The role of DNA damage and repair in liver cancer.

Hepatocellular carcinoma is rapidly becoming a major cause of global mortality due to the ever-increasing prevalence of obesity. DNA damage is known to play an important role in cancer initiation, however DNA repair systems are also vital for the survival of cancer cells. Given the function of the liver and its exposure to the gut, it is likely that DNA damage and repair would be of particular importance in hepatocellular carcinoma. However, many contemporary reports have neglected the role of individual pathways of DNA damage and repair in their hypotheses. This review, therefore, aims to provide a concise overview for researchers in the field of liver cancer to understand the pathways of DNA damage and repair and their individual roles in hepatocellular carcinoma.

Retrospective review of CT-guided intervertebral disc biopsies performed at a tertiary referral centre for suspected osteodiscitis.

INTRODUCTION: Patients with osteodiscitis are often prescribed antibiotics prior to biopsy. There is controversy in the literature about whether antibiotic pre-treatment prior to CT-guided biopsy decreases the microbiological culture yield. Conclusions from previous studies are influenced by sample size error and selection bias. Our study, conducted in a large number of patients over a 10-year period, clarifies this issue so that best clinical practice is assured. METHODS: We performed a retrospective audit of the clinical, radiological and microbiological features of adult patients who underwent CT-guided biopsies for suspected osteodiscitis at a tertiary institution. Patients who had received intravenous antibiotic therapy in the month prior to biopsy or oral antibiotics 2 weeks prior to biopsy were considered as having had antecedent treatment. RESULTS: We initially found no significant difference in the likelihood of a positive culture between patients who had received antecedent treatment and those who had not. However, when we performed a subgroup analysis, we found that using multiple antibiotics influenced the likelihood of a positive culture. A second subgroup analysis demonstrated that pre-treatment reduced the likelihood of a positive culture. This discrepancy arose from the match between the antecedent antibiotics and the organisms' antibiotic sensitivity profile. CONCLUSION: Antibiotic treatment preceding CT-guided biopsy reduces the likelihood of a positive microbiological culture results. However, due to the often poor match, between the pre-treatment antibiotic and the organisms' antibiotic sensitivity profile, this is often not clinically apparent. Furthermore, positive cultures sensitive to the pre-treatment antibiotics can still be obtained.

Gene-environment interaction demonstrates the vulnerability of the embryonic heart.

Mammalian embryos develop in a low oxygen environment. The transcription factor hypoxia inducible factor 1a (HIF1α) is a key element in the cellular response to hypoxia. Complete deletion of Hif1α from the mouse conceptus causes extensive placental, vascular and heart defects, resulting in embryonic lethality. However the precise role of Hif1α in each of these organ systems remains unknown. To further investigate, we conditionally-deleted Hif1α from mesoderm, vasculature and heart individually. Surprisingly, deletion from these tissues did not recapitulate the same severe heart phenotype or embryonic lethality. Placental insufficiency, such as occurs in the complete Hif1α null, results in elevated cellular hypoxia in mouse embryos. We hypothesized that subjecting the Hif1α conditional null embryos to increased hypoxic stress might exacerbate the effects of tissue-specific Hif1α deletion. We tested this hypothesis using a model system mimicking placental insufficiency. We found that the majority of embryos lacking Hif1α in the heart died when exposed to non-physiological hypoxia. This was a heart-specific phenomenon, as HIF1α protein accumulated predominantly in the myocardium of hypoxia-stressed embryos. Our study demonstrates the vulnerability of the heart to lowered oxygen levels, and that under such conditions of non-physiological hypoxia the embryo absolutely requires Hif1α to continue normal development. Importantly, these findings extend our understanding of the roles of Hif1α in cardiovascular development.

Loss of Cited2 causes congenital heart disease by perturbing left-right patterning of the body axis.

Cited2 is a transcriptional coactivator that is required for normal development of the embryo and placenta. Cited2-null mice die during gestation with fully penetrant heart defects and partially penetrant laterality defects. The laterality defects occur due to the loss of Nodal expression in the left lateral plate mesoderm (LPM). The cause of the heart defects that arise independently of laterality defects is unknown; they might occur due to an intrinsic requirement for Cited2 in the developing heart, or to disturbances in left-right patterning of the early embryo. Herein it is established that deletion of Cited2 from the heart progenitors does not alter development, and that heart defects in Cited2-null embryos arise due to an extra-cardiac requirement for Cited2 in establishing the left-right body axis. In addition, we provide evidence supporting a role for Cited2 in tissues of the embryo vital for left-right patterning (the node and LPM). Molecular and genetic analysis reveals that Cited2 is required for the initiation, but not propagation of, the left-sided determinant Nodal in the LPM. Moreover, a new role for Cited2 is identified as a potentiator of bone morphogenetic protein (BMP) signalling, counteracting the initiation of Nodal expression in the LPM. These data define Cited2 as a key regulator of left-right patterning in the mammalian embryo, and reveal that the role of Cited2 in cardiac development lies in its extra-cardiac functions. The clinical relevance of these findings lies in the fact that heterozygous mutation of human CITED2 is associated with congenital heart disease and laterality defects.

Cited2 is required both for heart morphogenesis and establishment of the left-right axis in mouse development.

Establishment of the left-right axis is a fundamental process of vertebrate embryogenesis. Failure to develop left-right asymmetry leads to incorrect positioning and morphogenesis of numerous internal organs, and is proposed to underlie the etiology of several common cardiac malformations. The transcriptional modulator Cited2 is essential for embryonic development: Cited2-null embryos die during gestation with profound developmental abnormalities, including cardiac malformations, exencephaly and adrenal agenesis. Cited2 is also required for normal establishment of the left-right axis; we demonstrate that abnormal heart looping and right atrial and pulmonary isomerism are consistent features of the left-right-patterning defect. We show by gene expression analysis that Cited2 acts upstream of Nodal, Lefty2 and Pitx2 in the lateral mesoderm, and of Lefty1 in the presumptive floor plate. Although abnormal left-right patterning has a major impact on the cardiac phenotype in Cited2-null embryos, laterality defects are only observed in a proportion of these embryos. We have therefore used a combination of high-resolution imaging and three-dimensional (3D) modeling to systematically document the full spectrum of Cited2-associated cardiac defects. Previous studies have focused on the role of Cited2 in cardiac neural crest cell development, as Cited2 can bind the transcription factor Tfap2, and thus affect the expression of Erbb3 in neural crest cells. However, we have identified Cited2-associated cardiac defects that cannot be explained by laterality or neural crest abnormalities. In particular, muscular ventricular septal defects and reduced cell density in the atrioventricular (AV) endocardial cushions are evident in Cited2-null embryos. As we found that Cited2 expression tightly correlated with these sites, we believe that Cited2 plays a direct role in development of the AV canal and cardiac septa. We therefore propose that, in addition to the previously described reduction of cardiac neural crest cells, two other distinct mechanisms contribute to the spectrum of complex cardiac defects in Cited2-null mice; disruption of normal left-right patterning and direct loss of Cited2 expression in cardiac tissues.