CD44+/CD24– Cancer Stem Cells Are Associated With Higher Grade of Canine Mammary Carcinomas

Abstract

The CD44þ/CD24-phenotype identifies cancer stem cell (CSC) properties in canine mammary carcinoma (MC); however, the histopathological features associated with this phenotype remain to be elucidated. Here, we determined whether the CD44þ/ CD24-phenotype was associated with hormonal receptor (HR; estrogen receptor [ER] and/or progesterone receptor [PR]) status and/or triple (ER, PR, and human epithelial growth factor receptor 2)-negative (TN) subtype; conventional histological evaluation was also performed. We found that, as single markers, both CD44þ and CD24þ were associated with less aggressive histological types, low grade, and a non-TN subtype; both markers were associated with HR positivity. On the other hand, a CD44þ/CD24-phenotype was associated with higher grade of carcinoma. Therefore, our results suggest that immunohistochemical phenotyping for CD44/CD24 is useful for the evaluation of tumor behavior as well as CSC-like properties in canine MCs. Keywords cancer stem cell, canine mammary carcinoma, CD44, CD24, immunohistochemistryCancer stem cells (CSCs) are capable of self-renewal and asymmetric differentiation, a type of plasticity that directly contributes to tumorigenesis, tumor maintenance, and resistance to therapeutics.13 CSCs in human breast cancer with a CD44þ/CD24-phenotype are associated with poor prognosis.8 Efforts to identify canine CSCs have also revealed a CD44þ/CD24-phenotype in mammary carcinomas (MCs). Specifically, spheroids derived from canine MC cell lines in an in vitro CSC model have high CD44 expression but are negative or low for CD24 expression. 3A previous study reported that the CD44þ/CD24-phenotype was detectable in archival tissues; 10 however, the molecular and histopathological features associated with those markers remain to be elucidated. It is suggested that hormone receptor (HR) status (specifically, the estrogen receptor [ER] and/or progesterone receptor [PR]) and the triple-negative (TN) subtype (ER, PR, and human epidermal growth factor receptor 2 [HER2] negative) are associated with aggressive tumor types in canine MCs. 6,7 We hypothesized that immunohistochemical analysis of the 2 markers, CD44 and CD24, would be a useful tool for predicting tumor behavior. The aims of this study were to examine CD44 and CD24 expression, either alone or in combination, with regard to canine MCs. Specifically, we determined the relationship of these markers with histological findings, HR status, and the TN subtype. Materials and MethodsWe investigated 88 cases of canine MCs from the histopathology database of the Department of Veterinary Pathology, Konkuk University Animal Teaching Hospital, Seoul, Korea. Routine hematoxylin and eosin staining and immunohistochemistry (IHC) were performed as previously described. 6 Classification of histological type and grade was achieved as previously described.4 Double immunostaining for CD44 and CD24 was performed consecutively using immunoperoxidase with DAB for CD44 and immunoalkaline phosphatase with Vector Red substrate for CD24...

Identification and characterization of cancer stem cells in canine mammary tumors

“…The CD44 + /CD24 − phenotype, which is characteristic of CSC, was detected more frequently in higher-grade tumors and lymph node metastases, while the CD24 + phenotype was identified more frequently in lower grade samples (grade I) compared to the other pathologies. Similar results were also demonstrated by other groups concluding that a higher frequency of CD44 + /CD24 − cells is associated with poorer prognosis [37–39]. However, results might be often underestimated due to non-homogenous expression of CD44 within tissue, uneven localization of putative cells and difficulties with serial sectioning of samples [41].…”

“…A few groups have presented promising results using this technique [28, 37–40]. In a large study conducted by Magalhaes et al [39], 130 CMT samples, including benign, malignant and lymph node metastases, were analyzed for CD44 and CD24 expression.…”

Conserved and variable: Understanding mammary stem cells across species

“…Moreover, they generated branching structures on collagen gels and induced tumor growth when implanted into the fat pads of NOD/SCID mice. Similar to CSC derived from human breast tumors, a CD24 –/lo /CD44 + population of CSC has been reported in several canine mammary tumors and cell lines, and was associated with poor prognosis . Canine CSC within the heterogeneous tumor cell line CMT‐U229 were isolated by flow cytometry according to Sca‐1 expression and Hoechst dye exclusion (side population, SP).…”

Salinomycin inhibits canine mammary carcinoma in vitro by targeting cancer stem cells

“…In canines, mammary CSCs are associated with a higher grade of carcinoma and poor prognosis (7,8). In addition, canine mammary CSCs are typically resistant to common cancer therapies (9,15).…”

“…Increasing evidence supports the presence of CSCs in canine mammary tumors (7)(8)(9)(10). Human breast CSCs are primarily characterized by cluster of differentiation (CD)44 + /CD24 -/low cells, sphere formation and active aldehyde dehydrogenase (11).…”