The Role of Breast Cancer Stem Cells in Chemoresistance and Metastasis in Triple-Negative Breast Cancer

Triple negative breast cancer (TNBC) remains an aggressive disease due to the lack of targeted therapies and relatively low rate of response to chemotherapy, which is currently the main treatment modality for TNBC. Breast cancer stem cells (BCSCs) are a small subpopulation of breast tumors and recognized as drivers of tumorigenesis. TNBC tumors are characterized as being enriched for BCSCs. Studies have demonstrated the role of BCSCs as the source of metastatic disease and chemoresistance in TNBC. Multiple targets against BCSCs are now under investigation, with the considerations of either selectively targeting BCSCs or co-targeting BCSCs and non-BCSCs (majority of tumor cells). This review article provides a comprehensive overview of recent advances in the role of BCSCs in TNBC and the identification of cancer stem cell biomarkers, paving the way for the development of new targeted therapies. The review also highlights the resultant discovery of cancer stem cell targets in TNBC and offers summaries of ongoing clinical trials treating chemoresistant breast cancer. We aim to better understand the mutational landscape of BCSCs and explore potential molecular signaling pathways targeting BCSCs to overcome chemoresistance and prevent metastasis in TNBC, ultimately to improve the overall survival of patients with this devastating disease.

Download Full-text

A Systematic Review to Clarify the Prognostic Values of CD44 and CD44+CD24- Phenotype in Triple-Negative Breast Cancer Patients: Lessons Learned and The Road Ahead

Frontiers in Oncology ◽

10.3389/fonc.2021.689839 ◽

2021 ◽

Vol 11 ◽

Author(s):

Mahdi Abdoli Shadbad ◽

Negar Hosseinkhani ◽

Zahra Asadzadeh ◽

Afshin Derakhshani ◽

Noora Karim Ahangar ◽

...

Keyword(s):

Breast Cancer ◽

Stem Cells ◽

Stem Cell ◽

Cancer Stem Cells ◽

Cancer Stem Cell ◽

Triple Negative Breast Cancer ◽

Triple Negative ◽

Cell Phenotype ◽

Stem Cell Markers ◽

Advanced Tumor Stage

As a unique population of tumor bulk, cancer stem cells have been implicated in tumor relapse and chemoresistance in triple-negative breast cancer (TNBC). Therefore, understanding the phenotype of cancer stem cells can pave the way for introducing novel molecular targeted therapies for treating TNBC patients. Preclinical studies have identified CD44+CD24-/low as a cancer stem cell phenotype; however, clinical studies have reported seemingly controversial results regarding the prognostic values of CD44 and CD44+CD24-/low phenotype in TNBC patients. To critically review the clinicopathological significance and prognostic values of CD44 and CD44+CD24-/low phenotype in TNBC patients, the Scopus, Embase, PubMed, and Web of Science databases were systematically searched to obtain the relevant records published before 20 October 2020. Based on nine included studies, CD44 and CD44+CD24-/low phenotype are associated with inferior prognosis in TNBC patients. Moreover, these cancer stem cell markers have been associated with advanced tumor stage, tumor size, higher tumor grade, tumor metastasis, and lymphatic involvement in TNBC patients. Our evidence has also indicated that, unlike the treatment-naïve TNBC patients, the tumoral cells of chemoradiotherapy-treated TNBC patients can upregulate the CD44+CD24-/low phenotype and establish an inverse association with androgen receptor (AR), leading to the inferior prognosis of affected patients. In summary, CD44 and CD44+CD24-/low phenotype can be utilized to determine TNBC patients’ prognosis in the pathology department as a routine practice, and targeting these phenotypes can substantially improve the prognosis of TNBC patients.

Download Full-text

Notch1 regulates breast cancer stem cell function via a non-canonical cleavage-independent pathway

10.1101/2020.02.28.970764 ◽

2020 ◽

Author(s):

Lufei Sui ◽

Suming Wang ◽

Roberto K. Rodriguez ◽

Danielle Sim ◽

Nandita Bhattacharya ◽

...

Keyword(s):

Breast Cancer ◽

Stem Cells ◽

Stem Cell ◽

Cancer Stem Cells ◽

Cancer Stem Cell ◽

Notch Signaling ◽

Triple Negative ◽

Cell Function ◽

Breast Cancer Stem Cells ◽

Tumor Initiation

AbstractCurrent treatment of triple negative breast cancer patients is hindered by a high incidence of chemoresistance (30-50%). The prevailing theory is that resistance and subsequent recurrence is driven by cancer stem cells. Unfortunately, the functional characterization of cancer stem cells at the molecular level is still incomplete. We show here, that within the canonical breast cancer stem cell population, a subset of cells characterized by high Notch1 expression possesses the tumor-initiating property associated with cancer stem cells. Moreover, the tumor initiating property of these high Notch1-expressing breast cancer stem cells is mediated by a cleavage independent Notch signaling pathway culminating in the repression of SIRT1. Of note, the Notch1-mediated repression of SIRT1 is required not only for tumor initiation, but also for chemoresistance in breast cancer stem cells. Strikingly, inhibition of SIRT1 obviates the requirement for Notch1, marking the first example of conferring cancer stem cell function by inhibiting the activity of a single protein. We also demonstrate that progenitor-like mammary epithelial cells, which possess both luminal and basal properties, are also characterized by high Notch1 expression and repression of SIRT1 via the non-canonical pathway. These findings provide the first functional mechanistic requirements for tumor initiation by breast cancer stem cells and suggest that activation of the non-canonical Notch1 pathway is hardwired into tumor-initiating progenitor cells and thus a prerequisite for tumor initiation.Statement of SignificanceWe demonstrate that chemoresistant and tumor-initiating properties of breast cancer stem cells are driven by repression of SIRT1 via non-canonical Notch signaling, suggesting a novel therapeutic strategy for triple negative breast cancer.

Download Full-text

The Role of Serotonin in Breast Cancer Stem Cells

Molecules ◽

10.3390/molecules26113171 ◽

2021 ◽

Vol 26 (11) ◽

pp. 3171

Author(s):

William D. Gwynne ◽

Mirza S. Shakeel ◽

Adele Girgis-Gabardo ◽

John A. Hassell

Keyword(s):

Breast Cancer ◽

Stem Cells ◽

Stem Cell ◽

Cancer Stem Cells ◽

Cancer Stem Cell ◽

Tumor Cell ◽

Breast Tumors ◽

Breast Cancer Stem Cells ◽

Selective Antagonists

Breast tumors were the first tumors of epithelial origin shown to follow the cancer stem cell model. The model proposes that cancer stem cells are uniquely endowed with tumorigenic capacity and that their aberrant differentiation yields non-tumorigenic progeny, which constitute the bulk of the tumor cell population. Breast cancer stem cells resist therapies and seed metastases; thus, they account for breast cancer recurrence. Hence, targeting these cells is essential to achieve durable breast cancer remissions. We identified compounds including selective antagonists of multiple serotonergic system pathway components required for serotonin biosynthesis, transport, activity via multiple 5-HT receptors (5-HTRs), and catabolism that reduce the viability of breast cancer stem cells of both mouse and human origin using multiple orthologous assays. The molecular targets of the selective antagonists are expressed in breast tumors and breast cancer cell lines, which also produce serotonin, implying that it plays a required functional role in these cells. The selective antagonists act synergistically with chemotherapy to shrink mouse mammary tumors and human breast tumor xenografts primarily by inducing programmed tumor cell death. We hypothesize those serotonergic proteins of diverse activity function by common signaling pathways to maintain cancer stem cell viability. Here, we summarize our recent findings and the relevant literature regarding the role of serotonin in breast cancer.

Download Full-text