O-Acetyl-GD2 as a Therapeutic Target for Breast Cancer Stem Cells

SynopsisA sugar-lipid molecule called OAcGD2 is a novel marker for breast cancer stem cells. Treatment with anti-OAcGD2 mAb8B6 may have superior anticancer efficacy by targeting cancer stem cells, thereby reducing metastasis and recurrence of cancer.BackgroundCancer stem cells (CSCs) that drive tumor progression and disease recurrence are rare subsets of tumor cells. CSCs are relatively resistant to conventional chemotherapy and radiotherapy. Eradication of CSCs is thus essential to achieve durable responses. GD2 was reported to be a CSC marker in human triple-negative breast cancer, and anti-GD2 immunotherapy showed reduced tumor growth in cell lines. Using a specific anti-OAcGD2 antibody, mAb8D6, we set out to determine whether OAcGD2+ cells exhibit stem cell properties and mAb8D6 can inhibit tumor growth by targeting OAcGD2+CSCs.MethodOAcGD2 expression in patient-derived xenografts (PDXs) of breast cancer was determined by flow cytometric analyses using mAb8D6. The stemness of OAcGD2+ cells isolated by sorting and the effects of mAb8B6 were assessed by CSC growth and mammosphere formation in vitro and tumor growth in vivo using PDX models.ResultWe found that the OAcGD2 expression levels in six PDXs of various molecular subtypes of breast cancer highly correlated with their previously defined CSC markers in these PDXs. The sorted OAcGD2+ cells displayed a greater capacity for mammosphere formation in vitro and tumor initiation in vivo than OAcGD2− cells. In addition, the majority of OAcGD2+ cells were aldehyde dehydrogenase (ALDH+) or CD44hiCD24lo, the known CSC markers in breast cancer. Treatment of PDXs-bearing mice with mAb8B6, but not doxorubicin, suppressed the tumor growth, along with reduced CSCs as assessed by CSC markers and in vivo tumorigenicity. In vitro, mAb8B6 suppressed proliferation and mammosphere formation and induced apoptosis of OAcGD2+ breast cancer cells harvested from PDXs, in a dose-dependent manner. Finally, administration of mAb8B6 in vivo dramatically suppressed tumor growth of OAcGD2+ breast CSCs (BCSCs) with complete tumor abrogation in 3/6 mice.ConclusionOAcGD2 is a novel marker for CSC in various subtypes of breast cancer. Anti-OAcGD2 mAb8B6 directly eradicated OAcGD2+ cells and reduced tumor growth in PDX model. Our data demonstrate the potential of mAb8B6 as a promising immunotherapeutic agent to target BCSCs.

Effect of Cell Culture Medium on the Proliferation and Stemness of CD24-/CD44+ Human Breast Cancer Stem Cells

BACKGROUND: Cancer stem cells (CSCs) is defined as tumor initiating cells within tumor that maintain stemness properties and tumorigenicity. Extracellular pH of CSCs in in vitro condition is important for supporting cell proliferation which may also regulate the expression of stemness markers such as OCT4. This work aimed to examine the effect of cell culture media on the proliferation and stemness of human breast cancer stem cells (BCSCs).METHODS: Human CD24-/CD44+ BCSCs were grown in Dulbecco's Modified Eagle Medium/F-12 (DMEM/F-12) with 15mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), without HEPES and adjusted to pH 7.4, or without HEPES but pH was not adjusted. BCSCs were grown under standard conditions for various days. Viable cell number was measured using trypan blue exclusion, whereas proliferation rate using MTS assay. OCT4 mRNA and protein were analyzed using quantitative real time PCR (qRT-PCR) and Western Blot assay, respectively. In vitro tumorigenic activity was determined using mammosphere formation unit (MFU) assay.RESULTS: Our results showed a higher viable cell number and proliferation of BCSCs in DMEM/F-12 HEPES (-) compared to HEPES (+) medium until 4 day incubation. OCT4 mRNA and protein level, as well as MFU of BCSCs were significantly higher in HEPES (-) compared to HEPES (+) medium on day 2.CONCLUSION: DMEM/F-12 medium without HEPES facilitates CD24-/CD44+ BCSCs to have higher proliferation and stemness on day 2 incubation compared to those with HEPES.KEYWORDS: breast cancer, cancer stem cell, OCT4, stemness, proliferation

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.

Recent advances in targeted nanotherapeutic approaches for breast cancer management

Breast cancer is the most commonly occurring tumor disease worldwide. Breast cancer is currently managed by conventional chemotherapy, which is inadequate in curbing this heterogeneous disease and results in off-site toxic effects, suggesting effective treatment approaches with better therapeutic profiles are needed. This review, therefore, focuses on the recent advancements in delivering therapeutics to the target site using passive and/or active targeted nanodrug-delivery systems to ameliorate endolysosomal escape. In addition, recent strategies in targeting breast cancer stem cells are discussed. The role of naturally cell-secreted nanovesicles (exosomes) in the management of triple-negative breast cancer is also discussed.

Dysregulation of Transcription Factor EB Contributes to Cell Proliferation, Metastasis and Stemness in Breast Cancer

Purpose: TFEB is a key regulator of autophagy-lysosomal biogenesis pathways, while its dysregulation is highly prevalent in various human cancers, but the specific contribution to breast cancer remains poorly understood. The main purpose of this study is to explore the role of TFEB in breast cancer proliferation, metastasis and maintaining breast cancer stem cells (BCSCs) traits, thus uncovering its underlying mechanism.Methods: Bioinformatics, western blotting and immunohistochemical staining were applied to analyze the expression of TFEB in breast cancer. Stable down-regulation TFEB cells were established in MCF-7 and MDA-MB-231 breast cancer cell lines. MTT, clone formation, wound healing, transwell and 3D tumor invasion assays were used to evaluate the proliferation, migration and invasion ability of breast cancer cells. Mammosphere formation, immunocytochemical (ICC) staining were used to detect the effect of down-regulating TFEB on breast cancer stem cells. Results: we demonstrated that higher expression of TFEB was found in breast cancer. TFEB depletion had inhibitory effects on cellular proliferation, migration and invasion of breast cancer cells. Moreover, knockdown TFEB decreased mammosphere formation ability of BCSCs and expression of cancer stem cell markers. Autophagy-lysosomal related proteins were decreased by down regulation of TFEB. Conclusion: we uncovered a critical role of TFEB in breast cancer proliferation and metastasis, and BCSCs self-renewal and stemness. The underlying mechanisms involve in maintaining BCSCs traits, and dysregulating lysosome functions.