PhD Scientific Days 2021

PO_II_L: Pathology and Oncology II. Lectures

Liquid Biopsy-Based Monitoring of EZH2 Mutations in Follicular Lymphoma

Text of the abstract

INTRODUCTION: Follicular lymphoma (FL) is the most common type of indolent non-Hodgkin lymphomas with an average overall survival rate of 15 years. The prolonged disease course raises the need for an effective disease monitoring system. Molecular analysis of tumor derived circulating DNA (ctDNA), frequently referred to as liquid biopsy, is a promising minimally invasive diagnostic tool for patients suffering from malignancies. Recent studies interrogating the genomic background of FL have revealed hot spot mutations in the epigenetic regulator EZH2 gene in 25% of patients.
AIMS: In our study, we tested the potential of liquid biopsy to detect and monitor EZH2 mutations in plasma samples of patients with EZH2 mutant FL treated with immunochemotherapy.
METHODS: Eighty-five blood plasma samples have been collected from forty-one EZH2 mutant patients. The EZH2 mutation status of the plasma specimens was assessed using a multiplex digital droplet PCR (ddPCR, Bio-Rad Laboratories, USA) approach, detecting seven different EZH2 hotspot mutations using only two PCR reactions.
RESULT: Among the forty-one patients, 36 responded to treatment (88%), meanwhile 5 patients did not (12%). We detected an EZH2 mutation in 89% of the samples collected prior treatment (17/19). Similarly, 86% of the samples (6/7) collected during therapy from patients not responding to treatment proved to be EZH2 mutant, meanwhile only 22% of the samples were positive from responding patients (6/33). As expected, all samples collected during remission were EZH2 wild-type (0/26). EZH2 variant allele frequencies (VAF) correlated with the metabolic tumor volume detected on the PET-CT scans. We also demonstrated spatial heterogeneity of EZH2 mutations in two cases, where different EZH2 mutations deriving from distinct anatomical sites could simultaneously be detected in the plasma. The median sensitivity of our ddPCR approach was 0.15%, with EZH2 VAFs ranging between 0.2 and 74%.
CONCLUSION: Our results demonstrate that liquid biopsy offers a sensitive, radiation-free, minimally-invasive monitoring method for EZH2 mutant FL patients.
Funding: Prepared with the support of the Doctoral Student Scholarship (NKFIH KDP-1022882) of the Co-operative Doctoral Program of the Ministry of Innovation and Technology and the Semmelweis 250+ Excellence PhD Scholarship from the EFOP-3.6.3-VEKOP-16-2017-00009 grant.

University and Doctoral School

Semmelweis University, Doctoral School of Pathological Sciences