LP-184, a Novel Acylfulvene Molecule, Exhibits Anticancer Activity against Diverse Solid Tumors with Homologous Recombination Deficiency

Homologous recombination (HR)-related gene alterations are present in a significant subset of prostate, breast, ovarian, pancreatic, lung, and colon cancers rendering these tumors as potential responders to specific DNA damaging agents. A small molecule acylfulvene prodrug, LP-184, metabolizes to an active compound by the oxidoreductase activity of enzyme prostaglandin reductase 1 (PTGR1), which is frequently elevated in multiple solid tumor types. Prior work demonstrated that cancer cell lines deficient in a spectrum of DNA damage repair (DDR) pathway genes show increased susceptibility to LP-184. Here, we investigated the potential of LP-184 in targeting multiple tumors with impaired HR function and its mechanism of action as a DNA damaging agent. LP-184 induced elevated DNA double-strand breaks in HR deficient (HRD) cancer cells. Depletion of key HR components BRCA2 or ataxia telangiectasia mutated (ATM) in cancer cells conferred up to 12-fold increased sensitivity to the LP-184. LP-184 showed nanomolar potency in a diverse range of HRD cancer models, including prostate cancer organoids, leiomyosarcoma cell lines, and patient-derived tumor graft models of lung, pancreatic, and prostate cancers. LP-184 demonstrated complete, durable tumor regression in 10 patient-derived xenograft (PDX) models of HRD triple-negative breast cancer (TNBC) including those resistant to PARP inhibitors (PARPi). LP-184 further displayed strong synergy with PARPi in ovarian and prostate cancer cell lines as well as in TNBC PDX models. These preclinical findings illustrate the potential of LP-184 as a pan-HRD cancer therapeutic. Taken together, our results support continued clinical evaluation of LP-184 in a large subset of HRD solid tumors.

SIGNIFICANCE

New agents with activity against DDR-deficient solid tumors refractory to standard-of-care therapies are needed. We report multiple findings supporting the potential for LP-184, a novel alkylating agent with three FDA orphan drug designations, to fill this void clinically: strong nanomolar potency; sustained, durable regression of solid tumor xenografts; synthetic lethality with HR defects. LP-184 adult phase IA trial to assess safety in advanced solid tumors is ongoing.

Porphyromonas gingivalis Peptidyl Arginine Deiminase (PPAD) in the Context of the Feed-Forward Loop of Inflammation in Periodontitis

Periodontitis is a widespread chronic inflammatory disease caused by a changed dysbiotic oral microbiome. Although multiple species and risk factors are associated with periodontitis, Porphyromonas gingivalis has been identified as a keystone pathogen. The immune-modulatory function of P. gingivalis is well characterized, but the mechanism by which this bacterium secretes peptidyl arginine deiminase (PPAD), a protein/peptide citrullinating enzyme, thus contributing to the infinite feed-forward loop of inflammation, is not fully understood. To determine the functional role of citrullination in periodontitis, neutrophils were stimulated by P. gingivalis bearing wild-type PPAD and by a PPAD mutant strain lacking an active enzyme. Flow cytometry showed that PPAD contributed to prolonged neutrophil survival upon bacterial stimulation, accompanied by the secretion of aberrant IL-6 and TNF-α. To further assess the complex mechanism by which citrullination sustains a chronic inflammatory state, the ROS production and phagocytic activity of neutrophils were evaluated. Flow cytometry and colony formation assays showed that PPAD obstructs the resolution of inflammation by promoting neutrophil survival and the release of pro-inflammatory cytokines, while enhancing the resilience of the bacteria to phagocytosis.

Abstract 6108: Novel functional dSTRIDE-HR assays to report on the status of homologous recombination repair in cancer cells

Since the early days of the synthetic lethality concept in DNA Damage Response the status of homologous recombination (HR) repair in cancer cells have been the focus of attention of researchers and clinicians. While different approaches exist, such as the RAD51 immunofluorescence (IF) or HRD genomic assays, functional biomarkers that can assess HR proficiency are missing. We report here the development, optimization and validation of two complementary, HR-specific functional assays. The assays, which are based on the STRIDE platform technology, detect double-strand DNA breaks localized in close proximity to RPA or RAD51 proteins. The optimization phase of assay development was performed in U2OS cells. First, repeatability (intra-run variation) and reproducibility (inter-run variation) of the assays were measured in untreated cells. Then, a series of technical negative controls was performed which have shown that the number of false-positive readouts is below 10% of the total number of signals. Finally, treatment of cells with compounds known to induce double-strand DNA breaks (etoposide and cisplatin) resulted in statistically significant increase in the number of detected dSTRIDE-RAD51 and dSTRIDE-RPA foci when compared to untreated controls. The assays were further validated in NCI-H661 (BRCA2 wild-type) and NCI-H169 (BRCA2 KO) cell line pair. The cells were treated with two concentrations of etoposide and the readouts from dSTRIDE, detecting the total pool of DSBs and dSTRIDE-HR assays were compared. In NCI-H661 cells, treatment with etoposide resulted in an increase in the number of double-strand breaks detected by dSTRIDE and as expected, more DSBs were formed after treatment with the higher concentration. dSTRIDE-HR assays confirmed that approximately 15% and 10% of these DSBs contain RPA and RAD51 proteins, respectively. In NCI-H169 cells etoposide produced a stronger reaction with even more DSBs detected by dSTRIDE, but importantly, no increase in the number of dSTRIDE-RAD51 foci was observed. dSTRIDE-RPA foci increased after treatment hinting that this step of HR remains unperturbed. Interestingly, the number of dSTRIDE-RAD51 foci in untreated cells was comparable between the two cell lines. In conclusion, we show here that two newly developed dSTRIDE-HR assays are well validated and can be successfully applied to report on the status of homologous recombination repair in different cell models.

Citation Format: Kamil Solarczyk, Agnieszka Waligórska, Karolina Uznańska, Zsombor Prucsi, Olga Wójcikowska, Ewelina Matuszyk, Magdalena Bartyńska, Agata Kitlińska, Aleksandra Bober, Franek Sierpowski, Maja Białecka, Monika Jarosz, Malgorzata Szczygiel, Szymon Koman, Karolina Korpanty, Lukasz Beben, Lukasz Bandzarewicz, Przemyslaw Stachura, Magdalena Kordon-Kiszala. Novel functional dSTRIDE-HR assays to report on the status of homologous recombination repair in cancer cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6108.

Uncovering the Oral Dysbiotic Microbiota as Masters of Neutrophil Responses in the Pathobiology of Periodontitis

Numerous bacterial species participate in the shift of the oral microbiome from beneficial to dysbiotic. The biggest challenge lying ahead of microbiologists, immunologists and dentists is the fact that the bacterial species act differently, although usually synergistically, on the host immune cells, including neutrophils, and on the surrounding tissues, making the investigation of single factors challenging. As biofilm is a complex community, the members interact with each other, which can be a key issue in future studies designed to develop effective treatments. To understand how a patient gets to the stage of the late-onset (previously termed chronic) periodontitis or develops other, in some cases life-threatening, diseases, it is crucial to identify the microbial composition of the biofilm and the mechanisms behind its pathogenicity. The members of the red complex (Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia) have long been associated as the cause of periodontitis and stayed in the focus of research. However, novel techniques, such as 16S clonal analysis, demonstrated that the oral microbiome diversity is greater than ever expected and it opened a new era in periodontal research. This review aims to summarize the current knowledge concerning bacterial participation beyond P. gingivalis and the red complex in periodontal inflammation mediated by neutrophils and to spread awareness about the associated diseases and pathological conditions.

Size-dependent activity of silver nanoparticles on the morphological switch and biofilm formation of opportunistic pathogenic yeasts

Background

Dimorphism and biofilm formation are important virulence factors of some opportunistic human pathogenic yeasts. Such species commensally colonize skin or mucosal surfaces generally in yeast form, but under particular circumstances, convert into virulent hyphae and disseminate internal organs or cause mucocutaneous infections. The yeast-to-hypha shape-conversion promotes the development of a biofilm, a thick extracellular matrix with sessile cells within. The biofilm is capable to prevent the penetration of antifungal drugs, rendering the surviving biofilm-resident cells intrinsic sources of recurrent infections. The aim of this study was to evaluate the ability of silver nanoparticles (AgNPs) to attenuate the morphological switch and biofilm formation of several opportunistic pathogenic yeasts and to determine whether this feature depends on the nanoparticle size.

Results

AgNPs in three different sizes were prepared by chemical reduction approach and characterized by transmission electron microscopy, ultraviolet–visible spectroscopy and dynamic light scattering. The antifungal activity was evaluated by the microdilution method, the inhibitory capacity on biofilm formation and the biofilm degradation ability of differently sized AgNPs was assessed by viability assay. The morphological state of opportunistic pathogenic yeast cells in monoculture and in co-culture with human keratinocytes in the presence of AgNPs was examined by flow cytometry and scanning electron microscopy. All the three AgNPs inhibited the growth of the examined opportunistic pathogenic yeasts, nevertheless, AgNPs with the smallest diameter exhibited the most prominent toxic activities. AgNPs attenuated the biofilm formation in a nanoparticle size-dependent manner; however, their biofilm destruction capacity was negligible. AgNPs with the smallest size exerted the most significant effect on suppressing the morphological change of pathogens in monoculture as well as in a co-culture with keratinocytes.

Conclusions

Our results confirm that AgNPs are capable to hinder yeast-to-hypha morphological conversion and biofilm formation of opportunistic pathogens and this biological effect of AgNPs is size-dependent.