PTEN and neoplasm: The most highly expressed miRNA (12% of expression) was miR-21, a known oncogene that represses a variety of tumor suppressors such as PTEN and PCDC4. Other highly expressed miRNAs included the Let-7 family, which is involved in regulating cell proliferation, as well as miR-143, miR-182, miR-148a, and miR-378.