Genomic characterization of co-existing neoplasia and carcinoma lesions reveals distinct evolutionary paths of gallbladder cancer

Genomic landscape of gallbladder cancer: insights from whole exome sequencing

BACKGROUND

Gallbladder cancer (GBC) is a common gastrointestinal malignancy noted for its aggressive characteristics and poor prognosis, which is mostly caused by delayed detection. However, the scarcity of information regarding somatic mutations in Indian patients with GBC has hampered the development of efficient therapeutic options. In the present study, the authors attempted to bridge this gap by revealing the mutational profile of GBC.

MATERIALS AND METHODS

To evaluate the somatic mutation profile, whole exome sequencing (WES) was performed on 66 tumor and matched blood samples from individuals with GBC. Somatic variant calling was performed using GATK pipeline. Variants were annotated at pathogenic and oncogenic levels, using ANNOVAR, VEP tools and the OncoKB database. Mutational signature analysis, oncogenic pathway analysis and cancer driver genes identification were performed at the functional level by using the maftools package.

RESULTS

Our findings focused on the eight most altered genes with pathogenic and oncogenic mutations: TP53, SMAD4, ERBB3, KRAS, ARID1A, PIK3CA, RB1, and AXIN1. Genes with pathogenic single nucleotide variations (SNVs) were enriched in oncogenic signaling pathways, particularly RTK-RAS, WNT, and TP53 pathways. Furthermore, our research related certain mutational signatures, such as cosmic 1, cosmic 6, and cosmic 18, 29, to known characteristics including patient age and tobacco smoking, providing important insights into disease etiology.

CONCLUSIONS

Given the scarcity of exome-based sequencing studies focusing on the Indian population, this study represents a significant step forward in providing a framework for additional in-depth mutational analysis. Genes with substantial oncogenic and pathogenic mutations are promising candidates for developing targeted mutation panels, particularly for GBC detection.

Clinical and Genomic Characterization of ERBB2-Altered Gallbladder Cancer: Exploring Differences Between an American and a Chilean Cohort

PURPOSE

Gallbladder cancer (GBC) is a biliary tract malignancy characterized by its high lethality. Although the incidence of GBC is low in most countries, specific areas such as Chile display a high incidence. Our collaborative study sought to compare clinical and molecular features of GBC cohorts from Chile and the United States with a focus on ERBB2 alterations.

METHODS

Patients were accrued at Memorial Sloan Kettering Cancer Center (MSK) or the Pontificia Universidad Católica de Chile (PUC). Clinical information was retrieved from medical records. Genomic analysis was performed by the next-generation sequencing platform MSK-Integrated Mutation Profiling of Actionable Cancer Targets.

RESULTS

A total of 260 patients with GBC were included, 237 from MSK and 23 from PUC. There were no significant differences in the clinical characteristics between the patients identified at MSK and at PUC except in terms of lithiasis prevalence which was significantly higher in the PUC cohort (85% v 44%; P = .0003). The prevalence of ERBB2 alterations was comparable between the two cohorts (15% v 9%; P = .42). Overall, ERBB2 alterations were present in 14% of patients (8% with ERBB2 amplification, 4% ERBB2 mutation, 1.5% concurrent amplification and mutation, and 0.4% ERBB2 fusion). Notably, patients with GBC that harbored ERBB2 alterations had better overall survival (OS) versus their ERBB2-wild type counterparts (22.3 months v 11.8 months; P = .024).

CONCLUSION

The prevalence of lithiasis seems to be higher in Chilean versus US patients with GBC. A similar prevalence of ERBB2 alterations of overall 14% and better OS suggests that a proportion of them could benefit from human epidermal growth factor receptor type 2-targeted therapies. The smaller cohort of Chile, where the disease prevalence is higher, is a reminder and invitation for the need of more robust next-generation sequencing analyses globally.

Morphomolecular Pathology and Genomic Insights into the Cells of Origin of Cholangiocarcinoma and Combined Hepatocellular-Cholangiocarcinoma

Cholangiocarcinomas are a highly heterogeneous group of malignancies that, despite recent progress in the understanding of their molecular pathogenesis and clinical management, continue to pose a major challenge to public health. The traditional view posits that cholangiocarcinomas derive from the neoplastic transformation of cholangiocytes lining the biliary tree. However, increasing genetic and experimental evidence has recently pointed to a more complex, and nuanced, scenario for the potential cell of origin of cholangiocarcinomas. Hepatocytes as well as hepatic stem/progenitor cells are being considered as additional potential sources, depending on microenvironmental contexts, including liver injury. The hypothesis of potentially diverse cells of origin for cholangiocarcinoma, albeit controversial, is certainly not surprising given the plasticity of the cells populating the liver as well as the existence of liver cancer subtypes with mixed histologic and molecular features. This review carefully examines the current pathologic, genomic, and experimental evidence supporting the existence of multiple cells of origin of liver and biliary tract cancers, with particular focus on cholangiocarcinoma and combined hepatocellular-cholangiocarcinoma.

Spatial transcriptomics profiling of gallbladder adenocarcinoma: a detailed two-case study of progression from precursor lesions to cancer

BACKGROUND

Most studies on tumour progression from precursor lesion toward gallbladder adenocarcinoma investigate lesions sampled from distinct patients, providing an overarching view of pathogenic cascades. Whether this reflects the tumourigenic process in individual patients remains insufficiently explored. Genomic and epigenomic studies suggest that a subset of gallbladder cancers originate from biliary intraepithelial neoplasia (BilIN) precursor lesions, whereas others form independently from BilINs. Spatial transcriptomic data supporting these conclusions are missing. Moreover, multiple areas with precursor or adenocarcinoma lesions can be detected within the same pathological sample. Yet, knowledge about intra-patient variability of such lesions is lacking.

METHODS

To characterise the spatial transcriptomics of gallbladder cancer tumourigenesis in individual patients, we selected two patients with distinct cancer aetiology and whose samples simultaneously displayed multiple areas of normal epithelium, BilINs and adenocarcinoma. Using GeoMx digital spatial profiling, we characterised the whole transcriptome of a high number of regions of interest (ROIs) per sample in the two patients (24 and 32 ROIs respectively), with each ROI covering approximately 200 cells of normal epithelium, low-grade BilIN, high-grade BilIN or adenocarcinoma. Human gallbladder organoids and cell line-derived tumours were used to investigate the tumour-promoting role of genes.

RESULTS

Spatial transcriptomics revealed that each type of lesion displayed limited intra-patient transcriptomic variability. Our data further suggest that adenocarcinoma derived from high-grade BilIN in one patient and from low-grade BilIN in the other patient, with co-existing high-grade BilIN evolving via a distinct process in the latter case. The two patients displayed distinct sequences of signalling pathway activation during tumour progression, but Semaphorin 4 A (SEMA4A) expression was repressed in both patients. Using human gallbladder-derived organoids and cell line-derived tumours, we provide evidence that repression of SEMA4A promotes pseudostratification of the epithelium and enhances cell migration and survival.

CONCLUSION

Gallbladder adenocarcinoma can develop according to patient-specific processes, and limited intra-patient variability of precursor and cancer lesions was noticed. Our data suggest that repression of SEMA4A can promote tumour progression. They also highlight the need to gain gene expression data in addition to histological information to avoid understimating the risk of low-grade preneoplastic lesions.

Dihydrotanshinone I inhibits gallbladder cancer growth by targeting the Keap1-Nrf2 signaling pathway and Nrf2 phosphorylation

BACKGROUND

Gallbladder cancer (GBC) poses a significant risk to human health. Its development is influenced by numerous factors, particularly the homeostasis of reactive oxygen species (ROS) within cells. This homeostasis is crucial for tumor cell survival, and abnormal regulation of ROS is associated with the occurrence and progression of many cancers. Dihydrotanshinone I (DHT I), a biologically effective ingredient isolated from Salvia miltiorrhiza, has exhibited cytotoxic properties against various tumor cells by inducing apoptosis. However, the precise molecular mechanisms by which dht I exerts its cytotoxic effects remain unclear.

PURPOSE

To explore the anti-tumor impact of dht I on GBC and elucidate the potential molecular mechanisms.

METHODS

The proliferation of GBC cells, NOZ and SGC-996, was assessed using various assays, including CCK-8 assay, colony formation assay and EdU staining. We also examined cell apoptosis, cell cycle progression, ROS levels, and alterations in mitochondrial membrane potential to delve into the intricate molecular mechanism. Quantitative PCR (qPCR), immunofluorescence staining, and Western blotting were performed to evaluate target gene expression at both the mRNA and protein levels. The correlation between nuclear factor erythroid 2-related factor 2 (Nrf2) and kelch-like ECH-associated protein 1 (Keap1) were examined using co-immunoprecipitation. Finally, the in vivo effect of dht I was investigated using a xenograft model of gallbladder cancer in mice.

RESULTS

Our research findings indicated that dht I exerted cytotoxic effects on GBC cells, including inhibiting proliferation, disrupting mitochondrial membrane potential, inducing oxidative stress and apoptosis. Our in vivo studies substantiated the inhibition of dht I on tumor growth in xenograft nude mice. Mechanistically, dht I primarily targeted Nrf2 by promoting Keap1 mediated Nrf2 degradation and inhibiting protein kinase C (PKC) induced Nrf2 phosphorylation. This leads to the suppression of Nrf2 nuclear translocation and reduction of its target gene expression. Moreover, Nrf2 overexpression effectively counteracted the anti-tumor effects of dht I, while Nrf2 knockdown significantly enhanced the inhibitory effect of dht I on GBC. Meanwhile, PKC inhibitors and nuclear import inhibitors increased the sensitivity of GBC cells to dht I treatment. Conversely, Nrf2 activators, proteasome inhibitors, antioxidants and PKC activators all antagonized dht I induced apoptosis and ROS generation in NOZ and SGC-996 cells.

CONCLUSION

Our findings indicated that dht I inhibited the growth of GBC cells by regulating the Keap1-Nrf2 signaling pathway and Nrf2 phosphorylation. These insights provide a strong rationale for further investigation of dht I as a potential therapeutic agent for GBC treatment.

Horizontal duodenal papilla is associated with a special spectrum of pancreaticobiliary diseases: a retrospective magnetic resonance cholangiopancreatography-based study

Background

Horizontal duodenal papilla (HDP) is not an uncommon ectopic major papilla. The impact of HDP on the occurrence of pancreaticobiliary diseases remains unclear. Here, we explored the associations in patients who underwent magnetic resonance cholangiopancreatography (MRCP).

Methods

Consecutive patients who underwent MRCP at Xijing Hospital (Xi'an, China) between January 2020 and December 2021 were eligible. Patients were divided into HDP and regular papilla (RP) according to the position of the major papilla. The primary outcome was the proportion of congenital pancreaticobiliary diseases.

Results

A total of 2,194 patients were included, of whom 72 (3.3%) had HDP. Compared with the RP group (n = 2,122), the HDP group had a higher proportion of congenital pancreaticobiliary diseases, especially choledochal cyst (CC) or anomalous pancreaticobiliary junction (APBJ) (6.9% vs 1.4%, P = 0.001). More gallbladder cancer (6.9% vs 1.2%, P < 0.001) and pancreatic cysts (27.8% vs 16.3%, P = 0.01) were also identified in the HDP group. Morphologically, the HDP group had a longer extrahepatic bile duct (8.4 [7.6-9.3] cm vs 7.2 [6.5-8.1] cm, P < 0.001), and larger angles between the common bile duct-duodenum and pancreatic duct-duodenum. Multivariate analysis showed that the presence of HDP was an independent risk factor for gallbladder cancer.

Conclusions

This study confirmed that HDP was not rare in patients underwent MRCP. A higher prevalence of congenital pancreaticobiliary malformations (especially CC or APBJ), gallbladder cancer and pancreatic cysts was observed in patients with HDP, as well as distinctive morphologic features.

Inhibition of circRNA NGFR promotes ferroptosis in gallbladder carcinoma cells

Background

Gallbladder carcinoma (GBC) is a formidably aggressive malignancy. Circular RNAs (circRNAs) play crucial regulatory roles in cancer. NGFR is a novel circRNA implicated in various types of cancers. The primary goal of this study was to elucidate the role of NGFR in GBC.

Methods

NGFR variants exhibiting discernible discrepancies were identified using RNA sequencing and validated using real-time PCR. Cell proliferation was assessed using 5-ethynyl-2'-deoxyuridine and Cell Counting Kit-8 assays. The ferroptotic phenotype was characterized by assessing the reactive oxygen species and Fe2+ levels. Western blotting was used to analyze ferroptosis-associated proteins. Superoxide dismutase, malondialdehyde, and glutathione levels were measured using commercially available reagent kits. The severity of mitochondrial damage was evaluated by assessing JC-1, MitoSOX, and ATP activities.

Results

NGFR was upregulated, and its suppression inhibited cell proliferation and increased Fe2+ levels in GBC cells. Furthermore, NGFR downregulation disrupted mitochondrial function.

Conclusion

Circular RNA NGFR can impede the advancement of GBC by modulating the ferroptotic phenotype, thereby potentially offering a novel avenue for the clinical diagnosis and treatment strategies of GBC.

Environmental and Metabolic Risk Factors Linked to Gallbladder Dysplasia

Gallbladder disorders encompass a spectrum from congenital anomalies to inflammatory and neoplastic conditions, frequently requiring surgical intervention. Epithelial abnormalities like adenoma and metaplasia have the potential to progress to carcinoma, emphasizing the importance of histopathological assessment for early detection of malignancy. Gallbladder cancer (GBC) may be incidentally discovered during cholecystectomy for presumed benign conditions, underscoring the need for a thorough examination. However, the lack of clarity regarding the molecular mechanisms of GBC has impeded diagnostic and therapeutic advancements. Timely detection is crucial due to GBC's aggressive nature and poor prognosis. Chronic inflammation plays a central role in carcinogenesis, causing DNA damage and oncogenic alterations due to persistent insults. Inflammatory cytokines and microRNAs are among the various mediators contributing to this process. Gallbladder calcifications, particularly stippled ones, may signal malignancy and warrant preemptive removal. Molecular pathways involving mutations in oncogenes and tumor suppressor genes drive GBC pathogenesis, with proposed sequences such as gallstone-induced inflammation leading to carcinoma formation. Understanding these mechanisms, alongside evaluating mucin characteristics and gene mutations, can deepen comprehension of GBC's pathophysiology. This, in turn, facilitates the identification of high-risk individuals and the development of improved treatment strategies, ultimately enhancing patient outcomes. Thus, in this review, our aim has been to underscore the primary mechanisms underlying the development of gallbladder dysplasia and neoplasia.

NGS of brush cytology samples improves the detection of high-grade dysplasia and cholangiocarcinoma in patients with primary sclerosing cholangitis: A retrospective and prospective study

BACKGROUND

Biliary dysplasia, a precursor of cholangiocarcinoma (CCA), is a common complication of primary sclerosing cholangitis. Patients with high-grade dysplasia (HGD) or early CCA who have received oncological treatment are candidates for liver transplantation. The preoperative diagnosis of CCA or HGD is challenging, and the sensitivity of biliary brush cytology (BC) is limited.

METHODS

By using next-generation sequencing (NGS), we retrospectively analyzed archived tissue samples (n=62) obtained from explanted liver tissue and CCA samples to identify oncogenic mutations that occur during primary sclerosing cholangitis carcinogenesis. BC samples were prospectively collected from patients with primary sclerosing cholangitis (n=97) referred for endoscopic retrograde cholangiography to measure the diagnostic utility of NGS combined with BC compared with traditional cytology alone.

RESULTS

Mutations in KRAS, GNAS, FLT3, RNF43, TP53, ATRX, and SMAD4 were detected in archived CCA or HGD samples. KRAS, GNAS, TP53, CDKN2A, FBXW7, BRAF, and ATM mutations were detected in prospectively collected brush samples from patients with histologically verified CCA or HGD. One patient with low-grade dysplasia in the explanted liver had KRAS and GNAS mutations in brush sample. No mutations were observed in brush samples or archived tissues in liver transplantation cases without biliary neoplasia. While KRAS mutations are common in biliary neoplasms, they were also observed in patients without biliary neoplasia during surveillance.

CONCLUSIONS

In summary, NGS of BC samples increased the sensitivity of detecting biliary neoplasia compared with traditional cytology. Performing NGS on BC samples may help diagnose HGD or early CCA, benefiting the timing of liver transplantation.

Diagnostic Utility of Next-Generation Sequencing in Circulating Free DNA and a Comparison With Matched Tissue in Gallbladder Carcinoma

Mutation detection for therapy monitoring in cell-free DNA (cfDNA) is used clinically for some malignancies. Gallbladder carcinoma (GBC) presents a diagnostic challenge and has limited late-stage treatment options. To our knowledge, this novel study examines, for the first time, genomic alterations in cfDNA from GBC to assess diagnostic accuracy and therapeutic options. The concordance of somatic genomic changes in cfDNA and DNA from paired tumor tissue was analyzed. Paired serum and tissue samples from 40 histologically proven GBC, 20 cholecystitis, and 4 normal (noninflamed gallbladder) controls were included. Targeted next-generation sequencing with a 22-gene panel (Colon and Lung Cancer Research Panel v2, Thermo Scientific) in cfDNA and tumor tissue with high depth and uniform coverage on ION Personal Genome Machine (ION, PGM) was performed. A spectrum of 223 mutations in cfDNA and 225 mutations in formalin-fixed paraffin-embedded tissue DNA were identified in 22 genes. Mutations ranged from 1 to 17 per case. In cfDNA frequent alterations were in TP53 (85.0%), EGFR (52.5%), MET (35%) CTNNB1, SMAD4, BRAF (32.5%), PTEN (30%), FGFR3 and PIK3CA (27.5%), NOTCH1 (25.0%), and FBXW7 and ERBB4 (22.5%). At least one clinically actionable mutation was identified in all cfDNA samples. Paired samples shared 149 of 225 genetic abnormalities (66.2%). Individual gene mutation concordance ranged from 44.44% to 82.0% and was highest for EGFR (82.0%), BRAF and NOTCH1 (80.0%), TP53 (73.08%), MET (72.22%), and ERBB4 (71.42%) with a significant level of correlation (Spearman r = 0.91, P ≤ .0001). The sensitivity and specificity of the TP53 gene at the gene level was the highest (94.44% and 100.0%, respectively). Overall survival was higher for ERBB4 and ERBB2 mutant tumors. The adenocarcinoma subtype revealed specific genetic changes in ERBB4, SMAD4, ERBB2, PTEN, KRAS, and NRAS. NGS-based cfDNA mutation profiling can be used to diagnose GBC before surgery to guide treatment decisions. Targeted therapy identified in GBC included SMAD4, ERBB2, ERBB4, EGFR, KRAS, BRAF, PIK3CA, MET, and NRAS.

Biliary Tract Cancer: Molecular Biology of Precursor Lesions

Biliary tract cancer is a devastating malignancy of the bile ducts and gallbladder with a dismal prognosis. The study of precancerous lesions has received considerable attention and led to a histopathological classification which, in some respects, remains an evolving field. Consequently, increasing efforts have been devoted to characterizing the molecular pathogenesis of the precursor lesions, with the aim of better understanding the mechanisms of tumor progression, and with the ultimate goal of meeting the challenges of early diagnosis and treatment. This review delves into the molecular mechanisms that initiate and promote the development of precursor lesions of intra- and extrahepatic cholangiocarcinoma and of gallbladder carcinoma. It addresses the genomic, epigenomic, and transcriptomic landscape of these precursors and provides an overview of animal and organoid models used to study them. In conclusion, this review summarizes the known molecular features of precancerous lesions in biliary tract cancer and highlights our fragmentary knowledge of the molecular pathogenesis of tumor initiation.

Unraveling the Drivers of Tumorigenesis in the Context of Evolution: Theoretical Models and Bioinformatics Tools

Cancer originates from somatic cells that have accumulated mutations. These mutations alter the phenotype of the cells, allowing them to escape homeostatic regulation that maintains normal cell numbers. The emergence of malignancies is an evolutionary process in which the random accumulation of somatic mutations and sequential selection of dominant clones cause cancer cells to proliferate. The development of technologies such as high-throughput sequencing has provided a powerful means to measure subclonal evolutionary dynamics across space and time. Here, we review the patterns that may be observed in cancer evolution and the methods available for quantifying the evolutionary dynamics of cancer. An improved understanding of the evolutionary trajectories of cancer will enable us to explore the molecular mechanism of tumorigenesis and to design tailored treatment strategies.

Comprehensive Molecular Characterization of Gallbladder Carcinoma and Potential Targets for Intervention

PURPOSE

Gallbladder carcinoma (GBC) is an uncommon and aggressive disease, which remains poorly defined at a molecular level. Here, we aimed to characterize the molecular landscape of GBC and identify markers with potential prognostic and therapeutic implications.

EXPERIMENTAL DESIGN

GBC samples were analyzed using the MSK-IMPACT (Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets) platform (targeted NGS assay that analyzes 505 cancer-associated genes). Variants with therapeutic implications were identified using OncoKB database. The associations between recurrent genetic alterations and clinicopathologic characteristics (Fisher exact tests) or overall survival (univariate Cox regression) were evaluated. P values were adjusted for multiple testing.

RESULTS

Overall, 244 samples (57% primary tumors and 43% metastases) from 233 patients were studied (85% adenocarcinomas, 10% carcinomas with squamous differentiation, and 5% neuroendocrine carcinomas). The most common oncogenic molecular alterations appeared in the cell cycle (TP53 63% and CDKN2A 21%) and RTK_RAS pathways (ERBB2 15% and KRAS 11%). No recurrent structural variants were identified. There were no differences in the molecular landscape of primary and metastasis samples. Variants in SMAD4 and STK11 independently associated with reduced survival in patients with metastatic disease. Alterations considered clinically actionable in GBC or other solid tumor types (e.g., NTRK1 fusions or oncogenic variants in ERBB2, PIK3CA, or BRCA1/2) were identified in 35% of patients; 18% of patients with metastatic disease were treated off-label or enrolled in a clinical trial based on molecular findings.

CONCLUSIONS

GBC is a genetically diverse malignancy. This large-scale genomic analysis revealed alterations with potential prognostic and therapeutic implications and provides guidance for the development of targeted therapies.

Concurrent Activation of Kras and Canonical Wnt Signaling Induces Premalignant Lesions That Progress to Extrahepatic Biliary Cancer in Mice

Biliary cancer has long been known to carry a poor prognosis, yet the molecular pathogenesis of carcinoma of the extrahepatic biliary system and its precursor lesions remains elusive. Here we investigated the role of Kras and canonical Wnt pathways in the tumorigenesis of the extrahepatic bile duct (EHBD) and gall bladder (GB). In mice, concurrent activation of Kras and Wnt pathways induced biliary neoplasms that resembled human intracholecystic papillary-tubular neoplasm (ICPN) and biliary intraepithelial neoplasia (BilIN), putative precursors to invasive biliary cancer. At a low frequency, these lesions progressed to adenocarcinoma in a xenograft model, establishing them as precancerous lesions. Global gene expression analysis revealed increased expression of genes associated with c-Myc and TGFβ pathways in mutant biliary spheroids. Silencing or pharmacologic inhibition of c-Myc suppressed proliferation of mutant biliary spheroids, whereas silencing of Smad4/Tgfbr2 or pharmacologic inhibition of TGFβ signaling increased proliferation of mutant biliary spheroids and cancer formation in vivo. Human ICPNs displayed activated Kras and Wnt signals and c-Myc and TGFβ pathways. Thus, these data provide direct evidence that concurrent activation of the Kras and canonical Wnt pathways results in formation of ICPN and BilIN, which could develop into biliary cancer.

SIGNIFICANCE

This work shows how dysregulation of canonical cell growth pathways drives precursors to biliary cancers and identifies several molecular vulnerabilities as potential therapeutic targets in these precursors to prevent oncogenic progression.

Treatment of Resectable Gallbladder Cancer

Gallbladder cancer (GBC) is the most common biliary tract cancer worldwide and its incidence has significant geographic variation. A unique combination of predisposing factors includes genetic predisposition, geographic distribution, female gender, chronic inflammation, and congenital developmental abnormalities. Today, incidental GBC is the most common presentation of resectable gallbladder cancer, and surgery (minimally invasive or open) remains the only curative treatment available. Encouragingly, there is an important emerging role for systemic treatment for patients who have R1 resection or present with stage III-IV. In this article, we describe the pathogenesis, surgical and systemic treatment, and prognosis.

Precursor Lesions of Gallbladder Carcinoma: Disease Concept, Pathology, and Genetics

Understanding the pathogenesis and carcinogenesis of gallbladder adenocarcinoma is important. The fifth edition of the World Health Organization’s tumor classification of the digestive system indicates three types of preinvasive neoplasm of the gallbladder: pyloric gland adenoma (PGA), biliary intraepithelial neoplasia (BilIN), and intracholecystic papillary neoplasm (ICPN). New terminologies have also been introduced, such as intracholecystic papillary-tubular neoplasm, gastric pyloric, simple mucinous type, and intracholecystic tubular non-mucinous neoplasm (ICTN). Pancreatobiliary maljunction (PBM) poses a markedly high risk for bile duct carcinoma, which was analyzed and investigated mainly by Asian researchers in the past; however, recent studies have clarified a similar significance of biliary carcinogenesis in Western countries as well. In this study, we reviewed and summarized information on three gallbladder neoplastic precursors, PGA, BilIN, and ICPN, and gallbladder lesions in patients with PBM.

Gallbladder adenocarcinomas undergo subclonal diversification and selection from precancerous lesions to metastatic tumors

We aimed to elucidate the evolutionary trajectories of gallbladder adenocarcinoma (GBAC) using multi-regional and longitudinal tumor samples. Using whole-exome sequencing data, we constructed phylogenetic trees in each patient and analyzed mutational signatures. A total of 11 patients including 2 rapid autopsy cases were enrolled. The most frequently altered gene in primary tumors was ERBB2 and TP53 (54.5%), followed by FBXW7 (27.3%). Most mutations in frequently altered genes in primary tumors were detectable in concurrent precancerous lesions (biliary intraepithelial neoplasia [BilIN]), but a substantial proportion was subclonal. Subclonal diversity was common in BilIN (n=4). However, among subclones in BilIN, a certain subclone commonly shrank in concurrent primary tumors. In addition, selected subclones underwent linear and branching evolution, maintaining subclonal diversity. Combined analysis with metastatic tumors (n=11) identified branching evolution in nine patients (81.8%). Of these, eight patients (88.9%) had a total of 11 subclones expanded at least sevenfold during metastasis. These subclones harbored putative metastasis-driving mutations in cancer-related genes such as SMAD4, ROBO1, and DICER1. In mutational signature analysis, six mutational signatures were identified: 1, 3, 7, 13, 22, and 24 (cosine similarity >0.9). Signatures 1 (age) and 13 (APOBEC) decreased during metastasis while signatures 22 (aristolochic acid) and 24 (aflatoxin) were relatively highlighted. Subclonal diversity arose early in precancerous lesions and clonal selection was a common event during malignant transformation in GBAC. However, selected cancer clones continued to evolve and thus maintained subclonal diversity in metastatic tumors.