Know Thy Model: Charting Molecular Homology in Stromal Reprogramming Between Canine and Human Mammary Tumors

Abstract

Spontaneous canine simple mammary tumors (CMTs) are often viewed as models of human breast cancer. Cancer-associated stroma (CAS) is central for initiation and progression of human cancer, and is likely to play a key role in canine tumors as well. Until recently, however, canine CAS in general, and in CMT in particular, lacked detailed characterization and it remained unclear how canine and human CAS compare. This void in knowledge regarding canine CAS and the resulting lack of unbiased crossspecies analysis of molecular homologies and differences undermined the validity of the canine model for human disease. To assess stromal reprogramming in canine breast tumors, we have recently established a protocol to specifically isolate and analyze CAS and matched normal stroma from archival, formalin-fixed paraffin embedded (FFPE) clinical tumor samples using laser-capture microdissection followed by next-generation RNA-sequencing. Using this approach, we have analyzed stromal reprogramming in both malignant canine mammary carcinomas (mCAs) as well as benign canine mammary adenomas in a series of studies. Our results demonstrate strong stromal reprogramming in CMTs and identify high-grade molecular homology between human and canine CAS. Here, I aim to give a short background on the value of comparative oncology in general, and spontaneous CMT in particular. This will be followed by a concise review of the current knowledge of stromal reprogramming in both malignant canine mCA and benign adenoma. Finally, I will conclude with insights on highly conserved aspects of stromal reprogramming between CMT and human breast cancer that accentuate the relevance of CAS in CMT as a model for the human disease.

Canine mammary cancer tumour behaviour and patient survival time are associated with collagen fibre characteristics

“…It is well known that cellular migration involves integration into a complex microenvironment, which can be a physiological or pathological process, including regeneration tissues, immune response and tumor progression 12 , 36 – 40 , 56 – 58 . In addition to well-established chemotaxis, the microstructure and physical properties of the extracellular matrix have a significant influence on cell migration via durotaxis 12 , 56 – 58 . This process can be explained as a unidirectional cell migration mechanism in which a cell responds to an extracellular gradient of rigidity, which is important in the process of cell migration and invasion in tumour progression.…”

Triple-Negative Breast Cancer Comparison With Canine Mammary Tumors From Light Microscopy to Molecular Pathology

“…Markkanen et al (94) analyzed CAS and normal stroma from 15 clinical cases using their laser capture microdissection (LCM) coupled with RNA-seq (LCMRNAseq) pipeline to identify stromal reprogramming in canine simple mammary carcinoma on a transcriptome-wide scale. They revealed strong increases in mesenchymal stem cells, gamma delta T-cells, macrophages, plasmoid dendritic cells, and natural killer T-cells in CAS and demonstrated that commonly deranged pathways between canine and human CAS included angiogenesis, epithelialmesenchymal transition, glycolysis, and immune response pathways.…”

“…They showed that TGFbeta signaling, glycolysis, mitotic spindle, epithelial to mesenchymal transition, mTORC1 signaling, unfolded protein response, apical surface, interferon-gamma response and G2M checkpoint demonstrated greatly increased enrichment only in CAS and pathways involving pancreas beta cells, fatty acid metabolism, spermatogenesis, heme metabolism and IL2-STAT5 signaling showing dramatically reduced enrichment only in CAS. Markkanen et al (94) ranked the samples in The Cancer Genome Atlas (TCGA) breast cancer subset (that contains >1000 human tumor samples) analogous to the stromal enrichment scores to compare their canine-derived stromal signature and found that the canine-derived stromal signature was strongly positively associated with the enrichment of human-derived stromal signature of the TCGA breast cancer subset.…”

“…CAFs may enhance TNBC progression by activating TGF-beta (138). Until now, understanding of fibroblast activation and ECM remodeling in CMTs have focused primarily on aSMA-positive myofibroblasts, expression of Tenascin-C (Tn-C), MMPs, and their inhibitors (94). Breast cancer cells secrete factors that propel macrophages toward M2 differentiation.…”

The Expression of Selected Factors Related to T Lymphocyte Activity in Canine Mammary Tumors

“…Canine mammary tumors are an attractive model for translational oncology and might be useful for the evaluation of novel diagnostic and therapeutic applications, including immunotherapy [4,7,8]. Therefore, our objective was to investigate the expression of genes encoding different molecules related to T cell activity, such as co-stimulatory and co-inhibitory ligands that regulate T cell activation, transcription factors, chemokine receptors, and inflammatory cytokines in canine mammary tumors with different malignancy statuses and metastatic potential (benign, malignant, and metastatic).…”