Decreased HCRP1 promotes breast cancer metastasis by enhancing EGFR phosphorylation

Removal of hypersignaling endosomes by simaphagy

Activated transmembrane receptors continue to signal following endocytosis and are only silenced upon ESCRT-mediated internalization of the receptors into intralumenal vesicles (ILVs) of the endosomes. Accordingly, endosomes with dysfunctional receptor internalization into ILVs can cause sustained receptor signaling which has been implicated in cancer progression. Here, we describe a surveillance mechanism that allows cells to detect and clear physically intact endosomes with aberrant receptor accumulation and elevated signaling. Proximity biotinylation and proteomics analyses of ESCRT-0 defective endosomes revealed a strong enrichment of the ubiquitin-binding macroautophagy/autophagy receptors SQSTM1 and NBR1, a phenotype that was confirmed in cell culture and fly tissue. Live cell microscopy demonstrated that loss of the ESCRT-0 subunit HGS/HRS or the ESCRT-I subunit VPS37 led to high levels of ubiquitinated and phosphorylated receptors on endosomes. This was accompanied by dynamic recruitment of NBR1 and SQSTM1 as well as proteins involved in autophagy initiation and autophagosome biogenesis. Light microscopy and electron tomography revealed that endosomes with intact limiting membrane, but aberrant receptor downregulation were engulfed by phagophores. Inhibition of autophagy caused increased intra- and intercellular signaling and directed cell migration. We conclude that dysfunctional endosomes are surveyed and cleared by an autophagic process, simaphagy, which serves as a failsafe mechanism in signal termination.Abbreviations: AKT: AKT serine/threonine kinase; APEX2: apurinic/apyrimidinic endodoexyribonuclease 2; ctrl: control; EEA1: early endosome antigen 1; EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; ESCRT: endosomal sorting complex required for transport; GFP: green fluorescent protein; HGS/HRS: hepatocyte growth factor-regulated tyrosine kinase substrate; IF: immunofluorescence; ILV: intralumenal vesicle; KO: knockout; LIR: LC3-interacting region; LLOMe: L-leucyl-L-leucine methyl ester (hydrochloride); MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK1/ERK2: mitogen-activated protein kinase 1; MAPK3/ERK1: mitogen-activated protein kinase 3; NBR1: NBR1 autophagy cargo receptor; PAG10: Protein A-conjugated 10-nm gold; RB1CC1/FIP200: RB1 inducible coiled-coil 1; siRNA: small interfering RNA; SQSTM1: sequestosome 1; TUB: Tubulin; UBA: ubiquitin-associated; ULK1: unc-51 like autophagy activating kinase 1; VCL: Vinculin; VPS37: VPS37 subunit of ESCRT-I; WB: western blot; WT: wild-type.

ER stress elicits non-canonical CASP8 (caspase 8) activation on autophagosomal membranes to induce apoptosis

The VPS37A gene encodes a subunit of the endosomal sorting complex required for transport (ESCRT)-I complex that is frequently lost in a wide variety of human solid cancers. We have previously demonstrated the role of VPS37A in directing the ESCRT membrane scission machinery to seal the phagophore for autophagosome completion. Here, we report that VPS37A-deficient cells exhibit an accumulation of the apoptotic initiator CASP8 (caspase 8) on the phagophore and are primed to undergo rapid apoptosis through the intracellular death-inducing signaling complex (iDISC)-mediated CASP8 activation upon exposure to endoplasmic reticulum (ER) stress. Using CRISPR-Cas9 gene editing and comparative transcriptome analysis, we identified the ATF4-mediated stress response pathway as a crucial mediator to elicit iDISC-mediated apoptosis following the inhibition of autophagosome closure. Notably, ATF4-mediated iDISC activation occurred independently of the death receptor TNFRSF10B/DR5 upregulation but required the pro-apoptotic transcriptional factor DDIT3/CHOP to enhance the mitochondrial amplification pathway for full-activation of CASP8 in VPS37A-deficient cells stimulated with ER stress inducers. Our analysis also revealed the upregulation of NFKB/NF-kB signaling as a potential mechanism responsible for restraining iDISC activation and promoting cell survival upon VPS37A depletion. These findings have important implications for the future development of new strategies to treat human cancers, especially those with VPS37A loss.Abbreviations: ATG: autophagy related; BMS: BMS-345541; CASP: caspase; CHMP: charged multivesicular body protein; DKO: double knockout; Dox: doxycycline; ER: endoplasmic reticulum; ESCRT: endosomal sorting complex required for transport; gRNA: guide RNA; GSEA: gene set enrichment analysis; GSK157: GSK2656157; iDISC: intracellular death-inducing signaling complex; IKK: inhibitor of NFKB kinase; IPA: ingenuity pathway analysis; KO: knockout; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; NFKB/NF-kB: nuclear factor kappa B; OZ: 5Z-7-oxozeaenol; RNA-seq: RNA sequencing; UPR: unfolded protein response; TFT: transcription factor target; THG: thapsigargin; TUN: tunicamycin; VPS: vacuolar protein sorting.

MiR-320d Inhibits Progression of EGFR-Positive Colorectal Cancer by Targeting TUSC3

Background: The mechanism of miR-320d in EGFR-positive colorectal cancer (CRC) has not been fully elucidated. The aim of the present study was to explore the molecular mechanism of miR-320d in CRC.

Methods: The miRNA microarray analysis was conducted to identify differential expressed miRNAs. The expression of miR-320d was validated using quantitative real-time PCR. EGFR-positive CRC cells were transfected with miR-320d mimic and inhibitor, after which cell proliferation, migration, and invasion were assayed. The relationship between miR-320d and TUSC3 was confirmed using bioinformatics and dual-luciferase reporter gene assays. Proteins involved in signaling pathways and the epithelial–mesenchymal transition were detected with Western blot.

Results: We found that the miR-320d expression is associated with tumor size and distant metastasis in colorectal cancer. Overexpression of miR-320d in EGFR-positive HCT-116 and SW480 cells decreased not only the proliferation ability but also the invasion and migration ability. In addition, miR-320d had the ability to inhibit epithelial-to-mesenchymal transition. Luciferase assays revealed that miR-320d directly targets the 3′-UTR of TUSC3. TUSC3 was downregulated by miR-320d at both the protein and mRNA levels in EGFR-positive CRC cell lines.

Conclusion: Generally, our results demonstrated that miR-320d could inhibit the malignant phenotype of EGFR-positive CRC through targeting TUSC3. The miR-320d might be a potential therapeutic target for EGFR-positive CRC.

Concurrent depletion of Vps37 proteins evokes ESCRT-I destabilization and profound cellular stress responses

Molecular details of how endocytosis contributes to oncogenesis remain elusive. Our in silico analysis of colorectal cancer (CRC) patients revealed stage-dependent alterations in the expression of 112 endocytosis-related genes. Among them, transcription of the endosomal sorting complex required for transport (ESCRT)-I component VPS37B was decreased in the advanced stages of CRC. Expression of other ESCRT-I core subunits remained unchanged in the investigated dataset. We analyzed an independent cohort of CRC patients, which also showed reduced VPS37A mRNA and protein abundance. Transcriptomic profiling of CRC cells revealed non-redundant functions of Vps37 proteins. Knockdown of VPS37A and VPS37B triggered p21 (CDKN1A)-mediated inhibition of cell proliferation and sterile inflammatory response driven by the nuclear factor (NF)-κB transcription factor and associated with mitogen-activated protein kinase signaling. Co-silencing of VPS37C further potentiated activation of these independently induced processes. The type and magnitude of transcriptional alterations correlated with the differential ESCRT-I stability upon individual and concurrent Vps37 depletion. Our study provides novel insights into cancer cell biology by describing cellular stress responses that are associated with ESCRT-I destabilization.

HCRP1 inhibits cell proliferation and invasion and promotes chemosensitivity in esophageal squamous cell carcinoma

Hepatocellular carcinoma related protein 1 (HCRP1), which is essential for internalization and degradation of ubiquitinated membrane receptors, was reported to play crucial roles in cancer pathogenesis and progression. However, the functional roles of HCRP1 in esophageal squamous cell carcinoma (ESCC) remain unknown. In this study, we investigated the effects of HCRP1 on ESCC cells and the underlying mechanism. Our results demonstrated that HCRP1 was lowly expressed in ESCC tissues and cell lines. Overexpression of HCRP1 significantly suppressed ESCC cell proliferation and invasion as well as the epithelial-mesenchymal transition (EMT) process. Furthermore, HCRP1 increased the sensitivity of ESCC cells towards cisplatin/fluorouracil. Mechanistically, HCRP1 inhibited the activity of Wnt/β-catenin signaling pathway in ESCC cells. In conclusion, these findings indicated that HCRP1 suppressed ESCC cell proliferation and invasion through regulation of the Wnt/β-catenin pathway. Therefore, HCRP1 may function as a tumor suppressor in ESCC progression.

MicroRNA-19a acts as a prognostic marker and promotes prostate cancer progression via inhibiting VPS37A expression

Prostate cancer (PCa) is a leading cause of cancer-related deaths among males worldwide. However, the molecular mechanisms underlying the progression of PCa remain unclear. Despite several reported miRNAs in prostate cancer, these reports lacked system-level identification of differentially expressed miRNAs in large sample size. Moreover, it's still largely unknown how miRNAs result in tumorigenesis and progression of PCa. Therefore, by analyzing three public databases, we identified 16 upregulated miRNAs and 13 downregulated miRNAs, and validated miR-19a was one of the most upregulated miRNAs using qRT-PCR. The dual-luciferase reporter assays indicated VPS37A was a potential target of miR-19a. Functional assays revealed miR-19a served as an oncogene by inhibiting VPS37A. Notably, a significant inverse correlation of miR-19a and VPS37A expression was observed in PCa specimens. Moreover, miR-19a-high and VPS37A-low phenotypes were associated with poor prognosis with biochemical recurrence-free probability. In this study, we confirmed the oncogenic role of miR-19a via targeting VPS37A in PCa, identifying miR-19a and VPS37A as diagnosis and therapeutic biomarkers for PCa.

Inhibition of EGF-induced migration and invasion by sulfated polysaccharide of Sepiella maindroni ink via the suppression of EGFR/Akt/p38 MAPK/MMP-2 signaling pathway in KB cells

SIP-SII, the sulfated Sepiella maindroni ink polysaccharide (SIP), has been manifested to possess anti-tumor and anti-metastasis activity in vivo and in vitro. In the present study, we evaluated its inhibitory effect on the epidermal growth factor (EGF)-induced migration and invasion of human epidermoid carcinoma cell (KB cell line) as well as the related signaling pathways. The results of MTT assay indicated that SIP-SII inhibited the proliferation of KB cells in a concentration and time dependent manner. Notably, the attenuation of cell growth by SIP-SII was enlarged in the presence of EGF. The wound healing assay and transwell invasion assay were used to evaluate the effect of SIP-SII on the EGF-induced migration and invasion of KB cells and the results showed that SIP-SII markedly attenuated the EGF-induced migration and invasion. Besides, the EGF-induced matrix metalloproteinase-2 (MMP-2) expression was also suppressed by SIP-SII. However, SIP-SII showed no significant inhibition of the EGF-induced matrix metalloproteinase-9 (MMP-9) expression. Further research revealed that SIP-SII decreased the EGF-induced phosphorylation of epidermal growth factor receptor (EGFR), Akt and p38, but no significant suppression on EGF-induced phosphorylation of extracellular signal-regulated kinase 1 and 2 (Erk1/2) and c-Jun N-terminal kinases (JNK) by SIP-SII treatment was observed. The involvement of EGFR/Akt/p38 pathway was confirmed by evidence that SIP-SII would enlarge the inhibitory effect of the specific signal pathway inhibitors. These results indicate that SIP-SII has the potential to be used as the inhibitor of tumor metastasis especially for cancers characterized by over-activation of EGF/EGFR signaling.