Characterization of novel MPS1 inhibitors with preclinical anticancer activity

Abstract

,5,6,11,12,13 Monopolar spindle 1 (MPS1), a mitotic kinase that is overexpressed in several human cancers, contributes to the alignment of chromosomes to the metaphase plate as well as to the execution of the spindle assembly checkpoint (SAC). Here, we report the identification and functional characterization of three novel inhibitors of MPS1 of two independent structural classes, N-(4-{2- [(2-cyanophenyl) and N-cyclopropyl-4-{8-(isobutylamino)imidazo[1,2-a]pyrazin-3-yl}benzamide (Mps-BAY2b) (two imidazopyrazines). By selectively inactivating MPS1, these small inhibitors can arrest the proliferation of cancer cells, causing their polyploidization and/or their demise. Cancer cells treated with Mps-BAY1 or Mps-BAY2a manifested multiple signs of mitotic perturbation including inefficient chromosomal congression during metaphase, unscheduled SAC inactivation and severe anaphase defects. Videomicroscopic cell fate profiling of histone 2B-green fluorescent protein-expressing cells revealed the capacity of MPS1 inhibitors to subvert the correct timing of mitosis as they induce a premature anaphase entry in the context of misaligned metaphase plates. Hence, in the presence of MPS1 inhibitors, cells either divided in a bipolar (but often asymmetric) manner or entered one or more rounds of abortive mitoses, generating gross aneuploidy and polyploidy, respectively. In both cases, cells ultimately succumbed to the mitotic catastrophe-induced activation of the mitochondrial pathway of apoptosis. Of note, low doses of MPS1 inhibitors and paclitaxel (a microtubular poison) synergized at increasing the frequency of chromosome misalignments and missegregations in the context of SAC inactivation. This resulted in massive polyploidization followed by the activation of mitotic catastrophe. A synergistic interaction between paclitaxel and MPS1 inhibitors could also be demonstrated in vivo, as the combination of these agents efficiently reduced the growth of tumor xenografts and exerted superior antineoplastic effects compared with either compound employed alone. Altogether, these results suggest that MPS1 inhibitors may exert robust anticancer activity, either as standalone therapeutic interventions or combined with microtubule-targeting chemicals. Mitosis is a sophisticated process that ensures the faithful inheritance of the genetic material by the cellular progeny while preventing aneuploidy and chromosomal instability (CIN), two established hallmarks of cancer. 1-3 A set of protein kinases that are collectively known as mitotic kinases, including Aurora kinases (AURKs), mitotic cyclin-dependent kinases (CDKs), Polo-like kinases and monopolar spindle 1 (MPS1), regulates and coordinates multiple aspects of chromosome segregation during mitosis. 4 MPS1 (also known as TTK) is a dual-specificity kinase (meaning that it phosphorylates both serine/threonine and tyrosine residues) with an established role in the proper alignment and orientation of chromosomes on the metaphase plate. 5 MPS1 is a core component of the spindle assembl...

Naturally Occurring Mutations in the MPS1 Gene Predispose Cells to Kinase Inhibitor Drug Resistance

“…Furthermore, MPS1 is also required for chromosome alignment and error correction (3)(4)(5). Thus, following the inhibition of MPS1 kinase activity, cells prematurely exit mitosis with mis-attached/unaligned chromosomes, which causes severe chromosome mis-segregation, aneuploidy, and cell death (6)(7)(8)(9)(10).…”

“…Furthermore, breast cancer cell lines deficient in the tumor-suppressor protein PTEN have been reported to be more sensitive to MPS1 depletion or kinase inhibition (18). As a result, MPS1 has attracted considerable attention as a potential drug target for anticancer therapy, with a number of small-molecule inhibitors recently identified and under development (6)(7)(8)(9)(10)19), or entering the clinic (BAY-1161909; clinical trial ID NCT02138812).…”

Functional characterization of CFI-402257, a potent and selective Mps1/TTK kinase inhibitor, for the treatment of cancer

“…CFI-402257 shows strong antineoplastic activity on a broad panel of human cancer-derived cell lines, and causes effects consistent with depletion or inhibition of Mps1 (4,(9)(10)(11)(12). Oral administration of CFI-402257 as a single agent to mice bearing human cancer xenografts results in inhibition of tumor growth at doses that are well-tolerated.…”

“…Mps1 is also required for chromosome alignment and error correction (6)(7)(8). Inhibition of Mps1 activity causes cells to prematurely exit mitosis with unattached chromosomes, resulting in severe chromosome missegregation, aneuploidy, and ultimately cell death (4,(9)(10)(11)(12). Mps1 is expressed during mitosis in proliferating cells.…”

Predicting drug resistance before it occurs

“…Among these compounds, NMS-P715, MPI-0479605, Mps-BAY2b and Mps1-IN-3 showed promising results in pre-clinical studies with rodent xenograft models. [12][13][14][15] Apart from these pre-clinical compounds, the small-molecule Mps1 inhibitors reversine and AZ3146 have drawn attention as important tools to decipher Mps1 functions in mitosis. 10,16,17 The strategy of targeting kinases with small-molecule kinase inhibitors in cancer therapy has been specifically successful to treat cells overexpressing or containing hyperactivated alleles of the tyrosine kinases BCR-ABL and epidermal growth factor receptor (EGFR) (reviewed in Barouch-Bentov and Sauer 18 ).…”