Zebrafish Xenografts Unveil Sensitivity to Olaparib beyond BRCA Status

Triumphs and challenges in exploiting poly(ADP-ribose) polymerase inhibition to combat triple-negative breast cancer

Poly(ADP-ribose) polymerase 1 (PARP1) regulates a myriad of DNA repair mechanisms to preserve genomic integrity following DNA damage. PARP inhibitors (PARPi) confer synthetic lethality in malignancies with a deficiency in the homologous recombination (HR) pathway. Patients with triple-negative breast cancer (TNBC) fail to respond to most targeted therapies because their tumors lack expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Certain patients with TNBC harbor mutations in HR mediators such as breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2), enabling them to respond to PARPi. PARPi exploits the synthetic lethality of BRCA-mutant cells. However, de novo and acquired PARPi resistance frequently ensue. In this review, we discuss the roles of PARP in mediating DNA repair processes in breast epithelial cells, mechanisms of PARPi resistance in TNBC, and recent advances in the development of agents designed to overcome PARPi resistance in TNBC.

Development of a Triple-Negative Breast Cancer Leptomeningeal Disease Model in Zebrafish

Leptomeningeal disease occurs when cancer cells migrate into the ventricles of the brain and spinal cord and then colonize the meninges of the central nervous system. The triple-negative subtype of breast cancer often progresses toward leptomeningeal disease and has a poor prognosis because of limited treatment options. This is due, in part, to a lack of animal models with which to study leptomeningeal disease. Here, we developed a translucent zebrafish casper (roy-/-; nacre-/-) xenograft model of leptomeningeal disease in which fluorescent labeled MDA-MB-231 human triple-negative breast cancer cells are microinjected into the ventricles of zebrafish embryos and then tracked and measured using fluorescent microscopy and multimodal plate reader technology. We then used these techniques to measure tumor area, cell proliferation, and cell death in samples treated with the breast cancer drug doxorubicin and a vehicle control. We monitored MDA-MB-231 cell localization and tumor area, and showed that samples treated with doxorubicin exhibited decreased tumor area and proliferation and increased apoptosis compared to control samples.

Oleanolic acid combined with olaparib enhances radiosensitization in triple negative breast cancer and hypoxia imaging with 18F-FETNIM micro PET/CT

The heterogeneity of triple negative breast cancer (TNBC) results in the worst prognosis among breast cancer types, making its treatment strategy very challenging. A recent study showed that oleanolic acid (OA) has a radiosensitizing effect on tumor cells, but it does not show a good clinical effect when used alone in radiotherapy. The cytotoxicity of radiotherapy can be enhanced by modulating DNA repair, so new treatment options are being investigated to inhibit DNA repair pathways and sensitize tumors to radiation. Radiation induces DNA double-strand breaks (DSBs), and inhibition of Poly (ADP-Ribose) polymerase (PARP) can prevent the repair of these lesions. Hence, we evaluated the radiosensitization and the underlying mechanism of combination treatment with OA and olaparib in TNBC. Meanwhile, tumor hypoxia was monitored with ¹⁸F-Fluoroerythronitroimidazole (FETNIM) positron emission tomography/computed tomography (PET/CT) during radiosensitization therapy. Here, we found that OA and olaparib in combination with radiotherapy significantly inhibited cell proliferation compared with other groups. The results were observed using colony formation assays [sensitization enhancement ratios (SER) 1.16-1.65]. In vivo, tumor growth was significantly delayed in transplanted tumors receiving irradiation (IR) with OA and olaparib. ¹⁸F-FETNIM PET/CT can be utilized for tumor hypoxia monitoring and radiosensitization response evaluation. In conclusion, these results suggest that the combination of OA and olaparib with IR enhances the inhibition of MDA-MB-231 in cell culture and in mice, providing a potentially novel combination for the effective treatment of TNBC patients.

Zebrafish Patient-Derived Avatars from Digestive Cancers for Anti-cancer Therapy Screening

Patient-derived xenografts (PDXs), also called "avatars," are generated by the implantation of human primary tumor cells or tissues into a host animal. Given the complexity and unique characteristics of each tumor, PDXs are models of choice in cancer research and precision medicine. In this context, the zebrafish PDX model (zPDX or zAvatar) has been recognized as a promising in vivo model to directly challenge patient cells with anti-cancer therapies in a personalized manner. The assay relies on the injection of tumor cells from patients into zebrafish embryos to then test and identify the best available drug combination for a particular patient. Compared to mouse PDXs, zAvatar assays take less time and do not require in vitro or in vivo cell expansion. The present article describes how to generate zAvatars from resected digestive cancer from surgeries and how to then use them for anti-cancer therapy screening. We describe the steps for tumor sample collection and cryopreservation, sample preparation and fluorescent labeling for microinjection into zebrafish embryos, drug administration, and analysis of tumor behavior by single-cell confocal imaging. We provide detailed protocols and helpful tips for performing this assay, and we address the technical challenges associated with the workflow. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Patient tumor sample collection and cryopreservation Basic Protocol 2: Generation of zAvatars and anti-cancer treatment Basic Protocol 3: Whole-mount immunofluorescence Basic Protocol 4: Confocal imaging and analysis.

Auger Emitter Conjugated PARP Inhibitor for Therapy in Triple Negative Breast Cancers: A Comparative In-Vitro Study

Simple Summary

Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer, with a high recurrence rate. Since treatment of BRCA^mut TNBC patients with PARP inhibitor (PARPi), targeting the nuclear protein PARP1, shows varied responses, its therapeutic efficacy is currently evaluated in combination with chemotherapy. Auger emitters (AEs) are radionuclides that can cause DNA damage when delivered close to the DNA. Due to the nuclear location of PARP1, radiolabelling of PARPi with AEs provide an efficient nuclear delivery mechanism. This study shows the radiosynthesis of an AE radiolabelled PARPi ([¹²⁵I]-PARPi-01) and its therapeutic effect as monotherapy or in combination with chemotherapeutics in a panel of TNBC cell lines. We found that [¹²⁵I]-PARPi-01 efficiently induces DNA damage with therapeutic effect irrespective of BRCA mutation. All responsive cell lines have homologous recombination deficiency. Short pretreatment with doxorubicin significantly reduces clonogenic survival of both responsive and resistant cell lines.

Abstract

PARP1 inhibitors (PARPi) are currently approved for BRCA^mut metastatic breast cancer, but they have shown limited response in triple negative breast cancer (TNBC) patients. Combination of an Auger emitter with PARPis enables PARP inhibition and DNA strand break induction simultaneously. This will enhance cytotoxicity and additionally allow a theranostic approach. This study presents the radiosynthesis of the Auger emitter [¹²⁵I] coupled olaparib derivative: [¹²⁵I]-PARPi-01, and its therapeutic evaluation in a panel of TNBC cell lines. Specificity was tested by a blocking assay. DNA strand break induction was analysed by γH2AX immunofluorescence staining. Cell cycle analysis and apoptosis assays were studied using flow cytometry in TNBC cell lines (BRCA^wt/mut). Anchorage independent growth potential was evaluated using soft agar assay. [¹²⁵I]-PARPi-01 showed PARP1-specificity and higher cytotoxicity than olaparib in TNBC cell lines irrespective of BRCA their status. Cell lines harbouring DNA repair deficiency showed response to [¹²⁵I]-PARPi-01 monotherapy. Combined treatment with Dox-NP further enhanced therapeutic efficiency in metastatic resistant BRCA^wt cell lines. The clonogenic survival was significantly reduced after treatment with [¹²⁵I]-PARPi-01 in all TNBC lines investigated. Therapeutic efficacy was further enhanced after combined treatment with chemotherapeutics. [¹²⁵I]-PARPi-01 is a promising radiotherapeutic agent for low radiation dosages, and mono/combined therapies of TNBC.

Object detection for automatic cancer cell counting in zebrafish xenografts

Cell counting is a frequent task in medical research studies. However, it is often performed manually; thus, it is time-consuming and prone to human error. Even so, cell counting automation can be challenging to achieve, especially when dealing with crowded scenes and overlapping cells, assuming different shapes and sizes. In this paper, we introduce a deep learning-based cell detection and quantification methodology to automate the cell counting process in the zebrafish xenograft cancer model, an innovative technique for studying tumor biology and for personalizing medicine. First, we implemented a fine-tuned architecture based on the Faster R-CNN using the Inception ResNet V2 feature extractor. Second, we performed several adjustments to optimize the process, paying attention to constraints such as the presence of overlapped cells, the high number of objects to detect, the heterogeneity of the cells' size and shape, and the small size of the data set. This method resulted in a median error of approximately 1% of the total number of cell units. These results demonstrate the potential of our novel approach for quantifying cells in poorly labeled images. Compared to traditional Faster R-CNN, our method improved the average precision from 71% to 85% on the studied data set.

Establishment of Pancreatobiliary Cancer Zebrafish Avatars for Chemotherapy Screening

Background: Cancers of the pancreas and biliary tree remain one of the most aggressive oncological malignancies, with most patients relying on systemic chemotherapy. However, effective biomarkers to predict the best therapy option for each patient are still lacking. In this context, an assay able to evaluate individual responses prior to treatment would be of great value for clinical decisions. Here we aimed to develop such a model using zebrafish xenografts to directly challenge pancreatic cancer cells to the available chemotherapies. Methods: Zebrafish xenografts were generated from a Panc-1 cell line to optimize the pancreatic setting. Pancreatic surgical resected samples, without in vitro expansion, were used to establish zebrafish patient-derived xenografts (zAvatars). Upon chemotherapy exposure, zAvatars were analyzed by single-cell confocal microscopy. Results: We show that Panc-1 zebrafish xenografts are able to reveal tumor responses to both FOLFIRINOX and gemcitabine plus nanoparticle albumin-bound (nab)-paclitaxel in just 4 days. Moreover, we established pancreatic and ampullary zAvatars with patient-derived tumors representative of different histological types. Conclusion: Altogether, we provide a short report showing the feasibility of generating and analyzing with single-cell resolution zAvatars from pancreatic and ampullary cancers, with potential use for future preclinical studies and personalized treatment.

Zebrafish disease models in drug discovery: from preclinical modelling to clinical trials

Numerous drug treatments that have recently entered the clinic or clinical trials have their genesis in zebrafish. Zebrafish are well established for their contribution to developmental biology and have now emerged as a powerful preclinical model for human disease, as their disease characteristics, aetiology and progression, and molecular mechanisms are clinically relevant and highly conserved. Zebrafish respond to small molecules and drug treatments at physiologically relevant dose ranges and, when combined with cell-specific or tissue-specific reporters and gene editing technologies, drug activity can be studied at single-cell resolution within the complexity of a whole animal, across tissues and over an extended timescale. These features enable high-throughput and high-content phenotypic drug screening, repurposing of available drugs for personalized and compassionate use, and even the development of new drug classes. Often, drugs and drug leads explored in zebrafish have an inter-organ mechanism of action and would otherwise not be identified through targeted screening approaches. Here, we discuss how zebrafish is an important model for drug discovery, the process of how these discoveries emerge and future opportunities for maximizing zebrafish potential in medical discoveries.

Identifying patients eligible for PARP inhibitor treatment: from NGS-based tests to 3D functional assays

Within the past few years, poly (ADP-ribose) polymerase inhibitors (PARPi) have been added to the standard of care for cancer patients, mainly for those exhibiting specific genomic alterations in the homologous recombination (HR) pathway. Until now, patients who are eligible to receive PARPi have been identified using next-generation sequencing (NGS) of gene panels. However, NGS analyses do have some limitations, with a subset of patients with negative NGS-based results can exhibit a clinical benefit, responding positively to PARPi, despite the failure to detect dynamic and predictive biomarkers such as mutated BRCA1/2 genes. Furthermore, the sequencing of initial tumour does not allow to detect reversions or secondary mutations that can restore proficient HR and lead to PARPi resistance. Therefore, it is crucial to better identify patients who are likely to benefit from PARPi treatment. In this context, tumour models such as patient-derived xenografts or tumour-derived organoids could help to guide clinicians in their decision making as these models accurately mimic phenotypic and genetic tumour heterogeneity, and could reflect treatment response in an integrative manner. In this Perspective article, we provide an overview of the currently available NGS-based tests that enable the identification of patients who might benefit from PARPi, and outline breakthroughs and discoveries to expand this selection using 3D functional assays. Combining NGS with functional assays could facilitate the efficient identification of patients, thereby improving patient survival.

The Use of Zebrafish Xenotransplant Assays to Analyze the Role of lncRNAs in Breast Cancer

Breast cancer represents a great challenge since it is the first cause of death by cancer in women worldwide. LncRNAs are a newly described class of non-coding RNAs that participate in cancer progression. Their use as cancer markers and possible therapeutic targets has recently gained strength. Animal xenotransplants allows for in vivo monitoring of disease development, molecular elucidation of pathogenesis and the design of new therapeutic strategies. Nevertheless, the cost and complexities of mice husbandry makes medium to high throughput assays difficult. Zebrafishes (Danio rerio) represent a novel model for these assays, given the ease with which xenotransplantation trials can be performed and the economic and experimental advantages it offers. In this review we propose the use of xenotransplants in zebrafish to study the role of breast cancer lncRNAs using low to medium high throughput assays.

Zebrafish Avatar to Develop Precision Breast Cancer Therapies

BACKGROUND

Zebrafish (Danio rerio) is a vertebrate that has become a popular alternative model for the cellular and molecular study of human tumors and for drug testing and validating approaches. Notably, zebrafish embryos, thanks to their accessibility, allow rapid collection of in vivo results prodromal to validation in the murine models in respect to the 3R principles. The generation of tumor xenograft in zebrafish embryos and larvae, or zebrafish avatar, represents a unique opportunity to study tumor growth, angiogenesis, cell invasion and metastatic dissemination, interaction between tumor and host in vivo avoiding immunogenic rejection, representing a promising platform for the translational research and personalized therapies.

OBJECTIVE

In this mini-review we report recent advances in breast cancer research and drug testing that took advantage of the zebrafish xenograft model using both breast cancer cell lines and patient's biopsy.

CONCLUSION

Patient derived xenograft, together with the gene editing, the omics biotechnology, the in vivo time lapse imaging and the high-throughput screening that are already set up and largely used in zebrafish, could represent a step forward towards precision and personalized medicine in the breast cancer research field.

Zebrafish as an in vivo screening tool to establish PARP inhibitor efficacy

Double strand break (DSB) repair through Homologous Recombination (HR) is essential in maintaining genomic stability of the cell. Mutations in the HR pathway confer an increased risk for breast, ovarian, pancreatic and prostate cancer. PARP inhibitors (PARPi) are compounds that specifically target tumours deficient in HR. Novel PARPi are constantly being developed, but research is still heavily focussed on in vitro data, with mouse xenografts only being used in late stages of development. There is a need for assays that can: 1) provide in vivo data, 2) early in the development process of novel PARPi, 3) provide fast results and 4) at an affordable cost. Here we propose a combination of in vivo zebrafish assays to accurately quantify PARP inhibitor efficacy. We showed that PARPi display functional effects in zebrafish, generally correlating with their PARP trapping capacities. Furthermore, we displayed how olaparib mediated radiosensitization is conserved in our zebrafish model. These assays could aid the development of novel PARPi by providing early in vivo data. In addition, using zebrafish allows for high-throughput testing of combination therapies in search of novel treatment strategies.