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Effects of trastuzumab on epidermal growth factor receptor-dependent and -independent human colon cancer cells
Scott K Kuwada1, Courtney L Scaife, Jinqiu Kuang
1Department of Medicine, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112, USA. scott.kuwada@hsc.utah.edu
Abstract:
Little information is available as to the potential role of HER-2 as a therapeutic target in colon cancers, which express much fewer HER-2 receptors than breast cancer cells. Treatment of certain human colon cancer cell lines with the HER-2 inhibitory antibody mAb 4D5 demonstrated a role for HER-2 in mediating proliferation, apoptosis and tumorigenicity. However, only the cell lines that were dependent on autocrine EGFR-mediated cell proliferation were susceptible to the antiproliferative and antitumorigenic effects of HER-2 inhibition. The relative levels of HER-2, EGFR, HER-3 and HER-4 were not predictive of responsiveness to mAb 4D5. Treatment with HER-2 antibodies caused a decrease in HER-2 protein levels in all of the colon cancer cell lines and also significantly decreased EGFR levels but only in the EGFR-dependent cell lines. Treatment with mAb 4D5 caused the rapid ubiquitination and ligand-dependent downregulation of the EGFR in an EGFR-dependent colon cancer cell line. Treatment of athymic mice engrafted with EGFR-dependent colon cancer cells with mAb 4D5 caused tumor regression and a decrease in EGFR tyrosine phosphorylation in the tumor cells. EGFR-independent colon cancer cell xenografts were resistant to mAb 4D5 therapy. Combined inhibition of HER-2 and EGFR caused large areas of necrosis in EGFR-dependent colon cancer xenografts, suggesting a benefit of combined HER-2 and EGFR inhibitor therapy. Predicting clinical responsiveness of human colon cancer cells to anti-HER-2 and anti-EGFR therapy may require demonstration of EGFR tyrosine kinase dependency of the cells.
Insights
HER-2 inhibition impacts colon cancer cell growth, but only those reliant on EGFR signaling respond. Combined HER-2 and EGFR blockade shows promise for treating colon tumors, highlighting EGFR dependency as key for therapeutic success.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- HER-2 (Human Epidermal growth factor Receptor 2) is a therapeutic target in some cancers, but its role in colon cancer is less understood.
- Colon cancers express lower levels of HER-2 compared to breast cancer cells, necessitating investigation into its specific role and therapeutic potential.
Purpose of the Study:
- To investigate the role of HER-2 as a therapeutic target in human colon cancer cell lines.
- To determine the susceptibility of colon cancer cells to HER-2 inhibition based on their dependency on epidermal growth factor receptor (EGFR) signaling.
Main Methods:
- Treatment of colon cancer cell lines with the HER-2 inhibitory antibody mAb 4D5.
- Assessment of proliferation, apoptosis, and tumorigenicity following HER-2 inhibition.
- In vivo studies using athymic mice engrafted with human colon cancer cells to evaluate tumor regression and molecular changes.
- Analysis of HER-2, EGFR, HER-3, and HER-4 protein levels and their correlation with treatment response.
Main Results:
- mAb 4D5 demonstrated a role for HER-2 in colon cancer proliferation, apoptosis, and tumorigenicity.
- Only colon cancer cell lines dependent on autocrine EGFR-mediated proliferation were sensitive to HER-2 inhibition.
- HER-2 antibody treatment decreased HER-2 and EGFR protein levels in EGFR-dependent cell lines.
- In vivo studies showed tumor regression and decreased EGFR phosphorylation in response to mAb 4D5 in EGFR-dependent xenografts.
- Combined HER-2 and EGFR inhibition led to significant necrosis in EGFR-dependent xenografts.
Conclusions:
- HER-2 is a potential therapeutic target in colon cancer, particularly in tumors dependent on EGFR signaling.
- EGFR dependency is a critical factor in predicting responsiveness to anti-HER-2 therapy in colon cancer.
- Combined inhibition of HER-2 and EGFR may offer a synergistic therapeutic benefit for colon cancer patients with EGFR-dependent tumors.
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