The synthesis and antiproliferative activity of Mes-and iPr-substituted gold(I) bis(1,2,3-triazol-5-ylidene) complexes in various cancer cell lines are reported, showing nanomolar IC 50 values of 50 nM (lymphoma cells) and 500 nM (leukemia cells), respectively (Mes < iPr). The compounds exclusively induce apoptosis (50 nM to 5 μM) instead of necrosis in common malignant blood cells (leukemia cells) and do not affect non-malignant leucocytes. Remarkably, the complexes not only overcome resistances against the well-established cytostatic etoposide, cytarabine, daunorubicin, and cisplatin but also promote a synergistic effect of up to 182% when used with daunorubicin. The present results demonstrate that gold(I) bis(1,2,3-triazol-5-ylidene) complexes are highly promising and easily modifiable anticancer metallodrugs.
Colchicine, the main
active alkaloid from Colchicum
autumnale L., is a potent tubulin binder and represents
an interesting lead structure for the development of potential anticancer
chemotherapeutics. We report on the synthesis and investigation of
potentially reactive colchicinoids and their surprising biological
activities. In particular, the previously undescribed colchicinoid
PT-100, a B-ring contracted 6-exo-methylene colchicinoid, exhibits
extraordinarily high antiproliferative and apoptosis-inducing effects
on various types of cancer cell lines like acute lymphoblastic leukemia
(Nalm6), acute myeloid leukemia (HL-60), Burkitt-like lymphoma (BJAB),
human melanoma (MelHO), and human breast adenocarcinoma (MCF7) cells
at low nanomolar concentrations. Apoptosis induction proved to be
especially high in multidrug-resistant Nalm6-derived cancer cell lines,
while healthy human leukocytes and hepatocytes were not affected by
the concentration range studied. Furthermore, caspase-independent
initiation of apoptosis via an intrinsic pathway was observed. PT-100
also shows strong synergistic effects in combination with vincristine
on BJAB and Nalm6 cells. Cocrystallization of PT-100 with tubulin
dimers revealed its (noncovalent) binding to the colchicine-binding
site of β-tubulin at the interface to the α-subunit. A
pronounced effect of PT-100 on the cytoskeleton morphology was shown
by fluorescence microscopy. While the reactivity of PT-100 as a weak
Michael acceptor toward thiols was chemically proven, it remains unclear
whether this contributes to the remarkable biological properties of
this unusual colchicinoid.
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