α-Catulin promotes cancer stemness by antagonizing WWP1-mediated KLF5 degradation in lung cancer.

Background: The cytoskeletal linker protein α-Catulin has been shown to be important for tumor progression in various cancers. However, its role in the regulation of cancer stemness remains unclear. Methods: Phenotypic effects of α-Catulin on the cancer stem cell (CSC)-like properties and metastasis were examined by in vitro sphere formation assay, migration assay, invasion assay, and in vivo xenografted animal models. Yeast two-hybrid assay, co-immunoprecipitation assay, and cycloheximide chase assay were performed to confirm the effect of α-Catulin on the WWP1-mediated degradation of KLF5. CPTAC and TCGA database were analyzed to determine the clinical association of α-Catulin, KLF5, and stemness-associated signatures in lung adenocarcinoma. Results: We report that α-Catulin increases cancer stem-like properties in non-small cell lung cancer (NSCLC). The expression of α-Catulin is elevated in tumor spheres compared to sphere-derived adherent cells and promotes the acquisition of cancer stemness characteristics in vitro and in vivo. Mechanistically, the interaction of α-Catulin and the C-terminal region of Kruppel-like transcription factor KLF5 results in the inhibition of WWP1-mediated degradation of KLF5. Accordingly, increased protein expression of KLF5 is observed in clinical specimens of lung adenocarcinoma with high expression of α-Catulin compared to specimens with low α-Catulin-expression. Knockdown of KLF5 abrogates α-Catulin-driven cancer stemness. α-Catulin is known to interact with integrin-linked kinase (ILK). Notably, an ILK inhibitor disrupts the α-Catulin-KLF5 interaction, promotes the degradation of KLF5, and decreases α-Catulin-driven cancer stemness. Importantly, we identify a CTNNAL1/ILK/KLF5 three-gene signature for predicting poor overall survival in patients with lung adenocarcinoma. Conclusions: These findings reveal a molecular basis of α-Catulin-enhanced KLF5 signaling and highlight a role for α-Catulin in promoting cancer stemness.

Imaging and biodistribution of radiolabeled SP90 peptide in BT-483 tumor bearing mice.

The objective of this study was to evaluate radiolabeled DOTA-SP90 as a radiotracer for breast cancer. The in vitro competition assay showed that radiolabeled DOTA-SP90 had significant binding affinity to BT-483 cancer cells. Biodistribution, nanoSPECT/CT and nanoPET/CT imaging results indicated that radiolabeled DOTA-SP90 can accumulate in tumors. In addition, radiolabeled DOTA-SP90 peptides can also detect metastatic tumors. Therefore, radiolabeled SP90 peptide may provide the potential capability as diagnostic agent for breast cancer patients.

A DNA Aptamer Targeting Galectin-1 as a Novel Immunotherapeutic Strategy for Lung Cancer.

Galectin-1 (Gal-1) is a pleiotropic homodimeric ß-galactoside-binding protein with a single carbohydrate recognition domain. It has been implicated in several biological processes that are important during tumor progression. Several lines of evidence have indicated that Gal-1 is involved in cancer immune escape and induces T cell apoptosis. These observations all emphasized Gal-1 as a novel target for cancer immunotherapy. Here, we developed a novel Gal-1-targeting DNA aptamer (AP-74 M-545) and demonstrated its antitumor effect by restoring immune function. AP-74 M-545 binds to Gal-1 with high affinity. AP-74 M-545 targets tumors in murine tumor models but suppresses tumor growth only in immunocompetent C57BL/6 mice, not in immunocompromised non-obese diabetic (NOD)/severe combined immunodeficiency (SCID) mice. Immunohistochemistry revealed increased CD4+ and CD8+ T cells in AP-74 M-545-treated tumor tissues. AP-74 M-545 suppresses T cell apoptosis by blocking the binding of Gal-1 to CD45, the main receptor and apoptosis mediator of Gal-1 on T cells. Collectively, our data suggest that the Gal-1 aptamer suppresses tumor growth by blocking the interaction between Gal-1 and CD45 to rescue T cells from apoptosis and restores T cell-mediated immunity. These results indicate that AP-74 M-545 may be a potential strategy for cancer immunotherapy.

Targeting FXYD2 by cardiac glycosides potently blocks tumor growth in ovarian clear cell carcinoma.

Ovarian clear cell carcinoma (OCCC) is an aggressive neoplasm with a high recurrence rate that frequently develops resistance to platinum-based chemotherapy. There are few prognostic biomarkers or targeted therapies exist for patients with OCCC. Here, we identified that FXYD2, the modulating subunit of Na+/K+-ATPases, was highly and specifically expressed in clinical OCCC tissues. The expression levels of FXYD2 were significantly higher in advanced-stage of OCCC and positively correlated with patients' prognoses. Silencing of FXYD2 expression in OCCC cells inhibited Na+/K+-ATPase enzyme activity and suppressed tumor growth via induction of autophagy-mediated cell death. We found that high FXYD2 expression in OCCC was transcriptionally regulated by the transcriptional factor HNF1B. Furthermore, up-regulation of FXYD2 expression significantly increased the sensitivity of OCCC cells to cardiac glycosides, the Na+/K+-ATPase inhibitors. Two cardiac glycosides, digoxin and digitoxin, had a great therapeutic efficacy in OCCC cells in vitro and in vivo. Taken together, our results demonstrate that FXYD2 is functionally upregulated in OCCC and may serve as a promising prognostic biomarker and therapeutic target of cardiac glycosides in OCCC.

MDA-9/Syntenin-Slug transcriptional complex promote epithelial-mesenchymal transition and invasion/metastasis in lung adenocarcinoma.

Melanoma differentiation-associated gene-9 (MDA-9)/Syntenin is a novel therapeutic target because it plays critical roles in cancer progression and exosome biogenesis. Here we show that Slug, a key epithelial-mesenchymal-transition (EMT) regulator, is a MDA-9/Syntenin downstream target. Mitogen EGF stimulation increases Slug expression and MDA-9/Syntenin nuclear translocation. MDA-9/Syntenin uses its PDZ1 domain to bind with Slug, and this interaction further leads to HDAC1 recruitment, up-regulation of Slug transcriptional repressor activity, enhanced Slug-mediated EMT, and promotion of cancer invasion and metastasis. The PDZ domains and nuclear localization of MDA-9/Syntenin are both required for promoting Slug-mediated cancer invasion. Clinically, patients with high MDA-9/Syntenin and high Slug expressions were associated with poor overall survival compared to those with low expression in lung adenocarcinomas. Our findings provide evidence that MDA-9/Syntenin acts as a pivotal adaptor of Slug and it transcriptionally enhances Slug-mediated EMT to promote cancer invasion and metastasis.

α-Catulin drives metastasis by activating ILK and driving an αvß3 integrin signaling axis.

α-Catulin is an oncoprotein that helps sustain proliferation by preventing cellular senescence. Here, we report that α-catulin also drives malignant invasion and metastasis. α-Catulin was upregulated in highly invasive non-small cell lung cancer (NSCLC) cell lines, where its ectopic expression or short-hairpin RNA-mediated attenuation enhanced or limited invasion or metastasis, respectively. α-Catulin interacted with integrin-linked kinase (ILK), a serine/threonine protein kinase implicated in cancer cell proliferation, antiapoptosis, invasion, and angiogenesis. Attenuation of ILK or α-catulin reciprocally blocked cell migration and invasion induced by the other protein. Mechanistic investigations revealed that α-catulin activated Akt-NF-κB signaling downstream of ILK, which in turn led to increased expression of fibronectin and integrin αvß3. Pharmacologic or antibody-mediated blockade of NF-κB or αvß3 was sufficient to inhibit α-catulin-induced cell migration and invasion. Clinically, high levels of expression of α-catulin and ILK were associated with poor overall survival in patients with NSCLC. Taken together, our study shows that α-catulin plays a critical role in cancer metastasis by activating the ILK-mediated Akt-NF-κB-αvß3 signaling axis.