Abstract B035: CXCL12 / CXCR4 signaling enhances and sustains migrating cancer stem cells via BMI1 in pancreatic ductal adenocarcinomas

Pancreatic cancer is a fatal disease and is one of the most aggressive and metastatic malignancies worldwide. The dissemination of tumor cells is the prerequisite of metastases and correlates with a loss of epithelial differentiation and the acquisition of a migratory phenotype, a hallmark of malignant tumor progression. Migrating cancer stem cells (miCSCs) characterized by CD133+ and CXCR4+ expression play a pivotal role in malignant tumor formation, have been reported to form the invasive front of the metastasis and in silico analysis showed that both CSCs and miCSCs are significantly upregulated in PDAC. However, the regulatory pattern maintaining these CSCs and especially miCSCs in PDAC remains widely elusive. Thus, this study further helps to unravel pathways responsible for maintenance of CSC (CD133+) and miCSC (CD133+ CXCR4+) population. To identify key signaling pathways responsible for both CSCs and miCSCs maintenance, we first generated a protein-protein interaction network using STRING database. Afterwards, we validated these signaling pathway(s) involved in aiding CSC and miCSC population by performing shRNA mediated knockdown of key signaling proteins in different patient-derived pancreatic cancer cell lines. Moreover, we interrogated the involvement of the tumor-stroma crosstalk in the regulation of these pathways by co-culturing tumor cells with pancreatic stellate cells. Protein-protein interaction network incorporating relevant factors involved in EMT, stemness, as well as SHH, NF-kB and AKT signaling pathway identified a strong link between the CXCL12/CXCR4 signaling axis and BMI1. Migration assay, sphere formation assay and western blot upon shRNA mediated knockdown of either CXCR4 and/or BMI1 ascertained BMI1 as a key player downstream of the CXCL12/CXCR4 axis to mechanistically effect both EMT and stemness. Pathway focused gene expression analysis as well as ELISA and immunofluorescence for CXCL12 and actin filaments, respectively, revealed the indispensable nature of tumor-stroma crosstalk on promoting CSC and miCSC population through the chemokine CXCL12. In addition, co-culture systems revealed that particularly pancreatic stellate cells play a significant role in maintaining both CSCs and miCSCs population as well as their characteristic phenotype including but not limited to chemotherapy resistance. Taken together, our results obtained in this study established mechanistically that the CXCL12/CXCR4 signaling pathway driven by tumor-stroma crosstalk not only enhances but also maintains both CSCs and miCSCs in pancreatic ductal adenocarcinomas through BMI1 ultimately promoting metastases and therapeutic resistance. Citation Format: Kanishka Tiwary, Anton Lahusen, Syeda Inaas, Stefanie Hauff, Karolin Walter, Alexander Kleger, Thomas Seufferlein, Bruno Sainz Jr., Patrick Christian Hermann. CXCL12 / CXCR4 signaling enhances and sustains migrating cancer stem cells via BMI1 in pancreatic ductal adenocarcinomas [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr B035.