EPCO-03. GLIOMA ONCOGENESIS IN THE CONSTITUTIONAL MISMATCH REPAIR DEFICIENCY (CMMRD) SYNDROME

PURPOSE Constitutional Mismatch Repair Deficiency (CMMRD) is a cancer predisposition due to bi-allelic mutations in one of the four main mismatch repair (MMR) genes (PMS2, MSH2, MSH6 or MLH1) associated with early onset of cancers, especially glioblastomas (GBM). Our aim was to decipher the molecular specificities of gliomas occurring in this context. METHODS A comprehensive analysis of clinical, histopathological and genomic data (whole exome sequencing) was performed for 12 children with a CMMRD for which we had available frozen brain tumor material (10 GBM and 2 anaplastic astrocytomas). RESULTS Eight patients harbored an ultra-mutated phenotype with more than 100 somatic non synonymous (NS) SNV/Mb. No correlation was observed between the number of mutation and sex, age, overall survival or mutated MMR gene. POLE and POLD1 exonuclease domain driver somatic mutations were described for eight and one patients respectively. The 4/12 tumors without POLE somatic mutation did not show the classical ultra-hypermutation pattern. All patients with POLE mutation had already more than 20 NS SNV/Mb (median 40NS SNV/Mb, [range 23-114]) suggesting that the hypermutation phenomenon started before the appearance of the somatic POLE mutation. The mutational signatures of the tumors, dominated by the MMR signatures, were not modified after the onset of the POLE mutation when analyzing the different mutation bursts. Specific recurrent somatic mutations were observed in SETD2 (9/12), TP53 (9/12), NF1 (9/12), EPHB2 (8/12), and DICER1 (7/12). Only half of the tumors overexpressed PDL1 by immunohistochemistry and this overexpression was not associated with a higher tumor mutation burden. CONCLUSION CMMRD-associated gliomas have a specific oncogenesis that does not trigger usual pathways and mutations seen in sporadic pediatric or adult GBM. Frequent alterations in other pathways (e.g. MAPK or DNA-PK pathway) may suggests the use of other targeted therapies aside from PD1 inhibitors.

A case of esophageal granular cell tumor diagnosed by mucosal incision-assisted biopsy

For an esophageal submucosal mass suspicious of granular cell tumor (GCT) based on gross appearance and endoscopic ultrasound findings, a sufficient number of biopsy specimens is required for a definite diagnosis using immunohistochemical examination. When the specimen obtained by forceps biopsy is insufficient, endoscopic ultrasound-fine needle aspiration (EUS-FNA) is believed to be an useful alternative. However, it may be difficult to obtain an adequate amount of tumor material using EUS-FNA. Mucosal incision-assisted biopsy (MIAB) is a simple method that can collect larger amounts of specimens. This procedure is helpful for physicians who encounter the problem of obtaining an adequate amount of biopsy material from esophageal tumors suspicious for GCT. We present a case of esophageal GCT that was successfully diagnosed through MIAB.

Modern possibilities of optical reconstructive surgery in patients after removal of tumor of iridociliary zone

Choroid tumors constitute 2/3 of all intraocular tumors, out of which 23% are tumors of the iris and the ciliary body, and the rest are tumors of the choroid. After removing the tumor of the iridociliary zone (ICZ) it is necessary to perform optical reconstructive surgery to reduce light aberrations and increase visual functions. Purpose. To identify key features of the complex rehabilitation of patients after removal of the ICZ tumor. Material and methods. The clinical and functional results of the complex rehabilitation of 12 patients (12 eyes) aged from 35 to 84 years (average 66 years) were studied at least 1 year after removal of the ICZ tumor. The area of the iris defect before the reconstructive surgery ranged from 15% to 55%. Preoperative uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA) were 0.26 ± 0.19 (from 0.01 to 0.6) and 0.46 ± 0.22 (from 0.1 to 0.8) respectively. All patients were underwent phacoemulsification of cataract and implantation of the iris-lens diaphragm. Results. After the reconstructive surgery, UCVA and BCVA increased:0.5 ± 0.17 (from 0.2 to 0.7) and 0.61 ± 0.27 (from 0.3 to 0.9) respectively. Undesirable optical effects were decreased, and patients were satisfied with the cosmetic result. Conclusion. The presented algorithm of optical reconstructive surgery after removal of the ICZ tumor creates necessary conditions for increasing postoperative functional results and improving the quality of life of these patients. Key words: tumor of the iridociliary zone, iris-lens diaphragm, optical reconstructive surgery, phacoemulsification of cataract.

OMIC-07. FEASIBILITY AND UTILITY OF EPIGENOMIC PROFILING FOR CHILDHOOD CNS TUMORS IN HONG KONG

Genome-wide DNA methylation profiling has emerged as an important diagnostic tool that complements histopathology for CNS tumors in children and adults. Literature describing its application in Asian countries is nonetheless limited. Herein, we report the feasibility and utility of adopting such platform for children diagnosed with CNS tumors in Hong Kong. A multi-institutional cohort (n=94, 97% of Chinese ethnicity) with CNS embryonal or high grade neuroepithelial tumors (HGNET) diagnosed in Hong Kong from 1996–2020 was assembled based on tissue availability. DNA was extracted from FFPE tumor material (median 301ng, range 13-1000ng), bisulfite converted and profiled with the Infinium Methylation EPIC BeadChip kit. Raw data were analyzed on the German Cancer Research Center MNP 2.0 classifier and through unsupervised dimensionality-reduction analysis (t-SNE) referencing a published CNS tumor reference dataset (GSE90496). The radio-histologic diagnosis included medulloblastoma (n=65), ATRT (n=9), pineal parenchymal tumors (n=7), ETMR (n=5), CNS-PNET (n=4) and other embryonal tumors/HGNETs (n=4). Methylation class could be assigned based on results from MNP 2.0 (calibrated score ≥ 0.9) in 62 patients (66%, including 2 clustering with control) and t-SNE in 22 (23%), while no-match was encountered in 10 (11%). Methylation-based analysis allowed confirmation of diagnosis and assignment of molecular subgroup in 64 patients (68%), confirmation of histologic diagnosis alone in 5 (5%) and resulted in revision/reassignment of diagnosis in 13 (14%). Among medulloblastoma samples that were assigned molecular tumor classes (n=57), 8 clustered with WNT-activated medulloblastoma, 13 with SHH-activated medulloblastoma, 10 with Group 3 medulloblastoma, 21 with Group 4 medulloblastoma, and 5 with non-medulloblastoma entities (high-grade gliomas=3, ETMR=1, ATRT=1). In conclusion, epigenomic profiling allowed refinement of disease classification for pediatric CNS tumors. Availability of such methodology in Asia sets the stage for international collaborations in molecularly-driven trials.

Refinement of an Established Procedure and Its Application for Identification of Hypoxia in Prostate Cancer Xenografts

Background: This pre-clinical study was designed to refine a dissection method for validating the use of a 15-gene hypoxia classifier, which was previously established for head and neck squamous cell carcinoma (HNSCC) patients, to identify hypoxia in prostate cancer. Methods: PC3 and DU-145 adenocarcinoma cells, in vitro, were gassed with various oxygen concentrations (0–21%) for 24 h, followed by real-time PCR. Xenografts were established in vivo, and the mice were injected with the hypoxic markers [18F]-FAZA and pimonidazole. Subsequently, tumors were excised, frozen, cryo-sectioned, and analyzed using autoradiography ([18F]-FAZA) and immunohistochemistry (pimonidazole); the autoradiograms used as templates for laser capture microdissection of hypoxic and non-hypoxic areas, which were lysed, and real-time PCR was performed. Results: In vitro, all 15 genes were increasingly up-regulated as oxygen concentrations decreased. With the xenografts, all 15 genes were up-regulated in the hypoxic compared to non-hypoxic areas for both cell lines, although this effect was greater in the DU-145. Conclusions: We have developed a combined autoradiographic/laser-guided microdissection method with broad applicability. Using this approach on fresh frozen tumor material, thereby minimizing the degree of RNA degradation, we showed that the 15-gene hypoxia gene classifier developed in HNSCC may be applicable for adenocarcinomas such as prostate cancer.

Feasibility of whole-genome sequencing in routine clinical practice.

3013 Background: In the next few years numerous drugs will be approved for defined genomic targets, most of these in a tumor agnostic manner. Identifying patients who can benefit from this is critical for the future success of precision medicine, ideally using a single comprehensive test to detect all possible biomarkers. The WIDE study (WGS Implementation in standard cancer Diagnostics for Every cancer patient) aimed to evaluate the feasibility, clinical validity (primary endpoints) and added value (secondary endpoint) of clinical grade Whole Genome Sequencing (cWGS) in routine clinical practice. Methods: cWGS was prospectively performed on 1,200 consecutive patients with (suspected) metastatic cancer. Tumor material was obtained during routine clinical procedures for both Standard-Of-Care (SOC) and cWGS. Next to securing a high quality specimen for SOC diagnostics, multiple frozen sections per patient were evaluated to identify the sample most suitable for WGS. cWGS was conducted independently of, but in parallel with SOC diagnostics, which included SOC molecular diagnostics (Moldx) for 48% of patients. cWGS and MolDx results were compared and discussed in a dedicated tumor board. Additional tests for resolving discordances were applied when needed. Results: cWGS was successfully performed in 69% (841/1217) of samples with a technical success rate of 97% (841/871). An insufficient amount of tumor cells ( < 20%) was the main reason for not completing cWGS (25%, 310/1217). cWGS turn-around-time (TAT), due to continuous improvements to the clinical procedure and cWGS pipeline over the course of the study, decreased to 10 working days. A total of 856 genomic biomarkers identified by SOC MolDx could be compared to cWGS results. Initial analyses of discordances revealed an error rate of 2.1% (18/856) for cWGS compared to a 1.0% (8/856) error rate for SOC Moldx. After optimizing cWGS and SOC pipelines based on these findings, error rates dropped to 0.6% (5/856) and 0.7% (6/856) for cWGS and SOC MolDx, respectively. Overall, cWGS identified clinically actionable (routine practice and experimental) biomarkers in 71% of all patients tested. Compared to SOC MolDx, cWGS identified one or more additional clinically actionable biomarkers in 54% (446/832) of patients. Interestingly, in patients who were not tested by SOC MolDx, actionable variants were identified by cWGS in 54% (153/282). Conclusions: The WIDE study has shown that cWGS is feasible in routine clinical practice in a comprehensive cancer center setting, using tumor material obtained during routine procedures. Furthermore, cWGS showed added value by identifying one or more additional clinically actionable biomarkers in 54% of patients including patients who had not received SOC Moldx. These outcomes have led to the successful adoption of cWGS at the Netherlands Cancer Institute as part of routine care, which will further facilitate precision medicine for cancer patients.

Peripheral blood levels of tumor-infiltrating lymphocytes (TILs) and circulating tumor cells (CTCs) in patients with colorectal cancer.

e15510 Background: Tumor is a structure where malignant cells interact, among others, with cells of the adaptive and innate immune systems largely determining the tumor microenvironment. The role of TILs in the disease prognosis has been shown. The amount of CTCs is one of the factors that significantly affect the risk and rate of metastasis. The purpose of the study was to assess an association between TILs and CTCs in the peripheral blood of patients with various stages of colorectal cancer (CRC). Methods: The study included 299 patients (aged 42-86 years, mean age 64.2±1.7) with stage II-IV CRC T1-4N0-2M0-1. TILs were identified in tumor material after standard histological processing. Lymphocytes were counted per 100 epithelial cells in 5 fields of view at a magnification of x400; the result was expressed as a percentage ( < 5% weak, 5-30% moderate, >30% strong). The numbers of CTCs were measured in the peripheral blood using the Veridex CellSearch system (Janssen), taking into account the expression of epithelial cell adhesion markers EpCAM, cytokeratins 8,18,19 and absence of the CD45 expression. The blood sample was evaluated according to the following criteria: 0 CTCs, 1-3 CTCs, and more than 3 CTCs. Statistical analysis of results was performed in the Statistica 13.0 program (StatSoftInc., USA). Results: Weak lymphocytic infiltration was detected in 32.8%, moderate - in 48.1%, strong - in 19.1% of cases. CTCs were detected in 62.9% cases (in 188 of 299 patients). The percentages of patients with 1-3 CTCs and with >3 CTCs were equal - 50% (94 of 188). CTCs were not registered in 37.1% cases (111 of 299). The absence of CTCs was noted equally often in moderate and strong lymphocytic infiltration – 43.7% and 43.8%. The presence of tumor cells in the peripheral blood was most often detected in weak lymphocytic infiltration, being 1.4 times more frequent than in moderate and strong infiltration (76.5% vs. 56.3% and 56.2%) (p = 0.019, c2= 11.890). Conclusions: The study demonstrated a significant relationship between the level of CTCs and the intensity of lymphocytic infiltration in the tumor (p≤0.05), which can be used as a new prognostic approach.

G-CSF as a suitable alternative to GM-CSF to boost dinutuximab-mediated neutrophil cytotoxicity in neuroblastoma treatment

BackgroundCurrent immunotherapy for patients with high-risk neuroblastoma involves the therapeutic antibody dinutuximab that targets GD2, a ganglioside expressed on the majority of neuroblastoma tumors. Opsonized tumor cells are killed through antibody-dependent cellular cytotoxicity (ADCC), a process mediated by various immune cells, including neutrophils. The capacity of neutrophils to kill dinutuximab-opsonized tumor cells can be further enhanced by granulocyte-macrophage colony-stimulating factor (GM-CSF), which has been shown in the past to improve responses to anti-GD2 immunotherapy. However, access to GM-CSF (sargramostim) is limited outside of Northern America, creating a high clinical need for an alternative method to stimulate dinutuximab responsiveness in the treatment of neuroblastoma. In this in vitro study, we have investigated whether clinically well-established granulocyte colony-stimulating factor (G-CSF) can be a potentially suitable alternative for GM-CSF in the dinutuximab immunotherapy regimen of patients with neuroblastoma.MethodsWe compared the capacity of neutrophils stimulated either in vitro or in vivo with GM-CSF or G-CSF to kill dinutuximab-opsonized GD2-positive neuroblastoma cell lines and primary patient tumor material. Blocking experiments with antibodies inhibiting either respective Fc gamma receptors (FcγR) or neutrophil integrin CD11b/CD18 demonstrated the involvement of these receptors in the process of ADCC. Flow cytometry and live cell microscopy were used to quantify and visualize neutrophil-neuroblastoma interactions.ResultsWe found that G-CSF was as potent as GM-CSF in enhancing the killing capacity of neutrophils towards neuroblastoma cells. This was observed with in vitro stimulated neutrophils, and with in vivo stimulated neutrophils from both patients with neuroblastoma and healthy donors. Enhanced killing due to GM-CSF or G-CSF stimulation was consistent regardless of dinutuximab concentration, tumor-to-neutrophil ratio and concentration of the stimulating cytokine. Both GM-CSF and G-CSF stimulated neutrophils required FcγRIIa and CD11b/CD18 integrin to perform ADCC, and this was accompanied by trogocytosis of tumor material by neutrophils and tumor cell death in both stimulation conditions.ConclusionsOur preclinical data support the use of G-CSF as an alternative stimulating cytokine to GM-CSF in the treatment of high-risk neuroblastoma with dinutuximab, warranting further testing of G-CSF in a clinical setting.

Digoxin treatment reactivates in vivo radioactive iodide uptake and correlates with favorable clinical outcome in non‐medullary thyroid cancer

Purpose Non-medullary thyroid cancer (NMTC) treatment is based on the ability of thyroid follicular cells to accumulate radioactive iodide (RAI). However, in a subset of NMTC patients tumor dedifferentiation occurs, leading to RAI resistance. Digoxin has been demonstrated to restore iodide uptake capacity in vitro in poorly differentiated and anaplastic NMTC cells, termed redifferentiation. The aim of the present study was to investigate the in vivo effects of digoxin in TPO-Cre/LSL-BrafV600E mice and digoxin-treated NMTC patients. Methods Mice with thyroid cancer were subjected to 3D ultrasound for monitoring tumor growth and 124I PET/CT for measurement of intratumoral iodide uptake. Post-mortem analyses on tumor tissues comprised gene expression profiling and measurement of intratumoral autophagy activity. Through PALGA (Dutch Pathology Registry), archived tumor material was obtained from 11 non-anaplastic NMTC patients who were using digoxin. Clinical characteristics and tumor material of these patients were compared to 11 matched control NMTC patients never treated with digoxin. Results We found that in mice, tumor growth was inhibited and 124I accumulation was sustainably increased after short-course digoxin treatment. Post-mortem analyses revealed that digoxin treatment increased autophagy activity and enhanced expression of thyroid-specific genes in mouse tumors compared to vehicle-treated mice. Digoxin-treated NMTC patients exhibited significantly higher autophagy activity and a higher differentiation status as compared to matched control NMTC patients, and were associated with favourable clinical outcome. Conclusions These in vivo data support the hypothesis that digoxin may represent a repositioned adjunctive treatment modality that suppresses tumor growth and improves RAI sensitivity in patients with RAI-refractory NMTC.