miRNAs as potential regulators of mTOR pathway in renal cell carcinoma

Deciphering potential molecular mechanisms in clear cell renal cell carcinoma based on the ubiquitin-conjugating enzyme E2 related genes: Identifying UBE2C correlates to infiltration of regulatory T cells

Renal clear cell carcinoma (ccRCC) is a highly aggressive and common form of kidney cancer, with limited treatment options for advanced stages. Recent studies have highlighted the importance of the ubiquitin-proteasome system in tumor progression, particularly the role of ubiquitin-conjugating enzyme E2 (UBE2) family members. However, the prognostic significance of UBE2-related genes (UBE2RGs) in ccRCC remains unclear. In this study, bulk RNA-sequencing and single-cell RNA-sequencing data from ccRCC patients were retrieved from the Cancer Genome Atlas and Gene Expression Omnibus databases. Differential expression analysis was performed to identify UBE2RGs associated with ccRCC. A combination of 10 machine learning methods was applied to develop an optimal prognostic model, and its predictive performance was evaluated using area under the curve (AUC) values for 1-, 3-, and 5-year overall survival (OS) in both training and validation cohorts. Functional enrichment analyses of gene ontology and Kyoto Encyclopedia of Genes and Genomes were conducted to explore the biological pathways involved. Correlation analysis was conducted to investigate the association between the risk score and tumor mutational burden (TMB) and immune cell infiltration. Immunotherapy and chemotherapy sensitivity were assessed by immunophenoscore and tumor immune, dysfunction, and exclusion scores to identify potential predictive significance. In vitro, knockdown of the key gene UBE2C in 786-O cells by specific small interfering RNA to validate its impact on apoptosis, migration, cell cycle, migration, invasion of tumor cells, and induction of regulatory T cells (Tregs). Analysis of sc-RNA revealed that UBE2 activity was significantly upregulated in malignant cells, suggesting its role in tumor progression. A three-gene prognostic model comprising UBE2C, UBE2D3, and UBE2T was constructed by Lasoo Cox regression and demonstrated robust predictive accuracy, with AUC values of 0.745, 0.766, and 0.771 for 1-, 3-, and 5-year survival, respectively. The model was validated as an independent prognostic factor in ccRCC. Patients in the high-risk group had a worse prognosis, higher TMB scores, and low responsiveness to immunotherapy. Additionally, immune infiltration and chemotherapy sensitivity analyses revealed that UBE2RGs are associated with various immune cells and drugs, suggesting that UBE2RGs could be a potential therapeutic target for ccRCC. In vitro experiments confirmed that the reduction of UBE2C led to an increase in apoptosis rate, as well as a decrease in tumor cell invasion and metastasis abilities. Additionally, si-UBE2C cells reduced the release of the cytokine Transforming Growth Factor-beta 1 (TGF-β1), leading to a decreased ratio of Tregs in the co-culture system. This study presents a novel three-gene prognostic model based on UBE2RGs that demonstrates significant predictive value for OS, immunotherapy, and chemotherapy in ccRCC patients. The findings underscore the potential of UBE2 family members as biomarkers and therapeutic targets in ccRCC, warranting further investigation in prospective clinical trials.

Silencing of the chemokine CXC receptor 4 (CXCR4) hampers cancer progression and increases cisplatin (DDP)-sensitivity in clear cell renal cell carcinoma (ccRCC)

Aberrant expression of the chemokine CXC receptor 4 (CXCR4) is closely associated with cancer progression and drug-resistance in multiple cancers, and we first investigated the role of CXCR4 in regulating cancer pathogenesis and cisplatin (DDP)-resistance in clear cell renal cell carcinoma (ccRCC) in the present study. Here, we identified that CXCR4 acted as an oncogene to promote cancer progression and genetically silencing of CXCR4 increased cisplatin (DDP)-sensitivity in ccRCC in vitro and in vivo. Functionally, analysis from the clinical and cellular data indicated that CXCR4 was significantly upregulated in ccRCC tissues and cells, compared to their normal counterparts. Next, the loss-of-function experiments validated that knock-down of CXCR4 suppressed cell proliferation, invasion, migration and epithelial-mesenchymal transition (EMT) in ccRCC cells, while CXCR4 overexpression had opposite effects on the above cellular functions. Consistently, the xenograft tumor-bearing mice models were established, and the results supported that knock-down of CXCR4 inhibited tumor growth and the expression levels of Ki67 protein in vivo. In addition, the ccRCC cells were exposed to DDP treatment, and we surprisingly found that upregulation of CXCR4 increased DDP-resistance in ccRCC cells, and conversely, CXCR4 ablation sensitized ccRCC cells to DDP stimulation. Taken together, we concluded that CXCR4 ablation hindered cancer progression and enhanced DDP-sensitivity in ccRCC, and the present study identified a novel therapeutic biomarker for ccRCC.

LAT1 and ASCT2 Related microRNAs as Potential New Therapeutic Agents against Colorectal Cancer Progression

The development and progression of colorectal cancer (CRC) have been associated with genetic and epigenetic alterations and more recently with changes in cell metabolism. Amino acid transporters are key players in tumor development, and it is described that tumor cells upregulate some AA transporters in order to support the increased amino acid (AA) intake to sustain the tumor additional needs for tumor growth and proliferation through the activation of several signaling pathways. LAT1 and ASCT2 are two AA transporters involved in the regulation of the mTOR pathway that has been reported as upregulated in CRC. Some attempts have been made in order to develop therapeutic approaches to target these AA transporters, however none have reached the clinical setting so far. MiRNA-based therapies have been gaining increasing attention from pharmaceutical companies and now several miRNA-based drugs are currently in clinical trials with promising results. In this review we combine a bioinformatic approach with a literature review in order to identify a miRNA profile with the potential to target both LAT1 and ASCT2 with potential to be used as a therapeutic approach against CRC.

Everolimus resistance in clear cell renal cell carcinoma: miRNA-101 and HIF-2α as molecular triggers?

Aim: The majority of clear cell renal cell carcinoma patients develop resistance to mTOR inhibitors. Materials & methods: As an in vitro model four cell lines were used: HKC-8, 786- O, RCC-FG-2 and an everolimus-resistant cell line (786-OR) established during this study. The quantification of miRNA-101 and HIF-2α mRNA levels was assessed by real-time PCR. Results: We observed a significant decrease of miRNA-101 intracellular levels in 786-OR. However, this miRNA presented higher extracellular levels. Additionally, we found a significant increase of HIF-2α in 786-OR. Conclusion: The circulating levels of miRNA-101 may be a potential biomarker of anti-mTOR therapy response and resistance prediction. Moreover, the resistance to mTOR inhibitors seems to be related with the overexpression of HIF-2α.

FABP5 regulates the proliferation of clear cell renal cell carcinoma cells via the PI3K/AKT signaling pathway

Clear cell renal cell carcinoma (ccRCC) has been associated with one of the highest mortality rates among all cancers. Fatty acid binding proteins (FABPs) are 14‑15 kDa proteins that are highly abundant in the cytosol of most tissues. FABP5, a member of the FABP family, has been observed to promote tumor cell growth in numerous cancer types. In order to investigate the function of FABP5 in ccRCC cells in the present study, RNA sequencing data from The Cancer Genome Atlas were analyzed to determine the expression levels of FABP5 in ccRCC patient samples. Survival and Cox regression analyses were performed to measure the association between FABP5 expression and clinicopathological features of patients with ccRCC. Subsequent in vitro experiments downregulated or overexpressed FABP5 in Caki‑1 and 786O ccRCC cells using lentiviral vectors to evaluate cell proliferation ability, and a xenograft transplantation model was established to examine the effect of FABP5 on tumorigenesis in vivo. The results demonstrated that FABP5 expression was significantly upregulated in samples from patients with ccRCC when compared with normal tissue samples. High FABP5 expression was also significantly correlated with tumor and metastasis classifications and predicted poor survival in patients with ccRCC. In ccRCC cells, silencing of FABP5 significantly inhibited cell proliferation, while overexpression of FABP5 promoted cell proliferation when compared to the respective controls. In addition, treatment with the phosphatidylinositol‑4,5‑bisphosphate 3‑kinase (PI3K)/AKT inhibitor, LY294002, attenuated the pro‑proliferative effects of exogenous FABP5 expression in Caki‑1 and 786O cells. This indicated that the PI3K/AKT signaling pathway may be partially involved in the FABP5‑mediated increase in ccRCC cell proliferation. Furthermore, FABP5 was observed to regulate tumor growth in nude mice in vivo. In conclusion, the results of the present study suggest that FABP5 may exert a pro‑proliferative role in ccRCC and may be associated with malignant progression and tumorigenesis.