Tumor-specific apoptosis caused by deletion of the ERBB3 pseudo-kinase in mouse intestinal epithelium
Daekee Lee, … , Jonathan M. Kurie, David W. Threadgill
Daekee Lee, … , Jonathan M. Kurie, David W. Threadgill
Published August 17, 2009
Citation Information: J Clin Invest. 2009;119(9):2702-2713. https://doi.org/10.1172/JCI36435.
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Research Article Oncology

Tumor-specific apoptosis caused by deletion of the ERBB3 pseudo-kinase in mouse intestinal epithelium

Abstract

Pharmacologic blockade of EGFR or the closely related receptor ERBB2 has modest efficacy against colorectal cancers in the clinic. Although the upregulation of ERBB3, a pseudo-kinase member of the EGFR/ERBB family, is known to contribute to EGFR inhibitor resistance in other cancers, its functions in normal and malignant intestinal epithelium have not been defined. We have shown here that the intestinal epithelium of mice with intestine-specific genetic ablation of Erbb3 exhibits no cytological abnormalities but does exhibit loss of expression of ERBB4 and sensitivity to intestinal damage. By contrast, intestine-specific Erbb3 ablation resulted in almost complete absence of intestinal tumors in the ApcMin mouse model of colon cancer. Unlike nontransformed epithelium lacking ERBB3, intestinal tumors lacking ERBB3 had reduced PI3K/AKT signaling, which led to attenuation of tumorigenesis via a tumor-specific increase in caspase-3–mediated apoptosis. Consistent with the mouse data, which suggest that ERBB3-ERBB4 heterodimers contribute to colon cancer survival, experimentally induced loss of ERBB3 in a KRAS mutant human colon cancer cell line was associated with loss of ERBB4 expression, and siRNA knockdown of either ERBB3 or ERBB4 resulted in elevated levels of apoptosis. These results indicate that the ERBB3 pseudo-kinase has essential roles in supporting intestinal tumorigenesis and suggest that ERBB3 may be a promising target for the treatment of colorectal cancers.

Authors

Daekee Lee, Ming Yu, Eunjung Lee, Hyunok Kim, Yanan Yang, Kyoungmi Kim, Christina Pannicia, Jonathan M. Kurie, David W. Threadgill

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Figure 1

Targeting the Erbb3 locus.

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Targeting the Erbb3 locus. (A) Targeted ES cells containing TK-Neo f...
(A) Targeted ES cells containing TK-Neo flanked by lox71 (open symbols) and loxP (filled symbols) were transfected with a Cre expression vector to generate the Erbb3 null allele without exon 2. A fragment upstream of 5′ homology was used as a probe for Southern blots. The primers (arrowheads) were used for PCR to discern the Erbb3 wild-type and null alleles. (B) Targeted ES cells containing exon 2 flanked with lox71 and loxP were transfected with a Cre expression vector to generate the Erbb3f conditional allele. The Erbb3fd allele, generated by Cre-mediated excision of exon 2 in the Erbb3f allele, was induced by breeding with tissue-specific Cre transgenic lines. (C) PCR genotyping with DNA from ear (Ea), colon (Co), and jejunum (Sij) of Erbb3f mice crossed to Vil-Cre mice. Lane M, 1-kb ladder; Tg, Vil-Cre transgenic mouse. PCR produces a 488-bp product specific for the Erbb3f allele (f), a 354-bp product for the wild-type Erbb3 allele (+), a 235-bp product for the Erbb3 null allele (–), a 193-bp product for the Erbb3fd allele (fd), and a 278-bp product for the Vil-Cre transgene. (D) Tissue extracts from the epithelium of jejunum analyzed by Western blotting with anti-ERBB3, anti-EGFR, anti-ERBB2, and anti-ERBB4 antibodies. (E) Immunofluorescence staining for ERBB3. Representative intestinal sections with wild-type levels of ERBB3 (top) and intestine-specific deletion of ERBB3 (bottom). Staining is shown individually and merged for ERBB3 and the epithelial marker E-cadherin (CDH1). There is background nuclear staining in the ERBB3 mutant tissue. DAPI staining shows locations of nuclei. Original magnification, ×200.