Novel preclinical gastroenteropancreatic neuroendocrine neoplasia models demonstrate the feasibility of mutation-based targeted therapy.

PURPOSE: Gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN) form a rare and remarkably heterogeneous group of tumors. Therefore, establishing personalized therapies is eminently challenging. To achieve progress in preclinical drug development, there is an urgent need for relevant tumor models. METHODS: We successfully established three gastroenteropancreatic neuroendocrine tumor (GEP-NET) cell lines (NT-18P, NT-18LM, NT-36) and two gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC) cell lines (NT-32 and NT-38). We performed a comprehensive characterization of morphology, NET differentiation, proliferation and intracellular signaling pathways of these five cell lines and, in addition, of the NT-3 GEP-NET cell line. Additionally, we conducted panel sequencing to identify genomic alterations suitable for mutation-based targeted therapy. RESULTS: We found that the GEP-NEN cell lines exhibit a stable neuroendocrine phenotype. Functional kinome profiling revealed a higher activity of serine/threonine kinases (STK) as well as protein tyrosine kinases (PTK) in the GEP-NET cell lines NT-3 and NT-18LM compared to the GEP-NEC cell lines NT-32 and NT-38. Panel sequencing revealed a mutation in Death Domain Associated Protein (DAXX), sensitizing NT-18LM to the Ataxia telangiectasia and Rad3 related (ATR) inhibitor Berzosertib, and a mutation in AT-Rich Interaction Domain 1A (ARID1A), sensitizing NT-38 to the Aurora kinase A inhibitor Alisertib. Small interfering RNA-mediated knock down of DAXX in the DAXX wild type cell line NT-3 sensitized these cells to Berzosertib. CONCLUSIONS: The newly established GEP-NET and GEP-NEC cell lines represent comprehensive preclinical in vitro models suitable to decipher GEP-NEN biology and pathogenesis. Additionally, we present the first results of a GEP-NEN-specific mutation-based targeted therapy. These findings open up new potentialities for personalized therapies in GEP-NEN.

Mapping Spatial Genetic Landscapes in Tissue Sections through Microscale Integration of Sampling Methodology into Genomic Workflows.

In cancer research, genomic profiles are often extracted from homogenized macrodissections of tissues, with the histological context lost and a large fraction of material underutilized. Pertinently, the spatial genomic landscape provides critical complementary information in deciphering disease heterogeneity and progression. Microscale sampling methods such as microdissection to obtain such information are often destructive to a sizeable fraction of the biopsy sample, thus showing limited multiplexability and adaptability to different assays. A modular microfluidic technology is here implemented to recover cells at the microscale from tumor tissue sections, with minimal disruption of unsampled areas and tailored to interface with genome profiling workflows, which is directed here toward evaluating intratumoral genomic heterogeneity. The integrated workflow-GeneScape-is used to evaluate heterogeneity in a metastatic mammary carcinoma, showing distinct single nucleotide variants and copy number variations in different tumor tissue regions, suggesting the polyclonal origin of the metastasis as well as development driven by multiple location-specific drivers.

Are Pathogenic Germline Variants in Metastatic Melanoma Associated with Resistance to Combined Immunotherapy?

BACKGROUND: Combined immunotherapy has significantly improved survival of patients with advanced melanoma, but there are still patients that do not benefit from it. Early biomarkers that indicate potential resistance would be highly relevant for these patients. METHODS: We comprehensively analyzed tumor and blood samples from patients with advanced melanoma, treated with combined immunotherapy and performed descriptive and survival analysis. RESULTS: Fifty-nine patients with a median follow-up of 13 months (inter quartile range (IQR) 11-15) were included. Interestingly, nine patients were found to have pathogenic or likely pathogenic (P/LP) germline variants in one of these genes: BRCA2, POLE, WRN, FANCI, CDKN2A, BAP1, PALB2 and RAD54B. Most of them are involved in DNA repair mechanisms. Patients with P/LP germline variants had a significantly shorter progression-free survival (PFS) and melanoma specific survival (MSS) compared to patients without P/LP germline variants (HR = 2.16; 95% CI: 1.01-4.64; p = 0.048 and HR = 3.21; 95% CI: 1.31-7.87; p = 0.011, respectively). None of the patients with a P/LP germline variant responded to combined immunotherapy. In the multivariate Cox-regression analysis, presence of a P/LP germline variant, S100B and lactate dehydrogenase (LDH) remained independently significant factors for MSS (p = 0.036; p = 0.044 and p = 0.001, respectively). CONCLUSIONS: The presence of P/LP germline variants was associated with resistance to combined immunotherapy in our cohort. As genes involved in DNA repair mechanisms are also involved in lymphocyte development and T-cell differentiation, a P/LP germline variant in these genes may preclude an antitumor immune response.

MAFA missense mutation causes familial insulinomatosis and diabetes mellitus.

The ß-cell-enriched MAFA transcription factor plays a central role in regulating glucose-stimulated insulin secretion while also demonstrating oncogenic transformation potential in vitro. No disease-causing MAFA variants have been previously described. We investigated a large pedigree with autosomal dominant inheritance of diabetes mellitus or insulinomatosis, an adult-onset condition of recurrent hyperinsulinemic hypoglycemia caused by multiple insulin-secreting neuroendocrine tumors of the pancreas. Using exome sequencing, we identified a missense MAFA mutation (p.Ser64Phe, c.191C>T) segregating with both phenotypes of insulinomatosis and diabetes. This mutation was also found in a second unrelated family with the same clinical phenotype, while no germline or somatic MAFA mutations were identified in nine patients with sporadic insulinomatosis. In the two families, insulinomatosis presented more frequently in females (eight females/two males) and diabetes more often in males (12 males/four females). Four patients from the index family, including two homozygotes, had a history of congenital cataract and/or glaucoma. The p.Ser64Phe mutation was found to impair phosphorylation within the transactivation domain of MAFA and profoundly increased MAFA protein stability under both high and low glucose concentrations in ß-cell lines. In addition, the transactivation potential of p.Ser64Phe MAFA in ß-cell lines was enhanced compared with wild-type MAFA. In summary, the p.Ser64Phe missense MAFA mutation leads to familial insulinomatosis or diabetes by impacting MAFA protein stability and transactivation ability. The human phenotypes associated with the p.Ser64Phe MAFA missense mutation reflect both the oncogenic capacity of MAFA and its key role in islet ß-cell activity.

Loss of Chromosome 18 in Neuroendocrine Tumors of the Small Intestine: The Enigma Remains.

BACKGROUND/AIMS: Neuroendocrine tumors of the small intestine (SI-NETs) exhibit an increasing incidence and high mortality rate. Until now, no fundamental molecular event has been linked to the tumorigenesis and progression of these tumors. Only the loss of chromosome 18 (Chr18) has been shown in up to two thirds of SI-NETs, whereby the significance of this alteration is still not understood. We therefore performed the first comprehensive study to identify Chr18-related events at the genetic, epigenetic and gene/protein expression levels. METHODS: We did expression analysis of all seven putative Chr18-related tumor suppressors by quantitative real-time PCR (qRT-PCR), Western blot and immunohistochemistry. Next-generation exome sequencing and SNP array analysis were performed with five SI-NETs with (partial) loss of Chr18. Finally, we analyzed all microRNAs (miRNAs) located on Chr18 by qRT-PCR, comparing Chr18+/- and Chr18+/+ SI-NETs. RESULTS: Only DCC (deleted in colorectal cancer) revealed loss of/greatly reduced expression in 6/21 cases (29%). No relevant loss of SMAD2, SMAD4, elongin A3 and CABLES was detected. PMAIP1 and maspin were absent at the protein level. Next-generation sequencing did not reveal relevant recurrent somatic mutations on Chr18 either in an exploratory cohort of five SI-NETs, or in a validation cohort (n = 30). SNP array analysis showed no additional losses. The quantitative analysis of all 27 Chr18-related miRNAs revealed no difference in expression between Chr18+/- and Chr18+/+ SI-NETs. CONCLUSION: DCC seems to be the only Chr18-related tumor suppressor affected by the monoallelic loss of Chr18 resulting in a loss of DCC protein expression in one third of SI-NETs. No additional genetic or epigenetic alterations were present on Chr18.

Is Upregulation of Aquaporin 4-M1 Isoform Responsible for the Loss of Typical Orthogonal Arrays of Particles in Astrocytomas?

The astrocytic endfoot membranes of the healthy blood-brain barrier-contacting the capillary-are covered with a large number of the water channel aquaporin 4 (AQP4). They form orthogonal arrays of particles (OAPs), which consist of AQP4 isoform M1 and M23. Under pathologic conditions, AQP4 is distributed over the whole cell and no or only small OAPs are found. From cell culture experiments, it is known that cells transfected only with AQP4-M1 do not form OAPs or only small ones. We hypothesized that in astrocytomas the situation may be comparable to the in vitro experiments expecting an upregulation of AQP4-M1. Quantitative Real-time PCR (qRT-PCR) of different graded astrocytomas revealed an upregulation of both isoforms AQP4 M1 and M23 in all astrocytomas investigated. In freeze fracture replicas of low-grade malignancy astrocytomas, more OAPs than in high-grade malignancy astrocytomas were found. In vitro, cultured glioma cells did not express AQP4, whereas healthy astrocytes revealed a slight upregulation of both isoforms and only a few OAPs in freeze fracture analysis. Taken together, we found a correlation between the decrease of OAPs and increasing grade of malignancy of astrocytomas but this was not consistent with an upregulation of AQP4-M1 in relation to AQP4 M23.

Inducing Differentiation of Premalignant Hepatic Cells as a Novel Therapeutic Strategy in Hepatocarcinoma.

Hepatocellular carcinoma (HCC) represents the second leading cause of cancer-related deaths and is reported to be resistant to chemotherapy caused by tumor-initiating cells. These tumor-initiating cells express stem cell markers. An accumulation of tumor-initiating cells can be found in 2% to 50% of all HCC and is correlated with a poor prognosis. Mechanisms that mediate chemoresistance include drug export, increased metabolism, and quiescence. Importantly, the mechanisms that regulate quiescence in tumor-initiating cells have not been analyzed in detail so far. In this research we have developed a single cell tracking method to follow up the fate of tumor-initiating cells during chemotherapy. Thereby, we were able to demonstrate that mCXCL1 exerts cellular state-specific effects regulating the resistance to chemotherapeutics. mCXCL1 is the mouse homolog of the human IL8, a chemokine that correlates with poor prognosis in HCC patients. We found that mCXCL1 blocks differentiation of premalignant cells and activates quiescence in tumor-initiating cells. This process depends on the activation of the mTORC1 kinase. Blocking of the mTORC1 kinase induces differentiation of tumor-initiating cells and allows their subsequent depletion using the chemotherapeutic drug doxorubicin. Our work deciphers the mCXCL1-mTORC1 pathway as crucial in liver cancer stem cell maintenance and highlights it as a novel target in combination with conventional chemotherapy. Cancer Res; 76(18); 5550-61. ©2016 AACR.

Frequency of BRAF V600E mutations in 969 central nervous system neoplasms.

BACKGROUND: Treatment options for oncological diseases have been enhanced by the advent of targeted therapies. The point mutation of the BRAF gene at codon 600 (BRAF V600E) is found in several tumor entities and can be approached with selective inhibitory antibodies. The BRAF inhibitor vemurafenib has demonstrated clinical efficacy in patients with BRAF V600E-mutant melanoma brain metastases and in other cancer diseases. Therefore the BRAF V600E mutation is a highly interesting oncological target in brain tumors. METHODS: This study assesses the BRAF V600E mutation status in 969 intracranial neoplasms using a tissue microarray method and immunohistochemical staining with the mutation-specific VE-1 antibody, followed by sequencing of positively stained cases. RESULTS: Out of 784 primary brain tumors seven cases with a BRAF V600E mutation were detected (7/784, 1 %). Six of these cases were neuroepithelial tumors (6/667, 1 %) encompassing 2 astrocytomas WHO grade II (2/42, 5 %), 1 gliosarcoma WHO grade IV (1/75, 1 %) and 3 glioblastomas WHO grade IV (3/312, 1 %). Interestingly, all three mutant glioblastomas showed epithelioid histopathological features. Patients with V600E mutated astrocytic tumors were significantly younger (mean age 15.3 years) than wildtype cases (58.2 years). Among three rhabdoid meningiomas, one case was mutated (1/3) while all other grade I-III meningiomas (1/116, 1 %) and all fifty vestibular schwannomas analyzed were of wildtype status. The vast majority of the BRAF V600E mutations were found in cerebral metastases of malignant melanomas and carcinomas (29/135, 22 %), with false-positive staining found in four breast cancer cases and two non-small-cell lung carcinoma (NSCLC) samples. CONCLUSIONS: Our data suggest routine screening for BRAF V600E mutations for glioblastomas WHO grade IV below the age of 30, especially in glioblastomas with epithelioid features and in all rhabdoid meningiomas WHO grade III. For colorectal carcinoma, thyroid cancer, malignant melanoma and gliomas BRAF V600E immunostaining is sufficient for screening purposes. We also recommend routine immunohistochemical staining followed by sequencing validation in rare CNS metastases or metastases of unknown primary. Immunohistochemical analysis using mutation-specific antibodies on tissue microarrays is a feasible, time- and cost-efficient approach to high-throughput screening for specific mutations in large tumor series but sequencing validation is necessary in unexpected cases.