Benzo[alpha]pyrene diol epoxide I binds to DNA at replication forks

The distribution of lesions in DNA caused by (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [alpha]pyrene (B[alpha]P diol epoxide-I) was studied in synchronized C3H/10T1/2 cells treated in S phase. Sites of carcinogen modification of DNA were identified by polyclonal rabbit antibodies elicited against DNA modified with B[alpha]P diol epoxide-I in vitro. This antigenic DNA contained trans-(7R)-N2-[10-(7 beta,8 alpha,9 alpha-trihydroxy-7,8,9,10-tetrahydrobenzo[alpha]pyrene)-yl]- deoxyguanosine; other adducts were not detected by liquid chromatography. In this study, DNA replication forks with antibodies bound to B[alpha]P diol epoxide-I adducts were detected by electron microscopy. The frequency of replication forks containing carcinogen adducts associated with the fork junction was found to be 8-fold higher than expected for an average distribution. The proportion of replication forks that were apparently blocked at the site of the DNA damage increased when replication was allowed to occur after carcinogen exposure. These results support the conclusions that the fork junction is particularly vulnerable to adduction by B[alpha]P diol epoxide-I and that B[alpha]P diol epoxide-I adducts block the displacement of replication forks during DNA synthesis in intact cells.

Timing of proto-oncogene replication: a possible determinant of early S phase sensitivity of C3H 10T1/2 cells to transformation by chemical carcinogens

The temporal order of replication of several genes was studied in 10T1/2 cells synchronized by release from confluence-induced arrest of proliferation followed by treatment with 2 micrograms/mL aphidicolin for 24 h. DNA subjected to bromodeoxyuridine substitution for 1- or 2-h intervals spanning the S phase was separated from the remaining DNA in cesium chloride gradients, filtered onto nitrocellulose in a slot-blot apparatus, and hybridized with various 32P-labeled probes. Ha-ras was among the first genes replicated at the onset of the S phase. The myc proto-oncogene replicated later but within the first hour of the S phase. The replication of Ki-ras, raf, and mos was detected between hour 1 and 2 of the S phase. The dihydrofolate reductase gene replicated early (0-2 h) and the myb proto-oncogene replicated in mid-S phase (2-4 h). An immunoglobulin VH sequence and the beta-globin gene replicated late in 10T1/2 cells, 4-6 h after removal of aphidicolin. Replicating DNA is preferentially adducted by chemical carcinogens, and replication of damaged proto-oncogenes before they are repaired may activate their transforming potential. Therefore, the observed replication of proto-oncogenes during the early S phase may underlie the enhanced sensitivity of 10T1/2 cells to chemically induced transformation at this point in the cell cycle.

The influence of exogenous estrogen use on survival after diagnosis of endometrial cancer

For examination of the effect of prior exogenous estrogen use on survival after diagnosis of endometrial cancer, 244 endometrial cancer cases newly diagnosed at North Carolina Memorial Hospital, Chapel Hill, North Carolina, between 1970 and 1976 were followed until 1982. Estrogen users (n = 46) were younger, had less advanced disease, and were more likely to be nonobese and white than were nonusers (n = 198). The estimated probability of surviving (Kaplan-Meier) five years after diagnosis was 0.89 for users and 0.53 for nonusers. When adjusted for age, grade, stage, obesity, race, and treatment (using the Cox proportional hazards regression model), the survival probabilities throughout the period of observation for estrogen users continued to be higher. The adjusted hazard rate for a nonuser was 2.05 (95% confidence interval (Cl) 0.96-4.39) times that for an estrogen user. The adjusted hazard rate from endometrial cancer only was 4.01 (95% Cl 1.22-13.21) times greater among estrogen nonusers. The more frequent occurrence of endometrial cancer in an earlier stage and grade among estrogen users may not be the sole cause of their lower hazard rate from this disease.

Specific nonsurgical therapy in male infertility

Although the objective of this article was to discuss the specific medically treatable causes of male infertility, the reader will be impressed by the fact that many of the treatments seem less than "specific." The need to treat infections to improve fertility is ill defined. The utilization of a scrotal cooling device as "specific" nonsurgical treatment for varicocele is yet to be defined. Immunologic suppression is indeed a specific form of therapy for a measurable phenomenon; unfortunately, the significance of that phenomenon as well as the best means and location of its assessment are undergoing significant reevaluation. An exciting frontier is the prospect of preventing infertility in the patient undergoing therapy for cancer, thus obviating the need for treatment of the ensuing infertility. Before specific therapies can be anticipated to have a predictable beneficial effect, these areas require active investigation to define the problem more clearly.

Aspiration flow cytometry of the testes in the evaluation of spermatogenesis in the infertile male

Deoxyribonucleic acid (DNA) flow cytometry of testicular tissue has been demonstrated to be a quantitative means of assessing spermatogenesis. This study evaluates testes aspirates and DNA flow cytometry in the evaluation of the infertile male. Testicular tissue obtained from 12 men who underwent bilateral orchiectomy for prostate cancer (group 1) were examined by both flow cytometry and standard histologic technique to assess the correlation between these two modalities. Thirteen men evaluated for infertility (group 2) and requiring histologic evaluation of spermatogenesis underwent both open biopsy and fine needle aspiration of their testes. Histology was independently examined and grouped according to standard nomenclature. Flow cytometric analysis revealed characteristic patterns in the relative numbers of haploid (1C), diploid (2C), and tetraploid (4C) cells. These patterns correlated reproducibly with the histologic diagnoses. DNA flow cytometry of testicular aspirates provides a rapid and reliable quantitative means of assessing spermatogenesis.

Cell cycle-dependent initiation of hepatocarcinogenesis in rats by (+/-)-7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo(a)py rene

Male F344 rats were treated once with (+/-)-7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo(a)pyre ne (BPDE) at various times after a two-thirds partial hepatectomy. Diet containing 0.05% phenobarbital was fed subsequently to promote the development of hepatocellular neoplasms from initiated cells. This combined treatment caused an apparently continuous emergence of hepatocellular neoplasms between 31 and 60 weeks after initiation. Yields of hepatocellular neoplasms (adenomas and carcinomas) seen at 45 weeks after initiation varied according to the time of treatment with BPDE. Rats treated at 15 h after partial hepatectomy, when maximal fractions of proliferating hepatocytes were entering the S phase, displayed the greatest incidence and yield of hepatocellular neoplasms. Rats treated when hepatocytes were early in the prereplicative G1 phase demonstrated a significantly lower incidence and yield of hepatocellular neoplasms. No neoplasms were seen in livers of rats treated with BPDE without prior partial hepatectomy; this indicates the insensitivity or resistance of nonproliferating G0 hepatocytes to initiation by this chemical. The variation in yields of neoplasms could not be attributed to variation in binding of carcinogen to DNA or to rates of DNA repair. The risk of initiation of hepatocytes appeared to be correlated (r = 0.95) with the fraction of hepatocytes that were entering the S phase at the time of treatment with BPDE. These results reveal a significant cell cycle dependency for initiation of hepatocarcinogenesis by BPDE and show that proliferating hepatocytes are at greatest risk when early in the S phase. Quantitation of islands of hepatocellular alteration suggested a similar pattern of cell cycle-dependent sensitivity, although the cycle-dependent variation in island frequencies (1.4-fold) was less than the variation in yields of neoplasms (5-fold). However, 1300-5000 islands were estimated to appear for every one neoplasm that appeared. When viewed within the context of multistep carcinogenesis, and assuming that islands of altered hepatocytes represent a step in this process, then these results suggest that islands may represent populations of cells at least one step removed from neoplasia.

Benign scrotal tumors masquerading as expanding varicoceles

Vascular lesions of the scrotum though most often varicoceles, can occasionally represent either benign or malignant tumors containing vascular elements. Two pediatric patients presenting with vascular scrotal masses resembling varicoceles are reported. Histologic interpretation of the operative specimens demonstrated benign tumors of the scrotum. Hemangiomas, hamartomas, or mesenchymal tumors should be especially suspect in the presence of any vascular right scrotal lesion. Because of the infrequency of prepubertal varicoceles, any vascular lesion of the scrotum in this age group should undergo biopsy before simple excision is performed to rule out the presence of malignancy. Early excision of benign mesenchymal tumors is especially important if, as some believe, they eventually dedifferentiate to more malignant tumors later in the lifetime of an individual.

Flow cytometric analysis of human uterine sarcomas and cell lines

Flow cytometric techniques were used to characterize multiple human uterine sarcomas and cell lines derived from some of these tumors. Analysis of DNA content showed that 9 of the 11 uterine sarcomas investigated were composed of at least one aneuploid population as well as a distinct diploid population. These data indicate that aneuploidy, as measured by flow cytometry, is a characteristic more common to uterine sarcomas than that previously reported for uterine adenocarcinomas. Unlike the original tumors, the cell lines established from three of the sarcomas contained predominantly diploid populations with only minor aneuploid populations. Treatment of one of the sarcoma cultures with tumor promoters did not result in an increase in the aneuploid populations. Tumors which arose in nude mice upon transplantation of two of the sarcomas did not contain the same distribution of tumor subpopulations as found in the original sarcomas. Apparently, the in vitro culture and and in vivo nude mouse conditions were not appropriate for maintaining the original equilibrium between the aneuploid and diploid subpopulations but instead provided a selective environment that resulted in the preferential growth of only certain tumor populations. Dual-parameter analysis of DNA content and alkaline phosphatase levels of one of the sarcomas were useful for distinguishing the aneuploid from the diploid population coexisting in this tumor. Our data suggest that flow cytometry is a valuable tool to analyze the characteristics of the tumor populations residing in primary uterine sarcomas as well as to determine which of these tumor subpopulations survive in culture and transplantation to nude mice.

Cell cycle-dependent initiation of hepatocarcinogenesis in rats by methyl(acetoxymethyl)nitrosamine

Hepatocyte sensitivity to initiation of carcinogenesis was studied as a function of the cell cycle phase in which damage was incurred. Hepatocytes were stimulated to proliferate by a two-thirds partial hepatic resection, and their proliferation was synchronized further by postsurgical treatment with hydrocortisone. Groups of male F344 rats were given a single administration of methyl(acetoxymethyl)nitrosamine, a highly reactive methylating agent, at various times after two-thirds partial hepatic resection when hepatocytes were in defined phases of the cell cycle. Beginning 3 wk after the treatment and for 37 wk thereafter, rats were fed a diet containing 0.05% phenobarbital to promote the expression of initiated hepatocytes. At 45 wk after treatment with carcinogen hepatocytic neoplasms were enumerated. The greatest yield of neoplasms (5.4 per liver) was observed in the group treated 16 h after two-thirds partial hepatic resection or at the time when proliferating hepatocytes began to enter the S phase of the cell cycle. The least yield of neoplasms (0.8 per liver) was identified in the group treated with methyl(acetoxymethyl)nitrosamine when hepatocytes were early in G1. In the proliferating hepatocytes sensitivity rose continuously during G1 to a peak at the G1-S border and then fell continuously as hepatocytes traversed S, G2, and M. This pattern of response could not be attributed to variation in hepatic esterase which activates methyl(acetoxymethyl)nitrosamine or to variation in methylation of DNA. The results support a model in which carcinogen-induced genetic alterations, occurring at the time of or soon after damaged cells enter the S phase, represent irreversible events that contribute to the initiation of carcinogenesis.

Factors influencing the initiation by gamma rays of hepatocarcinogenesis in the rat

F344 male rats were irradiated once with 6 G of cesium 137 gamma rays at various times after a two-thirds partial hepatectomy (PH) and then fed a diet containing the liver tumor promoter phenobarbital to evoke the expression of initiated hepatocytes. Yields of hepatocellular neoplasms were enumerated at 45 weeks after irradiation. Although proliferating hepatocytes in regenerating livers appeared to have increased risk of initiation by gamma rays, there was no apparent variation in risk among groups that were treated at times when hepatocytes were in different portions of the cell cycle (G1, S, G2/M). Gamma irradiation delayed the onsets of DNA synthesis and mitosis by proliferating hepatocytes by 18-20 h. The rate of rejoining of radiation-induced DNA strand breaks was analyzed in primary cultures of hepatocytes; 98% of the strand breaks were rejoined within 30 min after irradiation. Efficient repair of certain types of radiation-induced damage to DNA before the damaged DNA is replicated should cause a substantial reduction in the probability of induction of base-substitution mutations. Hepatocellular islands and neoplasms that were initiated by gamma rays may be derived from proliferating hepatocytes which incurred other radiation-induced DNA damages such as chromosomal aberrations.

Cystic fibrosis presenting in a 45-year-old man with infertility

Cystic fibrosis commonly is regarded as a disease of childhood associated with severe pulmonary and pancreatic pathological conditions. We report on a previously healthy 45-year-old man who was diagnosed as having cystic fibrosis after presentation with primary azoospermia. The literature is reviewed. Although references are made to late presentations of cystic fibrosis none was found in which the initial complaint was infertility. Primary azoospermia may be the presenting manifestation of cystic fibrosis in the absence of major respiratory symptoms.

Species differences in the formation of benzo(a)pyrene-DNA adducts in rodent and human endometrium

The formation of adducts of benzo(a)pyrene metabolites on DNA was investigated in endometrial tissue from humans, hamsters, mice, and rats. anti-Benzo(a)pyrene-7,8-diol-9,10-epoxide was the predominant adduct identified in all the species studied. The amount of (+)-anti-benzo(a)pyrene-7,8-diol-9,10-epoxide bound to DNA from human endometrium was approximately 3 times higher than to DNA from hamster tissue. Among the three animal species examined, the level of this adduct was highest in hamsters and lowest in rats. The high pressure liquid chromatography profiles of adducts formed in endometrium from humans and hamsters were similar, but the specific activity (pmol/mg DNA) of each adduct formed was different. syn-7,8-Dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene adduct was present in humans, hamsters, and rats but was not detected in mouse endometrium. There was an unidentified adduct present only in rat tissue. Rats had the lowest level of total DNA-bound radioactivity and the largest percentage of this total eluted as an uncharacterized radioactive peak that eluted with water (53%). These results demonstrate that endometrial tissues from humans and three rodent species differ with regard to the quantities and proportions of benzo(a)pyrene-DNA adducts formed from benzo(a)pyrene.

Endometrial stromal cells in culture: an attempt to understand the genesis and biologic activity of uterine sarcomas

The genesis of uterine sarcomas in vivo has been difficult to elucidate. The reasons are multifactorial and are compounded by the rarity of these tumors. In an effort to understand the biologic activity of this disease, normal endometrial tissue was subjected to tissue culture, histochemical study, and hormonal manipulation. Protein markers were used to differentiate endometrial epithelium from endometrial stromal cells in culture. The endometrial stromal cells grew rapidly following subculturing and were responsive to hormonal manipulation. When the stromal cells in culture were treated with the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the resultant morphologic changes mimicked uterine sarcomas grown in culture. These changes appeared to occur in a sequential manner, somewhat analogous to changes occurring in the endometrial epithelium as it undergoes transformation to endometrial adenocarcinoma. These studies, therefore, may serve as a model system in understanding the genesis and biologic activity of uterine sarcomas.

Quantitative relationship between initiation of hepatocarcinogenesis and induction of altered cell islands

We have quantified the initiation of hepatocytic neoplasms and the induction of altered cell islands in regenerating livers of rats given a single treatment with one of three carcinogens before or during the peak of DNA synthesis after partial hepatectomy. For up to 20 wk after treating livers during the peak of DNA synthesis with methyl(acetoxymethyl)nitrosamine (DMN-Ac), hepatocytic neoplasms were not seen. Thereafter, in rats fed the liver tumor promoter, phenobarbital, neoplasms emerged continuously so that by 60 wk after initiation, livers held an average of 5.5 neoplasms. Islands of cellular alteration, identified by their abnormal retention of glycogen on fasting, also appeared to emerge continuously between 20 and 60 wk after initiation. By 60 wk, promoted livers contained about 10,000 islands. In DMN-Ac-initiated, phenobarbital-promoted livers, neoplasms and islands maintained a constant numerical relationship over time with about 1,450 islands emerging for every neoplasm that emerged. This ratio of islands to neoplasms differed according to the type of carcinogen used to initiate hepatocarcinogenesis and depending on whether promotion with phenobarbital was included. In livers initiated with DMN-Ac but not promoted with phenobarbital, the ratio of islands to neoplasms was about 7,750:1. In livers initiated by treatment with (+/-)-7 alpha, 8 beta-dihydroxy-9 beta, 10 beta-epoxy-7,8,9, 10-tetrahydrobenzo[alpha]pyrene at the peak of DNA synthesis and then promoted with phenobarbital, the ratio of islands to neoplasms was 7,200:1. In livers exposed to gamma rays at the peak of DNA synthesis in regenerating livers and promoted, no neoplasms were seen in our sample although islands could be enumerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of DNA replication in C3H 10T1/2 cells synchronized by aphidicolin

Aphidicolin is an inhibitor of DNA polymerase alpha and blocks nuclear DNA replication without interfering with mitochondrial DNA synthesis. The efficacy of this mycotoxin as a tool in cell synchronization was evaluated in C3H 10T1/2 clone 8 cells. At concentrations of 1-2 micrograms/mL, aphidicolin quickly reduced the [3H]thymidine uptake to less than 5% of control levels in the first 5 min of incubation. This inhibition was easily reversed by washing and refeeding cells with fresh medium. The synchronization protocol consisted of first blocking cells by confluence arrest, replating them at lower density, and then treating the cells with aphidicolin for 24 h. Once the inhibitor was removed, DNA replication started without any delay. The cell population traversed the S phase in about 8 h and synchronously doubled in cell number. Autoradiography studies revealed a labeling index of 89-93% during the S phase. However, it was also observed that 10T1/2 cells were able to enter S phase in the presence of aphidicolin. The extent of the ensuing replication in the nucleus was dependent on the time that cells remained arrested in early S phase. Analyses of the newly replicated DNA in alkaline sucrose gradients revealed a fairly homogeneous distribution of sizes of nascent DNA in synchronized cells pulse-labeled at the beginning of the S phase. Upon chase in nonradioactive medium, the average molecular weight of the nascent DNA increased linearly with time of DNA synthesis for 2 h. The apparent rate of DNA chain growth determined from pulse and chase experiments was 1.2 micron/min. This rate was strongly inhibited (93%) by aphidicolin at a concentration of 2 micrograms/mL.

Quantitative relationship between hepatocytic neoplasms and islands of cellular alteration during hepatocarcinogenesis in the male F344 rat

Hepatocytic neoplasms (nodules and carcinomas) and islands of cellular alteration which display abnormal retention of glycogen on fasting were quantified in F344 male rats at intervals after initiation of hepatocarcinogenesis by the combination of a two-thirds partial hepatectomy with a single treatment with methyl(acetoxymethyl)-nitrosamine during the subsequent peak of DNA synthesis in regenerating livers. In initiated rats fed the liver tumor promoter phenobarbital, yields of neoplasms and islands maintained a constant numerical relationship over time, with one neoplasm emerging for every 1600 islands. Significantly fewer neoplasms developed in rats not fed the phenobarbital, although the numbers of islands observed at 45 and 60 weeks after initiation were not significantly increased by the promoter. The ratio of islands to neoplasms in rats not fed the phenobarbital was about 11,000:1. Dietary phenobarbital appeared to have an effect on initiated hepatocytes (or latent neoplasms) that was not revealed by its effects on the growth and size of the island population.

Quantitation by electron microscopy of the binding of highly specific antibodies to benzo[a]pyrene-DNA adducts

Highly specific antibodies bound to carcinogen adducts in DNA modified with (+/-)7 beta,8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE I) were quantitated by electron microscopy (EM) visualization and these observations were compared with quantitation of adducts by enzyme-linked immunosorbent assay (ELISA). The antiserum, elicited in rabbits following inoculation with BPDE I-modified DNA, has been found to be highly specific in its recognition of BPDE I-deoxyguanosine moieties. Parallel DNA samples prepared for analysis by ELISA and EM quantitation were randomized, encoded, and analyzed to determine extents of carcinogen modification in double-blind studies. After levels of modification were determined by immunoassays, DNA samples were prepared for EM analysis by incubation with amounts of anti-BPdG-DNA serum in excess of that necessary for complete binding of antibody to antigenic sites. At equilibrium, samples were enzymatically digested with papain in order to cleave anti-BPdG-DNA IgG molecules into Fab fragments in situ. Following column exclusion chromatography, BPdG-DNA-Fab complexes were incubated with ferritin-labeled Fab' fragments of goat [anti-rabbit F(ab')2] IgG in amounts in excess of those necessary for complete binding. When DNA samples were modified to between 0 and 40 fmol adduct/micrograms DNA, excellent agreement was obtained between ELISA quantitation and visualization by EM of antibodies bound to adducts.

Analysis of isoenzymes in normal and carcinogen-treated human endometrial stromal cells in culture

The isoenzyme patterns of lactate dehydrogenase (LDH), hexokinase, phosphofructokinase, and aldolase were investigated in cultured normal and carcinogen-treated human endometrial stromal cells. Both normal and carcinogen-treated cells had similar phosphofructokinase and aldolase isoenzymes. Distinctive changes in hexokinase and LDH isoenzyme patterns were found in the carcinogen-treated stromal cells. The LDH isoenzyme patterns of the carcinogen-treated stromal cells were shifted toward the muscle LDH forms. This is comparable to the alteration of LDH isoenzyme profiles observed in cell lines established from human uterine sarcomas. The two tissue culture media used affected the LDH isoenzyme patterns of endometrial stromal cells but differences between the LDH isoenzyme patterns of control and carcinogen-treated cells were detected regardless of the growth medium used. Total LDH activity was not significantly different in control and carcinogen-treated stromal cells. The hexokinase isoenzyme patterns expressed by the carcinogen-treated stromal cells were distinctly different from the normal hexokinase patterns. The treated stromal cells contained both hexokinase I and II, whereas the normal cells contained only hexokinase I. Hexokinase and LDH isoenzyme patterns may serve as markers with which to evaluate carcinogen-induced neoplastic changes in cultured endometrial stromal cells.

The heterogeneity of LDH isoenzyme patterns of human uterine sarcomas and cultured sarcoma cell lines

Both the tissue lactate dehydrogenase (LDH) isoenzyme pattern and total LDH activity were investigated in a series of human uterine sarcomas and cell lines derived from these tumors. Abnormal LDH isoenzyme patterns characterized by shifts toward the muscle isoenzyme forms (LDH4 and 5) were found in some, but not all, of the sarcomas. The tumors containing rhabdomyosarcomatous elements usually had normal or only slightly altered LDH isoenzyme patterns. The LDH isoenzyme patterns expressed by cultured cell lines established from the uterine sarcomas, in general, resembled those found in the primary tumors. These results suggest that the normal or near normal LDH isoenzyme distributions found in uterine sarcomas with rhabdomyosarcomatous differentiation may be a potential characteristic which may be used for distinguishing these tumors from other uterine sarcomas.

Biochemical studies of the tracheobronchial epithelium

Tracheobronchial epithelium has been a focus of intense investigation in the field of chemical carcinogenesis. We have reviewed some biochemical investigations that have evolved through linkage with carcinogenesis research. These areas of investigation have included kinetics of carcinogen metabolism, identification of carcinogen metabolites, levels of carcinogen binding to DNA, and analysis of carcinogen-DNA adducts. Such studies appear to have provided a reasonable explanation for the susceptibilities of the respiratory tracts of rats and hamsters to carcinogenesis by benzo(a)pyrene. Coinciding with the attempts to understand the initiation of carcinogenesis in the respiratory tract has also been a major thrust aimed at effecting its prevention both in humans and in animal models for human bronchogenic carcinoma. These studies have concerned the effects of derivatives of vitamin A (retinoids) and their influence on normal cell biology and biochemistry of this tissue. Recent investigations have included the effects of retinoid deficiency on the synthesis of RNA and the identification of RNA species associated with this biological state, and also have included the effects of retinoids on the synthesis of mucus-related glycoproteins. Tracheal organ cultures from retinoid-deficient hamsters have been used successfully to indicate the potency of synthetic retinoids by monitoring the reversal of squamous metaplasia. Techniques applied to this tissue have also served to elucidate features of the metabolism of retinoic acid using high pressure liquid chromatography. In brief, formidable strides have been made in biochemistry specific to this important target tissue, despite the inability to acquire tracheobronchial epithelium in large quantities.

Promotional effect of diethylstilbestrol on human endometrial stromal cells pretreated with a direct-acting carcinogen

Chronic treatment with 0.1 microM diethylstilbestrol (DES) increased the expression of phenotypic alterations in human endometrial stromal cells pretreated with the direct-acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Abnormal morphology, expression of gamma-glutamyltranspeptidase, and the ability to form colonies under restrictive conditions were more pronounced after combined treatment with carcinogen and DES compared to carcinogen or DES alone. This effect did not appear to be due simply to growth enhancement by DES, because acute treatment with DES did not alter colony formation, growth rate or thymidine incorporation into DNA in stromal cell cultures. Neither did the presence of DES after the toxicity of MNNG. DES did cause shifts in the isoenzyme distribution of lactate dehydrogenase which could be indicative of a hormonal response. The results suggest that DES may act as a tumor promoter or cocarcinogen in human cells through a mechanism other than simply stimulating cell proliferation, but that other estrogenic effects may contribute to the promotional process.

Histochemical identification of cultured cells from human endometrium

Histochemical techniques have been applied to the identification of cell types cultured from human endometrium. Previous work from this laboratory characterized two principal cell types found in cultures of endometrium: a mature epithelial cell and another cell which was classified as the endometrial stromal cell based on light and electron microscopy. In this report we compare the histochemical staining of endometrial tissue in frozen sections to that of cultured cells. These results confirm the epithelial and stromal nature of the respective cell types. Several markers were found that could distinguish between cells of epithelial and stromal origin. The enzymes alkaline phosphatase, gamma-glutamyltranspeptidase, peroxidase, and beta-glucuronidase were localized in glandular and surface epithelia in frozen sections and in colonies of epithelial cells in culture. Stroma in frozen sections and cultured stromal cells contained leucine aminopeptidase and fibronectin. Epithelia in sections and in culture could also be distinguished from cells of stromal origin by preferential binding of lotus and peanut lectin. Several other markers were found in both endometrial epithelium and stroma.

Enhancement by TPA of phenotypes associated with transformation in carcinogen-treated human cells: evidence for a selective mechanism

The tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) was found to increase the incidence of phenotypic alterations induced by the direct-acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in human endometrial stromal cells. Following carcinogen treatment, changes in saturation density, gamma-glutamyltranspeptidase expression, morphology, and growth in selective media were enhanced in cell cultures subjected to continuous TPA exposure as compared to cultures receiving ethanol vehicle. This enhancement may have resulted, at least in part, from selection of cells altered by carcinogen, as evidenced by differences in the colony-forming abilities of MNNG-treated and control cultures after prolonged TPA exposure, and by differences in morphologic response to TPA challenge in these two populations.

Fractionation and characterization of DNA at sites of replication from rat liver nuclei

Regenerating rat liver nuclei when sonicated and centrifuged in a Cs2SO4 gradient were fractionated into three distinct bands. These bands were designated as light band (LB), middle band (MB), and heavy band (HB) according to their density. LB and MB were shown to consist of large granular particles with varying electron densities, but LB also contained remnants of nuclear membrane. When analysed by gel electrophoresis, LB and MB displayed more than 35 bands of proteins. The third fraction, HB, consisted largely of small chromatin fibers and its proteins were predominantly the four histones of the nucleosomal core particle. Following short pulses with [3H]thymidine in vivo, the specific activity of DNA in LB and MB was significantly higher than that of bulk DNA contained in HB. DNA in all three fractions became equally labelled as the duration of the labelling interval increased beyond 30 min. Newly synthesized DNA was characterized by electrophoresis on analytical 1.7% acrylamide -0.5% agarose composite gels. After a 1-min labelling interval in vivo, 17% of the rapidly labelled DNA from LB and MB was stationary at the gel origin like replication forks from E. coli, but only 3% of HB DNA had zero mobility. Electron microscopy confirmed the presence of DNA replication forks in LB, MB, and HB. With increasing time of synthesis the proportion of labelled DNA exhibiting zero mobility decreased in all three fractions. Denaturation of DNA or digestion of single-stranded DNA with S1 nuclease released newly synthesized DNA from the gel origin. Ribonuclease was without effect. DNA recovered from LB and MB also had a higher molecular weight than the HB DNA. Together these results indicate (1) that LB and MB are enriched in newly replicated DNA; (2) that an increased proportion of newly replicated DNA in LB and MB is associated with DNA replication forks; and (3) that the replicating DNA recovered in LB and MB may be associated with other nuclear constituents in situ because this DNA appears to be protected from the more frequent chain breaks introduced into the bulk of chromatin (HB) by sonication.

Alterations of human endometrial stromal cells produced by N-methyl-N'-nitro-N-nitrosoguanidine

Stromal cell cultures obtained from human endometrium were treated repetitively with N-methyl-N'-nitro-N-nitrosoguanidine in vitro at concentrations ranging from 0.5 to 4.0 micrograms/ml, and alterations in growth potential and morphology were analyzed. A single exposure to the carcinogen resulted in morphological evidence of toxicity and reductions in growth rates, plating efficiency, and saturation density as compared to solvent-treated control cells. Cytotoxicity was reduced after additional exposures to the carcinogen. Following repetitive treatments with N-methyl-N'-nitro-N-nitrosoguanidine, human endometrial stromal cells developed enhanced growth potential, the capacity to form macroscopic colonies in soft agar, and elevated gamma-glutamyltranspeptidase activity. Carcinogen-treated cells displayed atypical morphology characterized by irregularities in cell and nuclear size and shape, large bizarre nucleoli, increased nuclear:cytoplasmic ratios, and cellular crowding. Control cells did not display altered morphology or growth parameters even following multiple exposures to solvent and repetitive subculturing. These alterations in growth potential and morphology suggest that the cells are progressing towards preneoplastic and perhaps neoplastic transformation in vitro.