Modification of Mcl-1 alternative splicing induces apoptosis and suppresses tumor proliferation in gastric cancer

FBXW7 affects autophagy through MCL1 in oral squamous cell carcinoma

BACKGROUND

Oral cancer is associated with high risk of morbidity and mortality. However, effective treatment for oral cancer is urgently required in clinics. In this study, we aimed to determine whether F-box/WD repeat-containing protein 7 (FBXW7), an essential tumor suppressor gene, can regulate autophagy and improve the prognosis in oral squamous cell carcinoma (OSCC).

METHODS

mRNA levels of FBXW7 and myeloid cell leukemia 1 (MCL-1) in OSCC tissues and adjacent normal tissues were measured by qRT-PCR. FBXW7 and MCL-1 were overexpressed in OSCC cell line using lentivirus containing FBXW7 and MCL-1, respectively. Protein expression was determined by Western blot.

RESULTS

The mRNA and protein levels of FBXW7 were decreased in patients with OSCC, whereas the mRNA and protein levels of MCL-1 were increased. Moreover, the mRNA coding for autophagy proteins was reduced in patients with OSCC. Additionally, it was found that overexpression of FBXW7 significantly reduced MCL-1 expression and upregulated autophagy-related proteins, including Beclin1, autophagy related 7, and microtubule-associated protein light chain 3.

CONCLUSION

Our results suggest that FBXW7 affects autophagy through MCL1 in OSCC.

LncRNA MIAT Promotes Spinal Cord Injury Recovery in Rats by Regulating RBFOX2-Mediated Alternative Splicing of MCL-1

LncRNA myocardial infarction-associated transcript (MIAT) alleviates acute spinal cord injury (ASCI)-induced neuronal cell apoptosis, but the specific mechanism of it involved in regulating SCI progression needs further exploration. Here, a SCI rat model was established, followed by administration with adenovirus-mediated MIAT overexpression vector (Ad-MIAT) alone or together with Ad-RBFOX2 (RNA binding fox-1 homolog 2). The data indicated that MIAT overexpression promoted motor function recovery, improved morphology of injured tissues, and restrained neuron loss and cell apoptosis in SCI rats. Then, PC-12 cells were treated with H₂O₂ to induce cell injury. And highly expressed MIAT suppressed H₂O₂-caused decrease in cell viability and increase in cell apoptosis. MIAT stabilized RBFOX2 protein expression by binding to RBFOX2, thereby promoting RBFOX2-induced upregulation of anti-apoptotic MCL-1L (myeloid cell leukemia sequence 1) and reduction of pro-apoptotic MCL-1S. And silencing RBFOX2 in vitro blocked the inhibitory effect of MIAT on cell apoptosis. Moreover, MCL-1-specific steric-blocking oligonucleotides (SBOs) were used to transfer the MCL-1 pre-mRNA splicing pattern from MCL-1L to MCL-1S. SBOs reversed the protection effect of RBFOX2 overexpression on H₂O₂-induced cell injury. Furthermore, overexpression of MCL-1L instead of MCL-1S facilitated autophagy activation in H₂O₂-stimulated cells. Interestingly, co-overexpression of MIAT and RBFOX2 had a better promoting effect on SCI recovery. In conclusion, MIAT mitigated SCI by promoting RBFOX2-mediated alternative splicing of MCL-1. Our findings might provide a promising therapeutic target for SCI.

Identification of prognostic alternative splicing signature in gastric cancer

Background

Aberrant alternative splicing (AS) events could be viewed as prognostic indicators in a large number of malignancies. This study aims to identify prognostic AS events, illuminate the function of the splicing variants biomarkers and provide reliable evidence for formulating public health strategies for gastric cancer (GC) surveillance.

Methods

RNA-Seq data, clinical information and percent spliced in (PSI) values were available in The cancer genome atlas (TCGA) and TCGA SpliceSeq data portal. A three-step regression method was conducted to identify prognostic AS events and construct multi-AS-based signatures. The associations between prognostic AS events and splicing factors were also investigated.

Results

We identified a total of 1,318 survival-related AS events in GC, parent genes of which were implicated in numerous oncogenic pathways. The final prognostic signatures stratified by seven types of AS events or not stratified performed well in risk prediction for GC patients. Moreover, five signatures based on AA, AD, AT, ES and RI events function as independent prognostic indicators after multivariate adjustment of other clinical variables. Splicing network also showed marked correlation between the expression of splicing factors and PSI value of AS events in GC patients.

Conclusion

Our findings provide a landscape of AS events and regulatory network in GC, indicating that AS events might serve as prognostic biomarkers and therapeutic targets for GC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13690-022-00894-3.

Overexpression of chaperonin containing TCP1 subunit 7 has diagnostic and prognostic value for hepatocellular carcinoma

Chaperonin containing TCP1 subunit 7 (CCT7) regulates the expression of many tumor-related proteins. We investigated the diagnostic and prognostic value of CCT7 expression for hepatocellular carcinoma (HCC). In datasets from The Cancer Genome Atlas and the Gene Expression Omnibus, CCT7 mRNA levels were greater in HCC tissues than adjacent normal tissues, and these results were validated using immunohistochemistry. In patients with early-stage disease and low alpha-fetoprotein expression, CCT7 expression was still higher in HCC tissues than normal tissues. Receiver operating characteristic curve analyses indicated that CCT7 expression had better diagnostic value than alpha-fetoprotein for HCC patients with early-stage disease and low alpha-fetoprotein expression. The positive predictive value of CCT7 expression was higher than that of alpha-fetoprotein expression. Higher CCT7 mRNA and protein levels were independent risk factors for poorer overall and recurrence-free survival in HCC patients. Greater methylation of the CpG site cg19515186 was associated with better overall survival in HCC patients. Genes co-expressed with CCT7 were upregulated in HCC and associated with poorer overall survival. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes and Gene Set Enrichment Analyses demonstrated that CCT7 expression correlated with spliceosome signaling. These findings demonstrate that CCT7 has diagnostic and prognostic value for HCC.

ID09, A Newly-Designed Tubulin Inhibitor, Regulating the Proliferation, Migration, EMT Process and Apoptosis of Oral Squamous Cell Carcinoma

Microtubules, a major target in oral squamous cell carcinoma (OSCC) chemotherapy, contribute to multiple malignant biological behaviors, including proliferation, migration, and epithelial-mesenchymal transition (EMT). Surpassing traditional tubulin inhibitors, ID09 emerges with brilliant solubility, photostability, and drug-sensitivity in multidrug-resistant cells. Its anti-tumor effects have been briefly verified in lung adenocarcinoma and hepatocellular carcinoma. However, whether OSCC is sensitive to ID09 and the potential mechanisms remain ambiguous, which are research purposes this study aimed to achieve. Various approaches were applied, including clone formation assay, flow cytometry, wound healing assay, Transwell assay, cell counting kit-8 assay, Western blot, qRT-PCR, and in vivo experiment. The experimental results revealed that ID09 not only contributed to cell cycle arrest, reduced migration, and reversed EMT, but accelerated mitochondria-initiated apoptosis. Remarkably, Western blot detected diminishment in expression of Mcl-1 due to the deactivation of Ras-Erk pathway, resulting in ID09-induced apoptosis, proliferation and migration suppression, which could be offset by Erk1/2 phosphorylation agonist Ro 67-7476. This study initially explored the essential role Mcl-1 played and the regulatory effect of Ras-Erk pathway in anti-cancer process triggered by tubulin inhibitor, broadening clinical horizon of tubulin inhibitors in oral squamous cell carcinoma chemotherapy application.

The interplay between apoptosis and cellular senescence: Bcl-2 family proteins as targets for cancer therapy

Cell death by apoptosis and permanent cell cycle arrest by senescence serve as barriers to the development of cancer. Chemotherapeutic agents not only induce apoptosis, they can also induce senescence known as therapy-induced senescence (TIS). There are, however, controversies whether TIS improves or worsens therapeutic outcome. Unlike apoptosis, which permanently removes cancer cells, senescent cells are metabolically active, and can contribute to tumor progression and relapse. If senescent cells are not cleared by the immune system or if cancer cells escape senescence, they may acquire resistance to apoptotic stimuli and become highly aggressive. Thus, there have been significant efforts in developing senolytics, drugs that target these pro-survival molecules to eliminate senescent cells. The anti-apoptotic Bcl-2 family proteins not only protect against cell death by apoptosis, but they also allow senescent cells to survive. While combining senolytics with chemotherapeutic drugs is an attractive approach, there are also limitations. Moreover, members of the Bcl-2 family have distinct effects on apoptosis and senescence. The purpose of this review article is to discuss recent literatures on how members of the Bcl-2 family orchestrate the interplay between apoptosis and senescence, and the challenges and progress in targeting these Bcl-2 family proteins for cancer therapy.