PPoma Review: Epidemiology, Aetiopathogenesis, Prognosis and Treatment

Unraveling the mysteries of MGMT: Implications for neuroendocrine tumors

Neuroendocrine tumors (NETs) are a diverse group of tumors that arise from neuroendocrine cells and are commonly found in various organs. A considerable proportion of NET patients were diagnosed at an advanced or metastatic stage. Alkylating agents are the primary treatment for NET, and O6-methylguanine methyltransferase (MGMT) remains the first-line of defense against DNA damage caused by these agents. Clinical trials have indicated that MGMT promoter methylation or its low/lacked expression can predict a favorable outcome with Temozolomide in NETs. Its status could help select NET patients who can benefit from alkylating agents. Therefore, MGMT status serves as a biomarker to guide decisions on the efficacy of Temozolomide as a personalized treatment option. Additionally, delving into the regulatory mechanisms of MGMT status can lead to the development of MGMT-targeted therapies, benefiting individuals with high levels of MGMT expression. This review aims to explore the polymorphism of MGMT regulation and summarize its clinical implications in NETs, which would help establish the role of MGMT as a biomarker and its potential as a therapeutic target in NETs. Additionally, we explore the benefits of combining Temozolomide and immunotherapy in MGMT hypermethylated subgroups. Future studies can focus on optimizing Temozolomide administration to induce specific immunomodulatory changes.

Relation between WHO Classification and Location- and Functionality-Based Classifications of Neuroendocrine Neoplasms of the Digestive Tract

Practice of neuroendocrine neoplasms (NENs) of the digestive tract, which comprise of a highly diverse group of tumors with a rising incidence, faces multiple biological, diagnostic, and therapeutic issues. Part of these issues is due to misuse and misinterpretation of the classification and terminology of NENs of the digestive tract, which make it increasingly challenging to evaluate and compare the literature. For instance, grade 3 neuroendocrine tumors (NETs) are frequently referred to as neuroendocrine carcinomas (NECs) and vice versa, while NECs are, by definition, high grade and therefore constitute a separate entity from NETs. Moreover, the term NET is regularly misused to describe NENs in general, and NETs are frequently referred to as benign, while they should always be considered malignancies as they do have metastatic potential. To prevent misconceptions in future NEN-related research, we reviewed the most recent terminology used to classify NENs of the digestive tract and created an overview that combines the classification of these NENs according to the World Health Organization (WHO) with location- and functionality-based classifications. This overview may help clinicians and researchers in understanding the current literature and could serve as a guide in the clinic as well as for writing future studies on NENs of the digestive tract. In this way, we aim for the universal use of terminology, thereby providing an efficient foundation for future NEN-related research.

Multifocal pancreatic PPoma in the setting of MEN1: Case report and review of literature

Introduction and importance

Functioning pancreatic neuroendocrine tumors (pNETs) that express pancreatic polypeptide—PPomas—do not yet have a pathognomonic clinical syndrome associated with them due to their overall rarity and diverse symptoms. Moreover, in patients with MEN1, the often multifocal nature of pNETs presents a unique clinical issue.

Case presentation

We report a case of a 22-year-old man with a known MEN1 gene mutation who was suffering from severe diarrhea (7–8 bowel movements per day) and was found to have only elevated PP levels on biochemical work-up. Ga68-DOTATATE PET/CT showed multifocal tumors in the body and tail of the pancreas that were not evident on contrast-enhanced CT. The patient underwent a successful laparoscopic radical antegrade modular pancreatosplenectomy (RAMP) and recovered well post-operatively with complete resolution of his diarrhea. Immunohistochemistry showed multiple pure PPomas.

Clinical discussion

This case highlights the unique propensity for multifocal disease in patients with MEN1 mutations and the utility of functional imaging by somatostatin analogs, i.e., Ga68-DOTATATE PET/CT, in order to perform oncologic laparoscopic pancreatic resections.

Conclusion

PPomas in the setting of MEN1 mutations are a unique clinical entity due to their diverse associated clinical syndromes and propensity for multifocal disease.

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PPomas have no pathognomonic clinical syndrome associated with them.

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Patients with MEN1 have a propensity for multifocal pNETs.

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DOTATE PET/CT is vital adjunct to pancreatic protocol CT for operative planning.

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Intra-operative ultrasound makes laparoscopic multi-focal pNET resection feasible.

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DOTATATE PET/CT surveillance is necessary due to high risk for recurrence in MEN1.

Evaluation of MGMT gene methylation in neuroendocrine neoplasms

Unresectable neuroendocrine neoplasms (NENs) often poorly respond to standard therapeutic approaches. Alkylating agents, in particular temozolomide, commonly used to treat high-grade brain tumors including glioblastomas, have recently been tested in advanced or metastatic NENs, where they showed promising response rates. In glioblastomas, prediction of response to temozolomide is based on the assessment of the methylation status of the MGMT gene, as its product, O-6-methylguanine-DNA methyltransferase, may counteract the damaging effects of the alkylating agent. However, in NENs, such a biomarker has not been validated yet. Thus, we have investigated MGMT methylation in 42 NENs of different grades and from various sites of origin by two different approaches: in contrast to methylation-specific PCR (MSP), which is commonly used in glioblastoma management, amplicon bisulfite sequencing (ABS) is based on high resolution next-generation sequencing and interrogates several additional CpG sites compared to those covered by MSP. Overall, we found MGMT methylation in 74% (31/42) of the NENs investigated. A higher methylation degree was observed in well-differentiated tumors and in tumors originating in the gastrointestinal tract. Comparing MSP and ABS results, we demonstrate that the region analyzed by the MSP test is sufficiently informative of the MGMT methylation status in NENs, suggesting that this predictive parameter could routinely be interrogated also in NENs.

Safety and efficacy of irreversible electroporation treatment in hepatobiliary and pancreatic tumours: a single-centre experience

AIM

To report initial experience with irreversible electroporation (IRE) in a single tertiary oncology centre and to describe its role in the management of liver and pancreatic tumours.

MATERIALS AND METHODS

The present study was a retrospective review of the technical success rate, complications, and treatment efficacy of patients who had undergone IRE treatment for hepatobiliary and pancreatic tumours between February 2014 to January 2020. The patients were divided into two cohorts: first 30 patients (cohort A) and subsequent 70 patients (cohort B) after a change in protocol.

RESULTS

One hundred IRE procedures (n=69 liver lesions; n=28 pancreatic lesions, n=3 nodal disease) were reviewed. The overall technical success rate was 99%. Early and immediate complications were 4% and 3%, respectively. In cohort A, the complete tumour ablation rate was 65% (13/20) for hepatic tumours, 20% (1/5) for locally advanced pancreatic adenocarcinoma, 50% (2/4) for pancreatic neuroendocrine tumours, and 0% (0/1) for nodal metastasis. For cohort B, the rate improved to 87.76% (43/49) for hepatic tumours, 28.57% (4/14) for locally advanced pancreatic adenocarcinoma, 80% (4/5) for pancreatic neuroendocrine, and 50% (1/2) for nodal metastasis. After the initial cohort A, cohort B showed a significant increase in the initial complete ablation rate in hepatic tumours (p=0.028).

CONCLUSION

IRE is a complex technique with a steep learning curve. It is safe, effective, and is valuable in the treatment of liver tumours that are unsuitable or considered high risk for conventional thermal ablation. Its role in the management of pancreatic tumours is less clear and requires larger studies.

Bioinformatics analysis reveals that ANXA1 and SPINK5 are novel tumor suppressor genes in patients with oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a solid tumor of squamous epithelial origin. Currently, surgery is still the main treatment for OSCC, with radiotherapy and chemotherapy as important adjuvant treatments. However, the problem of poor prognosis of OSCC patients still exists in clinical practice. To explore further potential biomarkers or treatment targets in OSCC patients, this study used a high-throughput gene expression database to study the potential molecular mechanisms of OSCC carcinogenesis.

METHODS

The GEO database related to OSCC was searched and analyzed using GEO2R. Oncomine and the Human Protein Atlas were used to evaluate the expression level of differentially-expressed genes (DEGs). The cBioPortal dataset was used to analyze the mutations of the potential DEGs and patient survival.

RESULTS

Three GEO datasets, GSE146483, GSE138206, and GSE148944, were downloaded and 7 DEGs were found in common in OSCC tissues. Using Oncomine and the Human Protein Atlas, ANXA1, IL1RN, and SPINK5 were decreased in cancer tissues, while protein levels of APOE and IFI35 were increased accordingly. Interestingly, low levels of ANXA1 and SPINKS were associated with the TNM stage of OSCC patients. No mutations in DEGs were found in OSCC patients, based on the cBioPortal dataset. Survival analysis indicated OSCC patients with high MSR1 had poor overall survival (OS), while low expression of CXCR4, ANXA1, IL1RN, and SPINK5 also predicted poor OS in OSCC patients.

CONCLUSIONS

Our findings uncovered 7 potential biomarkers of OSCC patients, with ANXA1 and SPINK5 serving as potential tumor suppressor genes in OSCC.

Differential diagnosis of solid pancreatic masses

Solid pancreatic lesions include mainly adenocarcinoma, neuroendocrine tumors pancreatic cystic neoplasms with solid component, solid pseudopapillary tumor, pancreatoblastoma, pancreatic lymphoma, and pancreatic metastasis. The most frequent pancreatic lesion is the adenocarcinoma, representing between 70% and 95% of all solid pancreatic neoplasm. The diagnosis of these lesions can be a challenge and currently, there are different imaging techniques such as CT scan, EUS and MRI with high sensitivity and specificity. The most widely used technique for the initial evaluation is the CT scan with a sensitivity between 76% and 92% for the diagnosis of pancreatic cancer. The EUS has a sensitivity for the detection of pancreatic lesions of around 98% and is accepted to be the most sensitive technique for the detection of small pancreatic tumors (<2 cm). The MRI, with a very high soft-tissue contrast resolution, provides an accuracy in the detection and staging of adenocarcinoma of 90-100%. A multimodality approach is usually necessary in patients with clinical suspicion of pancreatic lesion. The EUS is required for the local evaluation of the relation of the lesion with vessels and for tissue acquisition and the CT scan and/or MRI is usually required for the local and distance staging in case of pancreatic cancer. The purpose of this review is to provide an overview of solid pancreatic lesions and the role of the different imaging techniques in their evaluation.

Pancreatic Polypeptide-Secreting Tumour of the Proximal Pancreas (PPoma)-Ultra Rare Pancreatic Tumour: Clinically Malign, Histologically Benign

Background and objectives: Here we report a rare case of a pancreatic polypeptide-secreting tumour (PPoma) discovered by accident during an autopsy. These PPomas occur in less than 2% of all pancreatic neoplasms and are almost exclusively silent, i.e., they are non-functional. Symptoms arising from PPoma are due to its compression of surrounding tissue. Materials and methods: The autopsy was performed on a 68-year-old male diagnosed with multiple endocrine neoplasm type 1 (MEN1) due to the patient’s sudden death. Results: A solitary, densely fibrotic, pink-brown tumour, 18 mm in size tumorous mass, was localised in the head of the pancreas. Microscopically, the tumour had a glandular structure with a tubuloacinar arrangement of the cells. Immunohistochemically, we detected strong PP (pancreatic polypeptide) intracytoplasmic activity and negative glucagon activity. The PPoma was located in the head of the pancreas, likely resulting in the obstruction of the main pancreatic and common bile duct. Conclusions: To the best of our knowledge, this is the first report suggesting the association of PPomas with MEN1. Also, the PPoma could be the cause of acute hemorrhagic pancreatitis due to its location.