Tumor elastography and its association with cell-free tumor DNA in the plasma of breast tumor patients: a pilot study

Yi Hao; Wei Yang; Wenyi Zheng; Xiaona Chen; Hui Wang; Liang Zhao; Jinfeng Xu; Xia Guo

doi:10.21037/qims-20-443

Tumor elastography and its association with cell-free tumor DNA in the plasma of breast tumor patients: a pilot study

Quant Imaging Med Surg. 2021 Aug;11(8):3518-3534. doi: 10.21037/qims-20-443.

Authors

Yi Hao¹, Wei Yang², Wenyi Zheng^{2

3}, Xiaona Chen^{3

4}, Hui Wang^{1

5}, Liang Zhao^{1

5}, Jinfeng Xu^{6

7}, Xia Guo⁴

Affiliations

¹ Department of Ultrasound, South China Hospital of Shenzhen University, Shenzhen, China.
² Department of Ultrasound, Shenzhen Hospital, Southern Medical University, Shenzhen, China.
³ The Third School of Clinical Medicine, Southern Medical University, Guangzhou, China.
⁴ Shenzhen Key Laboratory of Viral Oncology, Center for Clinical Research and Innovation (CCRI), Shenzhen Hospital, Southern Medical University, Shenzhen, China.
⁵ Department of Ultrasound, Affiliated Tumor Hospital of Xinjiang Medical University, Urumqi, China.
⁶ Department of Ultrasound, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University, Shenzhen, China.
⁷ The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, China.

Abstract

Background: Breast tumor stiffness, which can be objectively and noninvasively evaluated by ultrasound elastography (UE), has been useful for the differentiation of benign and malignant breast lesions and the prediction of clinical outcomes. Liquid biopsy analyses, including cell-free tumor DNA (ctDNA), exhibit great potential for personalized treatment. This study aimed to investigate the correlations between the UE and ctDNA for early breast cancer diagnosis.

Methods: Breast tumor stiffness in 10 patients were assessed by shear wave elastography (SWE), and the ctDNA of eight collected plasma specimens with different tumor stiffness were analyzed by whole-genome sequencing (WGS). Subsequently, the distribution of carcinoma-associated fibroblasts (CAFs) was investigated by detecting the expression levels of alpha-smooth muscle actin (α-SMA) in tissues of breast lesions. We validated the function of discoidin domain receptor 2 (DDR2) in breast tumor CAFs by knockout of fibroblast activation protein (FAP) with different tumor stiffness during cancer progression in vitro and vivo.

Results: The UE estimates of tumor stiffness positively correlated with CAF-rich (α-SMA⁺) tumors (P<0.05). Copy number profiles and percent genome alterations were remarkably different between benign and malignant breast lesions. Somatic genomic alterations or structural variants of DDR2, ANTXRL, TPSG1, and TPSB2 genes were identified in ctDNA of plasma from breast lesions with high SWE values and an increase in the CAF content obtained from clinical samples. Deletion of FAP in breast tumor CAFs by CRISPR/Cas9-mediated gene knockout and decreased tumor stiffness resulted in downregulated expression of DDR2 (P<0.05), which in turn led to decreasing the tumor stiffness and carcinogenesis process in vitro and in vivo.

Conclusions: These results have established proof of principle that WGS analysis of ctDNA could complement current UE approaches to assess tumor stiffness changes for the early diagnosis and prognostic assessment of breast cancer.

Keywords: Breast cancer; cell-free tumor DNA (ctDNA); copy number variation (CNV); discoidin domain receptor 2 (DDR2); tumor stiffness.