A Novel Small-Molecule Inhibitor of Mcl-1 Blocks Pancreatic Cancer Growth In Vitro and In Vivo

Abstract

Using a high throughput screening (HTS) approach, we have identified and validated several small molecule Mcl-1 inhibitors (SMIs). Here we describe a novel selective Mcl-1 SMI inhibitor, 2 (UMI-77), developed by structure-based chemical modifications of the lead compound 1 (UMI-59). We have characterized the binding of UMI-77 to Mcl-1 by using complementary biochemical, biophysical and computational methods, and determined its antitumor activity against panel of pancreatic cancer (PC) cells and in vivo xenograft model. UMI-77 binds to the BH3 binding groove of Mcl-1 with Ki of 490 nM, showing selectivity over other members of anti-apoptotic Bcl-2 members. UMI-77 inhibits cell growth and induces apoptosis in PC cells in a time and dose-dependent manner, accompanied by cytochrome c release and caspase-3 activation. Co-immunoprecipitation experiments revealed that UMI-77 blocks the heterodimerization of Mcl-1/Bax and Mcl-1/Bak in cells, thus antagonizing the Mcl-1 function. The Bax/Bak-dependent induction of apoptosis was further confirmed by using murine embryonic fibroblasts that are Bax and Bak deficient. In an in vivo BxPC-3 xenograft model, UMI-77 effectively inhibited tumor growth. Western blot analysis in tumor remnants revealed enhancement of pro-apoptotic markers and significant decrease of survivin. Collectively, these promising findings demonstrate the therapeutic potential of Mcl-1 inhibitors against PC and warrant further preclinical investigations.

Myeloid cell leukemia 1 (MCL-1), an unexpected modulator of protein kinase signaling during invasion

“…5 MCL-1 protein levels correlate with outcome, tumor grade and therapeutic resistance in many cancers including those of the hematopoietic system, breast, lung and pancreas. [6][7][8][9][10][11][12] MCL-1 has been validated to participate in neoplastic progression of B-cell lymphomas 13 as well as haematopoietic progenitor/stem cell tumours 14 and accelerate Myc induced myeloid leukaemia. 15 Several studies have also shown that MCL-1 is a barrier to therapeutic sensitivity, including those that target BCL-2 (reviewed in 16 ).…”

Peptide‐Directed Binding for the Discovery of Modulators of α‐Helix‐Mediated Protein–Protein Interactions: Proof‐of‐Concept Studies with the Apoptosis Regulator Mcl‐1

“…[17] Thed eployment of the NoxaB peptide as as caffold for discovering new compounds was envisaged to also impart this selectivity onto the new small-molecule mimics.T oexamine this,weemployed two in vitro FA assays with Bcl-2 and Bcl-x L ,u sing an FITC-tagged Bid peptide as our fluorescent marker. [22] Navitoclax (ABT-263) was employed as apositive control and as an additional indication that the FA assay was performing adequately.…”

BH3 mimetics: Their action and efficacy in cancer chemotherapy

“…MCL-1 UMI-77 inhibits proliferation of pancreatic cancer cells and induces intrinsic apoptotic pathways [70].…”