Max-Delbrück-Centrum für Molekulare Medizin (MDC)

Multiple myeloma is one of the most common forms of cancer of the immune cells in the bone marrow. It is considered incurable. Even when patients respond to treatment at first, the cancer comes back. To be able to intervene faster and on a more targeted basis, researchers completed a comprehensive study of this disease at the molecular level. Multiple myeloma is one of the most common forms of cancer of the immune cells in the bone marrow. It is considered incurable. Even when patients respond to treatment at first, the cancer comes back. To be able to intervene faster and on a more targeted basis, researchers at Charité -- Universitätsmedizin Berlin, the Berlin Institute of Health at Charité (BIH), and the Max Delbrück Center teamed up with other partners for a comprehensive study of this disease at the molecular level. The team now describes how highly aggressive types of tumors can be detected early on in an article published in the journal Nature Cancer.* They show how changes in genetic material affect the protein pro the tumor cells, and thus the mechanisms involved in the disease. Multiple myeloma is a form of cancer in which the immune cells in the bone marrow, known as plasma cells, mutate and become cancerous. Plasma cells are responsible for producing antibodies. All humans have many different kinds of plasma cells that form large numbers of different antibodies. This allows the body to recognize and fight various pathogens. In multiple myeloma, a single plasma cell mutates into a tumor cell. That cell reproduces unchecked, forming a monoclonal cell population. This means many cells are formed, all of them exactly the same and genetically identical at first. The mutated cells often also produce large volumes of antibodies or fragments of them -- but they do not function properly. Over the course of the disease, most patients develop tumors at various locations in the bone marrow, hence the "multiple" in the disease's name. Immunodeficiency, kidney failure, bone loss, and bone fractures are just some of the consequences of this uncontrolled cell growth. Despite advances in treatment and the introduction of new gene and cell therapies, there is no cure for multiple myeloma at present. With this issue in mind, a team of researchers led by Jan Krönke from the Department of Hematology, Oncology and Cancer Immunology at Charité and Dr. Philipp Mertins, head of the Proteomics technology platform of the Max Delbrück Center and BIH, set out in search of new approaches to diagnosis and treatment. What path does the tumor take? No two cases of cancer are alike, and multiple myeloma is no exception. Tumors develop differently in different individuals, including at different rates. This makes it more difficult to predict how the disease will progress and choose the optimum treatment. While the mutated plasma cells do not spread much in some cases, in others they are extremely aggressive, leading to a poor prognosis. But what causes so much divergence in the course of multiple myeloma? In cooperation with protein analysis experts from the Max Delbrück Center and BIH, the researchers conducted a detailed study of genetic and molecular changes occurring in the tumor cells in a group of more than one hundred patients. The study included data from patients in the German Multiple Myeloma Study Group (DSMM), which is coordinated by the University Hospital of Würzburg. This allowed the researchers to include clinical data on patients who had received standardized treatment over a period of eight years or more following initial diagnosis. Systems medicine and big data While changes in the genome and their effects on the proteome are already well described for other types of cancer, this is the first detailed proteo-genomic study of multiple myeloma. "Genetic data alone is insufficient to explain the mechanisms involved in this disease," Mertins says. "We wanted to know the consequences of genetic changes at the protein level and compare this molecular biology data against the actual course of the disease in patients." The team was supported in collecting and analyzing the large volumes of data by experts at Charité, BIH, and the German Cancer Consortium (DKTK). Cutting-edge mass spectrometry methods made it possible to map the protein pro mutated plasma cells and compare it against that of healthy plasma cells in people without the disease. The researchers found that both genetic changes and changes in signaling pathways lead to uncontrolled activation of cancer cells. Regulatory processes at the protein level had the stronger influence. The researchers identified a protein constellation that suggests the disease will take a particularly aggressive course, regardless of other known risk factors. Unlocking new therapies "Our findings will help subcategorize patients more effectively going forward, personalizing their treatment," Krönke concludes. "We've identified key proteins and signaling pathways that can serve as the basis for even more effective, better tolerated treatments for multiple myeloma, for example for immune therapies such as CAR T-cell therapy." In further steps, the researchers plan to study which of the target structures they have identified are in fact good candidates for new therapeutic approaches. The study is a crucial resource for research and applied development, says Dr. Evelyn Ramberger, first author of the study: "To make the complex data set manageable, we programmed an interactive, freely available online tool." This has given cancer researchers easy access to the results, so they can use the information to develop new therapies and tests to help guide treatment. For example, it may be possible to treat patients with an especially aggressive form of multiple myeloma with more intensive therapies right at the outset. Mass spectrometry Mass spectrometry is a technique for analyzing the mass of molecules and atoms. The substance to be analyzed is ionized and converted to a gas phase. The ions formed are sharply accelerated using an electric field and then sorted by mass-to-charge ratio in the mass spectrometer's analytical unit. The mass spectrum of a substance provides information on its molecular composition. Mass spectrometry is therefore useful for identifying, characterizing, and quantifying a large number of biomolecules, such as proteins, metabolites, sugars, and fats, which may behave differently depending on the disease and the individual organism.

Researchers reveal how cells accelerate changes to their identity, a process known as cell fate conversion. The study has implications for cancer research as the disease often arises from errors in cell fate decisions. The study could eventually lead to new methods of accelerating or manipulating the molecular mechanisms involved in the formation of cancer. Researchers at the Centre for Genomic Regulation (CRG) in Barcelona and the Max Delbrück Center for Molecular Medicine in the Helmholtz Association in Berlin reveal how cells accelerate changes to their identity, a process known as cell fate conversion. The study, published today in the journal eLife, has implications for cancer research as the disease often arises from errors in cell fate decisions. The study could eventually lead to new methods of accelerating or manipulating the molecular mechanisms involved in the formation of cancer. Central to the study is C/EBPα (CCAAT/enhancer-binding protein alpha), a protein that orchestrates the conversion of B lymphocytes to macrophages, another type of immune cell. C/EBPα is a transcription factor, a type of protein which binds to specific DNA sequences in the regulatory regions of genes to influence the rate of transcription, the first step that leads to the activation or silencing of protein expression. Transcription factors play a vital role in the transformation of one cell type to another during differentiation and development, as well as in the growth and function of cells. Like many other proteins, C/EBPα is modified by enzymes, for example through the addition of a methyl group to specific amino acids. These modifications can have significant effects on interactions of the protein. The researchers found that when one specific arginine residue of C/EBPα is left unmethylated, it greatly accelerates the conversion process of B lymphocytes to macrophages. The study also found that the methylation of this specific arginine residue is mediated by the enzyme Carm1. Previous research has shown that Carm1-deficient mice are resistant to induced forms of acute myeloid leukaemia. The researchers hypothesise that the mechanisms they uncover in the present study can explain why: the unmethylated version of C/EBPα is a stronger inducer of macrophage differentiation compared to its methylated counterpart. As macrophages are a non-dividing cell type, this could prevent the formation of cancer cells. The researchers made the discovery while screening for C/EBPα mutants which affect the efficiency of cell fate conversion using human and mouse models. The location of the critical amino acid within C/EBPα was found when the authors tested a mutant form called C/EBPαR35A. This mutant dramatically accelerated the speed by which B cells could be turned into macrophages. To induce a cell conversion, C/EBPα works by interacting with another transcription factor called PU.1, which itself is essential for the development of immune cells and is already expressed in B cells. C/EBPαR35A had a much higher interaction affinity with PU.1, increasing the speed by which the combination of the two proteins silence the genes associated with B cells and activate the genes associated with macrophages. The methylation of C/EBPα is an example of an epigenetic mechanism. These are mechanisms which modify how the genome -- the instruction manual inside every cell of the human body -- is read. "Drugs that affect epigenetic mechanisms as described in the present study may indeed alter the function of transcription factors and correct cells that went astray, such as seen in cancer and leukaemia," says Dr. Achim Leutz, senior author from the Max-Delbrück-Center. "In this novel mechanism PU.1 is triggered by C/EBPα to switch from a B cell regulator into a macrophage regulator, an elegant 'on-off' mechanism that ensures the faithful formation of a mature cell type, avoiding the formation of 'confused' cells often seen in blood cancers. Therefore, drugs might be found that target this mechanism to correct such defects" adds Dr. Leutz. According to the authors of the study, much remains unknown about what determines the speed and directionality of cell fate decisions and their new work suggests that the two processes are two sides of the same coin. For instance, how do stem cells sequentially transform into the many different types of cells in the body? Better understanding how cells change their identity and how to manipulate the process might have applications from regenerative medicine to improving the efficacy of drugs against cancer. The research was led by a joint collaboration between the Centre for Genomic Regulation in Barcelona, the Max Delbrück Center for Molecular Medicine in Berlin and the University of Pennsylvania in Philadelphia. The study was funded by the Spanish Ministry of Economy, Industry and Competitiveness, the Catalan Agency of Research and Universities, a 4D-Genome European Research Council Synergy grant, by funds from the Max-Delbrueck-Center, and the United States National Institute of Health.

Regulatory T cells ensure that immune responses happen in a controlled way. But eating too much salt weakens these cells' energy supply, thus rendering them dysfunctional for a while. This may have implications for autoimmunity. Regulatory T cells ensure that immune responses happen in a controlled way. But eating too much salt weakens these cells' energy supply, thus rendering them dysfunctional for a while. This may have implications for autoimmunity, an international team -- including Dominik Müller -- reports in Cell Metabolism. Eating too much salt, which is common in many Western societies, is not only bad for our blood pressure and cardiovascular system -- it could also adversely impact the immune system. An international research team, coordinated by scientists at the VIB Center for Inflammation Research and Hasselt University in Belgium as well as the Max Delbrück Center in Germany, is now reporting in "Cell Metabolism" that salt can disrupt key immune regulators called regulatory T cells by impairing their energy metabolism. The findings may provide new avenues for exploring the development of autoimmune and cardiovascular diseases. A few years ago, research by teams led by Professor Dominik Müller at the Max Delbrück Center for Molecular Medicine and the Experimental and Clinical Research Center, a joint institution of Charité -- Universitätsmedizin Berlin and Max Delbrück Center (ECRC) in Berlin, Germany and Professor Markus Kleinewietfeld at the VIB Center for Inflammation Research and Hasselt University in Belgium, as well as by colleagues of theirs, revealed that too much salt in our diet can negatively affect the metabolism and energy balance in certain types of innate immune cells called monocytes and macrophages and stop them from working properly. They further showed that salt triggers malfunctions in the mitochondria, the power plants of our cells. Inspired by these findings, the research groups wondered whether excessive salt intake might also create a similar problem in adaptive immune cells like regulatory T cells. Important immune regulators Regulatory T cells, also known as Tregs, are an essential part of the adaptive immune system. They are responsible for maintaining the balance between normal function and unwanted excessive inflammation. Tregs are sometimes referred to as the "immune police" because they keep bad guys like autoreactive immune cells at bay and ensure that immune responses happen in a controlled way without harming the host organism. Scientists believe that the deregulation of Tregs is linked to the development of autoimmune diseases like multiple sclerosis. Recent research has identified problems in mitochondrial function of Tregs from patients with autoimmunity, yet the contributing factors remain elusive. "Considering our previous findings of salt affecting mitochondrial function of monocytes and macrophages as well as the new observations on mitochondria in Tregs from autoimmune patients, we were wondering if sodium might elicit similar issues in Tregs of healthy volunteers," says Müller, who co-heads the Hypertension-Mediated End-Organ Damage Lab at the Max Delbrück Center and the ECRC. Previous research has also shown that excess salt could impact Treg function by inducing an autoimmune-like phenotype. In other words, too much salt makes the Treg cells look like those involved in autoimmune conditions. However, exactly how sodium impairs Treg function had not yet been uncovered. Salt interferes with mitochondrial function of Tregs The new international study led by Kleinewietfeld and Müller and first-authored by Dr. Beatriz Côrte-Real and Dr. Ibrahim Hamad -- both of whom work at the VIB Center for Inflammation Research and Hasselt University in Belgium -- has now discovered that sodium disrupts Treg function by altering cellular metabolism through interference with mitochondrial energy generation. This mitochondrial problem seems to be the initial step in how salt modifies Treg function, leading to changes in gene expression that showed similarities to those of dysfunctional Tregs in autoimmune conditions. Even a short-term disruption of mitochondrial function had long-lasting consequences for the fitness and immune-regulating capacity of Tregs in various experimental models. The new findings suggest that sodium may be a factor that could contribute to Treg dysfunction, potentially playing a role in different diseases, although this needs to be confirmed in further studies. "The better understanding of factors and underlying molecular mechanisms contributing to Treg dysfunction in autoimmunity is an important question in the field. Since Tregs also play a role in diseases such as cancer or cardiovascular disease, the further exploration of such sodium-elicited effects may offer novel strategies for altering Treg function in different types of diseases," says Kleinewietfeld, who heads the VIB Laboratory for Translational Immunomodulation. "However, future studies are needed to understand the molecular mechanisms in more detail and to clarify their potential relationship to disease."