Differential stromal reprogramming in benign and malignant naturally occurring canine mammary tumours identifies disease-promoting stromal components

Abstract

The importance of cancer-associated stroma (CAS) for initiation and progression of cancer is well accepted. However, as stromal changes in benign forms of naturally occurring tumours are poorly understood, it remains unclear how CAS from benign and malignant tumours compare. Spontaneous canine mammary tumours are viewed as excellent models of human mammary carcinomas (mCA). We have recently reported highly conserved stromal reprogramming between canine and human mCA based on transcriptome analysis of laser-capture-microdissected FFPE specimen. To identify stromal changes between benign and malignant mammary tumours, we have analysed CAS and matched normal stroma from 13 canine mammary adenomas and compared them to 15 canine mCA. Our analyses revealed distinct stromal reprogramming even in small benign tumours. While similarities in stromal reprogramming exist, the CAS signature clearly distinguished adenomas from mCA, suggesting that it may reliably discriminate between benign and malignant tumours. We identified strongly discriminatory genes and found strong differential enrichment in several hallmark signalling pathways between benign and malignant CAS. The distinction between CAS from adenoma and mCA was further substantiated by differential abundance in cellular composition. Finally, to determine key players in CAS reprograming between adenomas and mCA, a network-based gene screening method identified modules of co-expressing genes with distinct expression profile in benign and malignant CAS, and revealed several hub genes as potential molecular drivers in CAS. Given the relevance of canine CAS as a model for the human disease, our approach identifies potential stromal drivers of tumour malignancy with implications for human mCA.\n\nSummary statementRNAsequencing-based analysis of stromal reprogramming between benign and malignant naturally occurring canine mammary tumours identifies potential molecular drivers in cancer-associated stroma that support tumour growth and malignancy.