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Background Y‐box binding protein 1 (YB1 or YBX1) plays a critical role in tumorigenesis and cancer progression. However, whether YB1 affects malignant transformation by modulating non‐coding RNAs remains largely unknown. This study aimed to investigate the relationship between YB1 and microRNAs and reveal the underlying mechanism by which YB1 impacts on tumor malignancy via miRNAs‐mediated regulatory network. Methods The biological functions of YB1 in hepatocellular carcinoma (HCC) cells were investigated by cell proliferation, wound healing, and transwell invasion assays. The miRNAs dysregulated by YB1 were screened by microarray analysis in HCC cell lines. The regulation of YB1 on miR‐205 and miR‐200b was determined by quantitative real‐time PCR, dual‐luciferase reporter assay, RNA immunoprecipitation, and pull‐down assay. The relationships of YB1, DGCR8, Dicer, TUT4, and TUT1 were identified by pull‐down and coimmunoprecipitation experiments. The cellular co‐localization of YB1, DGCR8, and Dicer were detected by immunofluorescent staining. The in vivo effect of YB1 on tumor metastasis was determined by injecting MHCC97H cells transduced with YB1 shRNA or shControl via the tail vein in nude BALB/c mice. The expression levels of epithelial to mesenchymal transition markers were detected by immunoblotting and immunohistochemistry assays. Results YB1 promoted HCC cell migration and tumor metastasis by regulating miR‐205/200b‒ZEB1 axis partially in a Snail‐independent manner. YB1 suppressed miR‐205 and miR‐200b maturation by interacting with the microprocessors DGCR8 and Dicer as well as TUT4 and TUT1 via the conserved cold shock domain. Subsequently, the downregulation of miR‐205 and miR‐200b enhanced ZEB1 expression, thus leading to increased cell migration and invasion. Furthermore, statistical analyses on gene expression data from HCC and normal liver tissues showed that YB1 expression was positively associated with ZEB1 expression and remarkably correlated with clinical prognosis. Conclusion This study reveals a previously undescribed mechanism by which YB1 promotes cancer progression by regulating the miR‐205/200b‒ZEB1 axis in HCC cells. Furthermore, these results highlight that YB1 may play biological functions via miRNAs‐mediated gene regulation, and it can serve as a potential therapeutic target in human cancers., YB1 regulates miR‐205/200b‐ZEB1 axis by inhibiting microRNA maturation.

It is widely accepted that redox reprogramming participates in malignant transformation of lung adenocarcinoma (LUAD). However, the source of excessive reactive oxygen species (ROS) and the downstream signaling regulatory mechanism are complicated and unintelligible. In the current study, we newly identified the aquaporin 3 (AQP3) as a LUAD oncogenic factor with capacity to transport exogenous hydrogen peroxide (H2O2) and increase intracellular ROS levels. Subsequently, we demonstrated that AQP3 was necessary for the facilitated diffusion of exogenous H2O2 in LUAD cells and that the AQP3‐dependent transport of H2O2 accelerated cell growth and inhibited rapamycin‐induced autophagy. Mechanistically, AQP3‐mediated H2O2 uptake increased intracellular ROS levels to inactivate PTEN and activate the AKT/mTOR pathway to subsequently inhibit autophagy and promote proliferation in LUAD cells. Finally, we suggested that AQP3 depletion retarded subcutaneous tumorigenesis in vivo and simultaneously decreased ROS levels and promoted autophagy. These findings underscore the importance of AQP3‐induced oxidative stress in malignant transformation and suggest a therapeutic target for LUAD., Aquaporin 3 (AQP3) is a lung adenocarcinoma (LUAD) oncogene with the capacity to transport exogenous hydrogen peroxide (H2O2) and increase intracellular ROS levels. The devitalized oxidation of PTEN by AQP3‐transported H2O2 induces the hyperactivation of the PI3K/AKT/mTOR pathway to subsequently inhibit autophagy and promote proliferation in LUAD cells.

Protein-metabolite interactions (PMIs) play important roles in various biological processes, especially in disease progression. However, due to the complexity of living cells, it is very difficult to identify specific PMIs. Herein, we chose one oncogenic factor, metadherin (MTDH), as a bait to identify its in vivo interacting metabolites in cancer cells. Cholesterol is an important metabolite and essential structural component of cell membranes. It could also drive several diseases including cancer. Interestingly, we found that cholesterol robustly interacted with MTDH and downregulated the expression of MTDH in cancer cells. Furthermore, MTDH disturbed metabolite alterations under cholesterol treatment in MTDH transduced cancer cells. Collectively, our results uncover an undescribed PMI where MTDH, as an oncogenic factor, might positively regulate cancer progression by interacting with cholesterol. This study interprets the theoretical basis of PMI-oriented cancer progression and targeting therapies in clinic.

Midkine (MDK), an extracellular growth factor, regulates signal transduction and cancer progression by interacting with receptors, and it can be internalized into the cytoplasm by endocytosis. However, its intracellular function and signaling regulation remain unclear. Here, we show that intracellular MDK interacts with LKB1 and STRAD to disrupt the LKB1-STRAD-Mo25 complex. Consequently, MDK decreases the activity of LKB1 to dampen both the basal and stress-induced activation of AMPK by glucose starvation or treatment of 2-DG. We also found that MDK accelerates cancer cell proliferation by inhibiting the activation of the LKB1-AMPK axis. In human cancers, compared to other well-known growth factors, MDK expression is most significantly upregulated in cancers, especially in liver, kidney and breast cancers, correlating with clinical outcomes and inversely correlating with PRKAA1 (encoding AMPKα1) expression and phosphorylated AMPK levels. Our study elucidates an inhibitory mechanism for AMPK activation, which is mediated by the intracellular MDK through disrupting the LKB1-STRAD-Mo25 complex.

Metabolite‐protein interactions (MPIs) play key roles in cancer metabolism. However, our current knowledge about MPIs in cancers remains limited due to the complexity of cancer cells. Herein, the authors construct an integrative MPI network and propose a MPI network based hepatocellular carcinoma (HCC) subtyping and mechanism exploration workflow. Based on the expressions of hub proteins on the MPI network, two prognosis‐distinctive HCC subtypes are identified. Meanwhile, multiple interdependent features of the poor prognostic subtype are observed, including hypoxia, DNA hypermethylation of metabolic pathways, fatty acid accumulation, immune pathway up‐regulation, and exhausted T‐cell infiltration. Notably, the immune pathway up‐regulation is probably induced by accumulated unsaturated fatty acids which are predicted to interact with multiple immune regulators like SRC and TGFB1. Moreover, based on tumor microenvironment compositions, the poor prognostic subtype is further divided into two sub‐populations showing remarkable differences in metabolism. The subtyping shows a strong consistency across multiple HCC cohorts including early‐stage HCC. Overall, the authors redefine robust HCC prognosis subtypes and identify potential MPIs linking metabolism to immune regulations, thus promoting understanding and clinical applications about HCC metabolism heterogeneity., The authors construct an integrative metabolite‐protein interaction (MPI) network and develop a MPI prediction model. The MPI network helps redefine robust hepatocellular carcinoma prognostic subtypes. The subtypes show remarkable differences in hypoxia, DNA methylation of metabolic enzymes, immune pathways, fatty acid accumulation as well as tumor microenvironment. Meanwhile, unsaturated fatty acids are potential links between the metabolism and immune regulations.

Elevated de novo lipogenesis (DNL) is considered to be a crucial factor in hepatocellular carcinoma (HCC) development. However, the molecular mechanism for its occurrence in HCC is still unclear. Herein, we identified ubiquitin-specific protease 22 (USP22) as a key regulator for de novo fatty acid synthesis, which directly interacts with, deubiquitinates and stabilizes PPARγ through K48-linked deubiquitination, and in turn, this stabilization increases ACC and ACLY transcription. In addition, we found that USP22 promoted the de novo synthesis of fatty acid labeling from glucose tracers. USP22-dysregulated de novo fatty acid synthesis contributes to HCC progression, but USP22 was functionality suppressed by inhibiting the expression of PPARγ, ACLY, or ACC in in vitro cell proliferation and in vivo tumorigenesis experiments. In HCC, USP22 expression positively correlates with PPARγ expression, and simultaneously, high expression of USP22 and PPARγ or USP22, ACC and ACLY is associated with a poor prognosis. Taken together, we identified a previously undescribed USP22-regulated lipogenesis molecular mechanism that involves the PPARγ-ACLY/ACC axis in HCC tumorigenesis and provide a rationale for therapeutic targeting of lipogenesis via USP22 inhibition.

E3 ubiquitin ligases play a critical role in cellular mechanisms and cancer progression. F-box protein is the core component of the SKP1-cullin 1-F-box (SCF)-type E3 ubiquitin ligase and directly binds to substrates by various specific domains. According to the specific domains, F-box proteins are further classified into three sub-families: 1) F-box with leucine rich amino acid repeats (FBXL); 2) F-box with WD 40 amino acid repeats (FBXW); 3) F-box only with uncharacterized domains (FBXO). Here, we summarize the substrates of F-box proteins, discuss the important molecular mechanism and emerging role of F-box proteins especially from the perspective of cancer development and progression. These findings will shed new light on malignant tumor progression mechanisms, and suggest the potential role of F-box proteins as cancer biomarkers and therapeutic targets for future cancer treatment.

Primary cilia are microtubule-based organelles that extend from nearly all vertebrate cells. Abnormal ciliogenesis and cilia length are suggested to be associated with hypertension and obesity as well as diseases such as Meckel-Gruber syndrome. Extracellular matrix (ECM), comprising cellular microenvironment, influences cell shape and proliferation. However, influence of ECM on cilia biogenesis has not been well studied. In this study we examined the effects of type I collagen (col I), the major component of ECM, on primary cilia growth. When cultured on collagen-coated dishes, confluent 3T3-L1 cells were found to exhibit fibroblast-like morphology, which was different from the cobblestone-like shape on non-coated dishes. The level of autophagy in the cells cultured on col I-coated dishes was attenuated compared with the cells cultured on non-coated dishes. The cilia of the cells cultured on col I-coated dishes became longer, accompanying increased expression of essential proteins for cilia assembly. Transfection of the siRNA targeting microtubule-associated protein light chain 3 (LC3) further enhanced the length of primary cilia, suggesting that col I positively regulated cilia growth through inhibition of autophagy. Histone deacetylase 6 (HDAC6), which was suggested as a mediator of autophagy in our previous study on primary cilia, was down-regulated with col I. 3T3-L1 cells treated with the siRNA against HDAC6 reduced the autophagy level and enhanced collagen-induced cilia elongation, implying that HDAC6 was involved in mediating autophagy. In conclusion, col I promotes cilia growth through repressing the HDAC-autophagy pathway that can be involved in the interaction between primary cilia and col I.

Silibinin is a major bioactive component of silymarin extracted from the milk thistle Silybum marianum. Silibinin has therapeutic potential for a wide variety of applications including anticancer, hepatoprotective and antiinflammatory medicines. There are studies reporting that silibinin has shown anti-bacterial effects, but its underlying mechanism has not yet been elucidated. In the present study, UVC inhibited growth of S. aurues in a dose-dependent manner and up-regulated production of reactive oxygen species (ROS). Silibinin treatment improved the survival of S. aureus in the presence of UVC. Interestingly, silibinin further enhanced the generation of ROS and activities of antioxidant enzymes (catalase (CAT) and glutathione peroxidase (GSH-PX)). To determine the role of ROS induced by silibinin, the scavengers (N-acetylcysteine (NAC), glutathione (GSH) and superoxide dismutase (SOD)) or donors (tBHP and H2O2) of ROS were used to treat the bacterial cells. The results showed that ROS scavengers down-regulated the protective effect of silibinin, while ROS donors up-regulated it. Therefore, ROS produced by silibinin protects S. aureus cells from UVC-induced cell death. Our findings revealed novel insights into the relationship between silibinin, bacteria and ROS. Elucidation of the relationship will contribute to the development of important applications for further use of natural products, particularly for therapeutic strategies for S. aureus-associated diseases.

Ultraviolet B (UVB) from sunlight is a major cause of cutaneous lesion. Silibinin, a traditional hepatic protectant, elicits protective effects against UVB-induced cellular damage. In A431 cells, the insulin-like growth factor-1 receptor (IGF-1R) was markedly up-regulated by UVB irradiation. The activation of the IGF-1R signalling pathways contributed to apoptosis of the cells rather than rescuing the cells from death. Up-regulated IGF-1R stimulated downstream mitogen-activated protein kinases (MAPKs), such as c-Jun N-terminal kinases (JNK) and extracellular signal-regulated protein kinases 1/2 (ERK1/2). The subsequent activation of caspase-8 and caspase-3 led to apoptosis. The activation of IGF-1R signalling pathways is the cause of A431 cell death. The pharmacological inhibitors and the small interfering RNA (siRNA) targeting IGF-1R suppressed the downstream activation of JNK/ERK-caspases to help the survival of the UVB-irradiated A431 cells. Indeed, silibinin treatment suppressed the IGF-1R-JNK/ERK pathways and thus protected the cells from UVB-induced apoptosis.

Ultraviolet B (UVB) is a major cause of skin inflammation, leading to skin damage. Our previous in vivo study revealed that a natural flavonoid silibinin had marked anti-inflammatory effect on UVB-exposed murine skin. UVB exposure caused reduced autophagy in epidermis while it promoted autophagy in dermis. Nevertheless, silibinin inhibited the inflammatory flux in the skin epidermis as well as dermis through the modulation of autophagy. In order to elucidate the underlying protective mechanisms of silibinin for UVB damage on skin, separate studies on epidermis and dermis are helpful. Derived from the normal tissue of the mouse, L929 cells are capable of representing some characteristics of dermal cells. UVB irradiation caused L929 cell apoptosis in a time- and dose-dependent manner. Ataxia-telangiectasia-mutated (ATM) protein and p53 were activated to cause cell apoptosis, accompanying upregulation of the autophagic flux. The pharmacological inhibition of ATM, p53 and autophagy or the transfection with autophagy-associated protein-targeted small interfering RNAs showed that the UVB-activated ATM-p53 axis and autophagy formed a positive feedback loop, which synergistically promoted cell apoptosis. Silibinin treatment simultaneously repressed the activation of ATM-p53 and autophagy and thereby protected UVB-irradiated L929 cells from apoptotic death.

Ultraviolet B (UVB) in the sun light is a major cause of skin damage, which accompanies complex alterations in irradiated skin cells, including DNA lesions, oxidative stress, inflammation and caspase activation. The protection against UVB damage requires multiple interruptions such as repair of the DNA lesions, scavenging of the reactive oxygen species (ROS), repression of the inflammation and others. Silibinin is suggested as an anti-UVB reagent, but the underlying mechanisms have not been fully elucidated. In this study, we found a role of autophagy in the anti-UVB effect of silibinin in A431 cells. Autophagy was reduced after UVB-irradiation while restored by silibinin through the suppression of the IGF-1R signalling pathway. The protective effect of silibinin in UVB-irradiated A431 cells was further enhanced by pre-treatment with an autophagy inducer, rapamycin, while it was reversed by an autophagy inhibitor, wortmannin, indicating that elevated autophagy contributed to the cell survival. Consistently, cell apoptosis was augmented by siRNAs targeting Beclin 1 and Atg5, supporting the hypothesis that autophagy induced by silibinin plays a protective role against UVB-induced epidermal apoptosis.