Immunotherapeutic Targeting of Membrane Hsp70-expressing Tumors Using Recombinant Human Granzyme B

PLoS One. 2012;7(7):e41341. doi: 10.1371/journal.pone.0041341. Epub 2012 Jul 19.


Background: We have previously reported that human recombinant granzyme B (grB) mediates apoptosis in membrane heat shock protein 70 (Hsp70)-positive tumor cells in a perforin-independent manner.

Methodology/principal findings: Optical imaging of uptake kinetics revealed co-localization of grB with recycling endosomes (Rab9/11) as early as 5 min after internalization, with late endosomes (Rab7) after 30 min, and the lysosomal compartment (LAMP1/2) after 60 to 120 min. Active caspase-3-mediated apoptosis was induced in mouse CT26 monolayer cells and 3D tumor spheroids, but not in normal mouse endothelial cells. Granzyme B selectively reduced the proportion of membrane Hsp70-positive cells in CT26 tumor spheroids. Consecutive i.v. injections of recombinant human grB into mice bearing membrane Hsp70-positive CT26 tumors resulted in significant tumor suppression, and a detailed inspection of normal mouse organs revealed that the administration of anti-tumoral concentrations of grB elicited no clinicopathological changes.

Conclusions/significance: These findings support the future clinical evaluation of human grB as a potential adjuvant therapeutic agent, especially for treating immunosuppressed patients that bear membrane Hsp70-positive tumors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Camptothecin / metabolism
  • Cell Line, Tumor
  • Cells, Cultured
  • Endothelial Cells / drug effects
  • Flow Cytometry
  • Granzymes / pharmacology
  • Granzymes / therapeutic use*
  • HSP70 Heat-Shock Proteins / metabolism*
  • Humans
  • In Vitro Techniques
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Confocal
  • Recombinant Proteins / pharmacology
  • Recombinant Proteins / therapeutic use
  • Xenograft Model Antitumor Assays


  • HSP70 Heat-Shock Proteins
  • Recombinant Proteins
  • Granzymes
  • Camptothecin