RSPO2 as Wnt signaling enabler: Important roles in cancer development and therapeutic opportunities

Screening, expression, and functional validation of camelid-derived nanobodies targeting RSPO2

OBJECTIVE

RSPO2 (R-spondin 2) is a key regulator of the Wnt/β-catenin signaling pathway, involved in embryogenesis, tissue homeostasis, and cancer progression. Despite its therapeutic potential, effective agents targeting RSPO2 remain elusive. To address the unmet need for RSPO2-targeted therapies, we aimed to develop high-affinity nanobodies via phage display and prokaryotic expression, characterizing their binding specificity and functional blockade of RSPO2-LGR4 interactions. This study provides foundational insights into nanobody-mediated inhibition of Wnt signaling, supporting future therapeutic strategies against RSPO2-driven pathologies.

METHODS

Recombinant RSPO2 proteins were constructed and purified using PCR-based recombination. Camels (Camelus bactrianus) were immunized with RSPO2, and phage display was employed to screen nanobody libraries. High-affinity nanobodies were cloned, expressed, purified, and assessed for specificity and binding affinity using biolayer interferometry and protein blotting. Functional validation was performed using TOPFLASH assays to evaluate their impact on Wnt/β-catenin signaling.

RESULTS

Nanobodies with high specificity and nanomolar-range affinity constants (KDs) for RSPO2 were identified. The nanobody effectively inhibited RSPO2-induced Wnt/β-catenin signaling in human renal epithelial cells.

CONCLUSION

The development of RSPO2-targeting nanobodies offers new prospects for treating RSPO2-related diseases. The nanobody serve as valuable tools for functional research and hold potential as diagnostic and therapeutic agents for RSPO2-driven conditions.

Anaplastic lymphoma kinase enhances Wnt signaling through R-spondin: A new dimension to ALK-mediated oncogenesis

Anaplastic lymphoma kinase receptor (ALK) is a receptor tyrosine kinase that plays a key role in the progression of several cancers and is activated by ligands such as ALKAL1 and ALKAL2. To identify additional molecules that interact with ALK, we constructed comprehensive genetic and molecular level networks. Notably, our study identified R-spondins, growth factors known to enhance Wnt signaling, as novel interacting partners of ALK. Protein-protein docking studies revealed that R-spondins bind to the TNF-like and EGF-like domains of ALK, which are critical for the interaction of ALK with its known ligand ALKAL2. These docking outcomes were further validated by molecular dynamics simulations, and approximate binding affinity calculations that confirmed the stability and conformational behavior of the ALK and R-spondin complex. These in silico findings indicate a strong interaction between ALK and R-spondins. To investigate whether this interaction influences Wnt signaling in vitro, we conducted a Wnt signaling reporter assay (TOP Flash/FOP Flash) in neuroblastoma cells by introducing Rspo2, Wnt3a, and crizotinib, an ALK inhibitor. The results showed a decrease in the TOP/FOP ratio when ALK was inhibited. Collectively, our study reveals a novel role for ALK in enhancing Wnt signaling via R-spondins, providing new dimension into ALK-mediated oncogenesis.

Management strategies for primary lung carcinosarcoma: a case study and comprehensive literature review

BACKGROUND

Primary lung carcinosarcoma, characterized by the presence of both carcinoma and sarcoma components, is a rare soft tissue malignancy. Its pathogenesis remains incompletely elucidated, and it exhibits significant resistance to conventional therapeutic interventions, resulting in a dismal prognosis. Consequently, there is currently no established standard treatment protocol for lung carcinosarcoma, leading most clinicians to draw upon their experiences with other tumor types when formulating treatment strategies.

CASE DESCRIPTION

A 56-year-old non-smoking male presented with a progressively enlarging mass in the right cervical region, The diagnosis of lung carcinosarcoma was definitively confirmed through CT-guided biopsy. First-line immunotherapy combined with targeted therapy was ineffective; second-line chemotherapy was effective, chest CT revealed the disappearance of enlarged lymph nodes in the retrosternal area and a significant reduction of pulmonary lesions, but showed signs of brain metastasis. the patient passed away at home on June 27th, 2023 due to sudden onset dyspnea accompanied by loss of consciousness.

LITERATURE REVIEW

A comprehensive literature search for lung carcinosarcoma was conducted across four databases, including PubMed/MEDLINE, Web of Science, Cochrane Library, and Embase, covering the period from 1968 to 2023. A total of 48 patients were included for analysis. Further survival analysis revealed a median survival time of 18 months; adjuvant therapy following surgery significantly improved survival compared to surgery alone and other treatment modalities.

CONCLUSION

Lung carcinosarcoma is an exceptionally rare malignant neoplasm of the lung, and definitive treatment protocols remain elusive. The most effective strategy to enhance prognosis may still entail complete surgical resection of the lesions in conjunction with adjuvant therapy.

The RSPO2 gene is associated with bilateral anterior amelia in Chihuahuas

Bilateral anterior amelia (BAA) is the congenital absence of thoracic limbs and has been reported in the Chihuahua as an autosomal recessive disorder. In some cases, the digits of the pelvic limbs can be variably affected, but otherwise, the pelvic limbs are generally spared. A GWAS performed with nine BAA affected Chihuahuas identified a significant association on chromosome 13, and homozygosity mapping delineated a 2.1 Mb chromosomal region containing the RSPO2 gene. Loss of function variants of RSPO2 in humans and cattle has been associated with the absence of all limbs. Six affected Chihuahuas were whole genome sequenced (WGS) and aligned to the CanFam4 assembly. SNVs, small indels, and structural variants within the critical interval that fitted a recessive model were investigated. Three SNVs (NC_049234.1:g.8891861C > T; NC_049234.1:g.8974204C > T and NC_049234.1:g.9789424G > A) were homozygous in five cases and absent from 3,418 genetically diverse control genome sequences, except for one Small Poodle that was heterozygous. One SNV resided in RSPO2's second intron, while the two others were intergenic. The three candidate variants were genotyped in 7 additional cases and 100 control Chihuahuas. Twelve of 13 cases were homozygous for the mutant allele, and one case was heterozygous. Controls were either homozygous for the reference allele (97%) or heterozygous (3%). Our data should facilitate genetic testing of Chihuahuas to prevent the unintentional production of BAA affected dogs. Moreover, the identification of these variants enhances understanding of RSPO2 gene function in limb development.

Characterizing macrophage diversity in colorectal malignancies through single-cell genomics

Colorectal cancer (CRC) is one of the most common malignant tumors of the digestive tract, with increasing incidence and mortality rates, posing a significant burden on human health. Its progression relies on various mechanisms, among which the tumor microenvironment and tumor-associated macrophages (TAMs) have garnered increasing attention. Macrophage infiltration in various solid tumors is associated with poor prognosis and is linked to chemotherapy resistance in many cancers. These significant biological behaviors depend on the heterogeneity of macrophages. Tumor-promoting TAMs comprise subpopulations characterized by distinct markers and unique transcriptional profiles, rendering them potential targets for anticancer therapies through either depletion or reprogramming from a pro-tumoral to an anti-tumoral state. Single-cell RNA sequencing technology has significantly enhanced our research resolution, breaking the traditional simplistic definitions of macrophage subtypes and deepening our understanding of the diversity within TAMs. However, a unified elucidation of the nomenclature and molecular characteristics associated with this diversity remains lacking. In this review, we assess the application of conventional macrophage polarization subtypes in colorectal malignancies and explore several unique subtypes defined from a single-cell omics perspective in recent years, categorizing them based on their potential functions.

LGR4 (GPR48): The Emerging Inter-Bridge in Osteoimmunology

Leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4), a member of the G-protein-coupled receptor (GPCR) family, has been implicated in various regulatory functions across multiple differentiation stages and numerous target sites in bone diseases. Therefore, LGR4 is a potential regulator of nuclear factor-κB ligand (RANKL) during osteoclast differentiation. However, a comprehensive investigation of its functions and applications in bone immunology is lacking. This review discusses the molecular characteristics, signaling pathways, and role of LGR4 in osteoimmunology, with a particular focus on its interactions with RANKL during osteoclast differentiation, while identifying gaps that warrant further research.

Wnt Pathway-Targeted Therapy in Gastrointestinal Cancers: Integrating Benchside Insights with Bedside Applications

The Wnt signaling pathway is critical in the onset and progression of gastrointestinal (GI) cancers. Anomalies in this pathway, often stemming from mutations in critical components such as adenomatous polyposis coli (APC) or β-catenin, lead to uncontrolled cell proliferation and survival. In the case of colorectal cancer, dysregulation of the Wnt pathway drives tumor initiation and growth. Similarly, aberrant Wnt signaling contributes to tumor development, metastasis, and resistance to therapy in other GI cancers, such as gastric, pancreatic, and hepatocellular carcinomas. Targeting the Wnt pathway or its downstream effectors has emerged as a promising therapeutic strategy for combating these highly aggressive GI malignancies. Here, we review the dysregulation of the Wnt signaling pathway in the pathogenesis of GI cancers and further explore the therapeutic potential of targeting the various components of the Wnt pathway. Furthermore, we summarize and integrate the preclinical evidence supporting the therapeutic efficacy of potent Wnt pathway inhibitors with completed and ongoing clinical trials in GI cancers. Additionally, we discuss the challenges of Wnt pathway-targeted therapies in GI cancers to overcome these concerns for effective clinical translation.

Cushing's Disease Manifestation in USP8-Mutated Corticotropinoma May Be Mediated by Interactions Between WNT Signaling and SST Trafficking

In the current work, we aimed to evaluate the association of clinical data of Cushing's disease (CD) patients with USP8 mutation status and to study USP8-related molecular mechanisms connected to the regulation of corticotropinoma growth and activity. 35 CD patients were enrolled; the sequencing of exon 14 in USP8 revealed variants in eighteen adenomas, two of which were described for the first time in CD. USP8 variants were more common in women (94% vs. 76%; p = 0.001), and microadenomas and tumor recurrence were prevalent in the USP8-mutant group (44% vs. 29%; p = 0.04 and 44% vs. 22%; p = 0.0015). Preoperative ACTH and serum cortisol did not differ in the USP8-WT and USP8-mutant patients. All USP8-mutant adenomas were SST5-positive, and 73% of them were double-positive (SST5+/SST2+). A total of 50% of USP8-WT adenomas were double-negative (SST5-/SST2-), and 40% of them were SST5-positive. Analysis of transcriptome was performed for nine USP8-mutant and six USP8-WT adenomas and revealed the that the bidirectional dysregulation of Wnt signaling, including both the agonist RSPO2 and antagonist SFRP1, in the USP8-mutant corticotropinomas was downregulated. These alterations may indicate the existence of regulatory connections between USP8 enzyme activity, Wnt signaling, EGFR signaling and somatostatin receptors' trafficking, which can explain, at least in part, the clinical manifestations of CD in patients with corticotropinomas harboring USP8 variants.

An "R-spondin code" for multimodal signaling ON-OFF states

R-spondins (RSPOs) are a family of secreted proteins and stem cell growth factors that are potent co-activators of Wnt signaling. Recently, RSPO2 and RSPO3 were shown to be multifunctional, not only amplifying Wnt- but also binding BMP- and FGF receptors to downregulate signaling. The common mechanism underlying these diverse functions is that RSPO2 and RSPO3 act as "endocytosers" that link transmembrane proteins to ZNRF3/RNF43 E3 ligases and trigger target internalization. Thus, RSPOs are natural protein targeting chimeras for cell surface proteins. Conducting data mining and cell surface binding assays we report additional candidate RSPO targets, including SMO, PTC1,2, LGI1, ROBO4, and PTPR(F/S). We propose that there is an "R-spondin code" that imparts combinatorial signaling ON-OFF states of multiple growth factors. This code involves the modular RSPO domains, notably distinct motifs in the divergent RSPO-TSP1 domains to mediate target interaction and internalization. The RSPO code offers a novel framework for the understanding how diverse signaling pathways may be coordinately regulated in development and disease.

The intestinal stem cell as a target: A review

Human intestinal epithelium handles several events that may affect health. It is composed of villi and crypts, which contain different types of cells. Each cell type plays an essential role in intestinal functions, including absorption, defense, self-renewal, and regeneration. Intestinal stem cells (ISCs), located at the base of intestinal crypts, play an important role in intestinal homeostasis and renewal. Any disruption in intestinal homeostasis, in which ISCs alter their function, may result in tumor growth. As Wnt and Notch signaling pathways are essential for ISCs homeostasis and for maintaining self-renewal, any defects in these pathways could increase the risk of developing colorectal cancer (CRC). Lgr5+ cells have been identified as intestinal stem cells expressing a leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), which is involved in the regulation of Wnt signaling. Several studies have reported upregulated expression of LGR5 in CRC. Hence, in this review, we discuss the relationship between LGR5, Wnt signaling, and Notch signaling and the development of CRC, as well as recent therapeutic strategies targeting LGR5, cancer stem cells (CSCs), and the aforementioned signaling pathways.

Wnt/β-catenin signaling pathway in carcinogenesis and cancer therapy

The Wnt/β-catenin signaling pathway plays a crucial role in various physiological processes, encompassing development, tissue homeostasis, and cell proliferation. Under normal physiological conditions, the Wnt/β-catenin signaling pathway is meticulously regulated. However, aberrant activation of this pathway and downstream target genes can occur due to mutations in key components of the Wnt/β-catenin pathway, epigenetic modifications, and crosstalk with other signaling pathways. Consequently, these dysregulations contribute significantly to tumor initiation and progression. Therapies targeting the Wnt/β-catenin signaling transduction have exhibited promising prospects and potential for tumor treatment. An increasing number of medications targeting this pathway are continuously being developed and validated. This comprehensive review aims to summarize the latest advances in our understanding of the role played by the Wnt/β-catenin signaling pathway in carcinogenesis and targeted therapy, providing valuable insights into acknowledging current opportunities and challenges associated with targeting this signaling pathway in cancer research and treatment.

Navigating through novelties concerning mCRC treatment-the role of immunotherapy, chemotherapy, and targeted therapy in mCRC

Over the course of nearly six decades since the inception of initial trials involving 5-FU in the treatment of mCRC (metastatic colorectal cancer), our progressive comprehension of the pathophysiology, genetics, and surgical techniques related to mCRC has paved the way for the introduction of novel therapeutic modalities. These advancements not only have augmented the overall survival but have also positively impacted the quality of life (QoL) for affected individuals. Despite the remarkable progress made in the last two decades in the development of chemotherapy, immunotherapy, and target therapies, mCRC remains an incurable disease, with a 5-year survival rate of 14%. In this comprehensive review, our primary goal is to present an overview of mCRC treatment methods following the latest guidelines provided by the National Comprehensive Cancer Network (NCCN), the American Society of Clinical Oncology (ASCO), and the American Society of Colon and Rectal Surgeons (ASCRS). Emphasis has been placed on outlining treatment approaches encompassing chemotherapy, immunotherapy, targeted therapy, and surgery's role in managing mCRC. Furthermore, our review delves into prospective avenues for developing new therapies, offering a glimpse into the future of alternative pathways that hold potential for advancing the field.

NestedBD: Bayesian inference of phylogenetic trees from single-cell copy number profiles under a birth-death model

Copy number aberrations (CNAs) are ubiquitous in many types of cancer. Inferring CNAs from cancer genomic data could help shed light on the initiation, progression, and potential treatment of cancer. While such data have traditionally been available via "bulk sequencing," the more recently introduced techniques for single-cell DNA sequencing (scDNAseq) provide the type of data that makes CNA inference possible at the single-cell resolution. We introduce a new birth-death evolutionary model of CNAs and a Bayesian method, NestedBD, for the inference of evolutionary trees (topologies and branch lengths with relative mutation rates) from single-cell data. We evaluated NestedBD's performance using simulated data sets, benchmarking its accuracy against traditional phylogenetic tools as well as state-of-the-art methods. The results show that NestedBD infers more accurate topologies and branch lengths, and that the birth-death model can improve the accuracy of copy number estimation. And when applied to biological data sets, NestedBD infers plausible evolutionary histories of two colorectal cancer samples. NestedBD is available at https://github.com/Androstane/NestedBD .

Multiomics data identifies RSPO2 as a prognostic biomarker in human tumors associated with pan-cancer

RSPO2 protein may provide valuable insights into the mechanism underlying various types of tumorigenesis. The role of RSPO2 in pan-cancer has not been reported so far. Therefore, this study aimed to provide a comprehensive analysis of RSPO2 from a pan-cancer perspective employing multiomics data. The expression profile and function of RSPO2 across different tumors were investigated using various web-based tools UALCAN, GEPIA, TIMER, Human Protein Atlas, cBioPortal, TISIDB, STRING, and Metascape to interpret the expression profile, promoter methylation status, genomic alterations, survival analysis, protein-protein interaction, correlation with immune cell subtypes, tumor immune microenvironment and enrichment analysis. Comprehensive pan-cancer analysis indicated that RSPO2 was significantly downregulated in eleven and upregulated in five tumor types compared to normal tissues, validation results further suggest RSPO2 was downregulated in most of the tumors. The protein level expression of RSPO2 was mostly low in malignant tissues. We found that RSPO2 was significantly related to individual pathological stages in BLCA, COAD, LUAD and LUSC. Prognostic analysis indicates that the high RSPO2 expression was significantly correlated with the poor prognosis in BRCA, KICH, KIRP, READ, and UCES. Furthermore, RSPO2 is frequently amplified, exhibits hypermethylated promoter in most cancers, and is associated with immune subtypes, molecular subtypes and immune cell infiltration. Finally, enrichment analysis showed that RSPO2 is involved in the regulation of the canonical Wnt pathway and neuronal development. The overall comprehensive pan-cancer analysis affirms that RSPO2 could be a promising diagnostic and prognostic biomarker and latent therapy target in the future.

R-spondin-1 induces Axin degradation via the LRP6-CK1ε axis

R-spondins (RSPOs) are secreted signaling molecules that potentiate the Wnt/β-catenin pathway by cooperating with Wnt ligands. RSPO1 is crucial in tissue development and tissue homeostasis. However, the molecular mechanism by which RSPOs activate Wnt/β-catenin signaling remains elusive. In this study, we found that RSPOs could mediate the degradation of Axin through the ubiquitin-proteasome pathway. The results of Co-IP showed that the recombinant RSPO1 protein promoted the interaction between Axin1 and CK1ε. Either knockout of the CK1ε gene or treatment with the CK1δ/CK1ε inhibitor SR3029 caused an increase in Axin1 protein levels and attenuated RSPO1-induced degradation of the Axin1 protein. Moreover, we observed an increase in the number of associations of LRP6 with CK1ε and Axin1 following RSPO1 stimulation. Overexpression of LRP6 further potentiated Axin1 degradation mediated by RSPO1 or CK1ε. In addition, recombinant RSPO1 and Wnt3A proteins synergistically downregulated the protein expression of Axin1 and enhanced the transcriptional activity of the SuperTOPFlash reporter. Taken together, these results uncover the novel mechanism by which RSPOs activate Wnt/β-catenin signaling through LRP6/CK1ε-mediated degradation of Axin.