The characterization of novel, dual ErbB-2/EGFR, tyrosine kinase inhibitors: potential therapy for cancer

The type I receptor tyrosine kinases constitute a family of transmembrane proteins involved in various aspects of cell growth and survival and have been implicated in the initiation and progression of several types of human malignancies. The best characterized of these proteins are the epidermal growth factor receptor (EGFR) and ErbB-2 (HER-2/neu). We have developed potent quinazoline and pyrido-[3,4-d]-pyrimidine small molecules that are dual inhibitors of ErbB-2 and EGFR. The compounds demonstrate potent in vitro inhibition of the ErbB-2 and EGFR kinase domains with IC(50)s <80 nM. Growth of ErbB-2- and EGFR-expressing tumor cell lines is inhibited at concentrations <0.5 microM. Selectivity for tumor cell growth inhibition versus normal human fibroblast growth inhibition ranges from 10- to >75-fold. Tumor growth in mouse s.c. xenograft models of the BT474 and HN5 cell lines is inhibited in a dose-responsive manner using oral doses of 10 and 30 mg/kg twice per day. In addition, the tested compounds caused a reduction of ErbB-2 and EGFR autophosphorylation in tumor fragments from these xenograft models. These data indicate that these compounds have potential use as therapy in the broad population of cancer patients overexpressing ErbB-2 and/or EGFR.

Indazolylamino quinazolines and pyridopyrimidines as inhibitors of the EGFr and c-erbB-2

Described herein is the design and synthesis of indazolylaminopyridopyrimidines and quinazolines as inhibitors of the class 1 tyrosine kinase receptor family. Data is presented for N(4)-(1-benzyl-1H-indazol-5-yl)-N(6),N(6)-dimethylpyrido[3,4-d]pyrimidine-4,6-diamine 3B. This compound inhibited EGFr and c-erbB-2 enzymes selectively over other kinases. It inhibited the proliferation of a range of tumour cell lines in vitro and the growth of BT474 xenografts in SCID mice.

An element within the 5' untranslated region of human Hsp70 mRNA which acts as a general enhancer of mRNA translation

The untranslated regions of mRNAs encoding heat-shock proteins have been reported to contain elements important to the post-transcriptional regulation of these key components of the stress response. In this report we describe an element from the 5'UTR of human Hsp70 mRNA that increases the efficiency of mRNA translation. Cloning of this region upstream of the coding sequence of two different reporter genes (firefly luciferase and chloramphenicol acetyltransferase) increases expression of the reporter under normal cell culture conditions by up to an order of magnitude. This effect was observed in three different promoter contexts (HSP, SV40 and CMV) and in six cell lines. The increase in protein production is not accompanied by any alteration in mRNA levels, suggesting that the element facilitates translation. 5' or 3' truncated sequences are ineffective in enhancing reporter expression, suggesting that the activity arises from the secondary structure of the element, rather than from some smaller defined motif. Computer analysis of this region revealed that it is able to form stable secondary structures (DeltaG approximately -292.6 kJ x mol(-1)). The Hsp70 element does not seem to act as an internal ribosome entry site. Incorporation of the sequence into plasmids used for DNA vaccination produces increased antibody responses, confirming that the sequence is functional in primary cells. These data suggest that the 5'UTR of human Hsp70 mRNA plays an important role in determining Hsp70 expression levels, and that it contains an element of general utility in enhancing recombinant protein expression systems.

Early commitment of adoptively transferred CD4+ T cells following particle-mediated DNA vaccination: implications for the study of immunomodulation

The early responses of CD4+ T cells to particle-mediated DNA immunisation were investigated using OVA-specific TCR-transgenic CD4+ T cells. Following adoptive transfer of these cells, mice were immunised by delivery into the skin of a plasmid encoding ovalbumin. Transgenic T cells underwent a rapid and transient antigen-specific activation, followed by clonal expansion (up to approximately 6% of total lymphocytes). Immunisation with ovalbumin in CFA evoked similar responses with slightly faster kinetics. Numerous antigen-specific T cells synthesising IFN-gamma (Th1) and IL-4 (Th2) were detectable using both intracellular staining and ELISPOT assays. This study provides a quantitative analysis of both T cell proliferation and Th1/Th2 balance following particle-mediated DNA immunisation and establishes a robust and sensitive model in which to assess modulation of helper T cell responses in DNA vaccination.

Cross-linking of the CAMPATH-1 antigen (CD52) mediates growth inhibition in human B- and T-lymphoma cell lines, and subsequent emergence of CD52-deficient cells

The CAMPATH-1H (CD52) antigen is a 21 000-28 000 MW glycopeptide antigen that is highly expressed on T and B lymphocytes and is coupled to the membrane by a glycosylphosphatidylinositol (GPI) anchoring structure. The humanized CAMPATH-1H anti-CD52 antibody is extremely effective at mediating depletion of both normal and tumorigenic lymphocytes in vivo and has been used in clinical trials for lymphoid malignancy and rheumatoid arthritis. Cross-linking GPI-anchored molecules, including CD52, on the surface of T lymphocytes in the presence of phorbol 12-myristate 13-acetate or anti-CD3, results in cellular activation. In the present study we have investigated the functional effects of cross-linking CD52 on T and B tumour cell lines. Cross-linking CD52 on either a B-cell line, Wien 133, which expresses high levels of endogenous CD52 or Jurkat T cells transfected and selected to express high levels of CD52 resulted in growth inhibition. This effect showed slower kinetics and occurred in a lower percentage of cells than growth inhibition stimulated via T- or B-cell receptors. Growth inhibition of the Wien 133 line was followed by the induction of apoptosis, which appeared independent of the Fas/Fas L pathway. Wien 133 cells surviving anti-CD52 treatment were selected and cloned and found to have down-regulated CD52 expression, with a characteristic biphasic pattern of 10% CD52-positive, 90% negative by fluorescence-activated cell sorter analysis. Interestingly, surface expression of other GPI-linked molecules, such as CD59 and CD55, was also down-regulated, but other transmembrane molecules such as surface IgM, CD19, CD20, HLA-DR were unaffected. The present study and previous work show that this is due to a defect in the synthesis of mature GPI precursors. Separation of CD52-positive and negative populations in vitro resulted in a rapid redistribution to the mixed population. Injection of CD52-negative cells into nude mice to form a subcutaneous tumour resulted in a substantial increase in expression of CD52. These results suggest that the defect in the Wien 133 cells is reversible, although the molecular mechanism is not clear. These observations have relevance to the clinical situation as a similar GPI-negative phenotype has been reported to occur in lymphocytes following CAMPATH-1H treatment in vivo.

Selective inhibition of inducible nitric oxide synthase inhibits tumor growth in vivo: studies with 1400W, a novel inhibitor

We have investigated the effect of N-(3-(aminomethyl)benzyl)acetamidine (1400W), a novel and highly selective inhibitor for inducible NOS (iNOS), on in vivo growth of solid tumors expressing iNOS. For the EMT6 murine mammary adenocarcinoma, in which iNOS is expressed in the tumor cells, continuous infusion of 1400W for 6 days at 10 or 12 mg/kg(-1)/h(-1) resulted in significant reduction in tumor weight (357 +/- 46 and 466 +/- 70 mg, respectively) compared with that of controls [726 +/- 65 (P < 0.001) and 796 +/- 88 mg (P < 0.02), respectively]. Reduced growth was also observed for a human tumor xenograft (colon adenocarcinoma DLD-1) genetically engineered to express iNOS constitutively and treated for 13 days with 6 mg/kg(-1)/h(-1) 1400W compared with controls (tumor weights 340 +/- 50 and 580 +/- 90 mg, respectively; P < 0.03). Growth of the parental DLD-1 clone was not altered with this treatment compared with that of controls (tumor weights 170 +/- 10 and 240 +/- 50 mg, respectively). Inhibition of iNOS in vivo was confirmed by decreases in plasma nitrite + nitrate concentrations in treated animals compared with that of controls (63-83% decreases for all experiments) and was supported by plasma and tumor concentrations of 1400W that were equivalent and 2.6-4.9 times higher than the EC50 previously reported for iNOS in a tissue assay. For the murine colon adenocarcinoma Colon 38, in which intratumoral macrophages are the predominant source of iNOS and which had high intratumoral arginine concentrations, 1400W treatment had no effect on growth or plasma nitrate + nitrate. Future studies with more potent selective iNOS inhibitors and a wider range of tumors may determine whether iNOS inhibitors could represent a novel approach to the treatment of cancer. These studies confirm that nitric oxide production in tumors plays a role in promoting their growth, rather than a role as a host defense mechanism in inhibiting growth.

Recognition of CD52 allelic gene products by CAMPATH-1H antibodies

Cloning of the CD52 from a B-lymphocyte tumour cDNA library revealed two closely related sequences differing only at two amino acids C-terminal to the proposed point of glycosylphosphatidylinositol (GPI)-linkage. When transfected into CHO cells only one of these sequences gave high-level expression of the antigen recognized by the prototypic anti-CD52 antibody CAMPATH-1 whereas in JURKAT cells good expression levels were obtained with both sequences. Fusion of the sequence from the second sequence to DNA encoding the extracellular domain of CD4 indicated that this sequence was capable of directing GPI linkage. The possible implications for the function of CD52 and serotherapy with anti-CD52 antibodies are discussed.

Development and characterization of a novel xenograft model permissive for human papillomavirus DNA amplification and late gene expression

Human papillomaviruses (HPVs) are important human pathogens associated with a range of epithelial neoplasia. The rising incidence of HPV infection and association of HPV with malignancy has led to increased interest in appropriate management of these infections. Development of new therapies for viral warts has been frustrated by the lack of availability of models permissive for viral replication. Here we describe the development of HPV-severe combined immunodeficient mouse model which reproduces mature HPV-infected epithelia. Grafting of anogenital and laryngeal papillomas harbouring either HPV-6 or HPV-11 resulted in the formation of a differentiated neo-epithelium exhibiting the hallmark features of HPV infection including basal hyperplasia, acanthosis and koilocytosis. The reformed warty epithelium contained amplified HPV DNA and expressed capsid protein in the differentiated layers. A striking feature is the production of macroscopic papillomata in an anatomically relevant and accessible site, providing a system of particular relevance for the temporal evaluation of developing lesions and selection of antiviral agents.

Effect of purine synthesis inhibition on WiDr spheroids in vitro or on WiDr or colon 38 tumors in vivo. Complete growth inhibition but not regression

Clinical responses for anticancer agents are based upon tumor regression. We have investigated the potential of glycineamide ribonucleotide transformylase (GAR TFase) inhibitors to produce regressions in multiple preclinical models of colon carcinoma. The growth of multicellular tumor spheroids of WiDr human colon carcinoma was inhibited by the GAR TFase inhibitors 5-deazaacyclotetrahydrofolate (5-DACTHF), its 2'-fluoro, 3'-fluoro, 10-deaza, and 10-thia analogs as well as 5,10-dideazatetrahydrofolate, but none of the compounds caused spheroid regressions. By contrast, complete spheroid disruption was observed with exposure to etoposide, m-AMSA (amsacrine), piritrexim, or 2-desamino-2-methyl-10-propargyl-5,8-dideazafolate (DMPDDF). Light microscopy of the spheroids treated with either 5-DACTHF or DMPDDF suggested that the reason for the difference is extensive cell kill throughout the spheroid in the presence of DMPDDF compared with little or no kill, over that found in controls, with 5-DACTHF. Treatment of spheroids with 5-DACTHF in the presence of 1 microM hypoxanthine resulted in no significant reversal of growth inhibition; 50% reversal required 10 microM hypoxanthine. The spheroid studies were extended to in vivo studies examining the effects of 5-DACTHF on established WiDr and colon 38 tumors. The results showed that, in contrast to melphalan, which produced cures and tumor regressions, 5-DACTHF produced reversible growth inhibition with no significant regression of tumors. The results predict that clinical response, typically measured by tumor regression, may be rare following single agent therapy with inhibitors of de novo purine biosynthesis.

A novel cell-based assay for the evaluation of anti-ras compounds

In order to identify drugs active against mutated ras oncogenes we have developed an in vitro assay employing two clones of the human fibrosarcoma cell-line, HT1080 which carries an N-ras gene mutated at codon 61. Clone, HT1080scc2, retains the transformed phenotype of the parental line, whilst the other, HT1081c, is a morphologically flat, non-tumourigenic, revertant with under-representation of the chromosome carrying the transforming N-ras allele. The clear implication of mutant ras in maintaining the transformed nature of HT1080scc2 was confirmed when these cells were microinjected with the pan ras neutralising antibody Y13-259, which resulted in the morphological detransformation of these cells to a phenotype resembling that of the HT10801c clone. A number of known anti-cancer drugs with modes of action unrelated to ras function were found to be equipotent against both clones. However, when compounds chosen on the grounds of their potential selective cytotoxic or differentiating activity were tested some interesting results were obtained. Thus 8-bromo cAMP affected some morphological detransformation of HT1080scc2 cells and reduced their colony forming potential. The IMP-dehydrogenase inhibitors, tiazafurin and mycophenolic acid also flattened the morphology of the transformed clone. Fumagillin, an antibiotic reported to exhibit selective activity against ras transformed cells showed very marked and selective cytostatic effects against HT1080scc2 cells with IC50 values as low as 1 x 10(-11) M.

Effect of reconstituted basement membrane components on the growth of a panel of human tumour cell lines in nude mice

Previous reports have indicated that reconstituted basement membrane (matrigel), when co-injected with either established or primary human tumour cells, can improve the growth of subcutaneous xenografts in nude mice. The human adenocarcinoma cell lines A549, SW480, and WiDr, and the human fibrosarcoma cell line HT1080scc2 exhibit varying degrees of tumourigenicity in nude mice. All these lines showed increased tumorigenicity and/or growth rate, together with a change towards a more differentiated tissue morphology, when co-injected with matrigel into nude mice. Experiments using A549 cell line have indicated that the effect of matrigel is concentration-dependent and that increased growth rate is not maintained when xenografts grown with matrigel are passaged into further mice. These results strongly suggest that increased tumour growth results from the improved growth conditions afforded by matrigel, rather than from the selection of subpopulations of the most tumourigenic cells. Increased growth of intracaecal tumours arising from the co-injection of SW480 cells with matrigel, indicate a possible use for matrigel in the development of more relevant animal models using the orthotopic site. Purified laminin significantly increased the growth of sc tumours resultant from co-injection with either WiDr or A549 cells, whereas collagen IV or laminin with entactin showed no such effect. A role for free laminin in the stimulation of cell growth in the absence of an intact basement membrane is discussed.

Fasciola hepatica in vitro: increased susceptibility to fasciolicides in a defined serum-free medium

The cidal properties of some phenolic, halogenated diphenyl, salicylanilide, benzimidazole and diaminophenoxyalkane anthelmintics, against 6-week-old worms of Fasciola hepatica were assessed in vitro. In a conventional fluke culture medium containing RPMI 1640, supplemented with serum with or without rabbit erythrocytes or pink-ghosts, only the halogenated diphenyl and salicylanilide compounds showed activity at concentrations equal to or less than 100 microM. However, when basal, serum and cell-free RPMI 1640 was used, all compounds other than diamphenethide were highly active, their minimum lethal concentrations being some 25-125 times lower under these conditions. The inclusion of rabbit liver microsomes in the basal culture medium resulted in diamphenethide exhibiting cidal activity equivalent to that seen when its free-amine active metabolite was assayed. The possibility that the activity of many of these compounds was masked in vitro because of their serum binding properties is discussed. Recommendations are made that in vitro screens for new fasciolicides should be carried out in serum-free medium and that additional replicates containing mammalian liver microsomes and liver cytosolic extracts be included as means for the metabolic activation of certain otherwise undetectable prodrugs.

The aggregation response of Trichostrongylus colubriformis: a basis for the rapid interpretation of in vitro anthelmintic screens

An in vitro anthelmintic primary screen in which the effects of compounds on the aggregation response of newly moulted adult worms of Trichostrongylus colubriformis was monitored is described. Representatives of all the major classes of the anti-trichostrongyle anthelmintics all inhibited worm aggregation completely when present in the culture medium either at or at less than micromolar concentrations. The screen proved highly selective for these broad-spectrum agents, much higher concentrations of the narrower spectrum anthelmintics, active only against blood-sucking nematodes, trematodes and/or cestodes, having little or no effect on this response. This in vitro assay, based solely on the occurrence or absence of worm aggregation following the final moult in culture, proved very easy to interpret rapidly and accurately. It can be recommended therefore for the primary mass screening of synthetic compounds or natural products for intrinsic activity against the trichostrongylid helminths of ruminants.

Trichostrongylus colubriformis: in vitro culture of parasitic stages and their use for the evaluation of anthelmintics

Approximately 50 per cent of fourth stage larvae of Trichostrongylus colubriformis taken from the gerbil, Meriones unguiculatus, on day 8 after infection, moulted to the young adult stage when cultured in a complex medium over a seven day period in vitro. Larvae at the late fourth stage of development were highly susceptible to certain benzimidazole, prebenzimidazole, imidazothiazole, pyrimidine, quaternary ammonium, organophosphorus and macrocyclic lactone anthelmintics when any of these were included at very low concentrations in the culture medium. However, few anthelmintics lacking activity against T colubriformis in vivo affected these larvae. An assay employing these larvae in vitro should offer a means for assessing the intrinsic activity of new compounds against T colubriformis in the absence of any complicating host pharmacokinetic factors, and could also be adapted for use as a high capacity preliminary screen. Thus it should now be possible to employ a target parasite at the earliest stages of a lead discovery programme obviating the need to use less relevant free-living nematodes or ones that are natural parasites of rodents.