Abstract
We have previously designed a novel piperidine compound, 3-[(dodecylthiocarbonyl) methyl]glutarimide (DTCM-glutarimide) based on the structure of 9-methylstreptimidone produced by a microorganism. It inhibits LPS-induced iNOS expression and NO production in macrophages. In one hand it inhibits cellular invasion and selectively induces anoikis in mouse melanoma B16-F10 cells. However, its molecular targets have not been elucidated, In the present study, we tried to find the molecular target of DTCM-glutarimide by the analysis of upstream mechanism of anoikis induction and mobility inhibition in melanoma cells. We have also studied its anti-inflammatory activity in mice bearing transplanted hearts. DTCM-glutarimide increased the expression of Bax, decreased that of Bcl-xL, and activated p53 by inhibiting the expression of MDM2, which is a protein inhibiting p53 activity. Upstream of MDM2, we found that DTCM-glutarimide inhibited the Akt activity in terms of suppression of phosphorylation of Thr308 and Ser473. The phosphorylation of Thr308 is catalyzed by the kinase PDK1, but DTCM-glutarimide did not change the level of phosphorylated PDK1. Then, we employed an in vitro assay system using recombinant PDK1, and found that DTCM-glutarimide inhibited the PDK1 enzymatic activity. Thus, DTCM-glutarimide was found to be an inhibitor of PDK1 that inhibits melanoma cell invasion. Moreover, it showed anti-inflammatory activity in vivo. The hearts of BALB/c (H-2d) mice were transplanted to C57BL/6 (H-2b) mice. DTCM-glutarimide at 10-60 mg/kg was given intraperitoneally every day from just before the transplantation. It prolonged the graft survival dose dependently at 10-40 mg/kg, and no toxicity was observed during the experiment even at 60 mg/kg. Thus, DTCM-glutarimide was found to be a new inhibitor of PDK1. Moreover, it inhibited graft rejection in mice without any toxicity. It may be a new anti-inflammatory and anticancer agent.
