chromosome bridge

Switching off Cancers Diversity

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JCS paper

A defining feature in over 2/3rds of all solid tumours is the continual loss and gain of whole are small parts of chromosomes. This instability, or CIN for short, strongly implicated in tumour initiation, progression, chemoresistance and poor prognosis. CIN is created through failures during mitosis, whereby whole or parts of a chromosome are segregated incorrectly, thereby created daughter cells with unequal chromosome numbers. Consequently, understanding how mitosis is regulated is essential for uncovering the mechanisms allowing CIN to arise and drive cancer. In our recent publication, we discovered the mechanisms controlling the key regulatory pathway critical to ensuring cells exit mitosis correctly. At the centre of this pathway is a gene call MASTL (short for ‘Microtubule Associated Serine/Threonine Kinase-Like’). The primary function of MASTL is to ensure that the cellular breaks (the phosphatase PP2A), is turned off during mitosis so that the accelerator (Cdk1 kinase) can drive the cell into mitosis. Much like a car, having the accelerator and breaks on at the same time is a bad idea, unless you like the smell of burning rubber. To successfully exit mitosis, and to perfectly segregate chromosomes, the cell must take the foot off the accelerator and turn on the breaks. Because MASTL is the central regulator ensuring the breaks are coordinated with the accelerator, it is essential to understand how MASTL is controlled. To this end, we uncovered that MASTL must be rapidly turned off to allow cells to exit mitosis, and this inactivation is carried out by another cellular brake call PP1 phosphatase (Rogers et al, JCS 2016). Now that we have identified and mapped this novel mitotic exit switch, we hope to be able to shed new light on how CIN drives the initiation and evolution cancer. We believe that with further study we will be able to better predict patient response to chemotherapy, and also identify new ways to ‘switch off’ highly unstable tumours, thereby improving treatment for patients that currently have a very poor prognosis.

Image of Interphase HeLa cell stained for Actin (red), DNA (blue) and the co-localisation of MASTL and PP1 by Proximity Ligation Assay (PLA; green).
Credit: Sam Rogers and Cell Division Lab

 

Public Talk “Killing Cancer One Cell at a Time ” now on YouTube

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Here is a recent talk I gave to some members of the public at the Garvan Institute of Medical Research.

It is a very general and simple over-view of explaining 1) how cells in your body proliferate, 2) how this goes wrong in cancer, 3) the challenges we are facing in treating and killing cancer, and 4) most importantly how we hoping to improve current treatments in the near future.

A big thanks to all the fantastic Garvan Foundation Team who hosted, filmed, and edited the event.

Anti-Oxaidants and Cancer…A complicated story!

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There has been a bit of press lately suggesting that Antioxidants might actually be bad for cancer… not good as they are commonly promoted in the media.
IFLS has put together a great article on some of the reasons why antioxidants might not be such a great thing [Link].

In addition, we recently wrote a review article about how different ‘stresses’ including oxidation can affect mitosis, and cancer. We also came to a similar conclusion in our review,  that antioxidants were a complicated and not always benifical for treating cancer. One of the main reason we suggested this was due to the fact that many common antioxidants are part of the Flavonoid family. On the surface that sound great, but many Flavonoids also happen to potently inhibit cyclin dependent kinases (Cdks). Coincidentally, our other recent article in Cell Cycle, showed that partial inhibition of Cdk1 can dramatically disrupt mitosis and drive severe cytokinesis defects and polyploidy (see video below). These mitotic defects are the foundation of chromosome instability  (CIN), which is a hallmark of more aggressive cancer types, that are also resistant to most chemotherapies and treatments. In simple terms, there is a possibility that in some cases, taking large quantities of dietary Flavonoids (e.g red wine, dark chocolate etc) could drive the formation of more aggressive cancers. This is definitely an area that needs a lot more research, and as always make sure that you fully discuss any dietary and supplements with your oncologist.

 

This is what happens when a ‘fairly normal’ cancer cell is treated with low doses of a Cdk1 inhibitor.

Here is a picture of a polyploid cancer cell, which was produced by partially inhibiting Cdk1.

ImageJ=1.48f unit=micron

 

Our Latest Review Article “Stressing Mitosis to Death” is now online !

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Great news, our latest review article “Stressing Mitosis to Death” has been accepted for publication by Frontiers in Oncology. You can access the provisional pre-press version here.

The review is about how common stresses affect mitosis, and the impact these stresses can have on the blockbuster mitotic chemotherapy drug Taxol (paclitaxel)

Finally here is one of the beautiful figures drawn by our own Sam Rogers for the Review!  Hope you enjoy the read !

 

Fig. v4

Were the front cover feature image on this months issue of Cell Cycle !

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Some more good news to coincide with today’s official release of our manuscript, one of our images has been chosen to be the feature image on the front cover.

It’s a great honour, one that I am very proud of, and is the first time I have ever had a front cover !
You can view the current issue (Volume 13 – Issue 9 – May 1, 2014) here.

Or jump directly to our paper here

Front Cover 

FrontCoverCC13-9

 

Read the rest of this entry »

Cell Image of the Week – Mitotic Catastrophe

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Here is one of the images that we took using a Leica SP8 confocal microscope this week in the lab.
It is a 3D image of a HeLa cell that has completely stuffed up mitosis (undergone mitotic catastrophe). It has separated whole chromosomes randomly into 2 daughter cells instead of separating the two identical chromatids in two.

And here is an artistic version just for fun !

A brief Intro to Greatwall Kinase…The King of Mitosis

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Our favourite protein in the lab is Greatwall kinase. It was first discovered in 2004 to be critical for cell division in fruit flies (1,2) . The trail then went cold for a few years as to its exact function, but in 2009, while I was working as a post-doc in France, I was fortunate enough to be in the lab that uncovered its exciting mode of action. For cells to get into mitosis they must activate a key protein called cyclin dependent kinase 1 (Cdk1). I like to think of this as the accelerator in a car. So to get moving cells push on the gas!
And conversely to get out of mitosis you need to hit the brakes. These brakes are the phosphatases which reverse the action of kinases like Cdk1. That’s great but what is missing from this equation?
Well like any car it’s pretty useless without a driver to co-ordinate the accelerator and brakes. And this is where Greatwall (Gwl for short) comes in. It makes sure that when Cdk1 (accelerator) turns on that the breaks get turned off and vice versa (3,4). Without Gwl the cell gets into a lot of trouble very fast, which you can see in the image below. Here I depleted the human version of Gwl (a gene called MASTL) and watched what happened as cells tried to undergo mitosis (5). As you can see they don’t do a very good job… the result is cells fail to divide correctly, resulting in multiple defects and often cell death.

Gwl Figure

I hope you enjoyed part one of my feature on Gwl, and in part 2 I will into more details about this amazing and exciting new protein.

References:

1. Bettencourt-Dias, M. et al. Genome-wide survey of protein kinases required for cell cycle progression. Nature 432, 980–987 (2004).

2. Yu, J. et al. Greatwall kinase: a nuclear protein required for proper chromosome condensation and mitotic progression in Drosophila. J Cell Biol 164, 487–492 (2004). [Link]

3. Vigneron, S. et al. Greatwall maintains mitosis through regulation of PP2A. EMBO J 28, 2786–2793 (2009). [Link]

4. Lorca, T. et al. Constant regulation of both the MPF amplification loop and the Greatwall-PP2A pathway is required for metaphase II arrest and correct entry into the first embryonic cell cycle. J Cell Sci 123, 2281–2291 (2010). [Link]

5. Burgess, A. et al. Loss of human Greatwall results in G2 arrest and multiple mitotic defects due to deregulation of the cyclin B-Cdc2/PP2A balance. Proc Natl Acad Sci USA 107, 12564–12569 (2010). [Link]

Mitotic Control Lab now has a Redbubble Store

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For a bit of fun way for us to show our research to the public, we have opened up a Redbubble store with some great Mitotic themed items inspired by the research that we do.  100% of any profits made will be used to directly fund further research (and or coffee) to keep us awake so that we can do more research. You can find a great selection of items including T-shirts, stickers and iPhone cases.

You can visit the store here [Link]

You had me at Prophase T-Shirt

New Mitotic Movies

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The Garvan recently took possession of a fantastic new Leica SP8 confocal microscope, which we have been lucky enough to have play with. Here are the results from our first go with the microscope. Very impressive, and we are yet to push the system to its fully potential. The massive increase in resolution and quality will greatly help in rapidly advancing our understanding of key mitotic events.