dosages of AOM ranging from0.0 to 10.0 mg/kg body weight (Study II), and the effect of a high fat diet(20% fat by weight) on the number and size of AC (Study III). In allstudies 4-6-week-old female CFi mice were used. In addition C57BL/6Jfemale mice were used in Study I. The major findings were as follows:(a) the time period required to form AC was approximately 2 weeksfollowing a single AOM injection (5 mg/kg); (b) a dose-dependent increase in the induction of AC was noted in response to AOM from nonein the control group to a plateau level of 2.90 Â±0.38 foci at a dose of 5.0mg/kg; (c) in comparison to the low fat group, the high fat group had agreater (P < 0.05) mean number of foci of AC per 5 cm of colon (15.67Â±1.32 vs. 11.44 Â±1.44) and a larger (P < 0.05) mean size of foci of AC(0.0296 Â±0.0012 mm vs. 0.0249 Â±0.0012 mm) after 16 weeks on therespective diets; and (il) preliminary histolÃ³gica!appearance of foci ofAC revealed mild atypia to unequivocal dysplasia. The findings of thepresent study are consistent with the hypothesis that AC are putativepreneoplastic lesions.

INTRODUCTION

Our understanding of the histogenesis of colon cancer hascome from sequential morphological studies done in both humans and animals. Based on such studies it is believed thatcolon cancer, like the majority of cancers, evolves from precursor lesions (1). Work done in humans by Morson and hiscolleagues (2, 3) and by Lane and colleagues (4, 5) providesstrong support for the contention that colon cancer evolvesfrom adenomatous polyps. To identify the possible precursorlesions of adenomatous polyps, and hence the early precursorlesions of colon cancer, several investigators have studied thedevelopment of colon cancer in rodents treated with chemicalcarcinogens.

Generally, the protocol employed in these studies consists oftreating the animals with multiple injections of the carcinogenand then viewing serial, histological sections of the colon inorder to note any changes. Following such a protocol severalresearchers (6, 7) have identified crypts with distinctly alteredproliferative patterns. They have proposed that such cryptsrepresent one of the early precursor lesions in the evolution ofcolon cancer. In addition, Chang (8), following a similar protocol, noted single crypts exhibiting dysplasia which he hasproposed represent preneoplastic lesions.

The above-mentioned studies, by identifying putative preneoplastic lesions, have contributed greatly to our understandingof the stages involved in the development of colon cancer.However, the methodology used to identify these precursorlesions does not allow for quantification of the lesions. In fact.

at the present time there is not a methodology capable ofidentifying and quantitating the early putative preneoplasticlesions in the colon. Without such a methodology it is notpossible to employ these lesions as endpoints in studies.

Recently, in our laboratory we have developed a methodologywhich may be capable of identifying and quantitating the earlypreneoplastic lesions in the rodent colon (9). By applying thismethodology we have observed lesions at the crypt level, presentin the colons of rodents treated with a colon carcinogen. Thecryptai lesions are distinguished by their increased size, thickerepithelial lining, and increased pericryptal zone. We havetermed these lesions AC.2 Since AC have only been observed inthe colons of carcinogen-treated rodents and never in the colonsof control rodents, we have hypothesized that AC may representearly preneoplastic lesions in the rodent colon.

Research in our laboratory is aimed at determining whetheror not AC demonstrate characteristics to suggest they may bepreneoplastic lesions. The purpose of this paper is to report onour findings from three such studies. Study I was designed todetermine the time of occurrence of AC and number of ACinduced in response to one injection of the colon carcinogen,AOM, in two strains of mice differing in their sensitivity todeveloping colon cancer. The objective of Study II was todetermine if there is a dose-dependent response between thenumber of AC formed and the dosage of AOM given. The effectof a HF diet on the growth of AC was investigated in Study III.Preliminary findings on the histological appearance of AC arealso presented.

MATERIALS AND METHODS

Animals. In all studies the animals were housed in plastic cages withwire tops and sawdust bedding with a 12-h light-dark cycle. Unlessotherwise stated, the animals were fed AIN pellets (10) ad libitum andhad free access to water.

Visualization and Quantification of AC. Immediately following termination of the animal, the colon was removed, flushed with Kreb's

Ringer, slit open from cecum to anus, and fixed in 10% bufferedformalin. Following the protocol cited by Bird (9), the fixed colonswere stained with mÃ©thylÃ¨neblue and then using the light microscopethe colons were assessed for AC. The parameters used to assess thecolons were occurrence, size, and distribution of AC. The occurrencewas measured by quantitating the mean number of foci of AC per colon.The number of AC per focus was also recorded. To assess the size ofthe foci, a grid was placed in the eyepiece of the light microscope andwith the magnification at lOOx the number of squares on the gridwhich the focus occupied was recorded. Each square in the grid had anarea of 10~2mm2. To determine the distribution of AC the colon was

divided into three sections. R represented the first 2 cm from the rectalend. M was the next 2 cm from R, and C was the first cm from M.

Pictures of the lesions were taken using Kodak Panatomic-X blackand white film in a Nikon FX-35A camera which was attached to aNikon microscope.

Study I: Time of Occurrence. Both CF, female mice (Charles RiverCanada Inc., Montreal, Quebec, Canada) and C57BL/6J female mice(The Jackson Laboratory, Bar Harbor, ME) approximately 6 weeks oldwere used to determine the time of occurrence. The mice were randomly

Received 2/18/88: revised 7/6/88: accepted 8/3/88.1To whom requests for reprints should he addressed.

2The abbreviations used are: AC, aberrant crypts: AOM. azoxymethane: b.w.,body weight; HF. high fat: LF. low fat.

6187

on June 9, 2020. © 1988 American Association for Cancer Research. cancerres.aacrjournals.org Downloaded from

http://cancerres.aacrjournals.org/

POTENTIAL PRENEOPLASTIC LESIONS

divided into two groups of 20 mice each. Group 1 received a single i.p.injection of 5 mg AOM (Ash Stevens) per kg b.w. Group 2 acted as thecontrol group and received a single i.p. injection of saline. Five micefrom each group were terminated by cervical dislocation, 1, 2, 3, and 4weeks after receiving the injection.

Study II: Dose Response. 4-week-old CF, female mice were randomlydivided into six groups. Each group received one i.p. injection of AOMat one of the following dosage levels: 0.0. 1.0, 2.5, 5.0, 7.5, or 10.0 mgper kg b.w. 2 weeks after the carcinogen treatment the mice wereterminated by cervical dislocation.

Study III: Dietary Modulation. 4-week-old CF, mice were randomlydivided into two groups. Group 1 received 4 weekly i.p. injections of 5mg AOM per kg b.w. Group 2 received 4 weekly i.p. injections ofsaline. 1 week following the fourth injection half the mice were fed aHF diet (I5ri beef tallow and 5Ã•7corn oil by weight) while the

remaining continued on a LF diet (5% corn oil by weight). The compositions of the diets are listed in Table 1. To make the HF diet extrafat was added to the LF diet at the expense of carbohydrate. Thenutrient per kilocalorie density of the HF diet was identical to the LFdiet except with respect to fat and carbohydrate. The mice were terminated after either 0, 4. 8, or 16 weeks on the diets.

Statistical Analysis. Statistical analysis of the data was performed byanalysis of variance and Duncan's multiple range test. A probability of

less than 5% (P < 0.05) was considered significant.

RESULTS

No AC were identified in the colons of mice given salinealone. Therefore, only the data for the mice treated with carcinogen are presented in the tables below.

Study I: Time of Occurrence. The results of Study I are shownin Table 2. In both CFi and C57 mice, the AC were notdetectable until 2 weeks following the AOM injection. At the2-week termination point CFi mice had a significantly higher

Table 1 Percentage by weight composition of the diets

CaseinDextrinSucroseCorn

oilBeeftallowAIN-76

mineralmixA1N-76vitaminmix(Â«-CelluloseDi.-mcthionineCholine

bitartrate%of calories from linoleicacidâ€¢

AIN-76diet.*Modified AIN-76 diet.Low

fatdiet"20.015.050.05.00.03.51.05.0OJ0.27.1Highfatdiet*22.710.535.05.015.04.11.25.90.40.27.0

mean number of foci per colon compared to C57 mice at thesame time point. The mean number of foci per colon in CFimice tended to decrease with time and the opposite trend wasnoted in C57 mice. Due to the small number of mice per group,neither trend was statistically significant. It is interesting tonote that the CF, mice showed 100% incidence of AC throughout the study. However, with the C57 mice, it was not until the4th week that the 100% incidence level was reached. Therewere no significant changes in the size of foci or the number ofAC per focus in either strain as a function of time.

Study II: Dose Response. There was no significant differencebetween the mean weights of the six groups (data not shown).The AC data for Study II is presented in Table 3. It is evidentthat there is a trend of increasing number of foci of AC percolon in response to increasing dosages of AOM up to 7.5 mgof AOM after which there appears to be a leveling off. A similartrend is also seen with the size of the foci as well as the numberof AC per focus in response to the dosage of AOM given.Although the majority of AC are located towards the rectal end,it is apparent that the higher dosages of AOM (7.5 and 10.0mg/kg b.w.) tended to induce a relatively higher number of ACtowards the cecum end than the lower dosages.

Study III: Dietary Modulation. The body weights of theanimals on the HF diet tended to be higher than those on theLF diet. However, there was no significant difference betweenthe mean weights of the mice on the HF and LF diets at anytime point in the study (Table 4). The AC data for Study III islisted in Table 5. The HF group had more foci of AC per coloncompared to the LF group at each of the respective time points.However, the difference was statistically significant only at the16-week point. The mean size of the foci was significantly largerin the HF group compared to the LF group at the 16-weekpoint. Between the 8th and the 16th week there was a significantincrease in the mean number of foci per colon and in the meannumber of AC per focus within both treatment groups. Also,the mean size of the foci increased in both treatment groupsbetween the 8th and the 16th week although it was only statistically significant in the HF group.

Appearance and Distribution of AC. Foci of AC are easilyrecognizable by their increased size, pericryptal area, andthicker epithelial lining. Fig. I, A, B, D, and E, depict foci ofAC present in unsectioned, mÃ©thylÃ¨neblue-stained, carcinogen-treated murine colons. Foci of AC containing varying numbersof AC have been observed. Fig. 1C shows the histologicalappearance of the focus identified in Fig. IB. Examination of

Table 2 Effect of lime on appearance of AC in murine (CFÂ¡and C57BL/6J) colon induced hy a:o.\yme1haneCF, and C57BL/6J mice were studied to determine the number of weeks required for AC formation following a single i.p. injection of 5 mg/kg body weight of the

colon carcinogen azoxymethane. The colons were scored for AC 1, 2, 3, and 4 weeks after treatment with the carcinogen.

No. weeks"Incidence*CF,

mice10/525/535/54

5/5C57BL/6J

mice10/522/433/44

5/5No.

foci/colonr0.00

Â±0.0*4.00Â±\.ÃŒO'J2.60Â±0.68'"i'r3.00Â±0.20'J0.00

Â±0.0*0.50Â±0.29**1.00Â±0.41/*'*2.60

Â±0.93'Â¿*No.

AC/focusc1.00

Â±0.0'1.23+0.21'1.36

Â±0.13'1

.00 Â±0.0'1.00Â±0.00'1.31

Â±0.13'Size

of focic(x IO'2

mm2)1.65

Â±0.11'1.88Â±0.21'1.98Â±0.18'1.25

Â±0.25'1.75Â±0.14'1.50

+ 0.13'%

Distribution''R9069711007577M10312902523C000000

Â°No. of weeks between injection and termination.* No. of colons with AC over total no. of colons scored.' All values shown are the mean Â±SE.d % Distribution of foci in the divisions of the colon. See text for explanation of abbreviations.'~* Means with the same letter are not significantly different (P < 0.05).

6188




Table 3 Effect of various doses ofAOM on number and size of AC in CF, miceCF, mice were given a single i.p. injection of AOM at various dosages. 2 weeks following the injection, the colons were scored for AC.

Dosage"1.0

2.55.07.5

10.0Incidence*0/10

1/910/1018/1917/18No.

foci/colonc0.00

Â±</0.11 Â±0.11/2.90 Â±0.38'4.05 Â±0.42'3. 17 Â±0.50'No.

AG/focus01.0

Â±0.0'1.03 Â±0.03'1.31 Â±0.06'1.28 Â±0.07'Size

of focif(x 10~2

mm2)1.0

+ 0.0'1.66 Â±0.09'1.98 Â±0.09'1.89 Â±0.13'%

distribution"*R100

8367

56M0

172932C00 412

" Dosages of AOM administered in mg per kg body weight.* No. of colons with AC over total no. of colons scored.c All values shown are the mean Â±SE.* % distribution of foci in the divisions of the colon. See text for explanation of R, M, and C abbreviations.' Means with the same letter are not significantly different (P < 0.05).

Table 4 Mean body weights ofCF\ mice treated with azoxymethane and fedeither a LF or HF diet for 4, 8, or 16 weeks

Diet

Body wtÂ°,g, of mice on experimental diets at

4 weeks 8 weeks 16 weeks

LFHF25.36

Â±0.7325.86 Â±0.5531.34

Â±1.3430.11 Â±1.0534.00+

1.7836.52 Â±1.06

Â°Mean wt Â±SE.

the histolÃ³gica! appearance shows that the epithelial cells liningthe AC appear to be disorganized. Fig. IF depicts the histolog-ical appearance of the large and small foci of AC shown in Fig.IE. It was apparent from the histolÃ³gica! sections that the largefocus of AC consisted of tortuous crypt structures manifestingdysplasia and hence could be termed a microadenoma.

Serial sections of the focus shown in Fig. 1C reveal that thelarger crypt in the focus branches into two distinct cryptstowards the muscularis mucosa (Fig. 2). Also, the pericryptalarea of the AC shows accumulation of oval-shaped cells. Thecharacteristics and significance of these cells are not known. Itis noted that the AC contain mitotic figures whereas the surrounding normal crypts do not, thus suggesting that the zoneof cell proliferation is increased in AC compared to normalcrypts (Fig. 2E). Goblet cells are not as evident in AC comparedto the surrounding normal crypts (Fig. 2, C-F).

The data from all four studies show that the majority of theAC are located in the distal colon. In addition, all studies showthat an aberrant crypt is at least three to four times larger thana normal crypt. At a magnification of lOOx, a normal cryptoccupied 0.25-0.33 the area of one square on the measuringgrid.

DISCUSSION

The results of Study I show that in CFi and C57BL/6J mice,AC require between 8 and 14 days to form following carcinogen

treatment. This length of time seems reasonable given thathistologically we have shown that AC have altered morphology.The finding that AC can be detected 2 weeks following carcinogen treatment is to our knowledge the earliest time a focalaberration at the crypt level has been demonstrated. It is alsothe first time such a lesion has been identified following asingle, low dose treatment with a carcinogen. For example,following multiple carcinogen treatments, Deschner (11) hasobserved focal atypias confined to one or two crypts at 38 days.

The strain differences observed at the 2-week terminationpoint in Study I would appear to indicate that C57 mice maybe less sensitive to developing AC than CFi mice. However, bythe 4-week termination point there was no significant differencebetween the two groups with respect to mean number of foci ofAC per colon. Thurnherr et al. (12) have reported that CFimice are more sensitive to developing colon tumors in responseto exposure to the colon carcinogen, 1,2-dimethylhydrazine,than are C57 mice. Assuming CFi mice are indeed more sensitive and that AC are reflective of the colon carcinogenesisprocess, then the data reported in Study I would suggest that itis the rate at which AC are formed that is indicative of sensitivityto the development of colon cancer. Further studies are neededto assess this possibility.

The findings of Study II indicate that AC are induced in adose-dependent manner following carcinogen treatment. Thefailure to show a pronounced dose response is likely due to thesmall differences between the dosages of carcinogen tested.Following a similar protocol, we have completed a dose-response study in Sprague-Dawley rats using dosages of the coloncarcinogen 1,2-dimethylhydrazine ranging from 0.00 to 150mg/kg b.w. The data generated from this study yielded a similar,yet more pronounced, dose-response curve with the maximumnumber of AC being formed in response to a dose of 125 mg/

Table 5 Effect ofLF or HF diet on number and size of AC induced by AOMCFi mice were given 4 weekly i.p. injections of AOM. One week after the final injection half the number of remaining mice were fed a HF diet (20% by weight)

and the other half continued on the LF diet (5% by weight). The colons were scored for AC after 0, 4, 8, and 16 weeks on the diet.

Treatment0(diet-weeks)P'LF-4LF-8LF-16HF-4HF-8HF-16Incidence*10/1010/1010/109/910/1011/119/9No.foci/colonr7.10+

2.25f6.10Â±1.2976.00+0.99f11.44+

1.44'9.70+0.87/:*9.36Â±\.49f-'15.67+

1.32'No.

AC/focusc1.34

+0.09/\.52Â±0.09f'111.70

+0.09*1.98+0.10'1.67+0.07*1.60Â±0.07/*2.17

Â±0.08'Size

of focic(X 10~2mm2)2.36

+0.14/i1.52+0.08*2.12Â±0.13/l2.49

+0.12*2.10+0.09/2.15+0.10/*2.96Â±0.12'%

distribution'R435861364149Mt393534445740C1875221

" Treatment: P. mice terminated I week following 4th AOM injection: diet-week, mice given 4 AOM injections then fed a LF or H F diet-no, of weeks of feeding

before termination.* No. of colons with AC over total no. of colons scored.c All values shown are the mean Â±SE.d % Distribution of foci in the divisions of the colon. See text for explanation of abbreviations.' No data available.f~' Means with the same letter are not significantly different (/" < 0.05).

6189




â€¢-

.

'Â¿ÃŒ&&FFig. I. Topographic views of AC in unsectioned mÃ©thylÃ¨neblue-stained murine colon and their histology. In A, topographic view of mucosa of colon from animal

treated with a single i.p. injection of AOM and then left for 2 weeks. A single AC is surrounded by normal crypts. Note the increase in size and density of theepithelial lining of the AC, x 40. In B. topographic view of mucosa of colon from animal treated with 4 weekly i.p. injections of AOM. A foci of 2 AC is surroundedby normal crypts, x 40. In C, histolÃ³gica! appearance of the focus shown in Fig. IÃŸ.Note the architecture of the AC exhibit a focal appearance and mild cellularatypia. H & E, x 100. In D, topographic view of mucosa of colon from animal treated with 4 weekly injections of AOM. A focus of 3 AC is surrounded by normalcrypts, x 50. In E, topographic view of mucosa of colon from animal treated with 4 weekly i.p. injections of AOM and then fed a high-fat diet for 16 weeks. Two fociof AC side by side. The smaller focus (arrow) consists of 2 AC. The number of AC in the larger focus could not be determined, x 10. In F, histolÃ³gica!appearance ofthe two foci in Fig. IE. Note that the two AC constituting the smaller focus are larger than the normal crypts (arrow). Dysplasia is present in the larger focus, H &E, x 20.

kg b.w. and significantly less at the highest dose of 150 mg/kgb.w.3

The findings that AC are induced in a dose-dependent manner suggests that there is a cause-and-effect relationship between formation of AC and exposure to the carcinogen and,hence, supports the hypothesis that AC represent preneoplasticlesions. It is interesting to note that the size of AC foci, as wellas the number of AC per focus, showed a similar response toincreasing doses of carcinogen as did the number of AC percolon. Although the trend noted within each of these twoparameters was not statistically significant at 2 weeks aftercarcinogen treatment, it is possible that with time a statisticallysignificant difference between response and dose of carcinogenwould be observed for both these parameters. Study I showedthat AC require between 8 and 14 days to form. Therefore, byjust 2 weeks after carcinogen treatment the parameter mostlikely to demonstrate a dose response is the number of ACinduced. However, once induced it is likely that with time thegrowth of the AC, as assessed by the size of the foci and thenumber of AC per focus, will be dependent on the dose ofcarcinogen administered. Further studies are needed to assessthis possibility.

The results of Study III indicate that the growth of AC, as

3 Unpublished observation.

assessed by their number and size, is enhanced by a HF dietconsisting of 20% fat by weight, 75% of which is beef tallowand 25% of which is corn oil. Several long term tumor incidencestudies have shown that a diet in which 20% or more of thediet by weight is from corn oil, safflower oil, beef fat, lard, orany combination thereof, has a promoting effect on coloncarcinogenesis (13-16). Since a HF diet has been shown topromote chemically induced colon carcinogenesis in the rodentmodel, it was reasoned that a HF diet should also promote thegrowth of AC, if AC are indeed preneoplastic lesions. Therefore,the finding of Study III showing that the growth of AC can beenhanced by a HF diet is further support for our contentionthat AC represent preneoplastic lesions. It is known that ACare not formed in response to a HF diet.3 Therefore, the increase

in the mean number of foci of AC per colon with time that wasobserved in Study III must be due to the appearance of slowergrowing AC.

In the murine system the majority of tumors arise in thedistal colon (17). Therefore, the observation that the majorityof AC also occur in the distal colon is consistent with thepossibility that AC are involved in colon carcinogenesis.

The results of all studies show that the area occupied by theluminal opening of AC is three to four times that occupied bynormal crypts. It was noted that one AC (Fig. 2) may have had

6190




CKÃ•H;:ly > "\%^ **.^%%MV^W-O^T u V$Ã‰ -A >4^M^'^"'

^VM *-Ar*>v ,>^K;>?Â£' .â€¢" w

A

SPOTfoÂ£ÃŒJAr

Â«RV^â€¢T Ã§

Fig. 2. Serial histolÃ³gica! sections of the focus of two AC shown in Fig. IB. Sections progress from luminal surface towards muscularis mucosa. A, H & E, x 50;B, note the accumulation of cells in the pericryptal zone of the AC, H & E, x 100; C, note the lack of goblet cells in the AC compared to the surrounding normalcrypts, H & E. x 100: O, note the apparent division of the larger AC into two crypts, H & E, x 100; E, note the presence of three distinct crypts comprising the focusand the presence of mitotic figures (arrows) in the AC but not in the surrounding normal crypts, H & E, x 100; F, note the increased accumulation of cells surroundingthe focus as seen in Fig. \.AloE, are no longer apparent closer to the muscularis mucosa, H & E, x 100.

a large luminal opening because it was multiplying. The histolÃ³gica!appearance of two foci, both consisting of two AC (Fig.1, C and F), is clearly atypical. Although the atypia seen in thesmaller focus cannot be called unequivocally dysplasia, thelarger focus in Fig. IF clearly exhibits dysplasia and can betermed a microadenoma, which is considered to be a precursorlesion of colon cancer (18). When the unsectioned tissue wasstained with mÃ©thylÃ¨neblue, the microadenoma looked asthough it was composed of many AC. It is our contention thatthe microadenoma evolved from a single AC which at one timeexhibited only mild atypia (such as the one in Fig. 2). If ourcontention is correct, we would have a simple method for theidentification of very early preneoplastic lesions (i.e., "predys-plastic" crypts) right through to microadenomas. Such a meth

odology would greatly facilitate the study of the multistepprocess of carcinogenesis in the colon. To substantiate ourhypothesis a systematic characterization of AC with time isbeing carried out in our laboratory.

The main objective of the studies reported in this article wasto determine if the lesions we have identified, by the methodology developed in our laboratory, demonstrate characteristicsto suggest that they may represent preneoplastic lesions in therodent colon. Based on the results, the following is knownabout AC in the murine colon: they can be induced in 2 weeksby a low dosage of a colon carcinogen, they are induced in adose-dependent manner, their growth is affected by dietarymodifications, they are largely located in the distal colon, andthey exhibit morphological alterations. All these observationsare consistent with our hypothesis that AC represent preneoplastic lesions.

Further studies in the rodent model are in progress to sequentially characterize AC for morphological, proliferative, andhistochemical changes.

The existence of a methodology capable of identifying andquantitating preneoplastic lesions in the rodent colon will serve

as an important tool in extending our knowledge of the cellularevents taking place during colon carcinogenesis. The existenceof such a system for the study of experimentally induced skinand liver cancer has already contributed greatly to our understanding of the cancer process (1). Furthermore, induction ofAC can be used as a screening system to identify colon carcinogens in our diet; and the growth of AC can be used to identifyand assess dietary factors capable of modulating the development of colon cancer.

ACKNOWLEDGMENTS

The authors wish to thank Dr. Alan Mediine (Department of Pathology, University of Toronto, and Northwestern General Hospital,Toronto, Ontario) for the histolÃ³gica! assessment of aberrant crypts.The authors thank Margaret Magee for her support and care in thepreparation of this manuscript.

REFERENCES

1. Farber, E., and Cameron, R. The sequential analysis of cancer development.Adv. Cancer Res., 31: 125-226, 1980.

2. Day, D. W., and Morson, B. C. The adenoma-carcinoma sequence, in: B. C.Morson (ed.). The Pathogenesis of Colorectal Cancer, pp. 58-71. Philadelphia: W. B. Saunders Company. 1978.

3. Muto, T.. Bussey, H. J. R., and Morson. B. C. The evolution of cancer ofthe colon and rectum. Cancer (Phila.). 36: 2251-2270, 1975.

4. Lane, N. The precursor tissue of ordinar) large bowel cancer. Cancer Res.,36:2669-2672, 1976.

5. Fenoglio, C. M., and Lane, N. The anatomical precursor of colorectalcarcinoma. Cancer (Phila.), 34: 819-823. 1974.

6. Lipkin, M., and Deschner, E. Early proliferative changes in intestinal cells.Cancer Res., 36: 2665-2668, 1976.

7. Richards. T. C. Early changes in the dynamics of crypt cell populations inmouse colon following administration of 1,2-dimethylhydrazine. CancerRes.. 37: 1680-1685, 1977.

8. Chang, W. W. L. Histogenesis of colon cancer in experimental animals.Scand. J. Gastroenterol. /9(Suppl. 104): 27-44. 1984.

9. Bird. R. P. Observation and quantification of aberrant crypts in the murinecolon treated with a colon carcinogen: preliminar) findings. Cancer Lett.,37: 147-151. 1987.

6191




10. Report of the American Institute of Nutrition Ad Hoc Committee on Stand- 15. Reddy, B. S., Narisawa, T., Vukusich, D.. Weisburger. J. H., and Wynder,ards of Nutritional Studies. J. Nutr../07: 1340-1348. 1977. E L Effect of quality and quantity of dietary fat and dimethylhydrazine in

' ' ' Â£frÂ«Â£jtt E. Experimentally induced cancer of the colon. Cancer (Phila.), co,on carcinogenesis in rats. Proc. Soc. Exp. Biol. Med., 151:237-239, 1976.

12. ThurnheVr N.. Deschner, E. E.. Stonehill. E. N.. and Lipkin, M. Induction ><*â€¢Bull. A. W.. Soullier. B. K, Wilson. P. S.. Hayden. M. T.. and Migro, N. D.of adenocarcinomas of the colon in mice by weekly injections of 1,2-di- Promotion of azoxymethane-mduced intestinal cancer by high-fat diet inmcthylhydrazine. Cancer Res.. 33: 940-945. 1973. rats. Cancer Res., 39:4956-4959, 1979.

13. Nigro, N. D., Singh, D. V.. Campbell, R. L.. and Pak, M. S. Effect of dietary 17. Wiebecke. B., Krey, U., Lohrs, U., and Eder, M. Morphological and auto-beef fat on intestinal tumor formation by azoxymethane in rats. J. Nati. radiographical investigations on experimental carcinogenesis and polyp de-Cancer Inst.. 54: 439-44 2. 1975. , ,, â€¢mm ru- u r < velopment in the intestinal tract of rats and mice. Virchows Arch. Abt. A.

14. Reddy. B. S.. Watanabe. K.. and Weisburger. J. H. Effect of high-fat diet on ;colon carcinogenesis in F344 rats treated with 1,2-dimethylhydrazine, meth- Patnol. Anat.. iUÃ¶:l /y-iyj, iy IS.ylazoxymethanol acetate, or methylnitrosourea. Cancer Res.. 37:4156-4159, 18- Morson, B. C, and Komshi, F. Dysplasia in the colorectum. Scand. J.1977. Gastroenterol., 79(Suppl. 104): 137-149. 1984.

6192



1988;48:6187-6192. Cancer Res Elizabeth A. McLellan and Ranjana P. Bird ColonAberrant Crypts: Potential Preneoplastic Lesions in the Murine

Updated version

http://cancerres.aacrjournals.org/content/48/21/6187

Access the most recent version of this article at:

E-mail alerts related to this article or journal.Sign up to receive free email-alerts

Subscriptions

Reprints and

[email protected] at

To order reprints of this article or to subscribe to the journal, contact the AACR Publications

Permissions

Rightslink site. Click on "Request Permissions" which will take you to the Copyright Clearance Center's (CCC)

.http://cancerres.aacrjournals.org/content/48/21/6187To request permission to re-use all or part of this article, use this link



http://cancerres.aacrjournals.org/cgi/alerts

mailto:[email protected]



aberrant crypts: potential preneoplastic lesions in the murine … · aberrant crypts: potential...

Documents