Send to

Choose Destination
PLoS One. 2014 Sep 8;9(9):e107165. doi: 10.1371/journal.pone.0107165. eCollection 2014.

EGFR-targeted TRAIL and a Smac mimetic synergize to overcome apoptosis resistance in KRAS mutant colorectal cancer cells.

Author information

Institute of Cell Biology and Immunology, University of Stuttgart, Stuttgart, Germany.
Institute of Molecular Medicine and Cell Research (IMMZ), Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Freiburg, Germany; Faculty of Biology, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.
Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy.
Institute of Molecular Medicine and Cell Research (IMMZ), Faculty of Medicine, Albert-Ludwigs-University of Freiburg, Freiburg, Germany; Centre for Biological Signalling Studies BIOSS, Albert-Ludwigs-University of Freiburg, Freiburg, Germany.


TRAIL is a death receptor ligand that induces cell death preferentially in tumor cells. Recombinant soluble TRAIL, however, performs poorly as an anti-cancer therapeutic because oligomerization is required for potent biological activity. We previously generated a diabody format of tumor-targeted TRAIL termed Db(αEGFR-sc)TRAIL, comprising single-stranded TRAIL molecules (scTRAIL) and the variable domains of a humanized variant of the EGFR blocking antibody Cetuximab. Here we define the bioactivity of Db(αEGFR)-scTRAIL with regard to both EGFR inhibition and TRAIL receptor activation in 3D cultures of Caco-2 colorectal cancer cells, which express wild-type K-Ras. Compared with conventional 2D cultures, Caco-2 cells displayed strongly enhanced sensitivity toward Db(αEGFR)-scTRAIL in these 3D cultures. We show that the antibody moiety of Db(αEGFR-sc)TRAIL not only efficiently competed with ligand-induced EGFR function, but also determined the apoptotic response by specifically directing Db(αEGFR)-scTRAIL to EGFR-positive cells. To address how aberrantly activated K-Ras, which leads to Cetuximab resistance, affects Db(αEGFR-sc)TRAIL sensitivity, we generated stable Caco-2tet cells inducibly expressing oncogenic K-Ras(G12V). In the presence of doxycycline, these cells showed increased resistance to Db(αEGFR-sc)TRAIL, associated with the elevated expression of the anti-apoptotic proteins cIAP2, Bcl-xL and FlipS. Co-treatment of cells with the Smac mimetic SM83 restored the Db(αEGFR)-scTRAIL-induced apoptotic response. Importantly, this synergy between Db(αEGFR)-scTRAIL and SM83 also translated to 3D cultures of oncogenic K-Ras expressing HCT-116 and LoVo colorectal cancer cells. Our findings thus support the notion that Db(αEGFR)-scTRAIL therapy in combination with apoptosis-sensitizing agents may be promising for the treatment of EGFR-positive colorectal cancers, independently of their KRAS status.

[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Public Library of Science Icon for PubMed Central
Loading ...
Support Center