Neuroendocrine Differentiation Research Articles

Androgen deprivation induces neuroendocrine phenotypes in prostate cancer cells through CREB1/EZH2-mediated downregulation of REST.

Although effective initially, prolonged androgen deprivation therapy (ADT) promotes neuroendocrine differentiation (NED) and prostate cancer (PCa) progression. It is incompletely understood how ADT transcriptionally induces NE genes in PCa cells. CREB1 and REST are known to positively and negatively regulate neuronal gene expression in the brain, respectively. No direct link between these two master neuronal regulators has been elucidated in the NED of PCa. We show that REST mRNA is downregulated in NEPC cell and mouse models, as well as in patient samples. Phenotypically, REST overexpression increases ADT sensitivity, represses NE genes, inhibits colony formation in culture, and xenograft tumor growth of PCa cells. As expected, ADT downregulates REST in PCa cells in culture and in mouse xenografts. Interestingly, CREB1 signaling represses REST expression. In studying the largely unclear mechanism underlying transcriptional repression of REST by ADT, we found that REST is a direct target of EZH2 epigenetic repression. Finally, genetic rescue experiments demonstrated that ADT induces NED through EZH2's repression of REST, which is enhanced by ADT-activated CREB1 signaling. In summary, our study has revealed a key pathway underlying NE gene upregulation by ADT, as well as established novel relationships between CREB1 and REST, and between EZH2 and REST, which may also have implications in other cancer types and in neurobiology.

PAX6 promotes neuroendocrine phenotypes of prostate cancer via enhancing MET/STAT5A-mediated chromatin accessibility

BackgroundNeuroendocrine prostate cancer (NEPC) is a lethal subset of prostate cancer which is characterized by neuroendocrine differentiation and loss of androgen receptor (AR) signaling. Growing evidence reveals that cell lineage plasticity is crucial in the failure of NEPC therapies. Although studies suggest the involvement of the neural transcription factor PAX6 in drug resistance, its specific role in NEPC remains unclear.MethodsThe expression of PAX6 in NEPC was identified via bioinformatics and immunohistochemistry. CCK8 assay, colony formation assay, tumorsphere formation assay and apoptosis assay were used to illustrate the key role of PAX6 in the progression of in vitro. ChIP and Dual-luciferase reporter assays were conducted to confirm the binding sequences of AR in the promoter region of PAX6, as well as the binding sequences of PAX6 in the promoter regions of STAT5A and MET. For in vivo validation, the xenograft model representing NEPC subtype underwent pathological analysis to verify the significant role of PAX6 in disease progression. Complementary diagnoses were established through public clinical datasets and transcriptome sequencing of specific cell lines. ATAC-seq was used to detect the chromatin accessibility of specific cell lines.ResultsPAX6 expression was significantly elevated in NEPC and negatively regulated by AR signaling. Activation of PAX6 in non-NEPC cells led to NE trans-differentiation, while knock-down of PAX6 in NEPC cells inhibited the development and progression of NEPC. Importantly, loss of AR resulted in an enhanced expression of PAX6, which reprogramed the lineage plasticity of prostate cancer cells to develop NE phenotypes through the MET/STAT5A signaling pathway. Through ATAC-seq, we found that a high expression level of PAX6 elicited enhanced chromatin accessibility, mainly through attenuation of H4K20me3, which typically causes chromatin silence in cancer cells.ConclusionThis study reveals a novel neural transcription factor PAX6 could drive NEPC progression and suggest that it might serve as a potential therapeutic target for the management of NEPC.

CYB561 supports the neuroendocrine phenotype in castration-resistant prostate cancer.

Castration-resistant prostate cancer (CRPC) is associated with resistance to androgen deprivation therapy, and an increase in the population of neuroendocrine (NE) differentiated cells. It is hypothesized that NE differentiated cells secrete neuropeptides that support androgen-independent tumor growth and induce aggressiveness of adjacent proliferating tumor cells through a paracrine mechanism. The cytochrome b561 (CYB561) gene, which codes for a secretory vesicle transmembrane protein, is constitutively expressed in NE cells and highly expressed in CRPC. CYB561 is involved in the α-amidation-dependent activation of neuropeptides, and contributes to regulating iron metabolism which is often dysregulated in cancer. These findings led us to hypothesize that CYB561 may be a key player in the NE differentiation process that drives the progression and maintenance of the highly aggressive NE phenotype in CRPC. In our study, we found that CYB561 expression is upregulated in metastatic and NE prostate cancer (NEPC) tumors and cell lines compared to normal prostate epithelia, and that its expression is independent of androgen regulation. Knockdown of CYB561 in androgen-deprived LNCaP cells dampened NE differentiation potential and transdifferentiation-induced increase in iron levels. In NEPC PC-3 cells, depletion of CYB561 reduced the secretion of growth-promoting factors, lowered intracellular ferrous iron concentration, and mitigated the highly aggressive nature of these cells in complementary assays for cancer hallmarks. These findings demonstrate the role of CYB561 in facilitating transdifferentiation and maintenance of NE phenotype in CRPC through its involvement in neuropeptide biosynthesis and iron metabolism pathways.

Non-metastatic primary neuroendocrine neoplasms of the breast: a reference cancer center's experience of a heterogenous entity.

Primary neuroendocrine neoplasms of the breast (Br-NENs) are rare. The classification has been updated in recent years making interpretation of the data published challenging. It is unclear whether neuroendocrine differentiation is associated with poorer prognosis and what treatment approaches should be applied. The database for breast cancer patients treated between 2009 and 2022 at the Maria Sklodowska-Curie National Research Institute of Oncology Branch Krakow was explored to search for Br-NENs. Patients' medical and pathological data were collected and analyzed. We included 22 females with Br-NEN without metastases at the time of diagnosis. The median age was 64 years (range: 28-88), Of the cases, 18 were hormone receptor positive, all were HER-2 negative, the median Ki67 was 27% (10-100%). The median tumor size at the time of diagnosis was 29.5mm (7-75mm), 9 patients were N-positive. DCIS was present in 5 cases. Only one case was negative for chromogranin and synaptophysin staining, but data were missing for 4 cases. Nine patients received adjuvant chemotherapy, mainly based on anthracyclines and taxanes, while 16 received adjuvant hormonal therapy and 15 received postoperative radiotherapy. Radical surgery was performed in all patients, but two underwent suboptimal tumorectomy. One patient had local recurrence, three experienced metastatic disease, all involving the lungs, but these patients are still alive. The median follow-up was 96 months (8-153). Two patients died, with a follow up time of no recurrence >4 years. Our results were compared to twelve case series collecting clinical data on Br-NENs, with median patient number of 10.5 (range: 3-142). Br-NENs represent a heterogenous group of diseases, lacking data from prospective studies or clinical trials. There are no established treatment standards tailored for Br-NENs. Our patients' cohort exhibited a favorable prognosis, potentially attributed to lower tumor stage and Ki67 index compared to other reported case series. We suggest that radical surgery and postoperative radiotherapy be administered akin to standard treatment for breast cancer of no special type. ESMO also advocates for this approach in systemic treatment, although we recommend considering platinum-based chemotherapy for patients with poorly differentiated Br-NENs exhibiting high Ki67.

Abstract PO3-08-05: Prognostic value of multigene test to the patients with Hormone receptor-positive, HER2-negative breast cancer based on special histologic subtypes

Abstract Background: Special histologic subtypes of breast cancer, including mucinous and tubular, account for 25% of all invasive breast cancers. Multigene tests (MGT) play a crucial role in guiding adjuvant chemotherapy and predicting prognosis for the patients with Hormone receptor-positive HER2-negative breast cancer. This research aims to examine the results of multigene tests for special histologic subtype patients and review the prognosis of each group. Methods: A retrospective analysis was conducted on data from 133 patients with special histologic subtypes of breast cancer who underwent surgery at Severance Hospital between November 2013 and December 2022. Each patient underwent one type of MGT, including Oncotype Dx, MammaPrint, or EndoPredict. Patients were grouped in two groups according to histologic types, based on WHO classification. Favorable types consist of type A mucinous carcinoma, pure tubular carcinoma, invasive solid papillary carcinoma, encapsulated papillary carcinoma with invasion, invasive cribriform carcinoma, secretory carcinoma, and invasive carcinoma with apocrine differentiation. Unfavorable types included type B mucinous carcinoma, mucinous carcinoma with micropapillary feature or neuroendocrine differentiation, mixed IDC, ILC or invasive micropapillary carcinoma, mixed invasive solid papillary carcinoma, mixed invasive papillary carcinoma, and mixed invasive cribriform carcinoma with IDC. Results: Patients with favorable types accounted for 42.86% (57 patients), while patients with unfavorable types accounted for 57.14% (76 patients). Patients with unfavorable histologic subtypes of breast cancer tended to have a higher incidence of high-risk results in MGT, as well as a greater prevalence of multiple (multifocal, multicentric) cancer and higher histologic grade. In multivariate analysis using logistic regression, unfavorable types showed a significantly high ratio of having high risk on MGT compared to the favorable type (OR = 4.327, 95% CI 1.210 – 15.475, p-value = 0.024). Moreover, overall survival in unfavorable histologic types showed a statistically significant difference between high-risk and low-risk in Kaplan-Meier survival analysis (p-value = 0.001). Conclusions: Unfavorable subtypes have shown a significantly higher-risk result of MGT, and patients with unfavorable types of breast cancer and high-risk MGT results have exhibited the worst prognosis. Consequently, we can suggest that MGT can be used as a prognosis evaluation tool for certain special subtypes of breast cancer and further utilized to aid in treatment decisions. Citation Format: Seung Hye Yang, Jee Hyun Ahn, Suk Jun Lee, Jee Ye Kim, Hyung Seok Park, Seung Il Kim, Byeong Woo Park, Seho Park. Prognostic value of multigene test to the patients with Hormone receptor-positive, HER2-negative breast cancer based on special histologic subtypes [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-08-05.

Abstract PO2-16-11: Real-World Data of Neuroendocrine Neoplasms of Breast

Abstract Background: Primary neuroendocrine neoplasms (NEN) of breast are rare and heterogeneous. WHO has classified NENs of non-endocrine organs into three distinct categories in 2022, however real-world data on outcomes of patients with NENs of non-endocrine organs under this new classification system are still sparse. Real world experience regarding demography, clinical presentation, treatment response, and prognosis can help identify potential areas of improvement in the management of breast NEN. Methods: Here, we present our findings from patients with NEN of breast in the Cleveland Clinic Foundation between 2000 and 2023. Pathology reports were reviewed to confirm NEN of breast origin. Neuroendocrine differentiation was determined by tumor histology and immunohistochemistry (IHC). For metastatic tumors at presentation, primary organ was determined by IHC and clinical presentation. Overall survival (OS) was from date of diagnosis of NEN. Recurrence is redemonstration of tumor following curative intent therapy, and progression is increase in tumor burden. T-test and log-rank test were used in statistical analyses. Results: Total of 97 patients were identified. Of these, 79 presented with localized disease, 18 were metastatic at presentation. 88 (91%) were invasive ductal carcinoma (IDC), and 64 (81%) were local disease at presentation and rest were metastatic. Gender spread was 92:5 (F:M). Patients with ER + disease was 84/96, PR + disease was 71, and 4/93 patients had overexpression of HER2. Median age was 70 at diagnosis. 11 patients underwent neoadjuvant chemotherapy, 15 patients underwent adjuvant chemotherapy (AC), and 58/84 patients underwent hormonal adjuvant therapy. For localized disease, median recurrence free survival (RFS) was 165 months (144-NA), and recurrence rate was 8/79 (10%). Recurrence rate for local IDC was 10% (6/64). Patients with metastatic disease at presentation had a median progression free survival (PFS) of 30 months, and progression rate was 7/18 (39%). For patients with metastatic disease, median lines of palliative therapy used was 2, with median duration of first line treatment being 3.5 months, and 10 months for second line. Most common surgical procedure was mastectomy, with 37% of patients undergoing management. Median duration from diagnostic biopsy to definitive surgery was 1 month. Median follow up was 28 months. Most common hormonal adjuvant option was anastrozole (58%), most common AC regimen was docetaxel and cyclophosphamide (39%), and most common first line palliative agent was letrozole (42%). Patients who underwent AC did not reach median OS, and patients who did not receive AC had a median OS of 148 months (p=0.8). Patients with grade 3 tumors had a median OS of 58.6 months, and grade 1 and 2 had a median OS of 148.1 months (p=0.5). Discussion: Current treatment strategies for NEN of breast mirror those of non-NEN of breast with similar histology and stage based on extrapolation of data. Recurrence rate was similar between IDC and SPC. In our cohort, survival was not significantly dependent on grade and use of AC. This might be due to the number of patients included in our study, as there was a non-significant trend towards lower OS in patients with high-grade neoplasms, and further limitations from retrospective design of study. Further research towards benefit of AC in NEN of breast and prognostic value of grading is necessary to explore management options in comparison to non-NEN of the breast. Citation Format: Serhan Unlu, Olisaemeka Ogbue, Gloria Lewis, Abdo Haddad, Hamed Daw, Baidehi Maiti. Real-World Data of Neuroendocrine Neoplasms of Breast [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-11.

Molecular subtypes of neuroendocrine carcinomas: A cross-tissue classification framework based on five transcriptional regulators

Neuroendocrine carcinomas (NECs) are extremely lethal malignancies that can arise at almost any anatomic site. Characterization of NECs is hindered by their rarity and significant inter- and intra-tissue heterogeneity. Herein, through an integrative analysis of over 1,000 NECs originating from 31 various tissues, we reveal theirtissue-independent convergence and further unveil molecular divergence driven by distinct transcriptional regulators. Pan-tissue NECs are therefore categorized into five intrinsic subtypes defined by ASCL1,NEUROD1, HNF4A, POU2F3, and YAP1. A comprehensive portrait of these subtypes is depicted, highlightingsubtype-specific transcriptional programs, genomic alterations, evolution trajectories, therapeutic vulnerabilities, and clinicopathological presentations. Notably, the newly discovered HNF4A-dominated subtype-H exhibits a gastrointestinal-like signature, wild-type RB1, unique neuroendocrine differentiation, poor chemotherapeutic response, and prevalent large-cell morphology. The proposal of uniform classification paradigm illuminates transcriptional basis of NEC heterogeneity and bridges the gap across different lineages and cytomorphological variants, in which context-dependent prevalence of subtypes underlies their phenotypic disparities.

Transformation of adenocarcinoma into small cell lung cancer as one of the mechanisms of acquired resistance to anti-EGFR tyrosine kinase inhibitors

Transformation of adenocarcinoma into small cell lung cancer (SCLC) is a rare and unique biological property of a cancer cell that is responsible for the mechanism of acquired resistance to EGFR tyrosine kinase inhibitors. There are very few clinical observations of phenotypic cellular transformation during metastatic progression of lung cancer in the literature. The aim of the work is to demonstrate clinical observation of phenotypic transformation of metastatic EGFR-mutated adenocarcinoma into small cell lung cancer with neuroendocrine differentiation during therapy with tyrosine kinase inhibitors. Case report. Due to the rarity of this biological phenomenon, we describe our own observation of the transformation of EGFR-mutated metastatic adenocarcinoma into DCLC with neuroendocrine differentiation, which occurred in a 42-year-old woman during treatment with gefitinib. Conclusions. Transformation and changes in cell phenotype during tyrosine kinase inhibitor therapy were the cause of resistance and failure of further treatment with osimertinib in the second line. It was concluded that it is necessary to consider this mechanism of resistance in clinical practice and to perform repeat biopsies during metastatic progression in patients with EGFR-mutated lung adenocarcinoma.

Merkel Cell Carcinoma: Integrating Epidemiology, Immunology, and Therapeutic Updates.

Merkel cell carcinoma (MCC) is a rare skin cancer characterized by neuroendocrine differentiation. Its carcinogenesis is based either on the integration of the Merkel cell polyomavirus or on ultraviolet (UV) mutagenesis, both of which lead to high immunogenicity either through the expression of viral proteins or neoantigens. Despite this immunogenicity resulting from viral or UV-associated carcinogenesis, it exhibits highly aggressive behavior. However, owing to the rarity of MCC and the lack of epidemiologic registries with detailed clinical data, there is some uncertainty regarding the spontaneous course of the disease. Historically, advanced MCC patients were treated with conventional cytotoxic chemotherapy yielding a median response duration of only 3 months. Starting in 2017, four programmed cell death protein 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) immune checkpoint inhibitors-avelumab, pembrolizumab, nivolumab (utilized in both neoadjuvant and adjuvant settings), and retifanlimab-have demonstrated efficacy in treating patients with disseminated MCC on the basis of prospective clinical trials. However, generating clinical evidence for rare cancers, such as MCC, is challenging owing to difficulties in conducting large-scale trials, resulting in small sample sizes and therefore lacking statistical power. Thus, to comprehensively understand the available clinical evidence on various immunotherapy approaches for MCC, we also delve into the epidemiology and immune biology of this cancer. Nevertheless, while randomized studies directly comparing immune checkpoint inhibitors and chemotherapy in MCC are lacking, immunotherapy shows response rates comparable to those previously reported with chemotherapy but with more enduring responses. Notably, adjuvant nivolumab has proven superiority to the standard-of-care therapy (observation) in the adjuvant setting.

A Path to Persistence after EGFR Inhibition.

Residual cancer cells persist even after targeted therapies, serving as a reservoir for the subsequent acquisition of genetic alterations that lead to acquired drug resistance and tumor relapse. These initial drug-tolerant persisters (DTP) are phenotypically heterogenous with transient phenotypes attributed to epigenetic, metabolic, and cell-cycle changes. DTPs are responsible for the inevitable relapse seen in EGFR-mutant non-small cell lung cancer (NSCLC) despite high initial response to tyrosine kinase inhibitor (TKI) treatment. While past in vitro studies identified diverse drivers of drug-tolerant persistence to EGFR TKIs in NSCLC, the resultant phenotypic plasticity is not well understood and in vivo models of persistence are lacking. In this issue of Cancer Research, Hu and colleagues used patient-derived xenograft models of EGFR-mutant lung cancer treated with the third-generation TKI osimertinib to investigate mechanisms of persistence at the time of maximal response. Using bulk and single-cell RNA sequencing, the authors identified a DTP transcriptional cluster mediated by the key neuroendocrine lineage transcription factor ASCL1, which triggers an epithelial-to-mesenchymal transition transcriptional program. ASCL1 overexpression increased osimertinib tolerance in vitro as well, apparently independent of its role in neuroendocrine differentiation. Interestingly, the ability of ASCL1 to induce persistence was context dependent as this occurred only in epigenetically permissive cells. Overall, these findings contribute to our understanding of DTP heterogeneity seen after osimertinib treatment and provide insights into potential therapeutic targets. See related article by Hu et al., p. 1303.

Molecular pathology of small cell lung cancer: Overview from studies on neuroendocrine differentiation regulated by ASCL1 and Notch signaling.

Pulmonary neuroendocrine (NE) cells are rare airway epithelial cells. The balance between Achaete-scute complex homolog 1 (ASCL1) and hairy and enhancer of split 1, one of the target molecules of the Notch signaling pathway, is crucial for NE differentiation. Small cell lung cancer (SCLC) is a highly aggressive lung tumor, characterized by rapid cell proliferation, a high metastatic potential, and the acquisition of resistance to treatment. The subtypes of SCLC are defined by the expression status of NE cell-lineage transcription factors, such as ASCL1, which roles are supported by SRY-box 2, insulinoma-associated protein 1, NK2 homeobox 1, and wingless-related integration site signaling. This network reinforces NE differentiation and may induce the characteristic morphology and chemosensitivity of SCLC. Notch signaling mediates cell-fate decisions, resulting in an NE to non-NE fate switch. The suppression of NE differentiation may change the histological type of SCLC to a non-SCLC morphology. In SCLC with NE differentiation, Notch signaling is typically inactive and genetically or epigenetically regulated. However, Notch signaling may be activated after chemotherapy, and, in concert with Yes-associated protein signaling and RE1-silencing transcription factor, suppresses NE differentiation, producing intratumor heterogeneity and chemoresistance. Accumulated information on the molecular mechanisms of SCLC will contribute to further advances in the control of this recalcitrant cancer.

Spontaneous intersibling polymorphism in the development of dopaminergic neuroendocrine cells in sea urchin larvae: impacts on the expansion of marine benthic species.

The plasticity of the nervous system plays a crucial role in shaping adaptive neural circuits and corresponding animal behaviors. Understanding the mechanisms underlying neural plasticity during development and its implications for animal adaptation constitutes an intriguing area of research. Sea urchin larvae offer a fascinating subject for investigation due to their remarkable evolutionary and ecological diversity, as well as their diverse developmental forms and behavioral patterns. We conducted immunochemical and histochemical analyses of serotonin-containing (5-HT-neurons) and dopamine-containing (DA-positive) neurons to study their developmental dynamics in two sea urchin species: Mesocentrotus nudus and Paracentrotus lividus. Our approach involved detailed visualization of 5-HT- and DA-positive neurons at gastrula-pluteus stages, coupled with behavioral assays to assess larval upward and downward swimming in the water column, with a focus on correlating cell numbers with larval swimming ability. The study reveals a heterochronic polymorphism in the appearance of post-oral DA-positive neuroendocrine cells and confirms the stable differentiation pattern of apical 5-HT neurons in larvae of both species. Notably, larvae of the same age exhibit a two- to four-fold difference in DA neurons. An increased number of DA neurons and application of dopamine positively correlate with larval downward swimming, whereas 5-HT-neurons and serotonin application induce upward swimming. The ratio of 5-HT/DA neurons determines the stage-dependent vertical distribution of larvae within the water column. Consequently, larvae from the same generation with a higher number of DA-positive neurons tend to remain at the bottom compared to those with fewer DA-positive neurons. The proportion of 5-HT and DA neurons within larvae of the same age underlies the different potentials of individuals for upward and downward swimming. A proposed model illustrates how coordination in humoral regulation, based on heterochrony in DA-positive neuroendocrine cell differentiation, influences larval behavior, mitigates competition between siblings, and ensures optimal population expansion. The study explores the evolutionary and ecological implications of these neuroendocrine adaptations in marine species.

Therapeutic Response to PRRNT in a Rare Case of Metastatic Renal Neuroendocrine Carcinoma

AbstractNeuroendocrine tumors (NETs) are a rare spectrum of neoplasms that are characterized by neuroendocrine and neural differentiation. The treatment can be challenging in view of the heterogeneity in differentiation and behavior. Primary renal origin NETs are rare and only a few cases have been reported in the literature. There is limited knowledge on their presentation and response to various lines of treatment. We report a case of a patient with a metastatic renal NET from a rare histological subtype of large cell neuroendocrine carcinoma, known to cause aggressive disease with poor prognosis. A multimodality treatment approach was followed. In spite of surgical management and second-line chemotherapy, the disease progressed. The patient subsequently received peptide receptor radionuclide therapy (PRRNT) using lutetium-177 DOTATATE, following which the patient demonstrated a remarkable clinical and radiological response and is stable to date. In a rare tumor with poor prognosis, the relevance of theranostics and the efficacy of targeted therapies like PRRNT are noteworthy.

Ewing sarcoma of the mandible: A rare case report and literature review.

Ewing sarcoma (ES) usually arises from long bones and affects the head and neck region in only 1%-4% of cases. We reported clinical, radiographic, cytomorphologic, and histomorphologic findings of the ES in the mandible, because of its rarity and radiologically misinterpreted as a parotid gland tumor. A 26-year-old male patient presented with a history of painfull cheek swelling. On magnetic resonance imaging, a mass measuring 50 × 48 × 45 mm was found eroding mandible and pushing back the parotid gland. Aspiration cytology was performed with suspicion of parotid gland tumor. Small, nucleated cells with nuclear indentation, inconspicuous nucleoli, and occasionally rosette-like arrangement were observed. Neuroendocrine immune markers were positive on cell block. It was diagnosed as small round cell neoplasm with neuroendocrine differentiation and biopsy was suggested. The differential diagnosis considered soft tissue and parotid gland tumors. The small round cell tumor morphology was seen on biopsy specimen and immunostaining was applied. The diagnosis for this case was ES of the mandible. ES of the mandible is unusual. Although the histogenesis is still unknown, various cells have been proposed as cells of origin namely, endothelial, hematopoietic, fibroblastic, mesenchymal stem cells or neural derived mesenchymal stem cells. Small cell morphology, CD99, CD56, neuron specific enolase, and synaptophysin expressions confirmed the diagnosis of ES. The differentiation of the ES from other small cell tumors may be difficult and requires awareness for histological and immunohistochemical features. It should be kept in mind that the diagnosis can be challenging due to uncommon locations and radiological misinterpreted.

Gastric Carcinoma in Autoimmune Gastritis: A Histopathologic and Molecular Study

Patients with autoimmune gastritis (AIG) have a 13-fold risk of developing type-1 neuroendocrine tumors, whereas the risk for gastric adenocarcinoma is still uncertain. Here we describe the clinicopathologic and molecular features of a series of gastric carcinomas (GC) arising in the context of AIG. A total of 26 AIG-associated GC specimens were collected from 4 Italian Institutions. Immunohistochemistry for MUC1, MUC2, MUC5AC, MUC6, CDX2, HER2, PD-L1, CLDN18, mismatch repair (MMR) proteins, and p53 and EBV-encoded RNA (EBER) in situ hybridization were performed. Histologic and immunohistochemical features were jointly reviewed by 5 expert gastrointestinal pathologists. Next-generation sequencing analysis (TrueSight Oncology 500, Illumina) of 523 cancer-related genes was performed on 19 cases. Most tumors were diagnosed as pT1 (52%) and they were located in the corpus/fundus (58%) and associated with operative link for gastritis assessment stage II gastritis (80.8%), absence of parietal cells, complete intestinal metaplasia, and enterochromaffin-like-cell micronodular hyperplasia. Only 4 (15.4%) GCs were diagnosed during follow-up for AIG. The following histotypes were identified: 20 (77%) adenocarcinomas; 3 (11%) mixed neuroendocrine–non-neuroendocrine neoplasms, and 2 (8%) high-grade solid adenocarcinomas with focal neuroendocrine component, 1 (4%) adenocarcinoma with an amphicrine component. Overall, 7 cases (27%) showed MMR deficiency, 3 (12%) were positive (score 3+) for HER2, 6 (23%) were CLDN18 positive, and 11 (42%) had PD-L1 combined positive score ≥ 10. EBER was negative in all cases. Molecular analysis revealed 5/19 (26%) microsatellite instability (MSI) cases and 7 (37%) tumor mutational burden (TMB) high. The most frequently altered genes were TP53 (8/19, 42%), RNF43 (7/19, 37%), ERBB2 (7/19, 37% [2 amplified and 5 mutated cases]), ARID1A (6/19, 32%), and PIK3CA (4/19, 21%). In summary, AIG-associated GCs are often diagnosed at low stage in patients with longstanding misrecognized severe AIG; they often display a neuroendocrine component or differentiation, have relatively higher rates of MMR deficiency, and TMB high.

Abstract LB217: Novel organoid models of lineage plasticity in castration resistant prostate cancer

Abstract The development of next-generation AR-targeted drugs, such as abiraterone and enzalutamide, has improved survival of patients with castration-resistant prostate cancer (CRPC). However, many patients eventually progress to therapy-resistant lethal prostate cancer. CRPC exhibits variant cellular states, including AR-pathway active prostate cancer (ARPC), AR activity-low prostate cancer (ARLPC), neuroendocrine prostate cancer (NEPC), amphicrine prostate cancer co-expressing AR and neuroendocrine genes (AMPC), and double-negative prostate cancer (DNPC) lacking both AR expression and neuroendocrine differentiation, indicating that lineage plasticity facilitates therapeutic resistance. While molecular characteristics of ARPC and NEPC are well described, other common forms of CRPC, such as DNPC which occurs in 20-25% of CRPC patients, remain poorly understood. Therefore, characterization of pre-clinical models of DNPC and identification of novel regulators of lineage plasticity in DNPC are urgent necessities for the development of effective treatment for lethal prostate cancer.In our studies, we have generated a new mouse model of CRPC in which Pten and Smad4 are deleted in distal luminal cells upon tamoxifen administration (Nkx3.1CreERT2/+; Ptenfl/fl; Smad4fl/fl; R26R-eYFP/+, NPS). We observed a molecular transition from ARPC to ARLPC and DNPC in the prostate tumors derived from NPS mice during tumor progression. Moreover, a combination of castration and enzalutamide treatment promoted a partial epithelial-mesenchymal transition (EMT) in DNPC. To identify the evolutionary trajectories of cancer progression and drivers of lineage plasticity in CRPC, we have established organoid lines from the prostate tumor cells of NPS mice. Single-cell RNA-sequencing (scRNA-seq) and marker validation analyses shown that these organoid lines display overt lineage plasticity, corresponding to ARPC, ARLPC, partial EMT-absent DNPC, and partial EMT-present DNPC. Orthotopic grafts derived from the established NPS organoid lines show consistent molecular phenotypes and confirm that AR-targeted therapies facilitate partial EMT in vivo. Furthermore, cross-species bioinformatic analyses using scRNA-seq datasets indicate that the established NPS organoid lines partially recapitulate the spectrum of lineage plasticity in human CRPC.In summary, we have established prostate cancer organoid lines from a novel mouse model of CRPC, which not only provide large and reproducible sources of two distinct forms of DNPC (partial EMT-absent DNPC and partial EMT-present DNPC) for molecular analyses, but also can capture the regulatory complexity of lineage plasticity in human CRPC. Therefore, NPS mice provide an excellent pre-clinical model of CRPC, especially DNPC, to identify novel regulators that drive lineage plasticity and to pursue assays for development of candidate drugs that can inhibit or even possibly convert therapy-resistant forms of CRPC to therapy-sensitive ones. Citation Format: Jinqiu Lu, Michael M. Shen. Novel organoid models of lineage plasticity in castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB217.

Protein kinase D2-Aurora kinase A-ERK1/2 signalling axis drives neuroendocrine differentiation of epithelial ovarian cancer.

Epithelial ovarian cancer (EOC) is deadliest gynecological malignancy with poor prognosis and patient survival. Despite development of several therapeutic interventions such as poly-ADP ribose polymerase (PARP) inhibitors, EOC remains unmanageable and discovery of novel early detection biomarkers and treatment targets are highly warranted. Although neuroendocrine differentiation (NED) is implicated in different human cancers including prostate adenocarcinoma and lung cancer, mechanistic studies concerning NED of epithelial ovarian cancer are lacking. We report that Aurora kinase A drives NED of epithelial ovarian cancer in an ERK1/2-dependent manner and pharmacological and genetic inhibition of Aurora kinase A suppress NED of ovarian cancer. Moreover, we demonstrate that protein kinase D2 positively regulated Aurora kinase A to drive NED. Overexpression of catalytically active PKD2 drives NED and collectively, PKD2 cross talks with Aurora kinase A/ERK1/2 signalling axis to positively regulate NED of EOC. PKD2/Aurora kinase A/ERK1/2 signalling axis is a novel therapeutic target against neuroendocrine differentiated EOC.

Combined therapy targeting AR and EZH2 curbs castration-resistant prostate cancer enhancing anti-tumor T-cell response.

Aim: Castration-resistant prostate cancer (CRPC) eventually becomes resistant to androgen receptor pathway inhibitors like enzalutamide. Immunotherapy also fails in CRPC. We propose a new approach to simultaneously revert enzalutamide resistance and rewire anti-tumor immunity. Methods: We investigated in vitro and in subcutaneous and spontaneous mouse models the effects of combining enzalutamide and GSK-126, a drug inhibiting the epigenetic modulator EZH2. Results: Enzalutamide and GSK-126 synergized to reduce CRPC growth, also restraining tumor neuroendocrine differentiation. The anti-tumor activity was lost in immunodeficient mice. Indeed, the combination treatment awoke cytotoxic activity and IFN-γ production of tumor-specific CD8+ T lymphocytes. Conclusion: These results promote the combination of enzalutamide and GSK-126 in CRPC, also offering new avenues for immunotherapy in prostate cancer.

Роль определения хромогранина А в лечении больных кастрационно-резистентным раком предстательной железы.

Introduction. Chromogranin A has the greatest diagnostic value in detecting neuroendocrine differentiation (NED) of a tumor. This work is devoted to the study of the therapy of castration-resistant prostate cancer (CRPC) using somatostatin (AS) analogues based on the assessment of the neuroendocrine status of the tumor. Material and methods. The study included 89 patients with CRPC aged 72.2±1.4 years. Localized prostate cancer was diagnosed in 6 (6.7%), locally distributed prostate cancer (T3-4N0M0) in 12 (13.5%) patients, metastatic (T3-4N0-1M1)–in 71 (79.8%). An increase in CgA was observed in 31.5% (n=28) of CRPC patients. Combination therapy was performed with Octreotide depot (Pharm–Sintez, Russia) according to the scheme: 20 mg n/a once every 28 days in combination with dexamethasone at a dose of 4 mg per day for 1 month. Then the dose of dexamethasone was reduced. Patients were monitored every 28 days. The effectiveness was evaluated by the dynamics of PSA and CgA, as well as (ultrasound, abdominal MSCT, pelvic MRI and osteoscintigraphy). According to PSA, the answer was considered to be a decrease in the median PSA, or a lack of growth of more than 10%. Results. In patients with normal levels of CgA after 3 months of treatment, the median PSA significantly increased: from 57.0 [29.8; 94] ng/ml initially to 89.0 [47.4; 131.9] ng/ml, which was 56.1%, the decrease in CgA was 9.5% (from 2.1 to 1.9 nmol/l). In patients with elevated levels of CgA, there was a decrease in the median PSA value by 35.7%, from 169.5 [66.3; 235.3] ng/ml to 109.0 [44.8; 236.9] and CgA by 25% – from 5.2 [3.6; 7.1] to 3.9 [2.3; 5.2]. The median values and the proportion of PSA reduction in the group of «responders» stratified by CgA levels before and after 3 months of treatment were, respectively: in the group with normal CgA values – 43.0 [16.5; 154.3] nmol/l and 15.2 [7.2; 48.8] nmol/l or 64.7%; with CgA 3-7 nmol/l – 160.5 [35.1; 278.6] nmol/l and 42.4 [14.1; 88.4] nmol/l or 73.6%; in patients with CgA more than 7 nmol/L – 166.5 [28.0; 222.0] nmol/l and 81.7 [16.4; 151.0] nmol/l or 50.9%. Conclusion. Early detection of NED in CRPC with the use of the CgA marker makes it possible to stratify patients according to its severity and off r combination therapy with the inclusion of AS. An analysis of the immediate results of treatment with octreotide depot in combination with GnRH agonists and dexamethasone showed significantly higher efficacy in patients with initially increased levels of CgA, and the results achieved look preferable in patients with a moderate increase in this marker (within 3-7 nmol/l).

Abstract 4864: Epidemiological characteristics and treatment strategies of gastric cancer with neuroendocrine differentiation (NED)

Abstract Background: Gastric cancer with neuroendocrine differentiation (NED) occurs in 10% to 40% of cases, a significant proportion that is under-researched. The lack of clinical guidelines for this subgroup necessitates the development of effective treatment protocols. Methods: This study enrolled 149 gastric cancer patients, analyzing retained surgical wax blocks via immunohistochemistry for syn, CgA, and CD56 expressions. Patients were categorized into NED-positive and NED-negative groups for analysis, employing continuous variable analysis, categorical variable analysis, clustering, principal component analysis (PCA), feature importance analysis, heatmap analysis, and survival prognosis. Moreover, the clinical efficacy and safety of first-line (surufatinib + SOX + anti PD-1 antibody, n=3) and second-line (surufatinib + anti PD-1 antibody, n=3) treatments were observed in six advanced gastric cancer with NED patients, exploring the epidemiological characteristics, feasibility, and importance of clinical treatments for NED. Results: The study revealed a 10.1% incidence of NED positivity in gastric cancer patients. NED-positive patients exhibited a rapid decline in early survival probability, with a median relapse-free survival of 32.4 months compared to 41.5 months in NED-negative patients, indicating a poorer prognosis for NED-positive patients. In-depth analysis suggested significant correlations between NED status and factors such as gender, tumor location, pathological type, and AJCC staging, with the most significant associations observed in males, stage IIIA, and gastric angle location. In the six advanced gastric cancer with NED cases, effective tumor reduction was observed in both first-line (100% tumor shrinkage rate, ORR 66.7%, DCR 100%) and second-line treatments (66.7% tumor shrinkage rate, ORR 33.3%, DCR 100%), showing sustained partial responses (PR) exceeding 10 months in two patients and 7 months in one patient, respectively. The major grade 3 or higher TEAEs being neutropenia and thrombocytopenia in the first-line, and hypertension and proteinuria in the second-line therapy. Conclusion: This study provides pivotal epidemiological and clinical treatment evidence for gastric cancer with NED, underscoring the necessity of personalized treatment strategies for this subgroup. Future research should focus on refining treatment protocols to enhance the quality of life and overall prognosis for these patients. Citation Format: Zhen Huang, Jinlai Wei, Yifan Shen, Jun Zhang. Epidemiological characteristics and treatment strategies of gastric cancer with neuroendocrine differentiation (NED) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4864.