Language：Japanese   Publisher：International Journal of Molecular Sciences  

Recently, immune checkpoint inhibitors (ICIs) and cabozantinib, a tyrosine kinase inhibitor (TKI), have been used to treat renal cell carcinoma (RCC); the combination of these agents has become a standard treatment for RCC. TKIs generally target vascular endothelial growth factor. However, cabozantinib is characterized by its targeting of MET. Therefore, cabozantinib can be used as a late-line therapy for TKI-resistant RCC. According to data from The Cancer Genome Atlas (TCGA), heat shock transcription factor 4 (HSF4) expression is higher in RCC tissues than in normal renal tissues. HSF4 binds to the MET promoter in colorectal carcinoma to enhance MET expression and promote tumor progression. However, the functional role of HSF4 in RCC is unclear. We performed loss-of-function assays of HSF4, and our results showed that HSF4 knockdown in RCC cells significantly decreased cell functions. Moreover, MET expression was decreased in HSF4-knockdown cells but elevated in sunitinib-resistant RCC cells. The combination of cabozantinib and HSF4 knockdown reduced cell proliferation in sunitinib-resistant cells more than each monotherapy alone. Furthermore, HSF4 knockdown combined with an ICI showed synergistic suppression of tumor growth in vivo. Overall, our strategy involving HSF4 knockdown may enhance the efficacy of existing therapies, such as cabozantinib and ICIs.

DOI： 10.3390/ijms26041776

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PubMed

Language：Japanese   Publisher：BMC Cancer  

Background: Chemotherapy including cisplatin is recommended for the treatment of advanced bladder cancer, but its effectiveness is limited due to the acquisition of drug resistance. Although several mechanisms of cisplatin resistance have been reported, there are still many unknowns, and treatment of cisplatin-resistant bladder cancer remains difficult. Accordingly, in this study, we aimed to identify and characterize microRNAs involved in cisplatin resistance. Methods: Small RNA sequencing analysis was performed to search for microRNAs related to cisplatin resistance. The identified microRNAs were then characterized using gain-of-function studies, sensitivity analysis, target gene analysis, and cellular assays. Results: We identified miR-424-5p as a candidate microRNA that was downregulated in cisplatin-resistant strains compared with parental strains. Notably, in gain-of-function studies, miR-424-5p suppressed the proliferative ability of cisplatin-resistant bladder cancer (CDDP-R BC). Furthermore, miR-424-5p restored sensitivity to cisplatin. RNA sequence analysis revealed seven candidate genes targeted by this microRNA. Among them, cyclin E1 (CCNE1) was chosen for subsequent analyses because its expression was upregulated in cisplatin-resistant cells compared with parental cells and because recent studies have shown that CCNE1 amplification is synthetic lethal with PKMYT1 kinase inhibition. Therefore, we performed functional analysis using the PKMYT1 inhibitor RP-6306 and demonstrated that RP-6306 inhibited cell growth through suppression of mitotic entry and restored cisplatin sensitivity in CDDP-R BC. Conclusions: Overall, our findings provided insights into the development of novel therapeutic strategies for CDDP-R BC.

DOI： 10.1186/s12885-024-13109-5

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PubMed

Language：Japanese   Publisher：Molecular Oncology  

Gemcitabine plus cisplatin (GC) combination chemotherapy is the primary treatment for advanced bladder cancer (BC) with unresectable or metastatic disease. However, most cases develop resistance to this therapy. We investigated whether drug resistance could be targeted through metabolic reprogramming therapies. Metabolomics analyses in our lab's gemcitabine- and cisplatin-resistant cell lines revealed increased phosphoglycerate dehydrogenase (PHGDH) expression in gemcitabine-resistant cells compared with parental cells. Isocitrate dehydrogenase 2 (IDH2) gain of function stabilized hypoxia-inducible factor1α (HIF1α) expression, stimulating aerobic glycolysis. In gemcitabine-resistant cells, elevated fumaric acid suppressed prolyl hydroxylase domain-containing protein 2/Egl nine homolog 1 (PHD2) and stabilized HIF1α expression. PHGDH downregulation or inhibition in gemcitabine-resistant BC cells inhibited their proliferation, migration, and invasion. Cisplatin-resistant cells showed elevated fatty acid metabolism, upregulating fatty acid synthase (FASN) downstream of tyrosine kinase. Using the fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor erdafitinib, we inhibited malonyl-CoA production, which is crucial for fatty acid synthesis, and thereby suppressed upregulated HIF1α expression. Combination treatment with NCT503 and erdafitinib synergistically suppressed tumor cell proliferation and induced apoptosis in vitro and in vivo. Understanding these mechanisms could enable innovative BC therapeutic strategies to be developed.

DOI： 10.1002/1878-0261.13684

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PubMed

Language：Japanese   Publisher：International Journal of Molecular Sciences  

Bladder cancer (BC) is a common genitourinary malignancy that exhibits silent morbidity and high mortality rates because of a lack of diagnostic markers and limited effective treatments. Here, we evaluated the role of the lncRNA brain cytoplasmic RNA 1 (BCYRN1) in BC. We performed loss-of-function assays to examine the effects of BCYRN1 downregulation in T24 and BOY BC cells. We found that BCYRN1 downregulation significantly inhibited the proliferation, migration, invasion, and three-dimensional spheroid formation ability and induced apoptosis in BC cells. Additionally, gene set enrichment analysis (GSEA) using RNA sequences from tumor fractions showed that BCYRN1 downregulation decreased the expression of mRNAs associated with the cell cycle. These findings were supported by observations of G<inf>2</inf>/M arrest in flow cytometry assays. Finally, we examined the expression of serum exosomal BCYRN1 as a biomarker. Clinically, BCYRN1 expression in serum exosomes from patients with BC (n = 31) was significantly higher than that in healthy donors (n = 19; mean difference: 4.1-fold higher, p < 0.01). Moreover, in patients who had undergone complete resection of BC, serum exosomal BCYRN1 levels were significantly decreased (n = 8). Thus, serum exosomal BCYRN1 may be a promising diagnostic marker and therapeutic target in patients with BC.

DOI： 10.3390/ijms25115955

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PubMed