Abstract 3073: Dickkopf1 as a potential therapeutic target in highly aggressive breast cancers

Abstract Background: Triple-negative breast cancer (TNBC) and inflammatory breast cancer (IBC) are aggressive and lethal breast cancer subtypes, largely due to the absence of targeted therapies and insufficient understanding of the mechanisms driving metastasis and immune evasion. The glycoprotein Dickkopf-1 (DKK1) inhibits the WNT pathway and has been reported to enhance angiogenesis, metastasis, and invasion in breast cancer. We hypothesized that elevated serum DKK1 expression in IBC patients correlates with poor patient outcomes and that inhibiting DKK1 expression reduces proliferation and stemness in breast cancer cell lines. Methods: We used the GOBO online tool (http://co.bmc.lu.se/gobo) to analyze gene expressions in breast cancer patients and performed a western blot to check the expression of DKK1 in a panel of TNBC and IBC cell lines. Next, as DKK1 is a secreted protein, we quantified its levels in serum samples from 176 IBC patients from MD Anderson using ELISA. To investigate DKK1’s biological role in TNBC and IBC, we performed in vitro cell viability, clonogenic, mammosphere formation, CD44+/CD24-/low flow cytometry, and Western blot analyses. Results: Using the GOBO datasets, we retrospectively analyzed DKK1 expression in breast tumors and observed that the mean DKK1 expression was higher in basal tumors (most likely to be TNBC) and HER2+ subtypes than in the other subtypes or normal tissue and cell lines. The DKK1 expression was higher in most of the TNBC and IBC cell lines as compared to the normal breast MCF-7 cells. For serum samples, the median age of patients was 52.5 years (range, 23-78 years), 75.0% were non-TNBC, and 25.0% were TNBC. The disease stage was III in 71.6% and IV in 28.4%, and the nuclear grade was 1 or 2 in 30.5% and 3 in 69.5%. High DKK1-expressing patients (categorized using median expression) showed a high risk of developing metastases (p=0.039), breast cancer-specific mortality (p=0.0183), and shorter overall survival (p=0.0267) compared to low DKK1-expressing patients, confirming literature findings and suggesting that DKK1 is likely to act as a metastasis or tumor promoter in breast cancer. shRNA- and CRISPR-based knockdown/knockout of DKK1 significantly reduced viability, clonogenic capability, mammosphere formation capability, and CD44+ and CD24-/low subpopulations in the MDA-MB-231 and SUM149 TNBC/IBC cell lines. DKK1 knockout showed loss of AKT S473 phosphorylation but no effect on beta-catenin expression in SUM149 IBC cells, suggesting beta-catenin-independent signaling. Conclusions and future prospects: DKK1 could be a clinically significant biomarker with implications for diagnosis and therapeutic targeting in TNBC and IBC. We are now assessing DKK1 inhibition in a high DKK1-expressing genetically engineered mouse model. Additional studies may clarify how DKK1 regulates stemness and metastasis in TNBC and IBC at the molecular level. Citation Format: Mohd Mughees, Jian Wang, Wendy A. Woodward, Megumi Kai, MDACC IBC Team, Sharon H. Giordano, Chandra Bartholomeusz. Dickkopf1 as a potential therapeutic target in highly aggressive breast cancers abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3073.