Abstract 4117: Adipsin promotes tumor progression in ESR1 mutant breast cancer cells
Authors: Malone Marie K. , Jin Kideok 
Published: September 2020

Abstract
ESR1 point mutations at ESR1 ligand-binding domain are frequently identified in metastatic tumors, cfDNA (Cell-free DNA), ctDNA (Circulating tumor DNA) and ptDNA (plasma tumor DNA) derived from ESR1 positive breast cancer patients treated SERMs, SERDs, and AIs. ESR1 mutations enhance ESR1 transcriptional activity in the absence of estrogen and induce estradiol independent growth as well as increase resistance to SERM or SERD in ESR1 mutant overexpressed cells. ESR1 mutations are found more frequently in cfDNA and tumor DNA from patients with metastatic disease compared to patients with primary tumor, Although SERM, SERD, AI, and CDK4/6 inhibitor therapies have demonstrated preclinical and clinical benefits for breast cancer with ESR1 mutations, the development of resistance remains a significant challenge and the detailed mechanisms and potential therapeutic targets in metastatic breast cancer with ESR1 point mutations is yet to be revealed.
Tumor and organ microenvironments are crucial for cancer progression and metastasis. Crosstalk between multiple non-malignant cell types in the microenvironments such as blood and lymphatic endothelial cells and cancer cells promotes tumor growth and metastasis. Possibly the anti-angiogenic and anti-lymphangiogenic therapies can be combined with each other for improved outcomes for patients.
In this study, we identified the secretion of Adipsin from two different genome-edited MCF-7 harboring Y537S and D538G ESR1 cells compared to wild-type cells using the Human Cytokine Array Q440 to quantitatively detect 440 human inflammatory factors, growth factors, chemokines, receptors, and cytokines simultaneously. We validated that the expression of Adipsin was highly upregulated in MCF-7-Y537S and D538G ESR1 mutant cells by real-time qRT-PCR and ELISA.
Interestingly, we observed that when cells were cultured in estrogen deprivation, the mRNA expression of the Adipsin was significantly increased in MCF-7-ESR1 mutant cells while the treatment of tamoxifen and fulvestrant abrogated the upregulation of Adipsin. These results suggest that Adipsin is an ER target gene. Since the cleavage of factor B by Adipsin results in the conversion of C3 to C3a, which binds to its cell surface receptor (C3aR), our data showed that the C3a production was significantly increased in ESR1 mutant cells compared to WT by ELISA. In addition, we found that C3aR expression was increased in ESR1 mutant cells. To elucidate that the C3aR signaling pathway promotes the proliferation of MCF-7-ESR1 mutant cells, we examined the ESR1 mutant cell viability using SB290157, C3aR inhibitor and found that ESR1 mutant cell growth was decreased in the treatment of SB290157. Furthermore, we found that apoptosis was significantly induced in ESR1 mutant cells compared to WT by Annexin V assay.
These findings implicate Adipsin signaling as a critical event in breast cancer metastasis with ESR1 mutations. Further, these studies suggest that Adipsin acts as a key regulator orchestrating breast cancer with ESR1 mutations. Therefore, we have provided evidence that supports the hypothesis that functional inhibition of the Adipsin signaling pathway has the potential to circumvent breast cancer metastasis.
Citation Format: Marie K. Malone, Kideok Jin. Adipsin promotes tumor progression in ESR1 mutant breast cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4117.