Anti-estrogen Resistance in Human Breast Tumors Is Driven by JAG1-NOTCH4-Dependent Cancer Stem Cell Activity

Abstract

SummaryBreast cancers (BCs) typically express estrogen receptors (ERs) but frequently exhibit de novo or acquired resistance to hormonal therapies. Here, we show that short-term treatment with the anti-estrogens tamoxifen or fulvestrant decrease cell proliferation but increase BC stem cell (BCSC) activity through JAG1-NOTCH4 receptor activation both in patient-derived samples and xenograft (PDX) tumors. In support of this mechanism, we demonstrate that high ALDH1 predicts resistance in women treated with tamoxifen and that a NOTCH4/HES/HEY gene signature predicts for a poor response/prognosis in 2 ER+ patient cohorts. Targeting of NOTCH4 reverses the increase in Notch and BCSC activity induced by anti-estrogens. Importantly, in PDX tumors with acquired tamoxifen resistance, NOTCH4 inhibition reduced BCSC activity. Thus, we establish that BCSC and NOTCH4 activities predict both de novo and acquired tamoxifen resistance and that combining endocrine therapy with targeting JAG1-NOTCH4 overcomes resistance in human breast cancers.

The role of steroid hormones in breast cancer stem cells

“…Estrogen may exert influence on stem cells via paracrine mechanisms because CD44 C CD24 K and ALDH C CSCs have been shown to lack expression of ER or express it at very low levels (Morimoto et al 2009, Harrison et al 2013, Simões et al 2015. Similar to what happens in the normal mammary gland, it has been suggested that estrogen can promote CSC activity of ER K BCSCs by inducing the secretion of paracrine growth factors from ER C cells.…”

“…Moreover, it was established that inhibition of the Notch signalling pathway reduces BCSC activity, and that the Notch4 receptor has a key role in controlling BCSCs (Harrison et al 2010). Recently, our group demonstrated that treating ER C breast cancer cells with endocrine therapies leads to increased Jag1-Notch4 signalling and that combining endocrine therapies with a Notch pathway inhibitor can prevent BCSC enrichment induced by endocrine therapies (Simões et al 2015). Our results suggest that inhibition of Notch signalling can help overcoming endocrine therapy resistance and might prevent recurrence in ER C breast cancer.…”

“…These data confirm that, while endocrine therapies target the differentiated proliferative breast cancer cells, they cannot effectively target the BCSCs. Stem cell activity in ER C tumors is mainly due to a minority population of ER K cells, which cannot be directly targeted by anti-estrogens and therefore might be responsible for resistance and recurrence (Harrison et al 2013, Simões et al 2015. Indeed, circulating tumor cells of ER C primary tumors are in general found to be ER K (Fehm et al 2009).…”

Targeting Cellular Signaling Pathways in Breast Cancer Stem Cells and its Implication for Cancer Treatment

“…Furthermore, Simões et al demonstrated that anti-estrogen therapy using Tamoxifen or Fulvestrant, increased the activity of the BCSCs though activation of NOTCH4-JAG1 axis (88). The same group also showed that a hormone therapy combined with NOTCH4 inhibition, using γ-secretase inhibitor RO4929097, might abrogate anti-estrogen therapy resistance.…”

Therapeutic strategies for targeting cancer stem cells

“…For example, cases of multiple myeloma have displayed abnormal signaling in response to elevated levels of Hedgehog ligand secreted by tumor stromal cells, [9] and upregulated Notch4 signaling has been implicated in drug-resistant breast CSC activity. [10] Like SCs, CSCs are able to repair damaged DNA more quickly and overexpress drug-efflux pumps such as ATP-binding cassette (ABC) transporters. In a glioblastoma model, aberrant Akt signaling contributed to overactivation of the ABC transporter ABCG2 in CSCs, leading to increased drug expulsion and rendering them resistant to mitoxantrone.…”