P3-17-03: ADAM17: A Novel Therapeutic Target for Treatment of Triple Negative Breast Cancer.
Authors: McGowan PM , Mullooly M , Sukor S , Madden S , McDermott E , Pierce A , Crown J , O'Donovan N , Duffy MJ 
Published: June 2012

Background: Due to the absence of ER, PR and HER2, targeted therapy is currently unavailable for patients with triple negative breast cancer (TNBC). Although TNBC lack overexpression of HER2, HER1, or EGFR, signaling is active in at least a subset of these cancers. Activation of EGFR is initiated by ADAM17-mediated release of ligands such as EGF, TGFa and HB-EGF. The aim of this study was to test the hypothesis that inhibition of ADAM17 is a novel approach for the treatment of TNBC.

Methods: Gene expression data sets were analyzed for ADAM17 expression (3,519 samples across 21 datasets incorporating 10 different microarrays). We used the ADAM17 specific inhibitor, WAY-180022 (WAY: Pfizer), the EGFR inhibitor gefitinib and 5-fluorouracil (5FU) (Sigma Aldrich) to determine their effects on the growth of 7 TNBC cell lines (MDA-MB-231, MDA-MB-468, SUM159PT, HCC1937, BT20, Hs578t, Hs578i) and 6 non-TNBC cell lines (MCF7, T47D, BT474, JIMT-1, SKBR3, MDA-MB-453). Growth inhibitory effects were determined by cell counts and by MTT cell viability assay (Roche), following 5 days post treatment. Levels of TGF alpha were measured by ELISA in conditioned media from cells treated with 1μM WAY for 24 hours. Levels of pEGFR were also measured by ELISA.

Results: We analyzed expression of ADAM17 across molecular subtypes for breast cancer. Levels of ADAM17 mRNA were significantly elevated in the basal like subtype (most of which were TNBC) compared to luminal A, luminal B or HER2 positive breast cancers. In vitro, treatment with WAY-180022 alone resulted in growth inhibitory effects ranging from 15 −49 %in TNBC cells as determined by cell counts. By MTT viability assay, treatment with 1 μM WAY resulted in a significant reduction in cell proliferation compared to vehicle control in MDA-MB-231 (p = 0.007) cells. Addition of WAY to gefitinib resulted in a significant reduction in proliferation in MDA-MB-231 cells compared to either gefitinib or WAY alone (p = 0.017 and p = 0.003, respectively). Similarly, addition of WAY to 5FU resulted in a significant inhibitory effect compared to 5FU alone in MDA-MB-468 (p = 0.007) cells.

Investigating the functional effects of ADAM17 inhibition on breast cancer cells, we found that levels of pEGFR were reduced by between 26–57.6% in 5 of 6 lines examined. pEGFR levels were significantly reduced in MDA-MB-468 (p = 0.01) and MDA-MB-231 (p = 0.01) cells. In addition, levels of TGFα were significantly reduced following treatment with 1 μM WAY (MDA-MB-468, p = 0.008; MDA-MB-231, p = 0.012; HCC1143, p = 0.033; Hs578i8, p = 0.036). Conclusion: Based on our findings, inhibition of ADAM17 with WAY-180022 is a potential treatment for patients with TNBC.

Acknowledgement: The authors wish to thank Science Foundation Ireland, Strategic Research Cluster award (08/SRC/B1410) to Molecular Therapeutics for Cancer Ireland and the Health Research Board Clinician Scientist Award (CSA/2007/11) for funding this work.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-17-03.