CCND1 and B-cell chronic lymphocytic leukemia: The specific genetic targets of these miRNAs in pituitary neuroendocrine tumours have not been elucidated, but studies in chronic lymphocytic leukaemia (CLL) have shown that loss of miR-15a and miR-16-1, which co-occur as a cluster, allows overexpression of BCL2, while investigations in prostate and non-small-cell lung cancer have reported that downregulation of miR-15a and miR-16-1 results in increased cyclin D1 (CCND1) expression, with each contributing to tumour formation (Cimmino et al. 2005, Bonci et al. 2008, Calin et al. 2008, Bandi et al. 2009, Croce 2009, Salerno et al. 2009).