Personalized medicine - Lab page of Karl-Friedrich Becker Munich

Institut für Pathologie

Trogerstrasse 18

D-81675 München

The lab page of Karl-Friedrich Becker

- Personalized Medicine: individual gene mutations

as basis for tumor-specific interventions -

Personalized Medicine

Supported by DFG (Klinische Forschergruppe 411 "Radionuklidtherapie")

In collaboration with:

Prof. Dr. R. Senekowitsch-Schmidtke, Dr. Christof Seidl, Dr. Roswitha Huber, Dr. Christoph Schumacher, Prof. Dr. Markus Schwaiger, Dr. Elisabeth Kremmer

Mutant E-cadherin can be differentiated using our mutation-specific monoclonal antibodies E-cadherin specifically visualized in a gastric cancer. Current monoclonal antibodies against E-cadherin do not differentiate between non-tumorous and tumor cells (left). In contrast, our mutation specific E-cadherin antibodies selectively react with abnormal E-cadherin protein expressed by tumor cells (right). (E-cadherin immunoreactivity is visualized with the brown colour. Upper, non-tumorous glands; lower, tumor cells).

More informations about the mutation-specific E-cadherin monoclonal antibodies (PDF, 209 kb)...

Protocols for immunohistochemical analysis: mAb delta 9-1, mAb delta 8-1.

AIM

To establish a personalized diagnosis and therapy of gastric cancer patients on the basis of tumor-specific E-cadherin mutations

STRATEGY

Primary Tumor

Cell culture

Animal model

RT-PCR/Sequencing

Mutation detection

Mutation-specific mAbs

Cloning of mutations

Transfection

Functional analysis

Tumor cell inoculation

Conjugated mAbs

Therapeutic evaluation

RESULTS

Primary Tumor

Cell culture

Animal model

E-cadherin delta 9 mutation

(larger view)

E-cadherin mutations result in reduced homophilic cell to cell contacts and increased cell motility

Animal model for tumor cell-specific radioimmunotherapy

Succesful generation of mutation-specific mAb del9-1

E-cadherin mutations result in reduced homophilic cell to cell contacts and increased cell motility

Conjugation of mAb del9-1 to radionuclide Bi-213, prolonged survival of treated mice

Gastric cancer, one of the most common human cancers with 1 million new cases each year worldwide, displays gene changes in multiple oncogenes, suppressor genes and DNA repair genes. Gastric adenocarcinoma can be divided into two variants, each of which accounts for half of the cases: intestinal type carcinomas, the predominent type of tumor in high-risk areas, have a glandular pattern and are usually accompanied by papillary formation or solid components. By contrast, the so-called diffuse type tumors include signet-ring cell carcinomas and anaplastic adenocarcinomas whose small and fairly uniform cells spread individually. If of a more solid cellular appearance, the individual cells are only loosely attached to each other.

Recently, the cell adhesion molecule E-cadherin has been identified to play a major role in determining which of the two subtypes of gastric cancer develops. We detected somatic E-cadherin gene mutations in 50% of diffuse-type gastric carcinomas. Remarkably, most mutations found either directly or indirectly resulted in in-frame deletions of small portions from the E-cadherin molecule together with the loss of the wild-type allele. In 20% of the patients splice site mutations eliminating either exon 8 or 9 were found, identifying this region as a mutational hot spot. In addition, smaller deletions or single amino acid substitutions destroying highly conserved domains shown to be critical for the adhesive function were detected. In contrast, mutations affecting the E-cadherin amino acid sequence were not identified in intestinal-type tumors nor in 31 non-tumorous epithelial tissues tested.

The characteristic type of E-cadherin mutations in diffuse-type gastric cancer (more than 70% of the mutations are complete or partial deletions of exons that do not interrupt the translation of the mRNA but will result in the synthesis of a slightly shortened protein) might improve the information of conventional diagnostic techniques. This special type of mutation allows the construction of mutation-specific antibodies and the detection of the altered protein at the cell membrane of tumor cells in various compartments, including biopsies, primaries, lymph node metastasis, bone marrow and blood. Tumor-specific monoclonal antibodies against the hot spot region are already available. Besides for use in diagnosis, after linking to toxins, drugs or radioisotopes these conjugated antibodies could serve as highly specific agents to treat small tumour deposits for adjuvant-, neoadjuvant- and additive therapy. In cell culture studies we could show that E-cadherin mutation-specific immunotoxins exclusively killed cells expressing abnormal E-cadherin; those cells expressing the normal protein were not affected. In addition, in a mouse model we could show that radiolabelled antibodies selectively target tumor cells expressing mutant E-cadherin, resulting in prolonged animal survival, demonstating the specificity of our approach.

References:

Christof Seidl, Hedwig Schröck, Sabine Seidenschwang, Roswitha Beck, Ernst Schmid, Michael Abend, Karl-Friedrich Becker, Christos Apostolidis, Tuomo K. Nikula, Elisabeth Kremmer, Markus Schwaiger and Reingard Senekowitsch-Schmidtke. Cell death triggered by alpha-emitting 213Bi-immunoconjugates in HSC45-M2 gastric cancer cells is different from apoptotic cell death. European Journal of Nuclear Medicine and Molecular Imaging 2004. DOI: 10.1007/s00259-004-1653-3

Huber R, Seidl C, Schmid E, Seidenschwang S, Becker KF, Schuhmacher C,
Apostolidis C, Nikula T, Kremmer E, Schwaiger M, Senekowitsch-Schmidtke R. Locoregional alpha-radioimmunotherapy of intraperitoneal tumor cell dissemination using a tumor-specific monoclonal antibody. Clin Cancer Res. 2003 Sep 1;9(10 Pt 2):3922S-8S.

Miederer M, Seidl C, Beyer GJ, Charlton DE, Vranjes-Duric S, Comor JJ, Huber R, Nikula T, Apostolidis C, Schuhmacher C, Becker KF, Senekowitsch-Schmidtke R. Comparison of the radiotoxicity of two alpha-particle-emitting immunoconjugates, terbium-149 and bismuth-213, directed against a tumor-specific, exon 9 deleted (d9) E-cadherin adhesion protein. Radiat Res. 2003 May;159(5):612-20.

Becker KF, Kremmer E, Eulitz M, Becker I, Handschuh G, Schuhmacher C,
Muller W, Gabbert HE, Ochiai A, Hirohashi S, Hofler H. Analysis of E-cadherin in diffuse-type gastric cancer using a mutation-specific monoclonal antibody. Am J Pathol. 1999 Dec;155(6):1803-9.

© 2003-2005 Dr. Karl-Friedrich Becker, Institut für Pathologie, TU München

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