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PubMed1998

Immunophenotype, proliferation, DNA ploidy, and biological behavior of gastrointestinal stromal tumors: a multivariate clinicopathologic study.

To determine the prognostic impact of clinical, immunohistochemical, and biological parameters, we examined 52 gastrointestinal stromal tumors (GIST) by conventional light microscopy and immunohistochemistry. DNA ploidy was analyzed by image cytometry on cytospin preparation. The proliferative activity was determined by mitosis counting and assessment of Ki-67 reactivity by means of monoclonal antibody Ki-S5. A histopathologic grade was assigned to each tumor according to the French Federation of Cancer Centers (FNCLCC) grading system. Next to vimentin, CD34 was the most prevalent antigen, followed by markers of neural and muscular differentiation. Many tumors exhibited a mixed phenotype. Twenty-one tumors were diploid, eight hypodiploid, and 23 aneuploid. In univariate analysis, tumor grade, Ki-S5 labeling index, mitotic count, atypical mitoses, cellularity, and sex were predictive of both mortality and metastasis risk. DNA ploidy only correlated with overall survival, whereas the tumor location affected the occurrence of metastases. Multivariate analysis selected Ki-S5 scores (P < .0001) and atypical mitoses (P=.012) as independent prognosticators for overall survival, and tumor grade (P=.0036) and size (P=.0055) as predictors of metastatic spread. We conclude that GIST are primitive mesenchymal tumors capable of divergent differentiation, which does not influence their prognosis. The latter appears to be best predicted by histopathologic grading and the Ki-67 labeling index.

Adult↗
PubMed1998

Spindle cell squamous carcinoma of the esophagus: analysis of ploidy and tumor proliferative activity in a series of 13 cases.

Spindle cell squamous esophageal carcinomas are distinctive polypoid "biphasic" tumors in which the sarcoma-like phenotype usually predominates over the epithelial component. To biologically assess both phenotypes, we compared the tumoral proliferative activity and DNA ploidy between the two histological components of 13 polypoid spindle cell squamous carcinomas of the esophagus. We studied the tumoral proliferative index (TPI) using MIB 1 monoclonal antibody (Ki-67) and determined the DNA histogram by image cytometry on Feulgen-stained sections. The DNA histograms were classified into four types (I to IV) according to the degree of dispersion of the DNA. The TPI of the carcinomatous regions ranged from 0.20 to 0.63 (mean, 0.44) and from 0.55 to 0.85 for the sarcoma-like areas (mean, 0.68) P < .0001. In all cases, the sarcoma-like areas were aneuploid, and 37.5% of the carcinomatous regions were diploid. Also, in all instances the carcinomatous areas were of either histogram type I or II, and the sarcoma-like areas showed histograms of type II or III. We conclude that in esophageal spindle cell squamous carcinomas the sarcoma-like phenotype differs biologically in two ways from the carcinomatous: (1) it has a higher TPI and (2) it has higher aneuploidy with a greater dispersion of the DNA content. We postulate that these characteristics could give a "growth" advantage to the sarcoma-like component of these tumors and explain its predominance over the carcinomatous component.

Aged↗
PubMed1996

p53 expression, proliferation marker Ki-S5, DNA content and serum PSA: possible biopotential markers in human prostatic cancer.

OBJECTIVES: The biology of prostate cancer is poorly understood. Despite established prognostic criteria, a confident prediction of the clinical outcome is not always possible. Therefore, additional and more precise information is highly desirable. In the present study, we compared potential biologic markers with the laboratory, clinical, and histopathologic parameters of prostate-specific antigen (PSA) level, tumor stage, and tumor grade. METHODS: Paraffin-embedded material from 62 radical prostatectomies for prostate carcinoma was examined immunohistochemically using monoclonal antibody Ki-S5 to determine the tumor growth fraction and antibody DO-1 to assess p53 protein overexpression. Deoxyribonucleic acid-ploidy was analyzed by flow and image cytometry. Preoperative PSA levels were assessed by standard method. The tumors were categorized according to the Gleason grading system and staged postsurgery after the TNM classification. RESULTS: The p53 expression, proliferation rate (Ki-S5), and rate of aneuploidy correlated closely with stage (P < 0.05) and Gleason score (P < 0.01). However, divergences were occasionally observed. The ploidy status correlated closely with proliferative activity and p53 expression. Conversely, no correlation was seen between these parameters and serum PSA content, the latter being significantly associated with the tumor stage alone. CONCLUSIONS: The results characterize proliferation marker Ki-S5, p53 expression, and ploidy status as tumor biopotential markers, whereas PSA provides diagnostic information. Use of these investigative methods promises to provide additional information relevant in prognosis and therapy selection. Nonetheless, their precise prognostic value will have to be established in further studies.

Aged↗
PubMed1997

A DNA cytometric proliferation index improves the value of the DNA ploidy pattern as a prognosticating tool in patients with carcinoma of the prostate.

OBJECTIVES: A still controversial issue is whether the results of a cytometric assessment of the DNA distribution pattern of the nuclei of the neoplastic parenchymal cells of a prostatic adenocarcinoma has additional prognostic value to that of the stage and grade of the disease. To increase the accuracy of the DNA ploidy assessments. Image cytometry (ICM) has been used and combined with the determination of an ICM proliferation index (PI) to increase its value as an additional prognosticating tool. METHODS: We investigated 96 patients, followed up since diagnosis in 1980/1981 until death or, in 11 surviving patients, for an average of 14.5 years. Survival analysis was made by the conventional Kaplan-Meier method. Fine-needle aspiration biopsy was used as the major diagnostic tool. The neoplastic cell nuclei were classified as ICM DNA diploid, tetraploid, or aneuploid by means of the ploidy-establishing peak in the ICM DNA histograms, as well as the fraction of tumor cells in the S-phase. Scattered cells to the right of the ploidy-establishing peak, the S-phase fraction, and those in the G2M area of the ICM DNA histograms were counted as percent of the total number of tumor cells; this percentage was defined as the PI. Arbitrarily, tumors with a PI less than 5% were classified as having a low proliferation rate, those with a PI greater than 10% were considered highly proliferating, and those with a PI between 5% and 10% as carcinomas with an intermediate proliferation potency. RESULTS: By univariate analyses, clinical stage, cytodiagnostic grade, cytometric DNA ploidy pattern and PI all had significant prognostic value. By multivariate analyses, the PI was found to add prognostic information to that of the ICM DNA ploidy pattern variable, giving it an increase in its statistical P value from 0.002 to 0.0005. As a consequence, the combination of these two variables was found to give rise to three new patient groups with regards to their prognosis: DNA group I had tumors with a diploid ICM DNA pattern with a low PI; DNA group II had tumors with a diploid or tetraploid ICM DNA tumor cell nuclei pattern with an intermediate PI; and DNA group III had a diploid or tetraploid ICM DNA pattern with high PI and all tumors with an aneuploid pattern. By multivariate analysis, including tumor grade and clinical stage, these new DNA groups (P = 0.0004) and M stage disease (P = 0.0006) were the only significant prognostic variables. CONCLUSIONS: A DNA cytometric PI improves the prognosticating value of DNA ploidy. Patients with prostatic adenocarcinomas, classified as DNA group I, have a low risk of death from their neoplastic disease with deferred or hormonal treatment only.

Adenocarcinoma↗
PubMed2004

A recurrent gain of chromosome arm 3q in primary squamous carcinoma of the vagina.

Primary carcinomas of the vagina are rare tumors, accounting for 2%-3% of all gynecologic malignancies. Only a few karyotypes based on chromosome banding techniques have been reported. We have, therefore, used comparative genomic hybridization to establish a pattern of genomic imbalances in vaginal squamous cell carcinomas. Analysis of 16 formalin-fixed and paraffin-embedded tumors revealed that 70% of vaginal carcinomas carry relative copy number increases that map to chromosome arm 3q. Other recurring gains were observed on chromosome arms 5p and 19p. Chromosomal losses were infrequent. Most tumors were aneuploid, as measured by image cytometry on Feulgen-stained tissue sections. The cytogenetic data were related to the presence of human papillomavirus genomes, expression of laminin-5 as a marker for invasiveness, and expression levels of markers for proliferative activity and mutated TP53. All relevant clinical data were recorded. The results suggest that vaginal carcinomas are defined by a specific distribution of chromosomal aneuploidies and that the pattern of genomic imbalances is strikingly similar to that observed in squamous cell carcinomas of the uterine cervix. Age at diagnosis (P=0.031), tumor size (P=0.025), and increased laminin-5 expression (P=0.006) have a significant influence on the survival time.

Aged↗
PubMed2004

Effects of low energy protons on clonogenic survival, DSB repair and cell cycle in human glioblastoma cells and B14 fibroblasts.

BACKGROUND AND PURPOSE: The reaction of human tumor cells and mammalian normal tissue to irradiation with low energy protons and X-rays was examined. MATERIAL AND METHODS: An irradiation facility with a vertical proton beam was set up at the Tandem accelerator at the University of Erlangen. U-138MG human glioblastoma cells and B14 hamster fibroblasts were irradiated with 5.7 and 7.0 MeV protons (LET 7.27 and 6.23 keV/microm) and with 120 kV X-rays. The inactivation was measured by the colony forming assay, induction and repair of DNA double strand breaks (DSB) by constant field gel electrophoresis and cell cycle control by image cytometry. RESULTS: An obvious reduction of the shoulder of the dose effect curve was determined. This effect was more pronounced for the glioblastoma cell line. The RBE at 10% survival was measured as 1.78 +/- 0.09 for glioblastoma cells and 1.18 +/- 0.06 for B14 fibroblasts. The induction of DNA DSB in glioblastoma cells showed an RBE of 0.96 +/- 0.06, after 24h repair time an RBE of 2.63 +/- 0.07 was calculated. Protons had a larger and enduring effect on G2 arrest of cell cycle than X-rays, 72 hours after irradiation with 10 Gy an RBE of 1.57 +/- 0.05 was calculated. CONCLUSIONS: The effect of higher LET irradiation was more distinct for tumor cells than for normal tissue. Both cell lines showed a higher RBE for cell survival than the value of 1.1 normally used for proton therapy. Repair capacity of DNA DSB was reduced following low energy proton irradiation and G2 arrest was induced to a larger degree. Further experiments are needed to elucidate if this could be a reason for lower cell survival.

Cell Cycle↗
PubMed1996

In hepatocellular carcinoma AgNOR protein expression correlates with tumour mass doubling time.

AIMS/METHODS: The relationship between AgNOR protein expression and doubling time was evaluated in 20 untreated nodules of hepatocellular carcinoma arising in cirrhotic liver. AgNOR protein quantity within the lesion was defined by image cytometry on histological sections from frozen biopsies obtained under ultrasound-guidance, selectively stained for AgNOR proteins. Tumour doubling time was calculated 6 months after diagnosis by measuring the volume variations of the nodules over a fixed period by "real time" ultrasonography. RESULTS: The doubling time of nodules characterized by high AgNOR protein area values (> 5.50 microns2, corresponding to the median AgNOR protein value) was shorter than that of nodules with low AgNOR protein area values (< 5.50 microns2). A highly significant difference in the mean doubling time values between the two groups (6.31 +/- 2.68 (E.S.) versus 15.92 +/- 3.03 (E.S.) months, respectively; p = 0.009) was found. Moreover, when the relationship between AgNOR protein and doubling time values was tested by linear regression analysis, a significant inverse correlation was observed (r = -0.68; p < 0.005). CONCLUSIONS: Our results indicate that AgNOR protein quantity represents a reliable parameter for predicting the tumour growth rate of untreated hepatocellular carcinoma nodules. Among the procedures commonly employed for the assessment of cell proliferation, the evaluation of the AgNOR parameter seems to be particularly suitable for kinetic analysis of ultrasound-guided fine-needle liver biopsies.

Adult↗
PubMed1996

Alteration of DNA ploidy and cell nuclearity in human hepatocellular carcinoma associated with HBV infection.

BACKGROUND/AIMS: Hepatocellular carcinoma usually arises in cirrhotic livers as a complication of chronic liver disease, and may show a variable trend towards increasing ploidy. The aim of this study was to investigate possible associations between different etiological factors, particularly hepatitis B virus and hepatitis C virus infection, and alteration of DNA-ploidy and nuclearity of neoplastic hepatocytes. METHODS: DNA-ploidy, the percentage of binucleated cells in the total cell population and the fraction of mononucleated hepatocytes in the polyploid compartment were assessed by image cytometry on cellular suspensions obtained by fine-needle biopsy from 60 hepatocellular carcinomas in patients whose viral status had previously been assessed. RESULTS: Significantly higher DNA-ploidy values (p = 0.005), with a reduction in the percentage of binucleated hepatocytes (p = 0.003) and an increase in the fraction of mononucleated hepatocytes in the polyploid compartment (p < 0.0001), were found in hepatocellular carcinoma with actual or previous hepatitis B virus infection (including also HCV+ve patients) in comparison to those not associated with hepatitis B virus infection, but not when HCV+ve hepatocellular carcinomas were compared to HCV-ve ones. Statistically significant differences for ploidy values (p < 0.05), percentage of binucleated hepatocytes (p < 0.05) and fraction of mononucleated hepatocytes in the polyploid compartment (p = 0.003) were also found between hepatocellular carcinoma associated only to hepatitis B virus infection ("pure" hepatitis B virus cases) and those associated only to hepatitis C virus infection ("pure" hepatitis C virus cases). CONCLUSIONS: Hepatocellular carcinoma associated with a previous or actual hepatitis B virus infection shows a peculiar phenotypical appearance, characterized by a trend towards increasing ploidy and reduction of binuclearity.

Adult↗
PubMed1997

Aberrant dipeptidyl peptidase IV (DPP IV/CD26) expression in human hepatocellular carcinoma.

BACKGROUND/AIMS: Diagnosis of small nodular lesions in the liver is often difficult because polarization of hepatocytes under pathological conditions is not as easily determined as for glandular or squamous epithelia. The aim of the present study was to investigate whether the bile canalicular enzyme dipeptidyl peptidase IV (DPP IV) would be useful to assess the pattern of hepatocellular surface polarity in liver sections. METHODS: Expression of DPP IV activity was determined by enzymatic cytochemistry and image cytometry in 25 human hepatocellular carcinomas and five cirrhotic livers removed at transplantation. Samples from the central and/or peripheral portion of neoplastic nodules and from surrounding tissue were analyzed in each case. Control specimens were obtained from normal liver of seven patients who underwent surgery for non-neoplastic conditions. RESULTS: In normal liver, DPP IV activity was confined to the bile canalicular plasma membrane with a zone 3 predominance in the hepatic acinus. This was also the case in the majority of pathological non-neoplastic livers, but the cell distribution pattern of DPP IV was altered in all hepatocellular carcinomas: 2/25 cases were completely devoid of DPP IV activity and in the remaining 23 DPP IV expressing hepatocellular carcinomas, three different patterns were observed that deviated distinctly from the typical canalicular pattern: (i) canaliculi were distorted and convoluted and contained an abnormally high DPP IV activity; (ii) canalicular activity was lost and enzymatic activity was restricted to isolated spots; (iii) pseudoacinar structures of hepatocytes with both basolateral and apical DPP IV expression appeared. CONCLUSIONS: It is concluded that DPP IV is a useful bile canalicular enzyme to assess the functional polarization of hepatocytes and that aberrant DPP IV expression occurs in human hepatocellular carcinoma.

Bile Canaliculi↗
PubMedDate not supplied

["New cytology" and diagnosis of malignant tumors].

Cytology is an old method of diagnosis: it is the microscopical observation of cells in the aim of their identification, of the recognition of morphological abnormalities to obtain diagnosis or prognosis informations. During the last 20 years, new technics have been developed: 1) Immunocytochemistry permits the identification of the tissue or the organ of which a tumoral cell population is born, the determination of its stage of differentiation, its kinetic and the diagnosis of bone marrow or lymph node metastasis. 2) With in situ molecular biology, it becomes possible to detect, at the cell level, virus, oncogenes or chromosomic abnormalities. 3) Flow and image cytometry are easy means for DNA content determination and for an objective and reproducible cell definition. None of these methods are able, at this time, to replace the cytological analysis, but they are useful, sometimes necessary, for the diagnosis and the prognosis evaluation of malignancy.

Biomarkers, Tumor↗
PubMed2003

Predictive variables for the biological behaviour of basal cell carcinoma of the face: relevance of morphometry of the nuclei.

We did a morphometric analysis of 130 histological sections of basal cell carcinoma (BCC) of the face to find out whether morphometric variables in the structure of the nuclei of BCC cells could serve as predictors of the biological behaviour. We considered the following variables: maximum and minimum diameters, perimeter, nuclear area and five form factors that characterise and quantify the shape of a structure (axis ratio, shape factor, nuclear contour index, nuclear roundness and circumference ratio). We did a statistical analysis of primary and recurring tumours and four histology-based groups (multifocal superficial BCCs, nodular BCCs, sclerosing BCCs and miscellaneous forms) using a two-sided t test for independent samples. Multifocal superficial BCCs showed significantly smaller values for the directly measured variables (maximum and minimum diameters, perimeter and nuclear area). Morphometry could not distinguish between primary and recurring tumours.

Adolescent↗
PubMed2000

Urban levels of air pollution modifies the progression of urethane-induced lung tumours in mice.

This paper investigates the effects of air pollution in urethane-induced lung tumours in mice by means of histological, morphometrical, and DNA ploidy. The experimental exposure was done in locations with different air pollution profiles: a polluted area (downtown São Paulo) and a "clean" environment. Swiss mice were employed and urethane (3 g/kg) was used as a carcinogenic substance. All the animals, whether exposed or not to air pollution, were sacrificed after 6 months, and the lung lesions were analysed. The results showed a significant effect of air pollution on tumour progression, observed by changes in the phenotype of the tumour cells as demonstrated by morphometry and DNA ploidy. We observed more atypical adenomas in the air pollution-exposed group (p = 0.02). Coherently, morphometric differences were also detected between the two groups. Neoplasms of exposed mice exhibited an increase in the nuclear fraction (p = 0.002) and in the nucleus/cytoplasm ratio (p = 0.011), as a decrease in the stromal fraction (p < 0.001). There was a higher risk of aneuploidy in the 6-months-of-air-pollution-exposure group (relative risk: 1.58; 95% of confidence interval: 1.007 to 2.403). These results indicate that urban air pollution accelerates the process of progression towards malignancy.

Adenoma↗
PubMed1999

Multiple endometrial stromal nodules with sparse cysts and glands in the lung--a nodular variation of endometriosis that may mimic metastases of sarcoma.

We report an unusual case of a nodular variation of pulmonary endometriosis. To our knowledge, there is no previous report on a morphological investigation of this entity. The etiology of this rare condition is still a matter of discussion. The well-circumscribed nodular mass is composed of cells identical to, or closely resembling, those of endometrial stroma containing sparse cysts and glands. Immunohistochemically, the cells showed an extensive co-expression of cytokeratin AE1/AE3 and vimentin and were highly positive for progesterone receptor (PRICA) and estrogen receptor (ERICA). Cells lining the cysts and glands as a monolayer were reactive for Ber-Ep4, cytokeratin Pan and cytokeratin AE1/AE3 and negative to all other markers used including PRICA and ERICA. The differential diagnosis of this entity included fibrous tumor of the pleura and metastatic low-grade-endometrial-stromal-sarcoma. The morphological findings are correlated with immunohistochemical studies and results of cell image analysis. This study details the clinicopathological features of the nodular variation of pulmonary endometriosis.

Adult↗
PubMed2002

Histologic precursors of gastrointestinal tract malignancy.

Precursor lesions in the GIT include flat dysplasias, adenomas, dysplasia superimposed on nonneoplastic polyps, endocrine cell dysplasia, ACF, and condyloma accuminatum. Interobserver variability can be a problem in reporting dysplasia, and ancillary techniques including flow cytometry, image analysis, proliferation markers, and examination for p53 expression can help in this task. Squamous dysplasia seen in the esophagus and anus is graded on either a two-tiered or three-tiered system largely based on the extent of mucosal involvement. Glandular dysplasia is morphologically similar whether seen as an adenomatous polyp or within the setting of Barrett's esophagus, atrophic gastritis, or idiopathic inflammatory bowel disease. The distinction between LGD and HGD in glandular mucosa is based on the severity of cytologic and architectural distortion. Type I dysplasia is the classic adenomatous pattern seen most commonly and recognized by the presence of elongate hyperchromatic stratified nuclei. Type II, the nonadenomatous variant, contains vesicular nuclei and alteration in nuclear size and shape. Nonantral endocrine dysplasia in the stomach is seen in the setting of corporal predominant atrophic chronic gastritis and Zollinger-Ellison syndrome with Multiple Endocrine Neoplasia syndrome type I. Condyloma accuminatum is a HPV-related lesion most commonly seen in men practicing anal intercourse. Superimposed squamous dysplasia can be seen with HGD most frequently in the HIV-positive population. Recognition of the different classification systems of dysplasia, the most frequent settings in which these lesions are found, and their natural history is important for all practicing gastroenterologists and pathologists.

Carcinoma, Squamous Cell↗
PubMed2002

Automated microaxial tomography of cell nuclei after specific labelling by fluorescence in situ hybridisation.

Microaxial tomography provides a good means for microscopic image acquisition of cells or sub-cellular components like cell nuclei with an improved resolution, because shortcomings of spatial resolution anisotropy in optical microscopy can be overcome. Thus, spatial information of the object can be obtained without the necessity of confocal imaging. Since the very early developments of microaxial tomography, a considerable drawback of this method was a complicated image acquisition and processing procedure that requires much operator time. In order to solve this problem the Heidelberg 2pi-tilting device has been mounted on the Brno high-resolution cytometer as an attempt to bring together advanced microscopy and fast automated computer image acquisition and analysis. A special software module that drives all hardware components required for automated microaxial tomography and performs image acquisition and processing has been developed. First, a general image acquisition strategy is presented. Then the procedure for automation of axial tomography and the developed software module are described. The rotation precision has been experimentally proved followed by experiments with a specific biological example. For this application, also a method for the preparation of cell nuclei attached to glass fibres has been developed that allows for the first time imaging of three-dimensionally conserved, fluorescence in situ hybridisation-stained cell nuclei fixed to a glass fibre.

Cell Nucleus↗
PubMedDate not supplied

Cardiac myocyte nuclear size and ploidy status decrease after mechanical support.

Two patients with end-stage dilated cardiomyopathy of ischemic and idiopathic origin were treated with a left ventricular assist device (LVAD) as a bridge for heart transplantation. Myocardial tissue was collected during LVAD insertion and from the left ventricular apex of the explanted hearts. The myocyte diameter, nuclear area and DNA content of myocyte nuclei were measured by static cytomorphometry in tissue sections and in isolated myocytes with a digital analysis system. The presence of apoptotic nuclei was investigated by the TdT mediated X-dUTP nick end labeling technique (TUNEL). The prolonged use of a LVAD was associated with a reduction in myocyte diameter, indicating that the LVAD may induce a reversion of myocyte hypertrophy, a process described as "reverse remodeling." In addition, unloading of the heart induced a reduction in the size and DNA content of myocyte nuclei. These results suggest that the cardiomyocyte nuclei are in a dynamic state and, as it occurs with cell hypertrophy, nuclear hypertrophy and polyploidization may be a reversible phenomenon.

Adult↗
PubMed2002

FDG-PET in the pretherapeutic evaluation of primary squamous cell carcinoma of the oral cavity and the involvement of cervical lymph nodes.

PURPOSE: The diagnostic role of positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) in squamous cell carcinoma of the oral cavity is evaluated. PROCEDURES: In 38 patients, the results of FDG-PET, magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound were compared. The standard uptake values (SUV) of FDG-PET were correlated to histopathological grading and DNA-image cytometry. RESULTS: In the case of lymph node metastases, the sensitivity of FDG-PET (93%) was higher than the sensitivity for the compared methods. The specificity was best for CT. SUVs of diploid tumor cell lines seemed to be lower than in non-diploid tumor cell lines. CONCLUSIONS: The high sensitivity and the high negative predictive value of PET may lead to more restrictive therapeutic regimens regarding lymph node metastases. Studies are necessary regarding possible relationships between glucose metabolism and tumor grading.

Journal Article↗
PubMed2000

Characterization of a plasmid region involved in Bacillus anthracis toxin production and pathogenesis.

The germination of spores within the host is the initial step of anthrax infection. We have shown, using immunofluorescence staining, confocal scanning laser microscopy and image cytometry analysis, that the alveolar macrophage is the primary site of B. anthracis germination in a murine inhalation infection model. B. anthracis germinated inside macrophages, in vesicles derived from the phagosomal compartment. We have demonstrated that the toxin genes and their trans-activator, AtxA, are expressed within the macrophages after germination. It was also shown that the pXO1 plasmid strongly enhanced capsule formation and that this influence is mediated by AtxA. This indicates the existence of a regulon where AtxA is the regulatory protein acting on genes located on different plasmids. We identified a tricistronic germination operon gerX located between the pag and atxA genes on the 40-kb toxin-encoding fragment of pXO1 . Analysis of a gerX null mutant indicated that gerX-encoded proteins are involved in the virulence of B. anthracis.

Antigens, Bacterial↗