J Vet Sci.  2015 Jun;16(2):225-231. 10.4142/jvs.2015.16.2.225.

The potential role of COX-2 in cancer stem cell-mediated canine mammary tumor initiation: an immunohistochemical study

• Huang J
• Zhang D
• Xie F
• Lin D

• KMID: 2164533
• DOI: http://doi.org/10.4142/jvs.2015.16.2.225

Abstract

Increasing evidence suggests that cancer stem cells (CSCs) are responsible for tumor initiation and maintenance. Additionally, it is becoming apparent that cyclooxygenase (COX) signaling is associated with canine mammary tumor development. The goals of the present study were to investigate COX-2 expression patterns and their effect on CSC-mediated tumor initiation in primary canine mammary tissues and tumorsphere models using immunohistochemistry. Patterns of COX-2, CD44, octamer-binding transcription factor (Oct)-3/4, and epidermal growth factor receptor (EGFR) expression were examined in malignant mammary tumor (MMT) samples and analyzed in terms of clinicopathological characteristics. COX-2 and Oct-3/4 expression was higher in MMTs compared to other histological samples with heterogeneous patterns. In MMTs, COX-2 expression correlated with tumor malignancy features. Significant associations between COX-2, CD44, and EGFR were observed in low-differentiated MMTs. Comparative analysis showed that the levels of COX-2, CD44, and Oct-3/4 expression varied significantly among TSs of three histological grades. Enhanced COX-2 staining was consistently observed in TSs. Similar levels of staining intensity were found for CD44 and Oct-3/4, but EGFR expression was weak. Our findings indicate the potential role of COX-2 in CSC-mediated tumor initiation, and suggest that COX-2 inhibition may help treat canine mammary tumors by targeting CSCs.

Keyword

cancer stem cells; canine mammary tumor; COX-2; tumor initiation

MeSH Terms

Animals
Antigens, CD44/genetics/metabolism
Biomarkers, Tumor/genetics/metabolism
Cell Transformation, Neoplastic/*genetics/metabolism
Cyclooxygenase 2/*genetics/metabolism
Dog Diseases/*genetics/metabolism
Dogs
Female
Immunohistochemistry/veterinary
Mammary Neoplasms, Animal/*genetics/metabolism
Mammary Neoplasms, Experimental/*genetics/metabolism
Neoplastic Stem Cells/*metabolism
Octamer Transcription Factor-3/genetics/metabolism
Receptor, Epidermal Growth Factor/genetics/metabolism
Retrospective Studies
Antigens, CD44
Biomarkers, Tumor
Cyclooxygenase 2
Octamer Transcription Factor-3
Receptor, Epidermal Growth Factor

Figure

• 

  Fig. 1 Immunostaining for COX-2, Oct-3/4, CD44, and EGFR in canine mammary carcinoma. (A) Strong cytoplasmic COX-2 expression in the invasive components of ductal carcinoma with sporadic nucleic labeling. (B) Homogeneous nucleic expression of Oct-3/4 in well-differentiated simple carcinoma. (C) Predominant membrane expression of CD44 in ductal carcinoma. (D) Strong membrane and cytoplasmic expression of EGFR in tubulopapillary carcinoma with apical labeling in luminal cells. Scale bar = 50 µm.

• 

  Fig. 2 Immunolabeling of COX-2, CD44, Oct-3/4, and EGFR in tumorspheres (TSs). TSs generated from primary tumor tissues were compactly aggregated with a regular or irregular appearance. Heterogeneous patterns of COX-2 expression in the cytoplasm and nucleus were observed in all three TSs. Intensity of COX-2 expression in the TSs was elevated in a manner corresponding to primary tumor malignancy (histological grade) along with similar intensities of membrane CD44 and nucleic Oct-3/4 staining. Additionally, EGFR was absent or weakly expressed in all samples. Asterisks indicate a significant difference in IHC scores between PD (n = 8) vs. MD (n = 9) vs. WD (n = 7) primary tumor-derived TSs (p < 0.01). Scale bar = 50 µm (TS) or 20 µm (EGFR).

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