Distinct prevalence of the CYP19 Delta3(TTTA)(7) allele in premenopausal versus postmenopausal breast cancer patients, but not in control individuals

The CYP19 gene encodes the enzyme aromatase, which plays a key role in the conversion of androgens to oestrogens. A polymorphism in CYP19 in intron 4 (TTTA)n has been reported to be associated with breast cancer (BC) risk, although conflicting evidence has also been published. Here, we employ a non-traditional, highly demonstrative design of a molecular epidemiological study, where the comparison of BC cases and healthy middle-aged female donors was supplemented by an analysis of groups with extreme characteristics of either BC risk (bilateral breast cancer (biBC) patients) or cancer tolerance (tumour-free elderly women aged >or=75 years). None of the (TTTA)n polymorphic variants was significantly overrepresented among the affected women compared with any of the control groups. However, a 3-bp deletion/insertion CYP19 polymorphism, which is located in the same intron approximately 50 bp upstream to the (TTTA)n repeat, was evidently associated with the menopausal status in both the BC and biBC cohorts. In particular, the Delta3(TTTA)(7) allele occurred significantly more frequently in premenopausal than in postmenopausal BC patients (65/172 (38%) versus 67/310 (22%); P=0.0001; Odds Ratio (OR)=2.20 (95% Confidence Interval (CI) 1.46-3.32)), while the perimenopausal cases demonstrated an intermediate value (9/34 (26%)). In the biBC cohort, women who developed both tumours during their premenopausal period had a significantly higher prevalence of the Delta3(TTTA)(7) allele than patients with a postmenopausal onset of bilateral disease (16/46 (35%) versus 8/50 (16%); P=0.035; OR=2.80 (1.08-7.23)); those biBC patients, whose tumours were diagnosed before and after the cessation of menses, displayed an intermediate occurrence of the Delta3(TTTA)(7) allele (7/32 (22%)). Similar tendencies in the Delta3(TTTA)(7) allele distribution in BC and biBC patients suggest that its association with the menopausal status of the patients is truly non-random and thus this observation deserves further detailed investigation.

Tissue transglutaminase expression in breast carcinomas

Tissue transglutaminase (tTG) is known to participate in multiple cellular processes, including apoptosis, cellular adhesiveness etc. Alterations of tTG expression could contribute to the development of several categories of diseases, including AIDS, cancer etc. The aim of the study was to test the pattern and relevance of tTG expression in a subset of breast carcinomas. RT-PCR has detected tTG-specific RNA message in 11 out of 25 (44%) breast cancer samples. tTG message was detected in 6/8 (75%) breast carcinomas with high apoptotic index, but only in 5/17 (29%) with the low one (p = 0.03). Immunohistochemical analysis revealed that only 15% of breast carcinomas displayed tTG protein in tumor cells, while the staining of the stromal components occurred in approximately one-half of the tumours tested. Surprisingly, there was no significant association between tTG RNA expression and protein positivity. Moreover, there was no evident relationships between tTG immunostaining and apoptotic index or clinical parameters of breast neoplasms. There are at least 2 alternative explanations for the poor concordance between RNA and protein data. It is likely that the sensitivity of immunohistochemistry is not sufficient to detect functionally relevant tTG enzyme in all breast cancer sections. Otherwise, tTG RNA expression does not always lead to accumulation of its product in the tumor cells, but reflects the transcriptional activation of other pro-apoptotic genes due to common triggering mechanisms.

Evidence for microsatellite instability in bilateral breast carcinomas

The molecular pathogenesis of various categories of breast cancer (BC) has been well described, but surprisingly few reports have appeared on analysis of somatic mutations in bilateral BC. We have performed a polymerase chain reaction (PCR)-driven investigation of chromosomal regions showing common loss of heterozygosity (LOH) in 23 cases (46 tumors) from patients diagnosed with bilateral BC. LOH was observed in 15/46 (33%) informative tumors for chromosome 1p, 5/32 (16%) for 5q, 12/44 (27%) for 11q, 15/40 (38%) for 13q and 4/24 (17%) for 17p. These values are within the range of interlaboratory variations reported for unilateral BC. There was no strong evidence for concordance of LOH within the same patient for any of the chromosomal loci tested. Atypical for breast carcinomas, 7/46 (15%) tumors accumulated a high frequency (ranging from 11 to 29%) of shortened dinucleotide CA repeats, implying microsatellite instability (MI). Further analysis with the highly informative BAT-26 marker allowed for the classification of two of these tumors as having a replication error positive (RER(+)/MSI-H) phenotype, whereas the remaining five carcinomas harbored so-called borderline MI. Thus an involvement of both RER(+) and borderline MI appears to be a distinct feature of bilateral breast carcinomas compared to unilateral lesions.

Aromatase in breast cancer tissue--localization and relationship with reproductive status of patients

The precise place of local estrogen production in mammary cancer is still controversial. In this investigation localization of aromatase (the key enzyme of estrogen biosynthesis) was studied in breast cancer tissue by immunohistochemical method using polyclonal rabbit antibodies. The cytoplasmic staining was found in different cell types, but the most intensive specific staining was found in malignant cells and it was stronger (P < 0.01) in postmenopausal patients than in patients of reproductive age.

Wild type neu transgene counteracts mutant homologue in malignant transformation of rat Schwann cells

Mutational activation of the neu (erbB-2) receptor protein tyrosine kinase gene appears to be the triggering event in the process of oncogenesis induced by N-ethyl-N-nitrosourea (EtNU) in immature Schwann cells of the rat peripheral nervous system. Subsequent loss of the wild-type neu allele may represent a critical secondary step towards malignancy. Developmentally-regulated expression of a wild-type rat neu transgene (neu cDNA under the control of the rat Po promoter) in the Schwann cells of transgenic BDIX and Sprague-Dawley rats exposed to EtNU on postnatal day 1 results in a lower incidence of early atypical proliferates in the trigeminal nerve. Furthermore, re-introduction of the wild-type neu gene into homozygous neu mutant schwannoma cells counteracts the expression of the tumorigenic phenotype. The suppressive action of the wild-type gene over its mutationally activated oncogenic homologue underlines the critical function of the neu gene in the control of differentiation in the Schwann cell lineage, and provides evidence for the responsiveness of cellular phenotypes towards quantitative shifts in the dosage of wild-type vs mutant signal transducing molecules.

Development of malignant fibrous histiocytoma induced by 7,12-dimethylbenz[a]anthracene in the rat: characterization of early atypical cells

Morphologically atypical cells were first detected in the adjacent connective tissue 98 days after implanting a paraffin pill containing 2 mg of 7,12-dimethylbenz[a]anthracene (DMBA) into the subcutaneous tissues of rats. These cells subsequently formed groups and finally produced gross malignant fibrous histiocytomas (MFH). Early atypical cells were located between proliferating fibroblasts and histiocytes in the center of a fibrous capsule surrounding the DMBA pill. They exhibited a smooth cell surface, dilated rough endoplasmic reticulum, multiple Golgi complexes, and were often associated with newly formed collagen. These cells incorporated [3H]thymidine and [3H]proline intensively, and showed weak acid phosphatase activity but no features diagnostic of macrophages (microvilli, numerous lysosomes, high acid phosphatase and non-specific esterase activities, antigens recognized by monoclonal antibodies ED1 and OX-42 and vital staining with trypan blue). There was no evidence that atypical cells differentiated into muscle cells (no expression of desmin or the alpha-sarcomeric form of actin) or Schwann cells (no expression of S-100 protein). No point mutation in the neu gene at nucleotide 2007, specific for N-ethyl-N-nitrosourea- and DMBA-induced malignant rat schwannomas, was detected by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analyses. These results support the view that malignant fibrous histiocytoma is derived from immature fibroblasts exhibiting pronounced phenotypic diversity during the later stages of carcinogenesis.

Rat model of the human "Triton" tumor: direct genetic evidence for the myogenic differentiation capacity of schwannoma cells using the mutant neu gene as a cell lineage marker

Spontaneous myogenic differentiation was observed in 2 out of 15 cases when cells from schwannomas induced in the offspring of BDIX rats by transplacental exposure to N-ethyl-N-nitrosourea (EtNU) were grown in monolayer culture following fluorescence-activated cell sorting with monoclonal antibody (Mab) 217c. Myotubes and numerous mononucleated cells no longer expressed the Schwann cell antigens 217c and S-100 protein, but rather revealed the presence of desmin, the alpha-sarcomeric form (alpha-sr) of actin, and the cell surface antigen specified by Mab RB21-7, a 250 kD glycoprotein sharing an epitope with the neural cell adhesion molecule (N-CAM). Subcutaneous reimplantation of such cells into syngeneic animals led to the appearance of tumors composed of both S-100 positive Schwann cells and desmin and alpha-sr-actin positive rhabdomyoblasts, thus closely resembling the human "Triton" tumor. With the use of the polymerase chain reaction and allele-specific oligonucleotide hybridization, DNA isolated from individual myotubes was analyzed for the presence of a T----A transversion mutation at nucleotide 2012 of the neu gene, which is diagnostic of EtNU-induced rat schwannomas. All of the amplified DNA isolates contained the mutant neu allele, thus providing direct genetic proof for the capacity of mammalian neuroectodermal cells for myogenic differentiation.

Effects of misclerone (clofibrate) on dimethylhydrazine-induced intestinal carcinogenesis in rats

Intestinal tumors were induced by treatment with dimethylhydrazine (DMH) (14 mg with reference to base/kg body weight, weekly, s.c., for 20 weeks) in male rats supplied by Rappolovo Animal Farm. Some of the animals received 25 mg/day of misclerone (clofibrate) per os, 5 times a week. Clofibrate treatment did not affect the frequency of tumors of the large and small intestine but was followed by a significant decrease in the number of large- and medium-size tumors. The animals which had received clofibrate beginning from 10 days before the first injection of DMH revealed a relatively greater fraction of exophytic intestinal tumors and less invasion of the intestinal wall as compared with the animals treated with DMH alone. Possible mechanisms of the effect of clofibrate are discussed.

Study of kinetics of epithelial cell populations in normal tissues of the rat's intestines and in carcinogenesis. III. Changes in kinetics of enterocyte populations in the course of experimental intestinal tumour induction in rats

A stage-by-stage study of disturbances in enterocyte proliferation in the ileum and descending colon in the course of tumour induction by treatment with 1,2-dimethylhydrazine was performed. Even at early stages, an expansion of the zone of epithelial cell proliferation in the crypts and migration of dividing cells as far as to the crypt mouth, which is a manifestation of enterocyte differentiation disturbances, were observed. Enterocytes of the crypts chiefly proliferated through a short cycle, the mean duration of which was slightly greater than in normal intestinal tissue. The reduced cell loss in the epithelium and resultant disturbances of its steady state led to the accumulation of great numbers of atypical cells in the superficial layers of the crypts and formation of carcinomas in situ in the descending colon. The microscopically unaltered sections of the mucosa, prior to development of overt neoplastic changes carcinomas in situ, superficial cancers and small-size adenocarcinomas revealed a simplified structure of enterocyte population, as compared with normal epithelium. As tumours progressed, the heterogeneity of its component cell subpopulations increased, and several subpopulations, differing in mean duration of the mitotic cycle, were formed. Pathologic mitoses made up a greater portion (50-60 per cent) of the dividing cells of the descending colon, as compared with ordinary 4 per cent at all stages of experimental tumour induction.

Study of kinetics of epithelial cell populations in normal tissues of the rat's intestines and in carcinogenesis. I. A comparison of enterocyte population kinetics in different segments of the small intestine and colon

The peculiarities of enterocyte proliferation in the duodenum, jejunum, ileum, caecum, ascending, transverse and descending colon in the rat were studied by different methods of analysis of cell population kinetics (percentage-labelled mitosis curves, cumulative labelling curves, distribution of labelling index curves, etc.). The majority of proliferating cells in the small intestine are homogenous, as far as mitotic cycle mean duration (11-12 hrs) is concerned. All proliferating cells in all the zones of the colonic crypts and the bottom of the small intestine crypts are divided into subpopulations, having different mean durations of the mitotic cycle. It is suggested that, in the crypt bottom in all intestines as well as the crypt's maximum proliferation zones in most of the colonic segments, a considerable fraction of cells has a very long mitotic cycle or enters resting phase R1. The average value of the mean durations of the mitotic cycle of all colonic enterocyte subpopulations is 18-22 hours. On the basis of the authors' findings and literature data, a model for the enterocyte life cycle is proposed, according to which the cell flux is branched during the mitotic cycle and the crypt develops from a stem enterocyte population located at its bottom.

Study of kinetics of epithelial cell populations in normal tissues of the rat's intestines and in carcinogenesis. II. Peculiarities of kinetics of enterocyte populations in experimental tumours of the colon

Cell proliferation in adenocarcinomas induced in the rat's colon by parenteral injection of 1,2-dimethylhydrazine was compared with that in normal colonic epithelium by means of autoradiographs. The distinct zone of proliferation, typical of the intestines, was not observed in the tumours, and cells replicated nearly in all segments of neoplasms. Tumour enterocytes were found to have a longer short mitotic cycle (16 instead of 11 hrs), due, chiefly, to an extension of G1-period duration. They were also characterized by a more pronounced heterogeneity as far as the values of ts and tG2 are concerned, and, probably, by the formation of an R2-population. Both the index of S-phase (29%) and labelled cell fraction (87%) after 6 injections of 3H-thymidine spaced at six-hour intervals, were lower in adenocarcinomas than in the zone of maximum proliferation in the descending colon (45 and 100%, respectively) and yet higher than the same parameters calculated for the whole population of the intestinal epithelium (17 and 60%, respectively). As far as proliferation parameters go, adenocarcinoma cells highly resemble those of the crypt bottom population in control animals, which was found to consist of several subpopulations with a varying mean duration of the mitotic cycle, and where stem enterocytes are likely to occur. When enterocytes become malignant, disturbances in their differentiation decrease cell shedding into the intestinal lumen and, thus, cause tumours to arise and develop.

Dependence of 1,2-dimethylhydrazine metabolism on its treatment schedule

The content of cytochromes P-450 and b5 in rat liver microsomes, as well as the extent of labeling of nucleic acids and proteins of the liver and kidneys and of mucosa from different intestinal segments, was studied in rats injected daily or once a week subcutaneously with similar total doses of 1,2-dimethyl-hydrazine (SDMH) and in untreated rats. Daily SDMH administrations led to a decrease in cytochrome P-450 activity. Pretreatment of rats with unlabelled SDMH resulted in decreased labeling of DNA, RNA, proteins, and acid-soluble fractions after [3H]SDMH injection. A more pronounced effect was found after the daily treatment.

Distribution and carcinogenic action of 1,2-dimethylhydrazine (SDMH) in rats

The radioactivity in the blood, bile, and contents from different parts of the gastro-intestinal tract was estimated for different time intervals up to 24 h after 3H-SDMH injection to rats. 65% of the radioactivity was excreted in the urine. Of the total quantity of radioactive products entering the intestine, 96% is brought with bile and only 4% from the circulation through the wall of the intestine. This latter small amount of SDMH metabolites plays a leading role in the genesis of intestinal tumours. This conclusion was proved by the observation that the intestinal tumours developed in different isolated segments of the gut where the entry of bile was excluded and by published data indicating that SDMH is excreted unchanged in the bile. It was shown that the carcinogenic effect depends upon the dose schedule of carcinogen treatment, probably, due to the changes in the SDMH metabolism. The optimal conditions for induction of intestinal tumours occur after administration of SDMH in a dose of 21 mg/kg body weight once a week. Hypothetic SDMH metabolic pathways leading to tumour production have been considered in the light of available experimental data.

Nucleic acids from subcellular fractions of N-nitrosodiethylamine-induced hepatoma in mice

During eight successive isologous passages of hepatoma induced in male C3HA mice by N-nitrosodiethylamine, no common features of tumor progression were observed, although both the mitotic pattern and ploidy differed from generation to generation. These additional cytologic criteria allowed the biochemical examination of material least changed due to tumor progression. Tumor nDNA's were characterized by greater actinomycin D (AD)- and acridine orange (AO)-binding abilities than were normal nDNA's; this could have resulted from a higher proportion of double-stranded regions in tumor DNA. Isolated tumor deoxyribonucleoprotein had both lower template activity in an RNA polymerase system and fewer AD- and AO-binding sites, when compared with the activity and sites from normal mouse liver. RNA-DNA hybridization data with the above-mentioned findings showed that in hepatoma, part of the nuclear genome was repressed. Also, RNA "new classes" appeared and a certain proportion of nuclear genes controlling mitochondrial protein biosynthesis were derepressed in tumor mitochondria. The hybridization of mitochondrial RNA (mtRNA) and DNA revealed new classes of pulse-labeled RNA's in in vitro-incubated liver mitochondria that were absent from intact cell organelles; the hybridization properties of in vivo- and in vitro-formed hepatoma mtRNA's were similar. Competition and hybridization experiments demonstrated that in tumor mitochondria in vivo, some new classes of RNA existed. Hepatoma mitochondrial mRNA had a higher metabolic stability than did normal mRNA.

The significance of nonspecific injury for colon carcinogenesis in rats

A purse-string suture was put into the rat's cecum to form a "diverticulum." When the thread cut this stitch, the resultant extensive necrotic zone healed for a long time. The presence of a foreign body (ligature) provided a permanent source of injury to the cecal mucosa. The lesions caused an increase in [3H]thymidine-labeled epithelial cells in the adjacent tissue detected by means of microautoradiographs. A postinjury injection of 1,2-dimethylhydrazine resulted in a marked increase in the rate of cecal tumor incidence (from 23 +/- 2.8% under ordinary conditions to 87 +/- 6% and 96 +/- 4% in different experimental series). The rise in tumor incidence following injury may be due to the entry of a greater number of stem cells into the mitotic cycle at which stage they seem to be responsive to carcinogenic influences.

Morphology and morphogenesis of experimental epithelial tumors of the intestine

In a morphogenetic study of experimental tumors of the intestine, 556 male noninbred albino rats were given weekly sc injections of 21 mg 1, 2-dimethylhydrazine dihydrochloride/kg body weight and were killed at different intervals (10-70 rats/wk) after the beginning of treatment. Intestinal carcinomas developed in almost all rats surviving 5 months after the beginning of the experiment. In addition, intestinal tumors induced in 800 rats of both sexes were examined. Tumor development began with a widening of the proliferative zone within the crypts, an indication of enterocyte differentiation disorders. The ensuing in situ carcinoma became superficial cancer capable of invading the lamina propria of the mucosa. Its continued growth caused the tumor to penetrate the tunica muscularis mucosae into the underlying layers of the intestinal wall. Thus experimental intestinal adenocarcinomas developed de novo or, at least, were not preceded by adenomatous polyps. Signet-ring cell carcinomas began with the accumulation of goblet cells in cells of signet-ring appearance; later they ruptured the basal membrane and infiltrated the surrounding tissues. The proposed scheme of morphogenesis of experimental tumors was correlated with current concepts of rectal tumor development in man.

The mechanism of carcinogenic action of 1,2-dimethylhydrazine (SDMH) in rats

The radioactivity level in blood, bile, urine and contents of parts of the gastro-intestinal tract in rats was studied after subcutaneous administration of 3-H-1,2-dimethylhydrazine (3-H-SDMH) which induces colonic tumours. The alkylation of DNA, RNA and protein in the intestinal mucosa, liver and kidneys was estimated 1 h to 28 days after 3-H-SDMH treatment from the 3-H-incorporation into these macromolecules. Administration of 3-H-1,2-diethylhydrazine (3-H-SDEH) which does not induce intestinal tumours was made as a control. Fifteen to 30 min after 3-H-SDMH treatment, marked radioactivity was found in blood, bile, urine and in contents of all regions of gastro-intestinal tract. After 3-H-SDMH administration no label occurred in the contents of localized segments of gastro-intestinal tract although it was present in blood, bile and urine. 3-H-SDMH methylated DNA, RNA and proteins of intestinal mucosa, liver and kidney to a high degree. One hour after 3-H-SDMH treatment the incorporation of label into protein of intestinal mucosa was higher than into liver and kidneys. 3-H-SDEH did not alkylate macromolecules in these organs but did so in thymus, spleen and brain, which are target organs for this carcinogen. After total hepatectomy, 3-H-SDMH did not methylate macromolecules of the intestinal mucosa. The following mechanism for the carcinogenic effect of SDMH is suggested. A carcinogenic metabolite of SDMH forms, in the liver, a conjugate with glucuronic acid. This glucuronide enters the gut both with bile and directly via the circulation. Microbial beta-glucuronidase releases the active metabolite which, in turn, alkylates tissue macromolecules.