Drug Resistance Updates

TRAIL-driven targeting and reversing cervical cancer radioresistance by seleno-nanotherapeutics through regulating cell metabolism

Recently, radioresistance has become a major obstacle in the radiotherapy of cervical cancer. To demonstrate enhanced radiosensitization against radioresistant cervical cancer, radioresistant cervical cancer cell line was developed and the mechanism of radioresistance was explored. Due to the overexpression of (death receptor 5, DR5) in cervical cancer, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-overexpressed cervical cancer cell membrane-camouflaged Cu

Overcoming PARPi resistance: Preclinical and clinical evidence in ovarian cancer

Ovarian cancer is the fifth cause of cancer-related deaths in women with high grade serous carcinoma (HGSOC) representing the most common histological subtype. Approximately 50 % of HGSOC are characterized by deficiency in homologous recombination (HR), one of the main cellular pathways to repair DNA double strand breaks and one of the well-described mechanisms is the loss of function of the BRCA1 or BRCA2 genes. Inhibition of the poly-ADP-ribose polymerase (PARP) is synthetic lethal with HR deficiency and the use of PARP inhibitors (PARPi) has significantly improved the outcome of patients with HGSOC with a greater benefit in patients with BRCA1/2 deficient tumors. However, intrinsic or acquired resistance to PARPi inevitably occurs in most HGSOC patients. Distinct heterogeneous mechanisms underlying the resistance to PARPi have been described, including a decrease in intracellular drug levels due to upregulation of multidrug efflux pumps, loss of expression/inactivating mutations in the PARP1 protein, restoration of HR and the protection of the replicative fork. Deciphering the molecular mechanisms of resistance to PARPi is of paramount importance towards the development of new treatment strategies and/or novel pharmacological agents to overcome this chemoresistance and optimize the treatment regimen for individual HGSOC patients. The current review summarizes the mechanisms underlying the resistance to PARPi, the available preclinical and clinical data on new combination treatment strategies (with chemotherapy, anti-angiogenic agents and immune checkpoint inhibitors) as well as agents under investigation which target the DNA damage response.

ZBP1 antagonizes MRE11-mediated DNA end resection and confers synthetic lethality to PARP inhibition in ovarian cancer

ZBP1, a classic pattern recognition receptor (PRR), has been implicated in regulating programmed cell death and the innate immune response. However, the role of ZBP1 in the nucleus remains largely undefined. Here, we found that nuclear ZBP1 localizes to the site of DNA double-stranded breaks (DSBs) following DNA damage and impairs homologous recombination (HR) repair through its interaction with MRE11. ZBP1 interacts with MRE11 through RHIM A and B domains and inhibits the enzymatic activity of MRE11, ultimately leading to the suppression of HR and DNA damage repair (DDR). These processes are initiated via ATM-mediated ZBP1 phosphorylation at S106. Consistent with these findings, in vitro and in vivo models both exhibit increased sensitivity to PARP inhibitor treatment following ZBP1 overexpression. Furthermore, in our neoadjuvant niraparib monotherapy study (NCT05407841) higher ZBP1 expression correlates with better response to PARP inhibition and prolonged PFS in high-grade serous ovarian cancer (HGSOC). This study describes a novel function of ZBP1 for regulating HR, which confers synthetic lethality to PARP inhibition in ovarian cancer. ZBP1 thus serves as a potential therapy target and biomarker of response to PARP inhibitors and potentially other therapeutic agents such as platin analogs that are synthetically lethal with defective HR.

Syk-dependent homologous recombination activation promotes cancer resistance to DNA targeted therapy

Enhanced DNA repair is an important mechanism of inherent and acquired resistance to DNA targeted therapies, including poly ADP ribose polymerase (PARP) inhibition. Spleen associated tyrosine kinase (Syk) is a non-receptor tyrosine kinase acknowledged for its regulatory roles in immune cell function, cell adhesion, and vascular development. This study presents evidence indicating that Syk expression in high-grade serous ovarian cancer and triple-negative breast cancers promotes DNA double-strand break resection, homologous recombination (HR), and subsequent therapeutic resistance. Our investigations reveal that Syk is activated by ATM following DNA damage and is recruited to DNA double-strand breaks by NBS1. Once localized to the break site, Syk phosphorylates CtIP, a pivotal mediator of resection and HR, at Thr-847 to promote repair activity, particularly in Syk-expressing cancer cells. Inhibition of Syk or its genetic deletion impedes CtIP Thr-847 phosphorylation and overcomes the resistant phenotype. Collectively, our findings suggest a model wherein Syk fosters therapeutic resistance by promoting DNA resection and HR through a hitherto uncharacterized ATM-Syk-CtIP pathway. Moreover, Syk emerges as a promising tumor-specific target to sensitize Syk-expressing tumors to PARP inhibitors, radiation and other DNA-targeted therapies.

A novel SIK2 inhibitor SIC-19 exhibits synthetic lethality with PARP inhibitors in ovarian cancer

Ovarian cancer patients with HR proficiency (HRP) have had limited benefits from PARP inhibitor treatment, highlighting the need for improved therapeutic strategies. In this study, we developed a novel SIK2 inhibitor, SIC-19, and investigated its potential to enhance the sensitivity and expand the clinical utility of PARP inhibitors in ovarian cancer. The SIK2 protein was modeled using a Molecular Operating Environment (MOE), and the most favorable model was selected based on a GBVI/WSA dG scoring function. The Chembridge Compound Library was screened, and the top 20 candidate compounds were tested for their interaction with SIK2 and downstream substrates, AKT-pS473 and MYLK-pS343. SIC-19 emerged as the most promising drug candidate and was further evaluated using multiple assays. SIC-19 exhibited selective and potent inhibition of SIK2, leading to its degradation through the ubiquitination pathway. The IC50 of SIC-19 correlated inversely with endogenous SIK2 expression in ovarian cancer cell lines. Treatment with SIC-19 significantly inhibited cancer cell growth and sensitized cells to PARP inhibitors in vitro, as well as in ovarian cancer organoids and xenograft models. Mechanistically, SIK2 knockdown and SIC-19 treatment reduced RAD50 phosphorylation at Ser635, prevented nuclear translocation of RAD50, disrupted nuclear filament assembly, and impaired DNA homologous recombination repair, ultimately inducing apoptosis. These findings highlight the crucial role of SIK2 in the DNA HR repair pathway and demonstrate the significant PARP inhibitor sensitization achieved by SIC-19 in ovarian cancer. SIC-19, a novel SIK2 inhibitor, effectively inhibits tumor cell growth in ovarian cancer by interfering with RAD50-mediated DNA HR repair. Furthermore, SIC-19 enhances the efficacy of PARP inhibitors, providing a promising therapeutic strategy to improve outcomes for ovarian cancer patients.

Overexpression of ABCC1 and ABCG2 confers resistance to talazoparib, a poly (ADP-Ribose) polymerase inhibitor

The overexpression of ABC transporters on cancer cell membranes is one of the most common causes of multidrug resistance (MDR). This study investigates the impact of ABCC1 and ABCG2 on the resistance to talazoparib (BMN-673), a potent poly (ADP-ribose) polymerase (PARP) inhibitor, in ovarian cancer treatment. The cell viability test was used to indicate the effect of talazoparib in different cell lines. Computational molecular docking analysis was conducted to simulate the interaction between talazoparib and ABCC1 or ABCG2. The mechanism of talazoparib resistance was investigated by constructing talazoparib-resistant subline A2780/T4 from A2780 through drug selection with gradually increasing talazoparib concentration. Talazoparib cytotoxicity decreased in drug-selected or gene-transfected cell lines overexpressing ABCC1 or ABCG2 but can be restored by ABCC1 or ABCG2 inhibitors. Talazoparib competitively inhibited substrate drug efflux activity of ABCC1 or ABCG2. Upregulated ABCC1 and ABCG2 protein expression on the plasma membrane of A2780/T4 cells enhances resistance to other substrate drugs, which could be overcome by the knockout of either gene. In vivo experiments confirmed the retention of drug-resistant characteristics in tumor xenograft mouse models. The therapeutic efficacy of talazoparib in cancer may be compromised by its susceptibility to MDR, which is attributed to its interactions with the ABCC1 or ABCG2 transporters. The overexpression of these transporters can potentially diminish the therapeutic impact of talazoparib in cancer treatment.

Targeting NAT10 attenuates homologous recombination via destabilizing DNA:RNA hybrids and overcomes PARP inhibitor resistance in cancers

Single-cell transcriptome analysis of patient-derived organoids captures inter- and intratumor heterogeneity and uncovers targetable pathways in high grade serous ovarian cancer

High grade serous ovarian cancer (HGSOC) is the most aggressive subtype of ovarian cancer. HGSOC is characterized by high inter- and intra-tumoral heterogeneity, which contributes to chemotherapy resistance. Patient-derived organoids (PDOs) are valuable preclinical models to elucidate the biology of human cancers and to test their response to treatments. This study aims at characterizing the cellular heterogeneity of PDOs and to uncover vulnerabilities of chemotherapy resistant HGSOC. Single-cell transcriptomics of PDOs developed from biopsies of platinum-resistant and platinum-sensitive HGSOC. Chemotherapeutic treatments of HGSOC PDOs and of ascitic-derived ovarian cancer cells and immunohistochemistry analyses of tissues from independent HGSOC patients. HGSOC PDOs comprise subclusters of cells exhibiting different transcriptional states and patient-specific signatures. Proliferative and non-proliferative subclusters co-exist in PDOs and their relative proportion is altered by chemotherapy. Proliferative cell sub-populations exhibit expression of cell cycle and DNA damage response related genes, whereas non-proliferative sub-populations display inflammatory signatures. Furthermore, sensitivity to platinum-based treatments was inversely correlated with oxidative phosphorylation (OXHPOS) in PDOs, indicating a metabolic switch associated with chemoresistance. Accordingly, platinum-resistant PDOs and ascitic HGSOC cells show higher sensitivity to OXHPOS inhibition. We found that neoadjuvant chemotherapy (NACT) directly up-regulates oncogenic and metabolic pathways that are involved in development of recurrence, such as the MYC and OXPHOS genes. NACT also induces the expression of major histocompatibility complex type II (MHC-II) molecules. Immunohistochemistry confirmed MHC-II up-regulation in post-NACT biopsies, indicating that tumour cells mount a general antigen-presenting response upon chemotherapy, associated with recruitment of infiltrating immune cells. PDOs maintain the inter- and intra-tumoral cellular heterogeneity of HGSOC. Chemotherapy targets proliferative cell subclusters, sparing non-proliferative ones. Dependency on OXPHOS represents an actionable vulnerability in PDOs, which can be exploited to hijack chemoresistance. Sequential chemotherapy and immunotherapy may also improve clinical response of HGSOC patients.

Zebrafish patient-derived xenograft system for predicting carboplatin resistance and metastasis of ovarian cancer

Ovarian cancer (OC) remains a significant challenge in oncology due to high rates of drug resistance and disease relapse following standard treatment with surgery and platinum-based chemotherapy. Despite the widespread use of these treatments, no effective biomarkers currently exist to identify which patients will respond favorably to therapy. This study introduces a zebrafish patient-derived xenograft (PDX) system, capable of replicating both the carboplatin response and metastatic behavior observed in OC patients, within a rapid 3-day assay period. Two OC cell lines: carboplatin-sensitive (A2780) and resistant (OVCAR8) were used to assess differential responses to treatment in murine and zebrafish xenograft models. Tumor tissues from 16 OC patients were implanted into zebrafish embryos to test carboplatin responses and predict metastasis. Additionally, eight clinical OC samples were directly implanted into zebrafish embryos as part of a proof-of-concept demonstration. The zebrafish xenografts accurately reflected the carboplatin sensitivity and resistance patterns seen in in vitro and murine models. The zebrafish PDX model demonstrated a 67 % success rate for implantation and a 100 % success rate for engraftment. Notably, the model effectively distinguished between metastatic and non-metastatic disease, with an area under the ROC curve (AUC) of 0.818. Furthermore, the zebrafish PDX model showed a high concordance with patient-specific responses to carboplatin. This zebrafish PDX model offers a fast, accurate, and clinically relevant platform for evaluating carboplatin response and predicting metastasis in OC patients. It holds significant potential for advancing personalized medicine, allowing for more precise therapeutic outcome predictions and individualized treatment strategies.

CYP1B1 promotes PARPi-resistance via histone H1.4 interaction and increased chromatin accessibility in ovarian cancer

Ovarian cancer is the most lethal gynecological cancer and presents significant therapeutic challenges. The discovery of synthetic lethality between PARP inhibitors (PARPi) and homologous recombination deficiency marked a new era in treating BRCA1/2-mutated tumors. However, PARPi resistance remains a major clinical challenge. RNA sequencing was used to identify genes altered by PARPi treatment and LC-MS was used to detect proteins interacting with CYP1B1. Resistance mechanisms were explored through ATAC-seq and gene expression manipulation. Additional techniques, including micrococcal nuclease digestion assays, DAPI staining, and fluorescence microscopy, were used to assess changes in nuclear morphology and chromatin accessibility. The gradual exposure of Olaparib has developed a PARPi-resistant cell line, A2780-OlaR, which exhibits significant upregulation of CYP1B1 at both RNA and protein levels. Down-regulating CYP1B1 expression or using specific inhibitors decreased the cellular response to Olaparib. Linker histone H1.4 was identified as associated with CYP1B1. ATAC-seq showed differential chromatin accessibility between A2780-OlaR and parental cells, indicating that the downregulation of H1.4 was associated with increased chromatin accessibility and higher cell viability after Olaparib treatment. Our findings reveal a novel role for CYP1B1 in driving PARPi resistance through distinct molecular mechanisms in A2780-OlaR. This study highlights the importance of chromatin accessibility in PARPi efficacy and suggests the CYP1B1/H1.4 axis as a promising therapeutic target for overcoming drug resistance in ovarian cancer, offering potentially therapeutic benefits.