Depletion of DNA damage binding protein 2 sensitizes triple-negative breast cancer cells to poly ADP-ribose polymerase inhibition by destabilizing Rad51

Deciphering the mechanisms of PARP inhibitor resistance in prostate cancer: Implications for precision medicine

Prostate cancer is a leading malignancy among men. While early-stage prostate cancer can be effectively managed, metastatic prostate cancer remains incurable, with a median survival of 3-5 years. The primary treatment for advanced prostate cancer is androgen deprivation therapy (ADT), but resistance to ADT often leads to castrationresistant prostate cancer (CRPC), presenting a significant therapeutic challenge. The advent of precision medicine has introduced promising new treatments, including PARP inhibitors (PARPi), which target defects in DNA repair mechanisms in cancer cells. PARPi have shown efficacy in treating advanced prostate cancer, especially in patients with metastatic CRPC (mCRPC) harboring homologous recombination (HR)-associated gene mutations. Despite these advancements, resistance to PARPi remains a critical issue. Here, we explored the primary mechanisms of PARPi resistance in prostate cancer. Key resistance mechanisms include homologous recombination recovery through reverse mutations in BRCA genes, BRCA promoter demethylation, and non-degradation of mutated BRCA proteins. The tumor microenvironment and overactivation of the base excision repair pathway also play significant roles in bypassing PARPi-induced synthetic lethality. In addition, we explored the clinical implications and therapeutic strategies to overcome resistance,emphasizing the need for precision medicine approaches. Our findings highlight the need for comprehensive strategies to improve PARPi sensitivity and effectiveness,ultimately aiming to extend patient survival and improve the quality of life for those with advanced prostate cancer. As our understanding of PARPi resistance evolves, more diverse and effective individualized treatment regimens will emerge.

DNA Damage Response Pharmacogenomic (DDR_PGx) Score Predicts Response to Chemotherapy Consisting of Gemtuzumab Ozogamicin in Pediatric AML: A Report from the Children's Oncology Group

PURPOSE

Comprehensive pharmacogenomics (PGx) evaluation of calicheamicin pathway to identify predictive PGx markers of response to gemtuzumab ozogamicin (GO) treatment in acute myeloid leukemia (AML).

EXPERIMENTAL DESIGN

SNPs in DNA damage response (DDR) pathway genes were tested for association with event-free survival (EFS), overall survival (OS), and risk of relapse after induction 1 (RR1) in patients treated with standard chemotherapy consisting of Ara-C, daunorubicin, and etoposide (ADE) with or without addition of GO on COG-AAML03P1 and COGAAAML0531 trials (ADE+GO, n = 755; ADE n = 470). SNPs with significant association with any endpoint within ADE+GO arm but not in the ADE arm were tested using multi-SNP modeling to develop DDR_PGx7 score.

RESULTS

Patients with low DDR_PGx7 score (<0) had significantly worse EFS [HR = 1.51, 95% confidence interval (CI: 1.21-1.89), P < 0.001], worse OS [HR = 1.59, 95% CI (1.22-2.08), P < 0.001], and higher RR1 [HR = 1.87, 95% CI (1.41-2.47), P < 0.0001] compared with patients with highDDR_PGx7 score (≥0)when treated withGO (ADE+GO cohort). However, no difference between low and high DDR_PGx7 score groups was observed for EFS, OS, and RR1 (all P > 0.3) in patients treated on ADE arm.

CONCLUSIONS

Our results suggest that DDR pathway-based pharmacogenomic score holds potential to predict outcome in patients treated with GO which consists of DNA damaging cytotoxin, calicheamicin. The potential clinical relevance for this score to personalize GO in AML requires further validation in independent and expanded cohorts.

Emerging strategies to overcome PARP inhibitors' resistance in ovarian cancer

The utilization of PARP inhibitors (PARPis) has significantly improved the prognosis for ovarian cancer patients. However, as the use of PARPis increases, the issue of PARPi resistance has become more prominent. Prolonged usage of PARPis can lead to the development of resistance in ovarian cancer, often mediated by mechanisms such as homologous recombination (HR) recovery, ultimately resulting in cancer relapse. Overcoming PARPi resistance in ovarian cancer is a pressing concern, aiming to enhance the clinical benefits of PARPi treatment and delay disease recurrence. Here, we summarize the mechanisms underlying PARPi resistance, methods for analyzing resistance, and strategies for overcoming it. Our goal is to inspire the development of more cost-effective and convenient methods for analyzing resistance mechanisms, as well as safer and more effective strategies to overcome resistance. These advancements can contribute to developing personalized approaches for treating ovarian cancer.

PARP inhibitor resistance mechanisms and PARP inhibitor derived imaging probes

INTRODUCTION

Poly(ADP-ribose) polymerase 1 (PARP1) inhibition has become a major target in anticancer therapy. While PARP inhibitors (PARPi) are approved for homologous recombination (HR) deficient cancers, therapeutic resistance is a challenge and PARPi are now being investigated in cancers lacking HR deficiencies. This creates a need to develop molecular and imaging biomarkers of PARPi response to improve patient selection and circumvent therapeutic resistance.

AREAS COVERED

PubMed and clinicaltrials.gov were queried for studies on PARPi resistance and imaging. This review summarizes established and emerging resistance mechanisms to PARPi, and the current state of imaging and theragnostic probes for PARPi, including fluorescently labeled and radiolabeled probes.

EXPERT OPINION

While progress has been made in understanding PARPi therapeutic resistance, clinical evidence remains lacking and relatively little is known regarding PARPi response outside of HR deficiencies. Continued research will clarify the importance of known biomarkers and resistance mechanisms in patient cohorts and the broader utility of PARPi. Progress has also been made in PARPi imaging, particularly with radiolabeled probes, and both imaging and theragnostic probes have now reached clinical validation. Reducing abdominal background signal from probe clearance will broaden their applicability, and improvements to molecular synthesis and radiation delivery will increase their utility.

Transcriptomic analysis of the antioxidant responses and immunomodulatory effects of dietary melatonin in red swamp crayfish (Procambarus clarkii)

This study aimed to investigate the effects of dietary melatonin (MT) levels on the antioxidant capacity, immunomodulatory, and transcriptional regulation of red swamp crayfish. Six experimental diets with different levels of MT (0, 22.5, 41.2, 82.7, 165.1, and 329.2 mg/kg diet) were fed to juvenile crayfish for 60 d. The transcriptome data of the control group and the group supplemented with dietary MT at 165.1 mg/kg were obtained using RNA-seq. In total, 3653 differentially expressed genes (2082 up-regulated and 1571 down-regulated) were identified. Pathways and genes related to antioxidant immune and growth performance were verified by qRT-PCR. The total hemocyte count, phagocytosis rate, and respiratory burst were significantly increased in the MT (165.1 mg/kg) group compared to the control group. Analysis of antioxidant immune-related enzymes in the hepatopancreas demonstrated that dietary MT (165.1 mg/kg) significantly increased activities of catalase, superoxide dismutase, glutathione reductase, and glutathione peroxidase and significantly decreased aspartate aminotransferase and alanine aminotransferase activity. At the transcriptional level, dietary MT up-regulated expression levels of genes associated with antioxidant immune and development, which included toll-like receptors, Crustin, C-type lectin, and so on. To conclude, MT could be used as a supplement in crayfish feed to increase immunity and antioxidant capacity and according to the broken line regression, the ideal MT concentration was the 159.02 mg/kg. Overall, this study demonstrates the role of melatonin in the antioxidant responses and immunomodulatory of Procambarus clarkii, laying the foundation for the development of melatonin as a feed additive in the aquaculture of this species.

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.

A protein with broad functions: damage-specific DNA-binding protein 2

Damage-specific DNA-binding protein 2 (DDB2) was initially identified as a component of the damage-specific DNA-binding heterodimeric complex, which cooperates with other proteins to repair UV-induced DNA damage. DDB2 is involved in the occurrence and development of cancer by affecting nucleotide excision repair (NER), cell apoptosis, and premature senescence. DDB2 also affects the sensitivity of cancer cells to radiotherapy and chemotherapy. In addition, a recent study found that DDB2 is a pathogenic gene for hepatitis and encephalitis. In recent years, there have been few relevant literature reports on DDB2, so there is still room for further research about it. In this paper, the molecular mechanisms of different biological processes involving DDB2 are reviewed in detail to provide theoretical support for research on drugs that can target DDB2.

EGFR Transgene Stimulates Spontaneous Formation of MCF7 Breast Cancer Cells Spheroids with Partly Loss of HER3 Receptor

Multicellular spheroids with 3D cell-cell interactions are a useful model to simulate the growth conditions of cancer. There is evidence that in tumor spheroids, the expression of various essential molecules is changed compared to the adherent form of cell cultures. These changes include growth factor receptors and ABC transporters and result in the enhanced invasiveness of the cells and drug resistance. It is known that breast adenocarcinoma MCF7 cells can spontaneously form 3D spheroids and such spheroids are characterized by high expression of EGFR/HER2, while the natural phenotype of MCF7 cells is EGFRlow/HER2low. Therefore, it was interesting to reveal if high epidermal growth factor receptor (EGFR) expression is sufficient for the conversion of adherent MCF7 to spheroids. In this study, an MCF7 cell line with high expression of EGFR was engineered using the retroviral transduction method. These MCF7-EGFR cells assembled in spheroids very quickly and grew predominantly as a 3D suspension culture with no special plates, scaffolds, growth supplements, or exogenous matrixes. These spheroids were characterized by a rounded shape with a well-defined external border and 100 µM median diameter. The sphere-forming ability of MCF7-EGFR cells was up to 5 times stronger than in MCF7wt cells. Thus, high EGFR expression was the initiation factor of conversion of adherent MCF7wt cells to spheroids. MCF7-EGFR spheroids were enriched by the cells with a cancer stem cell (CSC) phenotype CD24-/low/CD44- in comparison with parental MCF7wt cells and MCF7-EGFR adhesive cells. We suppose that these properties of MCF7-EGFR spheroids originate from the typical features of parental MCF7 cells. We showed the decreasing of HER3 receptors in MCF7-EGFR spheroids compared to that in MCFwt and in adherent MCF7-EGFR cells, and the same decrease was observed in the MCF7wt spheroids growing under the growth factors stimulation. To summarize, the expression of EGFR transgene in MCF7 cells stimulates rapid spheroids formation; these spheroids are enriched by CSC-like CD24-/CD44- cells, they partly lose HER3 receptors, and are characterized by a lower potency in drug resistance pomp activation compared to MCF7wt. These MCF7-EGFR spheroids are a useful cancer model for the development of anticancer drugs, including EGFR-targeted therapeutics.

Biomarkers in Triple-Negative Breast Cancer: State-of-the-Art and Future Perspectives

Triple-negative breast cancer (TNBC) is a heterogeneous group of tumors characterized by aggressive behavior, high risk of distant recurrence, and poor survival. Chemotherapy is still the main therapeutic approach for this subgroup of patients, therefore, progress in the treatment of TNBC remains an important challenge. Data derived from molecular technologies have identified TNBCs with different gene expression and mutation profiles that may help developing targeted therapies. So far, however, only a few of these have shown to improve the prognosis and outcomes of TNBC patients. Robust predictive biomarkers to accelerate clinical progress are needed. Herein, we review prognostic and predictive biomarkers in TNBC, discuss the current evidence supporting their use, and look at the future of this research field.

PARP inhibitor resistance: the underlying mechanisms and clinical implications

Due to the DNA repair defect, BRCA1/2 deficient tumor cells are more sensitive to PARP inhibitors (PARPi) through the mechanism of synthetic lethality. At present, several PAPRi targeting poly (ADP-ribose) polymerase (PARP) have been approved for ovarian cancer and breast cancer indications. However, PARPi resistance is ubiquitous in clinic. More than 40% BRCA1/2-deficient patients fail to respond to PARPi. In addition, lots of patients acquire PARPi resistance with prolonged oral administration of PARPi. Homologous recombination repair deficient (HRD), as an essential prerequisite of synthetic lethality, plays a vital role in killing tumor cells. Therefore, Homologous recombination repair restoration (HRR) becomes the predominant reason of PARPi resistance. Recently, it was reported that DNA replication fork protection also contributed to PARPi resistance in BRCA1/2-deficient cells and patients. Moreover, various factors, such as reversion mutations, epigenetic modification, restoration of ADP-ribosylation (PARylation) and pharmacological alteration lead to PARPi resistance as well. In this review, we reviewed the underlying mechanisms of PARP inhibitor resistance in detail and summarized the potential strategies to overcome PARPi resistance and increase PARPi sensitivity.

Bioinformatics Analysis Reveals Biomarkers With Cancer Stem Cell Characteristics in Lung Squamous Cell Carcinoma

Background

Tumor stem cells play important roles in the survival, proliferation, metastasis and recurrence of tumors. We aimed to identify new prognostic biomarkers for lung squamous cell carcinoma (LUSC) based on the cancer stem cell theory.

Methods

RNA-seq data and relevant clinical information were downloaded from The Cancer Genome Atlas (TCGA) database. Weighted gene coexpression network analysis (WGCNA) was applied to identify significant modules and hub genes, and prognostic signatures were constructed with the prognostic hub genes.

Results

LUSC patients in the TCGA database have higher mRNA expression-based stemness index (mRNAsi) in tumor tissue than in adjacent normal tissue. In addition, some clinical features and outcomes were highly correlated with the mRNAsi. WGCNA revealed that the pink and yellow modules were the most significant modules related to the mRNAsi; the top 10 hub genes in the pink module were enriched mostly in epidermal development, the secretory granule membrane, receptor regulator activity and the cytokine-cytokine receptor interaction. The protein–protein interaction (PPI) network revealed that the top 10 hub genes were significantly correlated with each other at the transcriptional level. In addition, the top 10 hub genes were all highly expressed in LUSC, and some were differentially expressed in different TNM stages. Regarding the survival analysis, the nomogram of a prognostic signature with three hub genes showed high predictive value.

Conclusion

mRNAsi-related hub genes could be a potential biomarker of LUSC.

Emerging Roles of DDB2 in Cancer

Damage-specific DNA-binding protein 2 (DDB2) was originally identified as a DNA damage recognition factor that facilitates global genomic nucleotide excision repair (GG-NER) in human cells. DDB2 also contributes to other essential biological processes such as chromatin remodeling, gene transcription, cell cycle regulation, and protein decay. Recently, the potential of DDB2 in the development and progression of various cancers has been described. DDB2 activity occurs at several stages of carcinogenesis including cancer cell proliferation, survival, epithelial to mesenchymal transition, migration and invasion, angiogenesis, and cancer stem cell formation. In this review, we focus on the current state of scientific knowledge regarding DDB2 biological effects in tumor development and the underlying molecular mechanisms. We also provide insights into the clinical consequences of DDB2 activity in cancers.

Depletion of DNA damage binding protein 2 sensitizes triple-negative breast cancer cells to poly ADP-ribose polymerase inhibition by destabilizing Rad51

Poly ADP‐ribose polymerase inhibitors (PARPi) have shown promising therapeutic efficacy in triple‐negative breast cancer (TNBC) patients. However, resistance ultimately develops, preventing a curative effect from being attained. Extensive investigations have indicated the diversity in the mechanisms underlying the PARPi sensitivity of breast cancer. In this study, we found that DNA damage binding protein 2 (DDB2), a DNA damage‐recognition factor, could protect TNBC cells from PARPi by regulating DNA double‐strand break repair through the homologous recombination pathway, whereas the depletion of DDB2 sensitizes TNBC cells to PARPi. Furthermore, we found that DDB2 was able to stabilize Rad51 by physical association and disrupting its ubiquitination pathway‐induced proteasomal degradation. These findings highlight an essential role of DDB2 in modulating homologous recombination pathway activity and suggest a promising therapeutic target for TNBC.