Cloning of a non-c-myc DNA fragment from the double minutes of a human colon carcinoid cell line

Carcinoid Syndrome: Preclinical Models and Future Therapeutic Strategies

Carcinoid syndrome represents a debilitating paraneoplastic disease, caused by the secretion of several substances, occurring in about 10-40% of patients with well-differentiated neuroendocrine tumors (NETs). The main signs and symptoms associated with carcinoid syndrome are flushing, diarrhea, hypotension, tachycardia, bronchoconstriction, venous telangiectasia, dyspnea and fibrotic complications (mesenteric and retroperitoneal fibrosis, and carcinoid heart disease). Although there are several drugs available for the treatment of carcinoid syndrome, the lack of therapeutic response, poor tolerance or resistance to drugs are often reported. Preclinical models are indispensable tools for investigating the pathogenesis, mechanisms for tumor progression and new therapeutic approaches for cancer. This paper provides a state-of-the-art overview of in vitro and in vivo models in NETs with carcinoid syndrome, highlighting the future developments and therapeutic approaches in this field.

Double minutes, cytogenetic equivalents of gene amplification, in human neoplasia - a review

Double minutes are tiny spherical chromatin bodies of a few mega-base pairs of size which are found occasionally in hematopoietic neoplasia and more or less often in human solid tumors. They have been associated with worse prognosis and poor outcome of the malignancies where present. With the beginning era of molecular cytogenetics they could be defined as cytogenetic equivalents of amplified DNA sequences. The identification of involved chromosomal segments and their molecular nature led to the development of molecular genetic techniques for a rapid and reliable detection of prognostically important oncogene amplifications in human tumors and,as a consequence, to gene-targeted therapy.

Interspecific hybridization induced amplification of Mdm2 on double minutes in a Mus hybrid

We report a case of interspecific hybridization induced amplification of Chromosome 10 on double minutes (dm) in the karyotype of a hybrid Mus embryo. Stable, non-mosaic dm were previously found in tissues of a 16.5-day Mus Musculus x Mus Caroli hybrid (Graves, 1984). Dm in tissues of the hybrid was of interest to us because of previous reports of genomic instability in interspecific hybrids (O'Neill et al., 1998) and thus we decided to characterize the dm in the hybrid karyotypes. Whole chromosome painting of the hybrid cell lines showed amplification of Chromosome 10 sequences. Southern analysis with a probe for the candidate gene Mdm2 showed amplification of the paternal allele of this oncogene. Overexpression of Mdm2 was confirmed by a western analysis that also showed an associated inactivation of the tumor suppressor, Trp53. Evidence indicates that the event leading to the instability observed was an early adaptive response to stress on the genome, i.e. interspecific hybridization.

Karyotypic evolution of cells in culture: a new concept

The Chapter summarizes peculiarities of karyotypic variability during establishment and long-term cultivation of permanent cell lines. A new concept on pathways of karyotypic evolution of cells in culture is put forward. A detailed description is presented of the author's original approach of cytogenetic analysis of cell lines provided for a principally new characteristic of the cell line: its generalized reconstructed karyotype (GRK). Its use as a criterion to evaluate authenticity, purity, and stability of cell lines is discussed. Based on analysis of the GRK, two stages of karyotype evolution of cell lines are revealed: establishment and stabilization, different in karyotypic variability of the cell population and in peculiarities of clone selection. Comparison of peculiarities of karyotypic variability of leukemic and tumor cells both in vitro and in vivo was made, and general regularities of their karyotypic evolution have been established, such as nonrandom changes in the number and structure of chromosomes and deletion of one of the sex chromosomes, as well as regularities characteristic only of cells in culture in most human and animal cell lines (at least 85%) of disomy on all autosomes. The rest of the cell lines, 15%, are characterized by either partial or total monosomies on certain autosomes during long-term cultivation. Three main compensatory mechanisms of maintaining viability of cell lines that have lost genetic material are discussed: polyploidization of the initial cell clone, amplification of oncogenes (predominantly of mys family), and extracopying of whole autosomes or of their fragments.

Cytogenetic triclonality in acute myeloid leukemia: a morphologic, immunologic and in situ hybridization study

Cytogenetically unrelated clones are uncommon in hematologic malignancies. We report a case of acute myeloid leukemia, which consisted morphologically of two populations of small and large blasts demonstrating immunophenotypic heterogeneity. Cytogenetic analysis showed 3 karyotypically abnormal clones: 47,XY, +14/45,XY,dic(5;17)(q11;p11),14dmin, and a near-tetraploid clone. In situ hybridization showed that the near-tetraploid clone corresponded to the large blasts, and the near-diploid clones the small blasts, therefore demonstrating a direct relationship between cell size and DNA content. The diverse morphologic, immunologic and cytogenetic heterogeneity observed in our case suggested hematopoietic oligoclonality.

Novel DNA sequences at chromosome 10q26 are amplified in human gastric carcinoma cell lines: molecular cloning by competitive DNA reassociation

Molecular cloning of genomic sequences altered in cancer cells is believed to lead to the identification of new genes involved in the initiation and progression of the malignant phenotype. DNA amplification is a frequent molecular alteration in tumor cells, and is a mode of proto-oncogene activation. The cytologic manifestation of this phenomenon is the appearance of chromosomal homogeneously staining regions (HSRs) or double minute bodies (DMs). The gastric carcinoma cell line KATO III is characterized by a large HSR on chromosome 11. In-gel renaturation analysis confirmed the amplification of DNA sequences in this cell line, yet none of 42 proto-oncogenes that we tested is amplified in KATO III DNA. We employed the phenol-enhanced reassociation technique (PERT) to isolate 21 random DNA fragments from the amplified domain, and used 6 of them to further clone some 150 kb from that genomic region. While in situ hybridization performed with some of these sequences indicated that in KATO III they are indeed amplified within the HSR on chromosome 11, somatic cell hybrid analysis and in situ hybridization to normal lymphocyte chromosomes showed that they are derived from chromosome 10, band q26. The same sequences were found to be amplified in another gastric carcinoma cell line, SNU-16, which contains DMs, but were not amplified in other 70 cell lines representing a wide variety of human neoplasms. One of these sequences was highly expressed in both KATO III and SNU-16. Thus, the cloned sequences supply a starting point for identification of novel genes which might be involved in the pathogenesis of gastric cancers, and are located in a relatively unexplored domain of the human genome.

In vitro culture of neuroendocrine tumors of the pancreas and gut

Long-time culturing of neuroendocrine tumors from gut and pancreas obtained by surgery was performed with the addition of different growth factors, such as nerve growth factor (NGF), fibroblast growth factor (FGF) and platelet derived growth factor (PDGF) to Hite's medium. Furthermore, the cells were also cultured on epithelial cell matrix (ECM) coated flasks with or without 5% fetal calf serum (FCS) supplemented to the medium. In ECM coated flasks the cells displayed a flattened, non-overlapping pattern and sometimes glandular formation. On the addition of 5% FCS to the culture medium single cells often appeared in cord-like pattern. Culturing in uncoated flasks led to free floating cell colonies or cell clusters attached to fibroblasts present. When different growth factors were added to tumor cells in uncoated culture flasks, no morphological difference could be noticed between the experiments. The tumor cells aggregated to big cell colonies, free-floating in the medium. However, the addition of growth factors to the culture medium showed varying degrees of positive silver staining in cultured tumor cells, while cells cultured in Hite's medium only, with or without FCS supplemented, were negative. The result might indicate that the cells cultured with growth factors retained their endocrine differentiation even after long-term culture. This observation correlated to positive immunostaining to chromogranin A and synaptophysin. Different growth factors might stimulate different fractions of tumor cells to retain the endocrine characteristics.