Tag: tumours

Neutron reflectometry reveals how cancer cells can avoid programmed cell death

Neutron reflectometry reveals how cancer cells can avoid programmed cell death

Researchers have revealed a mechanism by which cancer cells can avoid programmed cell death. The team, from ISIS, the European Spallation Source (ESS), Lund University, the University of Umeå, the Institut Laue-Langevin (ILL) and Diamond Light Source, used an integrated combination of techniques to investigate how the Bax and Bcl-2 proteins involved in regulating programmed cell death, or apoptosis, interact at the surface of the mitochondrial outer membrane.

Apoptosis is one of the processes our body uses to control cell growth and proliferation. It plays a vital role in embryo development, in removing old or damaged cells, and in our immune systems. However, when it goes wrong, as in many cancers, those cells can escape their apoptotic removal and rapidly multiply to form tumours. Many cancer therapies, such as chemotherapy or radiotherapy, treat cancers by causing DNA damage or stressing cells, which leads to apoptosis. However, many tumours can also become treatment resistant by escaping even treatment-induced apoptotic death.

Controlling apoptosis

One of the key proteins that controls apoptosis is called Bax. Bax works by creating pores in mitochondrial membranes to start a biochemical cascade that results in cell death. Bax is usually tightly controlled by Bcl-2 proteins, which bind Bax and prevents it forming pores. The gene for Bcl-2 is involved in almost 50% of human cancers; these cancerous cells often produce more Bcl-2, leading to tumour development and protecting the cancerous cells from therapies.

To understand precisely how Bcl-2 and Bax interact, the researchers used a combination of neutron reflectometry on the Surf and Offspec instruments at ISIS and on Figaro at the Institut Laue Langevin, electron microscopy at eBIC, and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). They created a supported lipid bilayer resembling the mitochondrial outer membrane and which contained Bcl-2 proteins.

A two-step process in avoiding apoptosis

Kinetics of Bax sequestration by Bcl-2 at membrane level: from initial contact to oligomerization

The team found that, without Bcl-2, introducing Bax disrupted the membrane. When the membrane contained Bcl-2 the researchers initially saw a direct correlation between the amount of Bcl-2 in the membrane and the amount of Bax on the membrane surface, suggesting the Bcl-2 was binding directly to the Bax and preventing it from forming pores. Over time, however, they saw a second, slower process. The Bax proteins formed clusters, or oligomers, standing vertically upwards from the membrane surface, which sequestered Bax, prevented pore formation.

Read more on the Diamond website

A new way to look at thyroid tumours

A new way to look at thyroid tumours

Follicular tumours in the thyroid can be difficult to diagnose as the entire follicle capsule needs to be sliced and inspected in order to detect ruptures. The current protocol involves cytology and histology, but these have limitations. Researchers from Uppsala University (UU) and Lund University (LU) are investigating the potential use of synchrotron-based virtual histology for 3D inspection of the follicle capsule at MAX IV.

Thyroid tumours can be either benign follicular adenoma or malignant follicular carcinoma. The ability to assess the difference is crucial. Although cytological analysis can effectively distinguish between benign and malignant, it is unable to detect key diagnostic indicators of follicular carcinoma such as capsular breach or vascular invasion. In addition, further detailed histopathological analysis following diagnostic surgery is often required, which can be meticulous and time-consuming due to the number of thin slices necessary to correctly identify whether malignant indicators are present. Lund University Associate Professor Martin Bech and resident Physician Matilda Annebäck and Chief Physician Olov Norlén from Uppsala University conducted a pilot study at MAX IV’s DanMAX beamline to determine the applicability of a new and improved assessment method for thyroid tumours.

Synchrotron radiation-based micro-tomography (SRµCT) is an imaging technique that enables 3D mapping of internal structures of materials. At DanMAX, the field of view is 1.2 x 1.2 mm, allowing analysis of the thyroid lobes and, with exceptional spatial resolution, enabling detailed 3D visualization of the thyroid tissue.

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The goal is that SRµCT will detect those diagnostic features that are missed or difficult to spot with current available methods. Another advantage of SRµCT is that it is non-destructive to the sample, and thus will allow for subsequent histological analysis for comparative analysis between the two techniques

This will be the first study using SRµCT for follicular thyroid tumours, although it has been conducted elsewhere in other tissues from the lung, heart and brain. The challenge in the current experiment was the sample size in relation to the beam size. As a proof-of-concept experiment, it was deemed successful.

MAX IV is an ideal location for clinical experiments in Sweden as ethical approval often has stipulations about transport of samples outside of the country. The study samples were used for diagnostic purposes thus it was not difficult to obtain the ethics approval.

The collaboration between experts in the thyroid field (Department of Surgical Sciences; Endocrine Surgery, UU), and experts in SRµCT (X-Ray Phase Contrast Group, LU), arose after Martin Bech presented at Uppsala about the possibilities at MAX IV, with Olof Norlén in attendance at the talk.

This is a great example of how many studies are conducted at MAX IV and illustrates the need for mixed expertise in order to conduct these experiments, as the researchers from UU have the clinical expertise but were new users at MAX IV. As both parties are part of academic institutions, they were able to apply for free access to MAX IV through the peer-reviewed process which negates the need to apply for separate experimental funding.

SRµCT experiments generate substantial data, which is currently being analysed by the pathologist at UU and compared to their histological findings. More detailed data analysis will be another collaboration between the two research groups with the ultimate goal to publish the findings. This technique is of great interest to pathologists and has further implications both in the research and clinical fields.

Read more on MAXIV website

Image: Thyroid tumour sample at DanMAX beamline.

 Credit: MAX IV