The FBXW2-MSX2-SOX2 axis regulates stem cell property and drug resistance of cancer cells.

SOX2 is a key transcription factor that plays critical roles in maintaining stem cell property and conferring drug resistance. However, the underlying mechanisms by which SOX2 level is precisely regulated remain elusive. Here we report that MLN4924, also known as pevonedistat, a small-molecule inhibitor of neddylation currently in phase II clinical trials, down-regulates SOX2 expression via causing accumulation of MSX2, a known transcription repressor of SOX2 expression. Mechanistic characterization revealed that MSX2 is a substrate of FBXW2 E3 ligase. FBXW2 binds to MSX2 and promotes MSX2 ubiquitylation and degradation. Likewise, FBXW2 overexpression shortens the protein half-life of MSX2, whereas FBXW2 knockdown extends it. We further identified hypoxia as a stress condition that induces VRK2 kinase to facilitate MSX2-FBXW2 binding and FBXW2-mediated MSX2 ubiquitylation and degradation, leading to SOX2 induction via derepression. Biologically, expression of FBXW2 or SOX2 promotes tumor sphere formation, which is blocked by MSX2 expression. By down-regulating SOX2 through inactivation of FBXW2 E3 ligase, MLN4924 sensitizes breast cancer cells to tamoxifen in both in vitro and in vivo cancer cell models. Thus, a negative cascade of the FBXW2-MSX2-SOX2 axis was established, which regulates stem cell property and drug resistance. Finally, an inverse correlation of expression was found between FBXW2 and MSX2 in lung and breast cancer tissues. Collectively, our study revealed an anticancer mechanism of MLN4924. By inactivating FBXW2, MLN4924 caused MSX2 accumulation to repress SOX2 expression, leading to suppression of stem cell property and sensitization of breast cancer cells to tamoxifen.

p53 haploinsufficiency and increased mTOR signalling define a subset of aggressive hepatocellular carcinoma.

BACKGROUND & AIMS: p53 mutations occur frequently in human HCC. Activation of the mammalian target of rapamycin (mTOR) pathway is also associated with HCC. However, it is still unknown whether these changes together initiate HCC and can be targeted as a potential therapeutic strategy. METHODS: We generated mouse models in which mTOR was hyperactivated by loss of tuberous sclerosis complex 1 (Tsc1) with or without p53 haplodeficiency. Primary cells were isolated from mouse livers. Oncogenic signalling was assessed in vitro and in vivo, with or without targeted inhibition of a single molecule or multiple molecules. Transcriptional profiling was used to identify biomarkers predictive of HCC. Human HCC materials were used to corroborate the findings from mouse models. RESULTS: p53 haploinsufficiency facilitates mTOR signalling via the PTEN/PI3K/Akt axis, promoting HCC tumorigenesis and lung metastasis. Inhibition of PI3K/Akt reduced mTOR activity, which effectively enhanced the anticancer effort of an mTOR inhibitor. ATP-binding cassette subfamily C member 4 (Abcc4) was found to be responsible for p53 haploinsufficiency- and Tsc1 loss-driven HCC tumorigenesis. Moreover, in clinical HCC samples, Abcc4 was specifically identified an aggressive subtype. The mTOR inhibitor rapamycin significantly reduced hepatocarcinogenesis triggered by Tsc1 loss and p53 haploinsufficiency in vivo, as well as the biomarker Abcc4. CONCLUSIONS: Our data advance the current understanding of the activation of the PTEN/PI3K/Akt/mTOR axis and its downstream target Abcc4 in hepatocarcinogenesis driven by p53 reduction and Tsc1 loss. Targeting mTOR, an unexpected vulnerability in p53 (haplo)deficiency HCC, can be exploited therapeutically to treat Abcc4-positive patients with HCC. LAY SUMMARY: Tsc1 loss facilitates the p53 (haplo)insufficiency-mediated activation of the PTEN/Akt/mTOR axis, leading to the elevated expression of Abcc4 to drive HCC tumorigenesis and metastasis in mice. Inhibition of mTOR protects against p53 haploinsufficiency and Tsc1 loss-triggered tumour-promoting activity, providing a new approach for treating an aggressive subtype of HCC exhibiting high Abcc4 expression.

FBXW10 promotes hepatocarcinogenesis in male patients and mice.

Hepatocellular carcinoma (HCC) is reported to associate with abnormal expression of SCF E3 ubiquitin ligases. FBXW10, an F-box protein of the E3 ubiquitin ligases, was abnormally regulated in HCC patients. However, whether FBXW10 is associated with HCC has not yet been evaluated. Here, we analyzed the associations between overall survival and various risk factors in 191 HCC tissues. Univariate and multivariate analyses demonstrated that FBXW10 was an independent risk factor related to HCC prognosis. The results showed that FBXW10, gender and tumor state were strongly associated with overall survival in HCC patients. Furthermore, high expression of FBXW10 was associated with poor survival among male HCC patients but not female HCC patients. FBXW10 was more highly expressed in male HCC tissues and more strongly related to vascular invasion in male HCC patients. Consistent with these findings, the male FBXW10-Tg(+) mice were more susceptible to tumorigenesis, changes in regenerative capacity, and liver injury and inflammation but not changes in liver function than FBXW10-Tg(-) mice. FBXW10 promoted cell proliferation and migration in HCC cell lines. Our findings reveal that FBXW10, an independent risk factor for HCC, promotes hepatocarcinogenesis in male patients, and is also a potential prognostic marker in male patients with HCC.

Targeting autophagy enhances heat stress-induced apoptosis via the ATP-AMPK-mTOR axis for hepatocellular carcinoma.

PURPOSE: Radiofrequency ablation (RFA) is widely accepted as a curative treatment for small hepatocellular carcinoma (HCC). However, insufficient RFA (IRFA) can lead to rapid local recurrence. The underlying mechanisms remain poorly understood. This study aimed to elucidate the role and regulatory mechanisms of autophagy in the recurrence of HCC after IRFA. MATERIALS AND METHODS: SMMC7721 and Huh7 cells were exposed to sublethal heat stress to stimulate the transition zone of IRFA treatment. The levels of autophagy were measured by western blot, immunofluorescence and transmission electron microscopy. Functional assays, such as CCK-8, EdU incorporation and flow cytometry, were performed to determine the role of heat-induced autophagy. The involved signaling pathways were explored by western blot. Finally, the antitumor effects of chloroquine (CQ) on heat-treated HCC cells were evaluated via an in vivo xenograft tumor model. RESULTS: Sublethal heat stress induced autophagy in a temperature- and time-dependent manner in HCC cells. Furthermore, the inhibition of autophagy by CQ or siRNA targeting the autophagy-related genes Beclin-1 and Atg5 enhanced heat-induced apoptosis. The combination of CQ and heat treatment significantly suppressed tumor growth both in vitro and in vivo. Mechanistically, we reported for the first time that the ATP-AMPK-mTOR signaling pathway was involved in heat-induced autophagy. CONCLUSIONS: Heat stress induced protective autophagy against heat-induced apoptosis in HCC via the ATP-AMPK-mTOR axis, suggesting that targeting autophagy may be a promising strategy for improving the efficacy of RFA treatment for HCC.

Bufalin induces apoptosis via mitochondrial ROS-mediated caspase-3 activation in HCT-116 and SW620 human colon cancer cells.

OBJECTIVE: Bufalin has been reported to kill various types of cancer including human colorectal cancer. Our previous study demonstrated that bufalin induced cell death via autophagy in HT-29 and Caco-2 colon cancer cells, but the action of bufalin remains unclear. This study was conducted to investigate the role of bufalin in other colon cancer HCT-116 and SW620 cells as well as its potential mechanism. METHODS: The effect of bufalin in HCT-116 and SW620 colon cancer cells was detected by assessing cell viability and cell death. Apoptotic cells were analyzed by Western blot and trypan blue dye exclusion assay. Mitochondrial ROS production was analyzed by flow cytometry after DCFDA and DHR-123 staining. The potential mechanism was investigated via pharmacological inhibitors. RESULTS: Bufalin had high potency against HCT-116 and SW620 cells with IC50 values of 12.823 ± 1.792 nM and 26.303 ± 2.498 nM in HCT-116 and SW620 cells, respectively. Bufalin decreased cell viability, increased cell death as well as caspase-3 downstream target (cleaved PARP) accumulation, and these actions were significantly blocked by pan-caspase inhibitor zVAD-FMK. Mechanistically, ROS production, but neither the NAD(P)H oxidase, AMPK, ERK nor p38, is responsible for bufalin-induced apoptotic cell death. Moreover, bufalin-induced ROS generation is derived from mitochondria. CONCLUSION: Bufalin significantly induces apoptosis in HCT-116 and SW620 colon cancer cells via mitochondrial ROS-mediated caspase-3 activation. We believe that our novel findings will greatly alter our current understanding on the anti-cancer mechanism of bufalin in colon cancer cells and will pave the way for further exploiting the clinical application.

Elevated expression of WSB2 degrades p53 and activates the IGFBP3-AKT-mTOR-dependent pathway to drive hepatocellular carcinoma.

Dysregulation of wild-type p53 turnover is a key cause of hepatocellular carcinoma (HCC), yet its mechanism remains poorly understood. Here, we report that WD repeat and SOCS box containing protein 2 (WSB2), an E3 ubiquitin ligase, is an independent adverse prognostic factor in HCC patients. WSB2 drives HCC tumorigenesis and lung metastasis in vitro and in vivo. Mechanistically, WSB2 is a new p53 destabilizer that promotes K48-linked p53 polyubiquitination at the Lys291 and Lys292 sites in HCC cells, leading to p53 proteasomal degradation. Degradation of p53 causes IGFBP3-dependent AKT/mTOR signaling activation. Furthermore, WSB2 was found to bind to the p53 tetramerization domain via its SOCS box domain. Targeting mTOR with everolimus, an oral drug, significantly blocked WSB2-triggered HCC tumorigenesis and metastasis in vivo. In clinical samples, high expression of WSB2 was associated with low wild-type p53 expression and high p-mTOR expression. These findings demonstrate that WSB2 is overexpressed and degrades wild-type p53 and then activates the IGFBP3-AKT/mTOR axis, leading to HCC tumorigenesis and lung metastasis, which indicates that targeting mTOR could be a new therapeutic strategy for HCC patients with high WSB2 expression and wild-type p53.

Cardiac glycosides block cancer growth through HIF-1α- and NF-κB-mediated Plk1.

Cardiac glycosides as inhibitors of the sodium/potassium adenosine triphosphatase (sodium pump) have been reported to block cancer growth by inducing G2/M phase arrest in many cancer cells. However, no detailed studies have been performed to distinguish between these two phases of cardiac glycoside-arrested cells. Furthermore, the underlying mechanisms involved in this cell cycle arrest process are still not known. Here, we report that bufalin and other cardiac glycosides potently induce mitotic arrest by the downregulation of polo-like kinase 1 (Plk1) expression. Live-cell imaging results demonstrate that bufalin-treated cells exhibit a marked delay in entering prophase at an early stage and are then arrested at prometaphase or induced entry into apoptosis. This phenotypic change is attributed to the downregulation of Plk1. We also show that bufalin and the knockdown of sodium pump reduce Plk1, at least in part, through downregulation of the nuclear transcription factors, hypoxia-inducible factor-1α (HIF-1α) and nuclear factor-kappa B (NF-κB). These findings suggest that cardiac glycosides induce mitotic arrest and apoptosis through HIF-1α- and NF-κB-mediated downregulation of Plk1 expression, demonstrating that HIF-1α and NF-κB are critical targets of cardiac glycosides in exerting their anticancer action.

An optimized protocol to detect protein ubiquitination and activation by ubiquitination assay in vivo and CCK-8 assay.

E3 ubiquitin ligases play a role in protein degradation, cellular localization, and activation, and their dysregulation is associated with human diseases. Here, we present a protocol to detect IGF2BP1 ubiquitination and activation by an E3 ubiquitin ligase FBXO45. We describe steps for preparing cells and transfecting plasmids. We detail the use of western blot to detect IGF2BP1 ubiquitination and a Cell Counting Kit-8 (CCK-8) assay to detect IGF2BP1 activation. This protocol is applicable to other proteins of interest. For complete details on the use and execution of this protocol, please refer to Lin et al. (2021).1.

In vivo analysis of FBXO45-mediated fibrosis and liver tumorigenesis in a chemically induced mouse model of hepatocellular carcinoma.

FBXO45, an E3 ubiquitin ligase highly expressed in liver tumors, is positively correlated with poor survival of hepatocellular carcinogenesis (HCC) patients, but whether FBXO45 drives HCC tumorigenesis remains largely unclear. Here, we describe a protocol that shortens the observation period for HCC tumorigenesis to assess the effects of FBXO45 in a DEN/CCl4-induced HCC mouse model. We describe steps for chemical induction of HCC in FBXO45-overexpressing mice, followed by tissue collection and pathology assessment via quantitative real-time PCR, histology, and immunohistochemistry. For complete details on the use and execution of this protocol, please refer to Lin et al. (2021).1.

Elevated FBXL18 promotes RPS15A ubiquitination and SMAD3 activation to drive HCC.

BACKGROUND: F-box and leucine-rich repeat protein 18 (FBXL18) is an E3 ubiquitin ligase that is reported to be involved in the tumorigenesis of various types of cancer. However, it remains unknown whether FBXL18 is correlated with hepatocarcinogenesis. METHODS AND RESULTS: In the current study, we found that FBXL18 was highly expressed in HCC tissues and positively associated with poor overall survival of HCC patients. FBXL18 was an independent risk factor for HCC patients. We observed that FBXL18 drove HCC in FBXL18 transgenic mice. Mechanistically, FBXL18 promoted the K63-linked ubiquitination of small-subunit ribosomal protein S15A (RPS15A) and enhanced its stability, increasing SMAD family member 3 (SMAD3) levels and translocation to the nucleus and promoting HCC cell proliferation. Moreover, the knockdown of RPS15A or SMAD3 significantly suppressed FBXL18-mediated HCC proliferation. In clinical samples, elevated FBXL18 expression was positively associated with RPS15A expression. CONCLUSION: FBXL18 promotes RPS15A ubiquitination and upregulates SMAD3 expression, leading to hepatocellular carcinogenesis, and this study provides a novel therapeutic strategy for HCC treatment by targeting the FBXL18/RPS15A/SMAD3 pathway.

Degradation of helicase-like transcription factor (HLTF) by ß-TrCP promotes hepatocarcinogenesis via activation of the p62/mTOR axis.

Helicase-like transcription factor (HLTF) has been found to be involved in the maintenance of genome stability and tumour suppression, but whether its downregulation in cancers is associated with posttranslational regulation remains unclear. Here, we observed that HLTF was significantly downregulated in hepatocellular carcinoma (HCC) tissues and positively associated with the survival of HCC patients. Mechanistically, the decreased expression of HLTF in HCC was attributed to elevated ß-TrCP-mediated ubiquitination and degradation. Knockdown of HLTF enhanced p62 transcriptional activity and mammalian target of rapamycin (mTOR) activation, leading to HCC tumourigenesis. Inhibition of mTOR effectively blocked ß-TrCP overexpression- or HLTF knockdown-mediated HCC tumourigenesis and metastasis. Furthermore, in clinical tissues, decreased HLTF expression was positively correlated with elevated expression of ß-TrCP, p62, or p-mTOR in HCC patients. Overall, our data not only uncover new roles of HLTF in HCC cell proliferation and metastasis, but also reveal a novel posttranslational modification of HLTF by ß-TrCP, indicating that the ß-TrCP/HLTF/p62/mTOR axis may be a new oncogenic driver involved in HCC development. This finding provides a potential therapeutic strategy for HCC patients by targeting the ß-TrCP/HLTF/p62/mTOR axis.

Elevated FBXL6 expression in hepatocytes activates VRK2-transketolase-ROS-mTOR-mediated immune evasion and liver cancer metastasis in mice.

Metastatic hepatocellular carcinoma (HCC) is the most lethal malignancy and lacks effective treatment. FBXL6 is overexpressed in human hepatocellular carcinoma (HCC), but whether this change drives liver tumorigenesis and lung metastasis in vivo remains unknown. In this study, we aimed to identify FBXL6 (F-Box and Leucine Rich Repeat Protein 6) as a key driver of HCC metastasis and to provide a new paradigm for HCC therapy. We found that elevated FBXL6 expression in hepatocytes drove HCC lung metastasis and was a much stronger driver than Kras mutation (KrasG12D/+;Alb-Cre), p53 haploinsufficiency (p53+/-) or Tsc1 loss (Tsc1fl/fl;Alb-Cre). Mechanistically, VRK2 promoted Thr287 phosphorylation of TKT and then recruited FBXL6 to promote TKT ubiquitination and activation. Activated TKT further increased PD-L1 and VRK2 expression via the ROS-mTOR axis, leading to immune evasion and HCC metastasis. Targeting or knockdown of TKT significantly blocked FBXL6-driven immune evasion and HCC metastasis in vitro and in vivo. Notably, the level of active TKT (p-Thr287 TKT) was increased and was positively correlated with the FBXL6 and VRK2 expression levels in HCC patients. Our work provides novel mechanistic insights into FBXL6-driven HCC metastasis and suggests that targeting the TKT-ROS-mTOR-PD-L1/VRK2 axis is a new paradigm for treating patients with metastatic HCC with high FBXL6 expression.

Silencing of FAM111B inhibited proliferation, migration and invasion of hepatoma cells through activating p53 pathway.

BACKGROUND: The function of Family with sequence similarity 111 member B (FAM111B) has been reported in multiple malignancies, but its involvement in occurrence and development of hepatocellular carcinoma (HCC) is still unclear. PURPOSE: To investigate the role of FAM111B in HCC and explore the potential molecular mechanism. METHODS: We examined the mRNA level of FAM111B via qPCR and protein level via immunohistochemistry in human HCC tissues. siRNA was used to construct a FAM111B-knockdown model in HCC cell lines. CCK-8, colony formation, transwell, and wound healing assays were performed to investigate the effect of FAM111B on proliferation, migration and invasion of HCC cell. Gene Set Enrichment Analysis, western blotting, and flow cytometry were carried out to find the related molecular mechanism. RESULTS: Human HCC tumor tissues exhibited higher expression of FAM111B, and high FAM111B expression was associated with poor prognosis. Vitro assays demonstrated that knockdown of FAM111B greatly repressed proliferation, migration and invasion of HCC cells. Furthermore, silencing of FAM111B significantly resulted in cell cycle arrest at G0/G1 and downregulation of epithelial-mesenchymal transition (EMT)-related proteins MMP7 and MMP9 via activation of p53 pathway. CONCLUSION: FAM111B played an essential role in promoting HCC development by regulation of p53 pathway.

FBXO43 increases CCND1 stability to promote hepatocellular carcinoma cell proliferation and migration.

Background and Aims: Abnormal expression of E3 ubiquitin ligase plays an important role in the development and progression of hepatocellular carcinoma (HCC), although the mechanism has remained elusive. This study aimed to investigate the biological function and potential mechanism of FBXO43 in HCC. Methods: FBXO43 expression in tissues and cells were detected by quantitative real-time PCR (qRT-PCR), Western blot, and immunohistochemistry (IHC). The Kaplan-Meier method and Cox regression analysis were used to explore the correlation between the expression level of FBXO43 and the clinical survival. MTT assay, EdU incorporation, colony formation, Transwell, and wound healing assays were performed to evaluate the function of FBXO43 in cell proliferation and migration in vitro. The interaction between FBXO43 and cyclin D1 (CCND1) was assessed by co-immunoprecipitation (Co-IP) assay and in vivo ubiquitination assay. Results: We found that FBXO43 was upregulated in HCC patient tissues and positively associated with poor clinicopathological features. Meanwhile, HCC patients with high expression of FBXO43 had shorter overall survival (OS) and disease-free survival (DFS). Furthermore, knockdown of FBXO43 inhibited HCC cell proliferation, migration and epithelial-mesenchymal transition (EMT) in HCC cells. Mechanistically, FBXO43 interacted with CCND1 and promoted its stability by polyubiquitination, leading to HCC cell proliferation, migration and EMT. Functional rescue experiments demonstrated that knockdown of CCND1 blocks FBXO43-mediated cell proliferation and metastasis. Conclusions: FBXO43, as an independent prognostic biomarker, promotes HCC cell proliferation, metastasis and EMT by stability of CCND1, which provides a new potential strategy for HCC treatment by targeting FBXO43-CCND1 axis.

Elevated FBXW10 drives hepatocellular carcinoma tumorigenesis via AR-VRK2 phosphorylation-dependent GAPDH ubiquitination in male transgenic mice.

Hepatocellular carcinoma (HCC), the most common liver cancer, occurs mainly in men, but the underlying mechanism remains to be further explored. Here, we report that ubiquitinated glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is responsible for HCC tumorigenesis in males. Mechanistically, FBXW10 promotes GAPDH polyubiquitination and activation; VRK2-dependent phosphorylation of GAPDH Ser151 residue is critical for GAPDH ubiquitination and activation. Activated GAPDH interacts with TRAF2, leading to upregulation of the canonical and noncanonical NF-κB pathways, and increases PD-L1 and AR-VRK2 expression, followed by induction of immune evasion, HCC tumorigenesis, and metastasis. Notably, the GAPDH inhibitor koningic acid (KA) activates immune response and protects against FBXW10-driven HCC in vivo. In HCC clinical samples, the expression of active GAPDH is positively correlated with that of FBXW10 and VRK2. We propose that the FBXW10/AR/VRK2/GAPDH/NF-κB axis is critical for HCC tumorigenesis in males. Targeting this axis with KA is a potential therapeutic strategy for male HCC patients.

Elevated FBXL6 activates both wild-type KRAS and mutant KRASG12D and drives HCC tumorigenesis via the ERK/mTOR/PRELID2/ROS axis in mice.

BACKGROUND: Kirsten rat sarcoma (KRAS) and mutant KRASG12D have been implicated in human cancers, but it remains unclear whether their activation requires ubiquitination. This study aimed to investigate whether and how F-box and leucine-rich repeat 6 (FBXL6) regulates KRAS and KRASG12D activity in hepatocellular carcinoma (HCC). METHODS: We constructed transgenic mouse strains LC (LSL-Fbxl6KI/+;Alb-Cre, n = 13), KC (LSL-KrasG12D/+;Alb-Cre, n = 10) and KLC (LSL-KrasG12D/+;LSL-Fbxl6KI/+;Alb-Cre, n = 12) mice, and then monitored HCC for 320 d. Multiomics approaches and pharmacological inhibitors were used to determine oncogenic signaling in the context of elevated FBXL6 and KRAS activation. Co­immunoprecipitation (Co-IP), Western blotting, ubiquitination assay and RAS activity detection assay were employed to investigate the underlying molecular mechanism by which FBXL6 activates KRAS. The pathological relevance of the FBXL6/KRAS/extracellular signal-regulated kinase (ERK)/mammalian target of rapamycin (mTOR)/proteins of relevant evolutionary and lymphoid interest domain 2 (PRELID2) axis was evaluated in 129 paired samples from HCC patients. RESULTS: FBXL6 is highly expressed in HCC as well as other human cancers (P < 0.001). Interestingly, FBXL6 drives HCC in transgenic mice. Mechanistically, elevated FBXL6 promotes the polyubiquitination of both wild-type KRAS and KRASG12D at lysine 128, leading to the activation of both KRAS and KRASG12D and promoting their binding to the serine/threonine-protein kinase RAF, which is followed by the activation of mitogen-activated protein kinase kinase (MEK)/ERK/mTOR signaling. The oncogenic activity of the MEK/ERK/mTOR axis relies on PRELID2, which induces reactive oxygen species (ROS) generation. Furthermore, hepatic FBXL6 upregulation facilitates KRASG12D to induce more severe hepatocarcinogenesis and lung metastasis via the MEK/ERK/mTOR/PRELID2/ROS axis. Dual inhibition of MEK and mTOR effectively suppresses tumor growth and metastasis in this subtype of cancer in vivo. In clinical samples, FBXL6 expression positively correlates with p-ERK (χ2 = 85.067, P < 0.001), p-mTOR (χ2 = 66.919, P < 0.001) and PRELID2 (χ2 = 20.891, P < 0.001). The Kaplan-Meier survival analyses suggested that HCC patients with high FBXL6/p-ERK levels predicted worse overall survival (log­rank P < 0.001). CONCLUSIONS: FBXL6 activates KRAS or KRASG12D via ubiquitination at the site K128, leading to activation of the ERK/mTOR/PRELID2/ROS axis and tumorigenesis. Dual inhibition of MEK and mTOR effectively protects against FBXL6- and KRASG12D-induced tumorigenesis, providing a potential therapeutic strategy to treat this aggressive subtype of liver cancer.

FBXW10-S6K1 promotes ANXA2 polyubiquitination and KRAS activation to drive hepatocellular carcinoma development in males.

The incidence rate of human hepatocellular carcinoma (HCC) is approximately three times higher in males than in females. A better understanding of the mechanisms underlying HCC development in males could lead to more effective therapies for HCC. Our previous study found that FBXW10 played a critical role in promoting HCC development in male mice and patients, but the mechanism remains unknown. Here, we found that FBXW10 promoted K63-linked ANXA2 polyubiquitination and activation in HCC tissues from males, and this process was required for S6K1-mediated phosphorylation. Activated ANXA2 further translocated from the cytoplasm to the cell membrane to bind KRAS and then activated the MEK/ERK pathway, leading to HCC proliferation and lung metastasis. Interfering with ANXA2 significantly blocked FBXW10-driven HCC growth and lung metastasis in vitro and in vivo. Notably, membrane ANXA2 was upregulated and positively correlated with FBXW10 expression in male HCC patients. These findings offer new insights into the regulation and function of FBXW10 signaling in HCC tumorigenesis and metastasis and suggest that the FBXW10-S6K1-ANXA2-KRAS-ERK axis may serve as a potential biomarker and therapeutic target in male HCC patients with high FBXW10 expression.

Novel microtubule-targeted agent 6-chloro-4-(methoxyphenyl) coumarin induces G2-M arrest and apoptosis in HeLa cells.

AIM: To identify a novel coumarin analogue with the highest anticancer activity and to further investigate its anticancer mechanisms. METHODS: The viability of cancer cells was investigated using the MTT assay. The cell cycle progression was evaluated using both flow cytometric and Western blotting analysis. Microtubule depolymerization was observed with immunocytochemistry in vivo and a tubulin depolymerization assay in vitro. Apoptosis was demonstrated using Annexin V/Propidium Iodide (PI) double-staining and sub-G(1) analysis. RESULTS: Among 36 analogues of coumarin, 6-chloro-4-(methoxyphenyl) coumarin showed the best anticancer activity (IC(50) value about 200 nmol/L) in HCT116 cells. The compound had a broad spectrum of anticancer activity against 9 cancer cell lines derived from colon cancer, breast cancer, liver cancer, cervical cancer, leukemia, epidermoid cancer with IC(50) value of 75 nmol/L-1.57 µmol/L but with low cytotocitity against WI-38 human lung fibroblasts (IC(50) value of 12.128 µmol/L). The compound (0.04-10 µmol/L) induced G(2)-M phase arrest in HeLa cells in a dose-dependent manner, which was reversible after the compound was removed. The compound (10-300 µmol/L) induced the depolymerization of purified porcine tubulin in vitro. Finally, the compound (0.04-2.5 µmol/L) induced apoptosis of HeLa cells in dose- and time-dependent manners. CONCLUSION: 6-Chloro-4-(methoxyphenyl) coumarin is a novel microtubule-targeting agent that induces G(2)-M arrest and apoptosis in HeLa cells.

Mutant Kras and mTOR crosstalk drives hepatocellular carcinoma development via PEG3/STAT3/BEX2 signaling.

Background & Aims: Abnormal activation of mTOR through loss of tuberous sclerosis complex (Tsc) frequently occurs in hepatocellular carcinoma (HCC). Mutant Kras could induce aggressive HCCs. Here, we aim to identify the predictive or prognostic biomarkers for HCC patients with Kras mutant and mTOR hyperactivation, and to provide potential therapeutic approaches for this subtype of HCCs. Methods: We generated transgenic mice in which hepatocytic mTOR was hyperactivated through Tsc1 insufficiency with or without oncogenic KrasG12D. Bioinformatics and gain- or loss-of-function studies were used to illustrate the mechanisms underlying oncogenic pathway alterations. Transcriptional profiling was used to identify biomarker for the subtype of HCC. The therapeutic efficacy of targeting mTOR was tested in a liver orthotropic homogeneous murine model. Results: Oncogenic KrasG12D facilitated mTOR activation via the Mek/Erk/ROS axis, leading to HCC tumorigenesis and metastasis. Inhibition of Mek/Erk enhanced the anticancer effect of mTOR inhibitor via reduction of mTOR activity. Paternally expressed 3 (PEG3) was responsible for Kras/Erk- and mTOR-driven HCC. Elevated PEG3 protein interacted with STAT3 and promoted its transcriptional activity, resulting in the upregulation of proliferation- and metastasis-related proteins. Targeting mTOR significantly inhibited these actions in vitro and in vivo. Moreover, in clinical samples, PEG3 was identified as a new poor prognostic marker for HCC patients with Kras/Erk and mTOR hyperactivation. Conclusion: These findings reveal the underlying mechanism of hepatocytic Kras/Erk-driven mTOR activation and its downstream targets (PEG3 and STAT3) in HCC, identify PEG3 as a new prognostic biomarker for HCC with Kras/Erk and mTOR hyperactivation, and provide a potential therapeutic strategy for this subset of HCC patients.

Elevated Sodium Pump α3 Subunit Expression Promotes Colorectal Liver Metastasis via the p53-PTEN/IGFBP3-AKT-mTOR Axis.

The sodium pump α3 subunit is associated with colorectal liver metastasis. However, the underlying mechanism involved in this effect is not yet known. In this study, we found that the expression levels of the sodium pump α3 subunit were positively associated with metastasis in colorectal cancer (CRC). Knockdown of the α3 subunit or inhibition of the sodium pump could significantly inhibit the migration of colorectal cancer cells, whereas overexpression of the α3 subunit promoted colorectal cancer cell migration. Mechanistically, the α3 subunit decreased p53 expression, which subsequently downregulated PTEN/IGFBP3 and activated mTOR, leading to the promotion of colorectal cancer cell metastasis. Reciprocally, knockdown of the α3 subunit or inhibition of the sodium pump dramatically blocked this effect in vitro and in vivo via the downregulation of mTOR activity. Furthermore, a positive correlation between α3 subunit expression and mTOR activity was observed in an aggressive CRC subtype. Conclusions: Elevated expression of the sodium pump α3 subunit promotes CRC liver metastasis via the PTEN/IGFBP3-mediated mTOR pathway, suggesting that sodium pump α3 could represent a critical prognostic marker and/or therapeutic target for this disease.