Anaplastic Lymphoma Kinase (ALK) Inhibitors Show Activity in Colorectal Cancer With ALK Rearrangements: Case Series and Literature Review.

Anaplastic lymphoma kinase (ALK) rearrangement is a well-known driver oncogene detected in approximately 5% of non-small cell lung cancer. However, ALK rearrangement is much less frequent in other solid tumors outside the lungs, such as colorectal cancer (CRC); thus, the optimal management of CRC with ALK rearrangements has yet to be established. In this report, we describe 2 cases of ALK-positive CRC, both of which benefited from ALK tyrosine kinase inhibitor (ALK-TKI) therapy. Case 1 was a postoperative patient with poorly differentiated colon adenocarcinoma, who was diagnosed with metastatic relapse shortly after surgery. Both fluorouracil, leucovorin, and oxaliplatin (FOLFOX) and bevacizumab combined with 5-fluorouracil, l-leucovorin, and irinotecan (FOLFIRI) proved ineffective against the disease. The patient was then treated with ensartinib, as the CAD-ALK fusion gene was detected by genomic analysis. The patient was initially treated with ensartinib monotherapy for 9 months, then with ensartinib combined with local radiotherapy and fruquintinib for another 4 months for isolated hilar hepatic lymph node metastasis. The patient experienced disease progression with an acquired ALK G1202R resistance mutation that responded well to lorlatinib. Case 2 involved a 72-year-old man with advanced colon cancer (pT4bN2aM1b, stage IV) harboring an EML4-ALK fusion. The patient underwent resection of the right colon tumor due to intestinal obstruction, but the disease continued to progress after 12 courses of FOLFIRI and bevacizumab chemotherapy. However, the patient responded remarkably well to alectinib. Our report emphasizes the importance of gene detection in the treatment of malignant tumors, and the significance of ALK mutations in CRC.

Tripartite motif 31 drives gastric cancer cell proliferation and invasion through activating the Wnt/ß-catenin pathway by regulating Axin1 protein stability.

Mounting evidence has proposed the importance of the Wnt/ß-catenin pathway and tripartite motif 31 (TRIM31) in certain malignancies. Our research aimed to clarify the correlation between aberrant TRIM31 expression and the Wnt/ß-catenin pathway during gastric cancer (GC) oncogenesis and development. TRIM31 was drastically elevated in GC tissues and was closely associated with aggressive clinical outcomes and poor prognosis. Moreover, TRIM31 downregulation attenuated GC cell proliferation and invasion in vitro. Mechanistically, TRIM31 could bind and ubiquitinate Axin1 protein, thereby facilitating the activation of the Wnt/ß-catenin pathway. Additionally, Axin1 knockdown partially abrogated the inhibitory effects on the proliferative, invasive and migratory abilities of GC cells induced by TRIM31 silencing. Furthermore, TRIM31 was negatively correlated with Axin1 protein expression in GC tissues. In summary, we revealed a new TRIM31-Axin1-Wnt/ß-catenin axis that contributed greatly to the progression of GC, and targeting this regulatory axis may represent an effective treatment for GC patients.

Positive efficacy of Lactiplantibacillus plantarum MH-301 as a postoperative adjunct to endoscopic sclerotherapy for internal hemorrhoids: a randomized, double-blind, placebo-controlled trial.

Background: Endoscopic sclerotherapy is a widely used minimally invasive procedure for internal hemorrhoids, yet postoperative symptoms remain a concern. The purpose of this study is to investigate the postoperative adjuvant efficacy of Lactiplantibacillus plantarum. Method: In this study, patients (≥18 years) with internal hemorrhoids that conformed to Goligher's classification of grade I-III received administration of L. plantarum MH-301 for 4 weeks following endoscopic sclerotherapy. The primary clinical endpoint in this study was the improvement rate, which was defined as the percentage of patients whose n-HDSS score decreased to 0 following the procedure. Stools were collected for high-throughput sequencing analysis post operation. Result: A total of 103 participants (51 in the LP group and 52 in the C group) were recruited, with 96 completing the entire trial (49 in the LP group and 47 in the C group). The primary clinical endpoint showed a higher improvement rate in the LP group (87.8% vs. 70.2%, P = 0.045). High-throughput sequencing analysis demonstrated that the LP group had a greater diversity of intestinal microbiota and a higher relative abundance of beneficial bacteria such as Bifidobacterium, Megamonas, and Lactobacillus. No significant difference in postoperative complications and adverse events was found. Conclusion: This paper concludes that the administration of L. plantarum MH-301 after endoscopic sclerotherapy can further increase the efficacy of the procedure and improve bowel movements. Regulation of intestinal microbiota may be the potential mechanism for the efficacy of L. plantarum MH-301.

miR-3133 inhibits gastrointestinal cancer progression through activation of Hippo and p53 signalling pathways via multi-targets.

BACKGROUND: Malignant cell growth and chemoresistance, the main obstacles in treating gastrointestinal cancer (GIC), rely on the Hippo and p53 signalling pathways. However, the upstream regulatory mechanisms of these pathways remain complex and poorly understood. METHODS: Immunohistochemistry (IHC), western blot and RT-qPCR were used to analyse the expression of RNF146, miR-3133 and key components of Hippo and p53 pathway. CCK-8, colony formation, drug sensitivity assays and murine xenograft models were used to investigate the effect of RNF146 and miR-3133 in GIC. Further exploration of the upstream regulatory mechanism was performed using bioinformatics analysis, dual-luciferase reporter gene, immunoprecipitation assays and bisulfite sequencing PCR (BSP). RESULTS: Clinical samples, in vitro and in vivo experiments demonstrated that RNF146 exerts oncogenic effects in GIC by regulating the Hippo pathway. Bioinformatics analysis identified a novel miRNA, miR-3133, as an upstream regulatory factor of RNF146. fluorescence in situ hybridization and RT-qPCR assays revealed that miR-3133 was less expressed in gastrointestinal tumour tissues and was associated with adverse pathological features. Functional assays and animal models showed that miR-3133 promoted the proliferation and chemotherapy sensitivity of GIC cells. miR-3133 affected YAP1 protein expression by targeting RNF146, AGK and CUL4A, thus activating the Hippo pathway. miR-3133 inhibited p53 protein degradation and extended p53's half-life by targeting USP15, SPIN1. BSP experiments confirmed that miR-3133 promoter methylation is an important reason for its low expression. CONCLUSION: miR-3133 inhibits GIC progression by activating the Hippo and p53 signalling pathways via multi-targets, including RNF146, thereby providing prognostic factors and valuable potential therapeutic targets for GIC.

WWP2 drives the progression of gastric cancer by facilitating the ubiquitination and degradation of LATS1 protein.

BACKGROUND: Large tumor suppressor kinase 1 (LATS1), one of the predominant components of the Hippo pathway, has been characterized as a key player controlling the proliferation and invasion of cancer cells, including gastric cancer (GC) cells. However, the mechanism by which the functional stability of LATS1 is modulated has yet to be elucidated. METHODS: Online prediction tools, immunohistochemistry and western blotting assays were used to explore the expression of WW domain-containing E3 ubiquitin ligase 2 (WWP2) in GC cells and tissues. Gain- and loss-of-function assays, as well as rescue experiments were performed to determine the role of the WWP2-LATS1 axis in cell proliferation and invasion. Additionally, the mechanisms involving WWP2 and LATS1 were assessed by coimmunoprecipitation (Co-IP), immunofluorescence, cycloheximide and in vivo ubiquitination assays. RESULTS: Our results demonstrate a specific interaction between LATS1 and WWP2. WWP2 was markedly upregulated and correlated with disease progression and a poor prognosis in GC patients. Moreover, ectopic WWP2 expression facilitated the proliferation, migration and invasion of GC cells. Mechanistically, WWP2 interacts with LATS1, resulting in its ubiquitination and subsequent degradation, leading to increased transcriptional activity of YAP1. Importantly, LATS1 depletion abolished the suppressive effects of WWP2 knockdown on GC cells. Furthermore, WWP2 silencing attenuated tumor growth by regulating the Hippo-YAP1 pathway in vivo. CONCLUSIONS: Our results define the WWP2-LATS1 axis as a critical regulatory mechanism of the Hippo-YAP1 pathway that promotes GC development and progression. Video Abstract.

Low-density lipoprotein receptor-related protein 8 facilitates the proliferation and invasion of non-small cell lung cancer cells by regulating the Wnt/ß-catenin signaling pathway.

Low-density lipoprotein receptor-related protein 8 (LRP8) is involved in the development of multiple tumors, including lung cancer. However, the exact mechanism by which LRP8 exerts its oncogenic role in non-small cell lung cancer (NSCLC) remains elusive. Hence, in this study, we aimed to unravel the expression and role of LRP8 in the progression of NSCLC. We used online bioinformatics databases to identify the expression of LRP8 in multiple types of lung cancer. We validated LRP8 expression in NSCLC cell lines and tissues by Western blotting and immunohistochemistry. The functions of LRP8 in NSCLC carcinogenesis and progression were determined using in vitro and in vivo systems. The Wnt pathway activator LiCl was further used to validate the regulatory role of LRP8 in Wnt/ß-catenin signaling. We demonstrated that LRP8 was markedly overexpressed in NSCLC tissues and cell lines, and its overexpression significantly correlated with poor clinicopathological characteristics and prognosis. Moreover, LRP8 depletion suppressed cell proliferation, migration, invasion, and epithelial-mesenchymal transition in vitro and impeded tumor growth in vivo. Mechanistically, LPR8 knockdown elicited tumor-suppressive functions by suppressing the Wnt/ß-catenin pathway, which was partially reversed by LiCl. Hence, our study revealed that LRP8 facilitates NSCLC cell proliferation and invasion via the Wnt/ß-catenin pathway, and thus LRP8 could be a novel therapeutic target for NSCLC.

The E3 Ubiquitin Ligase TRIM11 Facilitates Gastric Cancer Progression by Activating the Wnt/ß-Catenin Pathway via Destabilizing Axin1 Protein.

BACKGROUND: Aberrant expression of tripartite motif 11 (TRIM11) and the Wnt/ß-catenin pathway are essential for facilitating tumorigenesis and progression in multiple types of cancer. AIM: To investigate the molecular changes linking the dysregulation of TRIM11 and Wnt/ß-catenin pathway activation in gastric cancer (GC) progression. METHODS: The expression levels of TRIM11 were detected in GC tissues and cells by immunohistochemistry and western blotting. The role of TRIM11 in the growth, proliferation, and invasion of gastric cancer cells was observed by a series of cell functional experiments and further verified in vivo. Co-immunoprecipitation (Co-IP), immunofluorescence, cycloheximide, and western blotting assays and other experiments were conducted to explore the mechanisms of TRIM11 underlying the regulation of the Wnt/ß-catenin pathway. For further verification, rescue experiments were performed by cotransfection of TRIM11 and Axin1 siRNA in GC cells. RESULTS: Using Co-IP assays, we identified TRIM11 as a potent binding partner of Axin1 in GC cells. Elevated TRIM11 levels were significantly correlated with unfavorable clinical outcomes and poor survival in patients with GC. In addition, TRIM11 promoted the cell proliferation and invasion capacities of GC cells in vitro and tumor growth in vivo. Mechanistic investigations revealed that TRIM11 destabilized Axin1 protein by interacting with Axin1, thus inducing the activation of the Wnt/ß-catenin pathway. Moreover, we found that the oncogenic effects of TRIM11 on GC cells were partly mediated by suppression of Axin1. Furthermore, the protein expression of TRIM11 and Axin1 was negatively correlated in GC tissues. CONCLUSION: Collectively, our findings not only establish a pivotal TRIM11-Axin1-ß-catenin axis in driving GC progression but also indicate that TRIM11 serves as a valuable therapeutic target for the treatment of GC patients.

The microRNA-381(miR-381)/Spindlin1(SPIN1) axis contributes to cell proliferation and invasion of colorectal cancer cells by regulating the Wnt/ß-catenin pathway.

Our study aimed to investigate the clinical significance and biological functions of Spindlin1 (SPIN1) in colorectal cancer (CRC) tumorigenesis and progression, as well as the mechanism underlying its upregulation. The expression of SPIN1 was detected by immunohistochemistry and western blotting assays. Bioinformatics prediction and dual-luciferase reporter assays were used to determine whether microRNA-381 (miR-381) could target SPIN1. A series of cell functional experiments were performed to investigate whether the miR-381-mediated regulation of SPIN1 is involved in the progression and aggressiveness of CRC cells via the Wnt/ß-catenin pathway. Our results showed that SPIN1 is frequently overexpressed in CRC tissues and cell lines, and its upregulation is positively correlated with disease progression and lymph node metastasis. Moreover, SPIN1 depletion suppresses cell growth, migration, and invasion through inactivation of the Wnt/ß-catenin signaling pathway, which recapitulates the effects of miR-381 upregulation. Moreover, SPIN1 is a target gene of miR-381, and miR-381 is downregulated in CRC. Furthermore, the reintroduction of SPIN1 partially abolished the miR-381-mediated inhibitory effects in CRC cells. In summary, our data revealed that the miR-381/SPIN1 axis greatly contributes to CRC tumorigenesis by orchestrating the Wnt/ß-catenin pathway, thereby representing actionable therapeutic targets for colorectal cancer patients.

Cullin-4B promotes cell proliferation and invasion through inactivation of p53 signaling pathway in colorectal cancer.

Cullin 4B (CUL4B) is a member of the Cullin RING E3 ligase family, which is found to be overexpressed in multiple cancers, thus facilitating tumorigenesis and progression. However, the correlation between CUL4B and p53 in colorectal cancer cells (CRC) remains to be further elucidated. In this study, we newly identified that CUL4B functions as a negative regulator of p53, thereby facilitating CRC tumorigenesis and progression. Our data has demonstrated that CUL4B was frequently overexpressed in CRC tissues, and its upregulation was closely correlated with disease progression and poor prognosis. Moreover, CUL4B knockdown suppressed cell proliferation, invasion and epithelial-mesenchymal transition (EMT) of CRC cells. Mechanistically, CUL4B depletion increased the expression of p53 protein and its downstream targets p21, PUMA and MDM2. Furthermore, CUL4B depletion prolonged the half-life of p53 protein, and CUL4B is a binding partner of MDM2. In conclusion, our study shed new lights on the complex regulatory network between CUL4B and p53, and clarifies this CUL4B-p53 axis contributes greatly to CRC tumorigenesis and progression.

Coiled-Coil Domain-Containing 68 Downregulation Promotes Colorectal Cancer Cell Growth by Inhibiting ITCH-Mediated CDK4 Degradation.

Coiled-coil domain-containing 68 (CCDC68) plays different roles in cancer and is predicted as a tumor suppressor in human colorectal cancer (CRC). However, the specific role of CCDC68 in CRC and the underlying mechanisms remain unknown. Here, we showed that CCDC68 expression was lower in CRC than that in corresponding normal tissues, and CCDC68 level was positively correlated with disease-free survival. Ectopic expression of CCDC68 decreased CRC cell proliferation in vitro and suppressed the growth of CRC xenograft tumors in vivo. CCDC68 caused G0/G1 cell cycle arrest, downregulated CDK4, and upregulated ITCH, the E3 ubiquitin ligase responsible for CDK4 protein degradation. This increased CDK4 degradation, which decreased CDK4 protein levels and inhibited CRC tumor growth. Collectively, the present results identify a novel CDK4 regulatory axis consisting of CCDC68 and ITCH, which suggest that CCDC68 is a promising target for the treatment of CRC.

An Assessment of Combination of the Camrelizumab With Chemotherapy in Metastatic Biliary Tract Cancers.

BACKGROUND: Monoclonal antibodies that target the PD-1 receptor are emerging as promising therapeutic candidates for the treatment of biliary tract cancers (BTCs). The purpose of the current study was to assess the combination of the camrelizumab with chemotherapy as a first-line treatment for metastatic BTCs. METHODS: We conducted a prospective single-arm pilot study of PD-1 antibody (camrelizumab 3 mg/kg d1, Q2 W or Q3 W) combined with different chemotherapy regimens as first-line treatment for BTCs. Efficacy endpoints were objective response rate (ORR), disease control rate (DCR), progression free survival (PFS), and overall survival (OS). Treatment-related adverse events (TRAEs) were also evaluated. RESULTS: Fourteen patients with histologically confirmed BTCs were evaluated. The ORR was 14.3% (95% CI: 1.8 to 42.8) and the DCR was 64.3% (95%CI: 41.7 to 86.9). The median PFS was 6.5 months (95% CI: 3.8 to 9.2), and the 6- and 12-month PFS rates were 61.6% and 12.3%, respectively. The median OS was 9.9 months (95% CI: 7.6 to 12.2), and the 6-and 12-month OS rates were 74.5% and 26.6%, respectively. All patients displayed at least 1 TRAE., and Grade 3 or 4 TRAEs occurred in 6 (42.86%) patients. CONCLUSIONS: Camrelizumab combined with chemotherapy as first-line treatment for metastatic BTCs demonstrated acceptable safety and efficacy in our pilot study. These findings warrant prospective controlled clinical trials comparing combinations of camrelizumab and chemotherapy to standard regimens.

Corrigendum: NUSAP1 Promotes Gastric Cancer Tumorigenesis and Progression by Stabilizing the YAP1 Protein.

[This corrects the article DOI: 10.3389/fonc.2020.591698.].

Ruscogenin induces ferroptosis in pancreatic cancer cells.

Pancreatic cancer is characterized by aggressive and highly metastatic phenotypes. This disease exhibits a poor patient prognosis and is considered a challenge due to the limited treatment options encountered in clinical practice. Previous studies have shown that ruscogenin, a saponin found in the root of Ophiopogon japonicus, exerts a wide range of biological functions including anticancer activity. In the present study, the effects of ruscogenin were investigated on pancreatic cancer cells and the potential molecular mechanism of this compound was explored. Cell viability was assessed using the 3­(4,5­dimethylthiazol­2­yl)­2,5­diphenyltetrazolium bromide (MTT) assay. Cell death was measured by trypan blue staining and by flow cytometry. The number of iron oxide nanoparticles was measured using Prussian blue staining. Reactive oxygen species (ROS) production was assessed using flow cytometry with dihydroethidium staining. Protein expression of the associated genes was assayed by western blotting. Furthermore, in vivo experiments were conducted to confirm the antitumor effects and assay the potential toxicity of ruscogenin in a nude mouse xenograft model. The results indicated that ruscogenin significantly repressed cell viability and induced cell death of pancreatic cancer cells in vitro in a dose­ and time­dependent manner. Furthermore, ruscogenin increased the concentration of intracellular ferrous irons and the production of ROS. This effect was inhibited by deferoxamine (DFO). Ruscogenin induced ferroptosis by regulating the levels of transferrin and ferroportin. These two proteins were involved in ruscogenin­induced pancreatic cancer cell death. Finally, in vivo experiments demonstrated the antitumor effect of ruscogenin on pancreatic cancer xenografts in the absence of apparent toxicity. Taken collectively, the data demonstrated that ruscogenin exhibited anticancer effects in pancreatic cancer cells by inducing ferroptosis. The findings suggested that this compound may be further developed as a promising anticancer candidate for the treatment of pancreatic cancer.

NUSAP1 Promotes Gastric Cancer Tumorigenesis and Progression by Stabilizing the YAP1 Protein.

The Yes-associated protein (YAP1) is a main effector of the canonical Hippo pathway, which contributes greatly to tumor initiation, progression, and metastasis in multiple cancers, including gastric cancer (GC). Due to limited knowledge of YAP1 upregulation in cancer, it is a great challenge of therapeutic targets toward the Hippo-YAP1 pathway. Here, we identify nucleolar spindle-associated protein 1 (NUSAP1) as a novel binding partner of YAP1. The upregulation of NUSAP1 is associated with unfavorable clinical outcomes in GC patients, and NUSAP1 depletion impairs its oncogenic properties in vitro and in a xenograft model. Mechanistically, we discovered that NUSAP1 functions as a positive regulator of YAP1 protein stability, thereby inducing the transcription of Hippo pathway downstream target genes, such as CTGF and CYR61. More interestingly, we find that the cancer-promoting effects of NUSAP1 on GC cell growth, migration, and invasion are mainly mediated by YAP1. Furthermore, aberrant expression of NUSAP1 and YAP1 is highly correlated in GC cell lines and tissues. We herein clarify the role of the oncogenic NUSAP1-YAP1 axis in GC tumorigenesis and progression and, therefore, provide novel therapeutic targets for GC treatment.

UCHL3 promotes pancreatic cancer progression and chemo-resistance through FOXM1 stabilization.

The dysregulation of deubiquitinating enzymes has been reported to be important in the development of many human cancers, including pancreatic cancer. However, the precise role and potential mechanism of action of the deubiquitinating enzyme UCHL3 in pancreatic cancer progression and chemo-resistance, are poorly elucidated. In the current study, the consequences of UCHL3 knockdown in pancreatic cancer cells were evaluated via cell viability and colony formation assays. In vivo experiments were also conducted to confirm the effect of UCHL3 and FOXM1 depletion on tumor growth in nude mouse xenograft models. Cell migration and invasion were assessed by wound-healing and transwell assays, respectively. Co-immunoprecipitation (co-IP) and in vitro deubiquitination assays were performed to investigate the interactions between UCHL3 and FOXM1. Immunohistochemical (IHC) staining was utilized to examine the expression of UCHL3 and FOXM1 in pancreatic cancer tissues. Our results demonstrate that UCHL3 deubiquitinated and stabilized FOXM1, thereby potentiating proliferation, migration, and invasion of pancreatic cancer cells. Furthermore, knockdown of UCHL3 increased FOXM1 ubiquitination, which enhanced FOXM1 turnover and promoted pancreatic cancer cells' sensitivity to gemcitabine. High UCHL3 expression was positively associated with FOXM1 expression level in pancreatic cancer patient samples. Collectively, our study established the UCHL3-FOXM1 axis as a pivotal driver of pancreatic cancer progression and gemcitabine resistance and provided evidence for the potential therapeutic benefit of targeting the UCHL3-FOXM1 axis for pancreatic cancer treatment.

miR­381 and miR­489 suppress cell proliferation and invasion by targeting CUL4B via the Wnt/ß­catenin pathway in gastric cancer.

Accumulating evidence has highlighted the critical role of cullin 4B (CUL4B) in driving tumourigenesis in several malignancies, including gastric cancer (GC); however, the mechanisms underlying CUL4B upregulation remain unclear. The dysregulation of microRNAs (miRNAs or miRs) is known to be involved in tumourigenesis. In this study, we report that the expression of miR­381 and miR­489 is downregulated and is negatively correlated with that of CUL4B in GC tissues and cell lines. Further analysis verified that miR­381 and miR­489 directly targeted CUL4B. CUL4B silencing inhibited cell proliferation, migration and invasion by inactivating the Wnt/ß­catenin pathway. miR­381/miR­489 overexpression recapitulated the effects of CUL4B silencing, while CUL4B restoration negated the suppressive effects induced by the ectopic expression of miR­381/miR­489. Furthermore, miR­381/miR­489 exerted tumour suppressive functions by inactivating the Wnt/ß­catenin pathway through the targeting of CUL4B. Taken together, the findings of this study suggest that the miR­381/miR­489­mediated expression of CUL4B modulates the proliferation and invasion of GC cells via the Wnt/ß­catenin pathway, which indicates that the miR­381/miR­489­CUL4B axis is critical in the control of GC tumourigenesis.

TRIM44, a crucial target of miR-410, functions as a potential oncogene in osteosarcoma.

PURPOSE: Mounting evidence highlights the essential role of TRIM44 in tumor initiation and malignant progression in several cancers; however, the function of TRIM44 in osteosarcoma (OS) remains unknown. In this study, we aim to investigate the role of TRIM44 and reveal its regulation by deregulated miRNAs in OS. MATERIALS AND METHODS: The expression profiles of TRIM44 were examined by immunohistochemistry, Western blotting, and qRT-PCR. The biological functions of TRIM44 were investigated through siRNA-mediated knockdown experiments. The regulation of TRIM44 by miR-410 was confirmed by Western blotting, dual luciferase reporter assays, and rescue experiments. RESULTS: TRIM44 was upregulated in OS tissues and cell lines, and its overexpression was positively correlated with TNM stage, metastasis, and recurrence. Knockdown of TRIM44 in OS cells suppressed cell proliferation, migration, invasion, and epithelial-mesenchymal transition. In addition, we identified TRIM44 as a novel target gene of miR-410 and miR-410 was remarkably downregulated in OS. Moreover, overexpression of miR-410 suppressed proliferation, migration, invasion, and epithelial-mesenchymal transition of OS cells by directly targeting TRIM44 expression. Furthermore, reintroduction of TRIM44 partially reversed miR-410-induced inhibitory effects on OS cells. CONCLUSION: Collectively, our findings indicate that the miR-410/TRIM44 link is critical in the control of OS progression.

SPIN1 promotes tumorigenesis by blocking the uL18 (universal large ribosomal subunit protein 18)-MDM2-p53 pathway in human cancer.

Ribosomal proteins (RPs) play important roles in modulating the MDM2-p53 pathway. However, less is known about the upstream regulators of the RPs. Here, we identify SPIN1 (Spindlin 1) as a novel binding partner of human RPL5/uL18 that is important for this pathway. SPIN1 ablation activates p53, suppresses cell growth, reduces clonogenic ability, and induces apoptosis of human cancer cells. Mechanistically, SPIN1 sequesters uL18 in the nucleolus, preventing it from interacting with MDM2, and thereby alleviating uL18-mediated inhibition of MDM2 ubiquitin ligase activity toward p53. SPIN1 deficiency increases ribosome-free uL18 and uL5 (human RPL11), which are required for SPIN1 depletion-induced p53 activation. Analysis of cancer genomic databases suggests that SPIN1 is highly expressed in several human cancers, and its overexpression is positively correlated with poor prognosis in cancer patients. Altogether, our findings reveal that the oncogenic property of SPIN1 may be attributed to its negative regulation of uL18, leading to p53 inactivation.

Cancer-mutated ribosome protein L22 (RPL22/eL22) suppresses cancer cell survival by blocking p53-MDM2 circuit.

Several ribosomal proteins (RPs) in response to various ribosomal stressors have been shown to play a critical role in p53-dependent regulation of cell cycle arrest, apoptosis and tumor suppression. Here, we report ribosomal protein L22 (RPL22/eL22) as a novel p53 activator highly mutated (mostly deletion mutation) in various types of human cancers, but not essential for ribosomal biogenesis in normal cells. Ectopic expression of RPL22/eL22 suppressed the colony formation of cancer cells in a p53-dependent manner, whereas knockdown of RPL22/eL22 significantly compromised p53 activation by Actinomycin D, rescuing p53-induced G1/G0 cell cycle arrest. Interestingly, human tumors with RPL22/eL22 deletion appeared to sustain wild type p53. Mechanistically, RPL22/eL22 bound to MDM2 acidic domain and inhibited MDM2-mediated p53 ubiquitination and degradation, hence extending the half-life of p53. Ribosome-profiling analysis revealed that induction of ribosomal stress by Actinomycin D leads to the increase of ribosome-free RPL22/eL22 pool. Also, RPL22/eL22 formed a complex with MDM2/RPL5/uL18/RPL11/uL5 and synergized with RPL11/uL5 to activate p53. Furthermore, the N terminus of RPL22/eL22 bound to MDM2, while the C terminus interacted with RPL5/uL18/RPL11/uL5; both of these two fragments activated p53 by inhibiting MDM2. Our study indicates that RPL22/eL22 highly mutated in human cancers plays an anti-cancer role likely through regulation of the MDM2-p53 feedback loop, and also suggests that targeting the RPL22/eL22-MDM2-p53 pathway could be a potential strategy for future development of anti-cancer therapy.

TRIM24 promotes the aggression of gastric cancer via the Wnt/ß-catenin signaling pathway.

Tripartite motif-containing 24 (TRIM24) is important in tumor development and progression. However, the role of TRIM24 in gastric cancer (GC) and the mechanisms underlying the dysregulated expression of TRIM24 remain to be fully elucidated. In the present study, it was found that TRIM24 was frequently overexpressed in GC cell lines and tissues compared with normal controls, as determined by western blotting and immunohistochemical staining. The high nuclear expression of TRIM24 was correlated with the depth of invasion (P=0.007), tumor-node-metastasis stage (P=0.005), and lymph node metastasis (P=0.027), and shorter overall survival rates (P=0.010) in patients with GC. Small interfering RNA-mediated knockdown of TRIM24 inhibited cell proliferation, colony formation, migration, invasion and the nuclear accumulation of ß-catenin, and it delayed cell cycle progression and induced apoptosis. In addition, the expression of TRIM24 was positively correlated with that of ß-catenin in GC tissues. TRIM24 knockdown decreased the expression of Wnt/ß-catenin target genes, whereas the activation of Wnt/ß-catenin signaling by lithium chloride reversed the effects of TRIM24 knockdown. Taken together, these data suggested that TRIM24 was a prognostic or potential therapeutic target for patients with GC and was important in the activation of the Wnt/ß-catenin pathway during the progression of GC.