Male sex and advanced age at diagnosis were associated with the worst disease progression. miR-222 was twofold to threefold higher in tall cell papillary carcinomas (P = 0.038). miR-146 (P = 0.016) and miR-221 (P = 0.050) had a positive correlation with thyroglobulin at the time of sampling.
Follicular lesions with partial features of papillary carcinoma all showed low miR-146b levels similar to other non-papillary carcinoma groups, suggesting that they are biologically distinctive from papillary carcinoma. miR-221 and miR-222 also showed higher expression in papillary carcinoma, but with substantial overlaps with the other groups.
It is likely that the negative regulation of p27(Kip1) by miR-221 and miR-222 might also have a role in vivo since we report an inverse correlation between miR-221 and miR-222 up-regulation and down-regulation of the p27(Kip1) protein levels in human thyroid papillary carcinomas.