PLAC8 Correlates with Prognosis, Immune Infiltration, and T Cell Exhaustion in Breast Cancer

Abstract

Background: Lysosomal protein placenta-specific 8 (PLAC8) with abundant cysteine, also referred to as onzin, participates in numerous cancers, and its effect is greatly determined by the cellular and tumor microenvironment (TME). Ourstudy focused on investigating the prognostic significance of PLAC8 and examined the association between PLAC8, immune infiltration, and T cells function in multiple malignancies comprehensively, particularly in breast cancer (BRCA).Methods: PLAC8 expression in various malignancies was analyzed using TIMER. PrognoScan, Kaplan-Meier Plotter, and GEPIA2 were utilized to explore the significance of PLAC8 in prognostic prediction. Moreover, PLAC8 functions were systematically analyzed through cancerSEA. Additionally, TISIDB, TIMER, and GEPIA2 were also employed for analyzing the associations among PLAC8, immune infiltration, related gene marker sets, and clinical stages. Finally, PLAC8 and its co-expressed genes biological process and KEGG were analyzed. Results: PLAC8 expression decreased in most malignancies and was related to poor prognosis in BRCA. PLAC8 significantly affected the survival of BRCA with ER status – array, PR status – IHC, HER2 status – array, Intrinsic subtype, Grade, and Pietenpol subtype. Increased PLAC8 expression positively correlated with the increased immune infiltration levels within immune cells and many functional T cells (such as exhausted T cells). In BRCA cells, PLAC8 functional phenotypesshowed a negative correlation with invasion, metastasis, apoptosis, DNA damage, and DNA repair. Besides, PD-1, TIM-3, TIGIT, LAG3, and GZMB, critical genes of exhausted T cells, interacted with PLAC8. Further analysis indicated that PLAC8 was related to T cell activation, proliferation and adhesion of leukocytes,adaptive immune response, cell adhesion molecules (CAMs), cytotoxicity-mediated by natural killer cells, and the NF-kappa B signal transduction pathway.Conclusion:PLAC8 is a prognostic indicator in pan-cancers, especially BRCA. Elevated PLAC8 level could significantly enhance immune infiltration in CD4+ T cells, CD8+ T cells, and functional T cells. Additionally, PLAC8 was tightly associatedwith T cell exhaustion which possibly enhances the latterwithin BRCA. PLAC8 expression determination might help in prognosis, and modulation of PLAC8level within exhausted T cells, a novel approach for optimizing the therapeutic effect of immunotherapy on BRCA cases.