Transcriptomic and microRNA Profiling Suggest a Candidate RIPPLY1-cfa-miR-187 Relationship in Canine Mammary Gland...

Canine mammary gland tumours (MGT) represent a common malignancy in intact female dogs, with a high metastasis rate approaching 50% and a poor prognosis. However, metastasis-related genes remain largely unelucidated. Accordingly, we aimed to identify differentially expressed mRNAs and miRNAs in primary canine MGT tissues from dogs with or without confirmed metastasis. We compared mRNA and microRNA (miRNA) expression profiles between malignant MGT tissue samples with and without metastasis. Differentially expressed genes and miRNAs were identified using next-generation sequencing and analysed using the Empirical Analysis of DEGs tool within CLC Genomics Workbench. We identified 119 genes and eight miRNAs as differentially expressed in primary MGTs from dogs with confirmed metastasis. The RIPPLY1 gene was significantly downregulated in primary MGT samples with confirmed metastasis and this result was validated by RT-qPCR. The Cancer Genome Atlas (TCGA) database showed decreased RIPPLY1 expression in human breast cancer, supporting its possible relevance to tumour biology. In silico analysis (miRWalk) revealed that miR-187 is a predicted candidate miRNA that may interact with RIPPLY1 and both NGS data and RT-qPCR showed increased cfa-miR-187 expression in primary tumour samples from dogs with confirmed metastasis. The inverse expression pattern of RIPPLY1 and cfa-miR-187, together with RNAhybrid binding prediction, suggests a possible candidate miRNA-mRNA relationship. STRING analysis suggested a possible pathway context involving beta-catenin/TCF-related proteins, but this computational result requires further validation. Based on these findings, we identified RIPPLY1 and cfa-miR-187 as potential candidate transcripts associated with primary canine MGTs from dogs with confirmed metastasis but functional validation is required.