DNA damage response proteins synergistically affect the cancer prognosis and resistance

HMGB1 promotes chemoresistance in small cell lung cancer by inducing PARP1-related nucleophagy

INTRODUCTION

Small cell lung cancer (SCLC) is prone to chemoresistance, which is closely related to genome homeostasis-related processes, such as DNA damage and repair. Nucleophagy is the elimination of specific nuclear substances by cells themselves and is responsible for maintaining genome and chromosome stability. However, the roles of nucleophagy in tumour chemoresistance have not been investigated.

OBJECTIVES

The aim of this work was to elucidate the mechanism of chemoresistance in SCLC and reverse this chemoresistance.

METHODS

RNA-seq data from SCLC cohorts, chemosensitive SCLC cells and the corresponding chemoresistant cells were used to discover genes associated with chemoresistance and patient prognosis. In vitro and in vivo experiments were performed to verify the effect of high-mobility group box 1 (HMGB1) knockdown or overexpression on the chemotherapeutic response in SCLC. The regulatory effect of HMGB1 on nucleophagy was then investigated by coimmunoprecipitation (co-IP) and mass spectrometry (MS), and the underlying mechanism was explored using pharmacological inhibitors and mutant proteins.

RESULTS

HMGB1 is a factor indicating poor prognosis and promotes chemoresistance in SCLC. Mechanistically, HMGB1 significantly increases PARP1-LC3 binding to promote nucleophagy via PARP1 PARylation, which leads to PARP1 turnover from DNA lesions and chemoresistance. Furthermore, chemoresistance in SCLC can be attenuated by blockade of the PARP1-LC3 interaction or PARP1 inhibitor (PARPi) treatment.

CONCLUSIONS

HMGB1 can induce PARP1 self-modification, which promotes the interaction of PARP1 with LC3 to promote nucleophagy and thus chemoresistance in SCLC. HMGB1 could be a predictive biomarker for the PARPi response in patients with SCLC. Combining chemotherapy with PARPi treatment is an effective therapeutic strategy for overcoming SCLC chemoresistance.

Inhibition of Cell Proliferation and Cell Death by Apigetrin through Death Receptor-Mediated Pathway in Hepatocellular Cancer Cells

Epidemiologic research recommends using flavonoids in the diet due to their overall health benefits. Apigetrin (Apigenin 7-O-glucoside) is a glycoside phytonutrient found in fruits and vegetables and known for different biological activities such as antioxidant and anti-inflammatory properties. Hepatocellular cancer (HCC) is a major health concern because of its adverse prognosis and side effects of chemotherapeutic agents. In the present study, we determine the impact of apigetrin on HepG2 cells and its cell death mechanism. Apigetrin reduced HepG2 cell proliferation with morphological changes and floating cells in treated cells. Colony formation and wound healing assays showed a reduced cell number in treatment groups. Further, we checked for the cell cycle through flow cytometry to understand the cell death mechanism. Apigetrin induced G2/M phase arrest in HepG2 cells by regulating Cyclin B1 and CDK1 protein levels in HepG2 cells. Annexin V and propidium iodide (PI) staining was performed to confirm the apoptotic cell population in treated groups. At the higher concentration, apigetrin showed a late apoptotic population in HepG2 cells. Chromatin condensation was also found in the treatment groups. Western blot analysis showed an increased expression of extrinsic apoptotic proteins such as FasL, Cleaved caspase 8, Cleaved caspase 3, and cleavage of PARP. In comparison, intrinsic apoptotic pathway markers showed no changes in Bax, Bcl-xL, and Cleaved caspase 9. Altogether, these findings strongly indicate that apigetrin causes cell death in HepG2 cells through the extrinsic apoptotic pathway, and that the intrinsic/mitochondrial pathway is not involved.

RAD54L promotes progression of hepatocellular carcinoma via the homologous recombination repair pathway

Hepatocellular carcinoma (HCC) is a malignant tumor with high incidence worldwide. The underlying mechanisms remain poorly understood. The DNA metabolic process of homologous recombination repair (HRR) has been linked to a high probability of tumorigenesis and drug resistance. This study aimed to determine the role of HRR in HCC and identify critical HRR-related genes that affect tumorigenesis and prognosis. A total of 613 tumor and 252 para-carcinoma tissue samples were collected from The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC) to obtain differentially expressed genes (DEGs). HRR-related genes were assessed using gene enrichment and pathway analyses. Survival analysis was performed using the Kaplan-Meier method in the Gene Expression Profiling Interactive Analysis portal. The levels of RAD54L in the HRR pathway were detected by RT-qPCR and western blotting in para-carcinoma and HCC tissues and in L02 normal human liver cells and Huh7 HCC cells. Immunohistochemistry (IHC) was performed on the clinical specimens to determine the connection between gene expression and clinical features. Bioinformatics analysis revealed that the HRR pathway was enriched in HCC tissues. Upregulation of HRR pathway DEGs in HCC tissues was positively correlated with tumor pathological staging and negatively associated with patient overall survival. RAD54B, RAD54L, and EME1 genes in the HRR pathway were screened as markers for predicting HCC prognosis. RT-qPCR identified RAD54L as the most significantly expressed of the three genes. Western blotting and IHC quantitative analyses further demonstrated that RAD54L protein levels were higher in HCC tissues. IHC analysis of 39 pairs of HCC and para-carcinoma tissue samples also revealed an association between RAD54L and Edmondson-Steiner grade and the proliferation-related gene Ki67. The collective findings positively correlate RAD54L in the HRR signaling pathway with HCC staging and implicate RAD54L as a marker to predict HCC progression.

Ultra-sensitive biosensor based on CRISPR-Cas12a and Endo IV coupled DNA hybridization reaction for uracil DNA glycosylase detection and intracellular imaging

As an essential biomarker associated with various diseases, Uracil-DNA Glycosylase (UDG) detection is vital for disease diagnosis, treatment selection, and prognosis assessment. In recent years, the signal amplification effect of the CRISPR-Cas12a trans-cleaved single-stranded DNA probe has provided an available strategy for constructing highly sensitive biosensors. However, its superior trans-cleavage activity has become a "double-edged sword" for building biosensors that can amplify the target signal while also amplifying the leakage signal, causing out of control. Therefore, the construction of structurally simple, extremely low-background, highly sensitive CRISPR-Cas12a-based biosensors is an urgent bottleneck problem in the field. Here, we applied CRISPR-Cas12a with a DNA hybridization reaction to develop a simple, rapid, low background, and highly sensitive method for UDG activity detection. It has no PAM restriction and the detection limit is as low as 2.5 × 10^-6 U/mL. As far as we know, this method is one of the most sensitive methods for UDG detection. We also used this system to analyze UDG activity in tumor cells (LOD: 1 cell/uL) and to evaluate the ability to screen for UDG inhibitors. Furthermore, we verified the possibility of intracellular UDG activity imaging by transfecting the biosensors to the cells. We believe this novel sensor has good clinical application prospects and will effectively broaden the application space of CRISPR-Cas12a.

Nanomedicines for Overcoming Cancer Drug Resistance

Clinically, cancer drug resistance to chemotherapy, targeted therapy or immunotherapy remains the main impediment towards curative cancer therapy, which leads directly to treatment failure along with extended hospital stays, increased medical costs and high mortality. Therefore, increasing attention has been paid to nanotechnology-based delivery systems for overcoming drug resistance in cancer. In this respect, novel tumor-targeting nanomedicines offer fairly effective therapeutic strategies for surmounting the various limitations of chemotherapy, targeted therapy and immunotherapy, enabling more precise cancer treatment, more convenient monitoring of treatment agents, as well as surmounting cancer drug resistance, including multidrug resistance (MDR). Nanotechnology-based delivery systems, including liposomes, polymer micelles, nanoparticles (NPs), and DNA nanostructures, enable a large number of properly designed therapeutic nanomedicines. In this paper, we review the different mechanisms of cancer drug resistance to chemotherapy, targeted therapy and immunotherapy, and discuss the latest developments in nanomedicines for overcoming cancer drug resistance.