Targeting RPL39 and MLF2 reduces tumor initiation and metastasis in breast cancer by inhibiting nitric oxide synthase signaling

Proc Natl Acad Sci U S A. 2014 Jun 17;111(24):8838-43. doi: 10.1073/pnas.1320769111. Epub 2014 May 29.


We previously described a gene signature for breast cancer stem cells (BCSCs) derived from patient biopsies. Selective shRNA knockdown identified ribosomal protein L39 (RPL39) and myeloid leukemia factor 2 (MLF2) as the top candidates that affect BCSC self-renewal. Knockdown of RPL39 and MLF2 by specific siRNA nanoparticles in patient-derived and human cancer xenografts reduced tumor volume and lung metastases with a concomitant decrease in BCSCs. RNA deep sequencing identified damaging mutations in both genes. These mutations were confirmed in patient lung metastases (n = 53) and were statistically associated with shorter median time to pulmonary metastasis. Both genes affect the nitric oxide synthase pathway and are altered by hypoxia. These findings support that extensive tumor heterogeneity exists within primary cancers; distinct subpopulations associated with stem-like properties have increased metastatic potential.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / prevention & control
  • Cell Line, Tumor
  • Cell Movement
  • Female
  • Gene Expression Regulation, Neoplastic
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Hypoxia
  • Lung Neoplasms / genetics*
  • Lung Neoplasms / metabolism
  • Mice
  • Mice, SCID
  • Mutation
  • Neoplasm Metastasis
  • Neoplasm Transplantation
  • Neoplastic Stem Cells / cytology*
  • Nitric Oxide / chemistry
  • Nitric Oxide Synthase / antagonists & inhibitors
  • Nitric Oxide Synthase / metabolism*
  • Nuclear Proteins / metabolism*
  • RNA, Small Interfering / metabolism
  • Ribosomal Proteins / metabolism*
  • Sequence Analysis, RNA
  • Signal Transduction
  • Time Factors


  • MLF2 protein, human
  • Nuclear Proteins
  • RNA, Small Interfering
  • RPL39L protein, human
  • Ribosomal Proteins
  • Nitric Oxide
  • Nitric Oxide Synthase