Combined PARP inhibitors and small molecular inhibitors in solid tumor treatment (Review)

Application of PARP inhibitors combined with immune checkpoint inhibitors in ovarian cancer

The advent of polyadenosine diphosphate ribose polymerase inhibitors (PARPi) has brought about significant changes in the field of ovarian cancer treatment. However, in 2022, Rucaparib, Olaparib, and Niraparib, had their marketing approval revoked for third-line and subsequent therapies due to an increased potential for adverse events. Consequently, the exploration of new treatment modalities remains imperative. Recently, the integration of PARPi with immune checkpoint inhibitors (ICIs) has emerged as a potential remedy option within the context of ovarian cancer. This article offers a comprehensive examination of the mechanisms and applications of PARPi and ICIs in the treatment of ovarian cancer. It synthesizes the existing evidence supporting their combined use and discusses key considerations that merit attention in ongoing development efforts.

Oncogenic STAT Transcription Factors as Targets for Cancer Therapy: Innovative Strategies and Clinical Translation

Despite advances in our understanding of molecular aspects of oncogenesis, cancer remains a leading cause of death. The malignant behavior of a cancer cell is driven by the inappropriate activation of transcription factors. In particular, signal transducers and activators of transcription (STATs), which regulate many critical cellular processes such as proliferation, apoptosis, and differentiation, are frequently activated inappropriately in a wide spectrum of human cancers. Multiple signaling pathways converge on the STATs, highlighting their importance in the development and progression of oncogenic diseases. STAT3 and STAT5 are two members of the STAT protein family that are the most frequently activated in cancers and can drive cancer pathogenesis directly. The development of inhibitors targeting STAT3 and STAT5 has been the subject of intense investigations in the last decade, although effective treatment options remain limited. In this review, we investigate the specific roles of STAT3 and STAT5 in normal physiology and cancer biology, discuss the opportunities and challenges in pharmacologically targeting STAT proteins and their upstream activators, and offer insights into novel therapeutic strategies to identify STAT inhibitors as cancer therapeutics.

Exceptional synergistic response of PARP inhibitor and immune checkpoint inhibitor in esophageal adenocarcinoma with a germline BRCA2 mutation: a case report

Immune checkpoint inhibitors (ICIs) and poly (ADP-ribose) polymerase (PARP) inhibitors have shown efficacy in various tumors. A significant therapeutic challenge with either ICIs or PARP inhibitors as monotherapy is treatment failure from intrinsic primary resistance or the development of secondarily acquired resistance after a period of responsiveness. The combination of PARP inhibitors and ICIs could mitigate this by potentiating treatment response. We describe an 83-year-old male patient who initially presented with abdominal pain, and weight loss along with alternating constipation and diarrhea. Imaging and biopsy revealed metastatic esophageal adenocarcinoma. Genomic testing revealed germline BRCA2 mutation. The patient initially underwent a few cycles of chemoimmunotherapy. However, due to intolerance to chemotherapy, the patient's case was discussed at a multidisciplinary molecular tumor board. He was switched to PARP inhibitor olaparib and ICI nivolumab. This combination led to a durable complete response. A combination of poly-ADP ribose polymerase inhibitor (PARPi) plus ICI may work in synergy through various mechanisms including enhanced neoantigen expression, release of immune-activating cytokines, and increased programmed death-ligand 1 expression. This may culminate in accentuated efficacy outcomes with a manageable safety profile. This exceptional response with ICI and PARPi in our case is consistent with the synergistic value of this combination, and prospective studies are warranted to definitively characterize clinical utility.

Bibliometric analysis of research trends on the combination of immune checkpoint inhibitors and PARP inhibitors in solid tumors

Introduction

Immune checkpoint inhibitors (ICIs) has made significant achievements in the therapeutics of various tumor types, and recently growing evidence from preclinical studies and clinical trials has indicated that poly-ADP-ribose polymerase inhibitors (PARPi) are exhibiting encouraging synergism with ICIs. The aim of our current study is to explore the development pattern of literature related to the combined therapy of ICIs and PARPi in solid tumors from a bibliometric perspective.

Methods

Publications concerning the combination of ICIs and PARPi in solid tumors during 2008-2022 were extracted from the WOSCC database. VOSviewer and R-bibliometrix were applied to conduct bibliometrics.

Results

In total, 1113 articles were finally included. The USA was the most dominant country, and University of Texas MD Anderson Cancer Center was the most fruitful institute. Andreas Schneeweiss ranked first concerning the amount of publications in this research domain, and Timothy Yap had the most citations on this theme. The analysis of keyword co-occurrence indicated that research frontiers were shifted from the biological mechanisms of cell death to the combined strategy of ICIs and PARPi in clinical trials.

Conclusions

Our study comprehensively examined the publications on the combination of ICIs and PARPi in solid tumors from a bibliometric perspective. The research on this topic is in its rapid growth stage, and the USA is possessing an absolutely leading position in this field by its scientific accumulations and productivity. Moreover, the research frontiers have shifted from the mechanisms of ICIs and PARPi to their combined treatment in clinical application. In summary, our results demonstrated a comprehensive overview of the knowledge atlas and a valuable reference for the future investigations in this field.

Histone and DNA Methylation as Epigenetic Regulators of DNA Damage Repair in Gastric Cancer and Emerging Therapeutic Opportunities

Gastric cancer (GC), one of the most common malignancies worldwide, is a heterogeneous disease developing from the accumulation of genetic and epigenetic changes. One of the most critical epigenetic alterations in GC is DNA and histone methylation, which affects multiple processes in the cell nucleus, including gene expression and DNA damage repair (DDR). Indeed, the aberrant expression of histone methyltransferases and demethylases influences chromatin accessibility to the DNA repair machinery; moreover, overexpression of DNA methyltransferases results in promoter hypermethylation, which can suppress the transcription of genes involved in DNA repair. Several DDR mechanisms have been recognized so far, with homologous recombination (HR) being the main pathway involved in the repair of double-strand breaks. An increasing number of defective HR genes are emerging in GC, resulting in the identification of important determinants of therapeutic response to DDR inhibitors. This review describes how both histone and DNA methylation affect DDR in the context of GC and discusses how alterations in DDR can help identify new molecular targets to devise more effective therapeutic strategies for GC, with a particular focus on HR-deficient tumors.

The dynamic process of covalent and non-covalent PARylation in the maintenance of genome integrity: a focus on PARP inhibitors

Poly(ADP-ribosylation) (PARylation) by poly(ADP-ribose) polymerases (PARPs) is a highly regulated process that consists of the covalent addition of polymers of ADP-ribose (PAR) through post-translational modifications of substrate proteins or non-covalent interactions with PAR via PAR binding domains and motifs, thereby reprogramming their functions. This modification is particularly known for its central role in the maintenance of genomic stability. However, how genomic integrity is controlled by an intricate interplay of covalent PARylation and non-covalent PAR binding remains largely unknown. Of importance, PARylation has caught recent attention for providing a mechanistic basis of synthetic lethality involving PARP inhibitors (PARPi), most notably in homologous recombination (HR)-deficient breast and ovarian tumors. The molecular mechanisms responsible for the anti-cancer effect of PARPi are thought to implicate both catalytic inhibition and trapping of PARP enzymes on DNA. However, the relative contribution of each on tumor-specific cytotoxicity is still unclear. It is paramount to understand these PAR-dependent mechanisms, given that resistance to PARPi is a challenge in the clinic. Deciphering the complex interplay between covalent PARylation and non-covalent PAR binding and defining how PARP trapping and non-trapping events contribute to PARPi anti-tumour activity is essential for developing improved therapeutic strategies. With this perspective, we review the current understanding of PARylation biology in the context of the DNA damage response (DDR) and the mechanisms underlying PARPi activity and resistance.