Actin cytoskeleton participation in the onset of IL-1beta induction of an invasive mesenchymal-like phenotype in epithelial MCF-7 cells.
BACKGROUND
Interleukin 1 beta (IL-1beta) and other inflammatory cytokines are reported to induce phenotypic changes in epithelial breast cancer tumor cells related to increased invasiveness. Mechanisms involved in the process are not well understood.


METHODS
The noninvasive breast cancer epithelial cell line MCF-7 was used to investigate the IL-1beta-induced phenotype. Live cells expressing EGFP-actin were monitored for cell morphology changes and actin cytoskeleton dynamics by time-lapse video microscopy in the presence of IL-1beta and specific inhibitors of actin signaling pathways. Chemotaxis, invasion of Matrigel, MMP activity and expression of S100A4 in cells treated with IL-1beta were assessed by migration assays, zymograms and immunoblots.


RESULTS
Exposure to IL-1beta specifically induced a change in MCF-7 cells from a typical epithelial morphology into elongated cells, showing numerous dynamic actin-rich lamellae and peripheral ruffles characteristic of fibroblasts. These cells could scatter from compact cell colonies and respond to chemoattractants such as the homing-associated chemokine CXCL-12. Pharmacological blockage of actin signaling pathways and negative mutants of RhoGTPases revealed that actin reorganization and enhanced motility are regulated via PI3K/Rac 1 activation. IL-1beta-stimulated cells expressed the metastasis promoter S100A4, increased secretion of active MMP-9 and MMP-2 and invasion of extracellular matrix proteins.


CONCLUSIONS
IL-1beta induces a PI3K/Rac 1-regulated reorganization of the actin cytoskeleton of MCF-7 cells that is required for cell scattering, elongation and migration. The enhanced motility is accompanied by expression of protein markers correlated with invasive behavior.
Franco-Barraza
Janusz
J
Departamento de Biomedicina Molecular, CINVESTAV-IPN, Apartado, México, D.F., México.
Valdivia-Silva
Julio E
JE
Zamudio-Meza
Horacio
H
Castillo
Aida
A
García-Zepeda
Eduardo A
EA
Benítez-Bribiesca
Luis
L
Meza
Isaura
I
D000199:Actins / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism / Q000494:pharmacology*; D008648:Mesoderm / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018715:Microscopy, Video; D009361:Neoplasm Invasiveness / Q000473:pathology; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000378:metabolism; D053573:Receptors, Interleukin-1 Type I / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D000199:Actins; C527276:CXCR4 protein, human; C508590:IL1R1 protein, human; D053583:Interleukin-1beta; C107953:RAC1 protein, human; D019718:Receptors, CXCR4; D053573:Receptors, Interleukin-1 Type I; D011994:Recombinant Proteins; D019869:Phosphatidylinositol 3-Kinases; D020830:rac1 GTP-Binding Protein