Identification and Functional Analysis of a Novel CTNNB1 Mutation in Pediatric Medulloblastoma

Medulloblastoma is the primary malignant tumor of the Central Nervous System (CNS) most common in pediatrics. We present here, the histological, molecular, and functional analysis of a cohort of 88 pediatric medulloblastoma tumor samples. The WNT-activated subgroup comprised 10% of our cohort, and all WNT-activated patients had exon 3 CTNNB1 mutations and were immunostained for nuclear β-catenin. One novel heterozygous CTNNB1 mutation was found, which resulted in the deletion of β-catenin Ser37 residue (ΔS37). The ΔS37 β-catenin variant ectopically expressed in U2OS human osteosarcoma cells displayed higher protein expression levels than wild-type β-catenin, and functional analysis disclosed gain-of-function properties in terms of elevated TCF/LEF transcriptional activity in cells. Our results suggest that the stabilization and nuclear accumulation of ΔS37 β-catenin contributed to early medulloblastoma tumorigenesis.

Molecular Profiling of Endometrial Cancer: An Exploratory Study in Aotearoa, New Zealand

Background: Aotearoa, New Zealand, has one of the fastest-rising rates of endometrial cancer (EC) worldwide, increasing particularly in younger Māori and Pasifika women. There is a move towards using molecular profiling to direct treatment for each EC subtype. Aim: This study aimed to explore the molecular profiling of primary EC tissue in Aotearoa. Methods: We used the PORTEC guidelines for the molecular subtyping of 90 patients’ samples into four categories: POLE-mutated, p53 abnormal, mismatch repair deficient (MMRd) and no specific molecular profile (NSMP). The CTNNB1 mutation and L1CAM expression were also included in the analysis. POLE and CTNNB1 mutations were analysed using targeted next-generation sequencing (NGS). Novel mutations were assessed using VarSome. MMRd, L1CAM and p53 abnormalities were analysed using immunohistochemistry. Results: In total, 15 samples were MMRd, 9 were p53 abnormal, 8 were POLE-mutated and the rest (56) were NSMP. Eleven samples had exon 3 CTNNB1 mutations and eleven novel POLE mutations were described. Conclusion: Surrogate markers for POLE mutations should be investigated. The validation of POLE variants and CTNNB1 mutations as part of an Aotearoa-based molecular panel is warranted.

Trends in diagnostic and therapeutic strategies for extra-abdominal desmoid-type fibromatosis: Japanese musculoskeletal oncology group questionnaire survey

Objective The mainstay of treatment modality for extra-abdominal desmoid-type fibromatosis (DF) has shifted from surgery, which often impairs ADL/QOL, to conservative treatment including active surveillance. In the present study, we conducted a longitudinal survey on the diagnosis and treatment of DF at facilities belonging to the Japanese Musculoskeletal Oncology Group, which is a research group of facilities specializing in the treatment of bone and soft tissue tumors in Japan to clarify the transition of medical care for extra-abdominal DF. Methods The same questionnaire was administered in 2015 and 2018, and responses were obtained from 46 (69%) of 67 facilities and 42 (53%) of 80 facilities in 2015 and 2018, respectively. Results Although immunostaining for β-catenin was often used for the pathological diagnosis in both 2015 and 2018, CTNNB1 mutation analysis was not performed either in 2015 or in 2018. As for the treatment strategy for resectable cases, surgical treatment including wide resection was selected at 11 facilities (24% of respondents) in 2015, and further decreased to 5 facilities (12%) in 2018. Conservative treatment with active surveillance or medical treatment was the most common treatment for both resectable and difficult-to-resect cases. COX-2 inhibitors and tranilast were often used in the drug treatment of both resectable and difficult-to-resect cases. Few facilities provided radiotherapy, methotrexate and vinblastine, or DOX-based chemotherapy for refractory cases in both 2015 and 2018. Conclusions A good trend was found in the questionnaire survey. It will be further necessary to disseminate clinical practice guidelines to physicians more widely, and to have them understand and implement the most up-to-date medical practice strategies for this rare disease.

Prognosis value of S45F mutation of CTNNB1 in desmoid-type fibromatosis (DF): Prospective analysis of 500 consecutive patients (pts) from ALTITUDES trial.

11510 Background: DF rare locally aggressive fibroblastic non-metastasizing tumor, with an unpredictable course. Its management remains challenging, there is a current shift in standard of care from large surgical resection (SR) to active surveillance (AS). Most of DF display somatic mutation of CTNNB1, with three major hotpots: S45F, T41A and S45P. The poor prognosis of S45F is a matter of debate (Timbergen et al. Ann Surg 2019). Methods: ALTITUDES (NCT02867033) is a nationwide prospective registry of DF, diagnosed from January 2016 to December 2020 and confirmed by central pathological review. CTNNB1 mutations were identified by NGS. Primary endpoint was event-free survival (including disease progression or relapse). We have selected pts managed by AS, SR or systemic treatments as front-line. Pt undergoing R2 resection and then managed by follow-up were part of AS group. Prognostic factors were assessed using univariate and multivariate Cox Model. Results: From the 630-pts enrolled in ALTITUDES, 500 (79.3%) were eligible for the present analysis. Exclusion criteria were diagnosis before 2016 in 13 pts, multiple DF in 33 pts, 39 pts without CTNNB1 mutation analysis, and 45 pts receiving other treatments. The study population included 349 females (69.8%), the median age was 40 years (range 1-89). Abdominal wall was the predominant primary site: 161 pts (32.2%). In 430 (86.0%) cases, there was a CTNNB1 mutation, including, S45F in 56 cases (11.2%). In 70 cases (14.0%), we did not identify CTNNB1 mutation. The front-line managements were AS in 361 pts (72.2%), SR with R0/R1 margins in 57 cases (11.4%) and systemic treatments in 82 pts (16.5%). The median follow-up was 23 months (Range, 0.4-55). Overall, progression or relapse occurred in 128 pts (25.6%). We observed a significant EFS-difference between treatment groups, both in univariate and multivariate analysis with, compared to AS, a better outcome in patients with SR and worse outcome in patients who had received a systemic treatment (p = 0.01 in multivariate analysis). The risk of event was significantly associated with the tumor size, with a HR = 1.46 in tumors larger than 50 mm compared to smaller tumors (95%CI, 1.01-2.10, p = 0.04). We did not observe any significant association between the CTNNB1 mutational status and the outcome: compared to patients with another mutation, the hazard ratio associated with a S45F mutation was HR = 0.84 (95%CI, 0.48-1.46, p = 0.53) in multivariate analysis. Age, gender, location (abdominal wall versus other) were not associated with EFS. Conclusions: In this large prospective study, S45F was not an independent poor prognostic factor in DF. Size and front-line treatment drive both the outcome. The understanding and prediction of natural course of DF require further studies.

Clinicopathological features of 70 desmoid-type fibromatoses confirmed by β-catenin immunohistochemical staining and CTNNB1 mutation analysis

Desmoid-type fibromatosis (DF) is a locally aggressive neoplasm characterized by mutations in the CTNNB1 gene, which encodes the β-catenin protein. We reviewed 85 cases of DF and performed Sanger sequencing for detecting mutations in CTNNB1 and immunostaining for detecting β-catenin localization. We included 70 DF samples, of which 56 cases demonstrated nuclear β-catenin localization and 43 cases harboured CTNNB1 mutations. CTNNB1-mutant DF samples consistently displayed nuclear β-catenin expression and were derived from larger-sized tumours compared to samples with wild-type CTNNB1. When we further classified DF cases into 2 subgroups based on the type of specimen, excised specimens with nuclear β-catenin expression frequently displayed CTNNB1 mutation and no statistical correlation between nuclear β-catenin expression and CTNNB1 mutation was observed in biopsies. When we classified CTNNB1 mutation cases into 2 subgroups (DF with T41A or T41I, and DF with S45F or S45P), T41A or T41I mutations were observed more frequently in males than in females. Additionally, DF tumours harbouring S45F or S45P mutations were located more frequently in the abdominal wall than tumours with T41A or T41I mutations. In conclusion, CTNNB1 mutation correlates with nuclear β-catenin expression in larger or excised DF tumours, and DF harbouring CTNNB1 mutations manifest variable clinical presentations.

Prognostic significance of CTNNB1 mutation in recurrence of sporadic desmoid tumors

Aim: Desmoid tumor (DT) is a rare, locally aggressive benign neoplasm with a high recurrence rate. The majority of sporadic DTs are associated with mutations in CTNNB1, but whether CTNNB1 mutations are associated with the risk of DT recurrence remains unclear. The goal of this meta-analysis was to evaluate the association between CTNNB1 mutation and recurrence in surgically treated DT patients. Methods: PubMed, Embase and Cochrane library were systematically searched. The outcome of interest was the risk of recurrence. The number of patients with CTNNB1 mutation and the number of recurrences they developed were recorded and compared. The quality of these studies was assessed using the Newcastle–Ottawa Quality Assessment Scale. Odds ratios and variances were calculated and pooled. Results: A total of eight studies were identified including 637 patients. S45F-mutated DTs were more likely to recur compared with wild type, T41A and other mutated DTs. However, there were no statistically significant differences in the rate of recurrence between wild type and T41A mutation or other mutation. Conclusions: Among CTNNB1 mutations, the mutation S45F is a high-risk factor for recurrence of DT and may be a predictive marker for the recurrence of sporadic DT.