DNA repair biomarkers to guide usage of combined PARP inhibitors and chemotherapy: A meta-analysis and systematic review

SETD1A-dependent EME1 transcription drives PARPi sensitivity in HR deficient tumour cells

BACKGROUND

Cells deficient in DNA repair factors breast cancer susceptibility 1/2 (BRCA1/2) or ataxia-telangiectasia mutated (ATM) are sensitive to poly-ADP ribose polymerase (PARP) inhibitors. Building on our previous findings, we asked how the lysine methyltransferase SETD1A contributed to PARP inhibitor-mediated cell death in these contexts and determined the mechanisms responsible.

METHODS

We used cervical, breast, lung and ovarian cancer cells bearing mutations in BRCA1 or ATM and depleted SETD1A using siRNA or CRISPR/Cas9. We assessed the effects of the PARPi Olaparib on cell viability, homologous recombination, and DNA repair. We assessed underlying transcriptional perturbations using RNAseq. We used The Cancer Genomics Atlas (TCGA) and DepMap to investigate patient survival and cancer cell characteristics.

RESULTS

Loss of SETD1A from both BRCA1-deficient and ATM-deficient cancer cells was associated with resistance to Olaparib, explained by partial restoration of homologous recombination. Mechanistically, SETD1A-dependent transcription of the crossover junction endonuclease EME1 correlated with sensitivity to Olaparib in these cells. Accordingly, when SETD1A or EME1 was lost, BRCA1 or ATM-mutated cells became resistant to Olaparib, and homologous recombination was partially restored.

CONCLUSIONS

Loss of SETD1A or EME1 drives cellular resistance to Olaparib in certain genetic contexts and may help explain why patients develop resistance to PARP inhibitors in the clinic.

The Potential of PARP Inhibitors as Antitumor Drugs and the Perspective of Molecular Design

PARP (poly-ADP ribose polymerase) has received widespread attention in cancer treatment. Research has shown that PARP plays a crucial role in DNA damage repair and has become a popular target for drug design. Based on the mechanism of "synthetic lethality", multiple PARPis (PARP inhibitors) have been launched for the treatment of BRCA deficient tumors. For example, the approved PARPis have shown significant potential in cancer treatment, particularly in breast cancer and cancers associated with BRCA1/BRCA2 deficiencies. However, the clinical efficacy and safety of PARP inhibitors in different cancers remain issues that cannot be overlooked. The design of PARPis aims to eliminate their resistance and broaden their application scope. Designing selective PARP-1 inhibitors is also a potential strategy. PROTACs (Proteolysis Targeting Chimeras) to degrade PARP have become a potential novel cancer treatment strategy.

Real-world efficacy and safety of combined first-line treatment with PARP inhibitors and novel hormonal therapy in mCRPC patients with HRR gene mutations

Objective

This study evaluated the real-world efficacy and safety of combining PARP inhibitors with novel hormonal therapy (NHT) as a first-line treatment in Chinese patients with metastatic castration-resistant prostate cancer (mCRPC) harboring homologous recombination repair (HRR) gene mutations.

Methods

We enrolled 41 mCRPC patients who received at least 1 month of combined treatment with PARP inhibitors and NHT. Patients were divided into two groups: Cohort A (mutations in BRCA1, BRCA2, or ATM genes) and Cohort B (mutations in other HRR genes). The primary endpoint was imaging-based progression-free survival (PFS), with secondary endpoints including objective response rate (ORR), disease control rate (DCR), overall survival (OS), PSA50 response, and adverse events (AEs). To ensure accurate research results and control confounding factors, we will employ multivariate Cox proportional hazards models to evaluate key variables affecting mCRPC patient survival outcomes.

Results

This study enrolled 41 patients, 22 in Cohort A and 19 in Cohort B. The median PFS for all patients was 21.8 months, and the median OS had yet to be reached. The overall ORR was 48.8%, and the DCR was 61.0%. Specifically, the median PFS for Cohort A was 21.8 months compared to 14.5 months for Cohort B. The median OS had yet to be reached for either cohort. Regarding efficacy, 81.8% of patients in Cohort A and 73.7% in Cohort B achieved a PSA50 response. Imaging assessments showed ORRs of 54.6% for Cohort A and 42.1% for Cohort B, with DCRs of 72.7% and 47.4%, respectively. 85.4% of patients experienced grade 1 or 2 adverse events, and 51.2% encountered grade 3 or 4. In the multivariate Cox regression analysis focusing on PFS, the Gleason score was identified as a significant predictor (HR = 5.8, 95% CI: 1.65-20.2, p = 0.006).

Conclusion

Combined first-line treatment with PARP inhibitors and NHT is effective and well-tolerated in mCRPC patients with HRR gene mutations, particularly those with BRCA1, BRCA2, or ATM mutations. These findings underscore the potential of this therapeutic combination in managing mCRPC in the Chinese population, suggesting a favorable outcome for those with specific genetic backgrounds.

Relationship between clonal evolution and drug resistance in bladder cancer: A genomic research review

Bladder cancer stands as a prevalent global malignancy, exhibiting notable sex-based variations in both incidence and prognosis. Despite substantial strides in therapeutic approaches, the formidable challenge of drug resistance persists. The genomic landscape of bladder cancer, characterized by intricate clonal heterogeneity, emerges as a pivotal determinant in fostering this resistance. Clonal evolution, encapsulating the dynamic transformations within subpopulations of tumor cells over time, is implicated in the emergence of drug-resistant traits. Within this review, we illuminate contemporary insights into the role of clonal evolution in bladder cancer, elucidating its influence as a driver in tumor initiation, disease progression, and the formidable obstacle of therapy resistance.

Ginsenoside Rk1 induces autophagy-dependent apoptosis in hepatocellular carcinoma by AMPK/mTOR signaling pathway

Hepatocellular carcinoma (HCC) is the third most lethal cancer in the world. Recent studies have shown that suppression of autophagy plays an important role in the development of HCC. Ginsenoside Rk1 is a protopanaxadiol saponin isolated from ginseng and has a significant anti-tumor effect, but its role and mechanism in HCC are still unclear. In this study, a mouse liver cancer model induced by diethylnitrosamine and carbon tetrachloride (DEN + CCl4) was employed to investigate the inhibitory effect of Rk1 on HCC. The results demonstrate that ginsenoside Rk1 effectively inhibits liver injury, liver fibrosis, and cirrhosis during HCC progression. Transcriptome data analysis of mouse liver tissue reveals that ginsenoside Rk1 significantly regulates the AMPK/mTOR signaling pathway, autophagy pathway, and apoptosis pathway. Subsequent studies show that ginsenoside Rk1 induces AMPK protein activation, upregulates the expression of autophagy marker LC3-II protein to promote autophagy, and then downregulates the expression of Bcl2 protein to trigger a caspase cascade reaction, activating AMPK/mTOR-induced toxic autophagy to promote cells death. Importantly, co-treatment of ginsenoside Rk1 with autophagy inhibitors can inhibit apoptosis of HCC cells, once again demonstrating the ability of ginsenoside Rk1 to promote autophagy-dependent apoptosis. In conclusion, our study demonstrates that ginsenoside Rk1 inhibits the development of primary HCC by activating toxic autophagy to promote apoptosis through the AMPK/mTOR pathway. These findings confirm that ginsenoside Rk1 is a promising new strategy for the treatment of HCC.

Nanoparticle-enhanced postbiotics: Revolutionizing cancer therapy through effective delivery

AIM

Gastric cancer contributes to cancer-related fatalities. Conventional chemotherapy faces challenges due to severe adverse effects, prompting recent research to focus on postbiotics, which are safer biomolecules derived from nonviable probiotics. Despite promising in vitro results, efficient in vivo delivery systems remain a challenge. This study aimed to design a potential nanoparticle (NP) formulation encapsulating the Lacticaseibacillus paracasei GMNL-133 (SGMNL-133) isolate to enhance its therapeutic efficacy in treating gastric cancer.

MAIN METHODS

We successfully isolated GMNL-133 (SGMNL-133) by optimizing the lysate extraction and column elution processes for L. paracasei GMNL-133, resulting in substantial enhancement of its capacity to inhibit the proliferation of gastric cancer cells. Additionally, we developed a potential NP utilizing arginine-chitosan and fucoidan encapsulating SGMNL-133.

KEY FINDINGS

This innovative approach protected the SGMNL-133 from degradation by gastric acid, facilitated its penetration through the mucus layer, and enabled interaction with gastric cancer cells. Furthermore, in vivo experiments demonstrated that the encapsulation of SGMNL-133 in NPs significantly enhanced its efficacy in the treatment of orthotopic gastric tumors while simultaneously reducing tissue inflammation levels.

SIGNIFICANCE

Recent research highlights postbiotics as a safe alternative, but in vivo delivery remains a challenge. Our study optimized the extraction of the lysate and column elution of GMNL-133, yielding SGMNL-133. We also developed NPs to protect SGMNL-133 from gastric acid, enhance mucus penetration, and improve the interaction with gastric cancer cells. This combination significantly enhanced drug delivery and anti-gastric tumor activity.