5-Fluorouracil may enrich cancer stem cells in canine mammary tumor cells in�vitro

Abstract

Mammary gland carcinomas are the most common neoplasms in women and unsterilized female dogs. Owing to the existence of cancer stem cells (CSCs), chemotherapy is not able to cure these types of diseases completely. A number of studies have demonstrated that CSCs are resistant to chemotherapeutic drugs, but whether canine mammary tumor cells that have acquired resistance to 5-fluorouracil (5-FU) exhibited properties of CSCs remains unknown. The aim of the present study was to investigate whether 5-fluorouracil-resistant canine mammary tumor cells exhibited properties of CSCs. CSCs were analyzed using western blot assays, ultra-low attachment sphere cultures, flow cytometry and migration (wound healing and Transwell) assays. The results indicated that, compared with parental cells, proteins associated with the Wnt/β-catenin signaling pathway and aldehyde dehydrogenase 1 were overexpressed, the number and size of spheres in the 5-FU-resistant cells were increased, the ratio of CD44/CD24 cells was increased and the migratory ability was improved compared with the 5-FU-susceptible cells. In conclusion, stimulation with chemotherapeutic drugs including 5-FU is a good method for increasing the proportion of canine mammary tumor stem cells, which may provide further understanding of chemotherapeutic methods and CSCs.

CSCs in Breast Cancer—One Size Does Not Fit All: Therapeutic Advances in Targeting Heterogeneous Epithelial and Mesenchymal CSCs

“…Although the exact mechanism by which cytokine secretion promotes CSC enrichment remains incompletely understood, it has been shown that secreted IL-6 activates the JAK1-STAT3 signal cascade in TNBC and promotes OCT-4 gene expression in non-CSCs to convert non-CSCs into E/M CSCs [104]. This may partially explain why TNBC tumors after chemotherapy are highly tumorigenic compared to untreated controls [5,107]. Radiotherapy and surgery have also been shown to enhance NF-κB signaling to fuel the growth and metastasis of residual tumor cells via an autocrine feedback loop [108,109].…”

“…Non-specific chemotherapy remains as first-line treatment for TNBC due to the lack of specific targets. However, chemotherapy is associated with off-target toxicity and the enrichment of cancer stem cells (CSCs) [3,4,5]. This limitation, in combination with the aggressive nature of TNBC, may contribute to the poor prognosis of TNBC in comparison to other breast cancer subtypes.…”

“…CSCs have the capacity to self-renew, differentiate, dedifferentiate, and hibernate [7], capable of initiating new tumors to cause disease relapse [8,9]. Although conventional chemotherapeutic drugs effectively suppress bulk tumor cells, they are ineffective in inhibiting CSCs, and even enrich CSCs following treatment [3,4,5]. CSCs in TNBC are heterogeneous, interconvertible, and respond to chemotherapy differently [10,11,12,13].…”

A Marine Collagen-Based Biomimetic Hydrogel Recapitulates Cancer Stem Cell Niche and Enhances Progression and Chemoresistance in Human Ovarian Cancer

“…In the last decade, various strategies based on conventional 2D cell culture platforms have been implemented to develop methods for CSC enrichment, including density gradient centrifugation [ 73 ]; hypoxia culture [ 22 , 74 ]; chemoradiotherapy stimulation [ 23 , 75 , 76 , 77 ]; side population sorting [ 78 , 79 ]; mesenchymal stem cell secretome cultures [ 80 , 81 ]; and molecule-mediated triggering, such as neural stimulating factor [ 82 ], estrogen [ 83 ], progestin [ 84 ], hypoxia-inducible factor (HIF)-1 [ 85 ], E-cadherin [ 86 ], keratin [ 87 ], poly ADP ribose polymerase (PARP) inhibitors [ 88 ], and hepatocyte growth factor (HGF)/mesenchymal-epithelial transition (c-Met) [ 89 ]. Overall, however, 2D culture conditions provide limited expansion, and the cells tend to lose clonal and differentiation capacity upon long-term passaging.…”

Functional analysis of CD44 variants and xCT in canine tumours

“…CD44 is recognized as a cancer stem cell marker in canine breast tumours, (Barbieri et al., 2015; Du et al., 2017; Zhou et al., 2018) and its expression is also increased in canine leukaemia, melanoma and osteosarcoma (Gelain et al., 2014; Guth et al., 2014; Milovancev et al., 2013). Although it is known that the canine CD44 gene encodes 20 exons, including 10 variant exons, as observed with the human CD44 gene, the expression pattern and role of CD44 isoforms in canine tumours remain unclear (Milde et al., 1994; Motegi et al., 2018).…”