Previous Article |
Table of Contents
| Next Article 
Medical Sciences
Antitumor efficacy of cytotoxic drugs and the monoclonal antibody 806 is enhanced by the EGF receptor inhibitor AG1478
*Ludwig Institute for Cancer Research, Austin Hospital, Studley Road, Heidelberg 3084, Australia; Ludwig Institute for Cancer Research, Royal Melbourne Hospital, Royal Parade, Parkville 3050, Australia; and Ludwig Institute for Cancer Research, Memorial Sloan–Kettering Cancer Center, York Avenue, New York, NY 10021
Contributed by Lloyd J. Old, October 8, 2003
 |
Abstract |
|---|
 Top Abstract Materials and MethodsResultsDiscussionReferences |
|---|
Blockade of epidermal growth factor receptor (EGFR) signaling with specific inhibitors of the EGFR tyrosine kinase retards cellular proliferation and arrests the growth of tumor xenografts. AG1478, an inhibitor of the EGFR tyrosine kinase, is used in laboratory studies; however, its therapeutic potential has not been elucidated. Therefore, we evaluated an aqueous form of AG1478 for its antitumor activity in mice bearing human xenografts expressing the WT EGFR or a naturally occurring ligand-independent truncation of the EGFR [delta2–7 (de2–7) EGFR or EGFRvIII]. Parenteral administration of soluble AG1478 blocked phosphorylation of the EGFR at the tumor site and inhibited the growth of A431 xenografts that overexpress the WT EGFR and glioma xenografts expressing the de2–7 EGFR. Strikingly, even subtherapeutic doses of AG1478 significantly enhanced the efficacy of cytotoxic drugs, with the combination of AG1478 and temozolomide displaying synergistic antitumor activity against human glioma xenografts. AG1478 was also examined in combination with mAb 806, an anti-EGFR antibody that was raised against the de2–7 EGFR but unexpectedly also binds a subset of the EGFR expressed in cells exhibiting amplification of the EGFR gene. The combination of AG1478 and mAb 806 displayed additive, and in some cases synergistic, antitumor activity against tumor xenografts overexpressing the EGFR. Here, we demonstrate that different classes of inhibitors to the EGFR can have synergistic antitumor activity in vivo. These results establish the antitumor efficacy of the EGFR inhibitor AG1478 and provide a rationale for its clinical evaluation in combination with both chemotherapy and other EGFR therapeutics.
The mAb 806 (8–11) was raised against cells expressing the delta2–7 (de2–7) EGFR, a naturally occurring truncation of the EGFR commonly expressed in glioma (13). This truncation results in the removal of 267 aa from the extracellular domain of the EGFR and renders the receptor unable to bind any known ligand (14). Despite this truncation, the de2–7 EGFR displays low levels of constitutive activation and enhances the tumorgenicity of glioma and breast cells when grown as xenografts in nude mice (15, 16). Unlike other de2–7 EGFR-specific antibodies, which are all specific to the unique de2–7 EGFR junctional peptide, mAb 806 recognizes a different epitope (8, 9). Although mAb 806 recognizes a large fraction of the de2–7 EGFR, it also binds some of the WT EGFR in cells that overexpress the receptor (8, 9). Scatchard analysis has revealed that mAb 806 binds 
50% of the de2–7 EGFR recognized by mAb DH8.3, an antibody specific for the de2–7 EGFR junctional peptide. In contrast, mAb 806 bound <10% of the WT EGFR overexpressed on A431 cells when compared with the WT EGFR-specific mAb 528. Importantly, mAb 806 does not bind to normal tissue expressing the WT EGFR (8, 9). When used as a single agent, mAb 806 demonstrated significant antitumor activity against human xenografts expressing either the de2–7 or amplified EGFR (10).
In this study, we evaluated the tumor-targeting and antitumor activity of an aqueous formulation of AG1478 against a number of different EGFR-expressing xenografts grown in nude mice. We also assessed the ability of AG1478 to improve the efficacy of several chemotherapy agents including temozolomide, which is often used for the treatment of glioma (17). Finally, we used AG1478 in combination with mAb 806 to see whether disparate inhibitors against the same receptor show increased antitumor potency when used together.
|
Materials and Methods |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
2–7, which expresses recombinant de2–7 EGFR, and the squamous cell carcinoma line A431, which overexpresses the EGFR, have been described (9). HN5 is a head and neck cell line that overexpresses the EGFR (18). mAb 528, which recognizes both de2–7 and WT EGFR, has been described (9). Both mAb 528 and 806 were produced in the Biological Production Facility of the Ludwig Institute, Melbourne, Australia. Production of the tyrphostin AG1478 [4-(3-chloroanilino)-6,7-dimethoxyquinazoline] has been described (7). The AG1478-mesylate (molecular weight 411.1) was manufactured by the Institute of Drug Technology (IDT, Melbourne, Australia). Activity of the AG1478-mesylate was tested in a standard in vitro mitogenic assay by using IL-3-dependent BaF/3 cells transfected with the WT EGFR (19). For animal experiments, the AG1478 was dissolved in 100 mM Captisol (Cydex, Overland Park, KS) at the desired concentration. The concentration of AG1478 in serum and tissues was essentially performed as previously validated (20). Fluorescence-Activated Cell Sorter Analysis of EGFR Expression. Cells were incubated in serum free media overnight and then incubated with fresh media containing AG1478 or EGF for 10 or 240 min. Cells were then incubated with mAb 806 for 30 min at 4°C with bound antibody detected by using an FITC-coupled goat anti-mouse antibody (Calbiochem). Cells were analyzed on an Epics Elite ESP flow cytometer (Beckman Coulter) and analyzed by using EXPO FOR WINDOWS.
ELISA Analysis of EGFR Expression. A431 cells were incubated overnight in serum-free media and then incubated with fresh media containing AG1478 for 10 min. Cells were placed in lysis buffer (1% Triton X-100/30 mM Hepes/150 mM NaCl/500 µM 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF)/150 nM aprotinin/1 µM E-64 protease inhibitor/0.5 mM EDTA/1 µM leupeptin, pH 7.4) for 1 h at 4°C. Lysates were clarified by centrifugation and diluted with PBS, and the EGFR was assayed by ELISA as described (21).
Antiproliferative Assays. A431 and U87MG.2–7 cells were set up at a density of 2.5 x 103 cells per well in 96-well plates, allowed to adhere overnight, and then incubated with AG1478 or mAb 806 for 48 h. After 0 and 48 h, viable cell number was determined by using the MTS assay (Promega), and the percentage inhibition was calculated by the following formula: 1 - [A490 (48 h) of treated cells - A490 (0 h)]/[A490 (48 h) of control cells - A490 (0 h)] x 100.
Xenograft Models. A431 or U87MG.2–7 tumor cells were inoculated s.c. into both flanks of female BALB/c nu/nu mice. Because of differences in xenograft growth rate, mice were always inoculated with the same cells on each flank. The therapeutic efficacy of AG1478 alone or in combination was investigated in both preventative and established tumor models as described (10). Differences between treatment groups at given time points were tested for statistical significance by using Student's t test.
Immunohistochemistry of Xenografts. Xenografts were embedded in OCT compound (Sakura Finetek, Torrance, CA) and snap frozen. Sections were cut, fixed in acetone for 10 min, and stained with antibodies to the EGFR (sc-03), phosphorylated EGFR (tyrosine 1173), and phosphorylated Akt (serine 473), all purchased from Santa Cruz Biotechnology.
|
Results |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
2–7 xenografts was determined at this time point. Serum AG1478 levels were proportional to dose and consistent between mice, with a mean ± SD concentration of 23 ± 5 µM observed 30 min after a 400-µg i.p. injection and 59 ± 12 µM after a 1-mg injection (Fig. 1). The amount of AG1478 measured in the liver, skin, and xenografts was also proportional to dose 30 min after injection (Fig. 1). Analyses of tissues, including xenografts, at 24 h postinjection showed that AG1478 was no longer detectable (data not shown). The mean concentration seen in the xenografts (13 and 42 µM after a 400- and 1,000-µg dose, respectively) is sufficient to inhibit EGFR phosphorylation at both dose levels (22). Indeed, AG1478 clearly reduced the amount of phosphorylated de2–7 EGFR as assessed by immunohistochemistry (Fig. 2) 30 min after injection. Furthermore, the level of phosphorylated Akt at the plasma membrane, a downstream target of the EGFR, was also clearly reduced (Fig. 2). Interestingly, the remaining phosphorylated Akt had moved in to the nucleus at this time point (Fig. 2), possibly reflecting a survival response to the sudden switching-off of EGFR signaling. Skin samples from AG1478-treated mice stimulated ex vivo with EGF displayed reduced phosphorylation of the murine EGFR in response to ligand, confirming that AG1478 in skin (Fig. 1) is active (data not shown).
|
|
Treatment of Xenografts with AG1478. Mice with either A431 or U87MG.2–7 xenografts were treated i.p. three times per week for 2 weeks with escalating doses of AG1478 in a preventative model to determine its efficacy as a single agent (Fig. 3). AG1478 significantly inhibited the growth of A431 xenografts at the 400-µg (P < 0.01) and the 1,000-µg (P < 0.0001) injection level in a dose-dependent manner (Fig. 3A). Mean tumor volume 13 days after inoculation was 760, 670, 590, and 320 mm3 for the vehicle and 200-, 400-, and 1,000-µg groups, respectively. AG1478 significantly inhibited the growth of U87MG.2–7 xenografts only at the 1,000-µg dose (P < 0.05) (Fig. 3B), suggesting that it may be more difficult to inhibit tumors expressing the constitutively active de2–7 EGFR. Weight loss (10%) was observed in mice that received 1,000 µg of AG1478 whereas no weight loss was noted at lower doses.
|
Treatment of Xenografts with AG1478 and Cisplatin in Combination. We examined whether aqueous AG1478 could potentiate the antitumor activity of cytotoxic drugs. To observe genuine enhancement of efficacy, these studies were performed by using doses of AG1478 and cisplatin that were relatively ineffective as a single agent (Fig. 4). Three coinjections of cisplatin and AG1478 given every second day displayed significantly higher antitumor activity against established U87MG.2–7 and A431 xenografts than either agent used alone (Fig. 4). With respect to the U87MG.2–7 xenografts, the combination of AG1478 and cisplatin caused significant inhibition of xenograft growth when compared with the vehicle (P < 0.01), the AG1478 alone (P < 0.01), or cisplatin alone (P < 0.002) treatment group at day 22 post tumor inoculation. At this time, the mean tumor volume was 1,420, 1,240, 1,290, and 700 mm3 for the vehicle, AG1478, cisplatin, and combination groups, respectively (Fig. 4A). The combination of AG1478 and cisplatin also caused significantly higher inhibition of A431 xenografts when compared with vehicle (P < 0.001), the AG1478 alone (P < 0.02), or cisplatin alone (P < 0.02) treatment group at day 16 (Fig. 4B). Some weight loss (10–15%) was observed in the combination treatment groups. Thus, the combination of AG1478 and cisplatin had significant antitumor activity at doses that were ineffective when either agent was used alone.
|
Treatment of U87MG.2–7 Xenografts with AG1478 and Temozolomide in Combination. Because temozolomide has been shown to have efficacy in advanced glioblastoma, we investigated whether AG1478 enhanced its efficacy against U87MG.2–7 human glioma xenografts. The combination of AG1478 and temozolomide caused significant inhibition of tumor growth compared with vehicle control (P < 0.005), AG1478 alone (P < 0.005), and temozolomide alone (P < 0.005) treatment groups at day 22 post tumor inoculation (Fig. 5A) when coinjected three times every second day. At day 22 post tumor inoculation, the mean tumor volume was 1,420, 1,240, 1,230, and 570 mm3 for the vehicle, AG1478, temozolomide, and combination groups, respectively (Fig. 5A). Thus, the combination of AG1478 and temozolomide had significant antitumor activity at doses that were ineffective when either agent was used alone. A second experiment using a higher dose of temozolomide (5 mg/kg vs. 2.5 mg/kg) and a different dose schedule (temozolomide once per week and AG1478 three times per week for 2 weeks) was performed to optimize the antitumor effect of the combination therapy (Fig. 5B). Although AG1478 had no efficacy as a single agent, it clearly displayed synergistic antitumor activity when used in combination with temozolomide (P < 0.0001 for combination therapy compared with temozolomide alone), leading to an 80% reduction in xenograft growth (Fig. 5B). The combination of AG1478 and temozolomide together did not produce any weight loss.
|
Treatment of Xenografts with a Combination of AG1478 and mAb 806 in Preventative Models. Given the differences in mode and site of action between antibodies and TKIs, we decided to examine whether the combination of AG1478 and EGFR antibody mAb 806 has enhanced antitumor activity. Although suboptimal doses of both AG1478 and mAb 806 inhibited the growth of A431 xenografts in a preventative model when used alone, the combination of both agents displayed synergistic antitumor activity (Fig. 6A). At day 20 post tumor inoculation, the A431 xenografts treated with both agents had a mean volume of 200 mm3, significantly lower than vehicle (1,260 mm3, P < 0.0001), the AG1478 alone (1,080 mm3, P < 0.0001), and mAb 806 alone (740 mm3, P < 0.002) groups. Furthermore, although the take rate of xenografts was 100% in the vehicle and single agent groups, only 60% of tumors successfully established in the group treated with both AG1478 and mAb 806. In contrast to A431 tumors, treatment of U87MG.2–7 xenografts with AG1478 and mAb 806 in combination was no more effective than mAb 806 alone (Fig. 6B).
|
Treatment of Established Xenografts with a Combination of AG1478 and mAb 806. The efficacy of the combination EGFR therapy was also tested against established A431 or U87MG.2–7 xenografts. When used as a single agent at this dose, AG1478 had no effect on the growth of A431 xenografts whereas mAb 806 caused slight inhibition (P < 0.03) (Fig. 7A). In contrast, the combination of AG1478 and mAb 806 produced significant growth inhibition that was greater than additive. At day 19 post tumor inoculation, the A431 xenografts treated with both agents had a mean volume of 740 mm3, which was significantly smaller than vehicle control (1,290 mm3, P < 0.0001), AG1478 alone (1,240 mm3, P < 0.002), and mAb 806 alone (1,060 mm3, P < 0.001) treatment groups (Fig. 7A). As in the preventative model, treatment of U87MG.2–7 xenografts with AG1478 and mAb 806 in combination was no more effective than mAb 806 alone (Fig. 7B). We extended our studies by treating HN5 xenograft bearing mice with a combination of AG1478 and mAb 806. Treatment of established HN5 xenografts with AG1478 and mAb 806 as single agents had no effect on tumor growth at the doses used (Fig. 7C). In comparison, the combination of these agents virtually abrogated the growth of HN5 xenografts (P < 0.0001, 0.002, and 0.0001 compared with vehicle, AG1478 alone, and mAb 806 alone, respectively) and actually induced tumor regression between day 17 and 22 post inoculation, indicative of a synergistic antitumor effect (Fig. 7C). No weight loss was observed in any of the treatment groups.
|
In Vitro Studies with AG1478 and mAb 806. We compared the in vitro anti-proliferative effects of AG1478 and mAb 806 on A431 and U87MG.2–7 cells. AG1478 was able to inhibit the proliferation of both cells lines even in the presence of 10% FCS (P < 0.0001 in both cases) (Fig. 8A). In contrast, mAb 806 had minimal effect on the proliferation of A431 and U87MG.2–7 cells grown in 10% FCS (data not shown) or 0.5% FCS (Fig. 8A), even though the concentration used exceeded that which can be achieved at the tumor site in vivo. Furthermore, the combination of AG1478 and mAb 806 had no greater in vitro efficacy than AG1478 alone (Fig. 8A). This result indicates that these EGFR therapeutics have different modes of action and that the antitumor activity of mAb 806 is observed only in vivo.
|
Because mAb 806 binds only 5–10% of the EGFR on the surface of A431 cells, we examined whether AG1478 increased the level of mAb 806 reactivity. By using a quantitative ELISA to measure total cellular EGFR, it was apparent that even a 10-min exposure to 0.5 or 5 µM AG1478 increases the level of mAb 806 reactivity in a dose-dependent manner (Fig. 8B). The level of mAb 528 reactivity also increased but was more modest in percentage terms. We sought to confirm that mAb 806 reactivity was also increased on the cell surface. To achieve this result, we compared the binding of mAb 806 to U87MG.2–7 and U87MG.wtEGFR cells after AG1478 treatment. The U87MG.wtEGFR cells overexpress the EGFR and were used because they could be directly compared with the U87MG.2–7 cells. Treatment with 2 µM AG1478 modestly, but reproducibly, increased the surface binding of mAb 806 to U87MG.wtEGFR cells at 10 and 240 min (Table 1). In comparison, AG1478 treatment under identical conditions actually reduced binding of mAb 806 to the surface of U87MG.2–7 (Table 1). Treatment of cells with 100 ng/ml of EGF, which induces EGFR down-regulation, caused a reduction of mAb 806 reactivity as expected.
|
|
Discussion |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
-cyclodextrin (Captisol), has significant antitumor activity. Currently, all TKIs undergoing clinical evaluation have been administered via the oral route (4). The oral route was chosen for its ease of administration and capacity to generate sustained serum levels, an outcome considered desirable because it results in the extended inhibition of the EGFR. Despite the advantages of oral administration, the potential benefits of i.v. delivery, which is how our soluble AG1478 would be administered, should be considered. One outcome of i.v. administration would be the ability to obtain higher local concentrations of AG1478 at the tumor site compared with the oral route. Because EGFR signaling can be initiated from a relatively small number of receptors (23), it may be necessary to inhibit a large proportion of the receptors to obtain a complete abrogation of signaling, something more achievable with the i.v route because of the higher concentration of TKI at the tumor site. Furthermore, the brief but repetitive inactivation of the EGFR that would result from i.v. administration may have greater and/or different antitumor effects. Indeed, it has been shown that the brief inactivation of MYC in osteogenic sarcoma cells causes tumor regression, with the subsequent reactivation of MYC inducing apoptosis in the surviving tumor cells (24). Given these considerations and the antitumor activity seen in our animal models, we intend to explore the clinical efficacy of AG1478 after i.v. administration.
High levels of AG1478-mesylate were detected in tumors 30 min after injection, resulting in complete abrogation of EGFR phosphorylation and growth inhibition of A431 xenografts. The antitumor effect against A431 xenografts is smaller than previous TKIs because we used less frequent administration to identify a dose schedule suitable for use with chemotherapy. In contrast to A431 xenografts, AG1478 only slightly inhibited the growth of U87MG.2–7 xenografts at the highest dose. Although the relative resistance of U87MG.2–7 xenografts to AG1478 may simply reflect intrinsic differences in sensitivity between cell lines, we have previously shown that de2–7 EGFR expressing U87MG xenografts are more resistant to AG1478 than U87MG cells overexpressing the WT EGFR (25). This comparative resistance of de2–7 EGFR expressing xenografts to AG1478 was not seen in vitro (Fig. 8), suggesting that some aspects of the enhanced in vivo tumorgenicity mediated by the de2–7 EGFR is not inhibited by AG1478. Indeed, a recent report (26) demonstrated that, in contrast to cells expressing the WT EGFR, the EGFR-specific TKI Iressa was ineffective against intracranial xenografts expressing the de2–7 EGFR.
Two recent reports demonstrated that Iressa enhances the antitumor activity of several cytotoxic agents against a range of tumors (27, 28). These experiments were done using doses of Iressa and the cytotoxic drug that produced significant tumor inhibition when used as single agents. In contrast, we treated established A431 and U87MG.2–7 xenografts with doses of AG1478 and cisplatin that were essentially ineffective as single agents but in combination had a significant antitumor effect. This result demonstrates that, even in the absence of direct antitumor activity, AG1478 can sensitize cells to subsequent treatment with cytotoxic drugs. The combination of AG1478 and temozolomide also significantly inhibited growth of human glioma xenografts, even when used at doses that were refractory as single agents. This report demonstrates that EGFR inhibition enhances the efficacy of temozolomide and provides a strong basis for using AG1478 and temozolomide in combination for the treatment of glioma. Indeed, a recent abstract¶ showed that patients receiving the EGFR inhibitor OSI-774 in combination with temozolomide displayed a low level of clinical response.
A further significant finding in this paper is the observation that AG1478 and mAb 806 in combination had additive and, in the case of HN5, synergistic antitumor activity against xenografts expressing the WT EGFR. Here, we demonstrate that different classes of inhibitor directed to the EGFR can lead to enhanced antitumor activity in vivo in multiple cell lines. A previous study (29) demonstrated that the combination of an EGFR-specific TKI and antibody (i.e., PD153035 and C225) did have an additive antiproliferative effect, but this finding was performed only in vitro against a single cell line. The mAb 806 antibody recognizes only a proportion of the WT EGFR expressed on the surface of tumor cell lines such as A431 and HN5 (8–10). Treatment of cells with AG1478 increased the level of mAb 806 reactivity on the surface of these cell lines. This result is consistent with previous studies (30, 31) that have demonstrated that AG1478 and other TKIs increase the total level of EGFR on the cell surface by reducing receptor internalization. Addition of AG1478 also induces the EGFR to assume an inactive dimer configuration (30); thus, it is possible that mAb 806 preferentially recognizes this conformation of the EGFR. AG1478 did not improve the efficacy of mAb 806 against a de2–7 EGFR-expressing xenograft, further emphasizing that the de2–7 EGFR responds to EGFR inhibitors in a manner different from the WT EGFR. Improved binding of mAb 806 to tumor cells may not be the only mechanism leading to enhanced antitumor activity when AG1478 and mAb 806 are used in combination. It is likely that these two EGFR inhibitors mediate their antitumor action through independent mechanisms although they target the same receptor. Thus, when used in combination, each inhibitor would suppress unique aspects of EGFR signaling and function, leading to the additive or synergistic antitumor activity. The mechanism by which mAb 806 inhibits xenograft growth has only been partially elucidated, largely because it has no antiproliferative or proapoptotic activity in any in vitro system. However, the in vivo antitumor activity of mAb 806 is not mediated by immune effector function (T.G.J, unpublished data) although it does have some antiangiogenic properties, which may partially explain its in vivo activity (9–11).
In conclusion, we have demonstrated that parenteral administration of soluble AG1478 has significant antitumor activity as a single agent, even though this approach only transiently exposes the xenograft to AG1478. Furthermore, nontherapeutic doses of AG1478 significantly enhanced the cytotoxicity of both cisplatin and temozolomide, providing a rationale for the use of AG1478 in glioma patients being treated with temozolomide. Finally, we ascertained that disparate inhibitors to the EGFR can produce synergistic antitumor activities. Overall, these studies provide an impetus for using soluble AG1478 in combination with chemotherapy or mAb 806 in the treatment of patients with EGFR-positive tumors.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
¶ Prados, M., Chang, S., Burton, E., Kapadia, A., Rabbitt, J., Page, M., Federoff, A., Kelly, S. & Fyfe, G. (2003) Proc. Am. Soc. Clin. Oncol. 22, 99, abstr. 394. 
To whom correspondence should be addressed. E-mail: terry.johns{at}ludwig.edu.au.
|
References |
|---|
|
TopAbstractMaterials and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg What's this?
This article has been cited by other articles in HighWire Press-hosted journals:
|
|
 |
|
  J. Huang, J. Hu, X. Bian, K. Chen, W. Gong, N. M. Dunlop, O.M. Z. Howard, and J. M. Wang Transactivation of the Epidermal Growth Factor Receptor by Formylpeptide Receptor Exacerbates the Malignant Behavior of Human Glioblastoma Cells Cancer Res., June 15, 2007; 67(12): 5906 - 5913. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. G. Johns, R. M. Perera, S. C. Vernes, A. A. Vitali, D. X. Cao, W. K. Cavenee, A. M. Scott, and F. B. Furnari The Efficacy of Epidermal Growth Factor Receptor-Specific Antibodies against Glioma Xenografts Is Influenced by Receptor Levels, Activation Status, and Heterodimerization Clin. Cancer Res., March 15, 2007; 13(6): 1911 - 1925. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. M. Scott, F.-T. Lee, N. Tebbutt, R. Herbertson, S. S. Gill, Z. Liu, E. Skrinos, C. Murone, T. H. Saunder, B. Chappell, et al. A phase I clinical trial with monoclonal antibody ch806 targeting transitional state and mutant epidermal growth factor receptors PNAS, March 6, 2007; 104(10): 4071 - 4076. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. K. Gan, F. Walker, A. W. Burgess, A. Rigopoulos, A. M. Scott, and T. G. Johns The Epidermal Growth Factor Receptor (EGFR) Tyrosine Kinase Inhibitor AG1478 Increases the Formation of Inactive Untethered EGFR Dimers: IMPLICATIONS FOR COMBINATION THERAPY WITH MONOCLONAL ANTIBODY 806 J. Biol. Chem., February 2, 2007; 282(5): 2840 - 2850. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. T. Lee, A. J. Mountain, M. P. Kelly, C. Hall, A. Rigopoulos, T. G. Johns, F. E. Smyth, M. W. Brechbiel, E. C. Nice, A. W. Burgess, et al. Enhanced Efficacy of Radioimmunotherapy with 90Y-CHX-A''-DTPA-hu3S193 by Inhibition of Epidermal Growth Factor Receptor (EGFR) Signaling with EGFR Tyrosine Kinase Inhibitor AG1478 Clin. Cancer Res., October 1, 2005; 11(19): 7080s - 7086s. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. M. Perera, Y. Narita, F. B. Furnari, H. K. Gan, C. Murone, M. Ahlkvist, R. B. Luwor, A. W. Burgess, E. Stockert, A. A. Jungbluth, et al. Treatment of Human Tumor Xenografts with Monoclonal Antibody 806 in Combination with a Prototypical Epidermal Growth Factor Receptor-Specific Antibody Generates Enhanced Antitumor Activity Clin. Cancer Res., September 1, 2005; 11(17): 6390 - 6399. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Zhou and M. G. Brattain Synergy of Epidermal Growth Factor Receptor Kinase Inhibitor AG1478 and ErbB2 Kinase Inhibitor AG879 in Human Colon Carcinoma Cells Is Associated with Induction of Apoptosis Cancer Res., July 1, 2005; 65(13): 5848 - 5856. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. R. Stewart and C. A. O'Brian Protein kinase C-{alpha} mediates epidermal growth factor receptor transactivation in human prostate cancer cells Mol. Cancer Ther., May 1, 2005; 4(5): 726 - 732. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Carter, L. Smith, and M. Ryan Identification and validation of cell surface antigens for antibody targeting in oncology Endocr. Relat. Cancer, December 1, 2004; 11(4): 659 - 687. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. G. Johns, T. E. Adams, J. R. Cochran, N. E Hall, P. A. Hoyne, M. J. Olsen, Y.-S. Kim, J. Rothacker, E. C. Nice, F. Walker, et al. Identification of the Epitope for the Epidermal Growth Factor Receptor-specific Monoclonal Antibody 806 Reveals That It Preferentially Recognizes an Untethered Form of the Receptor J. Biol. Chem., July 16, 2004; 279(29): 30375 - 30384. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Walker, S. G. Orchard, R. N. Jorissen, N. E. Hall, H.-H. Zhang, P. A. Hoyne, T. E. Adams, T. G. Johns, C. Ward, T. P. J. Garrett, et al. CR1/CR2 Interactions Modulate the Functions of the Cell Surface Epidermal Growth Factor Receptor J. Biol. Chem., May 21, 2004; 279(21): 22387 - 22398. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
