Evaluating and reporting LET and RBE-weighted dose in proton therapy for glioma - The Dutch approach.

Background And Purpose: With proton therapy, the relative biological effectiveness (RBE) accounts for increased DNA damage caused by higher linear energy transfer (LET) compared to photons. However, the LET and hence the RBE varies along the proton range, particularly at the Bragg peak, introducing challenges in proton treatment planning for brain tumors. The aim of this paper is to standardize evaluating and reporting LET and RBE in proton therapy for patients with grade 2 and 3 IDH mutant gliomas among the Dutch proton therapy centers.

Development of an Ex Vivo Functional Assay for Prediction of Irradiation Related Toxicity in Healthy Oral Mucosa Tissue.

Radiotherapy in the head-and-neck area is one of the main curative treatment options. However, this comes at the cost of varying levels of normal tissue toxicity, affecting up to 80% of patients. Mucositis can cause pain, weight loss and treatment delays, leading to worse outcomes and a decreased quality of life.

Functional Homologous Recombination (HR) Screening Shows the Majority of -Mutant Breast and Ovarian Cancer Cell Lines Are HR-Proficient.

Tumors with a pathogenic mutation are homologous recombination (HR)-deficient (HRD) and consequently sensitive to platinum-based chemotherapy and Poly-[ADP-Ribose]-Polymerase inhibitors (PARPi). We hypothesized that functional HR status better reflects real-time HR status than mutation status. Therefore, we determined the functional HR status of 53 breast cancer (BC) and 38 ovarian cancer (OC) cell lines by measuring the formation of RAD51 foci after irradiation.

Proof-of-concept study linking ex vivo sensitivity testing to neoadjuvant anthracycline-based chemotherapy response in breast cancer patients.

We developed a functional ex vivo anthracycline-based sensitivity test. Surgical resection material of primary breast cancer (BC) was used to determine criteria for the ex vivo sensitivity assay based on morphology, proliferation and apoptosis. Subsequently, a proof-of-concept study was performed correlating results of this assay on primary BC biopsies with in vivo response after treatment with anthracycline-containing neoadjuvant chemotherapy (NAC).

Establishing a Microfluidic Tumor Slice Culture Platform to Study Drug Response.

Accurate models for tumor biology and prediction of drug responses of individual tumors require novel technology to grow tumor tissue ex vivo to maintain tumor growth characteristics in situ. Models containing only tumor cells, without the stromal components of the tumor, are suboptimal for many purposes and are generally problematic because the cells are passed through extensive culture and selection. Therefore, direct culture of (human) tumors is of considerable interest for basic tumor biology and diagnostic purposes.

Ex Vivo Functional Assay for Evaluating Treatment Response in Tumor Tissue of Head and Neck Squamous Cell Carcinoma.

Background: Head and neck squamous cell carcinoma (HNSCC) displays a large heterogeneity in treatment response, and consequently in patient prognosis. Despite extensive efforts, no clinically validated model is available to predict tumor response. Here we describe a functional test for predicting tumor response to radiation and chemotherapy on the level of the individual patient.

Preclinical Assessment of the Combination of PSMA-Targeting Radionuclide Therapy with PARP Inhibitors for Prostate Cancer Treatment.

Prostate specific membrane antigen targeted radionuclide therapy (PSMA-TRT) is a promising novel treatment for prostate cancer (PCa) patients. However, PSMA-TRT cannot be used for curative intent yet, thus additional research on how to improve the therapeutic efficacy is warranted. A potential way of achieving this, is combining TRT with poly ADP-ribosylation inhibitors (PARPi), which has shown promising results for TRT of neuroendocrine tumor cells.

Functional RECAP (REpair CAPacity) assay identifies homologous recombination deficiency undetected by DNA-based BRCAness tests.

Germline BRCA1/2 mutation status is predictive for response to Poly-[ADP-Ribose]-Polymerase (PARP) inhibitors in breast cancer (BC) patients. However, non-germline BRCA1/2 mutated and homologous recombination repair deficient (HRD) tumors are likely also PARP-inhibitor sensitive. Clinical validity and utility of various HRD biomarkers are under investigation.

The COMPLETE trial: HolistiC early respOnse assessMent for oroPharyngeaL cancEr paTiEnts; Protocol for an observational study.

Introduction: The locoregional failure (LRF) rate in human papilloma virus (HPV)-negative oropharyngeal squamous cell carcinoma (OPSCC) remains disappointingly high and toxicity is substantial. Response prediction prior to or early during treatment would provide opportunities for personalised treatment. Currently, there are no accurate predictive models available for correct OPSCC patient selection.

Functional Ex Vivo Tissue-Based Chemotherapy Sensitivity Testing for Breast Cancer.

Unlabelled: Background chemotherapy is part of most breast cancer (BC) treatment schedules. However, a substantial fraction of BC tumors does not respond to the treatment. Unfortunately, no standard biomarkers exist for response prediction.

Rapid recruitment of p53 to DNA damage sites directs DNA repair choice and integrity.

SignificanceOur work focuses on the critical longstanding question of the nontranscriptional role of p53 in tumor suppression. We demonstrate here that poly(ADP-ribose) polymerase (PARP)-dependent modification of p53 enables rapid recruitment of p53 to damage sites, where it in turn directs early repair pathway selection. Specifically, p53-mediated recruitment of 53BP1 at early time points promotes nonhomologous end joining over the more error-prone microhomology end-joining.

A Microfluidic Cancer-on-Chip Platform Predicts Drug Response Using Organotypic Tumor Slice Culture.

Optimal treatment of cancer requires diagnostic methods to facilitate therapy choice and prevent ineffective treatments. Direct assessment of therapy response in viable tumor specimens could fill this diagnostic gap. Therefore, we designed a microfluidic platform for assessment of patient treatment response using tumor tissue slices under precisely controlled growth conditions.

A BRCA1 Coiled-Coil Domain Variant Disrupting PALB2 Interaction Promotes the Development of Mammary Tumors and Confers a Targetable Defect in Homologous Recombination Repair.

The tumor suppressor gene encodes a multidomain protein for which several functions have been described. These include a key role in homologous recombination repair (HRR) of DNA double-strand breaks, which is shared with two other high-risk hereditary breast cancer suppressors, BRCA2 and PALB2. Although both BRCA1 and BRCA2 interact with PALB2, missense variants affecting its PALB2-interacting coiled-coil domain are considered variants of uncertain clinical significance (VUS).

Biallelic variants in LIG3 cause a novel mitochondrial neurogastrointestinal encephalomyopathy.

Abnormal gut motility is a feature of several mitochondrial encephalomyopathies, and mutations in genes such as TYMP and POLG, have been linked to these rare diseases. The human genome encodes three DNA ligases, of which only one, ligase III (LIG3), has a mitochondrial splice variant and is crucial for mitochondrial health. We investigated the effect of reduced LIG3 activity and resulting mitochondrial dysfunction in seven patients from three independent families, who showed the common occurrence of gut dysmotility and neurological manifestations reminiscent of mitochondrial neurogastrointestinal encephalomyopathy.

Homologous Recombination Deficiency Testing for BRCA-Like Tumors: The Road to Clinical Validation.

Germline mutations result in homologous recombination deficiency (HRD) in hereditary breast and ovarian cancer, as well as several types of sporadic tumors. The HRD phenotype makes these tumors sensitive to DNA double strand break-inducing agents, including poly-(ADP-ribose)-polymerase (PARP) inhibitors. Interestingly, a subgroup of cancers without a mutation also shows an HRD phenotype.

Extensive preclinical evaluation of lutetium-177-labeled PSMA-specific tracers for prostate cancer radionuclide therapy.

Purpose: Various radiolabeled prostate-specific membrane antigen (PSMA)-targeting tracers are clinically applied for prostate cancer (PCa) imaging and targeted radionuclide therapy. The PSMA binding affinities, biodistribution, and DNA-damaging capacities of these radiotracers have not yet been compared in detail. A major concern of PSMA-targeting radiotracers is the toxicity in other PSMA-expressing organs, such as the salivary glands, thus demanding careful evaluation of the most optimal and safest radiotracer.

The RECAP Test Rapidly and Reliably Identifies Homologous Recombination-Deficient Ovarian Carcinomas.

Recent studies have shown that the efficacy of PARP inhibitors in epithelial ovarian carcinoma (EOC) is related to tumor-specific defects in homologous recombination (HR) and extends beyond deficient EOC. A robust method with which to identify HR-deficient (HRD) carcinomas is therefore of utmost clinical importance. In this study, we investigated the proficiency of a functional HR assay based on the detection of RAD51 foci, the REcombination CAPacity (RECAP) test, in identifying HRD tumors in a cohort of prospectively collected epithelial ovarian carcinomas (EOCs).

C-Terminal Extensions of Ku70 and Ku80 Differentially Influence DNA End Binding Properties.

The Ku70/80 heterodimer binds to DNA ends and attracts other proteins involved in the non-homologous end-joining (NHEJ) pathway of DNA double-strand break repair. We developed a novel assay to measure DNA binding and release kinetics using differences in Förster resonance energy transfer (FRET) of the ECFP-Ku70/EYFP-Ku80 heterodimer in soluble and DNA end bound states. We confirmed that the relative binding efficiencies of various DNA substrates (blunt, 3 nucleotide 5' extension, and DNA hairpin) measured in the FRET assay reflected affinities obtained from direct measurements using surface plasmon resonance.

Comparison of High- and Low-LET Radiation-Induced DNA Double-Strand Break Processing in Living Cells.

High-linear-energy-transfer (LET) radiation is more lethal than similar doses of low-LET radiation types, probably a result of the condensed energy deposition pattern of high-LET radiation. Here, we compare high-LET α-particle to low-LET X-ray irradiation and monitor double-strand break (DSB) processing. Live-cell microscopy was used to monitor DNA double-strand breaks (DSBs), marked by p53-binding protein 1 (53BP1).

Guide-free Cas9 from pathogenic bacteria causes severe damage to DNA.

CRISPR-Cas9 systems are enriched in human pathogenic bacteria and have been linked to cytotoxicity by an unknown mechanism. Here, we show that upon infection of human cells, secretes its Cas9 (CjeCas9) nuclease into their cytoplasm. Next, a native nuclear localization signal enables CjeCas9 nuclear entry, where it catalyzes metal-dependent nonspecific DNA cleavage leading to cell death.

HSF2BP negatively regulates homologous recombination in DNA interstrand crosslink repair.

The tumor suppressor BRCA2 is essential for homologous recombination (HR), replication fork stability and DNA interstrand crosslink (ICL) repair in vertebrates. We show that ectopic production of HSF2BP, a BRCA2-interacting protein required for meiotic HR during mouse spermatogenesis, in non-germline human cells acutely sensitize them to ICL-inducing agents (mitomycin C and cisplatin) and PARP inhibitors, resulting in a phenotype characteristic of cells from Fanconi anemia (FA) patients. We biochemically recapitulate the suppression of ICL repair and establish that excess HSF2BP compromises HR by triggering the removal of BRCA2 from the ICL site and thereby preventing the loading of RAD51.

Low dose ionizing radiation strongly stimulates insertional mutagenesis in a γH2AX dependent manner.

Extrachromosomal DNA can integrate into the genome with no sequence specificity producing an insertional mutation. This process, which is referred to as random integration (RI), requires a double stranded break (DSB) in the genome. Inducing DSBs by various means, including ionizing radiation, increases the frequency of integration.

Uptake and subcellular distribution of radiolabeled polymersomes for radiotherapy.

Polymersomes have the potential to be applied in targeted alpha radionuclide therapy, while in addition preventing release of recoiling daughter isotopes. In this study, we investigated the cellular uptake, post uptake processing and intracellular localization of polymersomes. High-content microscopy was used to validate polymersome uptake kinetics.

Direct Ex Vivo Observation of Homologous Recombination Defect Reversal After DNA-Damaging Chemotherapy in Patients With Metastatic Breast Cancer.

Purpose: Biomarkers that predict response to poly (ADP-ribose) polymerase inhibitors (PARPis) are required to detect PARPi sensitivity beyond germline -mutated (gBRCAm) cancers and PARPi resistance among reverted gBRCAm cancers. Therefore, we previously developed the Repair Capacity (RECAP) test, a functional homologous recombination (HR) assay that exploits the formation of RAD51 foci in proliferating cells after ex vivo irradiation of fresh primary breast cancer tissue. The aim of the current study was to validate the feasibility of this test on histologic biopsy specimens from metastatic breast cancer and to explore the utility of the RECAP test as a predictive tool for treatment with DNA-damaging agents, such as PARPis.

Apalutamide Sensitizes Prostate Cancer to Ionizing Radiation via Inhibition of Non-Homologous End-Joining DNA Repair.

Androgen-deprivation therapy was shown to improve treatment outcome of external beam radiation therapy (EBRT) for locally advanced prostate cancer (PCa). DNA damage response (DDR) was suggested to play a role in the underlying mechanism, but conflicting results were reported. This study aims to reveal the role of the androgen receptor (AR) in EBRT-induced DDR and to investigate whether next-generation AR inhibitor apalutamide can radiosensitize PCa.