Abstract P6-14-08: Epithelial/stromal cross talks that induce malignant transition of human ductal carcinoma in situ

Abstract Background: A large fraction of human DCIS (>50%) may not need the multimodality treatment options currently offered to all patients. More importantly, while we may be overtreating many, we cannot identify those most at risk for invasion/metastasis. Revealing the cellular and molecular mechanisms by which some DCIS remain indolent while others advance to invasive and metastatic breast cancers is currently a clinical unmet need. Methods: To address this gap, we developed the Mouse-INtraDuctal (MIND) model, by which patient-derived (PDX) DCIS epithelial cells are injected intraductally and allowed to progress naturally in mice. Single cell RNA-sequencing (scRNA-seq) was utilized to profile the DCIS epithelial and stroma cells in progressors vs. non-progressors. To distinguish between stromal (diploid) cells and tumor (aneuploid) cells, we calculated Copy Number Aberration (CNA) profiles from RNA using CopyKAT. Cell-type specific differential gene expression analysis of DCIS epithelial cells and microenvironment cell types in progressors and non-progressors was performed. We also predicted putative ligand:receptor interactions between the tumor cells and cell types in the microenvironment by CellPhoneDB. Results: Among 37 PDX DCIS MIND models followed for a median of 9 months, 20 (54%) grafted into 95 glands, showed in vivo invasive progression (progressed) while 17 (46%), injected into 107 glands, remained non-invasive (non-progressed). ScRNA-seq was performed on 13 DCIS samples including 10 progressors and 3 non-progressors. Aneuploid cells were further analyzed to identify deferentially expressed genes that were upregulated in progressors compared to non-progressors (log2 fold=1, FDR p< 0.05).. Notable genes included NEAT1, EIF4EBP1, SCGB2A2, TFF1 and TFF3 that were upregulated in the progressors. NEAT1, the core structural component of the paraspeckles, is frequently overexpressed in human cancers and its expression is correlated with worse survival in cancer patients. NEAT1 drives tumor progression by regulating genes involved in cellular growth, migration, invasion, metastasis, EMT, stemness, radio- and chemoresistance, supporting its role as a potential biomarker and therapeutic target. TFF1/TFF3 mRNAs show increased expression in metastatic breast cancers. EIF4EBP1 is located on chrom 8p11-p12 which is frequently amplified in breast cancer and is associated with poor clinical prognosis. Further analysis using Cancer Hallmarks identified mitotic spindle, interferon signaling, DNA repair, oxidative phosphorylation and P53 pathway among the top signatures that were upregulated in the progressors. CellPhoneDB identified expression of several receptor/ligand interactions including CD74/MIF involved in epithelial/stromal and stromal/stromal cross talks that may play a role in DCIS invasive progression. Conclusions: Future studies will validate our findings using patient DCIS samples with known long-term outcome and in vivo MIND models to further refine risk associated biomarkers for invasion/metastasis and to identify more effective treatments. Citation Format: Aditi Rastogi, Fariba Behbod, Nicholas Navin, Jerome Lin, Linheng Li, Hua Li, Andrew K. Godwin, Alastair M. Thompson, Timothy Fields, Yan Hong. Epithelial/stromal cross talks that induce malignant transition of human ductal carcinoma in situ. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-14-08.