Updated publication reference for PubMed record(s): 30197755. High mortality rate of muscle-invasive bladder cancer (MIBC) and complexity of disease demand new multi-targeting treatment strategies. Targeting proliferating cell nuclear antigen (PCNA) with a peptide containing the AlkB homologue 2 PCNA interacting motif (APIM), is shown to impair multiple vital cellular stress responses and induce hypersensitivity against several chemotherapeutics in different pre-clinical models. This study examine the anti-cancer efficacy of the novel APIM-peptide drug when combined with cisplatin-based therapies (cisplatin, cisplatin/gemcitabine (GC) and methotrexate/vinblastine/adriamycin/cisplatin (MVAC)) in a panel of bladder cancer (BC) cells and with intravenous cisplatin-therapy in a rat MIBC-model. Furthermore, we explore the molecular mechanisms underlying the observed effects on a genomic, proteomic and metabolomic level using microarray, multiplexed inhibitor bead (MIB)-assay, and targeted mass spectrometric metabolite profiling. The APIM-peptide significantly increased the efficacy of all cisplatin-based therapies in all BC cell lines tested, including a cisplatin resistant cell line and reduced the tumor load in cisplatin treated MIBC-bearing rats. Genome and proteome analysis of APIM-peptide/cisplatin treated BC cells revealed reduced expression of multiple proteins frequently overexpressed in MIBC. Of notice, the EGFR/ERBB2, PI3K/Akt and MAPK signaling pathways and anti-apoptosis were downregulated. We suggest that the anti-cancer effect of the APIM-peptide is through the downregulation of several known oncogenic signaling pathways including anti-apoptosis. Together our results indicate that the APIM-peptide represents a potential improved treatment approach for patients with MIBC.