Micro RNAs and cancer

“The science of miRNAs and related small RNAs will continue to generate new insights into cancer and possible future treatments” said Nobel Laureate Phillip A. Sharp head of the Koch Institute for Integrative Cancer Research at the Massachusetts Institute of Technology, Cambridge, at a press conference presenting some of the miRNAs related talks at the recent 101st AACR conference in Washington DC. One of the presenters at this conference, Sumaiyah Rehman, discussed the effect of a specific microRNA, Mir-21, on trastuzumab (Herceptin) therapy. For Her2/neu positive breast cancer patients, the standard treatment is trastuzumab + chemotherapy but approximately 35% of patients will develop resistance to treatment. Rehman,thinks that the loss of a specific protein PTEN, a tumour suppressor is a key player in the resistance in this group of breast cancers. As miR-21 targets the PTEN mRNA leading to PTEN protein downregulation, the researchers thought that the increased levels of Mir-21 and the reduced levels of PTEN could result in the resistence to trastuzumab. They tested their hypothesis in cell lines which overexpress HER-2 and found that cells with higher levels of Mir-21 had reduced levels of PTEN and were much more resistant to trastuzumab than control cells. These results are supported by results from the clinic which indicated that in Her-2 positive breast cancer patients with higher levels of Mir-21 had a poorer response to Herceptin which also correlated with disease progression.