Cancer genetics

Chromosomes, genes, and development of testicular germ cell tumors

A literature review found 265 articles on testicular germ cell tumors (TGCTs) detailing the copy number of chromosomal regions and expression of 245 genes. An initial precursor stage, intratubular germ cell neoplasia (IGCN), is characterized by triploidization and an upregulation of KIT, ALPP, CCDN2, and ZNF354A, and a downregulation of CDKN2D. TGCT regularly have a series of chromosomal aberrations: a decrease in copy number at 4q21 approximately qter and 5q14 approximately qter; an increase at 7p21 approximately pter, 7q21 approximately q33, and 8q12 approximately q23 (especially high increase in seminoma); a decrease at 11p11 approximately p15 and 11q14 approximately q24; an increase at 12p11 approximately pter; a decrease at 13q14 approximately q31; an increase of 17q11 approximately q21 (only for nonseminoma); a decrease of 18q12 approximately qter; and an increase at 21q21 approximately qter, 22q11 approximately qter (only for seminoma), and Xq. Macroscopically overt TGCT is associated with a characteristic series of abnormalities in the retinoblastoma pathway including upregulation of cyclin D2 and p27 and downregulation of RB1 and the cyclin-dependent kinase inhibitors p16, p18, p19, and p21. TGCT thus has a synergistic pattern in gene expressions of the retinoblastoma pathway that is rare in other malignancies.

Metabolic mapping with bioluminescence: basic and clinical relevance

This review is focused on metabolic mapping in biological tissue with quantitative bioluminescence and single photon imaging. Metabolites, such as ATP, glucose and lactate, can be imaged quantitatively and within microscopic dimensions in cryosections from shock frozen biological specimens using enzyme reactions and light emission by luciferases. The technique has been applied in numerous targets and models of experimental biomedical research, such as multicellular spheroids, various organs of laboratory animals in a physiological or pathophysiological state, and even in plant seeds. Among numerous other aspects, data obtained with this method have contributed to the elucidation of mechanisms that are involved in the development of necrosis in multicellular spheroids. The combination of the bioluminescence technique with immunohistochemistry, autoradiography or in situ hybridization can considerably reduce ambiguities in the interpretation of the experimental results. Although, an invasive technique, bioluminescence imaging has been used most intensively in clinical oncology using tumor biopsies taken at the first diagnosis of the disease. It has been shown for squamous cell carcinomas of the head and neck and of the uterine cervix that accumulation of high levels of lactate in the primary lesions is associated with a high risk of metastasis formation and a reduced overall and disease-free patient survival. Thus, metabolic imaging can provide additional information on the degree of malignancy and the prognosis of tumors which may help the oncologist in improving specific treatment approaches for each individual malignant disease. Last but not least, metabolic mapping in clinical oncology has stimulated a number of investigations in basic cancer research on mechanisms that underlie the correlation between tumor metabolism and malignancy.

Adenovirus-mediated p53 growth inhibition of ovarian cancer cells is independent of endogenous p53 status

OBJECTIVE

The aim of this study was to determine the effect of transfection of adenovirus-mediated wild-type p53 into ovarian cancer cells with both wild-type and mutant endogenous p53.

STUDY DESIGN

Eight human ovarian cancer cell lines were used: three with p53 mutations, one that is p53 null, and four with wild-type p53. The recombinant p53 adenovirus (Adp53) contains the cytomegalovirus promoter, wild-type p53 cDNA, and SV40 polyadenylation signal in a minigene cassette inserted into the E1-deleted region of modified Ad5. The transduction efficiency of cells was assessed using a beta-gal-containing adenovirus. Cell-counting assays were used to evaluate the effect of transfection with Adp53 on the growth of cells. P53 expression was evaluated using Western blot. Cell cycle analysis and apoptosis studies were done using a tunnel-based assay and fluorescent activated cell sorting.

RESULTS

Transduction efficiencies varied between cell lines. More than 90% growth inhibition occurred in seven of eight cell lines after infection with adenovirus-mediated p53 if a viral dose leading to at least 50% of cells infected was used. Regardless of endogenous p53 status, apoptosis occurred in cells infected with p53.

CONCLUSIONS

Ovarian cancer cells are growth inhibited by transfection with adenovirus-mediated p53 regardless of their endogenous p53 status. Growth inhibition is related to transduction efficiency.

APM-1, a novel human gene, identified by aberrant co-transcription with papillomavirus oncogenes in a cervical carcinoma cell line, encodes a BTB/POZ-zinc finger protein with growth inhibitory activity

Integration of human papillomavirus (HPV) DNA into the host cell genome is an important step in cervical carcinogenesis. In tumour cells with integrated HPV DNA, transcription of viral oncogenes E6 and E7 continues into the flanking cellular sequences thereby producing viral-cellular fusion transcripts. Analysis of cellular sequences flanking the integrated HPV68 DNA in the cervical carcinoma cell line ME180 revealed homozygosity of the mutant allele in ME180 cells. We speculated that this could indicate the existence of a cellular tumour suppressor gene in the integration region. We report here the identification of a novel human gene, named APM-1, which is co-transcribed with the HPV68 E6 and E7 genes and is present in the 3'-cellular part of the ME180 viral-cellular fusion transcripts. The APM-1 gene encodes a protein with a BTB/POZ domain and four zinc fingers, and is located at chromosome 18q21. APM-1 transcripts are detected in normal cervical keratinocytes, but not in the majority of cervical carcinoma cell lines analysed. The APM-1 gene caused a reduction of clonal cell growth in vitro of HeLa and CaSki tumour cells. These characteristics make APM-1, the first novel human gene identified in a HPV integration region, a likely candidate for the postulated tumour suppressor gene.

Aging mechanisms in fruit files

Genetic analysis of Drosophila has provided evidence in support of two proposed evolutionary genetic mechanisms of aging: mutation accumulation and antagonistic pleiotropy. Both mechanisms result from the lack of natural selection acting on old organisms. Analyses of large numbers of files have revealed that mortality rates do not continue to rise with age as previously thought, but plateau at advanced ages. This phenomenon has implications both for models and for definitions of aging, and may be explained by the evolutionary theories. The physiological processes and genes most relevant to aging are being identified using Drosophila lines selected in the laboratory for postponed senescence. Oxidative stress and insufficient metabolic reserves/capacity may be particularly important factors in limiting the fruitfly lifespan. Genes which exhibit aging-related changes in expression are now being identified. Transgenic files are being used to analyze the mechanisms of such aging-related gene expression, and to test the effects of specific genes on aging and aging-related deterioration.

Domains A and B in the Rb pocket interact to form a transcriptional repressor motif

The retinoblastoma protein (Rb) is a tumor suppressor that regulates progression from the G1 phase to the S phase of the cell cycle. Previously, we found that Rb is a transcriptional repressor that is selectively targeted to promoters through an interaction with the E2F family of cell cycle transcription factors--when Rb is tethered to a promoter through E2F, it not only blocks E2F activity, it also binds surrounding transcription factors, preventing their interaction with the basal transcription complex, thus resulting in a dominant inhibitory effect on transcription of cell cycle genes. Here we examine the repressor motif of Rb. The two domains in the Rb pocket, A and B, which are conserved across species and in the Rb-related proteins p107 and p130, are both required for repressor activity. The nonconserved spacer separating A and B is not required. Although neither A nor B alone had any repressor activity, surprisingly, repressor activity was observed when the domains were coexpressed on separate proteins. Transfection assays suggest that one domain can recruit the other to the promoter to form a repressor motif that can both interact with E2F and have a dominant inhibitory effect on transcription. Using coimmunoprecipitation and in vitro binding assays, we show that A and B interact directly and that mutations which disrupt this interaction inhibit repressor activity. The Rb pocket was originally defined as the binding site for oncoproteins from DNA tumor viruses such as adenovirus E1a. We present evidence that E1a interacts with a site formed by the interaction of A and B and that this interaction with A and B induces or stabilizes the A-B interaction.

Invasiveness of endometriotic cells in vitro

The pathogenesis of endometriosis is not known. The currently favoured theory is that viable endometrial cells, shed from the endometrium into the pelvic cavity by retrograde menstruation, reattach and invade other tissues. We used a collagen gel invasion assay to assess invasive potential of endometriotic cells. The invasion indices of cells from peritoneal endometriotic lesions and a metastatic bladder carcinoma cell line (EJ28) were similar (2.2-15.6 vs 8.4-11.6) whereas cells from normal endometrium and non-metastatic carcinoma cells (RT112) were non-invasive (indices < 1). Invasiveness of endometriotic cells might contribute to the pathogenesis of endometriosis.

Oesophageal cancer and amplification of the human cyclin D gene CCND1/PRAD1

The human CCND1/PRAD1 gene, located in the 11q13 chromosomal region, encodes a cyclin D protein with potential oncogenic capacity and is involved in several human malignancies. The amplification and expression status of CCND1 was investigated in a series of oesophageal tumours. CCND1 is amplified in 54% and overexpressed in 63% of the tumours of the squamous cell type.

Human cancer predisposition and the implications for radiological protection

It is well established from clinical, epidemiological and laboratory studies that specific human germ line mutation can predispose to spontaneously arising cancer. Some of the responsible genes have been characterized at the molecular level and evidence is rapidly accumulating on mechanistic aspects of the problem. A major outstanding issue is the extent to which genetically determined cancer predisposition in man interacts with exposures to environmental genotoxic agents such as ionizing radiation. This brief review considers the current position regarding the different forms and frequencies of cancer-predisposing mutations in the human population and provides an interim view of the possible implications for protection of man from ionizing radiation.