Medical Management of Gastroenteropancreatic Neuroendocrine Tumors: Current Strategies and Future Advances

ALKBH5 enhances lipid metabolism reprogramming by increasing stability of FABP5 to promote pancreatic neuroendocrine neoplasms progression in an m6A-IGF2BP2-dependent manner

The process of post-transcriptional regulation has been recognized to be significantly impacted by the presence of N6-methyladenosine (m6A) modification. As an m6A demethylase, ALKBH5 has been shown to contribute to the progression of different cancers by increasing expression of several oncogenes. Hence, a better understanding of the key targets of ALKBH5 in cancer cells could potentially lead to the development of new therapeutic targets. However, the specific role of ALKBH5 in pancreatic neuroendocrine neoplasms (pNENs) remains largely unknown. Here, we demonstrated that ALKBH5 was up-regulated in pNENs and played a critical role in tumor growth and lipid metabolism. Mechanistically, ALKBH5 over-expression was found to increase the expression of FABP5 in an m6A-IGF2BP2 dependent manner, leading to disorders in lipid metabolism. Additionally, ALKBH5 was found to activate PI3K/Akt/mTOR signaling pathway, resulting in enhanced lipid metabolism and proliferation abilities. In conclusion, our study uncovers the ALKBH5/IGF2BP2/FABP5/mTOR axis as a mechanism for aberrant m6A modification in lipid metabolism and highlights a new molecular basis for the development of therapeutic strategies for pNENs treatment.

Immunological role and prognostic value of somatostatin receptor family members in colon adenocarcinoma

Colon adenocarcinoma (COAD) is among the most prevalent cancers worldwide, ranking as the third most prevalent malignancy in incidence and mortality. The somatostatin receptor (SSTR) family comprises G-protein-coupled receptors (GPCRs), which couple to inhibitory G proteins (Gi and Go) upon binding to somatostatin (SST) analogs. GPCRs are involved in hormone release, neurotransmission, cell growth inhibition, and cancer suppression. However, their roles in COAD remain unclear. This study used bioinformatics to investigate the expression, prognosis, gene alterations, functional enrichment, and immunoregulatory effects of the SSTR family members in COAD. SSTR1-4 are differentially downregulated in COAD, and low SSTR2 expression indicates poor survival. Biological processes and gene expression enrichment of the SSTR family in COAD were further analyzed using the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology. A strong correlation was observed between SSTR expression and immune cell infiltration. We also quantified SSTR2 expression in 25 COAD samples and adjacent normal tissues using quantitative real-time polymerase chain reaction. We analyzed its correlation with the dendritic cell-integrin subunit alpha X marker gene. The biomarker exploration of the solid tumors portal was used to confirm the correlation between SSTR2 with immunomodulators and immunotherapy responses. Our results identify SSTR2 as a promising target for COAD immunotherapy. Our findings provide new insights into the biological functions of the SSTR family and their implications for the prognosis of COAD.

PDZ-binding kinase aggravates pancreatic neuroendocrine neoplasm progression by activating the AKT/mTOR pathway

The therapeutic effects of existing drug regimens against pancreatic neuroendocrine neoplasms (pNENs) remain limited, and identifying ideal therapeutic targets is warranted. PDZ binding kinase (PBK) may play an oncogenic role in most solid tumors. However, its function in pNEN remains unclear. In this study, pNEN samples and International Cancer Genome Consortium data were used to determine the clinical significance of PBK. Cell counting and CCK8 assays were used to assess cell proliferation. Flow cytometry was used to assess drug-induced apoptosis and cell cycle arrest. An in vivo PBK-targeting experiment was performed in mice bearing pNENs. Western blotting, quantitative PCR, and immunohistochemistry were performed to assess the molecular mechanisms. PBK was significantly upregulated in pNEN tissues compared with paracancerous tissues. Additionally, PBK was a poor prognostic factor for pNEN patients. PBK was found to promote the proliferation of pNEN cells by activating the AKT/mTOR pathway. Furthermore, PBK inhibition combined with everolimus treatment had enhanced antitumour effects on pNEN via inhibiting AKT/mTOR pathway and inducing G0/G1 phase cell cycle arrest. This study highlights that PBK plays an oncogenic role in and is a promising therapeutic target for pNEN.

Capecitabine and temozolomide (CAPTEM) is effective in metastatic well-differentiated gastrointestinal neuroendocrine tumors

OBJECTIVE

The aim of this study was to investigate the outcomes and prognostic factors of patients with metastatic gastrointestinal neuroendocrine tumor (mGI-NET) who were treated with capecitabine and temozolomide (CAPTEM) and somatostatin receptor ligand (octreotide or lanreotide).

METHODS

Clinicopathological characteristics and treatment outcomes of 43 patients with mGI-NET were retrospectively evaluated. Overall survival (OS) and progression-free survival (PFS) were evaluated using Kaplan-Meier curve. Cox-regression analysis was used to assess prognostic variables.

RESULTS

There were 23 (53.5%) men and 20 women (46.5%) with a median age of 59 years (range 27-85 y). Patients were given octreotide (86.0%) or lanreotide (14.0%) with CAPTEM. In patients with well-differentiated mGI-NET, median PFS was 17.4 months, and the disease control rate was 71.1%. Patients with poorly differentiated mGI-NET showed no response, and the median PFS was 4.5 months. Four (9.3%) discontinued the medication due to toxicity. Anemia (37.2%), thrombocytopenia (25.6%), and fatigue (16.3%) were the most prevalent adverse events. The 5-year OS rate was 61.0% in all patients during a median follow-up of 33.8 months. In multivariate analysis, age (P = 0.014) and tumor differentiation (P < 0.001) were statistically significant factors for OS.

CONCLUSIONS

CAPTEM plus somatostatin receptor ligands were efficacious and well tolerated in individuals with well-differentiated mGI-NET. However, it was ineffective for those with poorly differentiated tumors. Age of 60 years or elder and poorly differentiated tumors were related to a poor patient prognosis.

Combined use of 177 Lu-DOTATATE peptide receptor radionuclide therapy and fluzoparib for treatment of well-differentiated neuroendocrine tumors: A preclinical study

Peptide receptor radionuclide therapy (¹⁷⁷ Lu-DOTATATE) causes DNA strand breaks and has been validated for well-differentiated neuroendocrine tumor treatment. Poly-(ADP-ribose)-polymerase inhibitors have also been used for malignant tumors with deficient DNA repair. We aimed to determine whether the poly-(ADP-ribose)-polymerase inhibitor fluzoparib could enhance the anti-tumor effects of ¹⁷⁷ Lu-DOTATATE in neuroendocrine tumor cells and xenografts. The neuroendocrine characteristics of NCI-H727 bronchial carcinoid cells were evaluated by immunofluorescence staining. The synergistic effects of fluzoparib and ¹⁷⁷ Lu-DOTATATE were evaluated by cell proliferation and flow cytometry assays. Tumor response and the side effects of combination therapy were also assessed in xenograft mice treated with ⁷⁷ Lu-DOTATATE and fluzoparib alone or in combination. Somatostatin receptors were specifically expressed in NCI-H727 cells and tumor xenografts. ¹⁷⁷ Lu-DOTATATE (22.20 MBq mL^-1 ) and fluzoparib (50 µm) inhibited cell proliferation by 16.6% and 35.6%, respectively, compared to 73.2% in cells treated with their combination. Tumor cell proliferation was significantly suppressed by ¹⁷⁷ Lu-DOTATATE (22.20 MBq mL^-1 , 4.4-fold) and fluzoparib (50 µm, 2.1-fold). ¹⁷⁷ Lu-DOTATATE caused cell cycle arrest mainly at G1 phase, whereas fluzoparib caused arrest at G2/M phase, and combined treatment with both agents caused cell cycle arrest at G1 phase, similar to ¹⁷⁷ Lu-DOTATATE alone. The volume of tumor xenografts was reduced by 18.6% in mice receiving combined treatment, compared to 4.9% and 11.4% in mice treated with ¹⁷⁷ Lu-DOTATATE or fluzoparib alone. Fluzoparib can potentiate the anti-tumor effect of ¹⁷⁷ Lu-DOTATATE in NCI-H727 cells in a synergistic manner by arresting the cell cycle at G1 phase. Further preclinical and clinical studies are warranted to validate these findings.

Predictive Factors for Resistant Disease with Medical/Radiologic/Liver-Directed Anti-Tumor Treatments in Patients with Advanced Pancreatic Neuroendocrine Neoplasms: Recent Advances and Controversies

Simple Summary

Tumor resistance, both primary and acquired, is leading to increased complexity in the nonsurgical treatment of patients with advanced panNENs, which would be greatly helped by reliable prognostic/predictive factors. The importance in identifying resistance is being contributed to by the increased array of possible treatments available for treating resistant advanced disease; the variable clinical course as well as response to any given treatment approach of patients within one staging or grading system, the advances in imaging which are providing increasing promising results/parameters that correlate with grading/outcome/resistance, the increased understanding of the molecular pathogenesis providing promising prognostic markers, all of which can contribute to selecting the best treatment to overcome resistance disease. Several factors have been identified that have prognostic/predictive value for identifying development resistant disease and affecting overall survival (OS)/PFS with various nonsurgical treatments of patients with advanced panNENs. Prognostic factors identified for patients with advanced panNENs for both OS/PFSs include various clinically-related factors (clinical, laboratory/biological markers, imaging, treatment-related factors), pathological factors (histological, classification, grading) and molecular factors. Particularly important prognostic factors for the different treatment modalities studies are the recent grading systems. Most prognostic factors for each treatment modality for OS/PFS are not specific for a given treatment option. These advances have generated several controversies and new unanswered questions, particularly those related to their possible role in predicting the possible sequence of different anti-tumor treatments in patients with different presentations. Each of these areas is reviewed in this paper.

Abstract

Purpose: Recent advances in the diagnosis, management and nonsurgical treatment of patients with advanced pancreatic neuroendocrine neoplasms (panNENs) have led to an emerging need for sensitive and useful prognostic factors for predicting responses/survival. Areas covered: The predictive value of a number of reported prognostic factors including clinically-related factors (clinical/laboratory/imaging/treatment-related factors), pathological factors (histological/classification/grading), and molecular factors, on therapeutic outcomes of anti-tumor medical therapies with molecular targeting agents (everolimus/sunitinib/somatostatin analogues), chemotherapy, radiological therapy with peptide receptor radionuclide therapy, or liver-directed therapies (embolization/chemoembolization/radio-embolization (SIRTs)) are reviewed. Recent findings in each of these areas, as well as remaining controversies and uncertainties, are discussed in detail, particularly from the viewpoint of treatment sequencing. Conclusions: The recent increase in the number of available therapeutic agents for the nonsurgical treatment of patients with advanced panNENs have raised the importance of prognostic factors predictive for therapeutic outcomes of each treatment option. The establishment of sensitive and useful prognostic markers will have a significant impact on optimal treatment selection, as well as in tailoring the therapeutic sequence, and for maximizing the survival benefit of each individual patient. In the paper, the progress in this area, as well as the controversies/uncertainties, are reviewed.

Clinical and Molecular Characteristics of Rare Malignant Tumors of Colon and Rectum

Simple Summary

Tumors of colon and rectum other than adenocarcinomas represent a neglected issue from clinical and laboratory points of view because of their rarity. In this review, we summarize and describe the rare histologic entities occurring in colon and rectum. Clinical and pathologic characteristics, prognostic behavior, treatments, and altered genes are reported to provide readers with a paramount and comparative perspective. In relation to this, we propose that improvements in registries and multidisciplinary research are warranted to ameliorate their management.

Abstract

The most frequent form of colorectal cancer is represented by adenocarcinoma being about 98% of tumor histological types. However, other rare histotypes can be found in colon and rectum (adenosquamous, goblet cell adenocarcinoma, lymphoma, medullary carcinoma, melanoma, mesenchymal, neuroendocrine, plasmacytoma, signet ring, squamous tumors). Altogether, these forms account for less than 2% of colorectal tumors. There are no specific diagnostic or therapeutic recommended approaches and most of the information available from literature derives from small and retrospective clinical series. In the present study, we provide a paramount and updated view on clinical and biologic characteristics of rare colorectal tumors.

The evolution of PRRT for the treatment of neuroendocrine tumors; What comes next?

Lu-177 has been developed for the treatment of patients with peptide receptor radionuclide therapy (PRRT). A second generation pure no-carrier-added Lu-177 has a high specific activity and has waste disposal advantages over the first generation carrier-added Lu-177. PRRT has recently been developed for the treatment of neuroendocrine tumors (NETs). The majority of pancreatic and gastroenteric NETs (GEP-NETs) express the somatostatin receptors (SSTRs) 2 and 5. These receptors can be specifically targeted with a somatostatin peptide analogue (DOTATOC/DOTATATE) which can be chelated to a positron emission tomography (PET) emitting radioisotope such as Ga-68 for imaging or to a β-emitting radioisotope Lu-177 for therapy. A key advantage of this approach is that the receptor expression can be demonstrated by PET imaging before the patient is treated. Clinical studies in G1 and G2 GEP-NETS have demonstrated that PRRT is extremely effective in terms of progression free survival (PFS), symptom control and quality of life, with a well-established safety profile. A beneficial effect on outcome survival awaits to be confirmed. The first commercially available product Lu-177-DOTATATE was approved following the NETTER-1 trial in G1 and G2 GE-NETS. Lu-177-DOTATATE 7,4 GBq every 8 weeks for 4 cycles, together with octreotide LAR 30 mg monthly, demonstrated a median PFS of 28,4 months compared to 8,5 months for octreotide LAR 60 mg monthly. A second pivotal study COMPETE is currently in progress, comparing no carrier-added (n.c.a.) Lu-177-DOTATOC to the m-TOR inhibitor Everolimus in both GE-NETs and PNETs. Two studies, NETTER-2 and COMPOSE are currently underway in patients with high grade G2 and G3 NETs. Novel SSTR antagonists are being developed as next generation targeting molecules for SSTR2-expressing tumors. Antagonists have a higher tumor binding to receptors than agonists, opening up the potential indications for SSTR2 targeting to tumors which have a relatively lower expression of SSTR2 compared to NET such as small cell lung cancer, hepatocellular carcinoma and breast cancer. In addition to Lu-177, radioisotopes with different radiation properties such as Tb-161 and the α-emitter Ac-225 are being developed which have the potential to improve treatment efficacy across the range of G1 to G3 NETs.

The overriding role of surgery and tumor grade for long-term survival in patients with gastroenteropancreatic neuroendocrine neoplasms: A population-based cohort study

Background

Gastroenteropancreatic neuroendocrine neoplasms (GEP‐NENs) comprise a heterogeneous disease group. Factors that affect long‐term survival remain uncertain. Complete population‐representative cohorts with long‐term follow‐up are scarce.

Aim

To evaluate factors of importance for the long‐term survival.

Methods and results

An Observational population‐based study on consecutive GEP‐NEN patients diagnosed from 2003 to 2013, managed according to national guidelines. Univariable and multivariable survival analyses were performed to evaluate overall survival (OS) and to identify independent prognostic factors. One hundred ninety eligible patients (males, 58.9%) (median age, 60.0 years; range, 10.0–94.2 years) were included. The small bowel, appendix, and pancreas were the most common tumor locations. The World Health Organization (WHO) tumor grade 1–3 distributions varied according to the primary location and disease stage. Primary surgery with curative intent was performed in 66% of the patients. The median OS of the study population was 183 months with 5‐ and 10‐year OS rates of 66% and 57%, respectively. Only age, WHO tumor grade, and primary surgical treatment were independent prognostic factors for OS.

Conclusion

The outcomes of GEP‐NEN patients are related to several factors including age and primary surgical treatment. WHO tumor grading, based on the established criteria, should be routine in clinical practice. This may improve clinical decision‐making and allow the comparison of outcomes among different centers.

Neuroendocrine neoplasia of the gastrointestinal tract revisited: towards precision medicine

Over the past 5 years, a number of notable research advances have been made in the field of neuroendocrine cancer, specifically with regard to neuroendocrine cancer of the gastrointestinal tract. The aim of this Review is to provide an update on current knowledge that has proven effective for the clinical management of patients with these tumours. For example, for the first time in the tubular gastrointestinal tract, well-differentiated high-grade (grade 3) tumours and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) are defined in the WHO classification. This novel classification enables efficient identification of the most aggressive well-differentiated neuroendocrine tumours and helps in defining the degree of aggressiveness of MiNENs. The Review also discusses updates to epidemiology, cell biology (including vesicle-specific components) and the as-yet-unresolved complex genetic background that varies according to site and differentiation status. The Review summarizes novel diagnostic instruments, including molecules associated with the secretory machinery, novel radiological approaches (including pattern recognition techniques), novel PET tracers and liquid biopsy combined with DNA or RNA assays. Surgery remains the treatment mainstay; however, peptide receptor radionuclide therapy with novel radioligands and new emerging medical therapies (including vaccination and immunotherapy) are evolving and being tested in clinical trials, which are summarized and critically reviewed here.

Influence of pretreatment with everolimus or sunitinib on the subacute hematotoxicity of 177Lu-DOTATATE PRRT

Background: Peptide receptor radionuclide therapy (PRRT) is a validated treatment for somatostatin receptor overexpressing neuroendocrine tumors (NETs). The NETTER-1 trial demonstrated a pronounced positive effect on progression-free-survival compared to high dose somatostatin analogs (SSAs), with a strong tendency toward overall survival benefit. Our aim was to investigate the influence of pretreatment with everolimus and/or sunitinib on subacute hematotoxicity of PRRT. To assess the influence of prior treatment with everolimus/sunitinib might be of clinical relevance due to the link between short-term hematotoxicity and increased incidence of late hematotoxicity.Material and methods: Our single-center retrospective study enrolled all patients treated with ¹⁷⁷Lu-DOTATATE PRRT (1-4 cycles of 7.4 GBq), between November 2013 and July 2018. Patients were assigned to two groups according to their pretreatment: no targeted agents (N = 41), or targeted agents (everolimus, sunitinib or both; N = 41). The end point was subacute hematotoxicity, defined as the nadir value between the first administration until 3 months after the last administration, using the CTCAE 4.03 classification. The impact of splenectomy was also explored.Results: Eighty percent of patients had a primary gastroenteropancreatic NET. No statistically significant differences in severe subacute hematotoxicity were seen in the pretreated group vs. the naive group for hemoglobin (grade 3/4: 12% vs. 22%), neither for leucocytes (grade 3/4: 10% vs. 7%), neutrophils (grade 3/4: 5% vs. 7%), lymphocytes (grade 3/4: 49% vs. 37%) and platelets (grade 3/4: 15% vs. 15%). Furthermore, we observed significantly lower toxicity for total white blood cells, lymphocytes and platelets in the subgroup that had splenectomy (N = 12). Limitations of this study include the potential bias in lack of use of targeted agents in patients more susceptible to toxicity, and the limited number of patients and events.Conclusions: In a patient cohort with NET pretreated with everolimus and/or sunitinib, we could not demonstrate a significant effect of prior/pretreatment with everolimus and/or sunitinib on the subacute hematotoxicity of ¹⁷⁷Lu-DOTATATE PRRT.

Clinical Characteristics and Management of Functional Pancreatic Neuroendocrine Neoplasms: A Single Institution 20-Year Experience with 286 Patients

BACKGROUND

Functional pancreatic neuroendocrine neoplasms (PanNENs) are very rare disorders but have complex spectrum, including insulinoma, gastrinoma, glucagonoma, somatostatinoma, and VIPoma. Patients with PanNENs usually present with characteristic symptoms caused by corresponding hormone hypersecretion. It has always been challenging in dealing with such rare but complicated disorders. In this report, we analyzed the clinical characteristics of functional PanNENs in a large cohort of Chinese patients and summarized our clinical experience in diagnosis and treatment.

METHODS

The retrospective analysis was performed in patients with a definite diagnosis of functional PanNENs hospitalized in Chinese PLA General Hospital between 2000 and 2020. The clinical characteristics, surgical information, and pathological findings were extracted from their medical records and were analyzed.

RESULTS

Totally, 286 patients (gender: male 103 and female 183; age: 45.55 ± 15.23 years old) were diagnosed with definite functional PanNENs. The most frequent functional PanNENs were insulinoma (266/286) followed by glucagonoma (10/286), somatostatinoma (3/286), adrenocorticotropic hormone- (ACTH-) producing tumor (3/286), gastrinoma (2/286), and VIPoma (2/286). Nine patients were diagnosed with multiple endocrine neoplasia type 1 (MEN1) in which all the associated functional PanNENs were insulinomas. The duration from symptoms' onset to confirmed diagnosis was 3.67 ± 4.28 years. Two hundred and eighty patients with tumor localized in pancreatic or with limited metastasis underwent surgery. The symptoms associated with hormonal oversecretion were improved significantly after surgery. Five patients with unresectable metastases or tumor recurrence after surgery were administrated with systemic chemotherapy or other targeted therapies. With these various therapies, the symptoms were also partially relieved. According to findings in pathological and immunochemical examination, all the functional PanNENs were categorized into NEN-G1 (41.95%), NEN-G2 (54.90%), NEN-G3 (3.15%), and NEC-G3 (0%).

CONCLUSION

Patients with suspected functional PanNENs should have a systematic endocrine examination at diagnosis. Multidisciplinary collaborations are essential for precise diagnosis and tumor localization. A successful surgery or other targeted therapies can improve the prognosis of patients with such rare but complex disorders.

New and emerging systemic therapy options for well-differentiated gastroenteropancreatic neuroendocrine tumors

Introduction: Well-differentiated gastroenteropancreatic (GEP) neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms with a wide range of clinical behavior. Multiple treatment modalities exist, including novel and emerging systemic options, and an understanding of the advantages and disadvantages of each is imperative for optimizing the outcomes of patients with GEP-NETs.Areas covered: While surgical resection remains the preferred treatment for localized well-differentiated GEP-NETs, treatment of unresectable disease depends on its extent, location, and distribution as well as underlying aspects of tumor biology. Isolated hepatic metastases can be successfully treated with liver-directed therapies such as hepatic arterial based therapies or ablation. Diffuse metastatic disease often requires systemic treatments such as molecular-targeted therapeutics, peptide receptor radionuclide therapy (PRRT), or traditional chemotherapy. Somatostatin analogs are often the primary treatment option capable of simultaneously inhibiting hormone production and slowing tumor growth.Expert opinion: Recent advances in systemic treatment options for advanced well-differentiated GEP-NETs have emerged due to an improved understanding of the molecular mechanisms responsible for tumor development and progression. Future research is needed to determine the optimal indications for and sequencing of these novel therapies.