Novel Anti-MetastamiR Therapy for Metastatic Breast Cancer
Rebecca T. Marquez, Emily Binshtok, Amber R. Smith, Garrett Pretz, Liang Xu
Breast cancer patients diagnose with localized disease have a 5-year survival rate of 100%. However, in patients diagnosed after the cancer has spread to other organs (metastacized), the 5-year survival rate dramatically drops to only 24%. Because metastatic disease are unable to envision a long life without breast cancer. We now have the tools to revolutionize therapeutic strategies to treat and, ultimately, cure patients with metastatic breast cancer. Small RNAs, called microRNAs (miRNAs), are powerful regulatory molecules that can inhibit expression and protein production of over 60% of human genes by binding to target genes. Many of the proteins made from miRNA-regulated genes control the ability of cancer cells to move to other tissues in the body. In metastatic cancers, metastasis-promoting miRNAs, or pro-metastasis-inducing genes to become overexpressed providing the drive to send tumor cells to other sites in the body. Research studies have shown that reintroducing anti-metastamiRs back into the cancer cells will reduce the growth and development of metastatic disease in tumor-bearing mice. However, anti-metastamiR delivery can be hindered due to RNA binding proteins that disrupt the miRNA processing pathway resulting in a non-functional miRNA. This study will develop hybrid expression vectors that utilize a pro-metastamiR scaffold sequence and an anti-metastamiR guide sequence for efficient processing and delivery of anti-metastamiRs into metastatic breast cancer cells.
In order to determine which reintroduced miRNAs are functional in breast cancer cells, we developed a luciferase functional assay to measure exogenous miRNA target inhibition for four pro-metastamiRs (miR-21, miR-196a-1, miR-196a-2, miR-10b) and four anti-metastamiRs (miR-34a, miR-146b, miR-200b, miR200b, miR-335). We found pro-metastamiR miR-196a-2 is highly effective at inhibiting ~80% of its target sequence upon reintroduction, while anti-metastmiRs, miR-200b and miR-335, only inhibited less than ~20%. We are currently determining whether miR-200b and miR-335 are dysfunctional due to miRNA processing or target binding. Because miR-196a-2 is effectively delivered to breast cancer cells, we are currently designing miR-196a-2/200b scaffolds for delivery to metastatic breast cancer. Future studies will include using a nanovector have already shown the capability of delivering genes to metastatic lesions with minimal side effects. This project will have a significant impact on cancer therapies by demonstrating the efficacy of mi-RNA-based therapies using nanotechnology for treatment of metastatic breast cancer. Successful completion of this proposal can lead to new therapeutic options for women with metastatic based therapies can alter cellular pathways to reactivate cell death programs. Using miRNA-based therapies in combination with existing therapies, such as chemotherapy or radiation therapy would provide a new way of treating breast cancer patients with drug resistant metastatic disease.