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Targeting CXCR1/2 significantly reduces breast cancer stem cell activity and increases the efficacy of inhibiting HER2 via HER2-dependent and -independent mechanisms.

ABSTRACT: PURPOSE:Breast cancer stem-like cells (CSC) are an important therapeutic target as they are predicted to be responsible for tumor initiation, maintenance, and metastases. Interleukin (IL)-8 is upregulated in breast cancer and is associated with poor prognosis. Breast cancer cell line studies indicate that IL-8 via its cognate receptors, CXCR1 and CXCR2, is important in regulating breast CSC activity. We investigated the role of IL-8 in the regulation of CSC activity using patient-derived breast cancers and determined the potential benefit of combining CXCR1/2 inhibition with HER2-targeted therapy. EXPERIMENTAL DESIGN:CSC activity of metastatic and invasive human breast cancers (n = 19) was assessed ex vivo using the mammosphere colony-forming assay. RESULTS:Metastatic fluid IL-8 level correlated directly with mammosphere formation (r = 0.652; P < 0.05; n = 10). Recombinant IL-8 directly increased mammosphere formation/self-renewal in metastatic and invasive breast cancers (n = 17). IL-8 induced activation of EGFR/HER2 and downstream signaling pathways and effects were abrogated by inhibition of SRC, EGFR/HER2, phosphoinositide 3-kinase (PI3K), or MEK. Furthermore, lapatinib, which targets EGFR/HER2, inhibited the mammosphere-promoting effect of IL-8 in both HER2-positive and negative patient-derived cancers. CXCR1/2 inhibition also blocked the effect of IL-8 on mammosphere formation and added to the efficacy of lapatinib in HER2-positive cancers. CONCLUSIONS:These studies establish a role for IL-8 in the regulation of patient-derived breast CSC activity and show that IL-8/CXCR1/2 signaling is partly mediated via a novel SRC and EGFR/HER2-dependent pathway. Combining CXCR1/2 inhibitors with current HER2-targeted therapies has potential as an effective therapeutic strategy to reduce CSC activity in breast cancer and improve the survival of HER2-positive patients.

SUBMITTER: Singh JK

PROVIDER: S-EPMC4868141 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Targeting CXCR1/2 significantly reduces breast cancer stem cell activity and increases the efficacy of inhibiting HER2 via HER2-dependent and -independent mechanisms.

Singh Jagdeep K JK Farnie Gillian G Bundred Nigel J NJ Simões Bruno M BM Shergill Amrita A Landberg Göran G Howell Sacha J SJ Clarke Robert B RB

Clinical cancer research : an official journal of the American Association for Cancer Research 20121113 3

<h4>Purpose</h4>Breast cancer stem-like cells (CSC) are an important therapeutic target as they are predicted to be responsible for tumor initiation, maintenance, and metastases. Interleukin (IL)-8 is upregulated in breast cancer and is associated with poor prognosis. Breast cancer cell line studies indicate that IL-8 via its cognate receptors, CXCR1 and CXCR2, is important in regulating breast CSC activity. We investigated the role of IL-8 in the regulation of CSC activity using patient-derived ...[more]

PMID: 23149820

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Project description:BackgroundIntrinsic or acquired resistance to HER2-targeted therapy is often a problem when small molecule tyrosine kinase inhibitors or antibodies are used to treat patients with HER2 positive breast cancer. Therefore, the identification of new targets and therapies for this patient group is warranted. Activated choline metabolism, characterized by elevated levels of choline-containing compounds, has been previously reported in breast cancer. The glycerophosphodiesterase EDI3 (GPCPD1), which hydrolyses glycerophosphocholine to choline and glycerol-3-phosphate, directly influences choline and phospholipid metabolism, and has been linked to cancer-relevant phenotypes in vitro. While the importance of choline metabolism has been addressed in breast cancer, the role of EDI3 in this cancer type has not been explored.MethodsEDI3 mRNA and protein expression in human breast cancer tissue were investigated using publicly-available Affymetrix gene expression microarray datasets (n = 540) and with immunohistochemistry on a tissue microarray (n = 265), respectively. A panel of breast cancer cell lines of different molecular subtypes were used to investigate expression and activity of EDI3 in vitro. To determine whether EDI3 expression is regulated by HER2 signalling, the effect of pharmacological inhibition and siRNA silencing of HER2, as well as the influence of inhibiting key components of signalling cascades downstream of HER2 were studied. Finally, the influence of silencing and pharmacologically inhibiting EDI3 on viability was investigated in vitro and on tumour growth in vivo.ResultsIn the present study, we show that EDI3 expression is highest in ER-HER2 + human breast tumours, and both expression and activity were also highest in ER-HER2 + breast cancer cell lines. Silencing HER2 using siRNA, as well as inhibiting HER2 signalling with lapatinib decreased EDI3 expression. Pathways downstream of PI3K/Akt/mTOR and GSK3β, and transcription factors, including HIF1α, CREB and STAT3 were identified as relevant in regulating EDI3 expression. Silencing EDI3 preferentially decreased cell viability in the ER-HER2 + cells. Furthermore, silencing or pharmacologically inhibiting EDI3 using dipyridamole in ER-HER2 + cells resistant to HER2-targeted therapy decreased cell viability in vitro and tumour growth in vivo.ConclusionsOur results indicate that EDI3 may be a potential novel therapeutic target in patients with HER2-targeted therapy-resistant ER-HER2 + breast cancer that should be further explored.

Dataset Information

Targeting CXCR1/2 significantly reduces breast cancer stem cell activity and increases the efficacy of inhibiting HER2 via HER2-dependent and -independent mechanisms.

Publications

Targeting CXCR1/2 significantly reduces breast cancer stem cell activity and increases the efficacy of inhibiting HER2 via HER2-dependent and -independent mechanisms.

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