Wnt targets genes are not differentially expressed in desmoid tumors bearing different activating β-catenin mutations

Biclonal Desmoid-Type Fibromatosis With Two Beta-Catenin Mutations: Evidence for the Recruitment of Normal Myofibroblasts

Sporadic aggressive fibromatosis, or desmoid-type fibromatosis, is characterized by oncogenic mutations in CTNNB1. The clonal cell is a myofibroblast-like cell, and it has been hypothesized that the recruitment of normal myofibroblasts could contribute significantly to the tumor. We describe a case in which a CTNNB1 p.T41A mutation was present at a mutant allele frequency of 30%, suggesting that a significant proportion of the tumor myofibroblasts may have been recruited from normal precursor pools. In addition, a small subclone with a p.S45F mutation (allele frequency of 2%) was identified in the tumor. This case provides additional evidence that myofibroblasts recruited by a tumor from a normal precursor pool contribute significantly to the tumor; such recruitment could impact response to treatment and long-term outcomes.

Lack of prognostic value of CTNNB1 mutation profile in desmoid-type fibromatosis

PURPOSE

This prospective nationwide cohort study aimed to investigate desmoid-type fibromatosis (DF) outcomes, focusing on the prognostic value of CTNNB1 mutations.

EXPERIMENTAL DESIGN

ALTITUDES (NCT02867033) was a nationwide prospective cohort study of DF diagnosed between January 2016 and December 2020. At diagnosis, CTNNB1 molecular alterations were identified using next-generation sequencing or Sanger sequencing. The primary endpoint was event-free survival (EFS) (progression, relapse, or death). We enrolled 628 patients managed by active surveillance (AS), surgical resection (SR), or systemic treatment as front-line therapy.

RESULTS

Overall, 516 (82.2%) patients (368 females [71.3%], median age 40.3 years [range, 1-89]) were eligible for analysis. In 435 (84.3%) cases, there was one CTNNB1 molecular alteration: p.T41A, p.S45F, or p.S45P. The front-line management was AS in 352 (68.2%), SR in 120 (23.3%), and systemic treatments in 44 (8.5%) patients. CTNNB1 mutation distribution was similar across the three therapeutic groups. The median follow-up period was 24.7 (range, 0.4-59.7) months. The estimated 3-year EFS rate was 66.2% (95%CI, 60.5%-71.2%). DF harboring p.S45F was significantly associated with male sex (p=0.03), non-abdominal wall sites (p=0.05), pain (p=0.007), and large tumor size (p=0.025). CTNNB1 p.S45F mutation was not significantly associated with EFS, either in univariate (hazard ratio [HR]=1.06; 95% confidence interval [CI], 0.65-1.73; p=0.81), or in multivariate analysis (HR=0.91; 95% CI, 0.55-1.49; p=0.71).

CONCLUSIONS

We found that CTNNB1 mutation profile was associated with unfavorable prognostic factors but was not a prognostic factor for EFS.

[Biology and signaling pathways involved in the oncogenesis of desmoid tumors]

Desmoid tumors (TDs) are derived from mesenchymal stem cells and their pathogenesis is strongly linked to the Wingless/Wnt cascade where the deregulation of β-catenin plays a major role. A mutation of the CTNNB1 encoding β-catenin is found in the majority of sporadic TD cases and constitutional mutations of APC have been described in heritable forms in patients with familial adenomatous polyposis (FAP). Estrogens could also play a role in pathogenesis and this is the basis for the use of hormone therapy. Other signaling pathways have been involved in the development of TDs such as Notch, Hedgehog, JAK/STAT, PI3 Kinase/AKT and mTOR. Metalloproteases are expressed in TDs and play a role in invasiveness. TGF-ß, as a growth factor, stimulates the transcriptional activity of β-catenin. Future studies will need to focus on better describing and understanding the immune environment of TDs. One of the major difficulties for the experimental study of TDs is the virtual absence of a preclinical model, either in vitro or in vivo. This is partly why the interactions between the different signaling pathways presented here and their consequences for the development of TDs are still poorly understood.

The role of patients' associations

The role of patient groups has grown steadily stronger since the first General Meeting of cancer patients in 1999 and the emergence of the rare diseases issue in the mid-eighties. This article demonstrates the role of a patient group (SOS DESMOIDE) gathering people suffering from a rare disease (the desmoid tumor) in the stimulation of scientific and medical research as well as the improvement of patient care, information and support provided to patients. It substantiates these elements with numerous socio-medico-psychological surveys, scientific publications and medical research implemented by medical teams and supported, even sometimes initiated, by SOS DESMOIDE. This research effort illustrates the significant impact of a partnership between patients and physicians-researchers on medical and scientific breakthroughs in a specific pathological field.