Neuroendocrine tumours (NETs) originate in tissues that contain cells derived from the embryonic neural crest, neuroectoderm and endoderm. Thus, NETs occur at many sites in the body, although the majority occur within the gastro-entero-pancreatic axis and can be subdivided into those of foregut, midgut and hindgut origin. Amongst these, only those of midgut origin are generally argentaffin positive and secrete serotonin, and hence only these should be referred to as carcinoid tumours. NETs may occur as part of complex familial endocrine cancer syndromes, such as multiple endocrine neoplasia type 1 (MEN1), although the majority occur as non-familial (i.e. sporadic) isolated tumours. Molecular genetic studies have revealed that the development of NETs may involve different genes, each of which may be associated with several different abnormalities that include point mutations, gene deletions, DNA methylation, chromosomal losses and chromosomal gains. Indeed, the foregut, midgut and hindgut NETs develop via different molecular pathways. For example, foregut NETs have frequent deletions and mutations of the MEN1 gene, whereas midgut NETs have losses of chromosome 18, 11q and 16q and hindgut NETs express transforming growth factor-alpha and the epidermal growth factor receptor. Furthermore, in lung NETs, a loss of chromosome 3p is the most frequent change and p53 mutations and chromosomal loss of 5q21 are associated with more aggressive tumours and poor survival. In addition, methylation frequencies of retinoic acid receptor-beta, E-cadherin and RAS-associated domain family genes increase with the severity of lung NETs. Thus the development and progression of NETs is associated with specific genetic abnormalities that indicate the likely involvement of different molecular pathways.
P D Leotlela, A Jauch, H Holtgreve-Grez, and R V Thakker
T Vandamme, M Beyens, G Boons, A Schepers, K Kamp, K Biermann, P Pauwels, W W De Herder, L J Hofland, M Peeters, G Van Camp, and K Op de Beeck
Mutations in DAXX/ATRX, MEN1 and genes involved in the phosphoinositide-3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway have been implicated in pancreatic neuroendocrine neoplasms (pNENs). However, mainly mutations present in the majority of tumor cells have been identified, while proliferation-driving mutations could be present only in small fractions of the tumor. This study aims to identify high- and low-abundance mutations in pNENs using ultra-deep targeted resequencing. Formalin-fixed paraffin-embedded matched tumor-normal tissue of 38 well-differentiated pNENs was sequenced using a HaloPlex targeted resequencing panel. Novel amplicon-based algorithms were used to identify both single nucleotide variants (SNVs) and insertion-deletions (indels) present in >10% of reads (high abundance) and in <10% of reads (low abundance). Found variants were validated by Sanger sequencing. Sequencing resulted in 416,711,794 reads with an average target base coverage of 2663 ± 1476. Across all samples, 32 high-abundance somatic, 3 germline and 30 low-abundance mutations were withheld after filtering and validation. Overall, 92% of high-abundance and 84% of low-abundance mutations were predicted to be protein damaging. Frequently, mutated genes were MEN1, DAXX, ATRX, TSC2, PI3K/Akt/mTOR and MAPK-ERK pathway-related genes. Additionally, recurrent alterations on the same genomic position, so-called hotspot mutations, were found in DAXX, PTCH2 and CYFIP2. This first ultra-deep sequencing study highlighted genetic intra-tumor heterogeneity in pNEN, by the presence of low-abundance mutations. The importance of the ATRX/DAXX pathway was confirmed by the first-ever pNEN-specific protein-damaging hotspot mutation in DAXX. In this study, both novel genes, including the pro-apoptotic CYFIP2 gene and hedgehog signaling PTCH2, and novel pathways, such as the MAPK-ERK pathway, were implicated in pNEN.
J Cros, O Hentic, V Rebours, M Zappa, N Gille, N Theou-Anton, D Vernerey, F Maire, P Lévy, P Bedossa, V Paradis, P Hammel, P Ruszniewski, and A Couvelard
Temozolomide (TEM) showed encouraging results in well-differentiated pancreatic neuroendocrine tumors (WDPNETs). Low O6-methylguanine-DNA methyltransferase (MGMT) expression and MGMT promoter methylation within tumors correlate with a better outcome under TEM-based chemotherapy in glioblastoma. We aimed to assess whether MGMT expression and MGMT promoter methylation could help predict the efficacy of TEM-based chemotherapy in patients with WDPNET. Consecutive patients with progressive WDPNET and/or liver involvement over 50% who received TEM between 2006 and 2012 were retrospectively studied. Tumor response was assessed according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 guidelines. Nuclear expression of MGMT was assessed by immunochemistry (H-score, 0–300) and MGMT promoter methylation by pyrosequencing. Forty-three patients (21 men, 58years (27–84)) with grade 1 WDPNET (n=6) or 2 (n=36) were analyzed. Objective response, stable disease, and progression rates were seen in 17 patients (39.5%), 18 patients (41.9%), and 8 patients (18.6%), respectively. Low MGMT expression (≤50) was associated with radiological objective response (P=0.04) and better progression-free survival (PFS) (HR=0.35 (0.15–0.81), P=0.01). Disease control rate at 18months of treatment remained satisfying with an MGMT score up to 100 (74%) but dropped with a higher expression. High MGMT promoter methylation was associated with a low MGMT expression and longer PFS (HR=0.37 (0.29–1.08), P=0.05). Low MGMT score (≤50) appears to predict an objective tumor response, whereas an intermediate MGMT score (50–100) seems to be associated with prolonged stable disease.
Ziqiang Yuan, Juliet C Gardiner, Elaine C Maggi, Shuyu Huang, Asha Adem, Svetlana Bagdasarov, Guiying Li, Sylvia Lee, Daniel Slegowski, Alyssa Exarchakis, James R Howe, Edmund C Lattime, Xingxing Zang, and Steven K Libutti
The B7 family, and their receptors, the CD28 family, are major immune checkpoints that regulate T-cell activation and function. In the present study, we explore the role of two B7 immune-checkpoints: HERV-H LTR-Associating Protein 2 (HHLA2) and B7 Family Member, H4 (B7x), in the progression of gastrointestinal and pancreatic neuroendocrine tumors (GINETs and PNETs). We demonstrated that both HHLA2 and B7x were expressed to a high degree in human GINETs and PNETs. We determined that the expression of B7x and HHLA2 correlates with higher grade and higher incidence of nodal and distant spread. Furthermore, we confirmed that HIF-1 overexpression is associated with the upregulation of B7x both in our in vivo (animal model) and in vitro (cell culture) models. When grown in vitro, islet tumor β-cells lack B7x expression, unless cultured under hypoxic conditions, which results in both hypoxia inducible factor 1 subunit alpha (HIF-1α) and B7x upregulation. In vivo, we demonstrated that Men1/B7x double knockout (KO) mice (with loss of B7x expression) exhibited decreased islet β-cell proliferation and tumor transformation accompanied by increased T-cell infiltration compared with Men1 single knockout mice. We have also shown that systemic administration of a B7x mAb to our Men1 KO mice with PNETs promotes an antitumor response mediated by increased T-cell infiltration. These findings suggest that B7x may be a critical mediator of tumor immunity in the tumor microenvironment of NETs. Therefore, targeting B7x offers an attractive strategy for the immunotherapy of patients suffering from NETs.
Kimberly Kamp, Ronald A M Damhuis, Richard A Feelders, and Wouter W de Herder
An increased association between neuroendocrine tumors of the gastrointestinal tract and pancreas (GEP-NET) and other second primary malignancies has been suggested. We determined whether there is indeed an increased risk for second primary malignancies in GEP-NET patients compared with an age- and sex-matched control group of patients with identical malignancies. The series comprised 243 men and 216 women, diagnosed with a GEP-NET between 2000 and 2009 in a tertiary referral center. The timeline, before-at-after diagnosis, and the type of other malignancies were studied using person-year methodology. Poisson distributions were used for testing statistical significance. All data were cross-checked with the Dutch National Cancer Registry. Out of 459 patients with GEP-NET, 67 (13.7%) had a second primary cancer diagnosis: 25 previous cancers (5.4%), 13 synchronous cancers (2.8%), and 29 metachronous cancers (6.3%). The most common types of second primary cancer were breast cancer (n=10), colorectal cancer (n=8), melanoma (n=6), and prostate cancer (n=5). The number of patients with a cancer history was lower than expected, although not significant (n=25 vs n=34.5). The diagnosis of synchronous cancers, mainly colorectal tumors, was higher than expected (n=13 vs n=6.1, P<0.05). Metachronous tumors occurred as frequent as expected (n=29 vs n=25.2, NS). In conclusion, our results are in contrast to previous studies and demonstrate that only the occurrence of synchronous second primary malignancies, mainly colorectal cancers, is increased in GEP-NET patients compared with the general population.
J Di Cristofaro, V Vasko, V Savchenko, S Cherenko, A Larin, M D Ringel, M Saji, M Marcy, J F Henry, P Carayon, and C De Micco
Like children exposed to Chernobyl fallout, the workers who cleaned up after the accident, also known as liquidators, have exhibited an increased incidence of thyroid cancer. A high prevalence of ret/PTC3 rearrangement has been found in pediatric post-Chernobyl thyroid tumors, but this feature has not been investigated in liquidator thyroid tumors. In this study we analyzed the prevalence of ret/PTC1 and ret/PTC3 in thyroid tumors from 21 liquidators, 31 nonirradiated adult Ukrainian patients, and 34 nonirradiated adult French patients. ret rearrangements in carcinomas were found in 83.3% of liquidators, 64.7% of Ukrainian patients, and 42.9% of French patients. The prevalence of ret/PTC1 was statistically similar in the three groups. The prevalence of ret/PTC3 was significantly higher in liquidators than in French patients (P = 0.03) but it was also high in nonirradiated Ukrainian patients who exhibited values intermediate between liquidators and French patients. In adenomas the prevalence of rearrangement was significantly higher in all Ukrainians than in French patients (P = 0.004). Like children exposed to Chernobyl fallout, liquidators showed a high prevalence of ret/PTC3. This finding suggests that irradiation had the same effect regardless of age. However, given the high rate of ret/PTC3 in nonirradiated adult Ukrainians, the possibility of genetic susceptibility or low-level exposure to radiation in that group cannot be excluded.
Rosalinda M Savoy and Paramita M Ghosh
A new paper by Tawadros et al. in Endocrine-Related Cancer demonstrates a link between macrophage migration inhibitory factor and neuroendocrine differentiation in prostate cancer. This paper may have implications in explaining the effect of prostatitis and chronic inflammation on the development of aggressive prostate cancer.
H Klemen, F M Smolle-Jüttner, and H H Popper
Typical and atypical carcinoids are neuroendocrine epithelial lung tumours which are difficult to distinguish. Confusion has been introduced by designating atypical carcinoids as well differentiated neuroendocrine carcinomas and including some tumours which are large cell neuroendocrine carcinomas.
We therefore investigated 32 typical and 23 atypical carcinoids of the lung, and 9 combined forms of atypical carcinoid and small cell carcinoma. The following parameters were each independently correlated in a multivariate analysis with 10-year survival data: nuclear and nucleolar polymorphism, mitotic counts, vascular invasion, lymph node metastasis, structural pattern, location of the tumours, immunohistochemistry, age and sex of the patients.
Typical carcinoids were characterized by an absence of vascular invasion and lymph node metastases, and a mean mitotic rate of 0.75/10 high power fields (HPFs), while atypical carcinoids were characterized by vascular invasion and/or metastases, a mean mitotic rate of 4.25/10 HPFs and nuclear pleomorphism. Combined forms of atypical carcinoid and small cell carcinoma were characterized by vascular invasion, metastases and a mean mitotic rate of 20.7/10 HPFs. Vascular invasion, lymph node metastases, mitotic counts and nuclear pleomorphism significantly correlated with 10-year survival data, whereas location, size and structural pattern of the tumour, age and sex did not correlate with survival. All tumours were positive for cytokeratins and at least two out of three general neuroendocrine markers. However, positive reactivity for different peptides, hormones, and neurotransmitters did not correlate with one of the structural subtypes of carcinoid or with patient survival.
J E S Ardill and B Erikkson
The measurement of general and specific biochemical markers in patients with neuroendocrine tumours assists with diagnosis and gives an indication of the effectiveness of treatment and they may be used as prognostic indicators. There is much agreement that chromogranin A is the most universally helpful marker; it is found to be elevated in the circulation of about 90% of patients with metastatic neuroendocrine tumours and there are several excellent commercially available kits which give reliable estimations. Specific markers are useful for diagnosis also, and are helpful indicators of the effectiveness of treatment, particularly where tumour bulk may not change as much as tumour activity. Sporadic pancreatic neuroendocrine tumours may secrete more than one peptide and this indicates a worsening prognosis. Because of the wide variation in the progression of neuroendocrine tumours, a prognostic indicator gives a significant advantage to the clinician in order to facilitate optimum treatment at the optimum stage of disease. Both chromogranin A and neurokinin A have been used as powerful prognostic indicators for midgut carcinoid tumours.
Jennifer A Chan, David P Ryan, Andrew X Zhu, Thomas A Abrams, Brian M Wolpin, Paige Malinowski, Eileen M Regan, Charles S Fuchs, and Matthew H Kulke
Octreotide and everolimus have demonstrated efficacy in neuroendocrine tumors. Pasireotide is a somatostatin analog with binding affinity to a broader range of somatostatin receptor subtypes than octreotide. We performed a phase I study to evaluate the safety and feasibility of combining pasireotide with everolimus in patients with advanced neuroendocrine tumors. Cohorts of patients with advanced neuroendocrine tumors were treated with escalating doses of pasireotide (600–1200 μg s.c. b.i.d., followed by pasireotide LAR 40–60 mg i.m. monthly) and everolimus (5–10 mg daily). Twenty-one patients were treated. Dose-limiting toxicities consisting of grade 3 rash and grade 3 diarrhea were observed. Twelve patients were safely treated at the maximum protocol-defined dose level of pasireotide LAR 60 mg i.m. monthly and everolimus 10 mg daily. Hyperglycemia was common; other observed toxicities were consistent with the known toxicities of either agent alone. Partial tumor response was observed in one patient; 17 (81%) patients experienced at least some tumor regression as their best response to therapy. In conclusion, pasireotide LAR 60 mg i.m. monthly in combination with everolimus 10 mg daily is feasible and associated with preliminary evidence of antitumor activity in patients with advanced neuroendocrine tumors. Further studies evaluating this combination are warranted.