Abstract P4-12-06: Quantification of HER2-driven signaling (HER2S) inhibition of four different anti-HER2 drugs tested ex vivo in live primary HER2-negative breast cancer cell samples with abnormal HER2 signaling activity
Authors: Laing L , Burns D , Huang Y , MacNeil I , Rich B , Myhre S , Soltani S , Sullivan B 
Published: May 2019

Background: A new functional cellular analysis platform, the CELx HER2 Signaling Profile (CELx HSP) Test, uses a label-free impedance biosensor to measure HER2 signaling activity in live tumor cells. A recently completed study quantified HER2-driven signaling activity in epithelial cell samples extracted and cultured from fresh breast tissue specimens obtained from 34 patients with HER2-negative breast cancer (DAKO 0 or 1+). Of the cell samples tested, 7 of 34 HER2-negative breast tumor patients (20.5%; 95% CI=10%-37%) were found to have abnormal HER2 signaling activity (HER2S+). The current study set out to: 1) evaluate the primary cells with abnormal HER2-driven signaling with four HER2 signal inhibitors - pertuzumab, lapatinib, neratinib, afatinib; and 2) evaluate the same four HER2 signal inhibitors with 9 HER2-positive cell lines. The objective was to quantify the percentage of HER2-driven signaling activity each drug could inhibit ex vivo in the primary cell samples and cell lines. Comparing the results between the HER2-negative primary cells and the HER2-positive cell lines was also of interest. The anti-HER2 drug, trastuzumab, was not studied because its primary mechanism of action does not appear to be direct mediation of HER2-driven signaling.

Methods: Epithelial cells from the 7 HER2-negative tumor specimens with abnormal HER2-driven signaling (HER2S+) and the 9 HER2-positive cell lines were obtained. Real time live cell response to NRG1, a specific HER2/HER3 agonist, with or without a HER2 targeted drug (pertuzumab, lapatinib, neratinib, afatinib) was measured and quantified using an xCELLigence RTCA impedance biosensor (ACEA Biosciences, San Diego, CA). Clinically relevant concentrations of the HER2 drugs were used. From these responses, the percentage inhibition of the HER2-driven signaling initiated by NRG1 by the HER2 drugs was determined.

Results: Each of the HER2 drugs inhibited an average of at least 69% of the HER2-driven signaling activated by NRG1 stimulation in the HER2-negative primary cell samples; the highest level of inhibition was found with the two irreversible covalent dual RTKi's, afatinib and neratinib. All of the HER2 drugs inhibited a greater percentage of HER2-driven signaling in the HER2-negative primary tumor cells than in the HER2-positive cell lines.

table 1  Avg. % NRG1 Inhibition  Cell LinesPrimariesHER2 DrugsMechanism of Action(HER2+)(HER2-)PertuzumabHER2 dimerization inhibitor46%78%LapatinibReversible Dual RTKi (HER2, EGF)15%69%AfatinibIrreversible Covalent Dual RTKi (HER2, EGF)47%93%NeratinibIrreversible Covalent Dual RTKi (HER2, EGF)95%100%

Conclusions: These findings provide strong evidence that HER2 signal inhibitors are effective in blocking abnormal levels of HER2-driven signaling (HER2S+) ex vivo in live primary cells from breast cancer patients with normal expression levels of HER2. These results suggest a new group of breast cancer patients, HER2-negative with abnormal HER2 signaling (HER2-/HER2S+), may benefit from the addition of HER2 signal inhibitors to current combination therapeutic regimens. Additional studies to confirm these findings are underway.

Citation Format: Laing L, Burns D, Huang Y, MacNeil I, Rich B, Myhre S, Soltani S, Sullivan B. Quantification of HER2-driven signaling (HER2S) inhibition of four different anti-HER2 drugs tested ex vivo in live primary HER2-negative breast cancer cell samples with abnormal HER2 signaling activity [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-12-06.