Real-World Safety of Niraparib for Maintenance Treatment of Ovarian Cancer in Canada.

Niraparib was recently funded in Canada for the maintenance treatment of ovarian cancer following platinum-based chemotherapy. However, the drug's safety profile in the real world remains uncertain. We conducted a cohort study to describe the patient population using niraparib and the proportion that experienced adverse events between June 2019 and December 2022 in four Canadian provinces (Ontario, Alberta, British Columbia [BC], and Quebec). We used administrative data and electronic medical records from Ontario Health, Alberta Health Services, and BC Cancer, and registry data from Exactis Innovation. We summarized baseline characteristics using descriptive statistics and reported safety outcomes using cumulative incidence. We identified 514 patients receiving niraparib. Mean age was 67 years and most were initiated on a daily dose of 100 or 200 mg/day. Grade 3/4 anemia, neutropenia, and thrombocytopenia occurred in 11-16% of the cohort. In Ontario, the three-month cumulative incidence of grade 3/4 thrombocytopenia was 11.6% (95% CI, 8.3-15.4%), neutropenia was 7.1% (95% CI, 4.6-10.4%), and anemia was 11.3% (95% CI, 8.0-15.2%). Cumulative incidences in the remaining provinces were similar. Initial daily dose and proportions of hematological adverse events were low in the real world and may be related to cautious prescribing and close monitoring by clinicians.

Serum resistance, gallium nitrate tolerance and extrapulmonary dissemination are linked to heme consumption in a bacteremic strain of Acinetobacter baumannii.

Bacteremia caused by Acinetobacter baumannii is a highly lethal complication of hospital-acquired pneumonia. In the present study, we investigated the serum resistance, gallium nitrate tolerance and heme consumption of A. baumannii strain LAC-4 which was recently reported to display high virulence in a mouse pneumonia model with extrapulmonary dissemination leading to fatal bacteremia. This strain showed enhanced growth in mouse and fetal bovine serum that was independent of complement and was not observed with regular growth media. The LAC-4 strain was found to possess a high tolerance to gallium nitrate (GaN), whereas serum synergized with GaN in inhibiting A. baumannii strain ATCC 17978. We found that LAC-4 contains a heme oxygenase gene and expresses a highly efficient heme consumption system. This system can be fully blocked in vitro and in vivo by gallium protoporphyrin IX (GaPPIX). Inhibition of heme consumption by GaPPIX completely abrogated the growth advantage of LAC-4 in serum as well as its tolerance to GaN. More importantly, GaPPIX treatment of mice intranasally infected with LAC-4 prevented extrapulmonary dissemination and death. Thus, we propose that heme provides an additional source of iron for LAC-4 to bypass iron restriction caused by serum transferrin, lactoferrin or free gallium salts. Heme consumption systems in A. baumannii may constitute major virulence factors for lethal bacteremic isolates.

PARK2 mediates interleukin 6 and monocyte chemoattractant protein 1 production by human macrophages.

Leprosy is a persistent infectious disease caused by Mycobacterium leprae that still affects over 200,000 new patients annually. The host genetic background is an important risk factor for leprosy susceptibility and the PARK2 gene is a replicated leprosy susceptibility candidate gene. The protein product of PARK2, Parkin, is an E3 ubiquitin ligase that is involved in the development of various forms of Parkinsonism. The human macrophage is both a natural host cell of M. leprae as well as a primary mediator of natural immune defenses, in part by secreting important pro-inflammatory cytokines and chemokines. Here, we report that down-regulation of Parkin in THP-1 macrophages, human monocyte-derived macrophages and human Schwann cells resulted in a consistent and specific decrease in interleukin-6 (IL-6) and monocyte chemoattractant protein 1 (MCP-1/CCL2) production in response to mycobacteria or LPS. Interestingly, production of IL-6 at 6 hours by THP-1 cells stimulated with live M. leprae and M. bovis BCG was dependent on pretreatment with 1,25-dihydroxyvitamin D(3) (VD). Parkin knockdown in VD-treated cells blocked IL-6 induction by mycobacteria. However, IκB-α phosphorylation and levels of IκB-ξ, a nuclear protein required for IL-6 expression, were not affected by Parkin silencing. Phosphorylation of MAPK ERK1/2 and p38 was unaffected by Parkin silencing while JNK activation was promoted but did not explain the altered cytokine production. In a final set of experiments we found that genetic risk factors of leprosy located in the PARK2 promoter region were significantly correlated with M. leprae sonicate triggered CCL2 and IL6 transcript levels in whole blood assays. These results associated genetically controlled changes in the production of MCP-1/CCL2 and IL-6 with known leprosy susceptibility factors.

In vitro and in vivo biological activities of iron chelators and gallium nitrate against Acinetobacter baumannii.

We investigated the ability of compounds interfering with iron metabolism to inhibit the growth of Acinetobacter baumannii. Iron restriction with transferrin or 2,2-bipyridyl significantly inhibited A. baumannii growth in vitro. Gallium nitrate alone was moderately effective at reducing A. baumannii growth but became bacteriostatic in the presence of serum or transferrin. More importantly, gallium nitrate treatment reduced lung bacterial burdens in mice. The use of gallium-based therapies shows promise for the control of multidrug-resistant A. baumannii.

Genetic and functional analysis of common MRC1 exon 7 polymorphisms in leprosy susceptibility.

The chromosomal region 10p13 has been linked to paucibacillary leprosy in two independent studies. The MRC1 gene, encoding the human mannose receptor (MR), is located in the 10p13 region and non-synonymous SNPs in exon 7 of the gene have been suggested as leprosy susceptibility factors. We determined that G396S is the only non-synonymous exon 7-encoded polymorphism in 396 unrelated Vietnamese subjects. This SNP was genotyped in 490 simplex and 90 multiplex leprosy families comprising 704 patients (47% paucibacillary; 53% multibacillary). We observed significant under-transmission of the serine allele of the G396S polymorphism with leprosy per se (P = 0.036) and multibacillary leprosy (P = 0.034). In a sample of 384 Brazilian leprosy cases (51% paucibacillary; 49% multibacillary) and 399 healthy controls, we observed significant association of the glycine allele of the G396S polymorphism with leprosy per se (P = 0.016) and multibacillary leprosy (P = 0.023). In addition, we observed a significant association of exon 7 encoded amino acid haplotypes with leprosy per se (P = 0.012) and multibacillary leprosy (P = 0.004). Next, we tested HEK293 cells over-expressing MR constructs (293-MR) with three exon 7 haplotypes of MRC1 for their ability to bind and internalize ovalbumin and zymosan, two classical MR ligands. No difference in uptake was measured between the variants. In addition, 293-MR failed to bind and internalize viable Mycobacterium leprae and BCG. We propose that the MR-M. leprae interaction is modulated by an accessory host molecule of unknown identity.

Increased NOD2-mediated recognition of N-glycolyl muramyl dipeptide.

Peptidoglycan-derived muramyl dipeptide (MDP) activates innate immunity via the host sensor NOD2. Although MDP is N-acetylated in most bacteria, mycobacteria and related Actinomycetes convert their MDP to an N-glycolylated form through the action of N-acetyl muramic acid hydroxylase (NamH). We used a combination of bacterial genetics and synthetic chemistry to investigate whether N-glycolylation of MDP alters NOD2-mediated immunity. Upon infecting macrophages with 12 bacteria, tumor necrosis factor (TNF) alpha secretion was NOD2 dependent only with mycobacteria and other Actinomycetes (Nocardia and Rhodococcus). Disruption of namH in Mycobacterium smegmatis obrogated NOD2-mediated TNF secretion, which could be restored upon gene complementation. In mouse macrophages, N-glycolyl MDP was more potent than N-acetyl MDP at activating RIP2, nuclear factor kappaB, c-Jun N-terminal kinase, and proinflammatory cytokine secretion. In mice challenged intraperitoneally with live or killed mycobacteria, NOD2-dependent immune responses depended on the presence of bacterial namH. Finally, N-glycolyl MDP was more efficacious than N-acetyl MDP at inducing ovalbumin-specific T cell immunity in a model of adjuvancy. Our findings indicate that N-glycolyl MDP has a greater NOD2-stimulating activity than N-acetyl MDP, consistent with the historical observation attributing exceptional immunogenic activity to the mycobacterial cell wall.

Genetic predisposition to leprosy: A major gene reveals novel pathways of immunity to Mycobacterium leprae.

The elucidation of the genetic control of susceptibility to common infectious diseases is expected to provide new and more effective tools for prevention and control of some of the most pressings health needs on a global scale. A major advantage of whole genome based genetic approaches is that no a priori assumptions about mechanisms of pathogenesis need to be made in these studies. Hence, genetic studies can identify previously unrecognized pathways of disease susceptibility and tag critical pathogenic events for further biochemical, immunological or physiological analysis. We have applied this strategy to leprosy, a disease that still claims 400,000 new cases each year. We identified genetic variants in the shared promoter region of the PARK2 and PACRG genes as major risk factors of leprosy susceptibility. Both encoded proteins are part of the cellular ubiquitination system. Specifically, PARK2, the cause of early onset Parkinson's disease, is an E3 ligase that likely is involved in controlled proteolysis, the cellular anti-oxidants response and the regulation of innate immune responsiveness. In addition, numerous E3 ligases have recently been shown to be critical regulators of immunity. While the specific role of PARK2/PACRG in leprosy pathogenesis remains unknown, a number of experimentally testable scenarios can be developed to further explore the role of these proteins in anti-Mycobacterium leprae host responsiveness.

Nur77 forms novel nuclear structures upon DNA damage that cause transcriptional arrest.

The orphan nuclear receptor Nur77 has been implicated in both growth and apoptosis, and its function and activity can be modulated by cellular redistribution. Green fluorescent protein-tagged Nur77 was used to evaluate the role of Nur77 intracellular redistribution in response to genotoxic stress. Selected DNA damaging agents and transcription inhibition lead to rapid redistribution of Nur77 into nuclear structures distinct from conventional nuclear bodies. These nuclear bodies formed transiently were tightly bound to the nuclear matrix and conditions that lead to their appearance were associated with Nur77 transcriptional inhibition. The formation of Nur77 nuclear bodies might be involved in programmed cell death modulation upon exposure to DNA damaging agents that inhibit transcription by sequestrating this proapoptotic factor in dense nuclear structures.