Laboratory of Molecular Design
Triple negative breast cancer therapy by specific blocking of microRNA 17
We hypothesize that our paradigm-disrupting microRNA therapeutic designs block cancer-promoting microRNAs strongly and specifically, using a delivery system that targets triple negative breast cancer (TNBC) cells. TNBC cells lack estrogen and progesterone receptors, and Her2, which could be targeted by specifically designed medicines. Chemotherapy is thus the only standard of care, but TNBC comes back after standard chemotherapy, killing its victims in a year or two. TNBC is recognized by FDA as an orphan disease, attacking 40,000 US women in 2016.
Tumor suppressor proteins are reduced in TNBC cells by pathogenic microRNAs. Conventional wisdom holds that only one of the two strands in a microRNA (miRNA) precursor duplex is selected as the active guide strand. The complementary passenger strand is thought to be inactive. Contrary to conventional wisdom, and the knowledge of our competitors, we discovered that a conventional anti-miR-17 guide strand sequence halved the level of tumor suppressor proteins in TNBC cells, instead of increasing them.
When we studied the genetic code of the entire miR-17 precursor, we saw that the conventional anti-miR-17 sequence imitated the miR-17 passenger strand. We found that the miR-17 passenger strand, mimicked by the anti-miR-17, has its own targets in tumor suppressor mRNAs. We discovered a way around passenger strand activity to target miR-17 guide strand effectively in TNBC cells.
Knowing the critical guide strand code letters that we must block, we designed a short, specific, inhibitor sequence free of passenger strand side effects. Our platform for designing potent microRNA inhibitors is covered by our pending PCT patent application. We will pursue three Aims to test our hypothesis.
Aim 1: Increase potency of our miR-17 blocker by substituting other backbones for PNA. We will measure the potency of 12-16mer leads with tight binding ionic backbones, accepted as substrates by RNase H or Ago2, by melting temperature, qPCR, Western blots, and luciferase activity, in three TNBC cell lines.
Aim 2: Test the ability of the strongest anti-miR-17 lead compound to decrease the growth and metastatic behavior of TNBC cells. We will test our leads by cell proliferation, invasion, and migration assays, against a sequence control, in three TNBC cell lines.
Aim 3: Determine off-target effects of the strongest anti-miR-17 lead in one TNBC cell line. We will test hybridization dependent and hybridization independent effects of our leads by microarray expression profiling, proteomics, and miRNA target site analysis against a conventionally designed miR-17 inhibitor and a sequence control.
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