Strictinin, a novel ROR1-inhibitor, represses triple negative breast cancer survival and migration via modulation of PI3K/AKT/GSK3ß activity

PLoS One. 2019 May 31;14(5):e0217789. doi: 10.1371/journal.pone.0217789. eCollection 2019.

Abstract

Triple Negative Breast Cancer (TNBC), the most aggressive subtype of breast cancer, is characterized by the absence of hormone receptors usually targeted by hormone therapies like Tamoxifen. Because therapy success and survival rates for TNBC lag far behind other breast cancer subtypes, there is significant interest in developing novel anti-TNBC agents that can target TNBC specifically, with minimal effects on non-malignant tissue. To this aim, our study describes the anti-TNBC effect of strictinin, an ellagitanin previously isolated from Myrothamnus flabellifolius. Using various in silico and molecular techniques, we characterized the mechanism of action of strictinin in TNBC. Our results suggest strictinin interacts strongly with Receptor Tyrosine Kinase Orphan like 1 (ROR1). ROR1 is an oncofetal receptor highly expressed during development but not in normal adult tissue. It is highly expressed in several human malignancies however, owing to its numerous pro-tumor functions. Via its interaction and inhibition of ROR1, strictinin reduced AKT phosphorylation on ser-473, inhibiting downstream phosphorylation and inhibition of GSK3β. The reduction in AKT phosphorylation also correlated with decreased cell survival and activation of the caspase-mediated intrinsic apoptotic cascade. Strictinin treatment also repressed cell migration and invasion in a beta-catenin independent manner, presumably via the reactivated GSK3ß's repressing effect on microtubule polymerization and focal adhesion turnover. This could be of potential therapeutic interest considering heightened interest in ROR1 and other receptor tyrosine kinases as targets for development of anti-cancer agents. Further studies are needed to validate these findings in other ROR1-expressing malignancies but also in more systemic models of TNBC. Our findings do however underline the potential of strictinin and other ROR1-targeting agents as therapeutic tools to reduce TNBC proliferation, survival and motility.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Cell Line, Tumor
  • Cell Movement / drug effects
  • Cell Proliferation / drug effects*
  • Cell Survival / drug effects
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects
  • Glycogen Synthase Kinase 3 beta / genetics
  • Humans
  • Oncogene Protein v-akt / genetics
  • Phenols / pharmacology*
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphorylation / drug effects
  • Receptor Tyrosine Kinase-like Orphan Receptors / antagonists & inhibitors
  • Receptor Tyrosine Kinase-like Orphan Receptors / genetics*
  • Signal Transduction / drug effects
  • Triple Negative Breast Neoplasms / drug therapy*
  • Triple Negative Breast Neoplasms / genetics
  • Triple Negative Breast Neoplasms / pathology

Substances

  • Phenols
  • strictinin
  • ROR1 protein, human
  • Receptor Tyrosine Kinase-like Orphan Receptors
  • Glycogen Synthase Kinase 3 beta
  • Oncogene Protein v-akt

Grants and funding

Funding was provided through the Milton Lev Faculty Research Fund, an internal grant awarded to Dr. Peethambaran by The University of the Sciences.