MTH1 promotes mitotic progression to avoid oxidative DNA damage in cancer cells

Abstract

BACKGROUND: We developed MTH1 inhibitors (MTH1i) TH588 and TH1579 showing broad anti-cancer activity, while structurally distinct MTH1i fail to kill cancer cells. Here, we describe a new role of MTH1 in mitosis and the detailed mechanism of action of TH1579 (karonudib) and other structurally distinct MTH1i. MATERIALS AND METHODS: Cancer cell lines or zebrafish embryos were treated with MTH1i or siRNA targeting MTH1 and analysed primarily by live cell and immunofluorescence microscopy, survival assays, DNA fibre or COMET assays. MTH1 and tubulin interactions were analysed in vitro using co-immunoprecipitation and tubulin polymerisation assays. RESULTS: Here, we describe a mitotic role for the MTH1 protein, which binds to tubulin, is required for microtubule polymerisation, correct spindle assembly, mitosis progression and suppression reactive oxygen species (ROS) generation in mitosis. Potent MTH1i display differential abilities to break the MTH1-tubulin interaction and cause mitotic arrest, demonstrating 8-oxodGTPase and mitotic function of MTH1 are mechanistically distinct. TH588 and TH1579 have more profound effect on mitotic arrest than other MTH1i explained by additional direct inhibition of tubulin polymerisation. MTH1i only inhibiting 8-oxodGTPase activity synergize with mitotic poisons. CONCLUSIONS: Efficient MTH1 have a dual mechanism of action: inhibiting mitosis (to generate ROS) and promoting 8-oxodGTP incorporation into DNA during mitotic replication, dependent on ROS generation. Direct inhibition of tubulin polymerisation of TH588 and TH1579 increase their ability to arrest cells and generate ROS in mitosis. Furthermore, non-cytotoxic MTH1 can become effective and increase incorporation of oxidised nucleotides into DNA when combined with sub-therapeutic concentrations of mitotic inhibitors or challenged directly by 8-oxodGTP.

Targeting human MutT homolog 1 (MTH1) for cancer eradication: current progress and perspectives

“…Indeed, it was recently demonstrated that MTH1 could bind tubulin and promote the progression of mitosis in cancer cells. Some MTH1 inhibitors, such as TH588 and TH1579, could block the interaction of MTH1–tubulin, therefore inducing the mitotic arrest of cancer cells 49 . Taken together, the redox balance of the cellular processes involving oxidative metabolism and elimination, the tumorigenic models, off-target possibility and so on, might directly or indirectly determine the outcome of MTH1 inhibitors, complicating it as a viable therapeutic approach for cancer eradication by inhibiting MTH1.…”

AXL and CAV-1 play a role for MTH1 inhibitor TH1579 sensitivity in cutaneous malignant melanoma

“…Recent studies show on one hand that MTH1 is an important target for cancer [14,15,37], whereas on the other hand some studies claim MTH1 inhibition to be nontoxic, thereby questioning the anticancer therapeutic potential of MTH1i [38,39]. We reported that mitotic arrest, elevated ROS and 8-oxodGTP are important for the efficacy of TH1579 and that noncytotoxic MTH1i can show synergistic effects when combined with mitotic arrest agents [40]. Emerging evidence connect mitotic arrest with ROS.…”

Karonudib has potent anti-tumor effects in preclinical models of B-cell lymphoma

“…Here, we demonstrated that all B-cell lymphoma cell lines displayed a pronounced mitotic arrest in response to karonudib treatment, due to aberrant mitotic spindle formation. This may be related to the mechanism of action of karonudib, targeting microtubuli 13 . The transcriptional changes induced by karonudib in lymphoma cell lines supports this hypothesis as the only significant enrichment profiles identified were "spindle formation" and "G 2 /M-arrest".…”

“…This contrasts cancer cells which frequently upregulate MTH1 to compensate for increased ROS with corresponding higher oxidized nucleotide levels 11 , 12 . Furthermore, karonudib has a dual mechanism as it also directly and indirectly can perturb microtubule polymerization dynamics via an emerging role of MTH1 in mitosis 13 , 14 . Inhibition of MTH1 has potent anti-tumor activity in mouse models of colon cancer, malignant melanoma, hepatocellular carcinoma, -lung- and breast cancer 5 , 15 – 18 .…”