RESUMO
Aberrations of chromosome 13, including large-scale deletions and rearrangements, have been implicated in the development of a significant fraction of human hepatocellular carcinomas, suggesting that liver tumor suppressor genes may be located on this chromosome. In this study, we have employed a microcell hybrid-based model system to investigate the presence of liver tumor suppressor loci on human chromosome 13. The parental GN6TF rat liver epithelial tumor cells are highly tumorigenic in vivo and exhibit altered cellular morphology and growth characteristics in vitro. The GN6TF cells form tumors in 100% of syngeneic animals with short latency, are not contact inhibited or anchorage-dependent in cell culture, and do not express mRNAs for rat Rb1 and BRCA2. Microcell-mediated introduction of human chromosome 13 into the rat liver tumor cell line GN6TF resulted in the generation of clonal microcell hybrid (MCH) cell lines that differentially exhibited tumor suppression and/or alteration of other transformation-associated phenotypes in vitro. Two GN6TF-13neo MCH lines exhibited characteristics indicative of suppression by the human chromosome, including a normalized cellular morphology and growth pattern, loss of anchorage-independent growth potential, partial restoration of contact inhibition, reduction in tumorigenic potential in vivo, and dramatic elongation of tumor latency. In contrast, three GN6TF-13neo MCH cell lines were minimally affected by the introduction of the human chromosome and were nearly indistinguishable from the parental GN6TF tumor cells, exhibiting a highly aggressive tumorigenic phenotype in vivo. Both suppressed and non-suppressed GN6TF-13neo MCH cell lines express Rb1 and BRCA2 mRNA in vitro, and tumors derived from the non-suppressed GN6TF-13neo MCH cell lines continue to express Rb1 and BRCA2 mRNA in vitro, and express pRb in vivo. The results suggest that: i) human chromosome 13 contains a liver tumor suppressor locus, ii) expression of Rb1 and/or BRCA2 is insufficient to produce tumor suppression in this rat liver tumor cell line, and iii) that the human chromosome 13 liver tumor suppressor may represent a novel tumor suppressor gene, distinct from Rb1 and BRCA2.
Assuntos
Proteína BRCA2/fisiologia , Cromossomos Humanos Par 13/genética , Genes Supressores de Tumor , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patologia , Proteína do Retinoblastoma/fisiologia , Animais , Proteína BRCA2/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Células Híbridas/metabolismo , Células Híbridas/patologia , Hibridização in Situ Fluorescente , Metáfase/genética , Neoplasias/genética , Neoplasias/metabolismo , Mapeamento Físico do Cromossomo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Proteína do Retinoblastoma/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Células Tumorais CultivadasRESUMO
OBJECTIVE: To evaluate histamine release and selected physiologic variables during constant rate infusion (CRI) of morphine in dogs. ANIMALS: Five healthy, conscious, intact female dogs. MATERIAL AND METHODS: Using a Latin square, repeated-measures design, dogs were randomly assigned to three treatment groups to receive a 4-hour CRI of saline (SAL), or a loading dose of morphine at 0.3 mg kg(-1) (LM), or 0.6 mg kg(-1) (HM), followed by an infusion of 0.17 mg kg(-1) hour(-1) (LM) and 0.34 mg kg(-1) hour(-1) (HM) respectively. Dogs received each of the three treatments at intervals of at least 7 days. Plasma histamine concentration, skin flushing, edema and wheals, heart rate and rhythm and non-invasive arterial blood pressure were measured before the loading dose and at 1, 2, 5, 15, 30, 60, 120, 180 and 240 minutes during the CRI, or at the time of occurrence. RESULTS: The loading dose induced the highest histamine release in the HM group being statistically higher than the SAL group. The histamine release obtained in the LM group after the loading dose did not differ from SAL. During the infusion, plasma histamine levels were numerically higher in the LM group. Besides one dog that developed hypotension for 2 minutes after the loading dose in the HM group and one dog that showed occasional ventricular premature contractions during both morphine infusions, cardiovascular variables were similar among the three treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: Both doses of morphine induced variable histamine release with minimal adverse cardiovascular effects in these conscious, healthy dogs. The plasma histamine levels obtained may be associated with significant hemodynamic changes in patients with limited cardiovascular reserve and sympathetic nervous tone.