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.
Subject(s)
Animals , Dogs , Female , Hyaluronan Receptors/genetics , Biomarkers, Tumor/genetics , Cell Transformation, Neoplastic/genetics , Cyclooxygenase 2/genetics , Dog Diseases/genetics , Immunohistochemistry/veterinary , Mammary Neoplasms, Animal/genetics , Mammary Neoplasms, Experimental/genetics , Neoplastic Stem Cells/metabolism , Octamer Transcription Factor-3/genetics , ErbB Receptors/genetics , Retrospective StudiesABSTRACT
The participation of viruses in mammary carcinogenesis has been largely studied in animals. A model similar to the mouse mammary tumor virus (MMTV) was previously proposed. Several lines of research supported the participation of MMTV in human breast cancer, but these evidences were contradicted when further research was performed. One major issue was the presence of human endogenous retroviral sequences that confounded results reporting MMTV-like sequences in human breast cancer. To overcome this problem we selected a 660 bp sequence of the MMTV env gene with low homology to endogenous sequences and search for a sequence to it using the polymerase chain reaction (PCR). The sequence was found in 38 of the human breast cancers and in 2 of the normal breasts studied. The sequence was not present in tumors from other organs. It was 90-98 homologous to MMTV and only 18 to human endogenous retrovirus (HERV) K-10. It was also detected in some of the positive tumors by Southern blot hybridization using one of the cloned 660 bp as a probe. Using reverse transcriptase PCR, it was possible to demonstrate that the 660 bp sequence is expressed in the majority of the tumors. Also, preliminary experiments revealed that sequences related to the LTR and gag genes of MMTV were present in the DNA of breast tumors. The origin of the MMTV-like sequences in tumor DNA could be the result of integrated MMTV-like sequences derived from a human mammary virus or may represent unknown endogenous sequences that can only be detected in breast tumors.
Subject(s)
Humans , Animals , Mice , Breast Neoplasms , Retroviridae Infections/genetics , Tumor Virus Infections/genetics , Mammary Neoplasms, Experimental/genetics , Mammary Tumor Virus, Mouse/genetics , Breast Neoplasms , Growth Substances/geneticsABSTRACT
We have studied the involvement of growth factors (GF), their receptors (GF-R) and oncogenes in modulating tumor growth in the medroxyprogesterone acetate (MPA)-induced mammary tumor model in BALB/c mice. We demonstrated the presence of both ligands of the insulin-like growth factor family (IGF-I, IGF-II) and the two types of receptors (IGF-RI, IGF-RII). MPA upregulated IGF-II mRNA and protein levels in hormone-dependent lines (MPA-D). The progression to a hormone-independent phenotype was accompanied by a high constitutive expression of IGF-II and by a significant decrease in IGF-IIR number. An antisense strategy used to evaluate the role of IGF in the MPA-induced growth of epithelial MPA-D cells showed that IGF mediate progestin-induced mammary tumor growth by autocrine/intracrine pathways. We also studied the role of heregulins (HRG), the recently identified ligands for the c-erbB3 and c-erbB4 oncogenes. HRG mRNA expression was restricted to tumors of ductal origin. MPA induced an in vivo up-regulation of HRG expression. Finally, we also found that MPA may be exerting its proliferative effect on MPA-D lines by inhibiting the expression of transforming growth factor beta 1, (TGF-beta 1) and the lack of expression of TGF-beta 1 in hormone-independent tumors may be related to the acquisition of autonomous growth.