LAUSR

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that can stimulate cellular proliferation in multiple tumors. Our previous data indicates genetic deletion of MIF results in T1 stage arrest in the N-Butyl-N-(4-hydroxybutyl) nitrosamine (BBN) induced bladder cancer model. Similarly, pharmacological inhibition of MIF results in lower stage tumors and reduced bladder weights when given therapeutically. CD74 is a human leukocyte antigen class II trafficking and processing protein that also functions as an extracellular receptor for MIF. Additionally, CD74 complexes with CD44 to act as the cognate MIF receptor complex, and upregulation of CD74 has been noted in high grade bladder cancer. We hypothesized CD74 would be upregulated in malignant bladder cancer cell lines, and knockout of CD74 would reduce bladder cancer tumorigenesis in the murine BBN model. The objectives of this study were to determine the effect of CD74 knockout on development and progression of urothelial cell carcinoma; as well as evaluate expression of the putative MIF signaling axis in BCa cell lines. BCa cell lines HTB-9, HTB-5, RT-4, T24 and HT-1376 and benign urothelial UROtsa cells were analyzed for MIF, CD74, and CD44 expression via quantitative PCR or western blot to assess expression of the MIF signaling axis. CD74 and CD44 expression by q-PCR were dramatically elevated in BCa cell lines vs. benign cell lines. Protein levels of CD74 and CD44 were elevated in multiple cell lines as well. MIF expression levels did not change between cell lines. To ascertain differences in BCa tumorigeneis, WT C57Bl/6J mice or CD74-/- mice were given 0.05% BBN in the drinking water for 22 weeks. Bladders were weighed and evaluated for pathologic staging by histology. After exposure to BBN, bladders from CD74-/- mice had a 33% reduction in weight vs. WT bladders (p=.062). Pathological analysis revealed lower stage tumors in bladders of CD74-/- mice (33% incidence; 6.7% pTa, 0% pTis, 6.7% pT1, 20% pT2, 6.7% pT3) as compared to bladders of WT mice (81.3% incidence; 0% pTa, 6.3% pTis, 25% pT1, 12.5% pT2, 37.5% pT3), which was a statistically significant reduction in tumor stage. Lower tumor stage correlated significantly with the CD74-/- genotype (p=0.02, Fisher9s Exact Test). These data suggest CD74 likely mediates a portion of the effects of MIF in BCa, raising the possibility of both CD74 dependent, and independent MIF signaling pathways. Citation Format: Justin Penticuff, Sambantham Shanmugam, Joshua Warrick, Brian Chase, Erika Abbott, Benjamin L. Woolbright, John A. Taylor. Targeting the MIF receptor CD74 in bladder cancer tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3560.