MTH1 Inhibitor TH588 Disturbs Mitotic Progression and Induces Mitosis-Dependent Accumulation of Genomic 8-oxodG

Reactive oxygen species (ROS) oxidize nucleotide triphosphate pools (e.g., 8-oxodGTP), which may kill cells if incorporated into DNA. Whether cancers avoid poisoning from oxidized nucleotides by preventing incorporation via the oxidized purine diphosphatase MTH1 remains under debate. Also, little is known about DNA polymerases incorporating oxidized nucleotides in cells or how oxidized nucleotides in DNA become toxic. Here we show that replacement of one of the main DNA replicases in human cells, DNA polymerase delta (Pol δ), with an error-prone variant allows increased 8-oxodG accumulation into DNA following treatment with TH588, a dual MTH1 inhibitor and microtubule targeting agent. The resulting elevated genomic 8-oxodG correlated with increased cytotoxicity of TH588. Interestingly, no substantial perturbation of replication fork progression was observed, but rather mitotic progression was impaired and mitotic DNA synthesis triggered. Reducing mitotic arrest by reversin treatment prevented accumulation of genomic 8-oxodG and reduced cytotoxicity of TH588, in line with the notion that mitotic arrest is required for ROS buildup and oxidation of the nucleotide pool. Furthermore, delayed mitosis and increased mitotic cell death was observed following TH588 treatment in cells expressing the error-prone but not wild-type Pol δ variant, which is not observed following treatments with antimitotic agents. Collectively, these results link accumulation of genomic oxidized nucleotides with disturbed mitotic progression. SIGNIFICANCE: These findings uncover a novel link between accumulation of genomic 8-oxodG and perturbed mitotic progression in cancer cells, which can be exploited therapeutically using MTH1 inhibitors.See related commentary by Alnajjar and Sweasy, p. 3459.

Abstract 105: MTH1 promotes mitotic progression to avoid oxidative DNA damage in cancer cells

MTH1 prevents incorporation of oxidized deoxynucleoside triphosphates (e.g., 8-oxodGTP) into DNA. Earlier we demonstrated that MTH1 inhibitors TH588 and TH1579 possesses anti-cancer activity in various tumour types, while other structurally distinct MTH1 inhibitors failed to kill cancer cells or elevate the levels of oxidized nucleotides in DNA. In our current study, we found a novel function of MTH1 in mitosis, as it plays an important role in correct spindle assembly in cancer cells and progression through mitosis, and furthermore, we demonstrate MTH1 binds tubulin in vivo. We also observed that structurally distinct MTH1 inhibitors display differential abilities to break the MTH1 tubulin interaction, and also demonstrate that TH588 and TH1579 can directly inhibit tubulin polymerisation in vitro. Consistent with our results, we establish that TH588 and TH1579 kill cancer cells by a mitosis-dependent mechanism and implicate reactive oxygen species (ROS) accumulation and incorporation of oxidised nucleotides into DNA in this process. Furthermore, we found that non-cytotoxic MTH1 inhibitors can become cytotoxic and increase incorporation of oxidised nucleotides into DNA when they are combined with sub-therapeutic concentrations of mitotic inhibitors. In conclusion, MTH1 inhibitors killing cancer cells have a unique and complex mechanism of action: (1) causing a mitotic arrest, induced by targeting MTH1 which is required for mitotic progression, but also through direct inhibition of microtubule polymerisation, in-turn leading to an increase in ROS and likely 8-oxodGTP and (2) MTH1-dependent 8-oxodGTPase inhibitory activity causing incorporation of damaged nucleotides into DNA to kill cancer cells.

Citation Format: Kumar Sanjiv, Helge gad, Sean G. Rudd, Oliver Mortusewicz, Ailine Stolz, Nuno Amaral, Lars Brautigham, Linda Pudelko, Christina Kaldéren, Ann-Sofie Jemth, Ingrid Almlöf, Torkild Visnes, Niklas Schultz, Johan Boström, José Manuel Calderon Montano1, Anna Hagenkort, Petra Groth, Camilla Gokturk, Tobias Koolmeister, Prasad Wakchaure, Evert Homan, Mikael Altun, Cecilia Ström, Martin Scobie, Holger Bastians, Ulrika Warpman Berglund, Thomas Helleday. MTH1 promotes mitotic progression to avoid oxidative DNA damage in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 105.

Germline variation in the oxidative DNA repair genes NUDT1 and OGG1 is not associated with hereditary colorectal cancer or polyposis

The causal association of NUDT1 (=MTH1) and OGG1 with hereditary colorectal cancer (CRC) remains unclear. Here, we sought to provide additional evidence for or against the causal contribution of NUDT1 and OGG1 mutations to hereditary CRC and/or polyposis. Mutational screening was performed using pooled DNA amplification and targeted next-generation sequencing in 529 families (441 uncharacterized MMR-proficient familial nonpolyposis CRC and 88 polyposis cases). Cosegregation, in silico analyses, in vitro functional assays, and case-control associations were carried out to characterize the identified variants. Five heterozygous carriers of novel (n = 1) or rare (n = 4) NUDT1 variants were identified. In vitro deleterious effects were demonstrated for c.143G>A p.G48E (catalytic activity and protein stability) and c.403G>T p.G135W (protein stability), although cosegregation data in the carrier families were inconclusive or nonsupportive. The frequency of missense, loss-of-function, and splice-site NUDT1 variants in our familial CRC cohort was similar to the one observed in cancer-free individuals, suggesting lack of association with CRC predisposition. No OGG1 pathogenic mutations were identified. Our results suggest that the contribution of NUDT1 and OGG1 germline mutations to hereditary CRC and to polyposis is inexistent or, at most, negligible. The inclusion of these genes in routine genetic testing is not recommended.

Nuclear F-actin and myosins drive relocalization of heterochromatic breaks

Heterochromatin mainly comprises repeated DNA sequences that are prone to ectopic recombination. In Drosophila cells, 'safe' repair of heterochromatic double-strand breaks by homologous recombination relies on the relocalization of repair sites to the nuclear periphery before strand invasion. The mechanisms responsible for this movement were unknown. Here we show that relocalization occurs by directed motion along nuclear actin filaments assembled at repair sites by the Arp2/3 complex. Relocalization requires nuclear myosins associated with the heterochromatin repair complex Smc5/6 and the myosin activator Unc45, which is recruited to repair sites by Smc5/6. ARP2/3, actin nucleation and myosins also relocalize heterochromatic double-strand breaks in mouse cells. Defects in this pathway result in impaired heterochromatin repair and chromosome rearrangements. These findings identify de novo nuclear actin filaments and myosins as effectors of chromatin dynamics for heterochromatin repair and stability in multicellular eukaryotes.

Nuclear Dynamics of Heterochromatin Repair

Repairing double-strand breaks (DSBs) is particularly challenging in pericentromeric heterochromatin, where the abundance of repeated sequences exacerbates the risk of ectopic recombination and chromosome rearrangements. Recent studies in Drosophila cells revealed that faithful homologous recombination (HR) repair of heterochromatic DSBs relies on the relocalization of DSBs to the nuclear periphery before Rad51 recruitment. We summarize here the exciting progress in understanding this pathway, including conserved responses in mammalian cells and surprising similarities with mechanisms in yeast that deal with DSBs in distinct sites that are difficult to repair, including other repeated sequences. We will also point out some of the most important open questions in the field and emerging evidence suggesting that deregulating these pathways might have dramatic consequences for human health.

Drosophila PS2 and PS3 integrins play distinct roles in retinal photoreceptors-glia interactions

Cellular migration and differentiation are important developmental processes that require dynamic cellular adhesion. Integrins are heterodimeric transmembrane receptors that play key roles in adhesion plasticity. Here, we explore the developing visual system of Drosophila to study the roles of integrin heterodimers in glia development. Our data show that αPS2 is essential for retinal glia migration from the brain into the eye disc and that glial cells have a role in the maintenance of the fenestrated membrane (Laminin-rich ECM layer) in the disc. Interestingly, the absence of glial cells in the eye disc did not affect the targeting of retinal axons to the optic stalk. In contrast, αPS3 is not required for retinal glia migration, but together with Talin, it functions in glial cells to allow photoreceptor axons to target the optic stalk. Thus, we present evidence that αPS2 and αPS3 integrin have different and specific functions in the development of retinal glia.

Paraovarian tumor of borderline malignancy - a case report

A case of a 23-year-old woman with a paraovarian tumor is presented. The patient complained of pelvic pain and abdominal swelling. Cystectomy was the initial surgical treatment, but after the histological diagnosis, a staging surgery was carried out. The clinical aspects and subsequent management of related cases are discussed, and a literature review is made.

Carcinoma in situ and early breast carcinoma survey of the Portuguese Senology Society on treatment in Portugal and its evolution between 1985 and 2000

By means of a questionnaire sent to Portuguese hospitals which diagnose and treat most female patients with breast cancer, it was intended to assess the situation regarding the treatment of carcinoma in situ and early breast cancer (T1 or T2, N0 or N1), as well as their evolution between 1985 and 2000. The hospital participation rate was 65% and a sample of 865 patients was collected, distributed by the years 1985, 1990, 1995 and 2000. It was observed that, in terms of surgery, there was an increase in conservative surgery, which was over 40% in 2000, as well as an increase in the average of excised axillary lymph nodes. Progress in the surgical approach was similar both in cancer centres and in large and university hospitals, when compared with the other surveyed hospitals. Also, no differences between these two hospital groups in disease-free survival and overall survival were found. Postoperative radiotherapy was employed in more than 90% of the patients submitted to conservative surgery and adjuvant chemotherapy was used in 39% of all the patients, while tamoxifen as adjuvant treatment was used in 58% of the patients.

Paraovarian tumor of borderline malignancy – a case report

A case of a 23-year-old woman with a paraovarian tumor is presented. The patient complained of pelvic pain and abdominal swelling. Cystectomy was the initial surgical treatment, but after the histological diagnosis, a staging surgery was carried out. The clinical aspects and subsequent management of related cases are discussed, and a literature review is made.

Carcinoma in situ and early breast carcinoma. Survey of the Portuguese Senology Society on the diagnostic tools used in Portugal and their evolution between 1985 and 2000

By means of a questionnaire, sent to the Portuguese hospitals which diagnose and treat most female patients with breast cancer, it was intended to assess the situation regarding the diagnosis of carcinoma in situ and early breast cancer (T1 or T2, N0 or N1), as well as their evolution between 1985 and 2000. The hospital participation rate was 65% and a sample of 865 patients was collected, distributed in the years 1985, 1990, 1995 and 2000. It was found that the presentation form of breast cancer in 1985 was of palpable tumour in 87% of the cases, whereas in 2000 this situation only corresponded to 54% of the patients, being most of the remaining patients diagnosed by imaging without palpable tumour. In 94% of the patients, the first diagnostic investigation was mammography, associated or not to echography, and the second most frequent investigation was fine-needle aspiration biopsy. The time evolution of the tumour size showed an increasingly earlier diagnosis. Invasive tumours not more than 1 cm represented 13.2% in 1985 and 20.3% in 2000. On the other hand, breast cancers more than 2 cm and not more than 5 cm decreased from 67.2% in 1985 to 40% in 2000. When oncology centres and some large university hospitals (Group A) were compared to the other hospitals (Group B), there were no significant differences between the diagnostic methods, although the sequence of diagnostic methods was different in the hospitals in Group A versus those in Group B. It was observed that in more differentiated hospitals the diagnosis was achieved increasingly earlier along the studied periods, and this situation did not occur in the other hospitals.

Locally advanced/inflammatory breast cancers treated with intensive epirubicin-based neoadjuvant chemotherapy: are there molecular markers in the primary tumour that predict for 5-year clinical outcome?

BACKGROUND

Locally advanced and/or inflammatory breast cancer (LABC) is a heterogeneous disease. Molecular markers may help to understand this heterogeneity. This paper reports the results of a study assessing the potential prognostic or predictive value of HER-2, p53, cyclinD1, MIB1, ER and PgR expression by immunohistochemistry from patients included in an EORTC-NCIC-SAKK trial.

PATIENTS AND METHODS

A total of 448 patients with a cytological or histological diagnosis of LABC were randomised into a trial comparing two anthracycline-based neoadjuvant regimens. Chemotherapy was followed by standard locoregional therapy. Survival was comparable in both arms. We collected and analysed centrally paraffin-embedded tumour specimens from 187 (72.5%) of 258 patients that had a histological diagnosis.

RESULTS

Of the patients included in this molecular marker study 114 relapsed and 91 died. In the multivariate analysis p53 positivity was associated with a shorter progression-free survival [hazard ratio (HR) = 1.96; 95% CI 1.33-2.91; P = 0.0008) and a shorter overall survival (HR = 1.98; 95% CI 1.28-3.06; P = 0.002). PgR positivity predicted for a longer overall survival (HR = 0.54; 95% CI 0.35-0.83; P = 0.0045).

CONCLUSIONS

p53 was an independent factor predicting for survival. In order to clarify whether p53 is a pure prognostic and/or a predictive factor, a phase III trial is being conducted (EORTC 10994/BIG 00-01 study) using functional assay in yeast from frozen tumour samples.

Sclerosis of gross cysts of the breast: a three-year study

Breast cysts can be separated into two types: Type I cyst with a lining epithelium which shows apocrine metaplasia, and Type II cyst with an epithelium which is markedly attenuated or absent. The risk of subsequent breast cancer among patients with Type I cysts can be up to 4. The standard treatment is fine needle aspiration, but 20% of the cysts recur. Pharmacological treatment has been tried, which reduces size and volume, but has side-effects and a high recurrence rate post-treatment occurs. The objectives of this prospective study were to sclerose the cyst, induce its regression and prevent or reduce recurrence rate, with the administration of a sclerosing solution (Sclerovein) within the cyst post-aspiration. Fifty-seven patients were followed in the study, 37 with Type I cysts and 20 with Type II cysts. At the end of six months all patients with Type II cysts had no detectable cyst. On the other hand, two patients still had a residual Type I cyst. At the end of three years our recurrence rate appears to be less than 2%, with one patient with a possible recurrence. No significant side-effects were observed. The use of Sclerovein is a simple and safe alternative in the treatment of recurring cysts.

[Prognosis value of p53, C-erB-2 and Ki67 proteins in ovarian carcinoma]

The prognosis in ovarian carcinoma remains poor. We need to identify patients who are less likely to respond to treatment. In order to evaluate the prognostic value of C-erb-B2, p53 and Ki 67 expression and correlate these markers with classic prognostic factors, we studied paraffin-embedded tumor tissue from 81 patients with epithelial ovarian cancer and made a quantitative evaluation of C-erb-B2, p53 and Ki 67 expression by immunohistochemistry. The results were: age 5.4 +/- 15(22-88); 66% with normal physical activity; 48.2% with residual disease < 2 cm; initial stage--42% and advanced stage--58%. Age, performance status, residual disease and stage were correlated with 2 and 5 years survival. Positive immunostaining: p53--87%, C-erb B-2--51% and Ki67--100%. P53 and C-erb B-2 were associated with residual disease and stage; patients with no C-erbB-2 staining had a significantly better survival. A direct and significant correlation was found between p53 and Ki67 and between C-erb B-2 and p53. We conclude that these markers have a high expression in ovarian carcinoma and p53 and C-er B-2 correlate with stage and residual disease. Although C-erb B-2 was associated with better survival, it was not found to be an independent prognostic factor.

[Wertheim-Meigs procedure. 10-year results]

Wertheim-Meigs hysterectomy is used in the treatment of cervical cancer, but since 1988 we have also used it to stage and treat endometrial carcinoma. To evaluate the morbidity of Wertheim Meigs hysterectomy as well as node invasion incidence and its correlation with other prognostic factors, the authors made a retrospective study of 112 patients, from October 1986 to March 1996. Among the 112 cases evaluated, 52% had cervical carcinoma and 48% had endometrial carcinoma; mean ages were 45 +/- 10 and 60 +/- 8 years (p < 0.005). FIGO stage distribution was: I-94.8 and 33.3%; II-5.2 and 51.9%; III-0 and 13%; IV-0 and 1.8%, for cervical and endometrial carcinoma. Hemorrhagic and traumatic accidents happened in 24.3% and 1.7% respectively. We had 15.5% early post operative complications and 1.7% late post operative ones. The mean duration of surgery and hospitalization was 163 +/- 29 minutes and 10 +/- 5 days. Pelvic lymphadenectomy was performed in 70% of patients and para-aortic nodes were also excised in the other 30%. The mean number of lymphatic nodes excised were 17 +/- 9. Pelvic node invasion was found in 9% and in 3.7% of para-aortic ones. When we studied endometrial cancer, we found a positive correlation between external myometrium invasion and lymphovascular invasion and positive node (p < 0.05). From the data available we may conclude that the complication rate of Wertheim Meigs is quite important, even though all but one complication were transitory. It may be possible to make a better selection of patients who need this surgical procedure by correct evaluation of risk factors.

Effect of selection for lean tissue growth on body composition and physiological state of the pig at birth

The effects of selection for lean tissue growth on the metabolic and physiological state (i.e., level of maturity) of the pig at birth have been examined on newborns from three breeds that markedly differ with respect to birth weight and postnatal muscle growth potential: a primitive Chinese breed (Meishan, MS), a European breed (Large White, LW), and a composite line (CL) highly selected for high rate of gain. Within each breed, 40 pigs from eight litters were used for whole carcass and tissue sampling, blood sampling, and for a fat tolerance test at 2 h of age. The CL pigs were heavier (P < .001) than the LW and MS pigs at birth but exhibited lower percentages of carcass protein, fat, mobilizable fat, and ash than the MS pigs (P < .05). In addition, MS pigs had larger adipose tissue adipocytes than pigs from the two other breeds (P < .001). Despite their 31% higher RNA capacity in longissimus muscle (higher RNA:protein ratio, P < .05), CL pigs exhibited a lower percentage of muscle protein (P < .05) than did MS pigs. Relative liver weight was higher for LW than for CL pigs (P < .05), which had the lowest percentage of liver phospholipids (P < .01). The CL pigs exhibited lower hematocrit (P < .01), glucose (P < .01), albumin (P < .01), cortisol (P < .01), and thyroxine (P < .05) levels than the MS pigs.(ABSTRACT TRUNCATED AT 250 WORDS)