FOXM1-Mediated Regulation of Reactive Oxygen Species and Radioresistance in Oral Squamous Cell Carcinoma Cells

Regulation of Exosomal miR-320d/FAM49B Axis by Guanylate Binding Protein 5 Promotes Cell Growth and Tumor Progression in Oral Squamous Cell Carcinoma

BACKGROUND

Guanylate binding protein 5 (GBP5) and exosomal miRNAs are involved in tumor progression. While several studies reveal the connection between GBP5 and exosomes for immune response and infection, this relationship in cancer, particularly in oral squamous cell carcinoma (OSCC), remains unexplored.

METHODS

The exosomal miRNA extracted from the cells was analyzed using next-generation sequencing. Bioinformatic tools were used to predict exosomal miRNA target genes. OSCC cell growth was verified by colony formation, cell viability, and cell cycle analysis. The Cancer Genome Atlas database was used to inspect the prognosis of OSCC patients.

RESULTS

Our results showed that OSCC cells treated with exosomes from GBP5-silenced OSCC cells reduced colony formation. Also, 56 differentially expressed exosomal miRNAs were found in GBP5-silenced OSCC cells compared to scrambled OSCC cells. Among them, exosomal miR-320d exhibited the highest negative correlation with GBP5 in OSCC patients. High GBP5/low miR-320d co-expression was linked to reduced disease-free survival (DFS) in patients with OSCC. Interestingly, the inhibitory effect of GBP5-silenced exosomes on OSCC cell growth was reversed by miR-320d inhibitors. Moreover, five miR-320d target genes were predicted, and only Family with Sequence Similarity 49, Member B (FAM49B) showed a negative correlation with miR-320d. A decreased level of FAM49B was found in OSCC cells treated with exosomes derived from GBP5-silenced OSCC cells, while the decreased level of FAM49B was reversed by miR-320d inhibitors. Silencing FAM49B and GBP5-silenced exosomes enhanced the cytotoxicity of paclitaxel. FAM49B was abundantly expressed in tumor tissues, and high FAM49B/low miR-320d and high GBP5/high FAM49B co-expression were linked to reduced DFS of OSCC patients.

CONCLUSION

Our study suggests that GBP5 downregulated exosomal miR-320d may trigger FAM49B expression and facilitate OSCC tumor growth and progression.

CPT1A mediates radiation sensitivity in colorectal cancer

The prevalence and mortality rates of colorectal cancer (CRC) are increasing worldwide. Radiation resistance hinders radiotherapy, a standard treatment for advanced CRC, leading to local recurrence and metastasis. Elucidating the molecular mechanisms underlying radioresistance in CRC is critical to enhance therapeutic efficacy and patient outcomes. Bioinformatic analysis and tumour tissue examination were conducted to investigate the CPT1A mRNA and protein levels in CRC and their correlation with radiotherapy efficacy. Furthermore, lentiviral overexpression and CRISPR/Cas9 lentiviral vectors, along with in vitro and in vivo radiation experiments, were used to explore the effect of CPT1A on radiosensitivity. Additionally, transcriptomic sequencing, molecular biology experiments, and bioinformatic analyses were employed to elucidate the molecular mechanisms by which CPT1A regulates radiosensitivity. CPT1A was significantly downregulated in CRC and negatively correlated with responsiveness to neoadjuvant radiotherapy. Functional studies suggested that CPT1A mediates radiosensitivity, influencing reactive oxygen species (ROS) scavenging and DNA damage response. Transcriptomic and molecular analyses highlighted the involvement of the peroxisomal pathway. Mechanistic exploration revealed that CPT1A downregulates the FOXM1-SOD1/SOD2/CAT axis, moderating cellular ROS levels after irradiation and enhancing radiosensitivity. CPT1A downregulation contributes to radioresistance in CRC by augmenting the FOXM1-mediated antioxidant response. Thus, CPT1A is a potential biomarker of radiosensitivity and a novel target for overcoming radioresistance, offering a future direction to enhance CRC radiotherapy.

Rho GTPase activating protein 11A promotes tongue squamous cell carcinoma proliferation and is a transcriptional target of forkhead box M1

Background/purpose

Rho GTPase activating protein 11A (ARHGAP11A) can facilitate GTP hydrolysis in RhoA. The functions of ARHGAP11A in oral squamous cell carcinoma (OSCC) have not yet been explored. This study aimed to investigate the expression profile of ARHGAP11A in OSCC, its correlation with patient prognosis, its effect on cell-cycle progression, and the mechanisms by which it is dysregulated.

Materials and methods

Bioinformatics analysis was conducted using data from The Cancer Genome Atlas-Head and Neck Squamous Cell Carcinoma (TCGA-HNSC). Lentiviruses carrying ARHGAP11A shRNAs were employed to determine the effects of ARHGAP11A knockdown on tumor cell proliferation and cell-cycle progression. Dual-luciferase reporter assays were utilized to examine how FOXM1 transcriptionally regulates ARHGAP11A expression.

Results

ARHGAP11A upregulation was associated with unfavorable overall survival (OS) in patients with TSCC (HR: 2.142, 95%CI: 1.224-3.749, P = 0.007), but not in patients with OSCC of sites other than the tongue. ARHGAP11A knockdown inhibited the proliferation of TSCC cells in vitro and in vivo, and induced G1 phase arrest. ARHGAP11A knockdown increased GTP-RhoA but decreased p-RB levels, while it did not affect the total expression of RhoA and RB. ARHGAP11A knockdown increased p27 and decreased cyclin E1 expression. ARHGAP11A is transcriptionally activated by FOXM1 via multiple FOXM1 binding sites in the promoter regions in TSCC cells.

Conclusion

This study revealed the oncogenic role of ARHGAP11A in TSCC, highlighting its impact on cell-cycle control and tumor proliferation. Furthermore, the regulatory relationship between FOXM1 and ARHGAP11A provides new insights into the transcriptional networks in TSCC.

RNA methylation, homologous recombination repair and therapeutic resistance

Homologous recombination (HR) repair of DNA double-strand breaks (DSBs) is critical for maintaining genomic integrity and stability. Defects in HR increase the risk of tumorigenesis. However, many human tumors exhibit enhanced HR repair capabilities, consequently endowing tumor cells with resistance to DNA-damaging chemotherapy and radiotherapy. This review summarizes the role of RNA methylation in HR repair and therapeutic resistance in human tumors. We also analyzed the interactions between RNA methylation and other HR-modulating modifications including histone acetylation, histone deacetylation, ubiquitination, deubiquitination, protein arginine methylation, and gene transcription. This review proposes that targeting RNA methylation is a promising approach to overcoming HR-mediated therapeutic resistance.