Expression and localization of the mechanosensitive/osmosensitive ion channel TMEM63B in the mouse urinary tract.

The epithelial cells that line the kidneys and lower urinary tract are exposed to mechanical forces including shear stress and wall tension; however, the mechanosensors that detect and respond to these stimuli remain obscure. Candidates include the OSCA/TMEM63 family of ion channels, which can function as mechanosensors and osmosensors. Using Tmem63bHA-fl/HA-fl reporter mice, we assessed the localization of HA-tagged-TMEM63B within the urinary tract by immunofluorescence coupled with confocal microscopy. In the kidneys, HA-TMEM63B was expressed by proximal tubule epithelial cells, by the intercalated cells of the collecting duct, and by the epithelial cells lining the thick ascending limb of the medulla. In the urinary tract, HA-TMEM63B was expressed by the urothelium lining the renal pelvis, ureters, bladder, and urethra. HA-TMEM63B was also expressed in closely allied organs including the epithelial cells lining the seminal vesicles, vas deferens, and lateral prostate glands of male mice and the vaginal epithelium of female mice. Our studies reveal that TMEM63B is expressed by subsets of kidney and lower urinary tract epithelial cells, which we hypothesize are sites of TMEM63B mechanosensation or osmosensation, or both.

[Practical application of the Paris system for reporting urinary cytology].

Objective: To validate the diagnostic performance of the Paris system for reporting urinary cytology (TPS). Methods: A total of 7 046 urine cytology samples from 3 402 patients collected in the Department of Pathology, Beijing Hospital, China from January 2020 to January 2022 were analyzed. 488 patients had a biopsy or resection specimen during the follow-up period of 6 months. The sensitivity, specificity, risk of malignancy (ROM) and risk of high-grade malignancy (ROHM) of the TPS were evaluated using histological diagnosis as the golden standard. Results: Among the 7 046 samples, high-grade urothelial carcinoma (HGUC) accounted for 5.7% (399/7 046), suspicious for high-grade urothelial carcinoma (SHGUC) for 3.2% (227/7 046), atypical urothelial cells (AUC) for 8.4% (593/7 046), and negative for high-grade urothelial carcinoma (NHGUC) for 72.9% (5 139/7 046) including low-grade urothelial neoplasm (LGUN) for 0.8% (59/7 046) and insufficient samples for 9.8% (688/7 046). 488 patients had a bladder biopsy or resection in the follow-up of six months, including 314 males and 174 females, aged 27 to 92 years (average, 66 years). The ROHM of TPS was 94.7% in HGUC, 83.3% in SHGUC, 41.3% in AUC and 18.8% in NHGUC. The sensitivity and specificity of urine cytology were 70.1% (169/241) and 97.0% (162/167), respectively. The negative predictive value of NHGUC was 69.2% (162/234). Conclusions: The study has shown that TPS classification has high sensitivity and specificity, high ROHM for HGUC and SHGUC, and high negative predictive value for NHGUC. The application of TPS reporting system can better interpret the clinical significance of cytology samples, improve the accuracy of urine cytopathology and ensure continuous diagnostic consistency.

Epithelial development of the urinary collecting system in the human embryo.

The urinary collecting system (UCS) consists of organized ducts that collect urine from the nephrons and transport it to the ureter and bladder. Understanding the histogenesis of the UCS is critical. Thirty human embryos between the Carnegie stages (CS) 18 and 23 were selected from the Congenital Anomaly Research Center, Kyoto, Japan. Epithelia of the UCS, ureter, and bladder of each sample were randomly selected. Histological findings of the epithelia were analyzed according to the following criteria: type of epithelium, presence or absence of glycogen, percentage of migrated nuclei, percentage of cells in mitosis, and the surrounding mesenchyme. A thickened epithelium lining a narrow luminal cavity was observed in the pre-expanded pelvic specimens at CS18-CS23. At CS23, after pelvic expansion, the UCS showed a thin epithelium with a large luminal cavity mainly located on the early branches, whereas the epithelium covering the subsequent branches had medium thickness. Histological characteristics differed depending on the UCS part and sample stage. The degree of differentiation was evaluated, revealing that in CS18-CS23 pre-expanded pelvis specimens, the undifferentiated epithelium was found in the zeroth to third/fifth generation, whereas at CS23, after pelvic expansion, a differentiated epithelium covered the UCS zeroth to seventh generation. In a comparison of the urothelial epithelium between the UCS, ureter, and bladder, we found that urinary tract differentiation may be initiated in the bladder, followed by the ureter, UCS zeroth to seventh generations, and finally, UCS eighth to end generations. An understanding of the histogenesis of embryonic stage UCS can aid in the clinical management of congenital urinary tract defects and other diseases.

Enhancing upper tract urothelial carcinoma diagnosis: Utility of cytokeratin 17 and CK20/CD44/p53 immunohistochemical panel.

Upper tract urothelial carcinoma (UTUC) presents diagnostic challenges due to small biopsy specimen size, poor orientation, and technical obstacles that can yield equivocal diagnoses. This uncertainty often mandates repeated biopsies to evaluate the necessity of nephroureterectomy. Prior studies have suggested cytokeratin 17 (CK17) immunostain as an adjunctive tool for diagnosing bladder urothelial neoplasia in both urine cytology and tissue biopsy specimens. We evaluated the utility of CK17 in differentiating UTUC from benign urothelium and its ability to stratify low-grade from high-grade neoplasia. Our study involved a cohort of previously diagnosed cytology (n = 29) and tissue specimens from biopsies and resections (n = 85). We evaluated CK17 staining percentage in cytology and tissue samples and localization patterns in biopsy/resection samples. Our findings showed a statistically significant distinction (p < 0.05) between UTUC and benign tissue specimens based on full thickness localization pattern (odds ratio 8.8 [95% CI 1.53-67.4]). The percentage of CK17 staining failed to significantly differentiate neoplastic from non-neoplastic cases in cytology or tissue samples. Additionally, based on prior research showing the efficacy of CK20/CD44/p53 triple panel in bladder urothelial neoplasia, we utilized tissue microarrays to evaluate if these markers could distinguish UTUC from benign urothelium. We found that CK20/CD44/p53, individually or in combination, could not distinguish urothelial neoplasia from non-neoplasia. Full thickness CK17 urothelial localization by immunohistochemistry was highly reproducible with excellent interobserver agreement and may play a supplementary role in distinguishing upper tract urothelial neoplasia from benign urothelium.

Scoring PD-L1 Expression in Urothelial Carcinoma: An International Multi-Institutional Study on Comparison of Manual and Artificial Intelligence Measurement Model (AIM-PD-L1) Pathology Assessments.

Assessing programmed death ligand 1 (PD-L1) expression on tumor cells (TCs) using Food and Drug Administration-approved, validated immunoassays can guide the use of immune checkpoint inhibitor (ICI) therapy in cancer treatment. However, substantial interobserver variability has been reported using these immunoassays. Artificial intelligence (AI) has the potential to accurately measure biomarker expression in tissue samples, but its reliability and comparability to standard manual scoring remain to be evaluated. This multinational study sought to compare the %TC scoring of PD-L1 expression in advanced urothelial carcinoma, assessed by either an AI Measurement Model (AIM-PD-L1) or expert pathologists. The concordance among pathologists and between pathologists and AIM-PD-L1 was determined. The positivity rate of ≥ 1%TC PD-L1 was between 20-30% for 8/10 pathologists, and the degree of agreement and scoring distribution for among pathologists and between pathologists and AIM-PD-L1 was similar both scored as a continuous variable or using the pre-defined cutoff. Numerically higher score variation was observed with the 22C3 assay than with the 28-8 assay. A 2-h training module on the 28-8 assay did not significantly impact manual assessment. Cases exhibiting significantly higher variability in the assessment of PD-L1 expression (mean absolute deviation > 10) were found to have patterns of PD-L1 staining that were more challenging to interpret. An improved understanding of sources of manual scoring variability can be applied to PD-L1 expression analysis in the clinical setting. In the future, the application of AI algorithms could serve as a valuable reference guide for pathologists while scoring PD-L1.

UPK3A+ umbrella cell damage mediated by TLR3-NR2F6 triggers programmed destruction of urothelium in Hunner-type interstitial cystitis/painful bladder syndrome.

Urothelial damage and barrier dysfunction emerge as the foremost mechanisms in Hunner-type interstitial cystitis/bladder pain syndrome (HIC). Although treatments aimed at urothelial regeneration and repair have been employed, their therapeutic effectiveness remains limited due to the inadequate understanding of specific cell types involved in damage and the lack of specific molecular targets within these mechanisms. Therefore, we harnessed single-cell RNA sequencing to elucidate the heterogeneity and developmental trajectory of urothelial cells within HIC bladders. Through reclustering, we identified eight distinct clusters of urothelial cells. There was a significant reduction in UPK3A+ umbrella cells and a simultaneous increase in progenitor-like pluripotent cells (PPCs) within the HIC bladder. Pseudotime analysis of the urothelial cells in the HIC bladder revealed that cells faced challenges in differentiating into UPK3A+ umbrella cells, while PPCs exhibited substantial proliferation to compensate for the loss of UPK3A+ umbrella cells. The urothelium in HIC remains unrepaired, despite the substantial proliferation of PPCs. Thus, we propose that inhibiting the pivotal signaling pathways responsible for the injury to UPK3A+ umbrella cells is paramount for restoring the urothelial barrier and alleviating lower urinary tract symptoms in HIC patients. Subsequently, we identified key molecular pathways (TLR3 and NR2F6) associated with the injury of UPK3A+ umbrella cells in HIC urothelium. Finally, we conducted in vitro and in vivo experiments to confirm the potential of the TLR3-NR2F6 axis as a promising therapeutic target for HIC. These findings hold the potential to inhibit urothelial injury, providing promising clues for early diagnosis and functional bladder self-repair strategies for HIC patients. © 2024 The Pathological Society of Great Britain and Ireland.

Innervation pattern of the unclosed detrusor muscle in classic bladder exstrophy: a study of patients with urothelial overexpression of nerve growth factor.

PURPOSE: An overexpression of nerve growth factor (NGF) in the urothelium is discussed to lead to neuronal hyperinnervation of the bladder detrusor. The aim was to assess the sensory and sympathetic innervation of the detrusor in unclosed exstrophic bladders patients with known overexpression of NGF in the urothelium. METHODS: Full-thickness bladder biopsies were prospectively obtained from 34 infants at delayed primary bladder closure between 01/2015 and 04/2020. The bladder biopsies were immunohistochemically stained with antibodies against S100, calcitonin gene-related peptide (anti-CGRP), Neurofilament 200 (anti-NF200), and tyrosine-hydroxylase (anti-TH). Specimens from 6 children with congenital vesicoureterorenal reflux (VUR) served as controls. RESULTS: There was no statistically significant difference in nerve fiber density in any of the immunohistochemical assessments (anti-S100 [p = 0.210], anti-CGRP [p = 0.897], anti-NF200 [p = 0.897]), and anti-TH [p = 0.956]) between patients with BE and patients with VUR. However, we observed a trend toward lower nerve fiber densities in exstrophic detrusor. CONCLUSION: Overall our results showed an unharmed innervation pattern in this cohort but a lower density of nerve fibers in the detrusor compared to controls. Further studies in patients after successful primary closure are needed to clarify the potential impact of the urothelial overexpression of NGF modulating the innervation pattern in exstrophic bladders.

Insulin receptor signaling engages bladder urothelial defenses that limit urinary tract infection.

Urinary tract infections (UTIs) commonly afflict people with diabetes. To better understand the mechanisms that predispose diabetics to UTIs, we employ diabetic mouse models and altered insulin signaling to show that insulin receptor (IR) shapes UTI defenses. Our findings are validated in human biosamples. We report that diabetic mice have suppressed IR expression and are more susceptible to UTIs caused by uropathogenic Escherichia coli (UPEC). Systemic IR inhibition increases UPEC susceptibility, while IR activation reduces UTIs. Localized IR deletion in bladder urothelium promotes UTI by increasing barrier permeability and suppressing antimicrobial peptides. Mechanistically, IR deletion reduces nuclear factor κB (NF-κB)-dependent programming that co-regulates urothelial tight junction integrity and antimicrobial peptides. Exfoliated urothelial cells or urine samples from diabetic youths show suppressed expression of IR, barrier genes, and antimicrobial peptides. These observations demonstrate that urothelial insulin signaling has a role in UTI prevention and link IR to urothelial barrier maintenance and antimicrobial peptide expression.

Gene of the month: the uroplakins.

Uroplakins are a family of membrane-spanning proteins highly specific to the urothelium. There are four uroplakin proteins in humans. These are encoded by the following UPK genes: UPK1A, UPK1B, UPK2 and UPK3 Uroplakin proteins span the apical membrane of umbrella cells of the urothelium, where they associate into urothelial plaques. This provides a barrier function to prevent passage of urine across the urothelium in the renal pelvis, ureters, and bladder. Uroplakins are also involved in developmental processes such as nephrogenesis. The specific localisation of uroplakins within the urothelium means that they are often expressed in primary and metastatic urothelial cell carcinoma and may be used as an immunohistochemical marker of urothelial malignancy.

A biophysically comprehensive model of urothelial afferent neurons: implications for sensory signalling in urinary bladder.

The urothelium is the innermost layer of the bladder wall; it plays a pivotal role in bladder sensory transduction by responding to chemical and mechanical stimuli. The urothelium also acts as a physical barrier between urine and the outer layers of the bladder wall. There is intricate sensory communication between the layers of the bladder wall and the neurons that supply the bladder, which eventually translates into the regulation of mechanical activity. In response to natural stimuli, urothelial cells release substances such as ATP, nitric oxide (NO), substance P, acetylcholine (ACh), and adenosine. These act on adjacent urothelial cells, myofibroblasts, and urothelial afferent neurons (UAN), controlling the contractile activity of the bladder. There is rising evidence on the importance of urothelial sensory signalling, yet a comprehensive understanding of the functioning of the urothelium-afferent neurons and the factors that govern it remains elusive to date. Until now, the biophysical studies done on UAN have been unable to provide adequate information on the ion channel composition of the neuron, which is paramount to understanding the electrical functioning of the UAN and, by extension, afferent signalling. To this end, we have attempted to model UAN to decipher the ionic mechanisms underlying the excitability of the UAN. In contrast to previous models, our model was built and validated using morphological and biophysical properties consistent with experimental findings for the UAN. The model included all the channels thus far known to be expressed in UAN, including; voltage-gated sodium and potassium channels, N, L, T, P/Q, R-type calcium channels, large-conductance calcium-dependent potassium (BK) channels, small conductance calcium-dependent (SK) channels, Hyperpolarisation activated cation (HCN) channels, transient receptor potential melastatin (TRPM8), transient receptor potential vanilloid (TRPV1) channel, calcium-activated chloride(CaCC) channels, and internal calcium dynamics. Our UAN model a) was constrained as far as possible by experimental data from the literature for the channels and the spiking activity, b) was validated by reproducing the experimental responses to current-clamp and voltage-clamp protocols c) was used as a base for modelling the non-urothelial afferent neurons (NUAN). Using our models, we also gained insights into the variations in ion channels between UAN and NUAN neurons.

Papillary urothelial neoplasm of low malignant potential with osseous metaplasia in a 19-year-old chronic smoker: A case report with review of literature.

Urothelial tumors characteristically occur in elderly persons, more commonly in males with typical complaints of hematuria. Although few studies attempted to describe clinic-pathological features of urothelial malignancies in young patients, due to heterogeneity in the inclusion of age groups under "young patients" no reliable conclusions can be derived. Herein, we are describing an interesting case of papillary urothelial neoplasm of low malignant potential with osseous metaplasia in a 19-year-old chronic smoker young patient presented with chief complaints of abdominal pain with a review of the literature.

Metastatic upper tract urothelial carcinoma with nest-like features presenting as malignant pleural effusion.

Metastatic urothelial carcinoma is a rare cause of pleural effusions. We report a case of urothelial carcinoma of the upper urinary tract in an oldest-old male patient, a smoker, with situs inversus totalis, that presented uniquely with malignant pleural effusion at presentation without evidence of a primary tumor on imaging. Cytological smears of the massive left pleural effusion revealed epithelioid neoplastic cells arranged in short cords, small-to-large clusters, and raspberry-like morules, mimicking mesothelioma; cell block preparations highlighted the presence of tubules and nest-like structures. The tumor cells showed a high nuclear-to-cytoplasmic ratio, nuclear grooves, and mitotic figures. Cytomorphologic features coupled with the immunophenotype of neoplastic cells (p63, GATA3, and uroplakin II positive) allowed the diagnosis of metastatic urothelial carcinoma and a possible nested subtype. These findings were supported by a total body computed tomography (CT) showing no evidence of a mass in the bladder or elsewhere in the urinary tract but a concentric parietal thickening of the proximal left ureter, suggesting malignancy. To our knowledge, a malignant effusion as a primary manifestation of urothelial carcinoma with nest-like features originating in the upper urinary tract has never been described previously. Our case focuses on the value of cell block in the working-up of neoplastic effusions by revealing the architectural pattern of an uncommon malignancy and the correlation between cytopathology and imaging gross findings to reach an accurate diagnosis.

Implementation of The Paris System for Reporting Urine Cytology improves diagnostic accuracy of selective upper urinary tract cytology.

BACKGROUND: The Paris System for Reporting Urine Cytology (TPS) recommends diagnostic criteria for urinary tract cytology, focusing primarily on the detection of high-grade urothelial carcinoma (HGUC) in the lower urinary tract. The second edition of TPS (TPS 2.0), published in 2022, extends these recommendations to the upper urinary tract (UUT); however, there is a lack of comprehensive data on this subject. METHODS: In total, 223 consecutive UUT cytology specimens from 137 patients were retrieved and reclassified according to TPS 2.0 criteria and were compared with the original diagnosis based on the conventional system (CS). Histologic follow-up within a 3-month period was conducted for 43 patients. RESULTS: Histologic follow-up revealed 30 HGUCs, five low-grade urothelial carcinomas (LGUCs), and eight nonneoplastic fibrotic tissues. The risk of high-grade malignancy for each TPS diagnostic category was 16.7% for nondiagnostic/unsatisfactory, 2.3% for negative for HGUC (NHGUC), 42.1% for atypical urothelial cells, 50.0% for suspicious for HGUC (SHGUC), and 81.8% for HGUC. In all five cases of histologically diagnosed LGUC, the cytologic diagnosis was NHGUC. When SHGUC/HGUC was considered positive, the diagnostic accuracy of TPS had 63% sensitivity, 95% specificity, a 90% negative predictive value, and a 79% positive predictive value, which were better than those of CS. In addition, the TPS indices did not differ significantly between the specimens obtained before and after the application of contrast reagents. CONCLUSIONS: TPS implementation improved the accuracy of UUT cytology in predicting histologic HGUC, which was unaffected by the application of contrast reagents. These data indicate the usefulness of TPS for UUT cytology in routine clinical settings.

Urinary tract cytology showing variant morphology and divergent differentiation.

Urothelial carcinoma represents a diverse group of tumours with distinct histologic subtypes, each exhibiting unique cytomorphologic features, architectural growth patterns, and/or well-developed aberrant differentiation. In fact, there are more than 13 subtypes of urothelial carcinoma recognized in the 2022 WHO classification of tumours in the urinary tract. The identification of these subtypes is crucial for an accurate diagnosis of urothelial carcinoma, and many have important clinical implications. Variant/divergent features may coexist with conventional high-grade urothelial carcinoma (HGUC) or present with 100% variant morphology. In urinary tract cytology (UTC), urothelial carcinoma can display divergent differentiation, such as squamous, glandular, or small cell carcinoma differentiation. The use of cell block preparations and immunohistochemistry with available residual urine can enhance diagnostic accuracy. On the other hand, identifying urothelial carcinoma variants, including nested, micropapillary, and plasmacytoid subtypes, poses significant challenges in UTC. Many cases of these variants are only detected retrospectively after variant histology has been established from resection specimens. Moreover, some variants exhibit features inconsistent with the diagnostic criteria for HGUC according to the Paris System for Reporting Urinary Tract Cytology. Nevertheless, the rarity of pure variant morphology and the occurrence of some false negatives for these variant cases are essential to maintain the specificity of UTC overall. This review covers the histology, cytomorphology, and important clinical aspects observed in urothelial carcinoma exhibiting divergent differentiation and various urothelial carcinoma variants detected in UTC.

Deficiency of Pdcd10 causes urothelium hypertrophy and vesicle trafficking defects in ureter.

The scaffolding protein programmed cell death protein 10 (Pdcd10) has been demonstrated to play a critical role in renal epithelial cell homeostasis and function by maintaining appropriate water reabsorption in collecting ducts. Both ureter and kidney collecting duct systems are derived from the ureter bud during development. Here, we report that cadherin-16 (Cdh16)-cre drives gene recombination with high specificity in the ureter, but not the bladder, urothelium. The consequences of Pdcd10 deletion on the stratified ureter urothelium were investigated using an integrated approach including messenger RNA (mRNA) expression analysis, immunocytochemistry, and high-resolution confocal and electron microscopy. Loss of Pdcd10 in the ureter urothelium resulted in increased expression of uroplakins (Upks) and keratins (Krts), as well as hypertrophy of the ureter urothelium with an associated increase in the number of proliferation marker protein Ki-67 (Ki67)-expressing cells specifically within the basal urothelium layer. Ultrastructural analysis documented significant modification of the intracellular membrane system, including intracellular vesicle genesis and transport along the basal- to umbrella-cell-layer axis. Additionally, Pdcd10 loss resulted in swelling of Golgi compartments, disruption of mitochondrial cristae structure, and increased lysosomal fusion. Lack of Pdcd10 also resulted in decreased fusiform vesicle formation in umbrella cells, increased secretion of exosome vesicles, and alteration in microvillar structure on apical membranes. Our findings indicate that Pdcd10 expression and its influence on homeostasis is associated with modulation of endomembrane trafficking and organelle biogenesis in the ureter urothelium.

Restoring the barrier of chronically damaged urothelium using chondroitin sulfate glycosaminoglycan-replenishment therapy.

PURPOSE OF REVIEW: This study aims to further understand the physiological mechanism of chondroitin sulfate treatment on the urinary bladder in cases of inflammation, by investigating the effect of chondroitin sulfate therapy on recovery of urothelial barrier in an in-vitro chronic injury model. RECENT FINDINGS: With inflammatory bladder conditions, the urothelial barrier seems decreased. Glycosaminoglycan (GAG) replacement therapy is supposed to help restore this barrier. Clinical studies on inflammatory bladder conditions are complicated because of the heterogeneous patient population, hence the need for preclinical models. SUMMARY: In a model using porcine urothelial cells, functional barrier (TEER) and barrier markers were assessed. Chronic urothelial damage was simulated through protamine sulfate instillations with and without subsequent chondroitin sulfate instillations during 3 days. Chondroitin sulfate instillations significantly improved TEER compared to protamine sulfate treatment only (TEER difference 310 Ω.cm 2 , P  < 0.001). This consistent effect over 3 days resulted in a significant higher mean TEER value in the chondroitin sulfate treated group (difference 1855 Ω.cm 2 , P  < 0.001). Enhanced recovery of chondroitin sulfate and other barrier markers was observed.Chondroitin sulfate therapy shows promise in facilitating the recovery of the urothelial barrier in cases of chronic damage. This preclinical study lends support to the use of clinical GAG replenishment therapy for patients with a chronically impaired urothelium.

The urothelial gene regulatory network: understanding biology to improve bladder cancer management.

The urothelium is a stratified epithelium composed of basal cells, one or more layers of intermediate cells, and an upper layer of differentiated umbrella cells. Most bladder cancers (BLCA) are urothelial carcinomas. Loss of urothelial lineage fidelity results in altered differentiation, highlighted by the taxonomic classification into basal and luminal tumors. There is a need to better understand the urothelial transcriptional networks. To systematically identify transcription factors (TFs) relevant for urothelial identity, we defined highly expressed TFs in normal human bladder using RNA-Seq data and inferred their genomic binding using ATAC-Seq data. To focus on epithelial TFs, we analyzed RNA-Seq data from patient-derived organoids recapitulating features of basal/luminal tumors. We classified TFs as "luminal-enriched", "basal-enriched" or "common" according to expression in organoids. We validated our classification by differential gene expression analysis in Luminal Papillary vs. Basal/Squamous tumors. Genomic analyses revealed well-known TFs associated with luminal (e.g., PPARG, GATA3, FOXA1) and basal (e.g., TP63, TFAP2) phenotypes and novel candidates to play a role in urothelial differentiation or BLCA (e.g., MECOM, TBX3). We also identified TF families (e.g., KLFs, AP1, circadian clock, sex hormone receptors) for which there is suggestive evidence of their involvement in urothelial differentiation and/or BLCA. Genomic alterations in these TFs are associated with BLCA. We uncover a TF network involved in urothelial cell identity and BLCA. We identify novel candidate TFs involved in differentiation and cancer that provide opportunities for a better understanding of the underlying biology and therapeutic intervention.