Abstract 2421: Elucidation of CSF1 autocrine signaling mediated by mutant p53 in metastatic esophageal carcinoma
Authors: Efe Gizem , Tang Qiaosi , Cruz-Acuna Ricardo , Suzuki Kensuke , Sugiura Kensuke , Gabre Joel , Sachdeva Uma , Gu Wei , Prives Carol L. , Rustgi Anil K. 
Published: June 2022

Abstract
Introduction: Esophageal cancer is a highly aggressive cancer and is the 6th leading cause of cancer mortality worldwide, with esophageal squamous cell carcinoma (ESCC) being the most prevalent subtype. Mutations in the tumor suppressor TP53 (human homolog of mouse Trp53), which encodes p53, are detected frequently in ESCC that in turn correlate with poor survival and high metastatic rates. We have conducted RNA-Seq and cytokine array on primary and metastatic tumor cells harvested from our mouse models with Trp53R172H mutation. We have identified colony stimulating factor 1 (CSF1) to be upregulated. Our data suggest the existence of CSF1-CSF1R autocrine signaling, and its functional relationship to the promotion of metastasis in ESCC, recognizing that CSF1 is known to be critical in the polarization of macrophages to M2-like tumor associated macrophages. Our goal is to investigate the role and mediators of CSF1/CSF1R signaling by which missense TP53 mutations can promote invasion and lung metastasis in ESCC.
Methods: We used L2-Cre; LSL-Trp53R172H; Rosa26LSL-YFP mice and 2D/3D cell culture systems to model ESCC. To assess the functional role of CSF1, we established a CRISPR approach to knockout Csf1in our cells introducing ribonucleoprotein (RNP) Cas9/gRNA complex via nucleofection and overexpressed Csf1. We also utilized a small molecule inhibitor of CSF1R, GW2580. We conducted TCGA analysis on the association of distinct TP53 mutations with ESCC prognosis and Csf1 expression, as well as Csf1 expression in metastatic tumors. Based on this, we modeled ESCC by introducing various DNA contact and conformational p53 mutations into esophageal cells with wildtype p53 via base editing.
Results: TCGA data and our models demonstrate that metastatic ESCCs have increased Csf1 expression compared to primary tumors and it is dependent upon p53 mutation status. In addition, analysis of ESCC patients’ datasets reveal that specific p53 mutations are associated with markedly differential overall survival rates and Csf1 expression. We show that Csf1 function is related to tumor cell invasion, primary tumor growth and metastatic tumor burden in a mutant p53 background. We have identified both bromodomain and extra-terminal motif (BET) protein BRD4 and transcription factor nuclear factor kappa B (NF-κB) as proteins that interact with Trp53R172H at higher levels compared to wildtype p53 to induce Csf1 expression. In addition, inhibition of CSF1R with small molecule GW2580 downregulated JAK-STAT3 pathway mediating epithelial-mesenchymal transition (EMT) mechanisms that would contribute to increased invasiveness and metastasis.
Conclusion: We have demonstrated novel roles and mechanisms of mutant p53-dependent CSF1-CSF1R autocrine signaling and its mediators in promoting lung metastasis from ESCC that may be applicable to other squamous cell cancers. We believe this mechanism can be targeted therapeutically.
Citation Format: Gizem Efe, Qiaosi Tang, Ricardo Cruz-Acuna, Kensuke Suzuki, Kensuke Sugiura, Joel Gabre, Uma Sachdeva, Wei Gu, Carol L. Prives, Anil K. Rustgi. Elucidation of CSF1 autocrine signaling mediated by mutant p53 in metastatic esophageal carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2421.