Soluble‐E‐cadherin activates HER and IAP family members in HER2+ and TNBC human breast cancers

Abstract

Recent literature suggests that sEcad exerts pro-oncogenic effects, possibly acting as a ligand for the human epidermal growth factor family. Here we show that sEcad is a novel candidate protein for drug targeting since it is increased in human and mouse HER2-positive (HER2+) breast tumors, MMTV-PyMT bodily fluids and human cell culture systems. Mechanistically, we show that endogenous sEcad, and to a lesser extent membrane-bound E-cadherin, associates with HER1, HER2, and HER3 in human and MMTV-PyMT mouse HER2+ tumors and with HER1 in triple negative breast cancer (TNBC) specimens. Furthermore, addition of exogenous recombinant human E-cadherin/Fc chimeric protein (rhEcad/Fc; sEcad) to HER2+ MCF-7, SKBR3, and HER2-negative MDA-MB-231 TNBC cells, resulted in sEcad-HER receptor family interactions, activation of HER1–4 and downstream pro-survival signaling, including the MAPK-PI3K/Akt/mTOR pathways and IAP family members. Lastly, we demonstrate that sEcad exerts pro-oncogenic effects via HER signaling, and acts additively with the HER ligand EGF to promote HER2+ breast cancer proliferation and migration, as well as TNBC invasion. Because sEcad associates and activates many of the oncogenic pathways that tumors utilize for growth and survival and serum levels in patients correlates with clinical response, suggests that targeted therapy against sEcad in combination with other therapies may potentially offer a novel therapeutic strategy for the treatment of breast cancers.

Ectodomain-Specific E-Cadherin Antibody Suppresses Skin SCC Growth and Reduces Tumor Grade: A Multitargeted Therapy Modulating RTKs and the PTEN–p53–MDM2 Axis

“…Along these lines, we and others have confirmed that sEcad is a valid oncogenic target in that it is selectively increased in human skin, breast, and prostate cancer tissues and cells, as well as HER2-positive breast tumors and bodily fluids from MMTV-PyMT genetically engineered mice (4,7,8). Importantly, irrespective of E-cadherin status, we have validated that sEcad is functionally involved in skin and breast cancers as it enhances cell proliferation, migration, and invasion, the latter via increasing the production of proinvasive metalloproteinases (MMP; ref.…”

“…For tumor bromodeoxyuridine (BrdUrd) analyses, tissues were stained using an anti-BrdUrd (ab2284; Abcam) antibody, as previously described (4). The proliferation of cells was monitored by a Cell Proliferation ELISA BrdUrd (colorimetric) Kit (Roche), as described previously (4,7,15).…”

“…Moreover, utilizing a variety of HER as well as MEK and PI3K inhibitors, we have confirmed that sEcad signals via this HER-MAPK-PI3K axis to promote skin SCC and breast cancer proliferation, migration, and invasion (4,7). Because of the interdependent relationship between these pro-oncogenic pathways, we sought to determine whether monoclonal antibody targeting of sEcad may tip the balance toward cell death and away from pro-growth by downregulating this axis.…”

“…177437; Nalge Nunc International) were fixed with methanol or 4% formaldehyde, blocked in PBS containing 1% BSA, and incubated with anti-PTEN (sc-9145), MDM2 (sc-812), and p53 antibodies (sc-6243G; Santa Cruz Biotechnology), as previously described (4,7).…”

“…4). Although the molecular mechanisms underlying sEcad-induced pro-oncogenicity are still under investigation, we have previously shown that sEcad interacts with multiple receptor tyrosine kinases (RTK), including the human epidermal growth factor receptors (HER1-3) and insulin-like growth factor-1 receptor (IGF-1R), leading to the phosphorylation of these RTKs and activation of downstream mitogen-activated protein kinase (MAPK)-phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) and inhibitor of apoptosis (IAP) signaling (4,7). Of note, the RTK-MAPK-PI3K/Akt pathway is one of the most potent driving forces promoting tumor progression, and this axis has emerged as one of the most concentrated areas in anticancer drug development.…”