Mcl-1 downregulation enhances BCG treatment efficacy in bladder cancer by promoting macrophage polarization.

Background: Bacillus Calmette-Guérin (BCG) is the primary method of postoperative perfusion treatment for bladder cancer. The myeloid cell leukemia gene-1 (Mcl-1) is closely associated with the development of malignant tumors. Previous research by our group has demonstrated that downregulating Mcl-1 using shRNA can enhance the efficacy of BCG treatment in bladder cancer. This study aims to investigate the impact of Mcl-1 downregulation in combination with BCG treatment on bladder cancer, macrophage polarization, and the underlying mechanism of action, with the goal of reducing recurrence and metastasis in bladder cancer.

Methods: The GSE190529 dataset was analyzed to identify differential genes for enrichment analysis. The WGCNA algorithm was then employed to pinpoint gene modules closely associated with the Mcl-1 gene. The overlapping genes between these modules and the differentially expressed genes were subjected to enrichment analysis in GO and KEGG pathways to unveil crucial signaling pathways. In vitro experiments involved the co-culture of Raw264.7 macrophages and MB49 to establish a tumor microenvironment model, while in vivo experiments utilized an MNU-induced rat bladder cancer model. Various methods including Enzyme-Linked Immunosorbent Assay (ELISA), Western blot, immunofluorescence, HE staining, etc. were utilized to assess macrophage polarization and the expression of proteins linked to the ASK1/MKK7/JNK/cJUN signaling pathway.

Results: Bioinformatics analysis indicates that the therapeutic mechanism of Mcl-1 in BCG treatment for bladder cancer may be linked to the Mitogen-Activated Protein Kinase (MAPK) signaling pathway. Both in vivo and in vitro experiments have demonstrated that the combination of BCG treatment and Mcl-1shRNA intervention results in elevated expression of M1 markers (TNF-α, CD86, INOS) and reduced expression of M2 markers (IL-10, CD206, Arg-1). Moreover, there was a notable increase in protein levels of P-ASK1, P-MKK7, P-JNK, P-cJUN, and CX43, leading to a significant rise in the apoptosis rate of bladder cancer cells and diminished proliferation, migration, and invasion capabilities. The expression of these markers can be reversed by employing the JNK signaling pathway inhibitor SP600125.

Conclusion: Down-regulation of Mcl-1 promotes the polarization of macrophages towards the M1 type through activation of the ASK1/MKK7/JNK signaling pathway. This enhances intercellular communication and improves the efficacy of BCG in bladder cancer treatment.