LAUSR

e16601 Background: We previously showed that loss of PTEN by quantitative multiplex immunofluorescence (qIF) is associated with relapse after prostatectomy. Low expression of TTP, which modulates the NF-kB pathway and inflammation, is prognostic for lethal PrCa after surgery. We also showed, with this assay, that low CD8+ density is a poor prognostic marker. We hypothesized that co-loss of these independent cell signaling regulators leads to poorer outcomes, and low TTP is associated with a modified tumor immune microenvironment. Methods: qIF was performed on tissue microarrays from a cohort treated by radical prostatectomy (N = 128). PTEN and TTP expression intensity was measured continuously at a cell-by-cell level and summarized per patient using binary thresholds. Immune marker (CD3, CD8, PD-L1, PD-1, FOXP3) density (positive cells/area) was evaluated in glands and stroma. Median time to biochemical recurrence (BCR) and metastasis (MFS) was estimated using Kaplan Meier method and log rank test summarized associations between expression and time to event outcomes. Wilcoxon test assessed the association of biomarker status and immune marker density. Results: Of 128 patients with a median follow-up of 14.6 years, 67 (52%) had BCR. 102 had staining for PTEN, 103 for TTP and 86 for both. Key findings are detailed in Table. PTEN and TTP co-loss was associated with the shortest time to BCR and worst MFS. TTP-low tumors had an immune infiltrate deplete of CD8 (p = 0.0004) and PD-1 (p = 0.0001) expressing cells. No significant differences in immune markers were noted by PTEN status. Conclusions: Co-loss of regulators of inflammation and cell cycling is associated with incremental risk of relapse in localized PrCa. Loss of TTP is associated with a diminished effector T cell infiltrate and may be a modifier towards a ‘cold’ PrCa immune microenvironment. Table: Clinical outcomes by biomarker status [Table: see text]