Cells divide to generate two identical copies of them via a process known as mitosis. Nearly all cells undergo mitosis to generate daughter cells and hence proliferate. Mitosis is very tightly regulated. There are certain checkpoints in place to ensure proper division; a normal cell cannot proceed to the next step of division if all the required parameters are not met; hence it’s very controlled. On the contrary, when cells loose their control over this regulation it leads to abnormal or uncontrolled cell growth and division i.e. cancer. Because mitosis is such a controlled process, the cell requires several different proteins to ensure proper division.
One of the key proteins involved in mitosis are microtubules. Microtubules are a key component of the cytoskeleton as they aid in maintaining cellular structure. They are long filaments composed of polymers of a protein called tubulin. Microtubules are highly dynamic as they can polymerize on one end while dissociate on the other, thus aiding in cell motility. Microtubules are also known as the railroads of the cell, as they lay tracks for certain motor proteins carrying cargo to walk on. Most importantly, during mitosis microtubules are involved in chromosome separation as they form the mitotic spindles (akin to ropes) that pull the chromosomes apart.
The highly dynamic nature of microtubules makes them a target of chemotherapeutics. As such, drugs that interfere with microtubule dynamics are indispensible tools in cell biology. Molecules interfering with microtubule dynamics are being widely used for research and clinically as anticancer drugs. However, these drugs lack specificity towards the targets cells leading to severe side effects caused by chemotherapy.
A recent study published by Borowiak et., al 2015 in the journal Cell, uses photoactivable inhibitors known as photostatins to control microtubule dynamics with light. These inhibitors can be switched on and off using visible light and have a subsecond respond time. More importantly they can control mitosis in living organism with single cell spatial precision. Photostatins are way more cytotoxic (250X) to cells when activated by blue light as compared to when kept in dark. In light of these observations photostatins can be a significant tool in cell biology research and can potentially be used as chemotherapeutics. They can be spatiotemporally (in time and space) controlled by a constrained light source. Increased specificity to target cells would mean less severe side effects as the healthy cells will not be part of the target.
Borowiak et al., Photoswitchable Inhibitors of Microtubule Dynamics Optically Control Mitosis and Cell Death, Cell (2015), http://dx.doi.org/10.1016/j.cell.2015.06.049