Stages Of Cancer Development Research Articles

Elevated expression of eIF4E in confined early breast cancer lesions: possible role of hypoxia.

The translation-initiation factor eIF4E is rate-limiting for protein synthesis, and its over-expression results in oncogenic transformation of mammalian cells. eIF4E facilitates the synthesis of several powerful tumor angiogenic factors (FGF-2 and VEGF) by selectively enhancing their translation. In breast carcinomas, eIF4E is commonly over-expressed, but the pathology where this elevation is initially manifested is presently unknown. To probe whether the elevation of eIF4E marks an early stage of cancer development, we focused our research on early cancerous lesions. We have analyzed 70 invasive ductal carcinomas (IDCs), 78 ductal carcinomas in situ (DCIS), 51 benign lesions and 4 model cell lines for elevated expression of eIF4E by several different methods: Northern/Western blots, immuno-histochemistry and in situ RT-PCR. eIF4E expression was markedly increased in IDC and in islets of viable cells in the center of poorly vascularized DCIS, which are not easily identifiable by standard histological stains. We also show that expression of eIF4E is increased by hypoxia and, presumably, in hypoxic areas of these lesions. We propose that clonal expansion of cancer cells, permanently over-expressing eIF4E, gives them a critical advantage to survive hypoxia and marks the transition toward the vascular phase of cancer progression. Hence, eIF4E may be useful in stratifying DCIS lesions according to their malignant stage.

Elevated expression of eIF4E in confined early breast cancer lesions: Possible role of hypoxia

The translation-initiation factor eIF4E is rate-limiting for protein synthesis, and its over-expression results in oncogenic transformation of mammalian cells. eIF4E facilitates the synthesis of several powerful tumor angiogenic factors (FGF-2 and VEGF) by selectively enhancing their translation. In breast carcinomas, eIF4E is commonly over-expressed, but the pathology where this elevation is initially manifested is presently unknown. To probe whether the elevation of eIF4E marks an early stage of cancer development, we focused our research on early cancerous lesions. We have analyzed 70 invasive ductal carcinomas (IDCs), 78 ductal carcinomas in situ (DCIS), 51 benign lesions and 4 model cell lines for elevated expression of eIF4E by several different methods: Northern/Western blots, immuno-histochemistry and in situ RT-PCR. eIF4E expression was markedly increased in IDC and in islets of viable cells in the center of poorly vascularized DCIS, which are not easily identifiable by standard histological stains. We also show that expression of eIF4E is increased by hypoxia and, presumably, in hypoxic areas of these lesions. We propose that clonal expansion of cancer cells, permanently over-expressing eIF4E, gives them a critical advantage to survive hypoxia and marks the transition toward the vascular phase of cancer progression. Hence, eIF4E may be useful in stratifying DCIS lesions according to their malignant stage. Int. J. Cancer 80:516–522, 1999. © 1999 Wiley-Liss, Inc.

A Probability-based Multivariate Statistical Algorithm for Autofluorescence Spectroscopic Identification of Oral Carcinogenesis

Abstract— A probability-based multivariate statistical algorithm combining partial least-squares (PLS) and logistic regression was developed to identify the development stages of oral cancer through analysis of autofluorescence spectra of oral tissues. Tissues were taken from a 7, 12-dimethyl-benz[a]anthracene-induced hamster buecal pouch carcinogenesis model. Analyses were conducted at various excitation wavelengths, ranging from 280 nm to 400 nm in 20 nm increments, to assess classification performance at different excitations. For each excitation the PLS analysis and logistic regression were combined, on the basis of cross validation, to calculate the posterior probabilities of samples belonging to four stages of cancer development: normal tissues, hyperplasia, dysplasia and early cancers and frankly invasive cancers. Results showed that the 320 nm excitation wavelength optimally classified the cancer development stages: the accuracy rates for identifying samples at that excitation were 91.7%, 83.3%, 66.7% and 83.3% for the four respective stages. The average accuracy rate was 81.3%. These results suggest that the algorithm described in this study might be useful for the detection of human oral cancers.

Free Radicals and Glycoxidative Stress in Ageing and Age‐Related Diseases

Abstract. Free radicals and glycoxidative reactions are known to be associated with ageing on the level of the cell and whole organism. Free radicals are ubiquitous in living things and they lead to irreversible reactions in cell organelles and cell metabolism. One important source of free radicals is advanced glycation end products (AGEs) resulting from non‐enzymatic glycation and oxidation of proteins and lipids. Ageing, and thus life span, correlate with free radical generation and antioxidative defense as well as with advanced glycation end products. Most chronic diseases are also associated with free radicals and AGEs. Overproduction of free radicals accelerates cell ageing and is counteracted by antioxidants. Antioxidant status is in part amendable through nutritional and pharmacological interventions. AGE interaction with its receptor contributes also to accelerated ageing in many pathological conditions. Particularly vulnerable are long‐lived proteins, eg. in lens crystallin and skin collagen. The analysis of the mechanism generating free radicals and of the reaction of AGEs with cellular metabolism opens new avenues for the delaying of the development of chronic diseases such as atherosclerosis and neurodegenerative disease. On the other hand, the impact of free radicals on carcinogenesis may differ according to the cancer stage and hence the preventive potential of antioxidants is proposed to be different in early and late stages of cancer development. Free radicals and AGE products are important mediators of age‐related diseases and ageing per se. Intake of antioxidants over the life‐time determines, among other factors, the rate of ageing and the development of degenerative diseases. Interventive strategies such as soluble receptors for AGEs and effective antioxidants might become important therapeutic strategies in the near future.

Partial Least-Squares Discriminant Analysis on Autofluorescence Spectra of Oral Carcinogenesis

A partial least-squares (PLS) discriminant analysis on the autofluorescence spectra of oral squamous cell carcinoma based on the cross-validation technique was conducted to discriminate among oral tissues at different cancer development stages. These tissues were obtained from hamsters of DMBA-induced buccal pouch carcinogenesis. The study on the fluorescence spectra of the cancer tissues revealed that 320 nm might be the optimal excitation wavelength, and it was selected for the discriminating analysis. The PLS discriminant plot based on cross-validation showed that tissues of oral carcinogenesis belonging to four clinically important cancer development stages—normal tissues, hyperplasia, dysplasia and early cancers, and frankly invasive cancers—could be classified by using the first two PLS factors that emerged from the fluorescence spectra at 320 nm excitation. The PLS factor loading plots of the first PLS factor of 320 and 360 nm excitations showed that the first PLS factor was correlated to the fluorescent structure changes. This study indicates that further development of the PLS discriminant analysis on the autofluorescence spectra may be useful for developing a simple and efficient discriminating algorithm for the identification of different stages of human oral carcinogenesis.

Application of PIXE analysis to determination of trace elements in colonic tumor disease

In order to investigate the validity of the cancer development, the presence of active oxygen need to be taken into account since active oxygen participates in the initiation and promotion of cancer. However, it is impossible to measure the amount of active oxygen in vivo directly. Therefore, the levels of trace elements such as Zn, Cu and Mn in enzyme which eliminates active oxygen were measured at each stage of cancer development by PIXE. The large differences between the normal mucosa and colonic adenoma in the amount of Zn, Cu and Mn within the enzyme eliminating free radicals were observed. There was a significant relationship among trace element levels, active oxygen and the development of tumor in connection with the levels of Zinc and Copper.

Circadian-system alterations during cancer processes: a review.

Murine and human data have indicated that tumors and tumor-bearing hosts may exhibit nearly normal or markedly altered circadian rhythms. Amplitude damping, phase shifts, and/or period (tau) change, including appearance of ultradian rhythms (with tau < 20 hr) usually become more prominent at late stages of cancer development. The extent of rhythm alterations also varies according to tumor type, growth rate and level of differentiation. While "group chronotherapy," i.e., administration of the same chronomodulated schedule to cancer patients, has increased chemotherapy efficacy and/or tolerability, cancer patients' individual circadian rhythms now need to be explored on a large scale, in order to estimate the incidence of cancer-associated circadian-system alterations and to understand the underlying mechanisms. Correlations between such alterations and patient outcome must be established in order to specify the need for individualized chronomodulated delivery schedules and/or specific rhythm-oriented therapy, especially in patients with circadian-system disturbances.

Carcinogen-induced alteration in liver epidermal growth factor receptor distribution during the promotion stage of hepatocarcinogenesis in rat.

Changes in hepatic membrane binding capacity for epidermal growth factor (EGF) were assessed during 2-acetylaminofluorine (2-AAF)-induced hepatocarcinogenesis. An overall decrease in membrane EGF binding levels was observed throughout the period of 2-AAF administration. Immunochemical studies indicated the decreases in EGF binding levels were paralleled by decreases in tissue EGF receptor levels. Immunohistochemical studies showed that the losses in hepatic EGF receptor levels were not uniform throughout the liver during the early, promotion stage of cancer development. During the promotion stage, preneoplastic liver nodules were found to display a higher level of EGF receptor than surrounding hepatic tissue. This resistance to 2-AAF-mediated down-regulation of EGF receptor may confer a proliferative advantage to the developing nodule relative to the surrounding liver tissue. Similar immunochemical and immunohistochemical analysis of hepatocarcinomas at late stages of 2-AAF-induced hepatocarcinogenesis indicated a uniform loss of EGF receptor in tumor and surrounding tissue. These studies indicate that carcinogen-mediated changes in EGF binding levels are different during the multistage process of hepatocarcinogenesis, and that resistance to down-regulation of EGF receptor among preneoplastic nodules may have a role in providing a selective growth advantage to initiated cell populations. EGF receptor may be useful as a dynamic marker assessing the development of hepatic tumors.

Human papilloma viruses andp53 mutations in normal, pre-malignant and malignant oral epithelia

HPV infections have been previously observed in oral cancers, and inactivation of the p53 gene has been shown to be one of the most common genetic alterations in human tumors. We examined 179 oral specimens from 70 individuals with histologic findings of either normal mucosa (n = 6) or oral disease that ranged from mild dysplasia to invasive squamous-cell carcinoma (n = 64) to determine the occurrence of both HPV infection and p53 mutations and their relationship with several clinical factors. HPV infection was detected by PCR amplification of viral DNA, and the presence of p53 mutations was assayed using the single-strand conformation polymorphism (SSCP)-PCR technique. HPV infection was found in 31% of individuals with oral disease and was not seen in healthy individuals. Mutations in exons 5, 6, 7 or 8 of the p53 gene were detected in 37.5% of patients with oral lesions and in a biopsy from 1 healthy individual who was a heavy smoker. Approximately one-third of lesions classified as pre-malignant (dysplasia and carcinoma in situ) and 42% of invasive carcinomas contained p53 mutations. The majority of these mutations were G:T transversions located within exons 7 and 8. Tumor tissues from 6 patients with oral lesions were found both to be HPV-16-positive and to contain p53 mutations; of these, 4 were poorly differentiated carcinomas that were diagnosed as late-stage disease. In this study, p53 mutations were detected in the early stages of cancer development.

Novel hypotheses for the roles of EBNA-1 and BHRF1 in EBV-related cancers.

Epstein-Barr virus has been linked to several types of human cancer including Burkitt's lymphoma and nasopharyngeal carcinoma but the mechanisms by which the virus might contribute to cancer remain obscure. Here we consider the possibility that EBNA-1, which is expressed in both tumours, directly transactivates cell genes. The EBNA-1 protein was tested for transcription transactivation domains and the human genome was screened for high-affinity EBNA-1-binding sites that might mediate transactivation. None were found, although novel low-affinity-binding sites in the EBV genome were detected. We also investigated the expression of BHRF1, the viral homologue to bcl-2, in epithelial cells and showed that it is expressed in vivo in the EBV replication found in oral hairy leukoplakia. A novel hypothesis is proposed for nasopharyngeal carcinoma in which BHRF1 expression protects cells against apoptotic death caused by environmental DNA damaging agents and thus contributes to the early stages of cancer development.

Genetics, molecular biology and colorectal cancer

Colorectal cancer (CRC) develops through several histologically well-defined stages, reflecting the sequential acquisition of genetic alterations. Several frequently mutated genes have been identified which probably contribute to the development of both hereditary and sporadic cancer (reviewed in Bishop and Thomas, 1990; Fearon and Vogelstein, 1990; Fearon and Jones, 1992; Hamilton, 1992). Several generalizations emerge from this work. Mutations are observed in the earliest detectable stages of cancer development. Specific genes tend to be mutated in a given order, but it is the accumulation of a critical number of lesions which governs the appearance of neoplasia. Mutations actively promote neoplastic character by activating oncogenes and eliminate restraints on neoplastic character by inactivating tumour suppressor genes.

Appearance of Ulex europaeus Agglutinin‐1 and Griffonia simplicifolia Agglutinin‐1 Binding Sites on Cancer Cells in Sigmo‐rectal Polyps

Ninety-three polypectomized cases from the sigmo-rectal region were examined by lectin histochemistry. On the apical surface, the UEA-1 binding sites were positive in 24/29 carcinomas and in 25/62 adenomas; while the GSA-1 binding sites were positive in 16/29 carcinomas and in 0/62 adenomas. In 2 non-neoplastic polyps, only one case was UEA-1 positive; none was GSA-1 positive. In neighbouring regions, adenomas adjacent to carcinomas were UEA-1 positive in 9/27 cases and GSA-1 positive in 3/37 cases. Thus, the GSA-1 binding sites were expressed more specifically on carcinomas. In the Golgi area, none of the polyps was UEA-1 positive while most of the cells showing GSA-1 positivity were apt to do so within the cells without showing GSA-1 positivity on the apical surface. There were no correlations between the positive rate of the lectin binding sites on the apical surface and the stage of cancer development or the histology of the adenoma on which a cancer developed. The meaning of this restricted appearance of the GSA-1 binding sites on the cancer cell surface was discussed in relation to observations previously reported in the literature.

Criteria, mechanisms, and potency evaluation for tumor promoters: Dioxin as a model

The promotion stage of cancer development involves the reversible clonal growth of initiated cells with an altered expression of several protein markers. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most potent promoting agent known with a Promotion Index in excess of 10 6. The time dependence (1–5 months) of promotion by biweekly injections of 0.14 μg TCDD/kg (equivalent to 0.01 μg TCDD/day was determined in female rats treated with diethylnitrosamine (10 mg/kg) in an initiation-promotion paradigm. In addition, the reversibility of promotion by TCDD was assessed in rats maintained for 6 months without TCDD administration after 1 to 5 months of TCDD administration. Whereas the number of altered hepatic foci (AHF) observed was decreased in animals promoted with TCDD and subsequently withdrawn from further TCDD administration for 6 months prior to sacrifice, the volume percentage of the liver occupied by AHF was increased with this regimen, suggesting that sufficient TCDD may remain in the liver after 6 months to maintain promotion or, alternatively, that TCDD exhibits progressor as well as promoter activity.

Facts and theories concerning the mechanisms of carcinogenesis

Carcinogenesis can be induced experimentally by exposure to exogenous agents or it can occur spontaneously without intentional or active intervention. Carcinogenesis can be actively induced by chemicals, radiation, infectious biological agents, transgenesis, or selective breeding. In the human and occasionally when testing potential carcinogens in animals, cancer may result from passive exposure to carcinogens encountered in the ambient environment or from changes in the internal milieu of the animal. Many carcinogens alter the structure of DNA resulting in carcinogenesis, but a significant number of carcinogens do not appear to act through this mechanism. When the action of specific carcinogenic agents is considered in relation to the stages of cancer development, initiation, promotion, and progression, the mechanism of the induction of carcinogenesis by DNA-reactive agents that alter genomic structure can be reconciled with those agents that do not act in this manner. As some cells are fortuitously initiated by uncontrolled variables such as irradiation and through changes in normal processes, the stimulation of growth and altered genetic expression by nongenotoxic agents may result indirectly in cancer development. The final stage of carcinogenesis, progression, can occur spontaneously, enhanced by formation and propagation of genetic errors due to increased cellular proliferation associated with the promotion stage. In addition, chemical and viral agents that lack the capacity for initiation and promotion may actively convert cells in the stage of promotion to the stage of progression. Therefore, the diverse mechanisms of action of carcinogenic agents in relation to their effects on specific stages in the natural history of cancer development allow for greater congruence of many of the theories of carcinogenesis. The influence of the roles of nongenotoxic carcinogenic agents and the potential role of progressor agents on the carcinogenesis process allow a more accurate identification of the potential risk that specific carcinogenic agents pose for increasing human cancer.

Studying lung cancer in the laboratory--2: Chemosensitivity testing.

<h3>Abstract</h3> Spontaneous mutations can alter tissue dynamics and lead to cancer initiation. While large-scale sequencing projects have illustrated processes that influence somatic mutation and subsequent tumour evolution, the mutational dynamics operating in the very early stages of cancer development are currently not well understood. In order to explore mutational dynamics in the early stages of cancer evolution we exploited neoplasia arising spontaneously in the <i>Drosophila</i> intestine. We analysed whole-genome sequencing data through the development of a dedicated bioinformatic pipeline to detect structural variants, single nucleotide variants, and indels. We found neoplasia formation to be driven largely through the inactivation of <i>Notch</i> by structural variants, many of which involve highly complex genomic rearrangements. Strikingly, the genome-wide mutational burden of neoplasia - at six weeks of age - was found to be similar to that of several human cancers. Finally, we identified genomic features associated with spontaneous mutation and defined the evolutionary dynamics and mutational landscape operating within intestinal neoplasia over the short lifespan of the adult fly. Our findings provide unique insight into mutational dynamics operating over a short time scale in the genetic model system, <i>Drosophila melanogaster</i>.

Stages in Cancer Development: Opportunities for Thresholds

It has now been established that many factors can influence the development of cancer in animal models. Epidemiologic studies support the concept of a similar situation in human populations with particular emphasis on lifestyle. Types of cancer which appear to be excellent candidates for such influences are colon, breast and lung. In the case of each there are antecedent (pre-neoplastic) changes in morphology of focal areas in the organ or tissue and a lag time varying from a few years to decades. It seems logical that thresholds do exist in some such cases and that if a threshold is not exceeded for whatever substance or condition may be primary to the cardnogenesis process, the atypical cellular alterations may regress or at most remain static. Furthermore, factors associated with lifestyle, including diet, can likely determine whether or not the progress toward malignancy is initiated, inhibited, or enhanced in a given organ or tissue. A number of factors or conditions which may relate to inhibiting or enhancing cardnogenesis are considered in this presentation. Mechanisms for such effects may be mediated by raising or lowering thresholds. This area of research requires increased emphasis in our efforts to prevent cancer.

Cancer-promoting effects of phenols in tea

Black tea (10 kg) bought at the local market was extracted and separated into four fractions. With spectroscopic and gas chromatographic methods phenols and dimethylphenols were found in the phenolic fraction. An initial application of 1% acetone solution of 3/4 benzopyrene to the neck region of each of 15 young Swiss mice was followed by paintings of tea to the neck region on alternate days for 55 applications. A control group of 15 similar mice received only the single benzopyrene painting. The control mice developed no skin lesions, but all of the mice treated with benzopyrene plus tea demonstrated various stages of cancer development. To produce cancer it is not necessary that both initiator and promoter agents be present in the same product; they may be completely separate in origin. The author concludes that we should become increasingly concerned about our environment, which contains in many instances minute amounts of initiators and larger amounts of promoters.