Expression of proliferation-associated nuclear autoantigens, p330d/CENP-F and PCNA, in differentiation and in drug-induced growth inhibition using two-parameter flow cytometry

Dr Eng M. Tan: a tribute to an enduring legacy in autoimmunity

At the age of ninety years, Dr Eng Meng Tan has had a remarkable impact on the accumulated knowledge of autoimmune diseases, including seminal findings in systemic lupus erythematosus (SLE) and a wide range of other autoimmune diseases. Dating to the first description of the Sm (Smith) autoantibody in SLE, his focus has been the use of autoantibodies as probes to identify and elucidate novel cellular molecules and then translating these discoveries into biomarkers and immunoassays for a wide range of these diseases and, later, cancer. He led efforts to standardize autoantibody nomenclature and testing protocols. Through his mentorship a great number of trainees and collaborators have had remarkably successful careers, and by that virtue he has garnered a remarkable continuing legacy.

PIK3R3 induces epithelial-to-mesenchymal transition and promotes metastasis in colorectal cancer

Class IA PI3K plays an essential role in the invasion and metastasis of cancer. However, the mechanisms and specific functions of PI3K isoforms in tumor invasion and metastasis are not fully understood. We evaluated the role of PIK3R3, a PI3K regulatory subunit encoded by the PIK3R3 gene, in colorectal cancer invasion and metastasis. Clinical specimens and cell lines data show that the expression level of PIK3R3 is associated with colorectal cancer metastasis. Overexpression of PIK3R3 increases tumor migration and invasion in vitro and promotes metastasis of colorectal cancers in vivo. Furthermore, we investigated that the overexpression of PIK3R3 depends on SNAI2, inducing significant epithelial-to-mesenchymal transition (EMT). Downregulation of PIK3R3 reverses this process, which possibly contributes to the enhanced invasive and metastasizing abilities of colorectal cancer cells. In this study, we found that PIK3R3 plays an important role in colorectal cancer metastasis and might be a potential and specific target for therapies against metastatic colorectal cancer.

Correlation between centromere protein-F autoantibodies and cancer analyzed by enzyme-linked immunosorbent assay

Background

Centromere protein-F (CENP-F) is a large nuclear protein of 367 kDa, which is involved in multiple mitosis-related events such as proper assembly of the kinetochores, stabilization of heterochromatin, chromosome alignment and mitotic checkpoint signaling. Several studies have shown a correlation between CENP-F and cancer, e.g. the expression of CENP-F has been described to be upregulated in cancer cells. Furthermore, several studies have described a significant correlation between the expression of autoantibodies to CENP-F and cancer.

Methods

Autoantibodies to CENP-F were detected in a small number of samples during routine indirect immunofluorescence (IIF) analysis for anti-nuclear antibodies (ANA) using HEp-2 cells as substrate. Using overlapping synthetic peptides covering a predicted structural maintenance of chromosomes (SMC) domain, we developed an enzyme-linked immunosorbent assay (ELISA) for detection of CENP-F antibodies.

Results

Analyzing the reactivity of the sera positive in IIF for CENP-F antibodies to overlapping CENP-F peptides, we showed that autoantibodies to several peptides correlate with the presence of antibodies to CENP-F and a diagnosis of cancer, as increased CENP-F antibody expression specific for malignant cancer patients to five peptides was found (A9, A12, A14, A16, A27). These antibodies to CENP-F in clinical samples submitted for ANA analysis were found to have a positive predictive value for cancer of 50%. Furthermore, the expression of cancer-correlated CENP-F antibodies seemed to increase as a function of time from diagnosis.

Conclusion

These results conform to previous findings that approximately 50% of those patients clinically tested for ANA analyses who express CENP-F antibodies are diagnosed with cancer, confirming that these antibodies may function as circulating tumor markers. Thus, a peptide-based CENP-F ELISA focused on the SMC domain may aid in identifying individuals with a potential cancer.

Nicotinic and PDGF-receptor function are essential for nicotine-stimulated mitogenesis in human vascular smooth muscle cells

Cigarette smoking is implicated in the formation of occlusive vascular diseases. Nicotine's role in this process is incompletely understood. Nicotine's effect on human aortic vascular smooth muscle cells (HaVSMC) and the role of the nicotinic receptor (nAChR), platelet-derived growth factor (PDGF), and the PDGF-receptor (PDGF-R) in this response were studied. Nicotine's mitogenic effect was characterized by three methods: thymidine incorporation, a viability/proliferation assay based on metabolic conversion of tetrazolium salt to formazan dye and cell counting. Nicotine administration (10(-6) M) stimulated cell cycle entry marked by increased DNA synthesis, PCNA and cyclin D1 production, and increased cell division. Nicotinic receptor blockade with d-tubocurarine, a nicotinic AchR blocker, decreased nicotine-induced DNA synthesis, and cell division (0.33 +/- 0.04, 0.77 +/- 0.31-fold decrease, respectively). Nicotine increased cellular PDGF-BB transcript levels and protein release (ELISA: 1.6 +/- 0.5-fold increase) but not PDGF-AA or PDGF-AB release. Nicotine increased PDGFbeta-receptor protein content. PDGF inactivation with anti-PDGF antibody abolished nicotine-induced DNA synthesis (1.9 +/- 0.08-fold decrease). PDGF-R blockade with the PDGF-R antagonist tyrphostin AG 1295 decreased nicotine-induced DNA synthesis and cell division (0.25 +/- 0.01, 0.44 +/- 0.2-fold decrease, respectively). PDGF-R blockade reversed nicotine-stimulated increases in PDGF release, PDGF-BB transcripts, and PDGF-receptor levels (0.68 +/- 0.34; 0.46 +/- 0.01; 0.28 +/- 0.01-fold decrease, respectively). In conclusion, nicotine-mediated activation of nAChRs increases PDGF-BB transcription and protein production as well as PDGF beta-receptor levels. PDGF-BB/PDGF-R interaction is vital in nicotine's mitogenic actions on human aortic smooth muscle cells.

Alterations in protein expression in HL-60 cells during etoposide-induced apoptosis modulated by the caspase inhibitor ZVAD.fmk

DNA topoisomerase inhibitors induce a specific signaling cascade that promotes an active apoptotic caspase-dependent cell death process. However, little is known about the initial signals elicited by these agents. In the present study, we compared apoptosis in HL-60 cells treated either with the chemotherapeutic drug etoposide (VP16) alone or combined with the broad caspase inhibitor ZVAD.fmk. Apoptosis was assessed by changes in cell morphology and agarose gel electrophoresis of extracted cell DNA. We found that ZVAD.fmk prevents VP16-induced DNA fragmentation and the appearance of an increased number of apoptotic cells in the culture. We also compared the effects of etoposide alone or together with the pan-caspase inhibitor ZVAD.fmk on proliferating cell nuclear antigen, Bcl-2, and actin expression in human promyelocytic leukemia HL-60 cells. In addition, we screened for proteins that were initially upregulated in a caspase-dependent manner. Indeed, some proteins were induced in the cytoplasm and subsequently accumulated in the nuclei after etoposide treatment. This process was slightly inhibited by the caspase inhibitor ZVAD.fmk. We suggest that these proteins are associated with the induction of specific signaling cascades that characterize the apoptotic cell death process.

retinoic acid, bromodeoxyuridine, and the Delta 205 mutant polyoma virus middle T antigen regulate expression levels of a common ensemble of proteins associated with early stages of inducing HL-60 leukemic cell differentiation

Retinoic acid (RA), bromodeoxyuridine (BrdU), and the Delta 205 mutant polyoma middle T antigen affect the expression of a common ensemble of proteins in HL-60 human myeloblastic leukemia cells. Each of these agents is known to be able to prime HL-60 cells and accelerate subsequently induced myeloid or monocytic differentiation and G0 cell cycle arrest, suggesting that they have equal or identical cellular targets relevant to the early stages of inducing cell differentiation and G0 arrest. As a test of this possibility, a survey of protein expression changes induced by RA, BrdU, or Delta 205 transfection was performed. Retinoic acid induced numerous changes within h. Bromodeoxyuridine caused larger numbers of changes, whereas Delta 205 caused a more limited number. Among the hundreds of affected proteins detected, there were comparable numbers of up- or downregulated proteins. A small number changed between undetectable and detectable expression. The affected proteins were not restricted to a single functional class and included transcription factors, receptors, signaling molecules, cytoskeletal molecules, and effectors of various cellular processes such as deoxyribonucleic acid replication, transcription, and translation. The intersect of the sets of proteins affected by RA, BrdU, and Delta 205 was identified to determine if these agents regulated a common subset of proteins. This ensemble contained the commonly upregulated proteins AF6, ABP-280, ENC-1, ESE 1, MAP2B, NTF2, casein kinase, IRF1, SRPK2, Rb2, RhoGDI, P47phox, CD45, PKR, and SIIIp15. The commonly downregulated proteins were SHC, katanin, flotillin-2/ESA, EB 1, p43/EMAPIIprecursor, Jab1, FNK. The composition of the ensemble suggested three apparent themes for cellular processes that were affected early. The themes reflected the ultimate fate of the treated precursor cells as a mature myeloid cell, namely a cell whose hallmarks are (1) motility to migrate to a target and phagocytize it, (2) inducible oxidative metabolism to reduce the target with superoxide from a respiratory burst, and (3) biosynthetic slow down consistent with conversion from cell proliferation to quiescence. Interestingly, RA appears to induce aspects of an interferon-like response of potential significance as part of a biosynthetic slow down leading to cell cycle arrest. In conclusion, three biologically disparate ways to prime cells to differentiate were used to filter out a small ensemble of commonly regulated proteins that group as either microtubule associated, oxidative metabolism machinery, or effectors of cellular responses to interferon.

DNA damage in HeLa cells induced arrest at a discrete point in G2 phase as defined by CENP-F localization

G(2) is defined as the time in the cell cycle after DNA synthesis is complete but before the initiation of mitosis. However, as the molecular events of the cell cycle are described, G(2) can be seen to be a sequence of events rather than a static phase. For example, CENP-F increases in amount in early G(2), after DNA synthesis is complete, but localizes to the nuclear rim and then to the kinetochores before mitosis commences. After DNA damage cells may arrest in G(2) through TP53-dependent and independent mechanisms, raising the question of the precise position of the arrest within G(2). HeLa cells lack functional TP53; this allowed us to examine the TP53-independent mechanism of G(2) arrest. Here we showed that the DNA damage-induced G(2) arrest in HeLa cells is positioned in early G(2), before redistribution of CENP-F to the nuclear envelope and kinetochores, and before chromosome condensation commences.

CENP-F gene amplification and overexpression in head and neck squamous cell carcinomas

BACKGROUND

Antibodies against cancer-related genes have been detected in human cancers including head and neck cancers. High titers of c-Myc autoantibodies have been linked to gene amplification and tumor progression. Centromere protein-F (CENP-F) autoantibodies have been detected in patients with various cancers, suggesting similar gene alteration.

METHODS

CENP-F and c-MYC amplification was assessed in 72 head and neck squamous cell carcinoma (HNSCC) patients. Tumor and matched mucosa from 22 patients were analyzed for CENP-F mRNA levels by RT-PCR.

RESULTS

The larynx was the site most altered by amplification of either gene. CENP-F and c-MYC were amplified in 11% and 17% of the tumors, respectively. Coamplification was found in 7% of the tumors, most of which showed regional node involvement. CENP-F mRNA was overexpressed in 36% of tumors, and 23% of paired mucosa.

CONCLUSION

Our results provide the first evidence that CENP-F gene is amplified and overexpressed in HNSCC. No correlation was noted between CENP-F amplification and clinicopathologic parameters. However, CENP-F overexpression correlated with nodal metastasis.