TGM1/3-mediated transamidation of Exo70 promotes tumor metastasis upon LKB1 inactivation.

Exo70, a key exocyst complex component, is crucial for cell motility and extracellular matrix (ECM) remodeling in cancer metastasis. Despite its potential as a drug target, Exo70's post-translational modifications (PTMs) are poorly characterized. Here, we report that Exo70 is transamidated on Gln5 with Lys56 of cystatin A by transglutaminases TGM1 and TGM3, promoting tumor metastasis. This modification enhances Exo70's association with other exocyst subunits, essential for secreting matrix metalloproteinases, forming invadopodia, and delivering integrins to the leading edge. Tumor suppressor liver kinase B1 (LKB1), whose inactivation accelerates metastasis, phosphorylates TGM1 and TGM3 at Thr386 and Thr282, respectively, to inhibit their interaction with Exo70 and the following transamidation. Cantharidin, a US Food and Drug Administration (FDA)-approved drug, inhibits Exo70 transamidation to restrain tumor cell migration and invasion. Together, our findings highlight Exo70 transamidation as a key molecular mechanism and target and propose cantharidin as a therapeutic strategy with direct clinical translational value for metastatic cancers, especially those with LKB1 loss.

The Prognostic Value and the Oncogenic and Immunological Roles of Vacuolar Protein Sorting Associated Protein 26 A in Pancreatic Adenocarcinoma.

The identification of the prognostic markers and therapeutic targets might benefit the diagnosis and treatment of pancreatic adenocarcinoma (PAAD), one of the most aggressive malignancies. Vacuolar protein sorting associated protein 26 A (VPS26A) is a candidate prognosis gene for hepatocellular carcinoma, but its expression and function in PAAD remain unknown. The mRNA and protein expression of VPS26A in PAAD was explored and validated by bioinformatics and immunohistochemical analysis. The correlation between VPS26A expression and various clinical parameters, genetic status, diagnostic and prognostic value, survival and immune infiltration were evaluated, and the co-expressed gene-set enrichment analysis for VPS26A was performed. Cytologic and molecular experiments were further carried out to investigate the role and potential mechanism of VPS26A in PAAD. The mRNA and protein levels of VPS26A were elevated in PAAD tissues. High VPS26A expression was associated with the advanced histological type, tumor stage simplified, smoking status and tumor mutational burden score, and the poor prognosis of PAAD patients. VPS26A expression was significantly correlated with immune infiltration and immunotherapy response. VPS26A-co-expressed genes were mainly enriched in the regulation of cell adhesion and actin cytoskeleton and the immune-response-regulating signaling pathway. Our experiments further demonstrated that VPS26A promoted the proliferation, migration and invasion potentials of PAAD cell lines through activating the EGFR/ERK signaling. Our study suggested that VPS26A could be a potential biomarker and a therapeutic target for PAAD through comprehensive regulation of its growth, migration and immune microenvironment.

The HNF4α-BC200-FMR1-Positive Feedback Loop Promotes Growth and Metastasis in Invasive Mucinous Lung Adenocarcinoma.

Invasive mucinous lung adenocarcinoma (IMA) is a subtype of lung adenocarcinoma with a strong invasive ability. IMA frequently carries "undruggable" KRAS mutations, highlighting the need for new molecular targets and therapies. Nuclear receptor HNF4α is abnormally enriched in IMA, but the potential of HNF4α to be a therapeutic target for IMA remains unknown. Here, we report that P2 promoter-driven HNF4α expression promotes IMA growth and metastasis. Mechanistically, HNF4α transactivated lncRNA BC200, which acted as a scaffold for mRNA binding protein FMR1. BC200 promoted the ability of FMR1 to bind and regulate stability of cancer-related mRNAs and HNF4α mRNA, forming a positive feedback circuit. Mycophenolic acid, the active metabolite of FDA-approved drug mycophenolate mofetil, was identified as an HNF4α antagonist exhibiting anti-IMA activities in vitro and in vivo. This study reveals the role of a HNF4α-BC200-FMR1-positive feedback loop in promoting mRNA stability during IMA progression and metastasis, providing a targeted therapeutic strategy for IMA. SIGNIFICANCE: Growth and metastatic progression of invasive mucinous lung adenocarcinoma can be restricted by targeting HNF4α, a critical regulator of a BC200-FMR1-mRNA stability axis.

Identification of Chaetocin as a Potent non-ROS-mediated Anticancer Drug Candidate for Gastric Cancer.

Chaetocin, a natural product extracted from Chaetomium species, possesses anticancer effects in several kinds of tumors. However, it remains unclear whether the potential indication for chaetocin could also include human gastric cancer. We found here that chaetocin induced caspase-dependent and -independent apoptosis in human gastric cancer cell lines, which greatly depended on BID-mediated AIF translocation. Despite not increasing the intercellular ROS levels in gastric cancer cells, chaetocin did cause a reduction in mitochondrial membrane potential probably through its regulation on the expression of Bcl-2 and BAX. Chaetocin could also induce autophagy in gastric cancer cells; blocking autophagy by chloroquine enhanced the cytotoxicity of chaetocin. Chaetocin was further found to suppress the growth of gastric cancer xenograft in nude mice. Therefore, our study provides first evidence that chaetocin has an anticancer efficacy against gastric cancer and the combined use of chaetocin with autophagy inhibitors may enhance the therapeutic effect for gastric cancer. As chronic and exorbitant ROS levels instigate drug resistance, chaetocin, which eradicates gastric cancer cells without increasing ROS levels, may initiate a new line of non-ROS-mediated anti-tumor strategy.

Exo70 is an independent prognostic factor in colon cancer.

Exo70, a key component of the Exocyst complex, plays important roles in human cancer progression beyond exocytosis. However, the expression of Exo70 and its prognostic value for patients with colon cancer has not been well investigated to date. In this study, we observed that the mRNA and protein levels of Exo70 were upregulated in 11 of 13 colon cancer tissues, compared with their normal counterparts, which was validated by immunohistochemical analysis in a tissue microarray containing 89 pairs of colon cancer tissues and the matched adjacent normal tissues. Statistical analysis revealed that Exo70 expression is positively correlated with tumor size, invasion depth, TNM stage and distant metastasis. Kaplan-Meier survival analysis showed that colon cancer patients with higher Exo70 expression have a poorer clinical outcome than those with lower Exo70 expression. Multivariate Cox regression analysis revealed that Exo70, age and distant metastasis were there independent prognostic factors for overall survival rate of colon cancer patients. Through gain- and loss of Exo70 in colon cancer cells, we found that Exo70 could enhance the migration ability of colon cancer cells. Taken together, our studies revealed that Exo70 might be a promising negative prognostic factor and a potential therapeutic target for colon cancer.

Seed Oil of Brucea javanicaInduces Cell Cycle Arrest and Apoptosis via Reactive Oxygen Species-Mediated Mitochondrial Dysfunction in Human Lung Cancer Cells.

Brucea javanica oil (BJO), a traditional herbal medicine extracted from the seeds of B. javanica, has been clinically used to treat non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) in combination with chemotherapy or radiotherapy in China. However, how BJO exerts this antitumor effect is still largely unknown. Here, effects of BJO on the growth of NSCLC and SCLC cell lines were investigated by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenytetrazolium Bromide (MTT) assay, and the results showed that BJO inhibited the proliferation of A549 cells (NSCLC) and H446 cells (SCLC). Further studies revealed that BJO induced G0/G1 arrest partly via regulating p53 and cyclin D1 in these two cell lines. BJO also has pro-apoptotic effect on H446 and A549 cells through mitochondria/caspase-mediated pathway, which was initiated by the accumulation of intracellular reactive oxygen species (ROS). These findings thus revealed the molecular mechanisms underlying the antitumor effect of BJO on SCLC and NSCLC, which may benefit the further clinical application of BJO.

Exo70 is transcriptionally up-regulated by hepatic nuclear factor 4α and contributes to cell cycle control in hepatoma cells.

Exo70, a member of the exocyst complex, is involved in cell exocytosis, migration, invasion and autophagy. However, the expression regulation and function of Exo70 in hepatocellular carcinoma are still poorly understood. In this study, we found Exo70 expression in human hepatoma cells was greatly reduced after knocking down hepatic nuclear factor 4α (HNF4α), the most important and abundant transcription factor in liver. This regulation occurred at the transcriptional level but not post-translational level. HNF4α transactivated Exo70 promoter through directly binding to the HNF4α-response element in this promoter. Cell cycle analysis further revealed that down-regulation of HNF4α and Exo70 was essential to berberine-stimulated G2/M cell cycle arrest in hepatoma cells. Moreover, knocking down either Exo70 or HNF4α induced G2/M phase arrest of hepatoma cells. Exo70 acted downstream of HNF4α to stimulate G2/M transition via increasing Cdc2 expression. Together, our results identify Exo70 as a novel transcriptional target of HNF4α to promote cell cycle progression in hepatoma, thus provide a basis for the development of therapeutic strategies for hepatocellular carcinoma.