5-Keto-3-cyano-2,4-diaminothiophenes as selective maternal embryonic leucine zipper kinase inhibitors.

Maternal embryonic leucine zipper kinase (MELK) is involved in several key cellular processes and displays increased levels of expression in numerous cancer classes (colon, breast, brain, ovary, prostate and lung). Although no selective MELK inhibitors have yet been approved, increasing evidence suggest that inhibition of MELK would constitute a promising approach for cancer therapy. A weak high-throughput screening hit (17, IC50 ≈ 5 µM) with lead-like properties was optimized for MELK inhibition. The early identification of a plausible binding mode by molecular modeling offered guidance in the choice of modifications towards compound 52 which displayed a 98 nM IC50. A good selectivity profile was achieved for a representative member of the series (29) in a 486 protein kinase panel. Future elaboration of 52 has the potential to deliver compounds for further development with chemotherapeutic aims.

MDM2 interacts with NME2 (non-metastatic cells 2, protein) and suppresses the ability of NME2 to negatively regulate cell motility.

MDM2 expression, combined with increased p53 expression, is associated with reduced survival in several cancers, but is particularly of interest in renal cell carcinoma (RCC) where evidence suggests the presence of tissue-specific p53/MDM2 pathway defects. We set out to identify MDM2-interacting proteins in renal cells that could act as mediators/targets of MDM2 oncogenic effects in renal cancers. We identified the non-metastatic cells 2, protein; NME2 (NDPK-B, NM23-B/-H2), a nucleoside diphosphate kinase, as an MDM2-interacting protein using both a proteomic-based strategy [affinity chromatography and tandem mass spectrometry [MS/MS] from HEK293 cells] and a yeast two-hybrid screen of a renal carcinoma cell-derived complementary DNA library. The MDM2-NME2 interaction is highly specific, as NME1 (87.5% amino acid identity) does not interact with MDM2 in yeast. Specific NME proteins display well-documented cell motility and metastasis-suppressing activity. We show that NME2 contributes to motility suppression under conditions where MDM2 is expressed at normal physiological/low levels. However, up-regulation of MDM2 in RCC cells abolishes the ability of NME2 to suppress motility. Significantly, when MDM2 expression is down-regulated in these cells using small interfering RNA, the motility-suppressing activity of NME2 is rescued, confirming that MDM2 expression causes the loss of NME2 cell motility regulatory function. Thus MDM2 up-regulation in renal cancer cells can act in a dominant manner to abrogate the function of a potent suppressor of motility and metastasis. Our studies identify a novel protein-protein interaction between MDM2 and NME2, which suggests a mechanism that could explain the link between MDM2 expression and poor patient survival in RCC.