Multitarget inhibition of drug-resistant multiple myeloma cell lines by dimethyl-celecoxib (DMC), a non-COX-2 inhibitory analog of celecoxib

2,5-dimethyl-celecoxib (DMC) is a close structural analog of the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib that lacks COX-2 inhibitory function. We and others have demonstrated that DMC, despite its inability to block COX-2, is able to potently mimic the antitumor effects of celecoxib in vitro and in vivo. In this current study, we investigated whether DMC would also be able to inhibit the growth of highly drug-resistant tumor cell variants. We focused on human multiple myeloma (MM) cells, as patients with MM frequently develop drug-resistant disease and ultimately succumb to death. Here we show that DMC (and celecoxib) inhibits the proliferation of various multiple myeloma cell lines, including several (multi) drug-resistant variants. Growth inhibition in drug-sensitive and drug-resistant cells is mediated via multiple effects, which include diminished signal transducer and activator of transcription 3 (STAT-3) and mitogen-activated protein (MAP) kinase kinase (MEK) activity, reduced expression of survivin and various cyclins, and is followed by apoptotic cell death. Thus, our study demonstrates that inhibition of proliferation and induction of apoptosis by DMC (and celecoxib) can be accomplished even in highly drug-resistant multiple myeloma cells, and that this effect is achieved via the blockage of multiple targets that are critical for multiple myeloma cell growth and survival.