Strategic Communication and Public Relations

Researchers discover a possible reason for drug resistance in breast tumors

No. 33c3 | 20/07/2015 | by Koh

HER2 membrane proteins play a special role in certain types of breast cancer: amplified levels of HER2 drive unrestricted cell growth. HER2-tailored antibody-based therapeutics aim to prevent cancer cell growth. However, two-thirds of HER2 positive breast cancer patients develop resistance against HER2-targeting drugs. The reason for this is not yet understood. Researchers now found out, that HER2 dimers appeared to be absent from a small sub-population of resting SKBR3 breast cancer cells. This small subpopulation may have self-renewing properties that are resistant to HER2-antibody therapy and thus able to seed new tumor growth.

Single molecules and dimers of the HER2-receptor can be distinguished with Liquid STEM Microscopy
© Leibniz Institut für neue Materialien

For their studies researchers from the INM – Leibniz-Institute for New Materials, Saarbrücken and from the German Cancer Research Center (DKFZ) in Heidelberg used a new electron microscopy method called Liquid STEM. It allows nanoscale studies of intact cells in their native liquid environment.

The scientists have studied the local variations of HER2 membrane protein and of its dimers. HER2 is a member of the human epidermal growth factor receptor (EGFR) family. These family members trigger cell growth signals, when two of the membrane proteins are bound into a protein complex (dimerization). This happens usually after the binding of a small protein, the epidermal growth factor, which circulates in the blood stream and serves as communicator to transmit signals that regulate cell growth. HER2 is special in the sense that it does not need the growth factor protein in order to form dimers. It is thus capable of triggering cell growth without external regulation. In certain types of breast cancer, amplified levels of HER2 and its dimerization are known to drive unrestricted cell growth. HER2-tailored antibody-based therapeutics entered clinical practice more than a decade ago. These drugs aim to prevent cell growth triggered by HER2 homo- and/or heterodimerization.

“We found out, that HER2 dimers appeared to be absent from a small sub-population of resting SKBR3 cells. Could such cells survive the therapy and then develop into a drug resistant cancer at a later stage? It thus seems to be of key significance to study this sub-population of cells with exceptional phenotype,” says Niels de Jonge, head of the Innovative Electron Microscopy group.

HER2 dimerization processes were thus far mostly studied on the basis of cell population averages, for example, with biochemical methods using pooled cell material, and information about the localization of HER2 dimerization was lacking. Therefore, the researchers around de Jonge pioneered the electron microscopy method Liquid STEM to imaging these receptors on cancer cells. The cells were examined on a microchip placed in the electron microscope, and remained intact and in liquid. “Specimens cannot be studied in liquid with traditional electron microscopy”, explains Professor de Jonge. “Cells are typically studied in dry state via thin sectioning of solid dried plastic embedded or frozen material. The role of HER proteins is a "hot" topic in cancer research but despite large research efforts using a wide range of techniques over the past decades this important information was not unveiled before. Our novel findings were obtained as a direct consequence of the high spatial resolution of Liquid STEM combined with its capability to study many intact cells in liquid,” says de Jonge.

D. B. Peckys, U. Korf, N. de Jonge: Local variations of HER2 dimerization in breast cancer cells discovered by correlative fluorescence and liquid electron microscopy. Science Advances, 2015, DOI: 10.1126/sciadv.1500165 

The German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) with its more than 3,000 employees is the largest biomedical research institution in Germany. More than 1,300 scientists at the DKFZ investigate how cancer develops, identify cancer risk factors and search for new strategies to prevent people from developing cancer. They are developing new methods to diagnose tumors more precisely and treat cancer patients more successfully. The DKFZ's Cancer Information Service (KID) provides patients, interested citizens and experts with individual answers to all questions on cancer.

Jointly with partners from the university hospitals, the DKFZ operates the National Center for Tumor Diseases (NCT) in Heidelberg and Dresden, and the Hopp Children's Tumour Center KiTZ in Heidelberg. In the German Consortium for Translational Cancer Research (DKTK), one of the six German Centers for Health Research, the DKFZ maintains translational centers at seven university partner locations. NCT and DKTK sites combine excellent university medicine with the high-profile research of the DKFZ. They contribute to the endeavor of transferring promising approaches from cancer research to the clinic and thus improving the chances of cancer patients.

The DKFZ is 90 percent financed by the Federal Ministry of Education and Research and 10 percent by the state of Baden-Württemberg. The DKFZ is a member of the Helmholtz Association of German Research Centers.

RSS-Feed

Subscribe to our RSS-Feed.

to top
powered by webEdition CMS