Background: Increasing evidence indicates that deregulation of microRNAs (miRNAs) is involved in tumorigenesis. Downregulation of microRNA-503 has been observed in various types of diseases, including cancer. However, the biological function of miR-503 in hepatocellular carcinoma (HCC) is still largely unknown. In this study we aimed to elucidate the prognostic implications of miR-503 in HCC and its pathophysiologic role. Methods: Quantitative reverse transcriptase polymerase chain reaction was used to evaluate miR-503 expression in HCC tissues and cell lines. Western blotting was performed to evaluate the expression of the miR-503 target genes. In vivo and in vitro assays were performed to evaluate the function of miR-503 in HCC. Luciferase reporter assay was employed to validate the miR-503 target genes. Results: miR-503 was frequently downregulated in HCC cell lines and tissues. Low expression levels of miR-503 were associated with enhanced malignant potential such as portal vein tumor thrombi, histologic grade, TNM stage, AFP level and poor prognosis. Multivariate analysis indicated that miR-503 downregulation was significantly associated with worse overall survival of HCC patients. Functional studies showed miR-503 suppressed the proliferation of HCC cells by induction of G1 phase arrest through Rb-E2F signaling pathways, and thus may function as a tumor suppressor. Further investigation characterized two cell cycle-related molecules, cyclin D3 and E2F3, as the direct miR-503 targets. Conclusion: Our data highlight an important role for miR-503 in cell cycle regulation and in the molecular etiology of HCC, and implicate the potential application of miR-503 in prognosis prediction and miRNA-based HCC therapy.

Liquid–liquid Phase Separation (LLPS) of proteins and nucleic acids has emerged as a new paradigm in the study of cellular activities. It drives the formation of liquid-like condensates containing biomolecules in the absence of membrane structures in living cells. In addition, typical membrane-less condensates such as nuclear speckles, stress granules and cell signaling clusters play important roles in various cellular activities, including regulation of transcription, cellular stress response and signal transduction. Previous studies highlighted the biophysical and biochemical principles underlying the formation of these liquid condensates. The studies also showed how these principles determine the molecular properties, LLPS behavior, and composition of liquid condensates. While the basic rules driving LLPS are continuously being uncovered, their function in cellular activities is still unclear, especially within a pathological context. Therefore, the present review summarizes the recent progress made on the existing roles of LLPS in cancer, including cancer-related signaling pathways, transcription regulation and maintenance of genome stability. Additionally, the review briefly introduces the basic rules of LLPS, and cellular signaling that potentially plays a role in cancer, including pathways relevant to immune responses and autophagy.

The tumor microenvironment (TME) has attracted attention owing to its essential role in tumor initiation, progression, and metastasis. With the emergence of immunotherapies for various cancers, and their high efficacy, an understanding of the TME in gastric cancer (GC) is critical. The aim of this study was to investigate the effect of various components within the GC TME, and to identify mechanisms that exhibit potential as therapeutic targets. The ESTIMATE algorithm was used to quantify immune and stromal components in GC samples, whose clinicopathological significance and relationship with predicted outcomes were explored. Low tumor mutational burden and high M2 macrophage infiltration, which are considered immune suppressive characteristics and may be responsible for unfavorable prognoses in GC, were observed in the high stromal group (HR = 1.585; 95% CI, 1.112–2.259; P = 0.009). Furthermore, weighted correlation network, differential expression, and univariate Cox analyses were used, along with machine learning methods (LASSO and SVM-RFE), to reveal genome-wide immune phenotypic correlations. Eight stromal-relevant genes cluster (FSTL1, RAB31, FBN1, ANTXR1, LRRC32, CTSK, COL5A2, and ENG) were identified as adverse prognostic factors in GC. Finally, using a combination of TIMER database and single-sample gene set enrichment analyses, we found that the identified genes potentially contribute to macrophage recruitment and polarization of tumor-associated macrophages. These findings provide a different perspective into the immune microenvironment and indicate potential prognostic and therapeutic targets for GC immunotherapies.

Carcinoma associated fibroblasts (CAFs), an important component of tumor microenvironment, are capable of enhancing tumor cells invasion and migration through initiation of epithelial–mesenchymal transition (EMT). MRC-5 fibroblasts are one of the CAFs expressing alpha-smooth muscle actin. It is ascertained that medium conditioned by MRC-5 fibroblasts stimulate motility and invasion of breast cancer cells. However, its role in hepatocellular carcinoma (HCC) is less clear. The aim of our study was to investigate the effect of MRC-5-CM on HCC and explore the underlying mechanisms. Using a combination of techniques, the role of MRC-5-CM in HCC was evaluated. We determined that MRC-5-CM induced the non-classical EMT in Bel-7402 and MHCC-LM3 cell lines. Initiation of the non-classical EMT was mainly via quintessential redistribution of α-, β- and γ-catenin, P120 catenin, E-cadherin, and N-cadherin, rather than up-regulation of typical EMT-related transcription factors (i.e., Snail, Twist1, ZEB-1 and ZEB2). We also found that MRC-5-CM potentiated both the migration and invasion of Bel-7402 and MHCC-LM3 cells in mesenchymal movement mode through activation of the α6, β3, β4, β7 integrin/FAK pathway and upregulation of MMP2. The flow cytometric analysis showed that MRC-5-CM induced G1 phase arrest in Bel-7402 cells with a concomitant reduction of S phase cells. In contrast, MRC-5-CM induced S phase arrest in MHCC-LM3 cells with a concomitant reduction of cells in the G2/M phase. MRC-5-CM also inhibited apoptosis in Bel-7402 cells while inducing apoptosis in MHCC-LM3 cells. Collectively, MRC-5-CM promoted HCC cell motility and invasiveness through initiation of the non-classical EMT, including redistribution of α-, β- and γ-catenin, P120 catenin, E-cadherin, and N-cadherin, activation of the integrin/FAK pathway, and upregulation of MMP2. Hence, MRC-5-CM exerted distinct roles in Bel-7402 and MHCC-LM3 cell viability by regulating cyclins, cyclin dependent kinases (CDKs), CDK inhibitors (CKIs), Bcl-2 family proteins and other unknown mechanosensors.

Background The epithelial-to-mesenchymal transition (EMT) and mesenchymal-to-epithelial transition (MET) play pivotal roles in metastasis of epithelial cancers. The distinction between them has shed new light on the molecular mechanisms of tumor metastasis. Recently, tumor microenvironment (TM) has been identified as one of the most potent inducers of EMT and MET. TM is characterized by its complexity and flexibility. The purpose of this study was to ascertain the exact effect of each distinct TM component on the evolution hepatocellular carcinoma (HCC) metastasis. Methods Two different cell culture models were used. The HCC cell line Bel-7402 was co-cultured with the normal liver cell line HL-7702 or with the retinal vascular endothelial cell line RF/6A in double-layer six-well plates, imitating the direct interaction between tumor-host cells and tumor cells. Bel-7402 was also cultured in the conditioned medium (CM) of the human lung fibroblast cell line MRC-5, HL-7702 or RF/6A, imitating an indirect interaction. Integrin β1, β3, β4, β7, laminin β3, E-cadherin and Snail levels were measured by quantitative RT-PCR in tumor sepecimens from 42 resected HCC. Results We found that Bel-7402 cells co-cultured with HL-7702 or RF/6A cells were induced to undergo MET. The expression of E-cadherin, α-catenin and β-catenin was up-regulated, accompanied with a strengthened E-cadherin/catenin complex on the membrane of co-cultured Bel-7402 cells. Consequently, the invasion and migration ability of cells was declined. Conversely, Bel-7402 cells cultured in conditioned medium from MRC-5 cells underwent an EMT-like transformation as the cells became elongated with increased invasion and migration ability. Furthermore, we demonstrated that HL-7702 cells could generally inhibit the tumorigenicity and viability of Bel-7402 cells. We also found that integrin β1 expression was negatively associated with capsular formation, and that integrin β4 expression was negatively associated with CK19 expression. Conclusion Our findings highlight the strong influences exerted by TM on tumor progression through EMT and MET by impacting the expression of adhesion molecules, including the E-cadherin/catenin complex, laminins and integrins.

N6-Methyladenosine (m⁶A) is the most common RNA internal modification in eukaryotic cells. Its regulatory effects at the post-transcriptional level on both messenger RNAs (mRNAs) and noncoding RNAs have been widely studied; these include alternative splicing, stability, translation efficiency, nucleus export, and degradation. m⁶A modification is implicated in a series of physiological and pathological activities, such as embryonic stem cell differentiation, immunoregulation, adipogenesis, and cancer development. Recently, the significance of m⁶A methylation has been identified in both viral hepatitis and non-alcohol fatty liver disease (NAFLD), which are major risk factors in the development of hepatocellular carcinoma (HCC). Given the high incidence and mortality rate of HCC worldwide, it is of great importance to elucidate the mechanisms underlying HCC initiation and progression. m⁶A as an emerging research focus has great potential to facilitate the understanding of HCC, particularly from an etiological perspective. Thus, in this review, we summarize recent progress in understanding m⁶A modification related to viral hepatitis, NAFLD, and HCC, including their mechanisms and clinical applications.