Abstract 5265: Novelmolecular subtypes of papillary thyroid carcinoma (PTC) driven by BRAFV600E-,RAS- and RET-mutations linked to distinct clinicopathological features and tumor immune microenvironment
Authors: Long Miaoyun , Yu Yunfang , Lin Lili , Zhu Yue , Tan Langping , Yalikun Yisikandaer , Ouyang Wenhao , Ni Shuai , Li Xi , Hou Ting , Sun Wenjie , Chen Zhange 
Published: June 2022

Abstract
Background: PTC is the most common type of thyroid cancer and offers excellent prognosis. However, recurrence PTC remains relatively common, especially PTC with BRAF V600E mutation. PTC is often characterized by RET, RAS or BRAFmutations. RAS, RET and BRAF V600E mutations tend to be mutually exclusive. In this study, we investigated whether these oncogenic driver mutations could propose a molecular classification of PTC into distinct tumor immune microenvironment.
Methods: Surgical tissue samples from 252 patients with stage I-III PTC consecutively diagnosed between 07/2020 to 08/2021 at Sun Yat-sen Memorial Hospital (SYMH) were sequenced using a panel targeting 18 cancer-related genes. Clinical and genomic data from SYMH cohort was compared with 499 stage I-III PTC patients (PTCs) from TCGA.
Results: Based on the analysis of the genetic alteration profile from SYMH cohort, 252 PTCs can be classed into three major subgroups, BRAFV600E-(83.7%), RAS-(6.0%), and RET-(3.6%) driven PTCs. These three subgroups covered 93.2% of SYMH cohort and 77.6% in TCGA cohort. (Thyroid peroxidase) TPO status was strongly correlated with BRAF V600E (p=0.003), RET (p=0.005) mutations. Median age of RET- driven PTCs was lower than that of BRAFV600E-, RAS- driven PTCs (p=0.034), which was in concordance with TCGA cohort (p=0.0021). In both cohorts, prevalence of lymph node metastasis in RET-driven PTCs (SYMH, 88%; TCGA, 76%) was higher than that in RAS-(SYMH, 20%; TCGA, 21%) driven PTCs (SYMH, RET vs. RAS, P=0.018; TCGA RET vs. RAS, p &lt;0.001). The TPO positive rates in RET- (p=0.034) and RAS- (p &lt;0.01) driven PTCs were higher than BRAF V600E- driven PTCs in SYMH cohort. In TCGA cohort, RET-driven PTCs had longer disease-free survival (DFS) than RAS- driven PTCs, but not statistically significant. Tumor immune microenvironment study in TCGA cohort revealed a more anti-inflammatory tumor state for RAS-driven PTCs, with decreased levels of pro-inflammatory mediators DC cells, Eosinophils, M1 Macrophages, B cells, and CD4 memory T cells, and increased level of anti-inflammatory M2 macrophages. RAS-driven PTCs also had the decreased level of pro-inflammatory cytokines IL-1, IL-2, IL-12, IL-17, IL-18, IFN-γ, and TNF-α. In contrast, significantly increased level of tumor-infiltrating Tregs was observed in BRAFV600E -driven PTCs (p&lt;0.005). BRAF V600E - driven PTCs had higher degree of NKT cells infiltration than RAS-driven PTCs (p&lt;0.05).
Conclusion: PTCs can be classified into BRAF V600E-, or RAS-, or RET-driven subgroups with district clinicopathological features and tumor immune microenvironmental differences, which implication for clinical treatment decision.
Citation Format: Miaoyun Long, Yunfang Yu, Lili Lin, Yue Zhu, Langping Tan, Yisikandaer Yalikun, Wenhao Ouyang, Shuai Ni, Xi Li, Ting Hou, Wenjie Sun, Zhange Chen. Novelmolecular subtypes of papillary thyroid carcinoma (PTC) driven by BRAFV600E-,RAS- and RET-mutations linked to distinct clinicopathological features and tumor immune microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5265.