Clinical and functional spectrum of RAC2-related immunodeficiency

Taraxacum mongolicum Hand.-Mazz. extract disrupts the interaction between triple-negative breast cancer cells and tumor-associated macrophages by inhibiting RAC2/NF-κB p65/p38 MAPK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Taraxacum mongolicum Hand.-Mazz., generally known as dandelion, is a herb renowned for its pharmacological properties, including detoxifying and anti-inflammatory effects. Historically, this herb has been extensively utilized in the treatment of breast diseases. Recent studies have demonstrated that dandelion exhibits inhibitory properties against triple-negative breast cancer (TNBC) and modulates the tumor-associated macrophages (TAMs) microenvironment. However, the primary pharmacological mechanisms remain to be completely revealed.

AIM OF THE STUDY

This study is focused on examining the mechanism by which dandelion extract regulates the communication between TNBC and TAMs through an integrative approach of network-based pharmacology and experimental verification.

MATERIALS AND METHODS

A three-dimensional (3D) co-culture cell model was employed to visualize the impact of dandelion extract on the crosstalk between TAMs and TNBC. To shed light on the crucial mechanisms of dandelion inhibitory effects on TNBC, a network pharmacology analysis was undertaken. Transwell assays were utilized to assess cell capabilities to migrate and infiltrate. Small interfering RNA (siRNA) and an overexpression plasmid targeting Ras-related C3 botulinum toxin substrate 2 (RAC2) were applied to knock down or upregulate the expression levels of RAC2. The altered expression levels of associated molecules were evaluated using quantitative real-time PCR, Western blotting, and immunohistochemistry.

RESULTS

The results from 3D co-culture model demonstrated that dandelion extract significantly hindered the consolidating strength between TNBC cells and TAMs. The extract effectively suppressed TAM-induced epithelial-mesenchymal transition (EMT) in TNBC cells and inhibited the recruitment of TAMs and M2 polarization mediated by TNBC cells. Network pharmacology analysis predicted that dandelion extract attenuates the inflammatory response in TNBC through NF-κB p65/p38 MAPK. Notably, dandelion extract reduced the levels of NF-κB p65/p38 MAPK-related cytokines, including TNF-α, IL-1β, and IL-6 in TNBC cells, while increasing them in TAMs. Overexpression of RAC2 in TNBC cells not only augmented their proliferation, migration, invasion, and EMT processes but also facilitated increased recruitment and M2 polarization of TAMs. TAMs were observed to promote lung metastasis, whereas dandelion extract significantly inhibited lung metastasis and EMT in 231 xenografts. Mechanically, dandelion extract significantly mitigated the RAC2/NF-κB p65/p38 MAPK-mediated inflammatory response both in TNBC cells and 231 xenografts, thereby disrupting the crosstalk between TNBC cells and TAMs.

CONCLUSION

Dandelion extract inhibits the crosstalk between TNBC and TAMs through RAC2/NF-κB p65/p38 MAPK inflammatory pathway, thereby suppressing lung metastasis in TNBC. This study revealed dandelion extract exerts a bidirectional regulatory effect on inflammation in modulating the interaction between TNBC and TAMs, offering a promising therapeutic insight for TNBC treatment.

The Role of RAC2 and PTTG1 in Cancer Biology

Several molecular pathways are likely involved in the regulation of cancer stem cells (CSCs) via Ras-associated C3 botulinum toxin substrate 2, RAC2, and pituitary tumor-transforming gene 1 product, PTTG1, given their roles in cellular signaling, survival, proliferation, and metastasis. RAC2 is a member of the Rho GTPase family and plays a crucial role in actin cytoskeleton dynamics, reactive oxygen species production, and cell migration, contributing to epithelial-mesenchymal transition (EMT), immune evasion, and therapy resistance. PTTG1, also known as human securin, regulates key processes such as cell cycle progression, apoptosis suppression, and EMT, promoting metastasis and enhancing cancer cell survival. This article aims to describe the molecular pathways involved in the proliferation, invasiveness, and drug response of cancer cells through RAC2 and PTTG1, aiming to clarify their respective roles in neoplastic process dependencies. Both proteins are involved in critical signaling pathways, including PI3K/AKT, TGF-β, and NF-κB, which facilitate tumor progression by modulating CSC properties, angiogenesis, and immune response. This review highlights the molecular mechanisms by which RAC2 and PTTG1 influence tumorigenesis and describes their potential and efficacy as prognostic biomarkers and therapeutic targets in managing various neoplasms.

RAC2 gain-of-function variants causing inborn error of immunity drive NLRP3 inflammasome activation

A growing number of patients presenting severe combined immunodeficiencies attributed to monoallelic RAC2 variants have been identified. The expression of the RHO GTPase RAC2 is restricted to the hematopoietic lineage. RAC2 variants have been described to cause immunodeficiencies associated with high frequency of infection, leukopenia, and autoinflammatory features. Here, we show that specific RAC2 activating mutations induce the NLRP3 inflammasome activation leading to the secretion of IL-1β and IL-18 from macrophages. This activation depends on the activation state of the RAC2 variant and is mediated by the downstream kinase PAK1. Inhibiting the RAC2-PAK1-NLRP3 inflammasome pathway might be considered as a potential treatment for these patients.

Key Disease-Related Genes and Immune Cell Infiltration Landscape in Inflammatory Bowel Disease: A Bioinformatics Investigation

Inflammatory Bowel Diseases (IBD), which encompass ulcerative colitis (UC) and Crohn's disease (CD), are characterized by chronic inflammation and tissue damage of the gastrointestinal tract. This study aimed to uncover novel disease-gene signatures, dysregulated pathways, and the immune cell infiltration landscape of inflamed tissues. Eight publicly available transcriptomic datasets, including inflamed and non-inflamed tissues from CD and UC patients were analyzed. Common differentially expressed genes (DEGs) were identified through meta-analysis, revealing 180 DEGs. DEGs were implicated in leukocyte transendothelial migration, PI3K-Akt, chemokine, NOD-like receptors, TNF signaling pathways, and pathways in cancer. Protein-protein interaction network and cluster analysis identified 14 central IBD players, which were validated using eight external datasets. Disease module construction using the NeDRex platform identified nine out of 14 disease-associated genes (CYBB, RAC2, GNAI2, ITGA4, CYBA, NCF4, CPT1A, NCF2, and PCK1). Immune infiltration profile assessment revealed a significantly higher degree of infiltration of neutrophils, activated dendritic cells, plasma cells, mast cells (resting/activated), B cells (memory/naïve), regulatory T cells, and M0 and M1 macrophages in inflamed IBD tissue. Collectively, this study identified the immune infiltration profile and nine disease-associated genes as potential modulators of IBD pathogenesis, offering insights into disease molecular mechanisms, and highlighting potential disease modulators and immune cell dynamics.

Unveiling the Uncommon: A Unique Case of ALPS-like Syndrome Complicated by Plasma Cell Disorder

Multiple myeloma is a rare disease in pediatrics, where about 30 cases are described under 15 years old. It is even rarer when atypical multiple myeloma occurs in the context of autoimmunity. This case describes a 9-year-old female with autoimmune lymphoproliferative-like disease and combined immune deficiency that developed acute kidney failure with monoclonal peak associated with RAC2 and TNFRSF9 variants. An adapted protocol from the backbone adult multiple myeloma standard of care with the addition of an allogeneic hematopoietic stem cell transplant was used. The patient, now nearly a year posttransplant, shows 100% chimerism with no sign of relapse.

Inborn errors of immunity with susceptibility to S. aureus infections

Staphylococcus aureus (S. aureus) is a significant human pathogen, in particular in patients with an underlying medical condition. It is equipped with a large variety of virulence factors enabling both colonization and invasive disease. The spectrum of manifestation is broad, ranging from superficial skin infections to life-threatening conditions like pneumonia and sepsis. As a major cause of healthcare-associated infections, there is a great need in understanding staphylococcal immunity and defense mechanisms. Patients with inborn errors of immunity (IEI) frequently present with pathological infection susceptibility, however, not all of them are prone to S. aureus infection. Thus, enhanced frequency or severity of S. aureus infections can serve as a clinical indicator of a specific underlying immunological impairment. In addition, the analysis of immunological functions in patients with susceptibility to S. aureus provides a unique opportunity of understanding the complex interplay between staphylococcal virulence and host immune predisposition. While the importance of quantitatively and qualitatively normal neutrophils is widely known, less awareness exists about the role of specific cytokines such as functional interleukin (IL)-6 signaling. This review categorizes well-known IEI in light of their susceptibility to S. aureus and discusses the relevant associated pathomechanisms. Understanding host-pathogen-interactions in S. aureus infections in susceptible individuals can pave the way for more effective management and preventive treatment options. Moreover, these insights might help to identify patients who should be screened for an underlying IEI. Ultimately, enhanced understanding of pathogenesis and immune responses in S. aureus infections may also be of relevance for the general population.

Case Report: Profound newborn leukopenia related to a novel RAC2 variant

We report the case of a 1-week-old male born full-term, who had two inconclusive severe combined immunodeficiency (SCID) newborn screens and developed scalp cellulitis and Escherichia coli bacteremia. He did not pass early confirmatory hearing screens. Initial blood counts and lymphocyte flow cytometry revealed profound neutropenia and lymphopenia with a T-/B-/NK- phenotype. Red blood cell adenosine deaminase 1 activity was within normal limits. A presumptive diagnosis of reticular dysgenesis was considered. Granulocyte colony-stimulating factor was started, but there was no improvement in neutrophil counts. Subsequent lymphocyte flow cytometry at around 4 weeks of age demonstrated an increase in T-, B- and NK-cell numbers, eliminating suspicion for SCID and raising concern for congenital neutropenia and bone marrow failure syndromes. Genetic testing revealed a novel variant in RAC2 [c.181C>A (p.Gln61Lys)] (Q61K). RAC2, a Ras-related GTPase, is the dominant RAC protein expressed in hematopoietic cells and is involved with various downstream immune-mediated responses. Pathogenic RAC2 variants show significant phenotypic heterogeneity (spanning from neutrophil defects to combined immunodeficiency) across dominant, constitutively activating, dominant activating, dominant negative, and autosomal recessive subtypes. Given the identification of a novel variant, functional testing was pursued to evaluate aberrant pathways described in other RAC2 pathogenic variants. In comparison to wild-type RAC2, the Q61K variant supported elevated superoxide production under both basal and PMA-stimulated conditions, increased PAK1 binding, and enhanced plasma membrane ruffling, consistent with other dominant, constitutively active mutations. This case highlights the diagnostic challenge associated with genetic variants identified via next-generation sequencing panels and the importance of functional assays to confirm variant pathogenicity.