A novel recombinant tumor necrosis factor-alpha mutant with increased anti-tumor activity and lower toxicity

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.

Unleashing endogenous TNF-alpha as a cancer immunotherapeutic

Tumor necrosis factor (TNF)-alpha was originally identified in the 1970s as the serum mediator of innate immunity capable of inducing hemorrhagic necrosis in tumors. Today, a wide spectrum of biological activities have been attributed to this molecule, and clinical translation has mainly occurred not in using it to treat cancer, but rather to inhibit its effects to treat autoimmunity. Clinical trials utilizing systemic TNF-alpha administration have resulted in an unacceptable level of toxicities, which blocked its development. In contrast, localized administration of TNF-alpha in the form of isolated limb perfusion have yielded excellent results in soft tissue sarcomas. Here we describe a novel approach to leveraging the potent antineoplastic activities of TNF-alpha by enhancing activity of locally produced TNF-alpha through extracorporeal removal of soluble TNF-alpha receptors. Specifically, it is known that cancerous tissues are infiltrated with monocytes, T cells, and other cells capable of producing TNF-alpha. It is also known that tumors, as well as cells in the tumor microenvironment produce soluble TNF-alpha receptors. The authors believe that by selectively removing soluble TNF-alpha receptors local enhancement of endogenous TNF-alpha activity may provide for enhanced tumor cell death without associated systemic toxicities.

Structural modeling of tumor necrosis factor: A protein of immunological importance

Tumor necrosis factor (TNF) is a multifunctional pro-inflammatory cytokine responsible for various immunoregulatory activities. Upon binding with its receptor, TNF triggers multiple complex signaling pathways such as the activations of nuclear factor kappa B and caspase cascade, which are the leading determining factors for cell survival or cell death. The present work studies certain modeling aspects of the TNF, with comparative structural analyses of the wild and mutant types of this protein. Additionally, nanoscale molecular dynamics simulations are performed to assess the structure-property relationships of proteins as functions of time.

Tumor vasculature-targeted recombinant mutated human TNF-α enhanced the antitumor activity of doxorubicin by increasing tumor vessel permeability in mouse xenograft models

OBJECTIVE

Increasing evidence suggests that, when used in combination, tumor necrosis factor-α (TNF-α) synergizes with traditional chemotherapeutic drugs to exert a heightened antitumor effect. The present study investigated the antitumor efficacy of recombinant mutated human TNF-α specifically targeted to the tumor vasculature (RGD-rmhTNF-α) combined with the chemotherapeutic agent doxorubicin in 2 murine allografted tumor models.

METHODS

Mice bearing hepatoma or sarcoma allografted tumors were treated with various doses of RGD-rmhTNF-α alone or in combination with doxorubicin (2 mg/kg). We then evaluated tumor growth and tumor vessel permeability as well as intratumoral levels of RGD-rmhTNF-α and doxorubicin.

RESULTS

RGD-rmhTNF-α treatment enhanced the permeability of the tumor vessels and increased intratumoral doxorubicin levels. In addition, intratumoral RGD-rmhTNF-α levels were significantly higher than that of rmhTNF-α. In both of the tested tumor models, administering RGD-rmhTNF-α in combination with doxorubicin resulted in an enhanced antitumor response compared to either treatment alone. Double-agent combination treatment of doxorubicin with 50,000 IU/kg RGD-rmhTNF-α induced stronger antitumor effects on H22 allografted tumor-bearing mice than the single doxorubicin agent alone. Moreover, doxorubicin with 10,000 IU/kg RGD-rmhTNF-α synergized to inhibit tumor growth in S180 allografted tumor-bearing mice.

CONCLUSIONS

These results suggest that targeted delivery of low doses of RGD-rmhTNF-α into the tumor vasculature increases the antitumor efficacy of chemotherapeutic drugs.

Construction of novel tumor necrosis factor-alpha mutants with reduced toxicity and higher cytotoxicity on human tumor cells

Two tumor necrosis factor-alpha mutants MT1 (32Trp157Phe) and MT2 (2Lys30Ser-32Trp 157Phe) were constructed by site-directed mutagenesis. These mutants were soluble and over-expressed inE. coli. The purity of purified mutants was above 95% by serial chromatography. The results of Western blot indicated that these mutants could be cross-reactive with monoclonal antibody against native hTNF-alpha. Compared to parent hTNF-alpha, the cytotoxicity of these mutants on murine fibrosarcoma L929 cell lines reduced 4-5 orders of magnitude but was equivalent to that of native hTNF-alpha on human tumor cell lines. The LD50 of mutant MT1 was reduced to 0.34% of wild type and the dose of MT2 that resulted in 30% death of mice reduced to less than 1/700 that of parent hTNF-alpha.

Cancer relapse under chemotherapy: why TLR2/4 receptor agonists can help

Liver or lung metastases usually relapse under chemotherapy. Such life-threatening condition urgently needs new, systemic anticancer compounds, with original and efficient mechanisms of action. In B16 melanoma mice treated with cyclophosphamide, D'Agostini et al. [D'Agostini, C., Pica, F., Febbraro, G., Grelli, S., Chiavaroli, C., Garaci, E., 2005. Antitumour effect of OM-174 and Cyclophosphamide on murine B16 melanoma in different experimental conditions. Int. Immunopharmacol. 5, 1205-1212.] recently found that OM-174, a chemically defined Toll-like receptor(TLR)2/4 agonist, reduces tumor progression and prolongs survival. Here we review 149 articles concerning molecular mechanisms of TLR2/4 agonists, alone or in combination with chemotherapy. It appears that TLR2/4 agonists induce a well controlled tumor necrosis factor-alpha (TNF-alpha) secretion, at plasma levels known to permeabilize neoangiogenic tumor vessels to the passage of cytotoxic drugs. Moreover, TLR2/4 agonists induce inducible nitric oxide synthase (iNOS) expression, and nitric oxide is able to induce apoptosis of chemotherapy-resistant tumor cell clones. Finally, TLR2/4-stimulation activates dendritic cell traffic and its associated tumor-specific, cytotoxic T-cell responses. Therefore, parenteral TLR2/4 agonists seem promising molecules to prolong survival in cancer patients who relapse under chemotherapy.

TNF-α promotes Doxorubicin-induced cell apoptosis and anti-cancer effect through downregulation of p21 in p53-deficient tumor cells

p53 is a key regulator in cell apoptosis, and cancer cells deficient in p53 expression fail to respond to chemotherapy. Here we show that effective Doxorubicin (DOX)-induced apoptosis is p53-dependent. However, an alternative treatment of DOX/TNF-alpha/DOX restored sensitivity of p53-deficient cells to DOX-induced apoptosis. Treatment of cells with TNF-alpha resulted in a decrease of p21 (waf1/cip1/sdi1) expression following second dose of DOX. In previous work, we demonstrated that p21 suppressed DOX-induced apoptosis via its (cyclin-dependent kinase) CDK-binding and CDK-inhibitory activity. Thus, we propose that TNF-alpha enhances the anti-cancer effect of DOX through suppressing the anti-apoptotic activity of p21, and that a combined treatment TNF-alpha/Dox is an effective chemotherapeutic strategy for p53-deficient cancers.

Mutational analysis of human tumor necrosis factor-alpha

To understand the structure-function relationship of human tumor necrosis factor-alpha (TNF-alpha), mutational analysis was carried out on the lower regions (regions 1-6) of the molecule. The muteins were prepared as a soluble form by using a chaperonin co-expression system and the cytotoxic activities of the purified muteins were evaluated on TNF-sensitive murine fibrosarcoma L929 cells. Three regions (regions 1, 2 & 4) were found where mutations significantly influenced the bioactivity. In region 1 (residues 1-10), the number of deleted residues and the positioning of positive charges are important to achieve a maximum activity and in region 4 (residues 84-88), introduction of charged residues in one of the positions 86-88 significantly increased the cytotoxic activity. On the other hand, any mutation introduced in region 2 (residues 37-41) had a deleterious effect. The present study provides a structural basis for the design of highly potent TNF-alpha as a therapeutic agent.

The effect of chemotherapy combined with recombination mutant human tumor necrosis factor on advanced cancer

Background

Past studies suggested that tumor necrosis factor (TNF) assisted anti-tumor treatment and intensified the sensitivity of chemotherapy. However its clinical application has been curbed because of its low purity, high dosage, and strong toxicity. This research, through perspective random clinical control experiment, observed the therapeutic effect of the treatment of late malignant tumor through the injection of recombinant mutant human tumor necrosis factor (rmhTNF) combined with general chemotherapy and its adverse reactions.

Methods

105 patients with advanced malignant tumor were randomly divided into trial group, 69 patients, and control group, 36 patients. Injection of rmhTNF 4 × 10⁶u/m² was given to the trial group, from the 1^st to 7^th days, the 11^th to 17^th days combined with chemotherapy course. The chemotherapy plan was as follows: CAP for patients with the NSCLC; FAM for patients with gastric cancer; FC for patients with colorectal cancer. One treatment cycle lasted for 21 days and two cycles were scheduled. The control group was given only the same chemotherapy as the trial group.

Results

In the trial group there was 1 CR case and 12 PR cases, and the response rate is 13/69 (18.84%); in the control group 1 PR case, the response rate 1/36 (2.78%). The response rate of the trial group was significantly higher than that of the control group (P = 0.022). The response rate for NSCLC in the trial group was 8/17 (47.06%), and 1/6 (16.67%) in the control group. The response rates for gastric cancer and colorectal cancer in the trial groups also were higher than those of the control groups. After the treatment the KPS is 89.00 ± 9.92 in the trial group, and 84.17 ± 8.84 in the control group, with a significant difference between the two groups (P = 0.028). The adverse reactions of rmhTNF injection included: pain in the injection area, chill, hardening and swelling and redness in the injection area, fever, ostealgia and myosalgia, and cold-like symptoms. All these adverse reactions were mild and bearable.

Conclusions

The administration of rmhTNF injection in combination with general chemotherapy is an effective and secure means in treating advanced malignant tumor.

Primary targeting of recombinant Fv-immunotoxin hscFv25-mTNFα against hepatocellular carcinoma

AIM: To obtain human recombinant Fv-immunotoxin hscFv₂₅-mTNFα (mutant human TNFα fused to human scFv₂₅) against hepatocellular carcinoma (HCC).

METHODS: Two relevant sites of enzymatic digestion were added to mTNFα by PCR. mTNFα was linked to the 3’ end of hscFv₂₅ in pGEX4T-1 vector. This anti-HCC recombinant Fv-immunotoxin hscFv₂₅-mTNFα was expressed in Escherichia coli and purified from inclusions. After purified by glutathione-S-transferase affinity chromatography and thrombin digestion, it was identified by electrophoresis and Western blot. And then, the purified recombinant Fv-immunotoxin was injected into nude mice with HCC xenografts through their tail veins. mTNFα protein and PBS were used as control at the same time. After treated for two weeks, nude mice were executed. The bulk and weight of tumors were observed. The tumor tissues were stained by immunohistochemical method with TNFα antibody.

RESULTS: The expression ratio of recombinant Fv-immunotoxin hscFv₂₅-mTNFα was 12% of bacterial protein. The result of tumor restraining trials of hscFv₂₅-mTNFα showed 2/5 complete remission and 3/5 partial remission. mTNFα restraining trials showed 5/5 partial remission. The therapeutic result of hscFv₂₅-mTNFα was better than that of mTNFα (F = 8.70, P < 0.05). The hscFv₂₅-mTNFα remedial tumor tissues were positive for TNFα by immunohistochemical staining. The positive granules mainly existed in the cytoplasm of tumor cell.

CONCLUSION: Recombinant Fv-immunotoxin hscFv₂₅-mTNFα has better therapeutic effect than mTNFα. It can inhibit the cellular growth of HCC and has some potential of clinical application.

Differentiation induction by a tumor-necrosis-factor mutant 471 in human myelogenous leukemic cells via tumor-necrosis-factor receptor-p55

The present study examined differentiation-inducing activity by various tumor-necrosis-factor(TNF) mutants against the human leukemic cell lines HL-60 and U-937. Mutant TNF 471, from which 7 N-terminal amino acids of native TNF were deleted and Pro8, Ser9 and Asp10 were replaced by Arg, Lys and Arg, possessed the highest activity among the TNF mutants, and its activity was 120-fold that of native TNF. The various biological activities of TNF were signaled through 2 distinct receptors, p55 and p75. Although cytotoxicity was reported to involve mainly p55, this differentiation-inducing activity was not well understood. The fact that the affinity of TNF 471 was higher to p55 and lower to p75 than that of native TNF by a binding competition assay suggested that the differentiation-inducing activity was also signaled through p55. To verify this hypothesis, the human myelogenous leukemic cell line, KG-1, which scarcely expresses either receptor and does not differentiate with TNF, was transduced with the p55 or p75 gene. Subsequently p55 transfectants manifested a greater ability to differentiate; however, p75 transfectants did not differ from parental cells or from mock-transfectants. Further, the differentiation of p55 transfectants induced by TNF was reduced by the inhibitor of protein-kinase-C (PKC), staurosporine. These results indicate that the differentiation-inducing activity was signaled through the TNF receptor, p55, via PKC and that the excellent ability of TNF 471 to induce differentiation was related to its high affinity for p55.

High resolution crystal structure of a human tumor necrosis factor-alpha mutant with low systemic toxicity

A human tumor necrosis factor-alpha (TNF-alpha) mutant (M3S) with low systemic toxicity in vivo was designed, and its structures in two different crystal packings were determined crystallographically at 1.8 and 2.15-A resolution, respectively, to explain altered biological activities of the mutant. M3S contains four changes: a hydrophilic substitution of L29S, two hydrophobic substitutions of S52I and Y56F, and a deletion of the N-terminal seven amino acids that is disordered in the structure of wild-type TNF-alpha. Compared with wild-type TNF-alpha, it exhibits 11- and 71-fold lower binding affinities for the human TNF-R55 and TNF-R75 receptors, respectively, and in vitro cytotoxic effect and in vivo systemic toxicity of M3S are 20 and 10 times lower, respectively. However, in a transplanted solid tumor mouse model, M3S suppresses tumor growth more efficiently than wild-type TNF-alpha. M3S is highly resistant to proteolysis by trypsin, and it exhibits increased thermal stability and a prolonged half-life in vivo. The L29S mutation causes substantial restructuring of the loop containing residues 29-36 into a rigid segment as a consequence of induced formation of intra- and intersubunit interactions, explaining the altered receptor binding affinity and thermal stability. A mass spectrometric analysis identified major proteolytic cleavage sites located on this loop, and thus the increased resistance of M3S to the proteolysis is consistent with the increased rigidity of the loop. The S52I and Y56F mutations do not induce a noticeable conformational change. The side chain of Phe56 projects into a hydrophobic cavity, while Ile52 is exposed to the bulk solvent. Ile52 should be involved in hydrophobic interactions with the receptors, since a mutant containing the same mutations as in M3S except for the L29S mutation exhibits an increased receptor binding affinity. The low systemic toxicity of M3S appears to be the effect of the reduced and selective binding affinities for the TNF receptors, and the superior tumor-suppression of M3S appears to be the effect of its weak but longer antitumoral activity in vivo compared with wild-type TNF-alpha. It is also expected that the 1.8-A resolution structure will serve as an accurate model for explaining the structure-function relationship of wild-type TNF-alpha and many TNF-alpha mutants reported previously and for the design of new TNF-alpha mutants.

Human lymphotoxin mutein lacks hypotensive activity but has higher in vivo antitumor activity than lymphotoxin or tumor necrosis factor

A serious drawback of tumor necrosis factor alpha (TNF) as a clinical antitumor agent is that it also has hypotensive activity. To overcome this problem, derivatives of its sister cytokine lymphotoxin (TNF-beta or LT) were prepared. One of them, mutein 2 (Mut2) has a deletion of amino acids 1-7 but contains substituted amino acids, Met-Phe-Pro at positions 8-10 of the mature human LT. This mutein has no hypotensive activity at the maximum dose (10 mg/kg) tested on rats. In contrast, a much lower dose (1 mg/kg) of TNF and LT caused a significant blood pressure drop. In vivo studies revealed that Mut2 was more effective than TNF or LT against MethA (a mouse tumor line) as judged by the therapeutic ratio [calculated as LD50 (dose that kills 50% of the animals)/ED50 (dose that reduces the tumor size by 50%)]. With five other different mouse tumors and two different human tumors, Mut2 was also effective and the effectiveness was comparable or superior to that of TNF or LT. These results suggest the possibility that this derivative may be usable as a clinical antitumor agent without the serious side effects associated with TNF.

International collaborative study of the candidate international standards for human tumour necrosis factors alpha (hTNF-alpha) and beta (hTNF-beta) and for murine tumour necrosis factor alpha (mTNF-alpha)

Four ampouled preparations of human tumour necrosis factor alpha (hTNF-alpha), one ampoule of human tumour necrosis factor beta (hTNF-beta) and one ampoule of mouse tumour necrosis factor alpha (mTNF-alpha) were evaluated by 20 laboratories in nine countries for their suitability to serve as international standards for these materials. A further three preparations of recombinant hTNF-alpha were included in the study so that hTNF-alpha preparations from different sources and with various structures could be compared. The preparations were assayed using in vitro bioassays and immunoassays. On the basis of the results reported here, with the agreement of participants in the study and with the authorisation of the Expert Committee on Biological Standardization (ECBS) of the World Health Organization (WHO), the preparation of hTNF-alpha in ampoules designated 87/650 was established as the international standard for hTNF-alpha with a defined potency of 40,000 international units per ampoule. Estimates relative to hTNF-alpha for both hTNF-beta and mTNF-alpha showed a substantial inter-laboratory variability in cytotoxic activity indicating that no preparations of hTNF-alpha would be suitable as a reference standard for either hTNF-beta or mTNF-alpha. However, given the current need for reference preparations for these materials, the ampouled preparations of hTNF-beta (87/640) and mTNF-alpha (88/532) were assigned potencies in arbitrary units and are available as reference reagents.

Human tumor necrosis factor mutants with preferential binding to and activity on either the R55 or R75 receptor

Previously, we reported that the cytotoxic activity of human (h) tumor necrosis factor (TNF) on murine (m) L929 cells requires the integrity of three loops (positions 30-36, 84-88 and 138-150) which cluster around the interface between each two subunits of the trimeric hTNF structure. The collection of hTNF mutants was further characterized by their activity on various human cell systems as well as by their binding to the two types of hTNF receptor (R), R55 and R75. It turned out that two amino acids (Leu29 and Arg32) were specifically involved in hR75 binding, as Leu29-->Ser (L29S) and Arg32-->Trp (R32W) mutant molecules had largely lost binding to hR75, but not to hR55. In order to screen for more highly R55-specific mutants, nine other amino acids were inserted at these two positions; only the substitutions L29G and L29Y showed an increased differential binding as compared to L29S, while no further improvement was found with mutations at position 32 compared to R32W. Biological assays mediated either by hR55 or hR75 confirmed the results obtained by physical binding to purified receptors. A similar substitution in mTNF, Arg32-->Tyr, also resulted in a preferential loss of binding to hR75 and a large decrease in mR75-mediated bioactivity. Except for the double mutant L29S-R32W, all other tested amino acid substitutions in the loops at positions 30-36 or 84-88 of hTNF led to a substantial loss of affinity for both receptors and a concomitant reduction of biological activity. In the loop at positions 138-150, the non-conservative replacement of Glu by Lys at position 146 (E146K) resulted in an even lower binding to R75 as compared to R32W, while binding on and bioactivity through R55 was only slightly reduced. Remarkably, a reversed differential binding was observed after substitution at position 143 in hTNF; replacing Asp by non-conservative residues such as Tyr, Phe or Asn resulted in a much larger decrease in binding to R55 than to R75. In conclusion, receptor-specific mutants such as R32W, E146K and D143N can be used to study the function either of R55 or R75 on different human cell types. In vivo, we presume that the R55-specific mutants will retain antitumor activity in the absence of R75-dependent, severe side effects.

Lysosome labilizers potentiate the antitumor effects of tumor necrosis factor-alpha

Enhancement of in vitro cytotoxic activity of tumor necrosis factor-alpha (TNF-alpha) was observed in combination with lysosome labilizers, particularly with urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA) and lipoprotein lipase (LPL). The concentration of TNF-alpha resulting in 50% cytotoxicity to L929 cells was only 20-30% of the value for TNF-alpha alone, when used in combination with a nontoxic dose of u-PA, t-PA or LPL. Furthermore, combined intravenous (i.v.) administration of TNF-alpha (3.5 x 10(5) U/mouse) and u-PA (300 IU/mouse) markedly increased the in vivo antitumor activity of TNF-alpha to Meth A tumors transplanted into BALB/c mice; the tumor weight in co-administered mice was about 40% of that in mice given TNF-alpha alone on day 6. The combination therapy of TNF-alpha (7.0 x 10(4) U/mouse, i.v.) and u-PA (300 IU/mouse, i.v.) was also effective for L929 tumors in Crj:CD-1(1CR)-nu nude mice compared with the conventional therapy with TNF-alpha alone. These results suggest that the combination of TNF-alpha and lysosome labilizers is a promising antitumor therapeutic regimen with clinical potential.