Transcriptional profiling of miRNA levels in mammary tumors from 18 [PyMT x AKXD]F1 sublines. The PyMT strain was FVB/N-TgN(MMTV-PyVT)634Mul. Overall design: Mammary tumor total RNA from mice representing one of 18 AKXD RI strains were pooled to represent each strain and expression profiled using a custom miRNA microarray.