In the past decade, miRNAs have been extensively attracted the scientist’s attentions as tumor
suppressors or oncogenes that have been implicated in tumor progression, metastasis and intrinsic
resistance to various cancer therapies. microRNA-21 (miR-21) demonstrates a potential oncogenic function
and targets tumor inhibitor proteins in almost all types of cancer. miR-21 overexpression has been
studied in terms of cell proliferation, migration, invasion, metastasis, and apoptosis regulation. Inhibition
of miRNA expression using antisense technology by various nanovectors of different sizes, shapes
and compositions has been evolved progressively to overcome the barriers confronted by miRNA delivery.
Application of miR-21 antisense oligonucleotides for treating cancerous cells has become a promising
achievement for cancer therapy. Moreover, miR-21 can mediate resistance to radiation and chemotherapy.
The expanding role of miR-21 functions in human cancers with an emphasis on its regulatory
targets and mechanisms, miR-21 related achievements against cancer promotion have been discussed.