Polymorphisms in miR-146, miR-149, miR-196, and miR-499 may increase the risk of non-smokers infected with HPV, overexpression of miR-21, miR-181b, miR-184, and miR-345 is associated with malignant transformation, and overexpression of miR-21, miR-34c, 184 and miR-155 promotes proliferation and evasion of apoptosis (205), with miR-21 targeting the tumor suppressor genes PTEN (Phosphatase and Tensin Homolog) and PDCD4 (Programmed Cell Death 4) in some cancers (206). Here, PDCD4 is linked to cancer.