Chemotherapy enriches for an invasive triple-negative breast tumor cell subpopulation expressing a precursor form of N-cadherin on the cell surface

Abstract

BackgroundAlthough most triple-negative breast cancer (TNBC) patients initially respond to chemotherapy, residual tumor cells frequently persist and drive recurrent tumor growth. Previous studies from our laboratory and others' indicate that TNBC is heterogeneous, being composed of chemo-sensitive and chemo-resistant tumor cell subpopulations. In the current work, we studied the invasive behaviors of chemo-resistant TNBC, and sought to identify markers of invasion in chemo-residual TNBC.MethodsThe invasive behavior of TNBC tumor cells surviving short-term chemotherapy treatment in vitro was studied using transwell invasion assays and an experimental metastasis model. mRNA expression levels of neural cadherin (N-cadherin), an adhesion molecule that promotes invasion, was assessed by PCR. Expression of N-cadherin and its precursor form (pro-N-cadherin) was assessed by immunoblotting and flow cytometry. Pro-N-cadherin immunohistochemistry was performed on tumors obtained from patients pre- and post- neoadjuvant chemotherapy treatment.ResultsTNBC cells surviving short-term chemotherapy treatment exhibited increased invasive behavior and capacity to colonize metastatic sites compared to untreated tumor cells. The invasive behavior of chemo-resistant cells was associated with their increased cell surface expression of precursor N-cadherin (pro-N-cadherin). An antibody specific for the precursor domain of N-cadherin inhibited invasion of chemo-resistant TNBC cells. To begin to validate our findings in humans, we showed that the percent cell surface pro-N-cadherin (+) tumor cells increased in patients post- chemotherapy treatment.ConclusionsTNBC cells surviving short-term chemotherapy treatment are more invasive than bulk tumor cells. Cell surface pro-N-cadherin expression is associated with the invasive and chemo-resistant behaviors of this tumor cell subset. Our findings indicate the importance of future studies determining the value of cell surface pro-N-cadherin as: 1) a biomarker for TNBC recurrence and 2) a therapeutic target for eliminating chemo-residual disease.

Suppression of Tumor Growth, Metastasis, and Signaling Pathways by Reducing FOXM1 Activity in Triple Negative Breast Cancer

“…All experiments involving animals were conducted in accordance with National Institutes of Health (NIH, Bethesda, MD, USA) standards for the care and use of animals, with protocols approved by the University of Illinois IACUC (IACUC Protocol 20111). To study the effects of FOXM1 inhibitory compounds on breast tumor growth and metastasis, intact female NOD-SCID-gamma (NSG) mice (8 weeks of age, from Jackson Labs, Bar Harbor, ME, USA) were used as detailed previously [ 40 ]. MDA-MB-231 and DT28 luciferase expressing breast cancer cells were generated using previously described methods [ 41 ].…”

“…The extent of metastasis was followed using an IVIS Spectrum CT imaging system. Animals were injected intraperitoneally with D-luciferin (Regis Technologies, Morton Grove, IL, USA) at 150 mg/kg mouse body weight; luciferase activity was measured, and bioluminescence was quantified using Living Image software (PerkinElmer, Waltham, MA, USA) as previously described [ 40 ]. To measure the metastatic burden, the primary tumor was covered with a black box to prevent signal saturation and inaccurate measurement of metastasis, and bioluminescence was monitored.…”

Synergistic antitumor effects of 9.2.27-PE38KDEL and ABT-737 in primary and metastatic brain tumors

“…Human melanoma cell lines (DM440 and DM443) [31] were kindly provided by Dr. Douglas S. Tyler at Duke University. Human breast cancer cell lines (SUM159, SUM159-R113, and Hs 578T) [32] were kindly provided by Dr. Robin Bachelder at Duke University. All cells were cultured in an incubator at 37°C, 5% CO 2 , and passaged when reached confluence with Accutase Cell Detachment Solution (BD Biosciences #561527).…”

<p>Histone deacetylase inhibitors reinforce the phenotypical markers of breast epithelial or mesenchymal cancer cells but inhibit their migratory properties</p>

“…TNBC cells that survived short-term treatment with docetaxel exhibit a more invasive behavior than pre-treated cells, these selected cell population had an increase in cell surface expression of N-cadherin precursor 35. Likewise, human cancer samples obtained from patients postchemotherapy support such observation as N-cadherin signaling potentiates mammary tumor metastasis via enhanced extracellular signal-regulated kinase (ERK) and Akt kinase activation 35–37. Yet, suppression of E-cadherin in BC (MDA-MB-468) xenografts significantly reduced tumor growth, suggesting an important role of E-cadherin in cancer cell proliferation.…”