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Biomedical subjects

Frank McCormick

Publications and source records attributed to Frank McCormick.

At least 37 records · Page 2Linked to original sources
PubMed2005

Heat shock phenocopies E1B-55K late functions and selectively sensitizes refractory tumor cells to ONYX-015 oncolytic viral therapy.

ONYX-015 is an E1B-55K-deleted adenovirus that has promising clinical activity as a cancer therapy. However, many tumor cells fail to support ONYX-015 oncolytic replication. E1B-55K functions include p53 degradation, RNA export, and host protein shutoff. Here, we show that resistant tumor cell lines fail to provide the RNA export functions of E1B-55K necessary for ONYX-015 replication; viral 100K mRNA export is necessary for host protein shutoff. However, heat shock rescues late viral RNA export and renders refractory tumor cells permissive to ONYX-015. These data indicate that heat shock and late adenoviral RNAs may converge upon a common mechanism for their export. Moreover, these data suggest that the concomitant induction of a heat shock response could significantly improve ONYX-015 cancer therapy.

Adenoviridae↗
PubMed2005

A conditional feedback loop regulates Ras activity through EphA2.

The EphA2 receptor tyrosine kinase is frequently overexpressed in many cancers, including 40% of breast cancers. Here, we show that EphA2 is a direct transcriptional target of the Ras-Raf-MAPK pathway and that ligand-stimulated EphA2 attenuates the growth factor-induced activation of Ras. Thus, a negative feedback loop is created that regulates Ras activity. Interestingly, the expression of EphA2 and ephrin-A1 is mutually exclusive in a panel of 28 breast cancer cell lines. We show that the MAPK pathway inhibits ephrin-A1 expression, and the ligand expression inhibits EphA2 levels contributing to the receptor-ligand reciprocal expression pattern in these cell lines. Our results suggest that an escape from the negative effects of this interaction may be important in the development of cancer.

Animals↗
PubMed2005

Killing time for cancer cells.

As the signalling pathways that control cellular proliferation and death are unravelled, a range of targets have emerged as candidates for molecular cancer therapy. For their survival, cancer cells depend on a few highly activated signalling pathways; inhibition of these pathways has a strong apoptotic effect and can lead to tumour regression. But drugs that exploit this weakness, such as imatinib, have not cured patients: withdrawal of the drug leads to disease recurrence, and sustained treatment leads to the emergence of drug-resistant clones. Can cancer be cured, or will it have to be controlled as a chronic disease?

Angiogenesis Inhibitors↗
PubMed2005

Effects of Onyx-015 among metastatic colorectal cancer patients that have failed prior treatment with 5-FU/leucovorin.

Despite recent improvements in the treatment of metastatic colorectal cancer, few patients are cured and the response rates to second-line treatments are poor. Onyx-015, an oncolytic virus, was administered to patients with metastatic colorectal cancer by hepatic artery infusion. No dose-limiting toxicities were observed in the phase I/II studies. Onyx-015 can kill tumor cells by mechanisms that are distinct from chemotherapeutic agents and may therefore have activity among patients who have failed first-line chemotherapy. The 24 patients included in this analysis had failed first-line therapy with 5-FU/leucovorin, 79% of the patients failed two or more regimens and 58% had failed treatment with Irinotecan. Despite the extensive prior therapy, the median survival of these patients was 10.7 months, 46% were alive at 1 year and two patients (8%) had partial responses. In all, 11 patients (46%) had stable disease at the completion of the four planned viral treatments (3 months). The median survival of this group of patients was 19 months, suggesting that stable disease may be an important predictor of benefit with oncolytic viruses. Eight of the 11 patients with stable disease at 3 months demonstrated a unique radiographic pattern of transient enlargement of tumor masses (10-48%) after the initial infusions of Onyx-015, followed by radiographic evidence of extensive tumor necrosis and regression. The initial enlargement and subsequent tumor necrosis resulted in a prolonged time to achieve objective tumor regression. In addition, the transient enlargement of the tumor masses may have resulted in premature removal of responding patients. Treatment of eight patients was stopped prior to completion of the planned four treatments due to presumed progression as defined by standard radiographic criteria (>25% increase in tumor size). Functional imaging, such as positron emission tomography (PET) scans, may help distinguish clinical responses from progressive disease following treatment with oncolytic viruses. Onyx-015 may benefit patients with refractory colorectal cancer and additional studies that include PET scans to assess clinical response are warranted.

Adenoviridae↗
PubMed2004

Downregulation of Skp2 and p27/Kip1 synergistically induces apoptosis in T98G glioblastoma cells.

S-phase kinase associated protein (Skp) 2 is an F-box protein required for substrate recognition of the SCF(Skp2) ubiquitin ligase complex. Skp2 is often overexpressed in transformed cells and in various types of tumors. Downregulation or inhibition of Skp2 inhibits growth of breast cancer cells and small-cell lung carcinoma cells. We downregulated Skp2 in T98G glioblastoma cells using small interfering RNA (siRNA). Downregulation induced p27 and caused growth arrest and apoptosis. Downregulation of both Skp2 and p27 increased apoptosis synergistically. Cyclin E levels and cyclin E-CDK2 kinase activity increased dramatically when both Skp2 and p27 were downregulated. Coincidently, Bcl-2 but not Bcl-xL expression decreased, and caspase-3 was activated. Inhibition of cyclin E-CDK2 kinase activity by forced expression of p21 reversed these effects. Moreover, stable expression of Bcl-2 also abrogated apoptosis induced by downregulation of Skp2 and p27. We suggest that Skp2 in tumor cells suppresses apoptosis through Bcl-2 expression, potentially through regulation of cyclin E-CDK2 activity.

Apoptosis↗
PubMed2004

Phosphorylation-independent stabilization of p27kip1 by the phosphoinositide 3-kinase pathway in glioblastoma cells.

The PTEN tumor suppressor gene is a frequent target of somatic mutation, particularly in glioblastoma multiform and prostate cancer. The expression of PTEN in PTEN-mutant glioblastoma cells leads to a cell cycle arrest in G(0)/G(1) that is mediated at least partially by increased p27(kip1) levels. Here we show that p27(kip1) is not regulated by transcriptional control but that p27(kip1) protein shows increased stability after inhibition of the phosphoinositide (PI) 3-kinase pathway. Because p27(kip1) protein stability is known to be regulated by phosphorylation, we have examined modifications in the phosphorylation pattern after PI 3-kinase inhibition. Biochemical evidence suggests that p27(kip1) is phosphorylated on several serine residues, including Ser-10 and Ser-178, but that phosphorylation is unaltered by PI 3-kinase activity. This is further confirmed by the inducible expression of p27(kip1) phosphorylation site mutants, suggesting that p27(kip1) is destabilized in a phosphorylation-independent manner by the PI 3-kinase pathway at the G(1)/S transition.

Base Sequence↗
PubMed2004

Activation of the hedgehog pathway in advanced prostate cancer.

BACKGROUND: The hedgehog pathway plays a critical role in the development of prostate. However, the role of the hedgehog pathway in prostate cancer is not clear. Prostate cancer is the second most prevalent cause of cancer death in American men. Therefore, identification of novel therapeutic targets for prostate cancer has significant clinical implications. RESULTS: Here we report that activation of the hedgehog pathway occurs frequently in advanced human prostate cancer. We find that high levels of hedgehog target genes, PTCH1 and hedgehog-interacting protein (HIP), are detected in over 70% of prostate tumors with Gleason scores 8-10, but in only 22% of tumors with Gleason scores 3-6. Furthermore, four available metastatic tumors all have high expression of PTCH1 and HIP. To identify the mechanism of the hedgehog signaling activation, we examine expression of Su(Fu) protein, a negative regulator of the hedgehog pathway. We find that Su(Fu) protein is undetectable in 11 of 27 PTCH1 positive tumors, two of them contain somatic loss-of-function mutations of Su(Fu). Furthermore, expression of sonic hedgehog protein is detected in majority of PTCH1 positive tumors (24 out of 27). High levels of hedgehog target genes are also detected in four prostate cancer cell lines (TSU, DU145, LN-Cap and PC3). We demonstrate that inhibition of hedgehog signaling by smoothened antagonist, cyclopamine, suppresses hedgehog signaling, down-regulates cell invasiveness and induces apoptosis. In addition, cancer cells expressing Gli1 under the CMV promoter are resistant to cyclopamine-mediated apoptosis. All these data suggest a significant role of the hedgehog pathway for cellular functions of prostate cancer cells. CONCLUSION: Our data indicate that activation of the hedgehog pathway, through loss of Su(Fu) or overexpression of sonic hedgehog, may involve tumor progression and metastases of prostate cancer. Thus, targeted inhibition of hedgehog signaling may have significant implications of prostate cancer therapeutics.

Gene Expression↗
PubMed2004

Cloning and characterization of the promoter of human Wnt inhibitory factor-1.

Wnt inhibitory factor-1 (WIF-1) is a secreted antagonist of Wnt signaling and functions by directly binding to Wnt ligands in the extracellular space. Here we report the identification of the 5' promoter region (approximately 1.5 kb) of the human WIF-1 gene. Functional analysis of this region shows that a whole fragment displays high basal promoter activity in different cell lines, while the truncated forms do not, indicating that integrity of the WIF-1 promoter region may be important for WIF-1 activity. Moreover, we found that the expression level of beta-catenin in cancer cell lines correlates with the WIF-1 promoter activity, suggesting that the WIF-1 promoter may be regulated by the Wnt/beta-catenin pathway and may function in a negative feedback manner. Our results also suggest that a methylated CpG island, which we observed recently in human lung cancer, lies within the functional WIF-1 promoter region and therefore bears the importance of the methylation-status of this CpG island as an important key in Wnt activation in human cancer.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Role for PP2A in ARF signaling to p53.

Activation of the ARF-p53 tumor suppressor pathway is one of the cell's major defense mechanisms against cancer induced by oncogenes. The ARF-p53 pathway is dysfunctional in a high proportion of human cancers. The regulation of the ARF-p53 signaling pathway has not yet been well characterized. In this study polyoma virus (Py) is used as a tool to better define the ARF-p53 signaling pathway. Py middle T-antigen (PyMT) induces ARF, which consequently up-regulates p53. We show that Py small T-antigen (PyST) blocks ARF-mediated activation of p53. This inhibition requires the small T-antigen PP2A-interacting domain. Our results reveal a previously unrecognized role of PP2A in the modulation of the ARF-p53 tumor suppressor pathway.

Amino Acid Sequence↗
PubMed2004

Expression of the secreted frizzled-related protein gene family is downregulated in human mesothelioma.

Secreted frizzled-related proteins (sFRPs) comprise a family of five secreted glycoproteins that antagonize Wnt signaling. Aberrant activation and upregulation of the Wnt pathway is a key feature of many cancers. Thus, role of sFRP as a negative regulator of Wnt signaling may have important implications in tumorigenesis, and its downregulation has been correlated with human cancers. Recently, we reported Wnt signaling and dishevelled (Dvl) overexpression in malignant pleural mesothelioma (MM). Here, we report significant transcriptional downregulation of the SFRP gene family in MM primary tissues and cell lines as well as several other cancer cell lines (breast, lung, glioma, and cervical) compared to normal cells. One or more SFRPs were downregulated in approximately 85% (18 of 21) of primary MM tumor specimens compared to normal pleural tissue. Eight of the nine cancer cell lines we examined showed silencing of the SFRP family. Methylation-specific PCR (MSP) analysis showed that SFRP1, SFRP4, and SFRP5 gene promoters are frequently methylated in MM primary tissue (>80%). Furthermore, transfection of the SFRP gene construct into MM cell lines lacking SFRP expression resulted in apoptosis and growth suppression. Our results suggest that methylation silencing of SFRPs may be one of the important mechanisms of aberrant Wnt signaling activation in MM.

Down-Regulation↗
PubMed2004

Inhibition of Wnt-2-mediated signaling induces programmed cell death in non-small-cell lung cancer cells.

In this report, we have demonstrated that Wnt-2 protein is overexpressed in freshly resected human non-small-cell lung cancer (NSCLC) tissues. We have also developed a monoclonal antibody against the N-terminus of human Wnt-2 protein. This monoclonal antibody induces apoptosis in human NSCLC cell lines that overexpress Wnt-2 protein. Incubation of this antibody with normal human airway cells lacking Wnt-2 expression does not induce apoptosis. Wnt-2 signaling blockade by the anti-Wnt-2 antibody is confirmed by downregulation of cytosolic beta-catenin and reduction in TCF-dependent transcriptional activity (TOPFLASH assay). In addition, Wnt-2-specific small interfering RNA (siRNA) treatment in the NSCLC cell line A549 also downregulated cytosolic beta-catenin and induced apoptosis. Moreover, downregulation of an inhibitor of apoptosis family protein, Survivin, was noticed both in the Wnt-2 antibody- and siRNA-treated NSCLC cells, suggesting that inhibition of Wnt-2-mediated signaling induces apoptosis through inactivating Survinin.

Antibodies, Monoclonal↗
PubMed2004

An anti-Wnt-2 monoclonal antibody induces apoptosis in malignant melanoma cells and inhibits tumor growth.

Activation of the Wnt/beta-catenin signaling pathway has been associated with human cancers. To test whether Wnt-2 signal is a survival factor in human melanoma cells and thus represents a potential therapeutic target, we investigated the effects of inhibition of Wnt-2 signaling in human melanoma cell lines. We have developed a novel monoclonal antibody against the NH(2) terminus of the human Wnt-2 ligand that induces apoptosis in human melanoma cells overexpressing Wnt-2. Whereas incubation of this antibody with normal cells lacking Wnt-2 expression does not induce apoptosis, Wnt-2 signaling blockade by the ligand-binding antibody is confirmed by down-regulation of Dishevelled and beta-catenin. Wnt-2 small interfering RNA treatment in these cells yielded similar apoptotic effects and downstream changes. Down-regulation of an inhibitor of apoptosis family protein, survivin, was observed in both the Wnt-2 antibody-treated and small interfering RNA-treated melanoma cell lines, suggesting that the antibody induces apoptosis by inactivating survivin. In an in vivo study, this monoclonal anti-Wnt-2 antibody suppresses tumor growth in a xenograft model. These findings suggest that the anti-Wnt-2 monoclonal antibody may be useful for the treatment of patients with malignant melanoma.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Wnt inhibitory factor-1 is silenced by promoter hypermethylation in human lung cancer.

Aberrant activation of the Wingless-type (Wnt) signaling pathway is associated with a variety of human cancers, and we recently reported the importance of aberrant Wnt signaling in lung cancer. On the other hand, inhibition of Wnt signaling suppresses growth in numerous cell types. Wnt inhibitory factor-1 (WIF-1) is a secreted antagonist that can bind Wnt in the extracellular space and inhibit Wnt signaling. Recently, down-regulation of WIF-1 has been reported in several human cancers. To discover the mechanism of WIF-1 silencing in lung cancer, we first identified the human WIF-1 promoter and subsequently examined the methylation status in the CpG islands. By using methylation-specific PCR and sequence analysis after bisulfite treatment, we demonstrate here frequent CpG island hypermethylation in the functional WIF-1 promoter region. This hypermethylation correlates with its transcriptional silencing in human lung cancer cell lines. Moreover, treatment with 5-aza-2'-deoxycytidine restores WIF-1 expression. We then studied WIF-1 expression in 18 freshly resected lung cancers, and we show a down-regulation in 15 of them (83%). This silencing also correlates with WIF-1 promoter methylation. Our results suggest that methylation silencing of WIF-1 is a common and likely important mechanism of aberrant activation of the Wnt signaling pathway in lung cancer pathogenesis, raising its therapeutic interest.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Inhibition of Wnt-1 signaling induces apoptosis in beta-catenin-deficient mesothelioma cells.

It is known that Wnt-1 signaling inhibits apoptosis by activating beta-catenin/tcf-mediated transcription. Here, we show that blocking Wnt-1 signaling in beta-catenin-deficient mesothelioma cell lines H28 and MS-1 induces apoptotic cell death. Both Wnt-1 small interfering RNA (siRNA) and Dishevelled siRNA induced significant apoptosis in these cell lines. A small molecule inhibitor of c-Jun NH(2)-terminal kinase inhibited the apoptotic cell killing induced by either Wnt-1 siRNA or Dishevelled siRNA in these cells. Our data suggest that beta-catenin-independent noncanonical pathway(s), i.e., Wnt/JNK pathway, may play a role in the apoptotic inhibition caused by Wnt-1 signaling.

Apoptosis↗
PubMed2004

Late viral RNA export, rather than p53 inactivation, determines ONYX-015 tumor selectivity.

ONYX-015 is an adenovirus that lacks the E1B-55K gene product for p53 degradation. Thus, ONYX-015 was conceived as an oncolytic virus that would selectively replicate in p53-defective tumor cells. Here we show that loss of E1B-55K leads to the induction, but not the activation, of p53 in ONYX-015-infected primary cells. We use a novel adenovirus mutant, ONYX-053, to demonstrate that loss of E1B-55K-mediated late viral RNA export, rather than p53 degradation, restricts ONYX-015 replication in primary cells. In contrast, we show that tumor cells that support ONYX-015 replication provide the RNA export function of E1B-55K. These data reveal that tumor cells have altered mechanisms for RNA export and resolve the controversial role of p53 in governing ONYX-015 oncolytic selectivity.

Adenoviridae↗
PubMed2004

Signaling specificity by Ras family GTPases is determined by the full spectrum of effectors they regulate.

Ras family GTPases (RFGs) regulate signaling pathways that control multiple biological processes. How signaling specificity among the closely related family members is achieved is poorly understood. We have taken a proteomics approach to signaling by RFGs, and we have analyzed interactions of a panel of RFGs with a comprehensive group of known and potential effectors. We have found remarkable differences in the ability of RFGs to regulate the various isoforms of known effector families. We have also identified several proteins as novel effectors of RFGs with differential binding specificities to the various RFGs. We propose that specificity among RFGs is achieved by the differential regulation of combinations of effector families as well as by the selective regulation of different isoforms within an effector family. An understanding of this new level of complexity in the signaling pathways regulated by RFGs is necessary to understand how they carry out their many cellular functions. It will also likely have critical implications in the treatment of human diseases such as cancer.

GTP Phosphohydrolases↗
PubMed2004

Future directions: oncolytic viruses.

Oncolytic viruses offer a promising new modality for cancer treatment. The strategy of this therapy is to develop viruses capable of selectively infecting and replicating in malignant tumor cells. Oncolytic viruses can spread and destroy malignant tumors without deleterious effects in normal tissues. These viruses are genetically engineered based on both the biology of replicating viruses and the major genetic defects in human cancer cells, so that they can replicate in cancer cells but not in normal cells. The key to the development of such viruses is the identification of viral genes, the deletion or modification of which enables tumor-specific cell destruction. Several clinical trials have demonstrated the safety of oncolytic viruses as cancer therapy and have also shown some encouraging results. Much evidence suggests that oncolytic viral therapy works in synergy with standard cancer therapies. In this review, we will focus on the oncolytic viruses that may be beneficial to patients with lung cancer in the near future.

Genetic Therapy↗