Prostaglandin F2α synthase promotes oxaliplatin resistance in colorectal cancer through prostaglandin F2α-dependent and F2α-independent mechanism.

BACKGROUND: Oxaliplatin (Oxa) is the first-line chemotherapy drug for colorectal cancer (CRC), and Oxa resistance is crucial for treatment failure. Prostaglandin F2α synthase (PGF2α) (PGFS), an enzyme that catalyzes the production of PGF2α, is involved in the proliferation and growth of a variety of tumors. However, the role of PGFS in Oxa resistance in CRC remains unclear. AIM: To explore the role and related mechanisms of PGFS in mediating Oxa resistance in CRC. METHODS: The PGFS expression level was examined in 37 pairs of CRC tissues and paracancerous tissues at both the mRNA and protein levels. Overexpression or knockdown of PGFS was performed in CRC cell lines with acquired Oxa resistance (HCT116-OxR and HCT8-OxR) and their parental cell lines (HCT116 and HCT8) to assess its influence on cell proliferation, chemoresistance, apoptosis, and DNA damage. For determination of the underlying mechanisms, CRC cells were examined for platinum-DNA adducts and reactive oxygen species (ROS) levels in the presence of a PGFS inhibitor or its products. RESULTS: Both the protein and mRNA levels of PGFS were increased in the 37 examined CRC tissues compared to the adjacent normal tissues. Oxa induced PGFS expression in the parental HCT116 and HCT8 cells in a dose-dependent manner. Furthermore, overexpression of PGFS in parental CRC cells significantly attenuated Oxa-induced proliferative suppression, apoptosis, and DNA damage. In contrast, knockdown of PGFS in Oxa-resistant HCT116 and HCT8 cells (HCT116-OxR and HCT8-OxR) accentuated the effect of Oxa treatment in vitro and in vivo. The addition of the PGFS inhibitor indomethacin enhanced the cytotoxicity caused by Oxa. Treatment with the PGFS-catalyzed product PGF2α reversed the effect of PGFS knockdown on Oxa sensitivity. Interestingly, PGFS inhibited the formation of platinum-DNA adducts in a PGF2α-independent manner. PGF2α exerts its protective effect against DNA damage by reducing ROS levels. CONCLUSION: PGFS promotes resistance to Oxa in CRC via both PGF2α-dependent and PGF2α-independent mechanisms.

piR-823 inhibits cell apoptosis via modulating mitophagy by binding to PINK1 in colorectal cancer.

Mitophagy plays a vital role in the maintenance of mitochondrial homeostasis and tumorigenesis. Noncoding RNA piR-823 contributes to colorectal tumorigenesis. In this study, we aim to evaluate piR-823-mediated mitophagy and its mechanistic association with colorectal cancer (CRC). Digital gene expression analysis was performed to explore the potential functions of piR-823. A piR-823 antagomir (Ant-823) was used to inhibit piR-823 expression, and piR-823 mimics (mimics-823) were used to increase piR-823 expression. Mitophagy was measured in vivo and in vitro by immunofluorescence and western blot analysis. JC-1 staining, ATP production, real-time PCR, and western blot analysis were used to measure changes in mitochondrial quality and number. siRNA transfection was used to inhibit mitophagy, and CCCP was used to induce mitophagy. RNA pull-down assays and RNA-binding protein immunoprecipitation assays were conducted to investigate the molecular mechanisms. Here, we found that CRC cells transfected with Ant-823 presented an altered expression of autophagic and mitophagy genes by Digital gene expression analysis. Ant-823 could promote Parkin activation and mitophagy in vitro and in vivo, followed by mitochondrial loss and dysfunction of some mitochondria, whereas mimics-823 exerted the opposite effects in CRC cells. The inhibition of mitophagy by siParkin alleviated Ant-823-induced mitochondrial loss and dysfunction, as well as apoptosis to a certain extent. Furthermore, piR-823 was found to interact with PINK1 and promote its ubiquitination and proteasome-dependent degradation, thus alleviating mitophagy. Finally, these findings were verifed in samples obtained by patients affected by colorectal cancer. In conclusion, we identify a novel mechanism by which piR-823 regulates mitophagy during CRC tumorigenesis by increasing PINK1 degradation.

Risk Factors for Brain Metastasis of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a common malignancy with high mortality, especially in HCC patients with brain metastases (BMS). However, few studies have investigated the risk factors for BMS among HCC patients based on large-scale population. The study involved clinical data of 36,091 patients who met the inclusion criteria from the SEER database, from 2004 to 2016. Univariate analysis and multifactor logistics regression analysis was used to analyze risk factors affecting BMS among HCC patients. This study revealed that BMS occurred in 108 of 36,091 patients, with an incidence of 0.33%. Median survival was 7 months for patients with BMS, but 12 months for patients without BMS. Univariate analysis showed that pathological low differentiation and undifferentiation, lymph node metastasis, no surgical treatment, and no chemotherapy and radiotherapy increased risk of BMS (P < 0.05). Multivariate analysis suggested that no surgical treatment and no chemotherapy or radiotherapy were independent risk factors for BMS (P < 0.001). Our findings highlighted that the independent risk factors for BMS were no surgical treatment, no chemotherapy, and no radiotherapy.

REC8 enhances stemness and promotes metastasis of colorectal cancer through BTK/Akt/ß-catenin signaling pathway.

Cancer/testis antigens (CTAs) are often aberrantly expressed in cancer stem cells (CSCs) which are responsible for tumor metastasis. Rec8 meiotic recombination protein (REC8), a member of CTAs, shares distinct roles in various cancers, while its contribution to CSCs and colorectal cancer (CRC) remains unclear. We found that overexpression of REC8 facilitated the migration and invasion of CRC cells (DLD-1 and SW480 cells) in vitro and promoted the liver metastasis of CRC in vivo. Moreover, REC8 is highly expressed in CRC stem-like cells and is required for the maintenance of CSC stemness. Mechanistic studies suggested that REC8 mediated through the activation of Bruton tyrosine kinase (BTK). Inhibition of BTK by ibrutinib not only suppressed the migration and invasion-promoting ability, but also declined the increased expression of p-BTK, p-Akt, ß-catenin, and CSC markers upon REC8 overexpression. Importantly, high expression of REC8 in cancerous tissues was related to advanced clinical stage and lymph node metastasis of 62 CRC patients, and REC8 was enriched in the cancerous cells positive for CSC markers. Collectively, our results indicate that REC8 promotes CRC metastasis by increasing cell stemness through BTK/Akt/ß-catenin pathway.

MitoQ inhibits hepatic stellate cell activation and liver fibrosis by enhancing PINK1/parkin-mediated mitophagy.

Mitophagy affects the activation of hepatic stellate cells (HSCs). Mitochondria-targeted ubiquinone (MitoQ) is a mitochondria-targeted antioxidant that reduces the production of intracellular reactive oxygen species (ROS). However, its relationship with mitophagy remains unclear. This study evaluated mitophagy during HSC activation and the effects of MitoQ on mitophagy in cell culture and in an animal model of the activation of HSCs. We found that MitoQ reduced the activation of HSCs and alleviated hepatic fibrosis. PINK1 (PTEN-induced putative kinase 1) is a putative serine/threonine kinase located in the mitochondria's outer membrane. While the activation of primary HSCs or LX-2 cells was associated with reduced PINK1/parkin-mediated mitophagy, MitoQ reduced intracellular ROS levels, enhanced PINK1/parkin-mediated mitophagy, and inhibited the activation of HSCs. After knocking down the key mitophagy-related protein, PINK1, in LX-2 cells to block mitophagy, MitoQ intervention failed to inhibit HSC activation. Our results showed that MitoQ inhibited the activation of HSCs and alleviated hepatic fibrosis by enhancing PINK1/parkin-mediated mitophagy.

Soluble TREM-1, as a new ligand for the membrane receptor Robo2, promotes hepatic stellate cells activation and liver fibrosis.

Triggering receptor expressed on myeloid cells-1 (TREM-1) exists in two forms: a transmembrane form and a soluble form (sTREM-1). The levels of sTREM-1 are elevated in supernatants of activated HSCs. However, the role of sTREM-1 in HSC activation and liver fibrosis remains undefined. Previous studies have primarily focused on the transmembrane form of TREM-1; we innovatively observed the function of sTREM-1 as a ligand in liver fibrosis and screened its receptor. Here, recombinant sTREM-1 was used as a stimulator which induced HSC activation and further aggravated liver fibrosis. Then, screening for sTREM-1 interacting membrane receptors was performed using pull-down assay followed by mass spectrometry, and the membrane receptor roundabout guidance receptor 2 (Robo2) was identified as a candidate receptor for sTREM-1. The interaction between sTREM-1 and Robo2 was verified by pull-down and immunofluorescence. The role of Robo2 on sTREM-1-induced HSC activation and its downstream signal pathways was assessed by knockdown of Robo2 in LX-2 cells. Furthermore, HSC-specific knockdown of Robo2 was achieved in a mouse model of liver fibrosis by using a recombinant adeno-associated virus (AAV) vector to confirm the role of the receptor, and we proved that Robo2 knockdown inhibited the activation of HSC and liver fibrosis, which also led to the inactivation of Smad2/3 and PI3K/Akt pathways in sTREM-1-induced HSC activation and liver fibrosis. In conclusion, sTREM-1 acts as a new ligand of Robo2; the binding of sTREM-1 to Robo2 initiates the activation of the downstream Smad2/3 and PI3K/Akt signalling pathways, thereby promoting HSC activation and liver fibrosis.

RNF141 interacts with KRAS to promote colorectal cancer progression.

RING finger proteins (RNFs) play a critical role in cancer initiation and progression. RNF141 is a member of RNFs family; however, its clinical significance, roles, and mechanism in colorectal cancer (CRC) remain poorly understood. Here, we examined the expression of RNF141 in 64 pairs of CRC and adjacent normal tissues by real-time PCR, Western blot, and immunohistochemical analysis. We found that there was more expression of RNF141 in CRC tissue compared with its adjacent normal tissue and high RNF141 expression associated with T stage. In vivo and in vitro functional experiments were conducted and revealed the oncogenic role of RNF141 in CRC. RNF141 knockdown suppressed proliferation, arrested the cell cycle in the G1 phase, inhibited migration, invasion and HUVEC tube formation but promoted apoptosis, whereas RNF141 overexpression exerted the opposite effects in CRC cells. The subcutaneous xenograft models showed that RNF141 knockdown reduced tumor growth, but its overexpression promoted tumor growth. Mechanistically, liquid chromatography-tandem mass spectrometry indicated RNF141 interacted with KRAS, which was confirmed by Co-immunoprecipitation, Immunofluorescence assay. Further analysis with bimolecular fluorescence complementation (BiFC) and Glutathione-S-transferase (GST) pull-down assays showed that RNF141 could directly bind to KRAS. Importantly, the upregulation of RNF141 increased GTP-bound KRAS, but its knockdown resulted in a reduction accordingly. Next, we demonstrated that RNF141 induced KRAS activation via increasing its enrichment on the plasma membrane not altering total KRAS expression, which was facilitated by the interaction with LYPLA1. Moreover, KRAS silencing partially abolished the effect of RNF141 on cell proliferation and apoptosis. In addition, our findings presented that RNF141 functioned as an oncogene by upregulating KRAS activity in a manner of promoting KRAS enrichment on the plasma membrane in CRC.

Y-box binding protein 1 augments sorafenib resistance via the PI3K/Akt signaling pathway in hepatocellular carcinoma.

BACKGROUND: Sorafenib is the first-line treatment for patients with advanced hepatocellular carcinoma (HCC). Y-box binding protein 1 (YB-1) is closely correlated with tumors and drug resistance. However, the relationship between YB-1 and sorafenib resistance and the underlying mechanism in HCC remain unknown. AIM: To explore the role and related mechanisms of YB-1 in mediating sorafenib resistance in HCC. METHODS: The protein expression levels of YB-1 were assessed in human HCC tissues and adjacent nontumor tissues. Next, we constructed YB-1 overexpression and knockdown hepatocarcinoma cell lines with lentiviruses and stimulated these cell lines with different concentrations of sorafenib. Then, we detected the proliferation and apoptosis in these cells by terminal deoxynucleotidyl transferase dUTP nick end labeling, flow cytometry and Western blotting assays. We also constructed a xenograft tumor model to explore the effect of YB-1 on the efficacy of sorafenib in vivo. Moreover, we studied and verified the specific molecular mechanism of YB-1 mediating sorafenib resistance in hepatoma cells by digital gene expression sequencing (DGE-seq). RESULTS: YB-1 protein levels were found to be higher in HCC tissues than in corresponding nontumor tissues. YB-1 suppressed the effect of sorafenib on cell proliferation and apoptosis. Consistently, the efficacy of sorafenib in vivo was enhanced after YB-1 was knocked down. Furthermore, KEGG pathway enrichment analysis of DGE-seq demonstrated that the phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) signaling pathway was essential for the sorafenib resistance induced by YB-1. Subsequently, YB-1 interacted with two key proteins of the PI3K/Akt signaling pathway (Akt1 and PIK3R1) as shown by searching the BioGRID and HitPredict websites. Finally, YB-1 suppressed the inactivation of the PI3K/Akt signaling pathway induced by sorafenib, and the blockade of the PI3K/Akt signaling pathway by LY294002 mitigated YB-1-induced sorafenib resistance. CONCLUSION: Overall, we concluded that YB-1 augments sorafenib resistance through the PI3K/Akt signaling pathway in HCC and suggest that YB-1 is a key drug resistance-related gene, which is of great significance for the application of sorafenib in advanced-stage HCC.