EGFRvIII expression triggers a metabolic dependency and therapeutic vulnerability sensitive to autophagy inhibition

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E-Cadherin loss associated with EMT promotes radioresistance in human tumor cells

BACKGROUND AND PURPOSE: Hypoxia is a hallmark of solid cancers and associated with metastases and treatment failure. During tumor progression epithelial cells often acquire mesenchymal features, a phenomenon known as epithelial-to-mesenchymal transition (EMT). Intratumoral hypoxia has been linked to EMT induction. We hypothesized that signals from the tumor microenvironment such as growth factors and tumor oxygenation collaborate to promote EMT and thereby contribute to radioresistance. MATERIALS AND METHODS: Gene expression changes under hypoxia were analyzed using microarray and validated by qRT-PCR. Conversion of epithelial phenotype upon hypoxic exposure, TGFβ addition or oncogene activation was investigated by Western blot and immunofluorescence. Cell survival following ionizing radiation was assayed using clonogenic survival. RESULTS: Upon hypoxia, TGFβ addition or EGFRvIII expression, MCF7, A549 and NMuMG epithelial cells acquired a spindle shape and lost cell–cell contacts. Expression of epithelial markers such as E-cadherin decreased, whereas mesenchymal markers such as vimentin and N-cadherin increased. Combining hypoxia with TGFβ or EGFRvIII expression, lead to more rapid and pronounced EMT-like phenotype. Interestingly, E-cadherin expression and the mesenchymal appearance were reversible upon reoxygenation. Mesenchymal conversion and E-cadherin loss were associated with radioresistance. CONCLUSIONS: Our findings describe a mechanism by which the tumor microenvironment may contribute to tumor radioresistance via E-cadherin loss and EMT

The deletion mutant EGFRvIII significantly contributes to stress resistance typical for the tumour microenvironment

BACKGROUND AND PURPOSE: The epidermal growth factor receptor (EGFR) is overexpressed or mutated in many tumour types. The truncated, constitutively active EGFRvIII variant has not been detected in normal tissues but is found in many malignancies. In the current study, we have investigated the hypothesis that EGFRvIII contributes to a growth and survival advantage under tumour microenvironment-related stress conditions. MATERIALS AND METHODS: U373MG doxycycline-regulated isogenic cells expressing EGFRwt or EGFRvIII were created and validated using Western blot, FACS and qRT-PCR. In vitro proliferation was evaluated with standard growth assays. Cell survival was assayed using clonogenic survival. Animal experiments were performed using NMRI-nu-xenografted mice. RESULTS: Inducible isogenic cell lines were created and showed high induction of EGFRwt and EGFRvIII upon doxycycline addition. Overexpression of EGFRvIII but not of EGFRwt in this model resulted in a growth and survival advantage upon different tumour microenvironment-related stress conditions in vitro. Induction of EGFRvIII increased tumour growth in vivo, which was reversible upon loss of expression. CONCLUSIONS: Under conditions where nutrients are limited and stress is apparent, as in the tumour microenvironment, expression of EGFRvIII leads to a growth and survival advantage. These data indicate a potential selection of EGFRvIII-expressing tumour cells under such stress conditions

Development and evaluation of a cetuximab-based imaging probe to target EGFR and EGFRvIII

BACKGROUND AND PURPOSE: The epidermal growth factor receptor (EGFR) is overexpressed in a significant percentage of human malignancies and its expression is associated with tumour aggressiveness and treatment resistance. The monoclonal antibody cetuximab (IMC-C225) blocks the ligand-binding domain of EGFR with high affinity, preventing downstream signalling resulting in tumour growth inhibition. We developed and characterized a novel imaging probe using Oregon Green 488 labelled cetuximab to evaluate its usage as an imaging agent to target EGFR. MATERIALS AND METHODS: Cells with varying expression levels of EGFR or a mutant form of EGFR, called EGFRvIII, were used for in vitro validation. The in vivo binding of labelled cetuximab to EGFR was also assessed ex vivo on tumour material. RESULTS: The development of Oregon Green 488 labelled cetuximab was successful, demonstrating binding to both EGFR and EGFRvIII in vitro. Accumulation was also found in vivo, which was confirmed by histopathology using anti-EGFR antibodies. However, significant mismatch highlights differences between drug delivery in vivo, and cell expression levels of EGFR. CONCLUSIONS: The monoclonal antibody cetuximab represents a promising probe to evaluate the biologic and pharmacokinetic effects of in vivo cetuximab binding to EGFR. It not only visualizes the presence of the wild type EGFR, but also the presence of the mutant EGFRvIII

IEEE Signal Processing Society: Celebrating 75 Years of Remarkable Achievements (Part 2) [From the Guest Editors]

Signal Processing System

IEEE Signal Processing Society: Celebrating 75 Years of Remarkable Achievements [From the Guest Editors]

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Signal Processing System