Strong EGFR signaling in cell line models of ERBB2-amplified breast cancer attenuates response towards ERBB2-targeting drugs

Abstract

Increasing the efficacy of targeted cancer therapies requires the identification of robust biomarkers suitable for patient stratification. This study focused on the identification of molecular mechanisms causing resistance against the anti-ERBB2-directed therapeutic antibodies trastuzumab and pertuzumab presently used to treat patients with ERBB2-amplified breast cancer. Immunohistochemistry and clinical data were evaluated and yielded evidence for the existence of ERBB2-amplified breast cancer with high-level epidermal growth-factor receptor (EGFR) expression as a separate tumor entity. Because the proto-oncogene EGFR tightly interacts with ERBB2 on the protein level, the hypothesis that high-level EGFR expression might contribute to resistance against ERBB2-directed therapies was experimentally validated. SKBR3 and HCC1954 cells were chosen as model systems of EGFR-high/ERBB2-amplified breast cancer and exposed to trastuzumab, pertuzumab and erlotinib, respectively, and in combination. Drug impact was quantified in cell viability assays and on the proteomic level using reverse-phase protein arrays. Phosphoprotein dynamics revealed a significant downregulation of AKT signaling after exposure to trastuzumab, pertuzumab or a coapplication of both antibodies in SKBR3 cells but no concomitant impact on ERK1/2, RB or RPS6 phosphorylation. On the other hand, signaling was fully downregulated in SKBR3 cells after coinhibition of EGFR and ERBB2. Inhibitory effects in HCC1954 cells were driven by erlotinib alone, and a significant upregulation of RPS6 and RB phosphorylation was observed after coincubation with pertuzumab and trastuzumab. In summary, proteomic data suggest that high-level expression of EGFR in ERBB2-amplified breast cancer cells attenuates the effect of anti-ERBB2-directed antibodies. In conclusion, EGFR expression may serve as diagnostic and predictive biomarker to advance personalized treatment concepts of patients with ERBB2-amplified breast cancer.

Targeting Three Distinct HER2 Domains with a Recombinant Antibody Mixture Overcomes Trastuzumab Resistance

“…Pertuzumab is claimed to be able to block EGFR-HER2 heterodimerization, but no effect of pertuzumab on either cell viability and EGFR or HER2 activity was observed in these cell lines (21). On the basis of our results and recent literature, it appears that a subset of breast and gastric cancers with HER2 amplification and high EGFR exists, and that these tumor cells are resistant to the combination of pertuzumabþtrastuzumab or either agent alone due to HER2-EGFR crosstalk (40,41). The three-mAb mixture, due to its effective induction of HER2 degradation, inhibits crosstalk of HER2 with EGFR and its development should be considered for this group of patients.…”

Cationic Polymer Modified Mesoporous Silica Nanoparticles for Targeted siRNA Delivery to HER2+ Breast Cancer

“…Figure 8C shows that 5 intravenous tail vein injections of 1.25 mg siRNA kg −1 , over a period of three weeks significantly inhibited tumor growth, while T-siSCR-NP 10C produced little effect. This response is noteworthy since HCC1954 has been established as resistant to cisplatin, [46] trastuzumab, [47] and pertuzumab) [48] in vitro and/or in mice. We confirmed its resistance in vivo to trastuzumab ( Figure 9 A-B) and trastuzumab and paclitaxel combination (Figure 9C).…”

ErbB2 overexpression upregulates antioxidant enzymes, reduces basal levels of reactive oxygen species, and protects against doxorubicin cardiotoxicity

“…Our previous studies on ErbB2 overexpression in the heart showed a concurrent upregulation of EGFR (62), as this phenomena has been observed in cancer cells with ErbB2 upregulation (22,28). Furthermore, in addition to ErbB2, EGFR is also known to bind and activate Abl kinases in breast cancer cells; consequently, the activities of EGFR cannot be excluded here (59).…”