Abstract 6108: Novel functional dSTRIDE-HR assays to report on the status of homologous recombination repair in cancer cells

Since the early days of the synthetic lethality concept in DNA Damage Response the status of homologous recombination (HR) repair in cancer cells have been the focus of attention of researchers and clinicians. While different approaches exist, such as the RAD51 immunofluorescence (IF) or HRD genomic assays, functional biomarkers that can assess HR proficiency are missing. We report here the development, optimization and validation of two complementary, HR-specific functional assays. The assays, which are based on the STRIDE platform technology, detect double-strand DNA breaks localized in close proximity to RPA or RAD51 proteins. The optimization phase of assay development was performed in U2OS cells. First, repeatability (intra-run variation) and reproducibility (inter-run variation) of the assays were measured in untreated cells. Then, a series of technical negative controls was performed which have shown that the number of false-positive readouts is below 10% of the total number of signals. Finally, treatment of cells with compounds known to induce double-strand DNA breaks (etoposide and cisplatin) resulted in statistically significant increase in the number of detected dSTRIDE-RAD51 and dSTRIDE-RPA foci when compared to untreated controls. The assays were further validated in NCI-H661 (BRCA2 wild-type) and NCI-H169 (BRCA2 KO) cell line pair. The cells were treated with two concentrations of etoposide and the readouts from dSTRIDE, detecting the total pool of DSBs and dSTRIDE-HR assays were compared. In NCI-H661 cells, treatment with etoposide resulted in an increase in the number of double-strand breaks detected by dSTRIDE and as expected, more DSBs were formed after treatment with the higher concentration. dSTRIDE-HR assays confirmed that approximately 15% and 10% of these DSBs contain RPA and RAD51 proteins, respectively. In NCI-H169 cells etoposide produced a stronger reaction with even more DSBs detected by dSTRIDE, but importantly, no increase in the number of dSTRIDE-RAD51 foci was observed. dSTRIDE-RPA foci increased after treatment hinting that this step of HR remains unperturbed. Interestingly, the number of dSTRIDE-RAD51 foci in untreated cells was comparable between the two cell lines. In conclusion, we show here that two newly developed dSTRIDE-HR assays are well validated and can be successfully applied to report on the status of homologous recombination repair in different cell models.

Citation Format: Kamil Solarczyk, Agnieszka Waligórska, Karolina Uznańska, Zsombor Prucsi, Olga Wójcikowska, Ewelina Matuszyk, Magdalena Bartyńska, Agata Kitlińska, Aleksandra Bober, Franek Sierpowski, Maja Białecka, Monika Jarosz, Malgorzata Szczygiel, Szymon Koman, Karolina Korpanty, Lukasz Beben, Lukasz Bandzarewicz, Przemyslaw Stachura, Magdalena Kordon-Kiszala. Novel functional dSTRIDE-HR assays to report on the status of homologous recombination repair in cancer cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6108.

Abstract 6211: Development and validation of a novel sSTRIDE-MMR functional assay to study the efficiency of MMR inhibitors

Mismatch repair (MMR) is considered to be one of the fundamental pathways that guards genome stability and mutations in genes encoding for crucial MMR proteins have been shown to promote cancer initiation. On the other hand, inactivation of MMR components in cancer cells leads to increased neoantigen formation and in consequence, exposes the tumor to the immune system. Therapeutic strategies aiming at inhibiting MMR are thus under development, yet methods reporting on the status of MMR are lacking. We report here the development, optimization and validation of a first MMR-specific functional assay. The assay, which is based on the STRIDE platform technology, detects DNA nicks localized in close proximity to PMS2 protein and can thus be utilized as a direct reporter of inhibition of PSM2 itself or upstream acting proteins. The optimization phase of assay development was performed in U2OS cells. First, in untreated cells we have shown that the sSTRIDE-MMR signals constitute ca. 10-15% of total single-strand DNA breaks foci detected by the classic sSTRIDE assay variant. In a series of technical negative controls we have then shown that the number of false-positive foci never exceeds 10% of the total number of signals, with as little as 2% for the isotype controls. The assay was further validated in HAP1 wild-type and PMS2-KO isogenic cell line pair. As expected, the number of sSTRIDE-MMR foci in the PMS2-KO cell line was significantly lower than in wild-type cells and additionally, no response to the treatment with 6TG, a known inducer of MMR, was detected in PMS2 null cells. Finally, the assay was used to verify the efficiency of first-in-class small-molecule MMR inhibitors. After treatment with the compounds, the number of detected sSTRIDE-MMR foci was significantly lower when compared to the number of foci in untreated cells. In conclusion, we show here that sSTRIDE-MMR is an assay characterized by high specificity, low false positives rate and a high-dynamic range. We believe that sSTRIDE-MMR can prove to be a very useful cell-based solution to study the efficiency of MMR inhibitors.

Citation Format: Kamil Solarczyk, Karolina Uznańska, Olga Wójcikowska, Maja Białecka, Agnieszka Waligórska, Szymon Koman, Magdalena Kordon-Kiszala. Development and validation of a novel sSTRIDE-MMR functional assay to study the efficiency of MMR inhibitors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6211.

Catechol-oxide-methyltransferase (COMT rs4680:G>A) gene polymorphism does not affect analgesics’ demand after elective hip replaceme

Pain in patients with hip osteoarthritis appears long before surgery, and requires effective management as it affects patient comfort and daily activities. Therefore, the search for factors influencing response rate to analgesics is mandatory. In recent years, increasing attention has been paid to genetic factors underlying pain threshold and treatment efficacy. Polymorphic gene of catechol-oxide-methyltransferase (COMT) is a candidate gene associated with pain pathology and treatment response. The aim of the study was to evaluate association between the COMT rs4680:G>A polymorphism and demand for analgesics in patients subjected to elective hip replacement. The study included 196 patients after hip replacement surgery. Opioid demand was recorded and analgesic efficacy was scored using a four-level verbal pain intensity scale. COMT rs4680:G>A polymorphism was analysed by PCR-RFLP method. The studied COMT genotypes did not influence opioid administration in the studied patients from the day of surgery till day 6 afterwards. The distribution of the COMT rs4680:G>A in the studied subjects was as follows: GA—52.04%, AA—23.98% and GG—23.98%. It can be concluded that the COMT rs4680:G>A polymorphism is not associated with opioid demand in patients after elective hip replacement.

Can We Talk about CD4+CD28– Lymphocytes as a Risk Factor for Ischemic Stroke?

BACKGROUND

CD4+CD28- lymphocytes are implicated in the destabilization of atheromatous plaque, leading to acute coronary episodes. One may ask whether these cells play a similar role in ischemic stroke pathogenesis with an atherosclerotic background.

METHODS

Flow cytometry was applied to determine the percentage of CD4+CD28- lymphocytes in the peripheral blood of patients during the acute phase of their first ischemic stroke (group I) and in patients without a history of stroke but with two of the most important risk factors (hypertension, diabetes) for atherosclerosis-related ischemic stroke (group II). The results were compared with healthy controls.

RESULTS

The median percentages of CD4+CD28- lymphocytes in groups I and II did not differ significantly, but for each of these groups the percentage was higher than in the control group. The time of blood sampling from onset of stroke, presence of the ischemic focus in the CT brain scan and severity of neurological deficits did not correlate with the percentage of CD4+CD28- lymphocytes.

CONCLUSIONS

We conclude that CD4+CD28- lymphocytes are implicated in mechanisms enhancing the risk of acute ischemic stroke and not a consequence of stroke.

The effect of monoamine oxidase B (MAOB) and catechol-O-methyltransferase (COMT) polymorphisms on levodopa therapy in patients with sporadic Parkinson's disease

OBJECTIVES

The etiology of sporadic idiopathic Parkinson's disease (PD) is considered multifactorial with both genetic and environmental factors modifying the disease expression. Recent studies suggest that polymorphism in monoamine oxidase B (MAOB) and catechol-O-methyltransferase (COMT) might influence the risk and treatment of PD. The aim of the study was to evaluate the effect of MAOB and COMT genetic polymorphism on effective daily dose of levodopa applied during the first 5 years of treatment, and to find out if a relationship exists between MAOB and COMT haplotypes and motor disturbances onset in PD patients treated with levodopa preparations.

MATERIALS AND METHODS

A total of 95 patients (40 females and 55 males) of Polish origin diagnosed with sporadic PD were enrolled into the study, and were divided into two groups. Group 1 - patients treated with doses of levodopa below 500 mg/day during the first 5 years of treatment. Group 2 - patients requiring levodopa doses exceeding 500 mg/24 h during the first 5 years of treatment. Low activity alleles of MAOB and COMT, i.e. MAOB allele A and COMT(L) as well as high activity ones, i.e. MAOB allele G and COMT(H), were determined using PCR-RFLP method.

RESULTS

No statistically significant differences were found in MAOB and COMT allele distribution in the two groups. However, the frequency of COMT(L/L) homozygotes was higher in the group treated with low doses of levodopa when compared with the second group. MAOB and COMT AG-HH haplotype predominated in the group of females treated with high daily doses of levodopa when compared with AG-LL haplotype in the group of females treated with low daily doses of levodopa (<500 mg/24 h).

CONCLUSION

The results of the study suggest that patients with COMT(L/L) genotype and possibly MAOB genotype A may benefit from more efficient and safer levodopa therapy.

[Effect of therapeutic drug monitoring of amitriptyline and genotyping on efficacy and safety of depression therapy]

Modern pharmacotherapy is based on precise adjustment of a dosage schedule to individual requirements of patient. Therapeutic drug monitoring is a method that allows for a more effective treatment approach, especially in the case of a narrow therapeutic index of a drug. Tricyclic antidepressant drugs are characterised by narrow therapeutic index as well as relationship between serum drug concentration and side effects. It was demonstrated that interindividual variability of blood concentrations of tricyclic antidepressant drugs is related to genetic polymorphism of oxidating enzymes participating in metabolism of these drugs. The aim of the study was to estimate the impact of therapeutic drug monitoring of tricyclic antidepressant drugs as well as genotyping on efficacy and safety of endogenous depression therapy. The study included 9 patients with established diagnosis of endogenous depression. Blood serum concentrations of amitryptyline was measured by fluorescence polarisation immune assay (FPIA, Abbott system). Genotype of cytochrome P450 isoenzyme CYP2D6 was determined using PCR-RFLP method. It was demonstrated that monitoring therapy of tricyclic antidepressant drugs in combination with determination of the genotype seems to be more safe and effective. Monitoring therapy and genotyping may be less expensive than the costs of prolonged hospitalisation and risk of side effects.

[Current concepts on the subject of properties and use of antidepressants]

Clinical evaluation of new, second generation antidepressants has been presented. The purpose of this paper also was to compare these drugs with the well defined, up to new administered antidepressive compounds, as for as their pharmacodynamic and pharmacokinetic properties are concerned and to indicate criteria for the "ideal" antidepressant.

[The effect of bioflavonoids and lecithin on the course of experimental atherosclerosis in rabbits]

Atherosclerosis and its clinical manifestations are still one of the most important civilization problems. New questions arise: is it really an inevitable process? Are there any rational methods to prevent the development of atherosclerotic changes or to facilitate its regression? The aim of the work was to evaluate the influence of bioflavonoids extracted from milk thistle (Sylibum marianum L), troxerutin (O-(beta-hydroxy-ethyl)-ruozid and lecithin, administered together and as a single therapy, on the experimental atherosclerosis development in rabbits. Sixty male mixed-breed rabbits were randomly assigned to 6 equal groups: I--control, II--fed on fat-rich diet (FR/DB), III--fed on FR-diet and sylimaryn concentrate (S), IV--animals fed on FR-diet and troxerutin (T), V--rabbits fed on FR-diet and soya bean lecithin (L), VI--animals fed on FR-diet and sylimaryn-phospholipid complex (SF). The whole experiment lasted 12 weeks. Following tests have been performed: electrocardiographic, biochemical, pathomorphological (including macroscopic and microscopic evaluations of aorta). Biochemical analysis included: cholesterol concentration (total, low density lipoprotein fraction cholesterol and high density fraction cholesterol), triglycerides, b-lipoproteins, phospholipids, fibrinogen, trace elements (calcium, magnesium, zinc and copper) and dimalonic aldehyde concentration. Concentrations of ascorbyl free radical, total cholesterol, triglycerides, P-450 cytochrome and phospholipids in liver have been estimated. Evident normalization of lipid metabolism and inhibition of atherosclerotic changes have been observed in the group of animals fed on SF complex. Concentrations of total cholesterol, LDL-cholesterol fraction, phospholipids and triglycerides decreased in serum. Decrease of serum dimalonic aldehyde was followed by increase of ascorbyl free radicals concentration in liver. Significant increase of serum zinc has been also noted, which exceeded values observed in control group. Concentration of P-450 cytochrome increased in liver microsomes. Sylimaryn and lecithin showed less anti-atherosclerotic activity, and troxerutin displayed the least anti-atherosclerotic activity (Tab. 1-2, Fig. 1-2). On the basis of the achieved results the following conclusions were drawn: 1) Sylimaryn and lecithin have anti-atherosclerotic activity in rabbits. 2) Sylimaryn-phospholipid complex shows the strongest anti-atherosclerotic activity. 3) The achieved results allow us to undertake clinical trials using SF-complex in prevention and treatment of atherosclerosis.

Eleven Polish patients with microcephaly, immunodeficiency, and chromosomal instability: the Nijmegen breakage syndrome

We report on 11 patients from 8 independent families (3 pairs of sibs) with a complex clinical pattern including microcephaly, peculiar "bird-like" face, growth retardation, and, in some cases, mild-to-moderate mental deficiency. Most of the patients have recurring respiratory tract infections. One girl has developed B-cell lymphoma. A detailed anthropometric study of 15 physical parameters, including 3 cephalic traits, was performed. It was possible to study the chromosomes of PHA-stimulated lymphocytes in all of the patients. We found structural aberrations with multiple rearrangements, preferentially involving chromosomes 7 and 14 in a proportion of metaphases in all individuals. Profound humoral and cellular immune defects were observed. Serum AFP levels were within normal range. Radioresistant DNA synthesis was strongly increased in all 8 patients who were hitherto studied in this respect. Our patients fulfill the criteria of the Nijmegen breakage syndrome, which belongs to the growing category of ataxia telangiectasia-related genetic disorders. In light of the increased predisposition to malignancy in this syndrome, an accurate diagnosis is important for the patient.

A further report of Brachmann-de Lange syndrome in two sibs with normal parents

We report on a family in which a girl and a boy in the same sibship show variable manifestations of a less severe type of Brachmann-de Lange syndrome without significant prenatal growth deficiency and reduction deformities of the forearms. Both parents are healthy and phenotypically normal, and no other family members are affected. All the affected sibs except one described so far with normal parents presented the severe type of Brachmann-de Lange syndrome (now sometimes classified as type I: "classic" or "full" Brachmann-de Lange syndrome), with major upper limb anomalies, severe growth and mental retardation and, frequently, early death. We discuss the possible role of genomic imprinting in the etiology of this syndrome.