IRF-1-mediated CAS expression enhances interferon-gamma-induced apoptosis of HT-29 colon adenocarcinoma cells

CAS (CSE1L) signaling pathway in tumor progression and its potential as a biomarker and target for targeted therapy

CSE1L (chromosome segregation 1-like protein), also named as CAS (cellular apoptosis susceptibility protein), is highly expressed in most cancer types. CSE1L/CAS is a multiple functional protein that plays roles in apoptosis, cell survival, chromosome assembly, nucleocytoplasmic transport, microvesicle formation, and cancer metastasis; some of the functions are explicitly correlated. CSE1L is also a cancer serum biomarker. The phosphorylation of CAS is regulated by the extracellular signal-regulated kinase (ERK). The RAS/RAF/MAPK/ERK signaling pathways are the essential targets of most targeted cancer drugs, thus serum phosphorylated CSE1L may be a potential biomarker for monitoring drug resistance in targeted therapy. CSE1L can regulate Ras-induced ERK phosphorylation. CSE1L also regulates the expression and phosphorylation of CREB (cAMP response element binding protein) and MITF (microphthalmia-associated transcription factor) and is thus involved in the melanogenesis and progression of melanoma. CAS is an exosome/microvesicle membrane protein. Tumor cells consistently secrete microvesicles and tumor-derived microvesicles may be accumulated around tumors. Therefore, microvesicle membrane CSE1L may be a potential target for the development of high-efficacy antibody-drug conjugates (ADCs) for cancer therapy. This review will focus on CSE1L expression in cancers, its relationship to Ras/ERK and cAMP/PKA signaling pathways in melanoma development, its potential for the development of ADCs and tumor imaging reagents, and secretory phosphorylated CSE1L for monitoring the emergence of drug resistance in targeted cancer therapy.

IRF-1 inhibits NF-κB activity, suppresses TRAF2 and cIAP1 and induces breast cancer cell specific growth inhibition

Interferon Regulatory Factor (IRF)-1, originally identified as a transcription factor of the human interferon (IFN)-β gene, mediates tumor suppression and may inhibit oncogenesis. We have shown that IRF-1 in human breast cancer cells results in the down-regulation of survivin, tumor cell death, and the inhibition of tumor growth in vivo in xenogeneic mouse models. In this current report, we initiate studies comparing the effect of IRF-1 in human nonmalignant breast cell and breast cancer cell lines. While IRF-1 in breast cancer cells results in growth inhibition and cell death, profound growth inhibition and cell death are not observed in nonmalignant human breast cells. We show that TNF-α or IFN-γ induces IRF-1 in breast cancer cells and results in enhanced cell death. Abrogation of IRF-1 diminishes TNF-α and IFN-γ-induced apoptosis. We test the hypothesis that IRF-1 augments TNF-α-induced apoptosis in breast cancer cells. Potential signaling networks elicited by IRF-1 are investigated by evaluating the NF-κB pathway. TNF-α and/or IFN-γ results in decreased presence of NF-κB p65 in the nucleus of breast cancer cells. While TNF-α and/or IFN-γ can induce IRF-1 in nonmalignant breast cells, a marked change in NF-κB p65 is not observed. Moreover, the ectopic expression of IRF-1 in breast cancer cells results in caspase-3, -7, -8 cleavage, inhibits NF-κB activity, and suppresses the expression of molecules involved in the NF-κB pathway. These data show that IRF-1 in human breast cancer cells elicits multiple signaling networks including intrinsic and extrinsic cell death and down-regulates molecules involved in the NF-κB pathway.

Blocking of interferon regulatory factor 1 reduces tumor necrosis factor α-induced interleukin-18 bioactivity in rheumatoid arthritis synovial fibroblasts by induction of interleukin-18 binding protein a: role of the nuclear interferon regulatory factor 1-NF-κB-c-jun complex

OBJECTIVE

To examine the role of interferon regulatory factor 1 (IRF-1) in tumor necrosis factor α (TNFα)-induced interleukin-18 binding protein a (IL-18BPa) expression in rheumatoid arthritis synovial fibroblasts (RASFs).

METHODS

TNFα-induced IRF-1 expression was assessed by real-time quantitative polymerase chain reaction and Western blotting. The effect of TNFα on IRF-1 was assessed using nuclear and cytoplasmic extracts, Western blots, and immunofluorescence. Chemical inhibitors of NF-κB or MAP kinases were used to analyze the signaling pathways of TNFα-induced IRF-1 expression and IRF-1 nuclear translocation. Control and IRF-1 small interfering RNA (siRNA) were used to analyze the effect of IRF-1 down-regulation on TNFα-induced IL-18BP expression. IL-18BPa expression was assessed by enzyme-linked immunosorbent assay, and IL-18 was assessed at the transcription and bioactivity levels using KG-1 cells.

RESULTS

TNFα induced RASF IRF-1 expression at the messenger RNA and protein levels, with a maximal effect at 2 hours (P < 0.05; n ≥ 3). Furthermore, TNFα induced nuclear translocation of IRF-1, with maximal translocation at 2 hours (∼6 fold-induction) (P < 0.05; n = 4). Blocking of the NF-κB or JNK-2 pathways reduced TNFα-induced IRF-1 nuclear translocation by 35% and 50%, respectively (P < 0.05; n ≥ 4). Using siRNA to knock down IRF-1, we observed reduced IL-18BPa expression. Additionally, IL-18 bioactivity was higher when siRNA was used to knock down IRF-1 expression.

CONCLUSION

These results show that IRF-1 is a key regulator of IL-18BPa expression and IL-18 bioactivity in RASFs. Regulation of IRF-1 will be a new therapeutic target in RA.

Cellular apoptosis susceptibility (CSE1L/CAS) protein in cancer metastasis and chemotherapeutic drug-induced apoptosis

The cellular apoptosis susceptibility (CSE1L/CAS) protein is highly expressed in cancer, and its expression is positively correlated with high cancer stage, high cancer grade, and worse outcomes of patients. CSE1L (or CAS) regulates chemotherapeutic drug-induced cancer cell apoptosis and may play important roles in mediating the cytotoxicities of chemotherapeutic drugs against cancer cells in cancer chemotherapy. CSE1L was originally regarded as a proliferation-associated protein and was thought to regulate the proliferation of cancer cells in cancer progression. However, the results of experimental studies showed that enhanced CSE1L expression is unable to increase proliferation of cancer cells and CSE1L regulates invasion and metastasis but not proliferation of cancer cells. Recent studies revealed that CSE1L is a secretory protein, and there is a higher prevalence of secretory CSE1L in the sera of patients with metastatic cancer. Therefore, CSE1L may be a useful serological marker for screening, diagnosis and prognosis, assessment of therapeutic responses, and monitoring for recurrence of cancer. In this paper, we review the expression of CSE1L in cancer and discuss why CSE1L regulates the invasion and metastasis rather than the proliferation of cancer.

Pancreatic cancer escape variants that evade immunogene therapy through loss of sensitivity to IFNgamma-induced apoptosis

Combined injections into experimental tumor nodules of adenovirus encoding IL-12 and certain chemokines are capable to induce immune-mediated complete regressions. In this study, we found that the combination of two adenoviruses, one encoding IL-12 and other MIP3alpha (AdCMVIL-12+AdCMVMIP3alpha) was very successful in treating CT-26-derived colon carcinomas. However, in experimental tumors generated from the pancreatic carcinoma cell line Panc02 such combined treatment induces 50% of macroscopic complete regressions, although local relapses within 1 week are almost constant. We derived cell lines from such relapsing tumors and found that experimental malignancies derived from their inoculum were not amenable to treatment in any case with AdCMVIL-12+AdCMVMIP-3alpha. Importantly, relapsing cell lines were insensitive to in vitro induction of apoptosis by IFNgamma, in clear contrast with the original Panc02 cells. Comparative analyses by cDNA arrays of relapsing cell lines versus wild-type Panc02 were performed revealing an important number of genes (383) whose expression levels were modified more than two-fold. These changes grouped in certain gene ontology categories should harbor the mechanistic explanations of the acquired selective resistance to IFNgamma.

Suppression of growth by all-trans retinoic acid requires prolonged induction of interferon regulatory factor 1 in cervical squamous carcinoma (SiHa) cells

All-trans retinoic acid (ATRA) suppresses growth of cervical dysplasias in vivo, although the sensitivity to retinoids is frequently lost during cervical carcinogenesis. It has been suggested that prolonged treatment or use of higher doses of retinoids might offer favorable response rates. We found SiHa cervical squamous carcinoma cells that were virtually resistant to ATRA-induced growth-inhibitory effects at physiological doses (10(-7 to) 10(-6) M) to be more responsive at pharmacological doses (10(-5 to) 10(-4) M). The growth inhibition by high-dose (10(-4) M) ATRA was associated with a sustained activation of interferon regulatory factor 1 (IRF-1), while a low dose (10(-6) M) of ATRA activated IRF-1 only transiently. Antisense IRF-1 inhibited the high-dose (10(-4) M), ATRA-mediated growth arrest; forced expression of IRF-1 caused a significant reduction in cell growth. High-dose (10(-4) M) ATRA increased binding of NF-kappaB and STAT1 proteins to sequences that originated from the IRF-1 promoter region, while low-dose (10(-6) M) ATRA induced only NF-kappaB binding. A delayed tyrosine phosphorylation of the signal transducer and activator of transcription-1 (STAT1) was observed after high-dose (10(-4) M) but not low-dose (10(-6) M) ATRA treatment. In agreement with this, induction of IRF-1 mRNA by ATRA was only modest and transient in a STAT1 knockout cell line, suggesting the importance of STAT1 in sustained IRF-1 expression. Our data showed that ATRA is capable of inducing dose-dependent cellular changes, which might be appropriate to overcome resistance to retinoids that frequently develops during cervical carcinogenesis.

CAS/CSE 1 stimulates E-cadhrin-dependent cell polarity in HT-29 human colon epithelial cells

The establishment and maintenance of epithelial polarity are crucial for tissue organization and function in mammals. Epithelial cadherin (E-cadherin) is expressed in epithelial cell membrane and is important for cell-cell adhesion, intercellular junctions formation, as well as epithelial cell polarization. We report herein that CAS (CAS/CSE 1), the human cellular apoptosis susceptibility protein, interacts with E-cadherin and stimulates polarization of HT-29 human colon epithelial cells. CAS binds with E-cadherin but not with beta-catenin in the immunoprecipitation assays. Interaction of CAS with E-cadherin enhances the formation of E-cadherin/beta-catenin cell-cell adhesive complex. Electron microscopic study demonstrated that CAS overexpression in cells stimulates intercellular junction complex formation. The disorganization of cellular cytoskeleton by cytochalasin D, colchicine, or acrylamide treatment disrupts CAS-stimulated HT-29 cell polarization. CAS-mediated HT-29 cell polarity is also inhibited by antisense E-cadherin DNA expression. Our results indicate that CAS cooperates with E-cadherin and plays a role in the establishment of epithelial cell polarity.

The class II tumour suppressor gene H-REV107-1 is a target of interferon-regulatory factor-1 and is involved in IFNgamma-induced cell death in human ovarian carcinoma cells

H-rev107-1 is a growth inhibitory RAS target gene capable of suppressing anchorage independent growth in vitro and in vivo. Using a tumour tissue array with 241 matched tumour and normal tissue cDNA pools, we found down-regulation of H-REV107-1 in 7 out of 14 ovary-derived cDNAs. RT-PCR analysis and immunohistochemical investigation confirmed expression of H-REV107-1 in normal ovarian epithelial cells but down-regulation in high grade ovarian carcinomas. H-REV107-1 is also strongly expressed in immortalized rat and human ovarian epithelial cells in vitro, but suppressed in transformed cells by two different mechanisms. KRAS-transformed rat ovarian cells and PA1 teratocarcinoma cells, reversibly repress H-REV107-1 via MAP/ERK signaling. In contrast, treatment of A27/80 and OVCAR-3 epithelial ovarian cancer cells with IFNgamma stimulated H-REV107-1 expression. In NIH3T3 cells harbouring an estrogen-inducible IRF-1, H-rev107-1 is directly induced after activation of IRF-1, indicating that H-rev107-1 is a target of IRF-1. Stimulation of H-REV107-1 expression was also observed in ovarian epithelial cells suggesting that IRF-1 is involved in H-REV107-1 regulation in human ovarian epithelium. In the IFNgamma-sensitive cell line A27/80, H-REV107-1 suppresses colony formation. A27/80 and OVCAR-3 cells overexpressing H-REV107-1 protein underwent apoptosis. These results demonstrate down-regulation of the class II tumour suppressor H-REV107-1 in human ovarian carcinomas and suggest an involvement of H-REV107-1 in interferon-dependent cell death.