Vector targeting makes 5-fluorouracil chemotherapy less toxic and more effective in animal models of epithelial neoplasms

L-Plastin Promotes Gastric Cancer Growth and Metastasis in a Helicobacter pylori cagA-ERK-SP1-Dependent Manner

Actin cytoskeleton dynamic rearrangement is required for tumor cell metastasis and is a key characteristic of Helicobacter pylori (H. pylori)-infected host cells. Actin cytoskeleton modulation is coordinated by multiple actin-binding proteins (ABP). Through Kyoto encyclopedia of gene and genomes database, GEPIA website, and real-time PCR data, we found that H. pylori infection significantly induced L-plastin, a key ABP, in gastric cancer cells. We further explored the regulation and function of L-plastin in H. pylori-associated gastric cancer and found that, mechanistically, H. pylori infection induced gastric cancer cells to express L-plastin via cagA-activated ERK signaling pathway to mediate SP1 binding to L-plastin promoter. Moreover, this increased L-plastin promoted gastric cancer cell proliferation and migration in vitro and facilitated the growth and metastasis of gastric cancer in vivo. Finally, we detected the expression pattern of L-plastin in gastric cancer tissues, and found that L-plastin was increased in gastric cancer tissues and that this increase of L-plastin positively correlated with cagA + H. pylori infection status. Overall, our results elucidate a novel mechanism of L-plastin expression induced by H. pylori, and a new function of L-plastin-facilitated growth and metastasis of gastric cancer, and thereby implicating L-plastin as a potential therapeutic target against gastric cancer. IMPLICATIONS: Our results elucidate a novel mechanism of L-plastin expression induced by H. pylori in gastric cancer, and a new function of L-plastin-facilitated gastric cancer growth and metastasis, implicating L-plastin as a potential therapeutic target against gastric cancer.

The actin-bundling protein L-plastin-A double-edged sword: Beneficial for the immune response, maleficent in cancer

The dynamic organization of the actin cytoskeleton into bundles and networks is orchestrated by a large variety of actin-binding proteins. Among them, the actin-bundling protein L-plastin is normally expressed in hematopoietic cells, where it is involved in the immune response. However, L-plastin is also often ectopically expressed in malignant cancer cells of non-hematopoietic origin and is even considered as a marker for cancer progression. Post-translational modification modulates L-plastin activity. In particular, L-plastin Ser5 phosphorylation has been shown to be important for the immune response in leukocytes as well as for invasion and metastasis formation of carcinoma cells. This chapter discusses the physiological and pathological role of L-plastin with a special focus on the importance of L-plastin Ser5 phosphorylation for the protein functions. The potential use of Ser5 phosphorylated L-plastin as a biomarker and/or therapeutic target will be evoked.

A Biodegradable Stent with Surface Functionalization of Combined-Therapy Drugs for Colorectal Cancer

In-stent restenosis caused by tumor ingrowth is a major problem for patients undergoing stent placement because conventional stents often lack sustainable antitumor capabilities. The aim of this work is to develop a silk fibroin (SF)-based nanofibrous membrane that is loaded with combined-therapy drugs by using electrospinning technologies, which is further coated on a polydioxanone (PDO) stent and used for the treatment of colorectal cancer (CRC). In order to improve treatment effectiveness, a combination of therapeutic drugs, i.e., curcumin (CUR) and 5-fluorouracil (5-FU), is dissolved into SF solution and then eletrospun onto the surface of the PDO stent. The morphology, secondary structure, and in vitro drug release profiles of the membranes are characterized. The antitumor efficacy is assessed in vitro and in vivo using a human CRC cell line and normal cells, and tumor-bearing nude mice. In vitro and in vivo studies on the nanofibrous memembrane-coating demonstrate improved antitumor effects for the CUR/5-FU dual drug system which can be attributed to cell cycle arrest in the S phase in association with induced apoptosis in tumor cells by blocking signal transducer and activator of transcription3 (Stat3) and nuclear factor kappa beta (NF-kB) signaling pathways, suggesting potential in the treatment of CRC in the future.

The Calcium-Dependent Switch Helix of L-Plastin Regulates Actin Bundling

L-plastin is a calcium-regulated actin-bundling protein that is expressed in cells of hematopoietic origin and in most metastatic cancer cells. These cell types are mobile and require the constant remodeling of their actin cytoskeleton, where L-plastin bundles filamentous actin. The calcium-dependent regulation of the actin-bundling activity of L-plastin is not well understood. We have used NMR spectroscopy to determine the solution structure of the EF-hand calcium-sensor headpiece domain. Unexpectedly, this domain does not bind directly to the four CH-domains of L-plastin. A novel switch helix is present immediately after the calcium-binding region and it binds tightly to the EF-hand motifs in the presence of calcium. We demonstrate that this switch helix plays a major role during actin-bundling. Moreover a peptide that competitively inhibits the association between the EF-hand motifs and the switch helix was shown to deregulate the actin-bundling activity of L-plastin. Overall, these findings may help to develop new drugs that target the L-plastin headpiece and interfere in the metastatic activity of cancer cells.

Bugs and drugs: oncolytic virotherapy in combination with chemotherapy

Single agent therapies are rarely successful in treating cancer, particularly at metastatic or end stages, and survival rates with monotherapies alone are generally poor. The combination of multiple therapies to treat cancer has already driven significant improvements in the standard of care treatments for many types of cancers. The first combination treatments exploited for cancer therapy involved the use of several cytotoxic chemotherapy agents. Later, with the development of more targeted agents, the use of novel, less toxic drugs, in combination with the more classic cytotoxic drugs has proven advantageous for certain cancer types. Recently, the combination of oncolytic virotherapy with chemotherapy has shown that the use of these two therapies with very distinct anti-tumor mechanisms may also lead to synergistic interactions that ultimately result in increased therapeutic effects not achievable by either therapy alone. The mechanisms of synergy between oncolytic viruses (OVs) and chemotherapeutic agents are just starting to be elucidated. It is evident, however, that the success of these OV-drug combinations depends greatly on the particular OV, the drug(s) selected, and the cancer type targeted. This review summarizes the different OV-drug combinations investigated to date, including the use of second generation armed OVs, which have been studied with the specific purpose of generating synergistic interactions with particular chemotherapy agents. The known mechanisms of synergy between these OV-drug combinations are also summarized. The importance of further investigating these mechanisms of synergy will be critical in order to maximize the therapeutic efficacy of OV-drug combination therapies in the future.

TAA/ecdCD40L adenoviral prime-protein boost vaccine for cancer and infectious diseases

A vaccine platform has been created by attaching the target-associated antigen (TAA) for the vaccine to the extracellular domain (ecd) of the potent immunostimulatory signal CD40 ligand (CD40L). Attachment of the TAA to the CD40L promotes uptake of the TAA into dendritic cells (DCs), binding to Class I as well as Class II MHC leading to presentation of the TAA on the DCs, expansion of the TAA-specific B cell and CD8 effector T-cell lymphocytes, and induction of a memory response. In addition, the TAA/ecdCD40L vaccine can overcome anergy, induce regressions of pre-existing subcutaneous (SC) nodules of cancer cells, and induce high titers of neutralizing antibodies against viral antigens. This vaccine, which can be administered SC as a TAA/ecdCD40L fusion protein, or as expression vectors (viral or plasmid) or as a vector prime-protein boost strategy, is applicable to the development of vaccine for a wide range of cancers and infectious agents.

Transcriptional control of Flt3 ligand targeted by fluorouracil-induced Egr-1 promoter in hematopoietic damage

BACKGROUND

Ionizing radiation (IR) activate the early growth response-1 (Egr-1) promoter by production of radical oxygen intermediates (ROIs). Egr-EF, an expression vector pCIneo containing Egr-1 promoter cloned upstream of the cDNA for Flt3 ligand, was used to treat hematopoietic damage. 5-fluorouracil, a commonly used chemotherapeutic agent, cause tumor cell death by producing DNA damage and generating ROIs. We therefore hypothesized that clinically employed chemotherapeutic agents that increase ROIs could also be employed to activate Egr-EF in a chemoinducible gene therapy strategy. The goal of this study was to explore the effect of Flt3 Ligand gene transcription regulated by fluorouracil-induced Egr-1 promoter on hematopoietic recovery.

METHODS

Human Flt3 Ligand (FL) cDNA and enhanced green fluorescent protein (EGFP) cDNA were linked together with IRES and inserted into the expression vector pCI-neo under control of the Egr-1 promoter (Egr-EF). The vector was transfected into the HFCL human bone marrow stromal cell line, and these cells were exposed to 5-FU, a chemotherapeutic drug. Expression of FL by HFCL/EF cells after 5-FU treatment was determined with ELISA, western blot and RT-PCR assays. In addition, the effect of FL from HFCL/EF cell culture supernatants on growth of CD34+ cells from cord blood was also studied. HFCL/EF cells were injected into CB-17 combined immunodeficient (SCID) mice with B16 melanoma. 5-FU was given three days after injection of the HFCL/EF cells. In the recipient mice, white blood cell levels in peripheral blood and expression of EGFP and FL in human stromal cells were measured. Tumor volumes in tumor-bearing mice were also measured.

RESULTS

5-FU treatment increased EGFP levels and secreted FL levels in HFCL/EF cells. Supernatants from HFCL/EF cell cultures treated with 5-FU increased CD34+ cell growth significantly. HFCL/EF exhibited an increase in the number of white blood cells after chemotherapy.

CONCLUSION

The data presented here support the use of transcriptional control mediated by chemoinducible gene therapy to reduce hematopoietic injury associated with 5-FU.

Chemotherapy targeted to cancer tissue potentiates antigen-specific immune response induced by vaccine for in vivo antigen loading and activation of dendritic cells

Our laboratory has created an Ad-sig-TAA/ecdCD40L vaccine platform designed to activate dendritic cells (DCs). Two subcutaneous (s.c.) injections of the TAA/ecdCD40L protein following the s.c. injection of the Ad-sig-TAA/ecdCD40L vector (TAA/ecdCD40L VPP vaccine) further increases the levels of the tumor-associated antigen (TAA)-specific CD8 effector T cells induced by the vector. We tested the combined effect of chemotherapy-induced destruction of tumor cells and TAA/ecdCD40L VPP vaccine which further increases the levels of TAA available to the DCs at the time of vaccination. The chemotherapy was delivered selectively to the tumor cells using intratumoral (i.t.) injection of the AdCDIRESE1A vector followed by intraperitoneal (i.p.) 5-fluorocytosine (5FC). The 5-fluorouracil (5FU) produced in the vector infected the tumor cells, destroys them and releases the TAA for processing and presentation by the DCs. This mode of delivery spares the TAA CD8 effector T cells from the destructive effect of the 5FU when their proliferation is induced by the vaccine. Test mice treated with both the s.c. administered TAA/ecdCD40L VPP vaccine and the AdCDIRESE1A/5FC chemosensitization vector had the smallest tumor volumes and survived longer than mice treated with either of these agents alone (P < 0.001).

Systemic 5-fluorouracil treatment causes a syndrome of delayed myelin destruction in the central nervous system

BACKGROUND

Cancer treatment with a variety of chemotherapeutic agents often is associated with delayed adverse neurological consequences. Despite their clinical importance, almost nothing is known about the basis for such effects. It is not even known whether the occurrence of delayed adverse effects requires exposure to multiple chemotherapeutic agents, the presence of both chemotherapeutic agents and the body's own response to cancer, prolonged damage to the blood-brain barrier, inflammation or other such changes. Nor are there any animal models that could enable the study of this important problem.

RESULTS

We found that clinically relevant concentrations of 5-fluorouracil (5-FU; a widely used chemotherapeutic agent) were toxic for both central nervous system (CNS) progenitor cells and non-dividing oligodendrocytes in vitro and in vivo. Short-term systemic administration of 5-FU caused both acute CNS damage and a syndrome of progressively worsening delayed damage to myelinated tracts of the CNS associated with altered transcriptional regulation in oligodendrocytes and extensive myelin pathology. Functional analysis also provided the first demonstration of delayed effects of chemotherapy on the latency of impulse conduction in the auditory system, offering the possibility of non-invasive analysis of myelin damage associated with cancer treatment.

CONCLUSIONS

Our studies demonstrate that systemic treatment with a single chemotherapeutic agent, 5-FU, is sufficient to cause a syndrome of delayed CNS damage and provide the first animal model of delayed damage to white-matter tracts of individuals treated with systemic chemotherapy. Unlike that caused by local irradiation, the degeneration caused by 5-FU treatment did not correlate with either chronic inflammation or extensive vascular damage and appears to represent a new class of delayed degenerative damage in the CNS.

Suicide gene therapy with the yeast fusion gene cytosine deaminase/uracil phosphoribosyltransferase is not enough for pancreatic cancer

OBJECTIVES

Suicide gene therapy with FCY1 gene, encoding cytosine deaminase (CD), together with FUR1, encoding uracil phosphoribosyltransferase (UPRT), has been proposed for pancreatic cancer therapy in vivo. We ascertained whether gene therapy with FCY1-FUR1 is effective in killing pancreatic cancer cells after 5-fluorocytosine (5-FC) treatment.

METHODS

AsPC1, BxPC3, Capan1, MIA PaCa2, and Panc1 cell lines were transfected using 2 plasmid vectors expressing CD only (pRSV-CD) or the chimera CD-UPRT (pRSV-CD-UPRT). Control and pRSV-CD- or pRSV-CD-UPRT-transfected cell lines were treated with 0, 0.1, 0.5, 1, 5, and 10 mM of 5-FC for 1, 3, 6, 8, 10, and 13 days.

RESULTS

FCY1 alone did not confer sensitivity to 5-FC. The CD-UPRT-transfected BxPC3 and Panc1 were sensitive to very low 5-FC doses (0.1 mM). 5-Fluorocytosine-sensitive transfected cell lines rapidly converted 5-FC into 5-fluorouracil, whereas the 5-FC resistant cell lines had an impaired 5-FC conversion.

CONCLUSIONS

Suicide gene therapy with the FCY1 gene alone was ineffective in the treatment of pancreatic cancer in vitro. The pRSV-CD-UPRT construct conferred 5-FC sensitivity to some pancreatic cancer cell lines. Therefore, the application in vivo of suicide gene therapy with FCY1 alone or in combination with the FUR1 gene is probably destined to fail.

Biology and therapeutic potential of cannabinoid CB2 receptor inverse agonists

Evidence has emerged suggesting a role for the cannabinoid CB2 receptor in immune cell motility. This provides a rationale for a novel and generalized immunoregulatory role for cannabinoid CB2 receptor-specific compounds. In support of this possibility, we will review the biology of a class of cannabinoid CB2 receptor-specific inverse agonist, the triaryl bis-sulfones. We will show that one candidate, Sch.414319, is potent and selective for the cannabinoid CB2 receptor, based on profiling studies using biochemical assays for 45 enzymes and 80 G-protein coupled receptors and ion channels. We will describe initial mechanistic studies using this optimized triaryl bis-sulfone, showing that the compound exerts a broad effect on cellular protein phosphorylations in human monocytes. This profile includes the down regulation of a required phosphorylation of the monocyte-specific actin bundling protein L-plastin. We suggest that this observation may provide a mechanism for the observed activity of Sch.414319 in vivo. Our continued analysis of the in vivo efficacy of this compound in diverse disease models shows that Sch.414319 is a potent modulator of immune cell mobility in vivo, can modulate bone damage in antigen-induced mono-articular arthritis in the rat, and is uniquely potent at blocking experimental autoimmune encephalomyelitis in the rat.

Cytotoxic effect of a replication-incompetent adenoviral vector with cytosine deaminase gene driven by L-plastin promoter in hepatocellular carcinoma cells

Great expectations are set on gene therapy for the treatment of malignant hepatocellular carcinomas (HCC) in East Asia. Recombinant adenoviral vectors (AV) have been developed in which the L-plastin promoter (LP) regulates the expression of transgenes, in a tumor cell specific manner, resulting in an increase in the therapeutic index. The development of the AdLPCD vector, a replication-incompetent AV, containing a transcription unit of LP and E. coli cytosine deaminase (CD), was reported in our previous work. In the present study, the AdLPCD vector combined with 5-fluorocytosine (5-FC) administration was tested to see if it might have significant utility in the chemosensitization of L-plastin positive HCC. Four HCC cell lines (HepG2, Chang Liver, Huh-7 and SK-Hep-1 cells) were investigated for the expression of LacZ after infecting the cells with the AdLPLacZ vector containing a 2.4 kb fragment of LP and the LacZ gene. Relatively high levels of LP activity were detected in HepG2, followed by Chang Liver cells; whereas, no promoter activity was found in Huh-7 and SK-Hep-1 cells, as determined by AdLPLacZ infection followed by the beta-galactosidase assay. In addition, the results of RT-PCR assays for the detection of endogenous L-plastin mRNA in these cells lines correlated well with those of the beta-galactosidase activity after infection with AdLPLacZ. Based on these data, the cytotoxic effect of AdLPCD/5-FC was evaluated in HepG2 cells. These results indicate that the CD gene delivered by AV could sensitize HepG2 cells to the prodrug, 5-FC. However, the observed effects were insufficient to cause the death of most of cells. This suggests that the screening of patients for an AdLP/5-FC strategy based on AdLPLacZ data might not always guarantee a good therapeutic outcome.

Rosiglitazone enhances fluorouracil-induced apoptosis of HT-29 cells by activating peroxisome proliferator-activated receptor γ

AIM: To examine whether and how rosiglitazone enhances apoptosis induced by fluorouracil in human colon cancer (HT-29) cells.

METHODS: Human colon cancer HT-29 cells were cultured in vitro and treated with fluorouracil and/or rosiglitazone. Proliferation and growth of HT-29 cells were evaluated by MTT assay and trypan blue exclusion methods, respectively. The apoptosis of HT-29 cells was determined by acridine orange/ethidium bromide staining and flow cytometry using PI fluorescence staining. The expressions of peroxisome proliferator-activated receptor γ (PPARγ), Bcl-2 and Bax in HT-29 cells were analyzed by Western blot.

RESULTS: Although rosiglitazone at the concentration below 30 μmol/L for 72 h exerted almost no inhibitory effect on proliferation and growth of HT-29 cells, it could significantly enhance fluorouracil-induced HT-29 cell proliferation and growth inhibition. Furthermore, 10 μmol/L rosilitazone did not induce apoptosis of HT-29 cells but dramatically enhanced fluorouracil-induced apoptosis of HT-29 cells. However, rosiglitazone did not improve apoptosis induced by fluorouracil in HT-29 cells pretreated with GW9662, a PPARγ antagonist. Meanwhile, the expression of Bax and PPARγ was up-regulated, while the expression of Bcl-2 was down regulated in HT-29 cells treated with rosiglitazone in a time-dependent manner. However, the effect of rosiglitazone on Bcl-2 and Bax was blocked or diminished in the presence of GW9662.

CONCLUSION: Rosiglitazone enhances fluorouracil-induced apoptosis of HT-29 cells by activating PPARγ.

Chemotherapy Dosing Part II: Alternative Approaches and Future Prospects

This overview follows on from part I, which described the current practices used in chemotherapy dosing and the paucity of scientific evidence to support them. In part II, alternative approaches are discussed, both in terms of scientific rationale and practical application. These include therapeutic drug monitoring, the use of pharmacokinetic-pharmacodynamic relationships, flat-fixed dosing, Bayesian modelling and dose banding.

Antitumor immune response induced by i.t. injection of vector-activated dendritic cells and chemotherapy suppresses metastatic breast cancer

S.c. injection of the Ad-sig-tumor-associated antigen (TAA)/ecdCD40L vector vaccine has been shown to induce a CD8 immune response against TAA for up to 1 year. The first goal of this article is to test if the injection of autologous dendritic cells infected ex vivo with the Ad-sig-TAA/ecdCD40L can increase the immune response induced against TAA. The second goal is to test the effect of adding local chemotherapy in the form of i.t. injection of the AdCDIRESE1A vector-directed chemotherapy on the immune response induced by i.t. injection of adenoviral vector-activated dendritic cells. The results show that the i.t. injection of the AdCDIRESE1A chemotherapy sensitization vector, which encodes the cytosine deaminase chemotherapy sensitization transcription unit, to the i.t. injection of Ad-sig-ecdCD40L vector-infected dendritic cells increased the level of suppression of the growth of the CCL-51 breast cancer cells. The combination of i.t. injection of the AdCDIRESE1A chemotherapy sensitization vector and Ad-sig-ecdCD40L vector-infected dendritic cells into s.c. CCL-51 breast cancer nodules suppressed the growth of uninjected metastatic tumor nodules in the lung. Finally, adding the i.t. injection of the AdCDIRESE1A chemotherapy sensitization vector to the i.t. administration of dendritic cells infected with a rat HER-2/neu (rH2N)-expressing vector (Ad-sig-rH2N/ecdCD40L) led to the induction of rH2N-specific antitumoral immunity in rH2N transgenic mice (which are anergic to the rH2N antigen). This anti-rH2N immune response suppressed the growth of established H2N-positive NT2 breast cancer more efficiently than did the vector-targeted chemotherapy or Ad-sig-rH2N/ecdCD40L-infected dendritic cell vaccine alone.

Sensitivity of 5-fluorouracil-resistant cancer cells to adenovirus suicide gene therapy

A promising approach for cancer gene therapy is the combination of adenovirus vectors (AdV) with the suicide gene cytosine deaminase and uracil phosphoribosyl transferase (CDColon, two colonsUPRT). While such vectors have been tested in tumor cell lines and xenograft models, it is not clear how these therapeutic vectors would perform in primary human tumors. We, thus, examined the effect of the combination of a recombinant adenovirus expressing the CDColon, two colonsUPRT (AdCU) with 5-fluorocytosine (5-FC) on primary cancer cells isolated from the ascites or pleural fluids of patients with metastatic cancers. In such models, we have found a direct correlation between the patients' response to 5-FU and the response shown by the cancer cells in vitro, confirming the clinical relevance of this methodology. Our findings demonstrated that this combination was able to kill primary tumor cells, including those that had developed resistance to 5-FU. Furthermore, while proliferating cells were more susceptible to 5-FU, the combination was effective in both rapid and slow proliferating samples. Our study demonstrated that this gene therapy approach could provide an effective therapeutic option for cancers and is not affected by acquired 5-FU resistance. Also of importance is the effectiveness of this gene therapy approach on slower proliferating cells that is typical of the majority of cancers in vivo. This suggests a greater likelihood that it will be effective in a clinical setting.

Virus-based therapies for colon cancer

Viral vectors are under development for anticancer therapy. As they can infect tumours and activate the immune system, viral vectors may directly destroy cancers (oncolysis), deliver genes with antitumour activity directly to the cancer cells, or act as cancer vaccines. Better insights into the biology of the various vectors in use (e.g., poxvectors, adenovirus, adeno-associated virus, reovirus, Newcastle disease virus) are making it possible to engineer viruses that are more tumour-specific, efficient at tumour infection, and which have enhanced safety due to incorporation of safeguards should dissemination occur. As considerable research has focused on therapy of colon cancer with viral vectors, this review will illustrate the major concepts of viral therapy of cancers with examples from studies targeting colorectal carcinoma.

Plastins: versatile modulators of actin organization in (patho)physiological cellular processes

Many actin-binding proteins are expressed in eukaryotic cells. These polypeptides assist in stabilizing and rearranging the organization of the actin cytoskeleton in response to external stimuli, or during cell migration and adhesion. Here we review a particular set of actin-binding proteins called plastins. Plastins (also called fimbrins) belong to a subclass of actin-binding proteins known as actin bundling proteins. Three isoforms have been characterized in mammals: T-plastin is expressed in cells from solid tissue, whereas L-plastin occurs predominantly in hematopoietic cells. The third isoform, I-plastin, is specifically expressed in the small intestine, colon and kidney. These proteins share the unique property of cross-linking actin filaments into tight bundles. Although plastins are primarily involved in regulation of the actin cytoskeleton, they possess some unique features. For instance, they are implicated in invasion by pathogenic bacteria such as Shigella flexneri and Salmonella typhimurium. Also, L-plastin plays an important role in leukocyte function. T-plastin, on the other hand, is possibly involved in DNA repair. Finally, both T- and L-plastin are implicated in several diseases, and L-plastin is considered to be a valuable marker for cancer.