gms | German Medical Science

27th German Cancer Congress Berlin 2006

German Cancer Society (Frankfurt/M.)

22. - 26.03.2006, Berlin

Role of Src-family kinases in Gastrointestinal Stromal Tumors

Meeting Abstract

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  • corresponding author presenting/speaker Sebastian Bauer - Westdeutsches Tumorzentrum, Universitätsklinikum, Essen, Deutschland
  • George D Demetri - Dana Farber Cancer Institute, Boston, MA (USA)
  • Jonathan A Fletcher - Brigham & Women“s Hospital, Harvard Medical School, Boston, MA (USA)

27. Deutscher Krebskongress. Berlin, 22.-26.03.2006. Düsseldorf, Köln: German Medical Science; 2006. DocOP171

The electronic version of this article is the complete one and can be found online at:

Published: March 20, 2006

© 2006 Bauer et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Background: Inhibition of KIT oncoproteins by imatinib mesylate (IM) induces clinical responses in most GIST patients. However, many patients develop IM-resistance due to secondary KIT mutations and none of the novel KIT inhibitors inhibits all known IM-resistance mutations. Src-family kinases (SFK) are important signaling intermediates in related kinase-driven tumor models (ALL, CML) and dual-specific Src/Abl-inhibitors show promising activity in IM-resistant CML in vitro. However, little is known about SFK functional role in IM-resistant GIST.

Methods: GIST (IM sensitive and resistant) were analyzed for expression and activation of Src-family kinases (SFK) using western blotting. Biological consequences of KIT inhibition alone (IM), SFK inhibition (SU6656) and combined KIT/SFK inhibition (PP1, PP2, SU6656+IM) was determined by immunoblotting for protein activation, and by luminescence assays for cell proliferation in GIST cell lines.

Results: Primary GIST and GIST cell lines showed weak activation of SFK compared to controls (Jurkat) as measured by phosphorylation of Y418. Variable expression of c-yes, c-fyn, c-lyn and c-src but not c-blk and c-lck) was observed in both cell lines and primary GIST. Expression of c-hck and c-fgr was found in 2 primary GIST only. KIT and KIT signaling pathways (pAKT, pS6, pSTAT3) were affected by IM and combined KIT inhibitors but not by SU6656 at 1µM in both GIST882 (primary IM-sensitive mutation) and GIST48 (IM-sensitive juxtamembrane and secondary kinase domain mutation). Phosphorylation of src (Y418) was not affected by IM or SFK-inhibitors at 1µM. IM showed superior inhibition of proliferation compared to PP1 and PP2 (1µM) in GIST882 (IM:67%, PP1:1%, PP2:0%) and comparable inhibition in GIST48 (IM:30%, PP1: 29%, PP2: 29%). No effects on proliferation were seen with SU6656 alone or in combination with IM; no antagonistic effects were observed.

Conclusion: Our analysis showed expression and weak activation of several SFK in GIST. Expression of heme-associated SFKs in primary GIST may be explained by lymphocellular infiltration. Biochemical inhibition of SFK alone does not have antiproliferative effects in GIST cell lines, and no synergies or antagonisms were found in combination with IM or with combined KIT/SFK inhibitors. Therefore, targeting of SFK may be of less therapeutic value in GIST than in kinase-driven hematological cancers.