Yonit Bomstein

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.

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.

Angiogenesis, p53, and c-erbB-2 immunoreactivity and clinicopathological features in male breast cancer

p53, c‐erbB‐2, and tumor microvascular density have been shown to be potential prognostic tools in female breast cancer. Our objective was to assess the significance of these biomarkers as prognostic factors in infiltrating male breast cancer.

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

Abstract 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.

The antiapoptotic effects of blood constituents in patients with chronic lymphocytic leukemia

Objective: Clonal B‐lymphocytes of chronic lymphocytic leukemia (B‐CLL) are characterized by decreased sensitivity to programmed cell death and, therefore, they accumulate in vivo. However, these malignant cells die rapidly in vitro. In the current study we concentrated on the contribution of autologous serum (AS) and lymphocyte subsets to the survival of the malignant cells in vitro.

Analysis of chromosomal aberrations in large hepatocellular carcinomas by comparative genomic hybridization

Hepatocellular carcinoma (HCC) is a very common and highly malignant tumor, associated mainly with chronic viral hepatitis, cirrhosis of any cause, aflatoxin exposure and ethanol consumption. The aim of this study was to map genomic aberrations in HCC by a recently developed technique: comparative genomic hybridization (CGH). We applied CGH on 17 liver specimens, of which seven were HCCs. The rest were benign liver tumors, cirrhotic and normal livers, and other liver malignancies. Our study included mainly large tumors (mean size 10.5 cm) unrelated to viral hepatitis or cirrhosis. Our CGH analysis detected genomic imbalances in 42% of HCCs. The common aberrations included DNA gains of 1q, 9p, and 8q and DNA losses of 17p, 13q, 9q, 4q, and 11q. Also, we detected trisomies 8, 9, 18 and 21, which have not been reported previously. Gains and losses of DNA found in this study probably involve oncogenes and tumor suppressor genes that play a role in the puzzle of hepatocarcinogenesis. This study also suggests a possible link between the size of the tumor and the burden of genetic changes.

Comparative genomic hybridization in polycythemia vera and essential thrombocytosis patients

Polycythemia vera (PV) and essential thrombocytosis (ET) are clonal chronic myeloproliferative disorders originating from a multipotent stem cell. Bone marrow examinations reveal chromosomal abnormalities in 15-43% of PV patients and 5% of ET patients, but no specific recurring abnormality has been found to date. We aimed to find cytogenetic aberrations in PV and ET by comparative genomic hybridization (CGH), a relatively new molecular cytogenetic technique. In this study, CGH analysis was performed on peripheral blood leukocytes of 12 PV patients and 8 ET patients. One patient (8.3%) with PV had an abnormal karyotype with a deletion in 7q11.2 and one patient with ET (12.5%) had a gain in 18p. Peripheral blood analysis by CGH revealed a low frequency of cytogenetic abnormalities in PV and ET patients. However, using CGH we were able to detect two cytogenetic aberrations that were not reported previously in these disorders.

Altered expression of the DNA mismatch repair proteins hMLH1 and hMSH2 in cutaneous dysplastic nevi and malignant melanoma

Molecular alterations in the mismatch repair system suggest that this mechanism may be important in the evolution of cutaneous melanoma. Our current study evaluated the expression of two mismatch repair proteins, hMLH1 and hMSH2, in dysplastic nevi (DN) and cutaneous melanoma (CM). Immunohistochemical staining of these proteins was performed on 55 CM and 30 DN specimens. The staining results were divided into three groups: negative, partially positive and strongly positive. Normal adjacent skin cells served as an internal control for positive immunostaining. Altered immunoreactivity of one of the proteins was found in four (13.4%) DN and seven (12.7%) CM. Lack of staining for hMLH1 was observed in two (6.7%) cases of DN and five (9.1%) cases of CM; staining for hMSH2 was absent in two (6.7%) of the DN and two (3.6%) of the CM specimens. Partially positive staining was found in 33.3% and 53.3% for hMLH1 and hMSH2, respectively, in DN, and in 54.5% and 69.1%, respectively, in CMM. Our study shows that complete or partial loss of MMR protein expression occurs in a subset of both DN and CM and may represent a distinct pathway in the development of some DN and CM.

Microsatellite instability in gastric MALT lymphoma

The role of microsatellite instability and defects in DNA mismatch repair mechanism in the pathogenesis of gastric lymphoma of mucosa-associated lymphoid tissue (MALT) type is still controversial, as both negative and positive findings have been reported. This may be explained mainly by arbitrary selection of the tested loci, the use of various techniques of microsatellite instability analysis and by different definitions of replication error positive phenotype. The aim of our study was to evaluate the instability at selected microsatellite markers using the GeneScan Analysis Software. DNA from paraffin-embedded tissue blocks of 13 previously untreated patients with localized gastric MALT lymphoma was extracted. Five microsatellite markers, which are located in hMSH2, hMLH1, P16, APC and MLL loci, were selected from the genetic database. We found genetic instability in tumors of 9/13 patients with gastric MALT lymphoma (69%). Seven of them had replication-error-positive phenotype (54%). Microsatellite instability was found in 39% of the samples in the MLL locus, 39% in the APC, 46% in the P16, 23% in the hMLH1 and none in the hMSH2. This study demonstrates that microsatellite instability has more prominent role in pathogenesis of gastric MALT lymphoma than reported to date. We suggest that microsatellite instability should be analyzed with markers adjacent to chromosomal loci that are involved in lymphomas. Our findings support the ‘Real Common Target genes’ theory of high rate of microsatellite instability in specific genes, which are associated with related tumors.

Regulation of heme synthesis in the regenerating rat liver.

This investigation shows that the regulation of heme synthesis in the regenerating rat liver does not differ from the regulation in the normal liver. The heme saturation of tryptophan pyrrolase was found to be low, indicating a reduced concentration of heme in the regulatory heme pool of the regenerating rat liver. As expected, ALAS in the mitochondrial fraction was found to be elevated. It was also shown that ALAS in the regenerating rat liver can be induced by the porphyrinogenic drugs AIA and DDC and that heme reduces its activity. The decrease observed in the activity of cytosolic ALAS might be due to impaired synthesis of the enzyme but does not affect the regulation of the heme biosynthetic pathway.