What causes brain cancer?

Glioblastoma is the most common and most lethal form of brain tumor in people. Research published in the International Journal of Computational Biology and Drug Design offers a novel way to determine what biological functions go awry when the tumor first begins to form. Understanding the problems at the molecular level might one day reveal the underlying mechanism of carcinogenesis in glioblastoma and ultimately lead to treatments or even preventative measures.

This form of brain tumor account for more than half of all cases in which the tumor is within the tissues of the brain and a fifth of cases in which a tumor is present within the skull.

Zhongming Zhao and colleagues at Vanderbilt University, in Tennessee, explain how problems that occur during the transcription of the genetic code for making proteins may play a role in the formation of a glioblastoma. These might arise through changes in the genetic materials itself or alterations to the molecules involved in regulating the transcription process. In their latest research, the team has tested the possibility that microRNAs (miRNAs) and transcription factors (TFs) might somehow regulate the genes glioblastoma. With this in mind, the researchers carried out a computer search of appropriate databases to uncover any links between these components of the genetic machinery and glioblastoma.

Although cancer exists in many different forms and is not a single disease but a complex array of different diseases, there are certain characteristics that define the different forms: self-sufficiency in growth signals, insensitivity to antigrowth signals, evading programmed cell death, limitless replicative potential of cells, sustained blood-vessel growth, evasion of the immune system, tissue invasion and spreading through the body in metastasis. Insights into these processes at the molecular level is now possible thanks to the advent of vast databases of genomic and biochemical information related to different types of cancer.

The Vanderbilt team has now searched three databases miR2Disease, HMDD (human miRNA-associated disease database) and PhenomiR, to find regulatory networks specific to glioblastoma. To do so they integrated data on glioblastoma-related miRNAs, TFs and genes. They utilized a well-known target-prediction tool, TargetScan, to trawl the databases and identified 54 so-called feed-forward loops (FFLs), these are molecular control systems involved in transcription and the required signaling processes. Follow up work revealed these FFLs to have functions important to carcinogenesis as well as unique functions specific to each FFL.

“Our work provided data for future investigation of the mechanisms underlying glioblastoma and also potential regulatory subunits that might be useful for biomarker discovery and therapy targets for glioblastoma,” the team concludes.

Gong, X., Sun, J., & Zhao, Z. (2011). Gene regulation in glioblastoma: a combinatorial analysis of microRNAs and transcription factors International Journal of Computational Biology and Drug Design, 4 (2) DOI: 10.1504/IJCBDD.2011.041006

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Black hole

The European Southern Observatory’s Very Large Telescope (VLT) has helped an international team of astronomers to detect a stellar mass black hole that lies at a much greater distance from Earth than any observed before. The black hole is in the spiral galaxy NGC 300, about six million light years away in the constellation Sculptor.

The spiral galaxy NGC 300 lying in the constellation Sculptor (Credit: Galex/NASA)
The spiral galaxy NGC 300 lying in the constellation Sculptor (Credit: Galex/NASA)

Paul Crowther and Vik Dhillon, of the University of Sheffield, UK, Robin Barnard and Simon Clark of the The Open University, Milton Keynes, UK, and Stefania Carpano and Andy Pollock of ESAC, in Madrid, Spain report the black hole which has a mass of about twenty times that of the Sun in the Monthly Notices of the Royal Astronomical Society.

The stellar-mass black holes found in our Milky Way galaxy commonly weigh up to ten times the mass of the Sun. The newly discovered black hole is not only the most distant, but the second most massive stellar-mass black hole ever found. It is also entwined with a star that will soon become a black hole itself.

Lead author Crowther, explains: “This is the most distant stellar-mass black hole ever weighed, and it’s the first one we’ve seen outside our own galactic neighbourhood, the Local Group. The black hole’s curious partner is a Wolf-Rayet star, which also has a mass of about twenty times as much as the Sun. Wolf-Rayet stars are near the end of their lives and expel most of their outer layers into their surroundings before exploding as supernovae, with their cores imploding to form black holes.

An artist's impression of the newly discovered black hole and its stellar companion (Credit: ESO/L. Calçada)
An artist's impression of the newly discovered black hole and its stellar companion (Credit: ESO/L. Calçada)

In less than a million years, a blink of the eye cosmologically speaking, the Wolf-Rayet star will explode as a supernova and its remnants collapse into a black hole. Only one other system of this type has previously been seen, but other systems comprising a black hole and a companion star are not unknown to astronomy. The existence of such systems hints at an underlying galactic chemistry. Astronomers believe that a higher concentration of heavy chemical elements influences how a massive star evolves, increasing how much matter it sheds, resulting in a smaller black hole when the remnant finally collapses.


Monthly Notices Royal Astronom Soc, 2010, in press

Paul Crowther