Effects of IFI16 overexpression on the growth and doxorubicin sensitivity of head and neck squamous cell carcinoma–derived cell lines

Interferon-Gamma-Inducible Protein 16 Inhibits Hepatocellular Carcinoma via Interferon Regulatory Factor 3 on Chemosensitivity

BACKGROUND AND AIM

Previous reports have suggested IFI16 as a tumor suppressor in hepatocellular carcinoma (HC). Nonetheless, the biological significance of IFI16 and its mechanism concerning resistance to cisplatin (DDP) in HC requires further exploration.

METHODS

Samples of tumor and corresponding para-carcinoma tissues were acquired from patients with HC. Furthermore, DDP-resistant cell lines of HC, specifically HCC, Huh7 and Hepatoblastoma, HepG3, were generated by gradually increasing the concentration of DDP. Cell apoptosis and DNA damage were evaluated by utilizing flow cytometry assay and TUNEL staining. The interaction between IFI16 and interferon regulatory factor 3 (IRF3) proteins were analyzed using Co-Immunoprecipitation (Co-IP) assay. In vivo assays were conducted by establishing HC subcutaneous xenograft tumor models.

RESULTS

The study found a reduction in IFI16 expression in both HC tissues and DDP-resistant HC cell lines. The binding of IFI16 to IRF3 regulated DNA damage-associated markers in vitro. Overexpression of IFI16 heightened the susceptibility of DDP-induced apoptosis and DNA damage, which was counteracted by IRF3 knockdown, while strengthened by IRF3 overexpression. Moreover, overexpression of IFI16 diminished in vivo DDP-resistant HC tumorigenicity.

CONCLUSION

In summary, our findings suggest that IFI16 serves as a tumor suppressor in HC by promoting DNA damage via its interaction with IRF3, thereby reversing DDP resistance.

IFI16 Can Be Used as a Biomarker for Diagnosis of Renal Cell Carcinoma and Prediction of Patient Survival

The incidences of renal cell carcinoma (RCC) increase in number each year and account for about 2–3% of all malignant tumors. Many patients have metastasis by the time of diagnosis, and their prognosis is poor. Therefore, it is essential that new diagnostic and prognostic markers for kidney cancer are identified. In this study, we assessed the potential of IFI16 as a diagnostic and prognostic marker for RCC. We analyzed the TCGA and UALCAN databases and found IFI16 to be highly expressed in ccRCC. In addition, high IFI16 levels positively correlated with lymphatic metastasis, tumor stage, and histopathological grade. Kaplan-Meier curve analysis showed that IFI16 expression was related to the prognosis of patients, and high IFI16 expression indicated a worse overall survival (p = 5.1E–0.7). Receiver operating characteristic curve analysis showed that a combination of IFI16 expression and histopathological grade improved predictive accuracy (AUC = 0.697; 95%CI: 0.628–0.765, P < 0.001). Finally, the relative levels of IFI16 in ACHN and Caki-1 cells were higher than that of HK-2 cells by western blotting analysis and RT-PCR. Functional tests showed that knocking down IFI16 expression inhibited migration and invasion in vitro. Therefore, IFI16 is a potential biomarker for the diagnosis and prognosis of RCC patients.

Function and Regulation of Nuclear DNA Sensors During Viral Infection and Tumorigenesis

IFI16, hnRNPA2B1, and nuclear cGAS are nuclear-located DNA sensors that play important roles in initiating host antiviral immunity and modulating tumorigenesis. IFI16 triggers innate antiviral immunity, inflammasome, and suppresses tumorigenesis by recognizing double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), damaged nuclear DNA, or cooperatively interacting with multiple tumor suppressors such as p53 and BRCA1. hnRNPA2B1 initiates interferon (IFN)-α/β production and enhances STING-dependent cytosolic antiviral signaling by directly binding viral dsDNA from invaded viruses and facilitating N⁶ -methyladenosine (m⁶A) modification of cGAS, IFI16, and STING mRNAs. Nuclear cGAS is recruited to double-stranded breaks (DSBs), suppresses DNA repair, and promotes tumorigenesis. This review briefly describes the nuclear functions of IFI16, hnRNPA2B1, and cGAS, and summarizes the transcriptional, post-transcriptional, and post-translational regulation of these nuclear DNA sensors.

Interferon-inducible protein 16 may be a biomarker and prognostic factor in renal cell carcinoma by bioinformatics analysis

BACKGROUND

Renal cell carcinoma (RCC) accounts for 2% to 3% of all human malignancies and is the 9th most common malignancy in Western countries. Due to the development of surgical procedures and the use of novel drugs, survival has been significantly prolonged. However, current challenges include how to diagnose RCC earlier and how to overcome drug resistance. Methods: We explored the relationship between the transcription level of IFI16 and clinical data in RCC through various online databases, including ONCOMINE, GEPIA, HPA, Timer and COEXPEDIA.

RESULTS

In comparison with corresponding normal tissues, IFI16 mRNA expression levels were higher in kidney renal clear cell carcinoma (KIRC) and kidney renal papillary cell carcinoma (KIRP) tissues. In KIRC, the higher expression of IFI16 was associated with lower overall survival (P = .037). In KIRP, the higher expression IFI16 was associated with lower disease-free survival and overall survival (P = .037 and P = .011). In contrast, the IFI16 expression was negatively correlated with tumor purity in kidney chromophobe, KIRC and KIRP (all P < .05). In KIRC and KIRP, the expression of IFI16 was positively correlated with tumor-infiltrating immune cells (TIICs) (all P < .05), except macrophages in KIRP. In KIRC, the main TIICs were B cells, CD4+T cells, neutrophils, and dendritic cells, while the main TIICs in the high amplification state were macrophage (all P < .0001). Functional enrichment analysis by gene ontology and Kyoto Encyclopedia of Genes and Genomes highlighted enrichment of neutrophil degranulation, phagocytosis and vesicle-mediated transport regulation, and pathways including tuberculosis, toxoplasmosis, phagosome, leishmaniasis, and Fc gamma R-mediated.

CONCLUSIONS

IFI16 is overexpressed in RCC and may be an important oncogene in the progression of kidney. In addition, IFI16 may a marker for RCC diagnosis and prognosis, which may be related to immune infiltration.

PYHIN Proteins and HPV: Role in the Pathogenesis of Head and Neck Squamous Cell Carcinoma

In the last decades, the human papillomavirus (HPV) emerged as an etiological cause of head and neck squamous cell carcinoma (HNSCC), especially in the oropharynx. The role of two intracellular DNA sensors, which belong to the PYHIN family (interferon-inducible protein 16 (IFI16) and absent in melanoma 2 protein (AIM2)), has been analyzed in relation to HPV infection and head and neck carcinogenesis. In particular, IFI16 and AIM2 expression depends on HPV infection in HNSCC. They represent viral restriction factors and are key components of the intrinsic immunity activated against different viruses, including HPV. This review analyzed and summarized the recent findings about the role of PYHIN proteins in HPV⁺ and HPV⁻ HNSCC.

IFI16 restoration in hepatocellular carcinoma induces tumour inhibition via activation of p53 signals and inflammasome

OBJECTIVE

Interferon-inducible 16 (IFI16) is known to involve in p53-dependent tumour suppression and also the formation of inflammasome, which function, however, remains controversy during carcinogenesis as a pattern recognition receptor for tumour death-derived free DNA. In this study, we investigated the anti-tumour role of IFI16 in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Hepatocellular carcinoma tissues (n = 20) and corresponding non-neoplastic tissues (n = 20) were collected to determine the expression of IFI16. After the transfection of pcDNA3.1-IFI16 into Huh7 and SMMC7721 cells in vitro, the influence of IFI16 overexpression on cell vitality, colony formation, apoptosis and migration were analysed. The role effect of IFI16 in vivo was further investigated.

RESULTS

The expression of IFI16 was significantly decreased in tumour tissues and cell lines. Overexpression of IFI16 induced decrease of cell vitality, colony formation and increased apoptosis with impaired ability of migration. Mechanistically, IFI16 could activate p53 at Ser15 to up-regulate the p21^WAF1/CIP1 level to inhibit tumour growth and migration, which was restored by the p53 inhibitor Pifithrin-α (20 μmol/L). Moreover, IFI16-induced tumour cell death promoted the recruitment of inflammasome complex to enhance tumour inhibition, but the caspase-1 inhibitor Ac-YVAD-CMK (50 μmol/L) could suppress this process in HCC. The results in vivo indicated that restored expression of IFI16 in tumour cells effectively promote tumour regression, which could be partly abrogated by the inhibition of activation of p53 signals or induced inflammasome.

CONCLUSION

IFI16 is a tumour suppressor in HCC via activation of p53 signals and inflammasome.

IFI16, an amplifier of DNA-damage response: Role in cellular senescence and aging-associated inflammatory diseases

DNA-damage induces a DNA-damage response (DDR) in mammalian cells. The response, depending upon the cell-type and the extent of DNA-damage, ultimately results in cell death or cellular senescence. DDR-induced signaling in cells activates the ATM-p53 and ATM-IKKα/β-interferon (IFN)-β signaling pathways, thus leading to an induction of the p53 and IFN-inducible IFI16 gene. Further, upon DNA-damage, DNA accumulates in the cytoplasm, thereby inducing the IFI16 protein and STING-dependent IFN-β production and activation of the IFI16 inflammasome, resulting in the production of proinflammatory cytokines (e.g., IL-1β and IL-18). Increased expression of IFI16 protein in a variety of cell-types promotes cellular senescence. However, reduced expression of IFI16 in cells promotes cell proliferation. Because expression of the IFI16 gene is induced by activation of DNA-damage response in cells and increased levels of IFI16 protein in cells potentiate the p53-mediated transcriptional activation of genes and p53 and pRb-mediated cell cycle arrest, we discuss how an improved understanding of the role of IFI16 protein in cellular senescence and associated inflammatory secretory phenotype is likely to identify the molecular mechanisms that contribute to the development of aging-associated human inflammatory diseases and a failure to cancer therapy.

Possibility of the use of public microarray database for identifying significant genes associated with oral squamous cell carcinoma

There are lots of studies attempting to identify the expression changes in oral squamous cell carcinoma. Most studies include insufficient samples to apply statistical methods for detecting significant gene sets. This study combined two small microarray datasets from a public database and identified significant genes associated with the progress of oral squamous cell carcinoma. There were different expression scales between the two datasets, even though these datasets were generated under the same platforms - Affymetrix U133A gene chips. We discretized gene expressions of the two datasets by adjusting the differences between the datasets for detecting the more reliable information. From the combination of the two datasets, we detected 51 significant genes that were upregulated in oral squamous cell carcinoma. Most of them were published in previous studies as cancer-related genes. From these selected genes, significant genetic pathways associated with expression changes were identified. By combining several datasets from the public database, sufficient samples can be obtained for detecting reliable information. Most of the selected genes were known as cancer-related genes, including oral squamous cell carcinoma. Several unknown genes can be biologically evaluated in further studies.

Redistribution of the nuclear protein IFI16 into the cytoplasm of ultraviolet B-exposed keratinocytes as a mechanism of autoantigen processing

BACKGROUND

The skin has long been recognized as a prominent target tissue in systemic lupus erythematosus (SLE) which plays a crucial role in the initiation and perpetuation of the autoimmune reaction cascade as a consequence of ultraviolet (UV)-induced keratinocyte apoptosis. Antibodies against IFI16 (interferon-inducible protein 16) have been detected in the sera of patients with SLE.

OBJECTIVES

To verify whether the induction of autoimmunity against IFI16 involves redistribution of this nuclear protein in keratinocytes during UVB-induced cell death.

METHODS

An in vitro epidermal model was developed to investigate the fate of the IFI16 protein in keratinocytes after irradiation with UVB; both keratinocyte monolayers and human skin explants were used. IFI16 expression and localization were also analysed in diseased skin sections of patients with SLE.

RESULTS

We demonstrated that IFI16, normally restricted to the nucleus, can be induced to appear in the cytoplasm under conditions of UVB-induced cell injury. This nucleus to cytoplasm translocation was also observed in skin explants exposed to UVB and in the diseased skin sections from patients with SLE. In addition, IFI16 was found in the supernatants of UVB-exposed keratinocytes.

CONCLUSIONS

The finding that IFI16 is present in the cytoplasm of diseased skin cells from patients with SLE and the demonstration of IFI16 in the supernatants of UVB-exposed keratinocytes, suggest that UVB irradiation or other stimuli may favour an abnormal IFI16 presentation to the afferent limb of the immune system and potentially an autoimmune response against the protein itself.

Analysis of expression profiles of MAGE-A antigens in oral squamous cell carcinoma cell lines

BACKGROUND

The immunological response to solid tumours is insufficient. Therefore, tumour specific antigens have been explored to facilitate the activation of the immune system. The cancer/testis antigen class of MAGE-A antigens is a possible target for vaccination. Their differential expression profiles also modulate the course of the cancer disease and its response to antineoplastic drugs.

METHODS

The expression profiles of MAGE-A2, -A3, -A4, -A6 and -A10 in five own oral squamous cell carcinoma cell lines were characterised by rt-PCR, qrt-PCR and immunocytochemistry with a global MAGE-A antibody (57B) and compared with those of an adult keratinocyte cell line (NHEK).

RESULTS

All tumour cell lines expressed MAGE-A antigens. The antigens were expressed in groups with different preferences. The predominant antigens expressed were MAGE-A2, -A3 and -A6. MAGE-A10 was not expressed in the cell lines tested. The MAGE-A gene products detected in the adult keratinocyte cell line NHEK were used as a reference.

CONCLUSION

MAGE-A antigens are expressed in oral squamous cell carcinomas. The expression profiles measured facilitate distinct examinations in forthcoming studies on responses to antineoplastic drugs or radiation therapy. MAGE-A antigens are still an interesting aim for immunotherapy.

p204, a p200 family protein, as a multifunctional regulator of cell proliferation and differentiation

The interferon-inducible p200 family comprises a group of homologous mouse and human proteins. Most of these have an N-terminal DAPIN domain and one or two partially conserved, 200 amino acid long C-terminal domains (designated as 200X domain). These proteins play important roles in the regulation of cell proliferation, tissue differentiation, apoptosis and senescence. p200 family proteins are involved also in autoimmunity and the control of tumor growth. These proteins function by binding to various target proteins (e.g. transcription factors, signaling proteins, oncoproteins and tumor suppressor proteins) and modulating target activity. This review concentrates on p204, a murine member of the family and its roles in regulating cell proliferation, cell and tissue differentiation (e.g. of skeletal muscle myotubes, beating cardiac myocytes, osteoblasts, chondrocytes and macrophages) and signaling by Ras proteins. The expression of p204 in various tissues as promoted by tissue-specific transcription factors, its distribution among subcellular compartments, and the controls of these features are also discussed.

The side population of ovarian cancer cells is a primary target of IFN-alpha antitumor effects

The side population (SP), recently identified in several normal tissues and in a variety of tumors based on its ability to extrude some fluorescent dyes, may comprise cells endowed with stem cell features. In this study, we investigated the presence of SP in epithelial ovarian cancer and found it in 9 of 27 primary tumor samples analyzed, as well as in 4 of 6 cultures from xenotransplants. SP cells from one xenograft bearing a large SP fraction were characterized in detail. SP cells had higher proliferation rates, were much less apoptotic compared with non-SP cells, and generated tumors more rapidly than non-SP cells. We also investigated the effects of IFN-alpha, a cytokine that has widely been used to treat solid tumors, on epithelial ovarian cancer cells and observed that IFN-alpha exerted marked antiproliferative and proapoptotic effects on primary cultures containing high numbers of SP cells. In vitro, IFN-alpha treatment invariably caused a dramatic reduction in SP size in tumor cell lines of different origins; moreover, IFN-alpha treatment of purified SP cells was associated with a distinctive change in their transcriptional profile. Gene therapy with human IFN-alpha resulted in regression of established tumors bearing a large SP fraction, which was not observed when tumors bearing low SP levels were treated. These findings could have relevant clinical implications because they imply that tumors bearing large SP numbers, albeit rare, could be sensitive to IFN-alpha treatment.