Activation of mitochondrial apoptosis pathways in cutaneous squamous cell carcinoma cells by diclofenac/hyaluronic acid is related to upregulation of Bad as well as downregulation of Mcl-1 and Bcl-w.
Actinic keratosis (AK) is characterized by high prevalence and the risk to proceed to squamous cell carcinoma (SCC). Cyclooxygenase-2 (COX-2)-mediated prostaglandin E2 (PGE (2) ) synthesis has been reported in AK and SCC, and the COX inhibitor diclofenac in hyaluronic acid (diclofenac/HA) was approved for AK therapy. Its mode of action, however, remained to be unravelled. In the present study, diclofenac resulted in reduced PGE (2)  levels in apoptosis-sensitive cutaneous SCC cell lines (SCL-II, SCC-12, SCC-13) whereas no PGE (2)  and no COX-2 expression was detectable in a SCC cell line resistant to apoptosis induction (SCL-I). Activation of mitochondrial apoptosis pathways was evident in SCC cells owing to loss of the mitochondrial membrane potential and release of the mitochondrial factors cytochrome c and apoptosis-inducing factor. Characteristic proapoptotic changes at the level of Bcl-2 proteins occurred in sensitive cells, as upregulation of Bad and downregulation of Mcl-1 and Bcl-w. In contrast, Bad was already high, and Mcl-1 and Bcl-w were already low in resistant SCL-I, even without treatment, which may be explained by the lack of PGE (2) . An antiapoptotic downregulation of proapoptotic Bcl-2 proteins Noxa and Puma was, however, also seen in SCL-I, suggesting here pathways independent of COX-2. The regulations of Mcl-1 and Bad were also reproduced in SCC cells by the more selective COX-2 inhibitor celecoxib, thus further underlining the specific role of COX-2. The findings illuminate the mode of action of diclofenac/HA in SCC cells as well as principles of their resistance, which may allow further adaptation and improvement of the new therapy.
Department of Dermatology and Allergy, Skin Cancer Center, University Medical Center Charité, Berlin, Germany.
Paul M
PM
Rodust
Lothar F
LF
Fecker
Eggert
E
Stockfleth
Jürgen
J
Eberle
D017209:Apoptosis / Q000187:drug effects; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins / Q000187:drug effects / Q000378:metabolism; D002294:Carcinoma, Squamous Cell; D000068579:Celecoxib; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D045304:Cytochromes c / Q000378:metabolism; D004008:Diclofenac / Q000494:pharmacology*; D015232:Dinoprostone / Q000378:metabolism*; D015536:Down-Regulation; D006801:Humans; D006820:Hyaluronic Acid / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D012878:Skin Neoplasms; D013449:Sulfonamides / Q000494:pharmacology; D015854:Up-Regulation; D051025:bcl-Associated Death Protein / Q000187:drug effects / Q000378:metabolism
D051033:Apoptosis Inducing Factor; D051017:Apoptosis Regulatory Proteins; C494819:BAD protein, human; C438378:BBC3 protein, human; C491073:BCL2L2 protein, human; D016861:Cyclooxygenase Inhibitors; D064549:Myeloid Cell Leukemia Sequence 1 Protein; C498702:PMAIP1 protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011720:Pyrazoles; D013449:Sulfonamides; D051025:bcl-Associated Death Protein; D004008:Diclofenac; D006820:Hyaluronic Acid; D045304:Cytochromes c; D051546:Cyclooxygenase 2; D000068579:Celecoxib; D015232:Dinoprostone