A Look at Cancer Cells

Thanks to a groundbreaking technique in super-resolution microscopy, scientists have been able to observe, in fine detail and in three dimensions, the way therapeutic antibodies target and modify B cells, ultimately leading to their destruction. This research introduces a novel method of visualizing molecular interactions between antibodies and cells, paving the way for advancements in cancer immunotherapy.
Blood cancers, particularly chronic lymphocytic leukaemia, cause an uncontrolled rise in B cells within the immune system. One therapeutic approach involves marking the CD20 protein that sits on the surface of B cells with specially designed antibodies. This initiates a series of immunological reactions that culminate in the obliteration of cancer cells.

Therapeutic antibodies have been utilized against various tumor-related diseases for three decades. ‘While the mechanics of therapy’s success are crucial, our understanding of how antibodies attach to CD20 and the resulting reactions remains limited,’ explains Professor Markus Sauer from the Biocentre of Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.

Tracking the Effectiveness of Antibodies

This situation is set to improve: A research team headed by the JMU biophysicist has created a new super-resolution microscopy method. This innovative technique allows for the first time the exploration of how therapeutic antibodies interact with specific molecules on tumor cells in 3D with molecular precision.

‘We can now better assess the efficacy of the antibodies, which will aid in developing enhanced treatments,’ says Markus Sauer.

The recently developed technique is called LLS-TDI-DNA-PAINT. In an article published in the journal Science, lead author Dr. Arindam Ghosh and colleagues from Markus Sauer’s group detail the workings of this technology and the insights gained so far. Dr. Thomas Nerreter and Professor Martin Kortüm from the Medical Clinic II at Würzburg University Hospital also contributed to this study.

B Cells Take on the Shape of a Hedgehog

The research team from Würzburg conducted their experiments on both fixed and live Raji B cells, a cell line derived from a patient’s Burkitt’s lymphoma, commonly used in cancer studies. The cells were exposed to one of four therapeutic antibodies: RTX, OFA, OBZ, and 2H7.

All four antibodies provoke the crosslinking of CD20 molecules found in the cell membrane, resulting in concentrated clusters of the antibodies. This process activates the complement system and sets off a sequence where the immune system destroys the targeted cells. Contrary to current classifications, findings indicate that the crosslinking of CD20 molecules occurs regardless of whether the antibodies are classified as type I or II.

The results also indicate that each of the four antibodies leads to the crosslinking of CD20 molecules located at particular membrane regions, specifically on long, finger-like extensions known as ‘microvilli’. Additionally, the binding of these antibodies causes the B cell to polarize, thereby stabilizing the extended microvilli. This behavior results in B cells assuming a hedgehog-like appearance, with membrane extensions appearing predominantly on one side of the cell.

The Next Steps in Research

What does the future hold? ‘The previous system of classifying therapeutic antibodies into types I and II is no longer viable,’ states Dr. Arindam Ghosh. Historically, researchers believed that type I therapeutic antibodies functioned differently from type II. However, those assumptions have been challenged by findings from the Würzburg studies.

‘The hedgehog formation suggests that B cells may attempt to establish an immunological synapse with another cell,’ adds the JMU researcher. It remains possible that these treated B cells activate macrophages and natural killer cells within the immune system through this process. The research team aims to investigate this hypothesis in future studies.