Preclinical evaluation of the nonsteroidal anti‐inflammatory agent celecoxib on malignant mesothelioma chemoprevention

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Abstract
Malignant mesothelioma (MM) remains the most lethal pleural, peritoneal and pericardial cancer. Here, we characterize the effects of nonsteroidal anti‐inflammatory agents (NSAIDs) on in vitro and in vivo experimental MM models. Unlike primary normal mesothelial cells, the selective cyclooxygenase (COX)‐2 inhibitor celecoxib reduced the in vitro proliferation of several MM cells derived from previously untreated MM patients. Moreover, celecoxib significantly inhibited MM cell colony formation in soft agarose (63–78% at 5 × 10−5 M; p ≤ 0.05) and it elicited remarkable antitumor activity, leading to long‐term survival in >37% of nude mice bearing intraperitoneal MM. Celecoxib was more efficient in inhibiting MM cell growth than acetylsalicylic acid (10−6 M‐10−2 M), indometacin (10−6 M‐10−2 M) and the COX‐2 inhibitor NS‐398 (10−6 M‐10−4 M). Efficacy of these different compounds was not related to the amount of COX‐2 protein levels present on MM cells. Celecoxib, in a dose‐ and time‐dependent manner, induced MM cell apoptosis, which involved decreased Akt phosphorylation, loss of Bcl‐2 and Survivin protein expression and caspase‐3 activation. Furthermore, vascular endothelial growth factor (VEGF), an MM autocrine growth factor and Akt inducer, rescued celecoxib‐induced apoptosis and Akt dephosphorylation. When the VEGF receptor (KDR/Flk‐1) inhibitor, SU‐1498, was used in combination with celecoxib, IC50 of celecoxib in vitro was reduced up to 65%. These data demonstrate that celecoxib may have antitumor properties in MM and provide a rationale for the therapeutic use of celecoxib in combination with a selective VEGF inhibitor.