Transplantation of chemically induced metastatic mucinous adenocarcinomas of the jejunum and colon in rats

Nonproliferative and Proliferative Lesions of the Gastrointestinal Tract, Pancreas and Salivary Glands of the Rat and Mouse

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) project is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature and diagnostic criteria for nonproliferative and proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and diagnostic criteria for classifying lesions in the digestive system including the salivary glands and the exocrine pancreas of laboratory rats and mice. Most lesions are illustrated by color photomicrographs. The standardized nomenclature, the diagnostic criteria, and the photomicrographs are also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and age related lesions as well as lesions induced by exposure to test items. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature and diagnostic criteria for the digestive system will decrease misunderstandings among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Intestinal tumor progression is associated with altered function of KLF5

Krüppel-like transcription factors have been linked to cell growth regulation and tumorigenesis in a number of systems. In the intestinal epithelium, expression of KLF5 (IKLF/BTEB2) is limited to proliferating crypt cells, indicating a growth-promoting role. Consistent with this role, we demonstrate that expression of KLF5 in non-transformed intestinal epithelial cells (ileal IEC-18 and Immorto-Min Colon Epithelial (IMCE) cells) enhances colony formation, cyclin D1 transcription, and cell growth. However, in contrast to these effects in non-transformed cells, KLF5 reduced colony number, failed to enhance cyclin D1 transcription, and was negatively correlated with cell growth in colon cancer cell lines. The relationship between tumor progression and KLF5 was further investigated using Ras-mediated transformation of IEC-18 and IMCE cells as syngeneic models. Ras-transformation recapitulated differences in the effects of KLF5 on cell growth and cyclin D1 transcription, providing a direct link between intestinal tumor progression and altered function of KLF5. Ras-transformation also markedly down-regulated KLF5; further analysis indicated that reduced expression of KLF5 mRNA and destabilization of KLF5 protein occur in intestinal tumors. Reduced levels of KLF5 mRNA were also detected in APC(min) mouse and human familial adenomatous polyposis adenomas compared with normal crypt epithelium, indicating that down-regulation of KLF5 is an early event in intestinal tumorigenesis in vivo. Collectively, these data indicate that intestinal tumor progression is associated with a change in the growth-related functions of KLF5 and that intestinal tumors down-regulate KLF5 expression by multiple mechanisms.

Identification of a novel cell population in nonhealing wounds in tumors

We have explored wound healing in tumors as a possible model for tumor-host interaction. This work demonstrated tumor wound healing failure to be the result of intense inhibition of fibroblasts although the tumor cells did not appear to be the direct source of the inhibitors. The inflammatory infiltrate found in tumor wounds was then examined for possible sources of the observed fibroblast suppression. Although the tumor wound infiltrate contains cell populations similar to a normal wound infiltrate, it also contains a large, vacuolated, nonadherent, phagocytic mononuclear cell which has morphologic and cytochemical characteristics of a lipid-laden macrophage. However, the cell also proliferates under normal culture conditions and has an immunophenotype more characteristic of lymphocytes than those of macrophages with striking expression of the CD8 surface antigen. Conditioned media from this cell population markedly inhibit fibroblast proliferation suggesting it is the source of fibroblast inhibitors within the tumor wound. Mechanical dissociation of non-wounded tumors yielded evidence that the tumor wound cell is normally present in small numbers within the tumor.

Effects of 5-fluorouracil, leucovorin, and glucarate in rat colon-tumor explants

In a previous study, we showed that 5-fluorouracil (FU) is active against the dimethylhydrazine-induced colon tumor in rats; a 7-day infusion of FU at 30 mg/kg daily produced 85% tumor-free cures. The present study examined the effects of FU alone and in combination with leucovorin (LV) or D-glucarate (GT) using an ex vivo system that maintained the growth of the rat colon-tumor explants on collagen gels. The labeling index (LI) was determined by the incorporation of [3H]-thymidine and autoradiography. The mean LI of the untreated control was 64.8% +/- 19.8%. The IC50, IC90, and IC95 values following a 7-day exposure to FU were 0.36, 0.75, and 1.22 microM, respectively. In comparison, the steady-state FU concentration required to produce 67% tumor-free cures in rats following a 7-day infusion is 1.54 microM. LV alone did not produce any antiproliferative effect at concentrations as high as 10 microM. The addition of LV at concentrations of 0.001-10 microM did not significantly reduce the IC50 of FU. The lack of effect of LV may have been due to tissue saturation with folate provided in the culture medium. GT alone reduced the tumor LI by 20%-30% at concentrations of 0.1-10 microM. GT enhanced the effect of FU. As compared with FU alone, the addition of GT at concentrations of 0.1 and 1.0 microM reduced the IC50 of FU by 47% and 60% to 0.21 and 0.16 microM, respectively. Assessment of the potentiation of the inhibitory effect of FU by GT using two-way analysis of variance and the isobologram method indicated a significant synergistic interaction between FU and GT. This interaction occurred within the FU concentration range of 0.08 and 0.4 microM. In summary, these data indicate that (a) the IC values for FU are comparable in tumor explants and in rats, suggesting that the effects in cultured tumors reflect those in intact animals; (b) GT alone showed antitumor activity, albeit relatively minor as compared with FU; (c) FU and GT exhibited synergistic activity, which was most pronounced at FU concentrations that produced submaximal activity (less than 30% inhibition of tumor LI); and (d) GT and LV had different effects on the growth inhibition by FU, suggesting that GT acts by a mechanism different from the thymidylate synthase-directed effect of FU and LV.

Prostaglandin E1 enhances tumoricidal activity of 5-fluoro-2'-deoxyuridine in rats

Addition of prostaglandin E1 (PGE1) to 5-fluoro-2'-deoxyuridine (FUDR) infused via the portal vein has been shown to diminish both the regional and the systemic toxicity of this chemotherapeutic agent. The effect of concomitant PGE1 infusion on tumor growth has not yet been determined. This study was designed to assess the effect of PGE1 in combination with FUDR on an established adenocarcinoma in the rat model. Fifty-gram Fischer rats underwent placement of a 3-mm3 fragment of colon carcinoma 4047 in the left thigh pad. After 6 weeks to allow for tumor growth, the animals were randomly assigned to receive a 7-day intravenous infusion of (1) saline, (2) PGE1 (0.1 microgram/kg/min), (3) FUDR (3 mg/kg/day), or (4) PGE1 + FUDR. At 10 days animals receiving PGE1 + FUDR had a significant decrease in tumor volume (mm3, log 10) (3.39 +/- 0.24 vs 3.85 +/- 0.12, P less than 0.05) compared with animals receiving FUDR alone. We conclude that PGE1 may be useful as an adjunctive cytotoxic agent.

Growth characteristics and metastatic potential of seven intestinal carcinoma lines serially passaged in syngeneic rats

Transplantable tumour lines were obtained from one duodenal carcinoma induced by N-methyl-N'-nitro-N-nitrosoguanidine in the Lewis rat and from six colonic carcinomas induced by 1,2 dimethylhydrazine in BDIX or Fisher rats. The tumours were serially transplanted by the subcutaneous route into homologous syngeneic rats. The seven tumours differ from one another in their histological structure, five of them being well or moderately differentiated adenocarcinomas, and in their capacity to produce neutral or acidic mucins. The seven tumours also differ in their growth rate. The seven lines produced metastases; the metastatic potential and the location of the metastases differed from one line to another. The seven lines kept their original differentiation characteristics through multiple passages, representing several years of transplantation into syngeneic hosts. These tumours represent a useful and diversified model of metastatic intestinal carcinoma, available for basic research and therapeutic trials.

Expression of two cytochromes P450 involved in carcinogen activation in a human colon cell line

Cytochrome P450 is known to cause carcinogen activation and correspondingly increased cancer risk in animal models. In order to determine whether P450 in the colon may be involved in cancer development in the human, the human colon cell line LS174T was examined for the presence of various cytochromes P450. Two isozymes of P450 were identified in the human cell line. Expression of P450IA1 or IA2 was increased by treatment of the cell line with benzanthracene; the induction was demonstrated by an increase in RNA hybridizing to a probe for P450IA1 and by ethoxyresorufin deethylation activity. Western analysis of microsomes isolated from human colon tissue also demonstrated the presence of P450IA1, as well as a form which cross-reacted to an antibody to human P450IIC9. Another isozyme, P450IIE1, was identified by polymerase chain reaction amplification of RNA from LS174T cells. These results underscore the presence of cytochromes P450 in colonic tissue and provide a basis for the involvement of isozyme-specific P450 mediated reactions in carcinogenesis of the colon.

Carcinoembryonic antigen: a rat model

It has been shown that a TAA termed rat CEA had the tissue distribution and physico-chemical properties similar to those of human CEA. In addition, it has been demonstrated that these two antigens shared antigenic determinants. These findings supported our contention that rat CEA and human CEA are analogous moieties. The production of CEA-specific autoantibodies and the induction of resistance to CEA-positive rat tumors after immunization of rats with extracts containing rat CEA raises the possibility that human CEA may be immunogenic in man. Treatment with heat, proteolytic enzymes and periodate oxidation revealed that rat CEA, similar to human CEA contained both carbohydrate and protein epitopes. The epitopes shared by rat and human CEA that were detectable by the monkey anti-human CEA serum appeared to be carbohydrate, whereas the epitopes on rat CEA with which the rat mAb combined appeared to be protein, and those detected by the rabbit anti-rat CEA serum appeared to be carbohydrate, as well as protein. These studies also indicated that, although the rat, rabbit and monkey produced antibodies specific for rat CEA, the epitopes detectable by antibodies from one species appeared to be distinct from those detectable by antibodies from the other two species. These observations have important implications in studies on human CEA. Its use as a reliable diagnostic marker for malignancy hinges on the detection of tumor-specific epitopes on the molecule. Such epitopes have not yet been clearly identified by antibodies produced in foreign species. Indeed, our finding that the rat mAb to rat CEA bound only to tumor extracts and not to extracts of normal tissues, including intestinal tissues, suggests that human beings would be the most likely source of a tumor-specific antibody to human CEA. In future studies, the role antibodies play in immunity against CEA-positive tumors will be explored and attempts will be made to determine whether all of the serologically detectable epitopes on rat CEA can induce tumor resistance, or whether this activity is limited to epitopes detectable only by rat antibodies. This information could have important implications in the use of human CEA in the immunotherapy of malignancies.

Does omentectomy prevent malignant small bowel obstruction?

Because the omentum collects and disseminates cancer cells, omentectomy is an integral part of ovarian cancer surgery. We postulate that the omentum serves a similar function in colon cancer and may contribute to post-operative malignant small bowel obstruction (S.B.O.) and that routine omentectomy during colectomy would reduce the incidence of S.B.O. Fischer 344 rats and a transplantable carcinogen-induced rat colon cancer were used to test: (1) whether the omentum is a unique site of intra-abdominal colon tumor implantation which contributes to S.B.O.; and (2) whether omentectomy at the time of tumor implantation would reduce the incidence of S.B.O. Statistical analysis confirmed that animals undergoing omentectomy had a significantly lower incidence of omental tumors and malignant S.B.O. (26 per cent and 16 per cent respectively) when compared with sham operated animals (75 per cent and 85 per cent respectively, P less than 0.001). These data suggest that the omentum is a source of bowel obstruction from implantation and growth of tumour cells in the rat model. Although this could be tested in other animal systems, the addition of routine omentectomy to colectomy is simple, not time-consuming, and may reduce postoperative morbidity.

Monoclonal rat antibodies to rat carcinoembryonic antigen

An IgM-class rat monoclonal antibody, designated 5B1, was produced against rat carcinoembryonic antigen. This antibody, which can be considered an autoantibody, formed a single precipitation line in a gel diffusion test with an extract of the CEA-positive rat colonic adenocarcinoma, RCA-1. This line gave a reaction of complete identity with a line formed by a rabbit antiserum specific for rat CEA. 5B1 also bound to extracts of the RCA-1 tumor in EIA, but did not bind at all to extracts of the CEA-negative rat colonic adenocarcinoma, RCA-2, nor to extracts of normal rat tissues including liver, kidney and intestine. Inhibition tests showed that the activity of the monoclonal antibody in EIA was abolished by extracts of RCA-1 tumor, but was hardly affected by extracts of the other tissues.

Reduced incidence of hepatic metastases by perioperative treatment with recombinant human interleukin-2

Abdominal operations induce immunosuppression during the time when tumors are manipulated and tumor cells are released into the circulation. The authors tested the hypothesis that the combined effect of these factors may promote the development of metastatic tumor implants and that perioperative treatment with Human Recombinant Interleukin-2 (RIL-2), a known immunostimulant of t, natural killer (NK), and lymphokine activated killer (LAK) cells may reduce the incidence of liver metastases from transplantable rat colon cancers. Hepatic metastases were induced in male Fischer 344 (F344) rats by injecting 10(7) rat colon tumor cells into the portal venous system during laparotomy. Control rats developed tumors by four weeks and were dead by ten weeks. Eleven groups of rats underwent celiotomy with portal vein injection of tumor on day three. Rats received either no RIL-2, RIL-2, or excipient buffer at varying doses on days 1 through 5 or 3 through 7 of these experiments. Animals were assessed for the presence of tumor and the incidence of liver metastases at autopsy (sacrifice and autopsy performed at seven weeks). Eighty-five percent of the rats in the untreated group developed tumor. This compared with only 50 percent of animals receiving 10(3) u/dose (P less than .025) and 42 percent of animals receiving 10(4) u/dose (P less than .01) of Interleukin-2 on days 1 through 5. Animals receiving very high doses of RIL-2 (10(5) or 4 X 10(5) units per dose) had a greater chance of developing tumors than did control rats, or rats receiving lower doses of RIL-2 (P less than .05). It is concluded that the perioperative period may be critical for the implantation and growth of metastatic disease and that perioperative immunostimulation with RIL-2 can decrease the incidence of tumors in these animals. This model may have relevance to the treatment of human colon cancer.

Transplantable colonic adenocarcinomas in rats

The induction of colonic adenocarcinoma using two different regimens of dimethylhydrazine (DMH) in Fischer F344 rats is described. Rats receiving 20 mg/kg of DMH per week for 20 weeks developed primary tumors with metastases, whereas rats receiving the same weekly dose for 15 weeks developed primary tumors only. The most common route of metastases was transcelomic which often was associated with ascites. The epithelial origin of malignant ascites cells was confirmed by immunofluorescent staining with antidesmosomal antibodies and demonstration of desmosomes by electron microscopy. When transplanted into syngeneic rats, the cells of the malignant ascites resulted in the development of adenocarcinomatous metastases.

Biological activities of 5-fluorouracil and its prodrug 5'-deoxy-5-fluorouridine in rats

The antitumor activity and toxicity of 5-fluorouracil (FUra) and 5'-deoxy-5-fluorouridine (dFUR) were compared in female Fischer rats bearing transplanted dimethylhydrazine-induced colon tumors. The therapeutic effects of FUra and dFUR were not affected by the initial tumor size, but were dependent on the dose and duration of treatment. The maximal response rate of 80-90% cures was obtained with 7-day infusions of 35 mg-kg-1-day-1 FUra or 500 mg-kg-1-day-1 dFUR. The host toxicity of FUra and dFUR in tumor-bearing or normal rats included gastrointestinal and central nervous system disturbances. Toxicity related death was preceded by a greater than 20% animal weight loss and other signs of gastrointestinal disturbances. The maximal therapeutic dose of FUra was identical to the toxic dose which caused 40% death in normal rats. By contrast, the maximal therapeutic dose of dFUR did not cause toxic death, and the threshold lethal dose of dFUR was 40% higher than the maximally therapeutic dose, indicating a better therapeutic index for dFUR in this rat tumor.

Reduced incidence of rat colon cancer metastases by perioperative immunostimulation with maleic anhydride-divinyl ether-2 (MVE-2)

Intra-abdominal operations result in profound immunodepression during a period when tumor cells are released into the systemic and portal circulations. This combination may augment tumor metastases. The authors have developed a model in which rat colon carcinoma cells transplanted into the portal vein consistently induce hepatic metastases by four weeks, and death within nine weeks. Additionally, the authors have shown that perioperative treatment with levamisole significantly reduces the incidence of metastases. This study tested whether maleic anhydride-divinyl ether-2 (MVE-2), a known immunostimulant, would produce similar effects. Rats pretreated with MVE-2 the day before and day of tumor implantation developed fewer metastases (34 percent of animals treated with MVE-2, compared with 5 percent of animals not treated with MVE-2 had less than or equal to two liver metastases). Eighteen percent of MVE-2-treated rats developed no hepatic metastases. Comparison of median liver weights between the MVE-2-treated group and the nontreated, tumor-bearing group was significant (P = 0.03) and the MVE-2-treated animals had significantly prolonged survival (P = 0.04). The authors conclude that the perioperative period is critical for the implantation and growth of metastases and that perioperative immunostimulation may be a factor in decreasing the incidence of metastases. This model may have relevance to the adjuvant treatment of human colonic cancer.

Metabolism of the carcinogen 1,2-dimethylhydrazine by isolated human colon microsomes and human colon tumor cells in culture

Human colon microsomes catalyze the metabolism of the model colon carcinogen 1,2-dimethylhydrazine. Activity appears to be distributed in a gradient towards the lower end of the colon. Highest activities were observed for microsomes prepared from the descending segment of the colon with the transverse segment exhibiting lower activities, while the ascending segment showed the lowest rate of metabolism. Dimethylhydrazine metabolism in each segment is inhibited significantly by inhibitors of the cytochrome P-450-dependent mixed function oxidase system. Microsomes prepared from a human colon tumor cell also catalyze the metabolism of 1,2-dimethylhydrazine. Metabolic activity in the cell line can be induced two-fold by treatment of cells with phenobarbital and three-fold by treatment of the cells with phenobarbital plus hydrocortisone. These results show that human colon activates 1,2-dimethylhydrazine and suggest that the human colon may be capable of activating other carcinogens in situ.

Effect of preoperative intralesional BCG and postoperative 5-FU chemotherapy in three adenocarcinoma lines in rats

In No. 13762 mammary adenocarcinoma, it has been shown that the combination of tumor infiltration with BCG and of subsequent surgery is more curative than either treatment modality alone. And the administration of postoperative systemic 5-fluorouracil (D-FU) is equally effective in eliminating the visceral metastasis and prolonging the host survival. In the experiments reported here, two other spontaneously metastasizing adenocarcinoma lines were similarly treated. Postoperative 5-FU chemotherapy, but not intralesional BCG, significantly improved survival duration of rats with SMT-2A mammary adenocarcinoma, but neither chemotherapy nor BCG immunotherapy was effective in the new colonic adenocarcinoma line.

Isolation and purification of normal and malignant colonic plasma membranes

Plasma membrane fractions from normal colon cells and a transplantable colon adenocarcinoma were isolated and purified by differential and zonal density centrifugation. Enrichment of normal and adenocarcinoma plasma membranes was found in zonal fractions I and II (ZI and ZII) following centrifugation in an 18--50% sucrose gradient. The distribution of various marker enzymes in normal colon preparations suggested an apical origin for the membranes obtained in zonal fraction I while zonal fraction II appeared to contain basal-lateral membrane fragments. Enzymatic analysis of the plasma membrane derived from the colon tumor indicated that these fractions possess a more uniform distribution of Na-K+ ATPase perhaps reflecting a dedifferentiated state. The plasma membrane fractions isolated should prove useful for investigation of transport and other properties of vesicles derived from malignant and normal colon cells.

[Nitrosamin induced neoplasms of the colon and rectum. Investigations on the morphogenesis in rats (author's transl)]

The morphogenesis of neoplasms (carcinomas and pracecancerous polypoid lesions) induced by N-methyl-N-nitroso-N'-nitroguanidine (MNNG) was studied on 154 male Wistar rats (including controls), from which a group received a colostomy. Operated and non-operated rats were treated by intrarectal instillations of 2 mg per kg body weight MNNG twice a week during a period of 210 days.

Affinity chromatography of thymidine kinase from a rat colon adenocarcinoma

Thymidine kinase from a transplantable colon adenocarcinoma, induced by 1,2-dimethylhydrazine and maintained in CDF rats, was purified by affinity chromatography using thymidine-3'(4-aminophenylphosphate) coupled to carboxyhexyl-Sepharose. Most of the contaminating protein passed through the column; non-specifically adsorbed protein was washed from the column by 0.1 M KC1 in 0.01 M Tris-HC1, 7.5. Thymidine kinase was eluted with 0.1 mM thymidine, 0.1 M KC1 in 0.01 M Tris-HC1, pH 7.5. The purified enzyme accounted for about 26% of the applied activity; the specific activity of the purified material (peak fraction) was 3,500 moles TMP formed per mg protein per 10 min., a 1,800-fold purification of the applied extract. The preparation is free of nucleoside phosphotransferase, but contains other protein impurities. Purification was completed in less than 1 hour, making this a useful procedure for isolation of this unstable enzyme.