Identification of the PAG1 gene as a novel target of inherent radioresistance in human laryngeal carcinoma cells

Curcumin potentiates laryngeal squamous carcinoma radiosensitivity via NF-ΚB inhibition by suppressing IKKγ expression

Context: Curcumin has shown efficacy in promoting radiosensitivity combined with radiotherapy. However, the role and mechanism of curcumin on radiosensitivity in laryngeal squamous cell cancer (LSCC) is largely unknown.Objective: The aim of our study is to explore the role of IKKγ-NF-κB signaling in curcumin enhancing LSCC cell radiosensitivity in vitro.Materials and methods: Curcumin and X-ray were used to induce cell DNA damage and apoptosis, or inhibit cell clone formation. IKKγ siRNA and plasmid were used to change IKKγ expression. The CCK8 assay was used to detect cell viability. Clone formation ability was analyzed using a clonogenic assay, cell apoptosis was examined using flow cytometry, an immunofluorescence assay was used to detect DNA damage, while mRNA and protein levels were assayed using real time PCR and western blotting, respectively.Results: Curcumin significantly enhanced irradiation-induced DNA damage and apoptosis, while weakening clone-forming abilities of LSCC cell line Hep2 and Hep2-max. Compared to Hep2 cells, Hep2-max cells are more sensitive to curcumin post-irradiation. Curcumin suppressed irradiation-induced NF-κB activation by suppressing IKKγ expression, but not IKKα and IKKβ. Overexpression of IKKγ decreased irradiation-induced DNA damage and apoptosis, while promoting clone-forming abilities of Hep2 and Hep2-max cells. IKKγ overexpression further increased expression of NF-κB downstream genes, Bcl-XL, Bcl-2, and cyclin D1. Conversely, IKKγ silencing enhanced irradiation-induced DNA damage and apoptosis, but promoted clone formation in Hep2 and Hep2-max cells. Additionally, IKKγ silencing inhibited expression of Bcl-XL, Bcl-2, and cyclin D1.Conclusions: Curcumin enhances LSCC radiosensitivity via NF-ΚB inhibition by suppressing IKKγ expression.

Identification of Integrin β1 as a Novel PAG1-Interacting Protein Involved in the Inherent Radioresistance of Human Laryngeal Carcinoma

Inherent radioresistance plays a crucial role in the failure of radiotherapy. Using the inherent radioresistant (Hep-2max) and radiosensitive (Hep-2min) cell lines established from the parental cell line Hep-2, we previously reported that phosphoprotein associated with glycosphingolipid-enriched microdomains 1(PAG1) overexpression in laryngeal carcinoma cells was correlated with inherent radioresistant phenotypes. However, the underlying mechanisms of this effect remain unknown. In the present study, we performed a proteomic screen to investigate the interactome of PAG1 in Hep-2max cells resulting in the identification of several interaction partners. Bioinformatic analysis and immunofluorescence experiments indicated the integrin β1 to be a crucial interaction partner of PAG1. PAG1 was also highly expressed in laryngeal carcinoma radioresistant tissues and showed co-localization with integrin β1. In addition, we demonstrated that integrin β1's binding to PAG1 could be interrupted by MβCD, an inhibitor of lipid rafts formation. Moreover, knockdown of integrin β1 by RNA interference sensitized radioresistant cells to irradiation. Importantly, we identified 2 potential interaction sites (Pro²¹⁶-Arg²³² and Asn³⁵⁶-Gly³⁷⁷) in the cytoplasmic domain of PAG1 using high throughput peptide arrays. Taken together, these results suggest that the binding of PAG1 to integrin β1 in lipid rafts is essential for inherent radioresistance of human laryngeal carcinoma.

Altered O-glycosylation is associated with inherent radioresistance and malignancy of human laryngeal carcinoma

Radioresistance (inherent or acquired) remains a major obstacle affecting the clinical outcome of radiotherapy for laryngeal carcinoma. Results from our laboratory and other groups suggest that aberrant glycosylation contributes to cancer acquired radioresistance. However, the role of glycosylation in inherent radioresistance of laryngeal carcinoma has not been fully uncovered. In this study, we investigated the glycan profiling of the inherent radioresistant (Hep-2max) and radiosensitive (Hep-2min) cell lines using lectin microarray analysis. The results revealed that the radioresistant cell line Hep-2max presented higher core 1-type O-glycans than the sensitive one. Further analysis of the O-glycan regulation by benzyl-α-GalNAc application in Hep-2max cells showed partial inhibition of the O-glycan biosynthesis and increased radiosensitivity. In addition, core 1 β1, 3-galactosyltransferase (C1GALT1) overexpression in Hep-2min cells enhanced cell migration, invasion, and radioresistance. Conversely, knockdown of C1GALT1 in Hep-2max cells was able to suppress these malignant phenotypes. Moreover, mechanistic investigations showed that C1GALT1 modified the O-glycans on integrin β1 and regulated its activity. The glycosylation-mediated radioresistance was further inhibited by anti-integrin β1 blocking antibody. Importantly, we also observed that core 1-type O-glycans expression was correlated with advanced tumor stage, metastasis, and poor survival of laryngeal carcinoma patients. These findings suggest that altered O-glycosylation can lead to the inherent radioresistance and progression, and therefore may be important for enhancing the efficacy of radiotherapy in laryngeal carcinoma.

Upregulation of PAG1/Cbp contributes to adipose-derived mesenchymal stem cells promoted tumor progression and chemoresistance in breast cancer

C-terminal Src kinase (Csk)-binding protein (Cbp) is a ubiquitously expressed transmembrane adaptor protein which regulating Src family kinase (SFK) activities. Although SFKs are well known for their involvement in breast cancer, the function of Cbp in breast carcinogenesis upon the adipose-tumor microenvironment has not been investigated. Here, we reported that adipose-derived mesenchymal stem cells (ASCs) induced increased expression of Cbp accompanied by enhanced cell proliferation and chemotherapy resistance in breast cancer cell MCF-7/ADR. Depletion of Cbp in breast cancer cell by RNA interference led to remarkable inhibition of cell proliferation, invasion as well as synergy with adriamycin hydrochloride to suppress the tumor growth. Furthermore, silencing of Cbp concomitantly inhibited the expression of phosphoryl of Src, AKT and mTOR signals. Our study highlights the underlying mechanism of cross interaction between ASCs and breast cancer cells, and indicates that PAG1/Cbp in breast cancer cell may modulate tumor progression and acquired chemoresistance in the ASCs-associated breast cancer microenvironment through Src and AKT/mTOR pathways.

"Stealth dissemination" of macrophage-tumor cell fusions cultured from blood of patients with pancreatic ductal adenocarcinoma

Here we describe isolation and characterization of macrophage-tumor cell fusions (MTFs) from the blood of pancreatic ductal adenocarcinoma (PDAC) patients. The MTFs were generally aneuploidy, and immunophenotypic characterizations showed that the MTFs express markers characteristic of PDAC and stem cells, as well as M2-polarized macrophages. Single cell RNASeq analyses showed that the MTFs express many transcripts implicated in cancer progression, LINE1 retrotransposons, and very high levels of several long non-coding transcripts involved in metastasis (such as MALAT1). When cultured MTFs were transplanted orthotopically into mouse pancreas, they grew as obvious well-differentiated islands of cells, but they also disseminated widely throughout multiple tissues in "stealth" fashion. They were found distributed throughout multiple organs at 4, 8, or 12 weeks after transplantation (including liver, spleen, lung), occurring as single cells or small groups of cells, without formation of obvious tumors or any apparent progression over the 4 to 12 week period. We suggest that MTFs form continually during PDAC development, and that they disseminate early in cancer progression, forming "niches" at distant sites for subsequent colonization by metastasis-initiating cells.

Warburg effect, hexokinase-II, and radioresistance of laryngeal carcinoma

Radiotherapy is now widely used as a part of multidisciplinary treatment approaches for advanced laryngeal carcinoma and preservation of laryngeal function. However, the mechanism of the radioresistance is still unclear. Some studies have revealed that the Warburg effect promotes the radioresistance of various malignant tumors, including laryngeal carcinoma. Among the regulators involved in the Warburg effect, hexokinase-II (HK-II) is a crucial glycolytic enzyme that catalyzes the first essential step of glucose metabolism. HK-II is reportedly highly expressed in some human solid carcinomas by many studies. But for laryngeal carcinoma, there is only one. Till now, no studies have directly targeted inhibited HK-II and enhanced the radiosensitivity of laryngeal carcinoma. Accumulating evidence has shown that dysregulated signaling pathways often result in HK-II overexpression. Here, we summarize recent advances in understanding the association among the Warburg effect, HK-II, and the radioresistance of laryngeal carcinoma. We speculate on the feasibility of enhancing radiosensitivity by targeted inhibiting HK-II signaling pathways in laryngeal carcinoma, which may provide a novel anticancer therapy.

Sodium glycididazole enhances the radiosensitivity of laryngeal cancer cells through downregulation of ATM signaling pathway

The purpose of this study was to evaluate the radiation-enhancing effect of sodium glycididazole, and the corresponding mechanisms of action on laryngeal cancer cells. Two laryngeal cancer cell lines (Hep-2 and UT-SCC-19A) were irradiated with X-rays in the presence or absence of sodium glycididazole. Cell survival, DNA damage and repair, cell apoptosis, cell cycle distribution, expression of proteins related to cell cycle checkpoint, and apoptosis were measured. Significantly increased DNA damages, decreased cells in the G1 phase, arrested cells at G2/M phase, decreased DNA repair protein XRCC1 foci formation, and enhanced cell apoptosis were observed in laryngeal cell lines treated by sodium glycididazole combined with irradiation compared with the irradiation alone. The combined treatment downregulated the protein expressions of ataxia-telangiectasia mutated (ATM), p-ATM, CHK2, and P53 but upregulated the protein expressions of MDM2 and Cdk2. This study indicates that sodium glycididazole enhances the radiosensitivity of laryngeal cancer cells through downregulation of ATM signaling pathway in vitro and in vivo.