Targeting of Rac GTPases blocks the spread of intact human breast cancer.
High expression of Rac small GTPases in invasive breast ductal carcinoma is associated with poor prognosis, but its therapeutic value in human cancers is not clear. The aim of the current study was to determine the response of human primary breast cancers to Rac-based drug treatments ex vivo. Three-dimensional organotypic cultures were used to assess candidate therapeutic avenues in invasive breast cancers. Uniquely, in these primary cultures, the tumour is not disaggregated, with both epithelial and mesenchymal components maintained within a 3-dimensional matrix of type I collagen. EHT 1864, a small molecule inhibitor of Rac GTPases, prevents spread of breast cancers in this setting, and also reduces proliferation at the invading edge. Rac1+ epithelial cells in breast tumours also contain high levels of the phosphorylated form of the transcription factor STAT3. The small molecule Stattic inhibits activation of STAT3 and induces effects similar to those seen with EHT 1864. Pan-Rac inhibition of proliferation precedes down-regulation of STAT3 activity, defining it as the last step in Rac activation during human breast cancer invasion. Our data highlights the potential use of Rac and STAT3 inhibition in treatment of invasive human breast cancer and the benefit of studying novel cancer treatments using 3-dimensional primary tumour tissue explant cultures.
Breakthrough Breast Cancer Research Unit, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom. elad.katz@ed.ac.uk
Elad
E
Katz
Andrew H
AH
Sims
Duncan
D
Sproul
Helen
H
Caldwell
Michael J
MJ
Dixon
Richard R
RR
Meehan
David J
DJ
Harrison
D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation; D005260:Female; D006801:Humans; D058990:Molecular Targeted Therapy; D011753:Pyrones / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics
C506907:EHT 1864; D011753:Pyrones; D011804:Quinolines; C107953:RAC1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D020830:rac1 GTP-Binding Protein