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Background: Small cell lung cancer (SCLC) is the most aggressive neuroendocrine lung cancer, with a dismal 5‐year survival rate. No reliable biomarkers or imaging are available for early SCLC detection. In a search for a specific marker of SCLC, this study identified that hepatocyte cell adhesion molecule 2 (HEPACAM2), a member of the immunoglobulin‐like superfamily, is highly and specifically expressed in SCLC. Methods: This study investigated HEPACAM2 expression in patients with SCLC via RNA sequencing and evaluated its relationship to progression‐free survival (PFS) and overall survival (OS). Immunofluorescence microscopy was used to assess the cellular location of HEPACAM2 and to conduct in vitro and in vivo studies to understand its expression and functional significance. These findings were integrated with databases of patients with SCLC. Results: HEPACAM2 is highly expressed and specific to SCLC. HEPACAM2 levels are inversely correlated with PFS and OS in patients with SCLC and are expressed at all stages. Moreover, HEPACAM2 messenger RNA and its peptides can be detected in the secretomes in cell lines. Positively correlated with ASCL1 expression in SCLC tumors, HEPACAM2 is localized primarily to the plasma membrane and linked to extracellular matrix signaling and cellular migration. A loss of HEPACAM2 in SCLC cells attenuated ASCL1 and MYC expression. Consistent with clinical data, in vitro and in vivo studies suggested that HEPACAM2 promotes cancer cell growth. Conclusions: With its remarkable specificity, high expression, presence in early disease, and extracellular secretion, HEPACAM2 could be a potential diagnostic cell surface biomarker for early SCLC detection. These findings warrant further investigation into its role in the pathobiology of SCLC. Hepatocyte cell adhesion molecule 2 (HEPACAM2) shows great promise as a diagnostic biomarker for small cell lung cancer (SCLC) due to its high specificity, strong expression in SCLC tissues, and extracellular secretion, which make it an ideal candidate for early detection. As a cell surface protein, HEPACAM2 offers the potential for minimally invasive diagnostic approaches to improve SCLC screening and early intervention strategies. [ABSTRACT FROM AUTHOR]

Antibody-drug conjugate (ADC) therapy has transformed treatment for several solid tumors, including small cell lung cancer (SCLC). However, significant challenges remain, including systemic toxicity, acquired resistance, and the lack of reliable biomarkers for patient selection. To enhance the effectiveness of ADC therapies in SCLC, we focused on target selection in this study by investigating the expression of ADC targets - SEZ6, DLL3, CD276, and TACSTD2 - in cell lines and patient samples. SEZ6 expression was significantly elevated in various SCLC transcriptional subtypes, particularly ASCL1, and exhibited gender-specific differences, being lower in women. DLL3 was primarily observed in the ASCL1 subtype, while CD276 showed high expression in non-neuroendocrine subtypes. TACSTD2 levels were generally low and attenuated in lymph nodes and brain metastases compared to primary tumors. Our findings underscore the importance of understanding target expression patterns to optimize ADC therapy and advance precision medicine in SCLC treatment. [ABSTRACT FROM AUTHOR]

Crohn's disease (CD) has been traditionally viewed as a chronic inflammatory disease that cause gut wall thickening and complications, including fistulas, by mechanisms not understood. By focusing on Parabacteroides distasonis (presumed modern succinate-producing commensal probiotic), recovered from intestinal microfistulous tracts (cavernous fistulous micropathologies CavFT proposed as intermediate between 'mucosal fissures' and 'fistulas') in two patients that required surgery to remove CD-damaged ilea, we demonstrate that such isolates exert pathogenic/pathobiont roles in mouse models of CD. Our isolates are clonally-related; potentially emerging as transmissible in the community and mice; proinflammatory and adapted to the ileum of germ-free mice prone to CD-like ileitis (SAMP1/YitFc) but not healthy mice (C57BL/6J), and cytotoxic/ATP-depleting to HoxB8-immortalized bone marrow derived myeloid cells from SAMP1/YitFc mice when concurrently exposed to succinate and extracts from CavFT-derived E. coli , but not to cells from healthy mice. With unique genomic features supporting recent genetic exchange with Bacteroides fragilis -BGF539, evidence of international presence in primarily human metagenome databases, these CavFT Pdis isolates could represent to a new opportunistic Parabacteroides species, or subspecies (' cavitamuralis' ) adapted to microfistulous niches in CD.

Comensal Bacteroidota ( Bacteroidota ) and Enterobacteriacea are often linked to gut inflammation. However, the causes for variability of pro-inflammatory surface antigens that affect gut commensal/opportunistic dualism in Bacteroidota remain unclear. By using the classical lipopolysaccharide/O-antigen ' rfb operon' in Enterobacteriaceae as a surface antigen model (5- rfb- gene-cluster rfbABCDX ), and a recent rfbA- typing strategy for strain classification, we characterized the integrity and conservancy of the entire rfb operon in Bacteroidota . Through exploratory analysis of complete genomes and metagenomes, we discovered that most Bacteroidota have the rfb operon fragmented into nonrandom patterns of gene-singlets and doublets/triplets, termed ' rfb- gene-clusters', or rfb-'minioperons' if predicted as transcriptional. To reflect global operon integrity, contiguity, duplication, and fragmentation principles, we propose a six-category (infra/supra-numerary) cataloging system and a Global Operon Profiling System for bacteria. Mechanistically, genomic sequence analyses revealed that operon fragmentation is driven by intra-operon insertions of predominantly Bacteroides -DNA ( thetaiotaomicron/fragilis ) and likely natural selection in gut-wall specific micro-niches or micropathologies. Bacteroides -insertions, also detected in other antigenic operons (fimbriae), but not in operons deemed essential (ribosomal), could explain why Bacteroidota have fewer KEGG-pathways despite large genomes. DNA insertions, overrepresenting DNA-exchange-avid ( Bacteroides ) species, impact our interpretation of functional metagenomics data by inflating by inflating gene-based pathway inference and by overestimating 'extra-species' abundance. Of disease relevance, Bacteroidota species isolated from cavitating/cavernous fistulous tract (CavFT) microlesions in Crohn's Disease have supra-numerary fragmented operons, stimulate TNF-alpha from macrophages with low potency, and do not induce hyperacute peritonitis in mice compared to CavFT Enterobacteriaceae . The impact of 'foreign-DNA' insertions on pro-inflammatory operons, metagenomics, and commensalism/opportunism requires further studies to elucidate their potential for novel diagnostics and therapeutics, and to elucidate the role of co-existing pathobionts in Crohn's disease microlesions.

The causes for variability of pro-inflammatory surface antigens that affect gut commensal/opportunistic dualism within the phylum Bacteroidota remain unclear (1, 2). Using the classical lipopolysaccharide/O-antigen ' rfb operon' in Enterobacteriaceae as a surface antigen model (5-gene-cluster rfbABCDX ), and a recent rfbA- typing strategy for strain classification (3), we characterized the architecture/conservancy of the entire rfb operon in Bacteroidota . Analyzing complete genomes, we discovered that most Bacteroidota have the rfb operon fragmented into non-random gene-singlets and/or doublets/triplets, termed 'minioperons'. To reflect global operon integrity, duplication, and fragmentation principles, we propose a five-category (infra/supernumerary) cataloguing system and a Global Operon Profiling System for bacteria. Mechanistically, genomic sequence analyses revealed that operon fragmentation is driven by intra-operon insertions of predominantly Bacteroides -DNA ( thetaiotaomicron/fragilis ) and likely natural selection in specific micro-niches. Bacteroides -insertions, also detected in other antigenic operons (fimbriae), but not in operons deemed essential (ribosomal), could explain why Bacteroidota have fewer KEGG-pathways despite large genomes (4). DNA insertions overrepresenting DNA-exchange-avid species, impact functional metagenomics by inflating gene-based pathway inference and overestimating 'extra-species' abundance. Using bacteria from inflammatory gut-wall cavernous micro-tracts (CavFT) in Crohn's Disease (5), we illustrate that bacteria with supernumerary-fragmented operons cannot produce O-antigen, and that commensal/CavFT Bacteroidota stimulate macrophages with lower potency than Enterobacteriaceae , and do not induce peritonitis in mice. The impact of 'foreign-DNA' insertions on pro-inflammatory operons, metagenomics, and commensalism offers potential for novel diagnostics and therapeutics., Competing Interests: Conflict of Interest: The authors declare they have no conflicts of interest.