Marcelo L. Larramendy

DNA Copy Number Losses in Human Neoplasms

This review summarizes reports of recurrent DNA sequence copy number losses in human neoplasms detected by comparative genomic hybridization. Recurrent losses that affect each of the chromosome arms in 73 tumor types are tabulated from 169 reports. The tables are available online at http://www.amjpathol.org and http://www. helsinki.fi/ approximately lglvwww/CMG.html. The genes relevant to the lost regions are discussed for each of the chromosomes. The review is supplemented also by a list of known and putative tumor suppressor genes and DNA repair genes (see Table 1, online). Losses are found in all chromosome arms, but they seem to be relatively rare at 1q, 2p, 3q, 5p, 6p, 7p, 7q, 8q, 12p, and 20q. Losses and their minimal common overlapping areas that were present in a great proportion of the 73 tumor entities reported in Table 2 (see online) are (in descending order of frequency): 9p23-p24 (48%), 13q21 (47%), 6q16 (44%), 6q26-q27 (44%), 8p23 (37%), 18q22-q23 (37%), 17p12-p13 (34%), 1p36.1 (34%), 11q23 (33%), 1p22 (32%), 4q32-qter (31%), 14q22-q23 (25%), 10q23 (25%), 10q25-qter (25%),15q21 (23%), 16q22 (23%), 5q21 (23%), 3p12-p14 (22%), 22q12 (22%), Xp21 (21%), Xq21 (21%), and 10p12 (20%). The frequency of losses at chromosomes 7 and 20 was less than 10% in all tumors. The chromosomal regions in which the most frequent losses are found implicate locations of essential tumor suppressor genes and DNA repair genes that may be involved in the pathogenesis of several tumor types.

Radiation-Associated Sarcomas are Characterized by Complex Karyotypes with Frequent Rearrangements of Chromosome Arm 3p

Ionizing radiation is a well-known risk factor for sarcoma development. To investigate whether radiation-associated sarcomas are characterized by chromosome aberrations that distinguish them from de novo sarcomas, we identified those patients in our series of more than 500 cytogenetically abnormal sarcomas that fulfilled the following criteria: (1) each patient should have been irradiated for another malignancy at least 3 years prior to the sarcoma diagnosis, and (2) the sarcoma should have developed within the field of radiation. Ten patients fulfilling these criteria could be retrieved (median age at sarcoma diagnosis was 55 years, range 17-79; median latency period between primary tumor and radiation-associated sarcoma was 9 years, range 4-30). The diagnoses were typical for radiation-associated sarcomas: 2 each of malignant fibrous histiocytoma, leiomyosarcoma, and pleomorphic sarcoma, and 1 each of osteosarcoma, fibrosarcoma, myxofibrosarcoma, and spindle cell sarcoma. All 10 cases had relatively complex karyotypes with multiple, mostly unbalanced, structural rearrangements, similar to what has been reported in de novo sarcomas of the corresponding histologic subtypes. The only cytogenetic features that were unusually frequent among the radiation-associated sarcomas were the finding of unrelated clones in 3 cases, and loss of material from chromosome arm 3p, in particular 3p21-3pter, in 8 cases. Loss of the same chromosome segment has been described in 4 of the 8 previously published cases of radiation-associated sarcomas that have been analyzed after short-term culturing, which makes this imbalance significantly (P < 0.001) more frequent among radiation-associated sarcomas (12 of 18 cases) than among unselected cases of the corresponding histologic subtypes (74 of 282 cases). In contrast to the cytogenetic results, no 3p deletions were detected among the 6 cases of the present series that could be analyzed by comparative genomic hybridization (CGH). The most frequent imbalance detected by CGH was gain of 15cen-q15 (3 cases), followed by loss of chromosome 13 and gain of 5p, and 7cen-q22, each detected in 2 cases.

Comparative genomic hybridization in childhood acute lymphoblastic leukemia

DNA copy number changes were studied by comparative genomic hybridization (CGH) on bone marrow samples obtained from 72 patients with childhood acute lymphoblastic leukemia (ALL) at diagnosis. The patients had been admitted to the Helsinki University Central Hospital (Finland) between 1982 and 1997. CGH showed DNA copy number changes in 45 patients (62.5%) with a mean of 4.6 aberrations per patient (range, 1 to 22). The results of CGH and chromosome banding analysis were generally concordant, but CGH facilitated specific karyotyping in 34 cases. DNA copy number gains were more frequent than losses (gains:losses, 6:1). Gains of DNA sequences affected almost exclusively whole chromosomes and were most commonly observed in chromosomes 21 (25%), 18 (22.2%), X (19.4%), 10 (19.4%) and 17 (19.4%). The most common partial gain was 1q31-q32 (8.3%). The most common gains of chromosomes 21, 18, X, 10, 17, 14, 4, 6 and 8 appeared concurrently. High-level amplifications of small chromosome regions were sporadic, detected only in two patients (2.8%). Chromosome 21 was involved in both cases. The most common losses were 9p22-pter (12.5%) and 12p13-pter (11.1%). No statistically significant association between the CGH findings and the diagnostic white blood cell count was observed.

FGF4 and INT2 oncogenes are amplified and expressed in Kaposi's sarcoma.

Kaposis sarcoma (KS) is a vascular tumor, the pathogenesis of which has been suggested to include human herpesvirus 8 (HHV-8) as well as various cytokines and growth factors. Very little is known about cytogenetic and molecular genetic changes in KS. We studied DNA copy number changes in KS and found a recurrent gain at 11q13. We then analyzed the amplification and expression status of two known oncogenes, FGF4 and INT2, residing at 11q13. Comparative genomic hybridization, interphase fluorescence in situ hybridization with yeast artificial chromosome probes containing FGF4 and INT2, and immunoperoxidase immunostaining with anti-FGF4 and -INT2 antibodies were used on 12 KS samples. All samples tested were shown by polymerase chain reaction to be HHV-8 positive. A recurrent gain at 11q13 was shown by comparative genomic hybridization in 4 of 10 cases studied. Of six cases studied by interphase fluorescence in situ hybridization, four showed a 3- to 4-fold amplification with the probes containing FGF4 and INT2. Expression of FGF4 and INT2 was found in nine and three cases, respectively, of nine studied. Amplification and expression of these genes is particularly interesting in the context of oncovirus involvement, because INT2 is a homolog of mouse int2, which causes mammary carcinoma in mice when activated by integration of retrovirus mouse mammary tumor virus. This raises the question of whether HHV-8 represents an integrating oncovirus that causes amplification and activation of genomic oncogenes in humans.

Genetic Toxicological Profile of Carbofuran and Pirimicarb Carbamic Insecticides

It’s well known that the pesticide usages in agriculture have led increase in food production worldwide. Although the benefits of conventional agricultural practices have been immense, they utilize levels of pesticides and fertilizers that can result in a negative impact on the environment (WHO, 1988). Only for the 2006-2007, the total world pesticide amount employed was approximately 5.2 billion pounds (www.epa.gov). Their application is still the most effective and accepted method for the plant and animal protection from a large number of pests, being the environment consequently and inevitably exposed to these chemicals. Herbicides accounted for the largest portion of total use, followed by other pesticides, like insecticides and fungicides (www.epa.gov). The goal in pesticide investigation and development is identifying the specificity of action of a pesticide toward the organisms it is supposed to kill (Cantelli-Forti et al., 1993). Only the target organisms should be affected by the application of the product. However, because pesticides are designed and selected for their biological activity, toxicity on non-target organisms frequently remains a significant potential risk (Cantelli-Forti et al., 1993). The benefits in using pesticides must be weighed against their deleterious effects on human health, biological interactions with non-target organisms, pesticide resistance and/or accumulation of these chemicals in the environment (WHO, 1988). Pesticides are high volume, widely used environmental chemicals and there is continuous debate concerning their probable role in both acute and chronic human health effects (Cantelli-Forti et al., 1993; Hodgson & Levi, 1996). Among the potential risk effects of agricultural chemicals, carcinogenesis is of special concern. The genetic toxicities of pesticides have been determined by numerous factors like their biological accumulation or degradation in the environment, their metabolism in humans, and their action in cellular components such as DNA, RNA and proteins (Shirasu, 1975). It seems essential the determination of the genotoxic risks of these pesticides before they are used in agriculture. Therefore, the carcinogenic and mutagenic potential of a large amount of pesticides has been the object of an extensive and wide investigation (WHO, 1990). These results have great predictive value for the carcinogenicity of several pesticides (IARC, 1987). The International Agency for Research on Cancer (IARC) has reviewed the potential carcinogenicity of a wide range of insecticides, fungicides, herbicides and other similar compounds. Fifty-six pesticides have been classified with carcinogenic potential in different laboratory animals (IARC, 2003). Among them, and as a brief example, chemicals compounds as phenoxy acid herbicides, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), lindane,

Herbicides in Argentina. Comparative Evaluation of the Genotoxic and Cytotoxic Effects on Mammalian Cells Exerted by Auxinic Members

In epidemiological and in experimental biology studies, the existence of an increasing interest in biomonitoring markers to achieve both a measurement and an estimation of biologically active/passive exposure to genotoxic pollutants, is nowadays a real fact. Significant contributions to the advancement of pesticide toxicology came and continue to come from many sources, e.g., academic, governmental/regulatory, and industrial. Regulatory agencies, private sector, and academia worldwide combine expertise to assess pesticide safety and risk potential demanding adequate data of high quality to serve as the basis for establishing safe exposure levels. The extent of testing was and is often determined by the depth of the science, as well as the chemical and physical properties of the agent and the extent of exposure. The importance of pesticide toxicology has evolved from listing poisons to protecting the public from the adverse effects of chemicals, from simply identifying effects (qualitative toxicology), to identifying and quantifying human risks from exposure (quantitative toxicology), and from observing phenomena to experimenting and determining mechanisms of action of pesticide agents and rational management for intoxication. Humans and living species may, therefore, be exposed to a number of different chemicals through dietary and other routes of exposure. Nonetheless, there continues to be concern that the presence of multiple chemical residues in foods may cause adverse health side effects, including effects that would not be predicted from consideration of single exposures to individual compounds. It is known that the regulatory system for pesticide products found in foods does not routinely address the toxic effects of different substances in combination. The implications, both for risk assessment and for approval processes, of exposure to mixtures of pesticides are among the topics examined by different international agencies, e.g., World Health Organization (WHO, www.who.int), International Agency for Research on Cancer (IARC, www.iarc.fr), United States Environmental Protection Agency (EPA, www.epa.gov), European Chemicals Agency (ECHA, www.echa.auropa.eu), Health Canada Pest Management Regulatory Agency (PMRA, www.pmra-arla.gc.ca), among others. These international agencies, particularly WHO and EPA, have contributed a great deal in their attempts to control pesticide poisoning. They continue their efforts, with particular emphasis on safety in the use of

Chapter 18. Hypsiboas pulchellus (Anura, Hylidae) Tadpoles, a Novel Amphibian Experimental Model in Aquatic Pollution Research

Amphibians as animal models have long been employed as indicators of environmental quality and to detect toxicity risks of environmental pollutants. The increased attention to the use of non-traditional species of amphibians in ecotoxicology and genotoxicology research lies in their ability not only to reveal the toxic and genotoxic effects of many potential environmental xenobiotics, but also to help researchers understand the behaviour of real ecosystems. This chapter presents an overview of selected research that has led to the use of the common tree frog Hypsiboas pulchellus as a reliable and valid model in in vivo and in situ studies of aquatic pollution.

Characterization of the 17p amplicon in human sarcomas — microsatellite marker analysis

The structure of the 17p amplicon from 9 human sarcoma specimens evaluated by comparative genomic hybridization (CGH) has been studied by analyzing 28 microsatellite markers by PCR. Eleven sarcoma specimens showing no DNA copy number increases at 17p by CGH were analyzed as control samples. Five specimens were analyzed by Southern blotting using probes that have previously shown amplification at the 17p12 region in astrocytoma and high-grade osteosarcoma samples. Microsatellite marker analyses revealed that all samples but 1 showing copy number increases at 17p by CGH displayed allelic imbalance that confirmed the CGH findings. Seven of these 9 cases displayed gain in copy number by microsatellite marker analysis. Four cases displaying gain in copy number were associated with loss of heterozygosity at other loci. Southern blot analysis showed amplification in 3 cases, all of them had shown copy number increases by CGH and microsatellite marker analysis, except one case, which was not included in the microsatellite marker analysis. Our results reveal the complexity of the 17p amplicon in sarcomas, suggesting that multiple target genes are involved in tumorigenesis.