Hypoxia is a major driving force of cancer invasion and metastasis. Here we show that death domain-associated protein (Daxx) acts to negatively regulate hypoxia-induced cell dissemination and invasion by inhibiting the HIF-1α/HDAC1/Slug pathway. Daxx directly binds to the DNA-binding domain of Slug, impeding histone deacetylase 1 (HDAC1) recruitment and antagonizing Slug E-box binding. This, in turn, stimulates E-cadherin and occludin expression and suppresses Slug-mediated epithelial–mesenchymal transition (EMT) and cell invasiveness. Under hypoxic conditions, stabilized hypoxia-inducible factor (HIF)-1α downregulates Daxx expression and promotes cancer invasion, whereas re-expression of Daxx represses hypoxia-induced cancer invasion. Daxx also suppresses Slug-mediated lung cancer metastasis in an orthotopic lung metastasis mouse model. Using clinical tumour samples, we confirmed that the HIF-1α/Daxx/Slug pathway is an outcome predictor. Our results support that Daxx can act as a repressor in controlling HIF-1α/HDAC1/Slug-mediated cancer cell invasion and is a potential therapeutic target for inhibition of cancer metastasis.

Human tumourous imaginal disc (Tid1), a human homologue of the Drosophila tumour suppressor protein Tid56, is involved in multiple intracellular signalling pathways such as apoptosis, cell proliferation, and cell survival. Here, we investigated the anti-tumourigenic activity of Tid1 in head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo. Firstly, the clinical association between Tid1 expression and progression of HNSCC was explored. It was found that expression of Tid1 was negatively associated with tumour status, recurrence, and survival prognosis using immunohistochemical analysis of primary HNSCC patient tumour tissue. Secondly, ectopic expression of Tid1 in HNSCC cells was shown to significantly inhibit cell proliferation, migration, invasion, anchorage-independent growth, and xenotransplantation tumourigenicity. Thirdly, we showed that overexpression of Tid1 attenuated EGFR activity and blocked the activation of AKT in HNSCC cells, which are known to be involved in the regulation of survival in HNSCC cells. On the other hand, ectopic expression of constitutively active AKT greatly reduced apoptosis induced by Tid1 overexpression. Together, these findings suggest that Tid1 functions as a tumour suppressor in HNSCC tumourigenesis.

ErbB2 (HER2/neu) is overexpressed in about 25-30% of breast malignancies, and up-regulation of ErbB2 in breast cancer patients is associated with poor prognosis. It is known that the carboxyl terminus of heat shock cognate 70 interacting protein (CHIP) efficiently down-regulates ErbB2 in vitro. Human tumourous imaginal disc 1 (Tid1, DnaJa3), a co-chaperone of heat shock protein 70 (Hsp70), also suppresses ErbB2 expression in breast cancer cell lines. However, the intracellular interactions among Tid1, CHIP, and ErbB2 remain elusive, and the utilization of Tid1 and CHIP as breast cancer biomarkers has never been proposed. Herein, we analysed the expression and correlations among Tid1, CHIP, and ErbB2 in a total of 183 breast cancer histology sections, including 30 fresh tissue specimens, using immunohistochemistry (IHC) and immunoblotting assay. A computerized image analysis system was used for IHC scoring and determining relative immunoblot intensity. The immunohistochemical expression of Tid1 and CHIP were positively correlated with each other but were both inversely correlated to that of ErbB2. Odds ratio analyses showed that lower expression of Tid1 has a relatively higher risk of unfavourable tumour grade, later pathological stage, larger tumour size, and microscopic features of a more malignant histology including lymphovascular invasion, stromal inflammatory response, and tumour necrosis. Expression of CHIP displayed similar characteristics. Furthermore, expression of Tid1 and/or CHIP increases patients' 10-year overall and disease-free survival rate. Empirically, we also demonstrated that Tid1, CHIP, and ErbB2 interacted with each other through immunofluorescence or co-immunoprecipitation analyses. Functionally, Tid1 and CHIP acted synergistically to degrade ErbB2 in vitro. Conversely, Tid1 cannot compensate for the loss of proteolytic function noted in CHIP mutations for degradation of ErbB2. Overall, our data suggest that Tid1 and CHIP play pivotal roles in affecting the levels of ErbB2 protein, and that both are significant prognostic indicators of breast cancer patient survival.

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Mesenchymal stem cells (MSCs) hold promise for cell therapy, and implantation of MSCs engineered with a baculovirus transiently expressing the growth factor can augment the bone repair. To prolong the baculovirus-mediated transgene expression, we developed hybrid baculovirus vectors exploiting the FLP/Frt-mediated recombination for circular episome formation. Transduction of human MSCs with the hybrid baculovirus vectors harboring the osteoinductive bmp2 gene substantially extended the BMP2 expression and improved the cellular osteogenic differentiation. To confirm the potential in the clinical setting, the present study evaluated the biosafety profile of human MSCs engineered by the hybrid vectors. We unraveled that transduction of MSCs with the hybrid baculovirus vectors slightly impeded the cell proliferation after transduction, probably due to the perturbation of cellular gene expression and induction of innate responses. Nonetheless, the hybrid baculovirus vectors did not compromise the cell viability and cellular differentiation. No transgene integration into the host chromosome and disruption of the karyotype of the MSCs were observed. Additionally, no upregulation of proto-oncogenes or downregulation of tumor suppressor genes occurred in the MSCs transduced with the hybrid baculovirus vectors. Neither did the transduced MSCs induce tumor formation in nude mice. This study not only supported the safety of MSCs for cell therapy but also implicated the potential of the human MSCs engineered by the hybrid baculovirus vectors for their applications in clinical scenarios necessitating sustained transgene expression.

The progression and metastasis of solid tumors, including head and neck squamous cell carcinoma (HNSCC), have been related to the behavior of a small subpopulation of cancer stem cells. Here, we have established a highly malignant HNSCC cell line, SASVO3, from primary tumors using three sequential rounds of xenotransplantation. SASVO3 possesses enhanced tumorigenic ability both in vitro and in vivo. Moreover, SASVO3 exhibits properties of cancer stem cells, including that increased the abilities of sphere-forming, the number of side population cells, the potential of transplanted tumor growth and elevated expression of the stem cell marker Bmi1. Injection of SASVO3 into the tail vein of nude mice resulted in lung metastases. These results are consistent with the postulate that the malignant and/or metastasis potential of HNSCC cells may reside in a stem-like subpopulation.

Novel heteroatom-incorporated antofine and cryptopleurine analogs were designed, synthesized, and tested against a panel of five cancer cell lines. Two new S-13-oxo analogs (11 and 16) exhibited potent cell growth inhibition in vitro (GI50: 9 nM and 20 nM). Interestingly, both compounds displayed improved selectivity among different cancer cell lines, in contrast to the natural products antofine and cryptopleurine. MOAa studies suggested that R-antofine promotes dysregulation of DNA replication during early S phase, while no similar effects were observed for 11 and 15 on corresponding replication initiation complexes. Compound 11 also showed greatly reduced cytotoxicity against normal cells and moderate antitumor activity against HT-29 human colorectal adenocarcinoma xenograft in mice without overt toxicity.