Biomedical subjects

B Shpitz

Publications and source records attributed to B Shpitz.

At least 19 recordsLinked to original sources

PubMed1999

Long-term incidence of acute myocardial infarction after open and transurethral resection of the prostate for benign prostatic hyperplasia.

PURPOSE: Acute myocardial infarction was found to be the main cause of increased long-term mortality in patients after transurethral compared to open prostatectomy in various retrospective studies. We performed a randomized prospective study to compare morbidity and incidence of acute myocardial infarction in patients after transurethral compared to open prostatectomy for benign prostatic hyperplasia. MATERIALS AND METHODS: We studied 365 patients who were assigned to transurethral (236) or open (129) prostatectomy only according to the size of the prostate and who were followed for 7 to 8 years. The clinical status of the patients in both groups before and after the operation was compared, and the rate of myocardial infarction and long-term mortality was studied. RESULTS: More patients with a history of cerebrovascular accident (5.4 versus 0.8%) and indwelling catheters (16.3 versus 7.6%) before the operation were in the open prostatectomy group. Among the 236 patients operated on transurethrally 31 were reoperated on (6 more than once) during followup compared to 4 of the 129 patients who underwent open prostatectomy. In 15 patients from the transurethral prostatectomy group myocardial infarction developed compared to 9 patients in the open prostatectomy group. This difference was not statistically significant. The rate of acute myocardial infarction after prostatectomy, no matter which approach was used, was greater than 6% and it appeared to be higher when compared to the rate of infarction in the general population of the same age group, which is approximately 2.5% in our county. There was no statistically significant difference in the overall mortality rate between the transurethral and open prostatectomy groups, which was 14.4 and 8.5% respectively. CONCLUSIONS: Open prostatectomy is more effective in overcoming urinary obstruction than the transurethral approach. No significant differences in myocardial infarction or overall mortality rates were found between the 2 groups.

Aged↗

PubMed1998

Controlled release of TGF-beta1 impedes rat colon carcinogenesis in vivo.

Transforming growth factor beta1 (TGF-beta1) is a cytokine known to play a key role in the control of cell growth. TGF-beta1 potently inhibits the proliferation of human and rodent-derived epithelial cells. Colonic precancerous and moderately differentiated cancer cells are responsive to TGF-beta1, whereas malignant colon cancer cells are resistant to the inhibitory action of the cytokine. These observations have been derived exclusively from in vitro studies. Therefore, the main aim of our study was to determine whether TGF-beta1 exerts a growth-restraining action on colon carcinogenesis in vivo. TGF-beta1 was sequestered into ethylene acetate copolymer matrices and "loaded" preparations were implanted intraperitoneally (i.p.) in rats. One week later, the animals were treated with dimethylhydrazine (DMH), a colon procarcinogen. Empty matrices devoid of TGF-beta1 but containing bovine serum albumin (BSA) carrier served as the appropriate control preparations. The number of aberrant crypt foci (ACF), considered to be preneoplastic lesions of the colon, was scored. Tumor formation and size were assessed at the appropriate times. TGF-beta1 released in a sustained manner from copolymer matrices: (i) markedly inhibited colonic ACF formation and the number of aberrant crypts and (ii) significantly reduced colonic tumor formation and size.

1,2-Dimethylhydrazine↗

PubMed1998

Chemopreventive effect of aspirin on growth of aberrant crypt foci in rats.

Nonsteroidal anti-inflammatory drugs display a chemopreventive effect on polyps and cancer of the large bowel. This study evaluated the inhibitory effect of aspirin on the distribution and growth of aberrant crypt foci (ACF), the earliest putative preneoplastic and early neoplastic lesions in a rat model. For initiation of ACF, Sprague Dawley rats were injected with azoxymethane (30 mg/kg), a well-established rat carcinogen. After the second injection the rats were allocated to three groups, which received 0.2% or 0.6% aspirin or the solvent only (control group). After 6 weeks the animals were killed, and their colons removed, fixed in formalin, and screened for distribution and size of ACF, separately for middle and distal parts of the large intestine. The rats injected with azoxymethane showed a 100% incidence of ACF. Administration of 0.2% and 0.6% aspirin resulted in 55% and 54% reduction, respectively, in overall frequency of ACF. Aspirin significantly reduced the frequency of medium-sized (four to six crypts per focus) and large (three to six crypts per focus) but not the small (one to three crypts per focus) ACF. In the control group the ACF of the same multiplicity were larger than those in the aspirin-treated rats. No statistically significant difference in ACF-inhibiting effect was noted between 0.6% and 0.2% aspirin solution. Aspirin given at a concentration of either 0.2% of 0.6% thus has a chemopreventive effect on ACF, acting on postinitiation stage of azoxymethane-induced colonic carcinogenesis model in rats.

Animals↗

PubMed1998

Aberrant crypt foci in human colons: distribution and histomorphologic characteristics.

Aberrant crypt foci (ACF) are one of the earliest putative preneoplastic, and in some cases, neoplastic lesions in human colons. These microscopic lesions, identified on methylene blue-stained mucosa with a low-power-magnification microscope, are thought to be closely related to the earliest steps in multistage colonic tumorigenesis. We investigated the distribution pattern and histomorphological features of ACF in 74 patients with sporadic colorectal cancer. The distribution pattern shows a slightly higher prevalence with older age. The prevalence of the ACF in sigmoid colon was significantly higher in patients with colorectal cancer as compared with patients with benign colonic diseases. Also, significantly more ACF were detected in distal parts of the large bowel (descending, sigmoid colon, and rectum) than in proximal parts. Of 42 microdissected lesions, 12 were dysplastic and 30 were hyperplastic foci. The average size of dysplastic lesions was significantly larger than hyperplastic foci. More apoptotic bodies were found in dysplastic lesions. These lesions also showed an upward expansion of proliferative compartment and higher proliferation indices expressed as proliferating cell nuclear antigen-labeling index. Lymphoid follicles were frequently observed in the base of both hyperplastic and dysplastic foci (40% and 66.6%, respectively). The coincidence of lymphoid follicles was 2.5 to 8 times higher than expected. These features may be related to further progression of selected ACF during colorectal tumorigenesis.

Adult↗

PubMed1997

Physiologic human T-cell responses to OKT3 in the human peripheral blood lymphocyte-severe combined immunodeficiency mouse model.

BACKGROUND: Our goal was to study physiologic responses of human T lymphocytes to OKT3 in the human peripheral blood lymphocyte-severe combined immunodeficiency (hu-PBL-SCID) mouse model. METHODS: SCID mice were pretreated with anti-asialo-GM1 (alpha-ASGM1) and radiation, then engrafted with human peripheral blood lymphocytes (PBLs). Seven to 14 days after engraftment, when most human T cells in the spleen of these mice are CD3+/CD4+ and CD3+/CD8+, mice were treated with OKT3 or control antibody. Mice were killed for histopathologic examination, for flow cytometric assessment of the engrafted human lymphocytes, and for analysis of human tumor necrosis factor-alpha serum levels. RESULTS: Intravenous injection of 5 microg of OKT3 resulted in early antigenic modulation of engrafted human T lymphocytes, with the emergence of CD3-/CD4+ and CD3-/CD8+ cells in the spleen of hu-PBL-SCID mice. There was an increase in the serum concentration of human tumor necrosis factor-alpha within 4 hr after OKT3 injection, suggesting early T-cell activation. Antigenic modulation and activation of the human lymphocytes in the spleen was followed by their depletion within 24 hr. This human T-cell response to OKT3 in hu-PBL-SCID mice is analogous to the response in humans treated with OKT3 and in BALB/c mice injected with an anti-murine CD3 monoclonal antibody. Graft-versus-host disease in the mice was abrogated by OKT3 treatment, and OKT3-treated mice lived longer than controls. Histopathologic studies showed clearance of lymphocytic infiltration in the liver and lungs of OKT3-treated mice. CONCLUSIONS: These findings provide further evidence of functional human immune T cells in the hu-PBL-SCID mouse. This model may have useful applications in the study of transplantation immunology.

Animals↗

PubMed1997

Proliferating cell nuclear antigen as a marker of cell kinetics in aberrant crypt foci, hyperplastic polyps, adenomas, and adenocarcinomas of the human colon.

BACKGROUND: One of the first steps in multistage colonic carcinogenesis is increased cell proliferation and an upward shift of the proliferation zone of colonic crypts. In the present study, progression in cell kinetics was followed up at all sequential stages of colonic carcinogenesis, starting with aberrant crypt foci (ACF), the earliest putative preneoplastic lesions, hyperplastic and dysplastic polyps, and invasive carcinomas. MATERIALS AND METHODS: Colonic tissue and tumor specimens were prospectively obtained from 65 patients treated at our hospital for adenocarcinoma or malignant polyps. For identification of ACFs, dissected mucosal strips obtained from patients with colorectal cancer were stained with 0.1% methylene blue and scanned under dissecting microscope. Paraffin-embedded ACFs and macroscopic lesions were serially sectioned, deparaffinized, and stained with a monoclonal antiproliferating cell nuclear antigen (PCNA) antibody. The PCNA-labelling index (PCNA-LI), expressed as a ratio of positively stained nuclei to total nuclei counted, was calculated separately for basal, middle, and upper colonic crypt compartments. A comparison of the PCNA-LI was made for each compartment in normal mucosa, and hyperplastic and dysplastic lesions. RESULTS: A stepwise increase in the PCNA-LI was observed during neoplastic progression of colonic lesions. The two most important variables of increased cell proliferation, expressed as PCNA-LI per crypt compartment, were the presence of dysplasia and the size of dysplastic lesions. CONCLUSIONS: In colorectal carcinogenesis, hyperproliferation with upward expansion of proliferative compartment is a characteristic feature at all stages of malignant progression.

Adenocarcinoma↗

PubMed1996

Cytotoxicity of B72.3XOKT3 bispecific antibody recognizing human colon cancer.

Bispecific monoclonal antibodies can be used to redirect peripheral blood lymphocytes against tumor cells. In the present study, a murine bispecific monoclonal antibody was developed using somatic hybrydization. The antibody has two different binding arms: one arm directed against human CD3 receptor expressed on T-lymphocytes and the other against tumor associated glycoprotein TAG-72, expressed on human carcinomas, such as colon, breast, and pancreas. Partially purified antibody was capable of inducing human T-cell proliferation and preventing growth of colon cancer cell line in nu/nu mice in a tumor neutralization assay.

Animals↗

PubMed1996

Natural history of aberrant crypt foci. A surgical approach.

BACKGROUND: The aberrant crypt focus (ACF) appears to be an important early step in colorectal carcinogenesis. Our objectives were to determine the natural history of ACF in a surgical model. METHODS: The natural history of ACF was followed by marking the lesions in vivo with tattoos. Rats were given four weekly injections of azoxymethand (AOM; 20 mg/kg). One hundred days after the first injection of AOM, rats were anesthetized, and individual aberrant crypt focus was identified by staining with methylene blue. A 3 x 3 mm area, identifying one large (4-8 crypts) ACF was marked with a tattoo dye in each colon. Control animals received saline or AOM injections and were tattooed in areas without ACF. At 200 days, colons were examined for the presence of macroscopic lesions. RESULTS: A total of 54 tumors were found in the study group of 38 animals, and 21 of these were in the transverse and proximal descending colon. The marked areas (all in transverse and proximal descending colon) yielded 6 tumors and 2 ACF, but in 30 instances no abnormality was noted. Probability of observing a tumor in the 3 x 3 mm area of the colon that was identified as containing ACFs was 17 times greater than expected from the observed tumor rate in approximately the same zone (16 vs. 1.7 percent; 95 confidence interval, 10 to 22 and 0.5 to 1.3 percent). Twenty control animals receiving saline had no tumors of epithelial origin. Nine control animals that were carcinogen-treated and tattooed in areas without ACF had no tumors in the marked areas. CONCLUSION: Results thus show regression of many ACF identified early in the carcinogenesis process. Results also support the hypothesis that some ACF are precursor lesions for adenomas and cancers.

Adenoma↗

PubMed1995

A human model of xenogeneic graft-versus-host disease in SCID mice engrafted with human peripheral blood lymphocytes.

Despite previous attempts there is currently no suitable animal model available for xenogeneic graft versus host disease (XGVHD) mediated via human immunocompetent cells. Recently, we have developed an efficient protocol to engraft SCID mice with human peripheral blood lymphocytes (Hu-PBLs). The engraftment efficiency is extremely high, such that 100% of Hu-PBL-SCID mice die of XGVHD within 4 weeks after engraftment with Hu-PBLs (3-5 x 10(7) cells). A series of experiments was performed to investigate the mechanisms involved in the severe XGVHD. The results suggest that XGVHD was induced by human CD4+ T cells, antixenogeneic (antimouse) antibodies, and lymphokines. The SCID mouse model will be extremely valuable for the evaluation and development of immunosuppressive agents and transplantation protocols for human XGVHD.

Animals↗

PubMed1995

Mastectomy as the preferred treatment for breast cancer among new immigrants from the former USSR.

Sixty-four new immigrant patients with primary breast cancer who arrived in Israel since 1990 were compared to 322 Israeli women with primary breast cancer. New immigrant patients had a more advanced stage at diagnosis (stage III+IV 28% vs. 13% respectively, P = 0.00005); larger mean tumor size (3.08 +/- 1.7 cm vs. 2.25 +/- 1.4 cm respectively, P = 0.00002); and more involved lymph nodes (3.8 +/- 5.3 vs. 1.8 +/- 3.3 P = 0.0002). Forty-seven percent of new immigrants had breast-conserving surgery compared to 69% of the Israelis (P = 0.0004). In stage II 51% of the new immigrants had conservative surgery compared to 74% in the Israeli group (P = 0.03). Mastectomy was recommended to 39 Israeli patients and to six immigrants. Only 19% of the Israeli group requested mastectomy compared to 44% in the new immigrant group. Most of the new immigrant patients chose mastectomy although breast-conserving surgery was an equal alternative. The reasons for choosing mastectomy as the preferred mode of treatment were related to economic problems, different life concepts, and other priorities. Constant surveillance and considerable enlightenment are needed in the new immigrant population, so that they will be able to separate the disease and its treatment from their paramedical problems.

Breast Neoplasms↗

PubMed1995

In vitro and in vivo evaluation of streptavidin immunoconjugates of the second generation TAG-72 monoclonal antibody CC49.

Streptavidin was conjugated to the second-generation TAG-72 monoclonal antibody CC49 at lysine amino acids, oxidized carbohydrates or reduced disulfides on the immunoglobulin. The streptavidin immunoconjugates were radiolabelled with 111In-DTPA-biocytin and their immunological characteristics evaluated in vitro and in vivo. FPLC analysis showed a single peak (mol. wt > 350 kDa) for the lysine conjugate and sulfhydryl conjugate (mol. wt approximately 210 kDa) but multiple peaks (approximately 210 to > 350 kDa) for the carbohydrate conjugate. There were only small differences in immunoreactivity against bovine submaxillary mucin in vitro. However, in mice bearing subcutaneous LS174T tumours, the lysine conjugate exhibited significantly lower tumour uptake (< 2% i.d./g) compared to the other streptavidin-CC49 conjugates (10-40% i.d./g) or DTPA-CC49 (14-18% i.d./g). Due to the monomeric nature and smaller molecular size of the sulphhydryl conjugate, and its similar in vitro and in vivo characteristics compared with DTPA-CC49, this conjugate has been selected for future pretargeting studies with 111In and 90Y biotin.

Animals↗

PubMed1995

Acute cholecystitis in diabetic patients.

Postoperative outcome and severity of acute cholecystitis in 32 diabetic patients (DM) who underwent urgent cholecystectomy were compared on a case-control basis with 32 nondiabetic age/sex matched controls. There was no difference in incidence of renal and lung diseases or duration of acute symptoms before surgery. Cardiovascular diseases were more often seen in the diabetic group (16/32 in DM, 7/32 in controls, P = 0.03). Bactobilia was more often in diabetics (19 in DM, 11 in controls, p = 0.07). Postoperatively, there was a trend toward higher incidence in overall complication rate. Infectious complications (wound and respiratory infections, hepatic abscess) were higher in DM, although the difference was not statistically significant. One patient in DM group died as a result of multiorgan failure. There was no difference in total and postoperative hospital stay. The severity of acute cholecystitis was greater in diabetics (26 patients with moderate-to-severe cholecystitis in DM group, 18 in control group, P = 0.05). The study indicates that although pathological findings were more severe in DM group, the postoperative course is comparable in diabetics as compared to age and sex matched nondiabetic controls. Our findings justify reconsideration of prophylactic cholecystectomy in asymptomatic diabetic patients.

Acute Disease↗

PubMed1994

Human primary immune response in SCID mice engrafted with human peripheral blood lymphocytes.

Severe combined immune deficient (SCID) mice were engrafted with human peripheral blood lymphocytes (Hu-PBLs) after treatment with anti-asialo GM-1 antiserum and radiation. This pretreatment facilitates high level of Hu-PBL engraftment in the SCID mice spleen. The next day, the Hu-PBL-SCID mice were immunized with either keyhole limpet hemocyanin (KLH), or carbohydrate Ag STn (AcNeu-alpha 2-alpha 6-Gal NAc-0) conjugated to KLH or protein of circumsporozoite malaria parasite (CSP), in a mixture of complete and incomplete Freund's adjuvant (1:10 v/v). The mice were bled 14 to 16 days after immunization, and the sera analyzed for STn-, KLH-, and CSP-specific human IgG and IgM Abs. The results showed that the immunized animals had a significantly higher titer of Ag-specific human IgG and IgM Abs compared to the control Hu-PBL-SCID mice. No significant Ab cross-reactions were detected between sera from KLH-, STn-, and CSP-vaccinated Hu-PBL-SCID mice. Depletion of either human CD4+ or CD8+ cells, in Hu-PBL-SCID mice, showed that CD4+ cells were essential for the primary immune response, but depletion of CD8+ cells had no influence on the titer of Ag-specific human IgG and IgM Abs.

Animals↗

PubMed1994

High level functional engraftment of severe combined immunodeficient mice with human peripheral blood lymphocytes following pretreatment with radiation and anti-asialo GM1.

The severe combined immunodeficient (SCID) mouse engrafted with human peripheral blood lymphocytes (PBLs) is a potentially useful model for the study of cancer immunotherapy. For this application, rapid, consistent, and high level engraftment of SCID mice with functional human cytotoxic effector cells is necessary. To date, short term human lymphoid cell engraftment in SCID mice has generally been low and variable. Further, most of the human cells detected within the first 30 days are found in the peritoneal cavity. The purpose of the present study was to improve short term reconstitution of human PBLs in the SCID mouse. When untreated SCID mice were injected with human PBLs, the mean level of CD3+ cells in the spleens was < 5% on days 6-32 after injection, as determined by flow cytometry (FCM). Depletion of SCID mouse natural killer (NK) cells with anti-asialo GM1 only marginally improved short term reconstitution with human CD3+ cells. Preirradiation of SCID mice with 3 Gy improved reconstitution to over 16% CD3+ cells on days 12-14 following engraftment. However, the combination of pretreatment with anti-asialo GM1 plus radiation, significantly increased the mean percentage of human CD3+ cells in the spleen to 40% within 2 weeks following injection of PBLs. Human T cells positive for CD4, CD8, TcR alpha beta, and TcR gamma delta, and human NK and B cells were detected in the spleens of irradiated plus anti-asialo GM1 pretreated SCID mice. The presence of human lymphoid cells was confirmed by immunohistologic staining. The human immune cells in these mice were shown to be functional by the in vivo demonstration of an appropriate secondary immune response to the injection of tetanus toxoid and by an in vivo proliferative response to phytohemagglutinin. Human NK cells could be found in the spleens and peripheral blood of irradiated plus anti-asialo GM1 pretreated mice. These cells were also shown to be competent by their ability to lyse the human NK sensitive tumor targets K562 and MOLT-4 in 51Cr release assays. Thus, pretreatment of SCID mice with radiation plus anti-asialo GM1 significantly improves short term human PBL engraftment and provides a potentially useful model for the study of cancer immunotherapy.

Animals↗

PubMed1994

Triple approach in the diagnosis of dominant breast masses: combined physical examination, mammography, and fine-needle aspiration.

In an attempt to reduce the number of breast biopsies done for benign breast disease in patients with breast lumps, we evaluated prospectively the sensitivity and specificity of the combination of three diagnostic modalities: clinical examination, mammography, and fine-needle aspiration cytologic examination (FNA). A total of 234 patients with a breast mass had a physical examination, a mammogram, and FNA, and were listed as malignant/suspicious or benign. All patients underwent a subsequent biopsy: 110 were found to have breast cancer, and 124 had a benign lesion. The sensitivity and specificity of the individual tests were as follows: 89% and 73%, respectively, for mammographic examination; 93% and 97% for FNA cytologic examination; and 89% and 60% for physical examination. For the combined triad of tests, the sensitivity was 100% and specificity 57%. All patients who had breast cancer had positive findings for malignancy in one or more of the diagnostic tests, i.e., 100% sensitively. All patients who had negative findings for malignancy in all three diagnostic tests had benign lesions, i.e., a negative predictive value of 100%. We conclude that breast masses can be diagnosed with a high degree of accuracy by combined physical, mammographic, and fine-needle aspiration cytologic examination. Patients in whom physical examination, mammography, and FNA were negative for malignancy can be safely observed, obviating the need for an open biopsy.

Adult↗

PubMed1994

Immunoscintigraphy of human colon cancer xenografts in nude mice using a second-generation TAG-72 monoclonal antibody labelled with 99Tcm.

Monoclonal antibody CC83 is a second-generation high-affinity antibody directed against the TAG-72 antigen in colorectal cancer. Our objectives were to evaluate the biodistribution, pharmacokinetics and imaging properties of CC83 labelled with 99Tcm via a modified Schwartz technique. The immunological integrity of 99Tcm-CC83 was evaluated by size-exclusion FPLC and by determining the immunoreactive fraction in vitro against bovine submaxillary mucin. The biodistribution of 99Tcm-CC83 up to 24 h postinjection was evaluated in nude mice bearing subcutaneous LS174T human colon cancer xenografts. Blood radioactivity data was fitted to a one-compartment pharmacokinetic model. Images of tumour-bearing mice were obtained at 17-24 h postinjection with 99Tcm-CC83. 99Tcm-CC83 was eluted as intact immunoglobulin by FPLC analysis and the mean immunoreactive fraction was 0.49 +/- 0.15. Tumour uptake at 24 h postinjection was 11.2 +/- 4.1% i.d.g-1. Radioactivity in the blood was eliminated rapidly with a half-life of 8 h and tumour:blood ratios were > 2:1 at 24 h postinjection. LS174T tumours were successfully imaged in 3/3 mice. In vitro studies showed instability of 99Tcm-CC83 when challenged with cysteine and glutathione but not metallothionein, suggesting a metabolic route for the 99Tcm antibody in vivo. We conclude that CC83 labelled directly with 99Tcm retains its immunological integrity and capability specifically to target subcutaneous LS174T human colon cancer tumours hosted in nude mice. These results further suggest that 99Tcm-CC83 may have potential for imaging colorectal cancer in humans.

Animals↗

PubMed1993

Comparative dual label study of first and second generation antitumor-associated glycoprotein-72 monoclonal antibodies in colorectal cancer patients.

Radiolabeled first-generation anti-tumor-associated glycoprotein-72 (TAG-72) monoclonal antibody (MAb), B72.3, has proven useful in detecting primary and secondary colorectal carcinoma. It has been anticipated that the development of second-generation, higher affinity, anti-TAG-72 MAbs, CC49 and CC83, would be of greater use in cancer detection and of value in radioimmunotherapy of human cancer. We compared the pharmacokinetics, biodistribution, and immune responses of 131I-labeled CC49 and CC83 to 125I-labeled B72.3 by preoperatively coninjecting dual-labeled MAbs into 16 colorectal cancer patients. The imaging properties of radiolabeled CC49 and CC83 were also assessed. Pharmacokinetics of all three MAbs were identical, and there were no differences in the uptake of any of three MAbs in tumor and normal tissues. Maximum tumor uptake was 0.0041% of the injected dose/g for 125I-B72.3, 0.0024% for 131I-CC49, and 0.0029% for 131I-CC83. Radiolabeled CC49 and CC83 detected most known tumor sites on scintigrams without any clear advantage for either MAb. Nonspecific splenic and testicular uptake was frequently observed. Anti-idiotypic human anti-mouse antibody responses were seen more frequently with B72.3 than with CC49 or CC83. We conclude that higher affinity, radiolabeled anti-TAG-72 MAbs can detect colorectal cancer but do not penetrate these tumors more effectively than B72.3. Improvements in tumor detection and radioimmunotherapeutic strategies will likely require the administration of smaller fragments of MAb molecules or novel delivery systems rather than the continued development of higher affinity MAbs.

Adult↗

PubMed1993

K-ras mutations in aberrant crypt foci, adenomas and adenocarcinomas during azoxymethane-induced colon carcinogenesis.

Ras mutations are an important early event in a number of carcinogen-induced rodent tumors. Colon carcinogenesis induced in rats by azoxymethane is a useful model as it mimics the adenoma-carcinoma sequence observed in humans. In addition, aberrant crypt foci develop in the rat and these lesions appear to be potentially important precursors to adenomas in colorectal cancer. Recent studies have shown that specific K-ras codon 12 and 13 mutations are present in up to 66% of carcinogen-induced rat colon adenocarcinomas. We studied the frequency of these mutations during the aberrant crypt focus-adenoma-carcinoma sequence in azoxymethane-induced Fisher F344 rats. K-ras codon 12 GAT and codon 13 GAC mutations were detected with a sensitive assay based on the amplification of DNA using the polymerase chain reaction. No mutations were present in normal mucosa. Of 27 aberrant crypt foci, K-ras mutations were identified in 2 lesions containing 5 and 10 aberrant crypts, respectively. Mutations were present in 1 of 23 and 10 of 27 adenomas and adenocarcinomas, respectively. These data suggest that K-ras mutations play a role during the stages of carcinogenesis in azoxymethane-induced rat colon cancer. The demonstration of a genetic mutation in aberrant crypt foci provides further evidence for the significance of these lesions as precursor markers of malignant potential during colorectal tumorigenesis.

Adenocarcinoma↗