Rectal neuroendocrine carcinoma: case report of a rare entity and perspective review of promising agents

LncRNA PCAT6 promotes progression and metastasis of colonic neuroendocrine carcinoma via MAPK pathway

BACKGROUND

Colonic neuroendocrine carcinomas (NECs) are highly malignant and invasive with poor prognosis. Long noncoding RNAs (LncRNAs) participate in the tumorigenesis and metastasis of multiple cancers

AIM

To detect the roles and mechanisms of lncRNA prostate cancer associated transcript 6 (PCAT6) in the progression of colonic NEC.

METHODS

Human NEC and adjacent normal samples were collected for immunohistochemistry staining of CgA and real-time quantitative polymerase chain reaction (RT-qPCR) of PCAT6 mRNA level. Subcutaneous xenograft tumor model and lung metastasis model were established in nude mice. The lung tissues were stained by hematoxylin and eosin to assess pulmonary metastasis. The expression of epithelial-mesenchymal transition (EMT)-related markers and pathway-related genes was measured by RT-qPCR and western blotting. CD56 expression was assessed by immunofluorescence staining. The biological functions of PCAT6 were examined by cell counting kit-8, colony formation assays, Transwell assays and wound healing assays. The interaction between PCAT6 and its potential downstream target was verified by luciferase reporter assays.

RESULTS

LncRNA PCAT6 was upregulated in human NEC samples and LCC-18 cells, and its high expression was positively correlated with poor prognosis in patients with colonic NEC. Additionally, the expression of PCAT6 was positively associated with the proliferation, migration, invasion, and EMT of LCC-18 cells. Moreover, PCAT6 facilitated tumor growth, lung metastasis and EMT in xenografts. Mechanistically, PCAT6 promoted the activation of MAPK to enhance the EMT in colonic NEC by targeting miR-326.

CONCLUSION

In conclusion, lncRNA PCAT6 accelerates the process of colonic NEC by activating ERK/p38 MAPK signaling through targeting miR-326. These results might provide useful information for exploring the potential therapeutic targets in colonic NEC.

Innovative approaches in predicting outcomes for rectal neuroendocrine tumors

Rectal neuroendocrine neoplasms pose significant challenges due to their varied presentations and prognoses. Traditional prognostic models, while useful, often fall short of accurately predicting clinical outcomes for these patients. This article discusses the development and implications of a novel prognostic tool, the GATIS score, which aims to enhance predictive accuracy and guide treatment strategies more effectively than current methods. Utilizing data from a large cohort and employing sophisticated statistical models, the GATIS score integrates clinical and pathological markers to provide a nuanced assessment of prognosis. We evaluate the potential of this score to transform clinical decision-making processes, its integration into current medical practices, and future directions for its development. The integration of genetic markers and other biomarkers could further refine its predictive power, highlighting the ongoing need for innovation in the management of rectal neuroendocrine neoplasms.

Treatment of poorly differentiated neuroendocrine carcinomas of rectum and anus with chemoradiotherapy: a single-centre evaluation

PURPOSE

Poorly differentiated neuroendocrine carcinoma (PDNEC) of the rectum and anus is a rare disease exhibiting aggressive biological behaviour, even if diagnosed early. Currently, there are no agreed standard treatment approaches and management of locally advanced (LA) and metastatic PDNEC usually follows treatments used in pulmonary neuroendocrine carcinomas because of the similarities with small cell lung cancer. The role of surgery in PDNEC is still debated and the benefit of chemoradiotherapy (CRT) is unknown. This report summarises the experiences of CRT application in anorectal PDNEC in a single Danish institution.

METHODS

All patients with PDNEC treated with concomitant CRT between May 2019 and January 2021 at a University hospital in Denmark were evaluated. Demographics, treatment and survival outcomes were collected and analysed.

RESULTS

Six patients were identified. Five patients received radiotherapy with 50.4 Gy/28 fractions, and four were eligible for curative resection after the CRT. Distant metastasis was observed in four patients at diagnosis. Two patients with synchronous liver metastases were treated with RFA, and one received a liver resection. The treatment was well tolerated with limited side effects. The median follow-up time was 17 months (range 10-36 months), and the median duration of response was 11.2 months (range 8.1 to 24.2 months). One patient achieved a complete response.

CONCLUSION

A multimodal treatment approach with CRT in advanced stages of PDNEC in a highly selected patient group is well tolerated and with a high chance of achieving local control and, combined with surgery, even complete response in a single case.

BRAF V600E-mutated large cell neuroendocrine carcinoma responding to targeted therapy: a case report and review of the literature

Large cell neuroendocrine carcinoma (LCNEC) is a rare and aggressive high-grade neuroendocrine tumor, commonly arising in the lung or in the gastrointestinal tract, with a frequent proportion of unknown primary origin (20%). In the metastatic setting, platinum-based or fluoropyrimidine-based chemotherapeutic regimens are as considered the first-line treatment, despite the limited duration of response. To date, the prognosis of advanced high-grade neuroendocrine carcinoma remains poor, suggesting the need to explore new treatment strategies in this orphan tumor. The evolving molecular landscape of LCNEC, not yet been completely defined, could explain the heterogeneous response to different chemotherapeutic regimens and suggest that treatment strategy could be driven by molecular features. v-Raf murine sarcoma viral oncogene homolog B (BRAF) mutations, well described in melanoma, thyroid cancer, colon cancer and lung adenocarcinoma, account for approximately 2% of cases in lung LCNEC. Here, we describe the case of a patient with a BRAF V600E-mutated LCNEC of unknown primary origin who partially responded to BRAF/mitogen-activated protein kinase kinase inhibitors after standard treatment. Additionally, BRAF V600E circulating tumor DNA was used to monitor disease response. Thereafter, we reviewed the available literature about the role of targeted therapy in high-grade neuroendocrine neoplasms to provide insight for future research to identify patients with driver oncogenic mutations, who can potentially benefit from target therapy.

Classification and Locoregional Treatment of Rectal Neuroendocrine Tumors

A 43-year-old male presented to his primary care physician's office with a complaint of painless rectal bleeding with a concomitant weight loss of 10-15 pounds and intermittent abdominal pain. Endoscopic evaluation was remarkable for a 5 mm rectal polyp roughly 10 cm from the anal verge. Resection was performed and the pathology was consistent with a low-grade neuroendocrine/carcinoid tumor. Immunostaining for synaptophysin, chromogranin, CD56, and CAM5.2 were positive while staining for CK20 was negative. Given the absence of metastasis on radiographic and endoscopic evaluation, the patient was managed conservatively thereafter with observation. Despite having an indolent clinical course, resection is recommended for all rectal neuroendocrine tumors. Locoregional endoscopic resection versus radical resection can be used for adequate tissue removal depending on the characteristics of the tumor and the degree of invasion.

Metastatic rectal neuroendocrine carcinoma presenting with treatment-refractory immune thrombocytopenia: A case report and literature review

RATIONALE

Colorectal neuroendocrine cancer (CRNEC) accounts for < 1% of all colorectal cancers. It presents in advanced stages and carries a risk of poor survival. CRNEC may be diagnosed incidentally on imaging or routine endoscopy. When symptomatic, it may mimic colorectal adenocarcinoma. Syncope and immune thrombocytopenic purpura (ITP) have not previously been reported as clinical presentations.

PATIENT CONCERNS

A 57-year-old man with human immunodeficiency virus infection on treatment, seizure and stroke without residue presented for the evaluation of fall and syncope.

DIAGNOSIS

Physical examination revealed tachycardia, swelling, and ecchymosis of his proximal left lower extremity. Laboratory tests showed a new isolated thrombocytopenia of 26,000/mm3. Computed tomography for a trauma survey showed an incidental left posterior rectal wall mass. After hospital admission, his platelet count dropped to 14,000/mm3. A peripheral blood smear revealed low platelet count, no schistocytes or immature cells. ITP at a high risk for bleeding was diagnosed and treated with standard medical therapy but remained refractory. Bone marrow biopsy showed metastatic neuroendocrine carcinoma, likely from the rectum.

INTERVENTIONS

Patient received courses of high-dose dexamethasone and intravenous immunoglobulin. He also receive eleven units of platelet transfusion. A course of rituximab was administered. The platelet count response was suboptimal or short lived with drop to a nadir of 4000/mm3. However, after initiation of Eltrombopag, the thrombocytopenia resolved. Patient was started on etoposide, carboplatin, Atezolizumab. His hospital stay was complicated by neutropenia and sepsis, which was successfully treated.

OUTCOMES

He was discharged to subacute rehab in stable condition. About 4 months later, he was readmitted for severe thrombocytopenia, septic shock, and acute respiratory failure. Despite appropriate treatment, the patient deteriorated and expired.

CONCLUSION

CRNEC is a rare aggressive disease with dismal outcome that lacks standardized treatment. Metastasis to the bone marrow is uncommon and concomitant ITP has not been reported. We report a rare case of rectal neuroendocrine carcinoma metastatic to bone marrow associated with refractory ITP and review the relevant literature.

Somatostatin and Its Receptor System in Colorectal Cancer

Somatostatin (SST)/somatotropin release-inhibiting factor (SRIF) is a well-known neuropeptide, widely distributed in the central and peripheral nervous systems, that regulates the endocrine system and affects neurotransmission via interaction with five SST receptors (SST1-5). In the gastrointestinal tract, the main SST-producing cells include intestinal enteroendocrine cells (EECs) restricted to the mucosa, and neurons of the submucosal and myenteric plexuses. The action of the SRIF system is based on the inhibition of endocrine and exocrine secretion, as well as the proliferative responses of target cells. The SST1–5 share common signaling pathways, and are not only widely expressed on normal tissues, but also frequently overexpressed by several tumors, particularly neuroendocrine neoplasms (NENs). Furthermore, the SRIF system represents the only peptide/G protein-coupled receptor (GPCR) system with multiple approved clinical applications for the diagnosis and treatment of several NENs. The role of the SRIF system in the histogenesis of colorectal cancer (CRC) subtypes (e.g., adenocarcinoma and signet ring-cell carcinoma), as well as diagnosis and prognosis of mixed adenoneuroendocrine carcinoma (MANEC) and pure adenocarcinoma, is poorly understood. Moreover, the impact of the SRIF system signaling on CRC cell proliferation and its potential role in the progression of this cancer remains unknown. Therefore, this review summarizes the recent collective knowledge and understanding of the clinical significance of the SRIF system signaling in CRC, aiming to evaluate the potential role of its components in CRC histogenesis, diagnosis, and potential therapy.