miR-34a and miR-15a/16 are co-regulated in non-small cell lung cancer. (A) miR-16 and miR-34a levels in adenocarcinomas and squamous cell carcinomas relative to matched normal tissues. (B) miR-21 levels in the same tumour samples, relative to matched normal tissue. (C) miR-34a and miR-15a/16 are not able to mutually regulate their expression. H2009 cells were transfected with pre-miR-34a (upper panel) or pre-miR-15a/16 (lower panel) and analysed for the expression of the miRNA counterpart or CDK6 mRNA 42 h post-transfection. Values are relative to the value obtained for the control transfected with precursor control (n = 3). *, P < 0.05.