Human tumor necrosis factor-alpha mutant RGD-V29 (F4614) shows potent antitumor activity and reduced toxicity against human tumor xenografted nude mice

Apoptosis-Inducing TNF Superfamily Ligands for Cancer Therapy

Cancer is a complex disease with apoptosis evasion as one of its hallmarks; therefore, apoptosis induction in transformed cells seems a promising approach as a cancer treatment. TNF apoptosis-inducing ligands, which are naturally present in the body and possess tumoricidal activity, are attractive candidates. The most studied proteins are TNF-α, FasL, and TNF-related apoptosis-inducing ligand (TRAIL). Over the years, different recombinant TNF family-derived apoptosis-inducing ligands and agonists have been designed. Their stability, specificity, and half-life have been improved because most of the TNF ligands have the disadvantages of having a short half-life and affinity to more than one receptor. Here, we review the outlook on apoptosis-inducing ligands as cancer treatments in diverse preclinical and clinical stages and summarize strategies of overcoming their natural limitations to improve their effectiveness.

Integrin targeted delivery of chemotherapeutics

Targeted delivery of chemotherapeutics is defined in the sense, that is, to maximize the therapeutic index of a chemotherapeutic agent by strictly localizing its pharmacological activity to the site or tissue of action. Integrins are a family of heterodimeric transmembrane glycoproteins involved in a wide range of cell-to-extracellular matrix (ECM) and cell-to-cell interactions. As cell surface receptors, integrins readily interact with extracellular ligands and play a vital role in angiogenesis, leukocytes function and tumor development, which sets up integrins as an excellent target for chemotherapy treatment. The peptide ligands containing the arginine-glycine-aspartic acid (RGD), which displays a strong binding affinity and selectivity to integrins, particularly to integrin αvβ3, have been developed to conjugate with various conventional chemotherapeutic agents, such as small molecules, peptides and proteins, and nanoparticle-carried drugs for integtrin targeted therapeutic studies. This review highlights the recent advances in integrin targeted delivery of chemotherapeutic agents with emphasis on target of integrin αvβ3, and describes the considerations for the design of the diverse RGD peptide-chemotherapeutics conjugates and their major applications.

Increasing the antitumor efficacy of doxorubicin-loaded liposomes with peptides anchored via a chelator lipid

The therapeutic efficacy of anticancer drugs like doxorubicin can be significantly increased by their incorporation into liposomes, but an ability to actively target the drug-containing liposomes to tumors could well provide an even greater curative effect. In this work, a commercial preparation of doxorubicin-loaded liposomes (Caelyx) was modified by incorporation of the metal chelator lipid 3(nitrilotriacetic acid)-ditetradecylamine (NTA(3)-DTDA) to enable engraftment of histidine-tagged targeting molecules. Our results show that when engrafted with p15-RGR, a His-tagged peptide containing a sequence purported to bind platelet-derived growth factor receptor β (PDGFRβ), NTA(3)-DTDA-containing Caelyx (3NTA-Caelyx) can be targeted to NIH-3T3 cells in vitro, leading to increased cytotoxicity compared with non-targeted 3NTA-Caelyx. PDGFRβ is known to be expressed on pericytes in the tumor vasculature; however, when radiolabeled p15-RGR liposomes were administered to mice bearing subcutaneous B16-F1 tumors, minimal accumulation into tumors was observed. In contrast, an alternative targeting peptide, p46-RGD, was found to actively direct liposomes to tumors (4.7 %ID/g). Importantly, when injected into tumor-bearing mice, p46-RGD-engrafted 3NTA-Caelyx significantly decreased the tumor growth rate compared with controls. These results indicate that the incorporation of NTA(3)-DTDA into liposomal drugs could represent a simple modification to the drug to allow engraftment of targeting molecules and to increase its efficacy.

Target-selective activation of a TNF prodrug by urokinase-type plasminogen activator (uPA) mediated proteolytic processing at the cell surface

We have previously developed TNF prodrugs comprised of a N-terminal scFv targeting, a TNF effector and a C-terminal TNFR1-derived inhibitor module linked to TNF via a MMP-2 motif containing peptide, allowing activation by MMP-2-expressing tumor cells. To overcome the known heterogeneity of matrix metalloprotease expression, we developed TNF prodrugs that become processed by other tumor and/or stroma-associated proteases. These TNF prodrugs comprise either an uPA-selective or a dual uPA-MMP-2-specific linker which displayed efficient, target-dependent and cleavage sequence-specific activation by the corresponding tumor cell-expressed proteases. Selective pharmacologic inhibition of endogenous uPA and MMP-2 confirm independent prodrug processing by these two model proteases and indicate the functional superiority of a prodrug containing a multi-specific protease linker. Processing optimised TNF prodrugs should increase the proportion of active therapeutic within the targeted tissue and thus potentially enhance tumor response rate.

The antimelanoma immunocytokine scFvMEL/TNF shows reduced toxicity and potent antitumor activity against human tumor xenografts

The immunocytokine scFvMEL/TNF, a fusion protein composed of human tumor necrosis factor (TNF) and a single-chain Fv antibody (scFv) scFvMEL targeting the melanoma gp240 antigen, demonstrates impressive cytotoxic effects against human melanoma cell lines in vitro. Pharmacokinetic studies of 125I-scFvMEL/TNF in BALB/c mice showed that the construct clears from the circulation with a terminal-phase half-life of 17.6 hours after intravenous administration. The maximum tolerated dose of scFvMEL/TNF in nude mice was 4 mg/kg, i.v., on a daily x5 schedule. There were no changes in gross pathology, clinical chemistry, or hematologic parameters in mice treated at doses of up to 3 mg/kg. Therapeutic studies at a dose of 2.5 mg/kg on athymic mice bearing established (approximately 50 mm3) human melanoma A375GFP xenograft tumors transfected with green fluorescent protein demonstrated potent tumor suppression and complete tumor regression of all lesions. There was no subsequent outgrowth of tumors from mice rendered tumor-free. These data show that scFvMEL/TNF can target melanoma cells in vivo and can result in pronounced antimelanoma effects after systemic administration. Toxicology studies indicate the relative safety of this agent at doses that are therapeutically effective and provide guidance to projected phase I starting doses on patients at this schedule.

Influence of rmhTNF on the chemotherapy treatment of small cell lung cancer

The efficacy and safety of the recombinant mutant human tumor necrosis factor (rmhTNF) combined with chemotherapy vs chemotherapy alone in the treatment of patients with small cell lung cancer (SCLC) were evaluated in this study. The selected 37 patients with SCLC were divided into experimental group (n =18) and control group (n = 19). Both groups were subjected to EP regimen. While in the experimental group, a regimen of 4 x 10(6) U/m2 rmhTNF intramuscular injection was given once a day from the 1st to 7th day and 11th to 17th day on the chemotherapy cycle. Twenty-one days were as a chemotherapy cycle and all patients received treatment with 2 cycles. The response rate was 83.3% (15/18) in the experimental group and 63.2% (12/19) in the control group respectively (P < 0.05). The KPS score after treatment was 78.4 +/- 9.6 in the experimental group and 71.2 +/- 9.7 in the control group with the difference being significant (P < 0.05). No severe adverse effects occurred in the two groups. It was concluded that the curative effectiveness of the rmhTNF combined with chemotherapy in the treatment of SCLC was more satisfactory than chemotherapy alone. The former could obviously improve the quality of life of the patients with SCLC.

Enhancement of sensitivity to tumor necrosis factor alpha in non-small cell lung cancer cells with acquired resistance to gefitinib

Tumor cells that have acquired resistance to gefitinib through continuous drug administration may complicate future treatment. To investigate the mechanisms of acquired resistance, we established PC-9/ZD2001, a non-small-cell lung cancer cell line resistant to gefitinib, by continuous exposure of the parental cell line PC-9 to gefitinib. After 6 months of culture in gefitinib-free conditions, PC-9/ZD2001 cells reacquired sensitivity to gefitinib and were established as a revertant cell line, PC-9/ZD2001R. PC-9/ZD2001 cells showed collateral sensitivity to several anticancer drugs (vinorelbine, paclitaxel, camptothecin, and 5-fluorouracil) and to tumor necrosis factor alpha (TNF-alpha). Compared with PC-9 cells, PC-9/ZD2001 cells were 67-fold more sensitive to TNF-alpha and PC-9/ZD2001R cells were 1.3-fold more sensitive. Therefore, collateral sensitivity to TNF-alpha was correlated with gefitinib resistance. PC-9/ZD2001 cells expressed a lower level of epidermal growth factor receptor (EGFR) than did PC-9 cells; this down-regulation was partially reversed in PC-9/ZD2001R cells. TNF-alpha-induced autophosphorylation of EGFR (cross-talk signaling) was detected in all three cell lines. However, TNF-alpha-induced Akt phosphorylation and IkappaB degradation were observed much less often in PC-9/ZD2001 cells than in PC-9 cells or PC-9/ZD2001R cells. Expression of the inhibitor of apoptosis proteins c-IAP1 and c-IAP2 was induced by TNF-alpha in PC-9 and PC-9/ZD2001R cells but not in PC-9/ZD2001 cells. This weak effect of EGFR on Akt pathway might contribute to the TNF-alpha sensitivity of PC-9/ZD2001 cells. These results suggest that therapy with TNF-alpha would be effective in some cases of non-small-cell lung cancer that have acquired resistance to gefitinib.

A mutated human tumor necrosis factor-alpha improves the therapeutic index in vitro and in vivo

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) is a multifunctional cytokine that has cytotoxic, cytostatic and immunomodulatory effects on malignant tumors. However, clinical trials have revealed high systemic toxicity and this has hampered its utilization as an anti-cancer agent. In this study, a human TNF-alpha mutant was created and tested for its anti-tumor effects.

METHODS

The TNF mutant (recombinant mutated human TNF; rmhTNF) was prepared by protein engineering in which amino acids Pro, Ser and Asp at positions 8, 9 and 10 of TNF-alpha were substituted by Arg, Lys and Arg, and C terminal Leu157 was substituted by Phe, along with deletion of the first seven N-terminal amino acids. Prokaryotic expression recombinant vector pBV-mhTNF containing the PLPR promotor was constructed and transformed into E. coli DH5alpha. The rmhTNF was expressed in a partially soluble form in DH5alpha, purified from the supernatant of cell lysate by ammonia sulfate precipitation and two sequential chromatographic steps.

RESULTS

The purified rmhTNF was >95% pure by SDS-PAGE stained with silver and high-pressure size exclusion chromatography (SEC-HPLC). Its yield was about 1.22 mg/g wet cell paste. The mutant rmhTNF exhibited an approximately 50-fold increase in cytotoxicity relative to the wild-type rhTNF on the mouse fibroblast cell line L929 in a standard cytotoxicity test, and at least and at least 50 times higher LD50 as wild type rhTNF in mice. In vivo biological activity studies carried out on tumor cell transplanted mice and nude mice also showed a more effective cytotoxicity of rmhTNF than rhTNF.

DISCUSSION

These results suggest that rmhTNF has potential for developing an effective anti-tumor reagent for some tumors.

RGD-based strategies for selective delivery of therapeutics and imaging agents to the tumour vasculature

During the past decade, RGD-peptides have become a popular tool for the targeting of drugs and imaging agents to alphavbeta3-integrin expressing tumour vasculature. RGD-peptides have been introduced by recombinant means into therapeutic proteins and viruses. Chemical means have been applied to couple RGD-peptides and RGD-mimetics to liposomes, polymers, peptides, small molecule drugs and radiotracers. Some of these products show impressive results in preclinical animal models and a RGD targeted radiotracer has already successfully been tested in humans for the visualization of alphavbeta3-integrin, which demonstrates the feasibility of this approach. This review will summarize the structural requirements for RGD-peptides and RGD-mimetics as ligands for alphavbeta3. We will show how they have been introduced in the various types of constructs by chemical and recombinant techniques. The importance of multivalent RGD-constructs for high affinity binding and internalization will be highlighted. Furthermore the in vitro and in vivo efficacy of RGD-targeted therapeutics and diagnostics reported in recent years will be reviewed.

Restoration of membrane TNF-like activity by cell surface targeting and matrix metalloproteinase-mediated processing of a TNF prodrug

Tumor necrosis factor (TNF) prodrugs are fusion proteins comprised of an N-terminal single-chain antibody variable fragment (scFv) targeting a TNF effector and a C-terminal TNF receptor (TNFR)1-derived inhibitor module. Introduction of matrix metalloproteinase (MMP)-2 recognition motifs between TNF and the TNFR1 fragment allowed activation by recombinant MMP-2 and MMP-expressing HT1080 cells. Processing by endogeneous MMPs required specific membrane binding of the TNF prodrug via the targeting scFv, ensuring strictly antigen-dependent activation. Interestingly, TNF bioactivity of the processed prodrug was approximately 1000-fold higher upon scFv-mediated targeting, and signaled juxtatropic cell death also to antigen-negative cells. Microscopical analyses of TNFR2 clustering and TNF receptor-associated factor 2 recruitment at contact sites to adjacent cells revealed the formation of stable TNFR complexes by target-bound, processed prodrug, resembling the increased signal capacity of natural, membrane-expressed TNF. MMP-2-sensitive TNF prodrugs represent novel cytokine-based reagents for targeted cancer therapy, which should be exploitable for MMP-overexpressing tumors.

Fundamental principals of tumor necrosis factor-alpha gene therapy approach and implications for patients with lung carcinoma

Apoptosis, known as programmed cell death, is defined as a cell's preferred form of death under hectic conditions through genetically conserved and complex pathways. There is a decisive balance between stimulatory and inhibitory signaling pathways to maintain homeostasis in cells. In order to shift the balance towards apoptosis, the modulation of both apoptotic and anti-apoptotic pathways represents an attractive target for cancer therapeutics. Currently, chemotherapy and radiotherapy are among the most commonly used treatment modalities against lung cancer. Tumor suppressor gene, p53, is required in order for both of these treatment methods to work as anti-tumor agents. As a result, tumors lacking p53 display resistance to both chemotherapy and radiotherapy. However, death ligands induce apoptosis regardless of p53 status of cells. Thus, these methods constitute a complementary therapeutic approach to currently employed conventional treatment modalities. At present, death ligands are being evaluated as potential cancer therapeutic agents. Since resistance to tumor necrosis factor (TNF)-alpha-mediated apoptosis represented an obstacle for the treatment of patients with lung carcinoma in the earlier attempts, an extensive research was recently initiated to understand molecular mechanism of TNF-alpha signaling. NF-kappaB transcription factors have been demonstrated to modulate the apoptotic program, mostly as blockers of apoptosis in different cell types. In this review, we concentrate on the current progress in the understanding of TNF-alpha-mediated apoptosis for lung carcinoma. Representative models of NF-kappaB-inhibiting gene therapy strategies from various labs including ours are also provided as examples of up-to-date approaches to defeat TNF resistance. In order to give the reader better understanding and appreciation of such approaches, previously unpublished in vivo assays are also incorporated into this review. Current progress in clinical trials using adenovirus-mediated delivery of TNF-alpha is also discussed.