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Posts Tagged ‘HIF’

Whitley Hypoxystation

Hypoxia and the Hallmarks of Cancer: Metabolic Reprogramming

Hanahan and Weinberg’s seminal papers on the Hallmarks of Cancer describe how cancer cells accommodate the frenzied growth characteristic of tumours. Low oxygen is eminently characteristic of tumours, and in this hypoxic environment, metabolism is reprogrammed to satisfy energetic and synthetic needs of the cells.

 

Our series on Hypoxia and the Hallmarks of Cancer has showcased research on how hypoxia in the tumour microenvironment affects 8 of the Hallmarks, and in the fifth and final chapter, we look more closely at how researchers are using the Hypoxystation to delineate the Hallmark Metabolic Reprogramming.

The Hypoxystation creates authentic cell culture conditions with regard to oxygen, CO2, temperature, and humidity.  Glove-less access to culture and manipulate cells under physiological atmosphere, in a HEPA-clean environment, allows cancer researchers to re-create the hypoxic tumour microenvironment. Hypoxystation user Dr Ali Tavassolli states that “We have only ever used the H35. I like the ease with which we can regulate and change the oxygen concentration”. And our user Dr. Brad Wouters at the Princess Margaret Cancer Centre in Toronto, who recently purchased his fourth Hypoxystation, says, “The continuous hypoxia we achieve in the workstation is a prerequisite for studies with hypoxia-activated drugs used in cancer therapy strategies.”

Hallmarks of Cancer

Metabolic Reprogramming

Changes in energy metabolism feature prominently in aggressive malignancy, and tumour hypoxia and the responding signalling pathways, featuring many HIF target genes, clearly interface with reprogrammed tumour metabolism. Reprogramming of conventional metabolic pathways serves to satisfy burgeoning energetic and anabolic needs of the tumour cells; many cancer cells may preferentially utilise glycolysis over oxidative phosphorylation, uncoupling mitochondrial metabolism from oxygen availability. Hypoxia-induced HIF’s attenuate mitochondrial function through diverse mechanisms, including down-regulation of enzymes in the electron transport chain and suppression of biogenesis of mitochondria. Signalling pathways involving HIF’s and many products of oncogenes and tumour suppressor genes interact to balance the energy needs of dividing cells with the requirement for bio-synthetic intermediates. Activation of lipid biosynthesis and other pathways with biosynthetic significance, such as the pentose phosphate pathway, is another metabolic consequence of hypoxia and HIF up-regulation. Reactive oxygen species ROS produced by the mitochondria stabilise HIF-1, influence redox homeostasis, and provide protective antioxidants to the cancer cells.

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KONICA MINOLTA DIGITAL CAMERA

Culturing Cells in Ambient Air is Far From Physiological

Based on the premise that the physiological range of oxygen in tissues is between 1- 8%, and pathologies from cancer to diabetes are characterised by much lower oxygen levels, researchers worldwide are cultivating their cell cultures in the Hypoxystation by Don Whitley Scientific. The Hypoxystation provides physiologically relevant conditions for cell culture and manipulation to ensure authentic behaviour of cells. User-defined parameters for temperature, CO2, O2 and humidity, plus the workstation format, where cells reside throughout the entire duration of the assays, minimise the extra-physiologic oxygen shock that is known to negatively impact cell metabolism and growth.

Numerous recent publications by our Hypoxystation users demonstrate that cell culture conditions which mimic physioxia, are essential in avoiding the significantly impaired growth rates, reduced lifespan, and altered molecular behaviour encountered in cells cultivated at ambient conditions. Oxygen levels in tissues are in constant flux; they change in response to functional status and blood delivery in the organs, and this too can be re-created in the Hypoxystation through programmed oxygen profiling.

Recent research using the Hypoxystation to investigate hypoxia inducible factors and the array of signalling pathways that regulate angiogenesis, metabolism, redox homeostasis, inflammation, and cell death, and the many other processes which enable the cellular and organismal response to hypoxia, “highlights the importance of oxygen as a cell culture parameter when making physiological inferences” (Timpano and Uniacke, 2016).

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From: Burr et al. (2016) “Mitochondrial Protein Lipoylation and the 2-Oxoglutarate Dehydrogenase Complex Controls HIF1a Stability in Aerobic Conditions” Cell Metabolism 25, 740–752


To find out more about Hypoxystations or other DWS products, please call +44 (0) 1274 595728 or email sales@dwscientific.co.uk


 

Clostridium difficile studies can be done in a Whitley Workstation

Hallmarks of Cancer: Sustaining Growth and Resisting Cell Death

In part four of our mini-series describing “Hypoxia and the Hallmarks of Cancer”, we look more closely at how researchers are using the Hypoxystation to delineate the Hallmarks Sustaining Growth and Resisting Cell Death.

 

 

 

 

 

Hallmarks of Cancer

Resisting Cell Death

The ability of cells to resist cell death under hypoxic conditions is central to the progression of cancer and the acquisition of resistance to chemotherapy so frequently encountered in tumors. Hypoxia in the tumor microenvironment exerts selective pressure favoring cells that have lost the functionality of apoptosis genes and can expand uncontrollably.  Hypoxia also contributes to survival by inducing autophagy, in a pathway involving HIF-1, beclin, BNIP3 and BNIP3L, in which cellular autophagy acts to recycle cellular organelles, satisfy metabolic demand and improve hypoxic tolerance.  HIF-1 mediates cell-cycle retardation and arrest, causing hypoxic tumor cells to become resistant to radiotherapies. NF-κB, through its effects on myriad transcription factors, for example through inhibition of cell death signalling, is activated by hypoxia and reactive oxygen species, and also promotes cell survival.

Sustaining Growth

Cancer is essentially based on the cells’ inability to “stop” when suppressors signal an end to growth, and the compunction to “go” despite a lack of bonafide growth signals. Hypoxia in the context of cancer, in precipitating genomic instability and mutation, results in numerous inactive tumor suppressor genes and activated growth factor genes, such that the combination of constitutive proliferative signaling and mutated cancer genes leads to sustained growth. HIF and NF-κB regulated pathways involving Notch, mTOR, WNT11, CAIX, and IGF-1, among many others, contribute to sustained growth in cancer as regulation of proliferation derails. Induced by hypoxia-regulated proteins, anabolic pathways for nucleotide and lipid synthesis are ramped up and enable the rapid proliferation typical of cancer.

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