TGF-beta1 causes epithelial-mesenchymal transition in HaCaT derivatives, but induces expression of COX-2 and migration only in benign, not in malignant keratinocytes.
BACKGROUND
Transforming growth factor beta (TGF-beta) acts as a tumor promoter by inducing epithelial-mesenchymal transition (EMT), which leads to a motile phenotype, enabling invasion and metastasis of cancer cells. Cancer-related inflammation, mediated by prostaglandins, has been proposed as a critical mechanism in conversion of benign cells to malignant.


OBJECTIVE
Induction of cyclooxygenase 2 (COX-2), producer of prostaglandins, is thought to be a prerequisite for TGF-beta-induced EMT in benign cells. We used HaCaT derivatives, representative of skin cancer progression, to investigate TGF-beta1 mediated EMT response, and the role of COX-2 in it.


METHODS
Effect of TGF-beta1 was investigated by analyzing cell proliferation, morphology and protein expression. Chemotaxis and scratch-wound assays were used to study migration.


RESULTS
TGF-beta1 caused proliferation arrest of benign and malignant HaCaT cells, and changed the epithelial morphology of benign and low-grade malignant cells, but not metastatic cells, to mesenchymal spindle-shape. Epithelial junction proteins ZO-1 and E-cadherin were downregulated in all cell lines in response to TGF-beta1, but mesenchymal markers were not induced, suggesting a partial EMT response. COX-2 and migration were induced only in benign HaCaT derivatives. Malignant derivatives did not induce COX-2 in response to TGF-beta 1 treatment, thus emphasizing the role of inflammation in EMT response of benign cells.


CONCLUSIONS
TGF-beta1 operates via distinct mechanisms in inducing EMT and metastasis, and supporting this we show that TGF-beta1 induces COX-2 and promotes the migration of benign cells, but does not further augment the migration of malignant cells, indicating their resistance to TGF-beta1 in the context of motility.
Räsänen
Kati
K
Haartman Institute, POB 21, FI-00014 University of Helsinki, Finland. kati.rasanen@helsinki.fi
Vaheri
Antti
A
D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D002633:Chemotaxis; D004848:Epithelium / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D015603:Keratinocytes / Q000378:metabolism*; D008648:Mesoderm / Q000378:metabolism*; D008954:Models, Biological; D009362:Neoplasm Metastasis; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000502:physiology*; D014945:Wound Healing
D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1