Hypoxia Strongly Affects Mitochondrial Ribosomal Proteins and Translocases, as Shown by Quantitative Proteomics of HeLa Cells.

Hypoxia is an important and common characteristic of many human tumors. It is a challenge clinically due to the correlation with poor prognosis and resistance to radiation and chemotherapy. Understanding the biochemical response to hypoxia would facilitate the development of novel therapeutics for cancer treatment. Here, we investigate alterations in gene expression in response to hypoxia by quantitative proteome analysis using stable isotope labeling with amino acids in cell culture (SILAC) in conjunction with LCMS/MS. Human HeLa cells were kept either in a hypoxic environment or under normoxic conditions. 125 proteins were found to be regulated, with maximum alteration of 18-fold. In particular, three clusters of differentially regulated proteins were identified, showing significant upregulation of glycolysis and downregulation of mitochondrial ribosomal proteins and translocases. This interaction is likely orchestrated by HIF-1. We also investigated the effect of hypoxia on the cell cycle, which shows accumulation in G1 and a prolonged S phase under these conditions. Implications. This work not only improves our understanding of the response to hypoxia, but also reveals proteins important for malignant progression, which may be targeted in future therapies.

Cell inactivation by combined low dose-rate irradiation and intermittent hypoxia.

PURPOSE: To investigate in detail the earlier observed combined effect of low dose-rate ß-irradiation delivered at a dose-rate of 15 mGy/h and continued intermittent hypoxia that leads to extensive cell death after approximately 3-6 weeks. MATERIAL AND METHODS: Continuous low dose-rate ß-irradiation at a dose rate of 15, 1.5 or 0.6 mGy/h was given by incorporation of [(3)H]-labelled valine into cellular protein. The cells were cultivated in an atmosphere with 4% O2 using an INVIVO2 hypoxia glove box. Clonogenic capacity, cell-cycle distribution and cellular respiration were monitored throughout the experiments. RESULTS: After 3-6 weeks most cells died in response to the combined treatment, giving a surviving fraction of only 1-2%. However, on continued cultivation a few cells survived and restarted proliferation as the cellular oxygen supply increased with the reduced cell number. Irradiating the T-47D cells grown in an atmosphere with 4% O2 at dose-rates 10 and 25 times lower than 15 mGy/h did not have a pronounced effect on the clonogenic capacity with surviving fractions of 60-80%. CONCLUSIONS: Treatment of T-47D cells with low dose-rate ß-irradiation leads to a specific effect on intermittent hypoxic cells, inactivating more than 98% of the cells in the population. Given improved oxygen conditions, the few surviving cells can restart their proliferation.

Alterations of monocarboxylate transporter densities during hypoxia in brain and breast tumour cells.

BACKGROUND: Tumour cells are characterized by aerobic glycolysis, which provides biomass for tumour proliferation and leads to extracellular acidification through efflux of lactate via monocarboxylate transporters (MCTs). Deficient and spasm-prone tumour vasculature causes variable hypoxia, which favours tumour cell survival and metastases. Brain metastases frequently occur in patients with advanced breast cancer.Effective treatment strategies are therefore needed against brain metastasis from breast carcinoma. MATERIAL AND METHODS: In order to identify differences in the capacity for lactate exchange, human T-47D breast cancer cells and human glioblastoma T98G cells were grown under 4 % or 20 % oxygen conditions and examined for MCT1, MCT2 and MCT4 expression on plasma membranes by quantitative post embedding immunogold electron microscopy. Whereas previous studies on MCT expression in tumours have recorded mRNA and protein levels in cell extracts, we examined concentrations of the proteins in the microvillous plasma membrane protrusions specialized for transmembrane transport. RESULTS: In normoxia, both tumour cell types highly expressed the low affinity transporter MCT4, which is thought to mainly mediate monocarboxylate efflux, while for high affinity transport the breast tumour cells preferentially expressed MCT1 and the brain tumour cells resembled brain neurons in expressing MCT2, rather than MCT1. The expressions of MCT1 and MCT4 were upregulated in hypoxic conditions in both breast and brain tumour cells. The expression of MCT2 also increased in hypoxic breast cancer cells, but decreased in hypoxic brain tumour cells. Quantitative immunoblots showed similar hypoxia induced changes in the protein levels. CONCLUSION: The differential expression and regulation of MCTs in the surface membranes of hypoxic and normoxic tumour cells of different types provide a foundation for innovation in tumour therapy through the selective targeting of MCTs. Selective inhibition of various MCTs could be an efficient way to quench an important energy source in both original breast tumour and metastatic cancer tissue in the brain.

[Congenital hyperinsulinism--diagnosis and treatment]. / Kongenit hyperinsulinisme--diagnostik og behandling.

Congenital hyperinsulinism (CHI) is a rare and heterogeneous disease with a challenging diagnostic process and a need of individualised treatment of each patient. In severe, neonatal or infant CHI, differentiation between the focal and diffuse form by rapid genetics, 18F-fluoro-L-dihydroxyphenylalanine positron emission tomography/computed tomography and peroperative microscopy of frozen section allows surgeons to resect the focal lesion instead of performing subtotal pancreatectomy. Milder CHI, sometimes difficult to diagnose, is treated conservatively. In spite of all improvements, cerebral complications are still frequently seen.

[Congenital hyperinsulinism--new causes and clinical variations]. / Kongenit hyperinsulinisme--nye årsager og kliniske variationer.

Congenital hyperinsulinism (CHI) is a heterogeneous disease with variable onset, non- or hypoketotic hypoglycaemia, onset from birth to adulthood and a persistent, intermittent, or transient course with possible later conversion to non-autoimmune diabetes. Giving insights to beta cell function, CHI mutations are now known in eight genes (ABCC8, KCNJ11, GLUD1, GCK, HADH, SLC16A1, HNF4A and UCP2). However, 40-50% of the patients are still genetically unexplained. CHI can be dominantly or recessively inherited or may occur de novo. A number of syndromes can be associated with CHI.