Stable aneuploid tumors cells are more sensitive to TTK inhibition than chromosomally unstable cell lines

Abstract

Inhibition of the spindle assembly checkpoint kinase TTK causes chromosome mis-segregation and tumor cell death. However, high levels of TTK correlate with chromosomal instability (CIN), which can lead to aneuploidy. We show that treatment of tumor cells with the selective small molecule TTK inhibitor NTRC 0066-0 overrides the mitotic checkpoint, irrespective of cell line sensitivity. In stable aneuploid cells NTRC 0066-0 induced acute CIN, whereas in cells with high levels of pre-existing CIN there was only a small additional fraction of cells mis-segregating their chromosomes. In proliferation assays stable aneuploid cells were more sensitive than cell lines with pre-existing CIN. Tetraploids are thought to be an intermediate between diploid and unstable aneuploid cells. TTK inhibitors had the same potency on post-tetraploid and parental diploid cells, which is remarkable because the post-tetraploids are more resistant to mitotic drugs. Finally, we confirm that the reference compound reversine is a TTK inhibitor and like NTRC 0066-0, inhibits the proliferation of patient-derived colorectal cancer organoids. In contrast, treatment with TTK inhibitor did not reduce the viability of non-proliferating T cell acute lymphoblastic leukemia cells samples. Consequently, TTK inhibitor therapy is expected to spare non-dividing cells, and may be used to target stable aneuploid tumors.

TTK Inhibitors as a Targeted Therapy forCTNNB1(β-catenin) Mutant Cancers

“…Supported by positive results from efficacy studies in preclinical models (8,12,14), TTK inhibitors have been positioned as potential new drugs in combination with taxane chemotherapy in TNBC (8,12). Our unbi-ased cell panel screen shows that TTK inhibitors are indeed very effective in TNBC cell lines (8,30), but do not confirm earlier results of TP53 or PTEN targeting (16,17). Instead, our unbiased cell panel profiling indicates that TTK inhibitors may be more effective in cancers characterized by activating mutations in the CTNNB1 gene.…”

“…The compound inhibited the proliferation of a wide variety of cancer cell lines with a potency similar to that of classic cytotoxic agents, and was efficacious in mouse cancer models, without toxicity (8). NTRC 0066-0 only kills proliferating cells, but there is no relationship between cell doubling time and half maximal inhibitory potency (IC 50 ) in cell proliferation assays (8,30). Because cell line profiling is one of the best ways to discover if certain genomic alterations confer drug sensitivity (28), we extended the number of cancer cell lines examined from 45 to 66, and related sensitivity of the cell lines to the presence or absence of mutations in 23 known cancer genes (18).…”

“…1A) indicates that mutant CTNNB1 is not the sole determinant of TTK inhibitor sensitivity. Recently, we showed by time-lapse image analysis of six cancer cell lines from the 66 cancer cell line panel, that chromosomally stable aneuploid cell lines are relatively more sensitive to TTK inhibition than intrinsically chromosomally unstable cell lines (30). Treatment of sensitive cell lines with TTK inhibitors increased the percentage of cells undergoing mis-segregations, which was already maximal in resistant cell lines.…”

“…Treatment of sensitive cell lines with TTK inhibitors increased the percentage of cells undergoing mis-segregations, which was already maximal in resistant cell lines. This suggests that TTK-sensitive lines are more dependent on an active SAC (30). In that study, we used the neardiploid cell line HCT116 that is chromosomally stable and CTNNB1 mutant.…”

Single cell DNA sequencing reveals distinct molecular types of basal cell carcinoma with unique transcriptome features

“…While stably aneuploid cells generally grow slower [11,12], CIN cells often display increased cell death, presumably as a result of the emergence of unfavourable karyotypes [10,13,14].…”