MSH2 Expression and Resistance to Cisplatin in Muscle-invasive Bladder Cancer: A Mix of Progress and Challenges

L3MBTL1, a polycomb protein, promotes Osimertinib acquired resistance through epigenetic regulation of DNA damage response in lung adenocarcinoma

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (EGFR-TKI) approved for patients with EGFR T790M resistance mutations as first- or second-line treatment of EGFR-positive patients. Resistance to Osimertinib will inevitably develop, and the underlying mechanisms are largely unknown. In this study, we discovered that acquired resistance to Osimertinib is associated with abnormal DNA damage response (DDR) in lung adenocarcinoma cells. We discovered that the polycomb protein Lethal(3) Malignant Brain Tumor-Like Protein 1 (L3MBTL1) regulates chromatin structure, thereby contributing to DDR and Osimertinib resistance. EGFR oncogene inhibition reduced L3MBTL1 ubiquitination while stabilizing its expression in Osimertinib-resistant cells. L3MBTL1 reduction and treatment with Osimertinib significantly inhibited DDR and proliferation of Osimertinib-resistant lung cancer cells in vitro and in vivo. L3MBTL1 binds throughout the genome and plays an important role in EGFR-TKI resistance. It also competes with 53BP1 for H4K20Me2 and inhibits the development of drug resistance in Osimertinib-resistant lung cancer cells in vitro and in vivo. Our findings suggest that L3MBTL1 inhibition is a novel approach to overcoming EGFR-TKI-acquired resistance.

MicroRNA-367-3p directly targets RAB23 and inhibits proliferation, migration and invasion of bladder cancer cells and increases cisplatin sensitivity

OBJECTIVES

This study investigated the biological role of miR-367-3p upregulation in bladder cancer and verified the mutual relation between miR-367-3p and RAB23.

MATERIALS AND METHODS

Expression levels of miR-367-3p were determined by RT-qPCR in bladder cancer cell lines and human bladder cancer tissues. The effects of miR-367-3p on proliferation, migration and invasion were evaluated by cell colony formation assays, wound healing assays and trans-well assays, respectively. The effects of miR-367-3p and RAB23 on cisplatin sensitivity of bladder cancer cells were assessed by CCK-8 assay. The expression of its target-RAB23 was determined by western blotting in T24, 5637. Plasmids used in dual-luciferase assays were constructed to confirm the action of miR-367-3p on downstream target-RAB23 in T24 cells. And also, the role of miR-367-3p in tumorigenesis was also confirmed in nude mouse models.

RESULTS

The downregulation of miR-367-3p was observed in human bladder cancer tissues. MiR-367-3p downregulation positively correlated with tumor stage and tumor grade. MiR-367-3p overexpression in T24, 5637 cells suppressed the proliferation, migration, and invasion of bladder cancer cells in vitro while decreasing IC50 values under T24 and 5637 cisplatin treatment conditions. RAB23 was shown to be upregulated in bladder cancer tissues and cell lines. MiR-367-3p directly bound to the 3' UTR of RAB23 in T24 cells. RAB23 was potentially accounted for the aforementioned functions of miR-367-3p. Tumor formation experiments in nude mouse models confirmed that overexpression of miR-367-3p could inhibit tumor growth and invasion in vivo.

CONCLUSIONS

miR-367-3p acts as a tumor suppressor in bladder cancer by downregulating RAB23 signaling. We conjecture that miR-367-3p-mediated downregulation of RAB23 expression may be a new therapeutic strategy for bladder cancer treatment.

Lnc-PTCHD4-AS inhibits gastric cancer through MSH2-MSH6 dimerization and ATM-p53-p21 activation

Conserved long non-coding RNAs (lncRNAs) have not thoroughly been studied in many cancers, including gastric cancer (GC). We have identified a novel lncRNA PTCHD4-AS which was highly conserved between humans and mice and naturally downregulated in GC cell lines and tissues. Notably, PTCHD4-AS was found to be transcriptionally induced by DNA damage agents and its upregulation led to cell cycle arrest at the G2/M phase, in parallel, it facilitated the cell apoptosis induced by cisplatin (CDDP) in GC. Mechanistically, PTCHD4-AS directly bound to the DNA mismatch repair protein MSH2-MSH6 dimer, and facilitated the binding of dimer to ATM, thereby promoting the expression of phosphorylated ATM, p53 and p21. Here we conclude that the upregulation of PTCHD4-AS inhibits proliferation and increases CDDP sensitivity of GC cells via binding with MSH2-MSH6 dimer, activating the ATM-p53-p21 pathway.

Analyzing the whole-transcriptome profiles of ncRNAs and predicting the competing endogenous RNA networks in cervical cancer cell lines with cisplatin resistance

Background

Cervical cancer (CC) is one of the most common malignant tumors in women. In order to identify the functional roles and the interaction between mRNA and non-coding RNA (ncRNA, including lncRNA, circRNA and miRNA) in CC cisplatin (DDP) resistance, the transcription profile analysis was performed and a RNA regulatory model of CC DDP resistance was proposed.

Methods

In this study, whole-transcriptome sequencing analysis was conducted to study the ncRNA and mRNA profiles of parental SiHa cells and DDP resistant SiHa/DDP cells. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed for pathway analysis based on the selected genes with significant differences in expression. Subsequently, ceRNA network analyses were conducted using the drug resistance-related genes and signal-transduction pathways by Cytoscape software. Furthermore, a ceRNA regulatory pathway, namely lncRNA-AC010198.2/hsa-miR-34b-3p/STC2, was selected by RT-qPCR validation and literature searching. Further validation was done by both dual-luciferase reporter gene assays and RNA pull-down assays. Besides that, the changes in gene expression and biological function were further studied by performing si-AC010198.2 transfection and DDP resistance analyses in the SiHa and SiHa/DDP cells, respectively.

Results

Using bioinformatics and dual-luciferase reporter gene analyses, we found that AC010198.2/miR-34b-3p/STC2 may be a key pathway for DDP resistance in CC cells. Significant differences in both downstream gene expression and the biological function assays including colony formation, migration efficiency and cell apoptosis were identified in AC010198.2 knockdown cells.

Conclusions

Our study will not only provide new markers and potential mechanism models for CC DDP resistance, but also discover novel targets for attenuating it.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02239-6.

SPHK1 contributes to cisplatin resistance in bladder cancer cells via the NONO/STAT3 axis

Sphingosine-1-phosphate (S1P) serves an important role in various physiological and pathophysiological processes, including the regulation of cell apoptosis, proliferation and survival. Sphingosine kinase 1 (SPHK1) is a lipid kinase that phosphorylates sphingosine to generate S1P. S1P has been proven to be positively correlated with chemotherapy resistance in breast cancer, colorectal carcinoma and non-small cell lung cancer. However, whether SPHK1 is involved in the development of cisplatin resistance remains to be elucidated. The present study aimed to identify the association between SPHK1 and chemoresistance in bladder cancer cells and to explore the therapeutic implications in patients with bladder cancer. Bladder cancer cell proliferation and apoptosis were determined using Cell Counting Kit-8 assays and flow cytometry, respectively. Apoptosis-related proteins were detected via western blotting. The results revealed that SPHK1 was positively correlated with cisplatin resistance in bladder cancer cells, exhibiting an antiapoptotic effect that was reflected by the downregulation of apoptosis-related proteins (Bax and cleaved caspase-3) and the upregulation of an antiapoptotic protein (Bcl-2) in SPHK1-overexpression cell lines. Suppression of SPHK1 by small interfering RNA or FTY-720 significantly reversed the antiapoptotic effect. A potential mechanism underlying SPHK1-induced cisplatin resistance and apoptosis inhibition may be activation of STAT3 via binding non-POU domain containing octamer binding. In conclusion, the present study suggested that SPHK1 displayed significant antiapoptotic effects in cisplatin-based treatment, thus may serve as a potential novel therapeutic target for the treatment for bladder cancer.

A novel prognostic biomarker for muscle invasive bladder urothelial carcinoma based on 11 DNA methylation signature

Muscle-invasive bladder urothelial carcinoma (MIBC) is a highly invasive cancer, which leads to prevalent recurrence and poor prognosis. Exploring the association of DNA methylation and the prognosis of MIBC will thus be of important value in clinical management and treatment. Bumphunter method and adaptive lasso regression were used to explore the relationship between different methylation regions (DMRs) and the prognosis of MIBC. Next, we constructed a risk prognosis model and validated this model. Moreover, the performance of this risk model was examined by using time-dependent receiver operating characteristic curve (ROC). We identified 58,449 different methylation sites and 490 different methylation regions. Among them, 11 DMRs were associated with the prognosis of MIBC through rigorous screening. Through the linear combination of 11 DMRs, a putative marker was developed, which can distinguish the survival risk in both the training dataset (HR = 2.58, 95% CI = (1.64, 4.05)) and the verification dataset (HR = 2.77, 95% CI = (1.25, 6.15)). Relatively high predictive values were observed from this model for training dataset (AUC = 0.791) and verification dataset (AUC = 0.668). Stratified analysis showed that the association was independent of gender. A nomogram was additionally generated to predict 5-year survival probability containing risk score and pathological stage. Its performance was evaluated by applying calibration curve. The methylation signature risk model based on 11 DMRs may be a reliable prognostic signature for MIBC, which provides new insights into development of individualized therapy for MIBC.

Identification and validation of poor prognosis immunoevasive subtype of muscle-invasive bladder cancer with tumor-infiltrating podoplanin+ cell abundance

The choice of chemo- or immuno-therapy for muscle-invasive bladder cancer (MIBC) patients remains contentious. Podoplanin is newly identified as an immune checkpoint which intrigues us to explore the clinical significance and immunoregulatory role of tumor-infiltrating podoplanin⁺ cells (PDPN⁺ cells) in MIBC. A retrospective analysis of 259 MIBC patients from Zhongshan Hospital (n = 141) and Shanghai Cancer Center (n = 118) was conducted. A total of 406 MIBC patients from TCGA database were enrolled to investigate the relationship between PDPN and molecular characterization. We found that tumor-infiltrating PDPN⁺ cell abundance indicated an inferior overall survival and recurrence-free survival. pT2 MIBC patients with PDPN⁺ cell low infiltration could benefit more from adjuvant chemotherapy (ACT). Increased PDPN⁺ cell infiltration was associated with diminished GZMB and TNF-α expression while correlated with expanded PD-1, PD-L1, LAG-3 and TIM-3 expression and tumor-promoting regulatory T cell and M2 macrophage infiltration. Tumors with high PDPN mRNA expression mainly presented luminal-infiltrated and basal-squamous subtypes (2017 TCGA classification) or stroma-rich and Ba/Sq subtypes (consensus classification). Elevated PDPN mRNA expression was associated with less FGFR3 activation signature and more T-cell-inflamed signature and EGFR activation signature. In conclusion, tumor-infiltrating PDPN⁺ cells could be applied as an independent prognosticator for clinical outcome and a predictive biomarker for suboptimal ACT responsiveness, which was also associated with immunosuppressive contexture infiltration. Intratumoral PDPN expression had a correlation with MIBC molecular classification and therapy-related signatures. The novel immune checkpoint PDPN should be considered as a possible immunotherapeutic target for MIBC.

Targeting the Immune system and Epigenetic Landscape of Urological Tumors

In the last years, we have witnessed remarkable advances in targeted therapies for cancer patients. There is a growing effort to either replace or reduce the dose of unspecific, systemic (chemo)therapies, given the associated short- and long-term side effects, by introducing more specific targeted therapies as single or combination agents. Due to the well-known implications of the immune system and epigenetic landscape in modulating cancer development, both have been explored as potential targets in several malignancies, including those affecting the genitourinary tract. As the immune system function is also epigenetically regulated, there is rationale for combining both strategies. However, this is still rather underexplored, namely in urological tumors. We aim to briefly review the use of immune therapies in prostate, kidney, bladder, and testicular cancer, and further describe studies providing supporting evidence on their combination with epigenetic-based therapies.