# BCAR3 Hypomethylation as a Potential Diagnostic Marker for Thyroid Cancer and Its Mechanism via Promoting EMT and AKT/mTOR Pathway

## TL;DR

This study shows that BCAR3 hypomethylation helps identify thyroid cancer and promotes cancer growth through specific pathways, suggesting it could be a new diagnostic tool and treatment target.

## Contribution

The study identifies BCAR3 hypomethylation as a novel diagnostic biomarker and functional driver in thyroid cancer via AKT/mTOR and EMT mechanisms.

## Key findings

- BCAR3 is hypomethylated in thyroid cancer compared to benign nodules, with CpG_6 strongly linked to cancer risk.
- BCAR3 promotes cancer cell growth, migration, and invasion through AKT/mTOR activation and EMT.
- Rescue experiments with a PI3K activator partially restored BCAR3-induced effects.

## Abstract

Distinguishing malignant from benign thyroid nodules preoperatively remains a significant diagnostic challenge. This study investigated the role of a gene called BCAR3 in thyroid cancer. Using a large cohort of 793 clinical samples and cell experiments, we discovered that BCAR3 loses a specific regulatory mark (DNA methylation) in thyroid tumors, and we demonstrated that BCAR3 promotes tumor cell growth, migration, and invasion through the AKT/mTOR pathway and epithelial–mesenchymal transition. Therefore, measuring BCAR3 methylation has the potential to serve as a novel diagnostic biomarker, and BCAR3 itself represents a promising future therapeutic target for thyroid cancer.

Background: BCAR3 has been implicated in various cancers, yet its role in thyroid cancer (TC) remains unclear. This study aimed to investigate the methylation status, functional effects, and underlying mechanisms of BCAR3 in TC. Methods: BCAR3 methylation was analyzed using matrix-assisted laser desorption/ionization–time-of-flight (MALDI-TOF) mass spectrometry in 422 TC and 371 benign thyroid nodule samples. Expression levels were assessed via immunohistochemistry, qPCR, and Western blot. Functional assays including proliferation, migration, and invasion were performed after BCAR3 knockdown. Rescue experiments using a PI3K activator were conducted to examine pathway mechanisms. Results: BCAR3 was significantly hypomethylated in TC compared to benign tissues (p < 0.001), with CpG_6 most strongly associated with TC risk (odds ratio, OR = 1.73, p < 0.001). Notably, BCAR3 hypomethylation was more pronounced in cases with larger tumor size and advanced disease stage. Furthermore, BCAR3 methylation showed differential patterns across TC subtypes, with medullary thyroid carcinoma exhibiting the lowest methylation levels. BCAR3 expression was upregulated in TC tissues and cell lines (p < 0.05). Mechanistically, BCAR3 knockdown reduced phosphorylation of AKT/mTOR and altered expression of epithelial-to-mesenchymal transition (EMT) marker, characterized by an increase in E-cadherin and decreases in Vimentin and N-cadherin, and consequently suppressed proliferation, migration, and invasion (p < 0.05). Rescue experiments with a PI3K activator showed a trend towards restoration of these effects, although not to the level of the control groups. Conclusions: BCAR3 hypomethylation contributes to TC cells’ proliferation, migration, and invasion by promoting AKT/mTOR activation and EMT. These findings highlight the potential of BCAR3 methylation as both a biomarker and a therapeutic target in TC.