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Pharmacodynamic Studies of Gefitinib in Tumor Biopsy Specimens From Patients With Advanced Gastric Carcinoma

Federico Rojo, Josep Tabernero, Joan Albanell, Eric Van Cutsem, Atsushi Ohtsu, Toshihiko Doi, Wasaburo Koizumi, Kuniaki Shirao, Hiroya Takiuchi, S. Ramon Cajal, José Baselga

From the Medical Oncology Service, Vall d'Hebron University Hospital, Barcelona, Spain; the University Hospital Gasthuisberg, Leuven, Belgium; the National Cancer Center Hospital E, Chiba; the Kitasato University E Hospital, Kanagawa; the National Cancer Centre Hospital, Tokyo; and the Osaka Medical College, Osaka, Japan.

Address reprint requests to José Baselga, MD, Medical Oncology Service, Vall d'Hebron University Hospital, P. Vall d'Hebron 119-129, 08035 Barcelona, Spain; e-mail: jbaselga{at}vhebron.net

	ABSTRACT

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Purpose Epidermal growth factor receptor (EGFR) is highly expressed in some gastric cancers and is implicated in cancer cell growth and proliferation. The objective of this study was to assess the in situ biologic activity of the EGFR tyrosine kinase inhibitor gefitinib in gastric tumor samples in a phase II study.

Methods Patients with previously treated stage IV adenocarcinoma of the stomach or gastroesophageal junction were randomly assigned to receive gefitinib (250 or 500 mg/d). Tumor biopsies, obtained at screening and on day 28 of treatment, were assessed for biomarker expression using immunohistochemistry and analysis of apoptosis.

Results One hundred sixteen tumor samples from 70 patients were available, 70 were baseline and 46 were on-therapy biopsies. At baseline, levels of EGFR expression significantly correlated with levels of phosphorylated EGFR (pEGFR; P < .001) and Ki67 expression (P = .011), but not with phosphorylated mitogen-activated protein kinase (pMAPK). After gefitinib treatment, levels of pEGFR in tumor cells were significantly reduced (P = .001); this was not the case for pMAPK and phosphorylated Akt (pAkt). However, in some cases gefitinib inhibited pAkt and these tumors had enhanced apoptosis. Likewise, there was a significant correlation between increased exposure to geftinib and enhanced apoptosis.

Conclusion Gefitinib reached the tumors at concentrations sufficient to inhibit EGFR activation in advanced gastric carcinoma patients, although this did not translate into clinical benefit. Overall, intratumoral phosphorylation of MAPK and Akt was not significantly inhibited by gefitinib. However, the finding that decreases in pAkt correlated with enhanced apoptosis deserves further exploration.

	INTRODUCTION

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Gastric cancer is one of the most common causes of cancer deaths—worldwide it is second only to lung cancer.¹ Prognosis for patients with advanced stomach cancer is poor; the 5-year survival rate for patients with localized disease is approximately 60%, whereas for those with distant disease it is only 2%.² Therefore, there is clearly a need for new therapeutic approaches, among them the development of agents against molecular targets.³

Epidermal growth factor receptor (EGFR) is a member of the ErbB family of receptors—a family of receptors that plays a major role in promoting proliferation and the malignant growth of a variety of epithelial tumors (see review in Yarden and Sliwkowski⁴). EGFR is highly expressed in approximately one third of advanced-stage gastric cancers⁵ and has been shown to be a modest prognostic indicator.⁶ Recently, agents targeting the EGFR have been shown to have meaningful clinical activity in a variety of tumor types (see review in Baselga and Arteaga⁷).

In order to study the effects of anti-EGFR therapy in patients with advanced gastric cancer, we conducted the current phase II study with gefitinib (Iressa; AstraZeneca, Macclesfield, Cheshire, United Kingdom), an orally active EGFR tyrosine kinase inhibitor that blocks receptor-dependent signal transduction and that shown to be active in patients with non–small-cell lung cancer.⁸ Our aim was to determine the antitumor activity of gefitinib in patients with advanced gastric cancer and to study the effects of gefitinib on EGFR phosphorylation and on the two major receptor signaling pathways, the mitogen-activated protein kinase (MAPK) pathway and the phosphatidlyl-inositol-3-kinase (PI3K)/Akt pathway, as well as its effects on proliferation and apoptosis.

In the first phase II study of gefitinib in patients with advanced gastric cancer, gefitinib was well tolerated and demonstrated modest clinical activity with disease control rates of 13.9% and 22.9% at 250 mg/d and 500 mg/d, respectively.⁹ The clinical results will be reported elsewhere (Van Cutsem et al, manuscript in preparation). Results from the sequential tumor biopsy study to study the effects of gefitinib on EGFR signaling are reported in this article.

	METHODS

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Study Design
This was a randomized, double-blind, parallel-group, multicenter, two-stage, phase II study. The exploratory objectives of this study were to investigate the pharmacodynamic parameters at steady state and to evaluate whether EGFR expression correlates with the antitumor activity of gefitinib.

Patients
Eligible patients had histologically confirmed stage IV adenocarcinoma of the stomach or gastroesophageal junction and had failed one or two prior chemotherapy regimens. In addition, patients were required to have at least one measurable lesion as defined in Response Evaluation Criteria in Solid Tumors, a WHO performance status of 0 to 2, life expectancy of 12 weeks or longer, the ability to ingest food, and to be age 18 years or older. Patients who had received more than two previous chemotherapy treatments or who had their last anticancer therapy within 21 days of the start of gefitinib treatment were excluded.

All eligible patients had to provide written informed consent and the study was conducted in accordance with good clinical practice guidelines and the Declaration of Helsinki.

Treatment
Treatment was divided into four strata: two ethnic groups of patients (Japanese and non-Japanese) randomly assigned to receive gefitinib at either 250 mg/d or 500 mg/d as an oral dose. Patients continued with their assigned dose until disease progression and any patient showing evidence of response could continue with therapy outside of the core treatment period into an extension period.

Pharmacokinetic Analysis
Venous blood samples for pharmacokinetic analysis were taken at screening, pregefitinib treatment, and at 1 hour, 3 hours, 5 hours, 7 hours, 12 hours, and 24 hours postgefitinib treatment on day 28 of treatment period 1. Complete pharmacokinetic data were available from 44 treated patients. In addition, a pregefitinib treatment sample was also taken on day 28 of each subsequent treatment period. Plasma was isolated from blood samples by centrifugation (10 minutes at 1,000 g) and was analyzed using high-performance liquid chromatography with tandem mass spectrometric detection. The C_max and t_max values for each patient were derived from the plasma concentration-time profile and the area under the time-concentration curve (AUC) _(0-24) was calculated using the linear trapezoidal rule.

Biopsy Samples
Tumor biopsies were obtained at screening (pregefitinib treatment), on day 28 of treatment, and, if possible, at disease progression. Fresh tissue samples were collected from either the primary tumor or from metastatic sites. As much tissue as possible was collected, such that the total sample volume was at least 3 x 3 x 3 mm. For endoscopic biopsies, eight to 10 samples of 1 x 1 mm were allowed. Biopsies from liver metastases were taken using a computed tomography scan-guided 18 G core needle. All samples were fixed immediately after removal in a 10% buffered formalin solution for a maximum of 48 hours at room temperature before being dehydrated and paraffin embedded under vacuum. To allow comparative biomarker studies, subsequent biopsies were taken from the same site as the screening biopsy.

Antibodies
The following antibodies were used for the detection of pharmacodynamic markers: anti-EGFR (mouse monoclonal antibody [MAb] clone 2-18C9), anti-Ki67 (mouse MAb clone MIB1), and antip27^kip1 (mouse MAb clone SX53G8) were obtained from DAKO (Carpinteria, CA), antiphosphorylated EGFR (pEGFR; mouse MAb clone 74) was obtained from Chemicon (Temecula, CA), anti-TGF- (mouse MAb clone Ab-2) was obtained from Oncogene (San Diego, CA), antiphosphorylated p42/44 MAPK (pMAPK; rabbit polyclonal phosphorylated-p44/42 MAPK at Thr202/Tyr204) and antiphosphorylated Akt (pAkt; rabbit polyclonal phosphorylated-Akt at Ser473) were obtained from Cell Signaling Technology (Beverly, MA).

Immunohistochemistry
Immunostaining was performed on 4 µm tissue sections mounted onto positively charged glass slides. After removal of paraffin in xylene and graded alcohols, sections were hydrated. Epitope retrieval was performed when necessary in 10 mmol/L EDTA buffer, pH 8 for 10 minutes in a pressure cooker (pEGFR, pMAPK, pAkt, Ki67, and p27^kip1) or using proteinase K digestion for 5 minutes (EGFR) at room temperature. Tumor necrosis factor alpha (TNF-) did not require antigen retrieval. After target retrieval, endogenous peroxidase was blocked by immersing the sections in .03% hydrogen peroxide for 5 minutes. Incubation with primary antibodies was performed at room temperature for 1 hour using the following dilutions: EGFR 1:1, pEGFR 1:500, TGF- 1:100, pMAPK 1:80, pAkt 1:50, Ki67 1:100, and p27^kip1 1:100. Peroxidase-conjugated goat antirabbit (pMAPK and pAkt) or antimouse (EGFR, TGF-, Ki67, and p27^kip1) were used to detect antigen-antibody reaction (En Vision+ System; DAKO) for 30 minutes at room temperature. For pEGFR, an enhanced signal amplification method (CSA; DAKO) was used as described in the manufacturer's guidelines. Sections were visualized with 3,3'-diaminobenzidine as a chromogen for 5 minutes and counterstained with Mayer's hematoxylin. Positive and negative controls were included in each experiment.

To score a tumor cell as positive, membrane staining was required for total EGFR, membrane or cytoplasmic staining for pEGFR, cytoplasmic staining for TGF-, cytoplasmic and nuclear staining for pAkt, and nuclear staining for pMAPK, Ki67, and p27^kip1. Samples were assessed blind by investigators (F.R. and J.A.). For quantitative analysis, the percentage of stained tumor cells with each antibody in representative sections in 10 high power fields (x400) was used to calculate the average percentage of cells staining in every sample. A tumor was considered as positive with at least 1% of stained cells. Scoring was performed blind to clinical data (F.R.) and was used for statistical analysis.

Terminal Deoxynucleotide Transferase-Mediated dUTP Nick End Labeling Assay
Determination of apoptosis was measured by TUNEL (Terminal deoxynucleotide transferase [TdT]-mediated dUTP Nick End Labeling) assay on tissue sections using fluorescein-labeled 12-dUTP-TdT (Roche Diagnostics GmbH, Mannheim, Germany) after proteinase K digestion of the tissue. The apoptotic index was expressed as a percentage calculated from the number of green fluorescent cells in 10 high-power fields of the tumor tissue (x400 optical magnification) using a fuorescence Elipse E400 Nikon microscope (Nikon, Kanagawa, Japan). Absolute differences between apoptotic index in pre- and on-therapy samples were calculated.

Statistical Methods
Statistical analyses were carried out using the SPSS data analysis program, version 10.0 (SPSS Inc, Chicago, IL). The Spearman's correlation test was used to analyze statistical significance of continuous variables. Mann-Whitney U test was used to compare group means. Paired pre- and on-therapy samples were analyzed using the Wilcoxon signed rank test and Pearson ². Significance was exclusively calculated on paired biopsies with pretherapy expression higher than 0. All statistical tests were conducted at the two sided .05 level of significance.

	RESULTS

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Patients and Biopsies
In total, 75 patients were randomly assigned to receive gefitinib. Of these patients, 37 received gefitinib 250 mg/d and 38 received gefitinib 500 mg/d. Patient demographics are summarized in Table 1. From this population, 105 tumor samples were available from 70 patients (Table 2) and of these samples, 70 were baseline tumor biopsies and 35 were on-therapy biopsies. From these samples, 67 baseline tumor biopsies and 32 sequential paired biopsies (baseline and on-therapy) were of sufficient quality for immunohistochemistry assays. The baseline tumor characteristics (tumor biomarker, location, and type) are presented in Table 3. The majority of tumor samples were obtained from the stomach (77.2%) compared with the gastroesophageal junction (21.4%). EGFR expression was detected in 41 baseline tumor biopsies (58.6%). pEGFR was observed in the same areas of tumor as EGFR expression. pMAPK expression was also mainly located in the infiltrating borders of the tumors. In samples that included gastric mucosa, EGFR, pMAPK, and pAkt were expressed in differentiated cells, as expected, while Ki67 was located in the proliferating intermediate area of gastric glands. pAkt, Ki67, p27^kip1, and TGF- were diffusely expressed in tumors. However, the expression of pAkt appeared more intense in well differentiated areas of tumors.

View larger version (17K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 1. Baseline correlation in biomarker expression (epidermal growth factor receptor [EGFR] v phosphorylated EGFR [pEGFR]; EGFR v phosphorylated mitogen-activated protein kinase [pMAPK]; EGFR v Ki67; Ki67 v pMAPK). Significant correlations were calculated using Pearson's correlation test for EGFR versus pEGFR (P < .001), EGFR versus Ki67 (P = .011), and Ki67 versus pMAPK (P = .01).

View larger version (91K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 2. Basal and on-therapy levels of (A) phosphorylated epidermal growth factor receptor (pEGFR); (B) phosphorylated mitogen-activated protein kinase (pMAPK); (C) phosphorylated Akt (pAkt); and (D) Ki67. For each marker a representative case is shown in addition to the full analysis. Boxes show median and range percentage cell stained and Wilcoxon signed rank test was calculated for paired pre- and post-therapy samples.

View larger version (22K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 3. Positive correlation between decrease in phosphorylated Akt (pAkt) levels after gefitinib administration and tumor apoptotic index. (A) Overall correlation. (B) Individual patient display of the absolute values for pAkt inhibition and apoptosis index after gefitinib therapy. In the shadowed square the cases with increased apoptosis and pAkt reduction (five patients) are shown.

We also found a significant correlation between increased exposure to gefitinib and enhanced apoptosis. In those patients with assessable tumor samples for apoptotic index and pharmacokinetic assessments, there was a strong correlation between a positive apoptotic index average and enhanced gefitinib concentration, calculated as C_max (P < .001), and total exposure, calculated as AUC_(0-24) (P < .001; Fig 4). No statistical differences in apoptosis and pharmacokinetic parameters were detected between Japanese and non-Japanese population, and between sex, age, and patients with disease control versus those with progression of the disease.

View larger version (14K): [in this window] [in a new window] [PowerPoint Slide for Teaching]   Fig 4. Correlation between pharmacokinetic parameters and apoptosis. (A) An average of apoptotic index between pre- and post-therapy samples was correlated with maximum concentration (Cmax) and area under the time-concentration curve (AUC)(0-24) (B) Two representative patients are shown. Increased apoptosis is observed in patient A after gefitinib treatment in contrast with patient B. Higher gefitinib concentration and total exposure was demonstrated in patient A.

	DISCUSSION

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Gefitinib demonstrated activity against its target, the EGFR; in these gastric tumors, resulting in a complete and statistically significant inhibition of EGFR phosphorylation in tumors. However, inhibition of EGFR phosphorylation was not accompanied by significant inhibition of MAPK and Akt activation as measured by their phosphorylation status. However, there were hints of biologic effects of EGFR inhibition in some tumors. For example, the proliferation marker Ki67 was significantly inhibited in EGFR-positive tumors treated with gefitinib and this inhibition in proliferation correlated with a significant reduction in the activation of MAPK. Likewise, those patients who had a decrease in pAkt had enhanced apoptosis in comparison with tumors without change in pAkt. This is an indication that gefitinib may inhibit tumor proliferation and/or induce apoptosis within a subgroup of EGFR-sensitive patients; however, the insensitive patients may result in a dilution of any observable benefit.¹⁰ One might speculate the reasons underlying the lack of Akt inhibition in the majority of tumors. Activation of PI3K/Akt is also mediated via ErbB2 through trans-activation and phosphorylation of ErbB3.¹¹ ErbB2 is highly expressed in 8% to 40% of gastric cancers, depending on disease stage, and ErbB3 is highly expressed in 72% to 86% of advanced gastric carcinomas.⁵ However, some studies have shown that gefitinib does prevent EGFR and ErbB2-mediated activation of ErbB3.^12,13 Alternative mechanisms of Akt activation, independent of ErbB receptors, may be at play in gastric cancer, including loss of activity of the tumor suppressor gene PTEN that results in enhanced PI3K-Akt activity and resistance to EGFR inhibitors.¹⁴ In gastric cancer, evidence suggests that a reduction in PTEN expression contributes to the malignant transformation of the gastric mucosa.^15,16 This ErbbB-independent Akt activation may be therapeutically exploitable.¹⁷ Our findings would support a combined anti-EGFR and anti-PI3Kinase approach as these agents become available for clinical testing.

Other pharmacodynamic studies of gefitinib have been performed in skin biopsy samples¹⁸ and in tumor biopsies from patients with advanced breast cancer¹⁹ and colorectal cancer.²⁰ The results from skin biopsy analysis described an abolition of EGFR and most of EGFR downstream signaling pathways.¹⁸ The pharmacodynamic study of gefitinib in breast cancer demonstrated an almost total loss of EGFR phosphorylation and a decrease in MAPK phosphorylation after gefitinib treatment. Clinical disease stabilization was observed in some patients. Furthermore, a reduction in Ki67 expression levels was observed only in tumors with low pAkt levels,¹⁹ suggesting elements of the PI3K pathway may be involved in resistance to gefitinib therapy and this may, in part, explain the results presented herein. In colorectal carcinoma, a recent study with gefitinib has reported lack of inhibition of EGFR.²⁰ However, other studies with anti-EGFR agents have been reported to inhibit EGFR activation in patients with advanced colon cancer.^21,22 Therefore, there is mounting evidence that EGFR inhibition in the tumor is achieved in the different tumor types, although clinical responses and downstream signaling inhibition may depend on EGFR sensitivity of a given tumor type.

In conclusion, in this first study using sequential biopsies from patients with advanced gastric cancer, gefitinib demonstrated biologic activity to effectively inhibit EGFR activation. Gefitinib had modest clinical efficacy as well as limited effects on EGFR downstream signaling pathways. However, a subpopulation of gastric tumors have evidence of EGFR sensitivity, as demonstrated by decrease in proliferation and increased apoptosis, which warrants further study.

	Authors' Disclosures of Potential Conflicts of Interest

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Although all authors completed the disclosure declaration, the following authors or their immediate family members indicated a financial interest. No conflict exists for drugs or devices used in a study if they are not being evaluated as part of the investigation. For a detailed description of the disclosure categories, or for more information about ASCO’s conflict of interest policy, please refer to the Author Disclosure Declaration and the Disclosures of Potential Conflicts of Interest section in Information for Contributors.

Authors Employment Leadership Consultant Stock Honoraria Research Funds Testimony Other Wasaburo Koizumi Astra Zeneca (A) Hiroya Takiuchi Eli Lilly (A) José Baselga Astra Zeneca (A); Roche (A); Merck KgGA (A) Merck KgGA (A) Astra Zeneca (B)

Dollar Amount Codes (A) < $10,000 (B) $10,000-$99,900 (C) $100,000 (N/R) Not Required

	Author Contributions

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Conception and design: Federico Rojo, Josep Tabernero, Joan Albanell, Eric Van Cutsem, Atsushi Ohtsu, Toshihiko Doi, Wasaburo Koizumi, Kuniaki Shirao, Hiroya Takiuchi, José Baselga Administrative support: Wasaburo Koizumi, José Baselga Provision of study materials or patients: Federico Rojo, Josep Tabernero, Joan Albanell, Eric Van Cutsem, Atsushi Ohtsu, Toshihiko Doi, Wasaburo Koizumi, Kuniaki Shirao, Hiroya Takiuchi, José Baselga Collection and assembly of data: Federico Rojo, Josep Tabernero, Joan Albanell, Eric Van Cutsem, Atsushi Ohtsu, Toshihiko Doi, Wasaburo Koizumi, Kuniaki Shirao, Hiroya Takiuchi, José Baselga Data analysis and interpretation: Federico Rojo, Josep Tabernero, Joan Albanell, José Baselga Manuscript writing: Federico Rojo, Josep Tabernero, S. Ramon Cajal, José Baselga Final approval of manuscript: Federico Rojo, Josep Tabernero, Joan Albanell, Eric Van Cutsem, Atsushi Ohtsu, Toshihiko Doi, Wasaburo Koizumi, Kuniaki Shirao, Hiroya Takiuchi, S. Ramon Cajal, José Baselga

 

	GLOSSARY

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Akt:

Protein kinase B belongs to a pathway that is responsible for cell survival. Following activation (ie, phosphorylation) by PI3K, activated Akt blocks the activity of molecules involved in the apoptotic pathway by in turn phosphorylating them.

EGFR (epidermal growth factor receptor):

Also known as HER-1, EGFR belongs to a family of receptors (HER-2, HER-3, HER-4 are other members of the family) and binds to the EGF, TGF-, and other related proteins, leading to the generation of proliferative and survival signals within the cell. It also belongs to the larger family of tyrosine kinase receptors and is generally overexpressed in several solid tumors of epithelial origin.

Gefitinib:

Belonging to the class of tyrosine kinase inhibitors, gefitinib (also known as Iressa) binds to the cytoplasmic region of the EGFR that also binds ATP. By competing with ATP binding that is essential for tyrosine phosphorylation, gefitinib inhibits activation of EGFR and blocks the cascade of reactions leading to cellular proliferation.

Ki67:

A marker of proliferation, Ki67 is a protein that is expressed in the nucleus of proliferating cells. Absent only in resting cells, cells in the G1, S, G2, and M phase of the cell cycle express this marker.

P27

^kip1: Belongs to the family of cell cycle regulators, typically known as cyclin-dependent kinase inhibitors (CDKI). Kip1/p27, like other CDKIs, binds cyclin-cdk complexes, leading to cell cycle arrest in the G1 phase of growth.

PI3K:

Phosphatidylinositol-3 phosphate kinase (PI3K) adds a phosphate group to PI3, which is a downstream signaling molecule involved in survival/proliferative pathways mediated by growth factors such as the EGF and the PDGFs.

pMAPK (phosphorylated mitogen-activated protein kinase):

MAPKs are a family of enzymes that form an integrated network influencing cellular functions such as differentiation, proliferation, and cell death. These cytoplasmic proteins modulate the activities of other intracellular proteins by adding phosphate groups to their serine/threonine amino acids. The phosphorylated form of MAPK is being used as a surrogate to the activated form of the receptor.

Tyrosine kinase inhibitor:

Molecules that inhibit the activity of tyrosine kinase receptors. They are small molecules developed to inhibit the binding of ATP to the cytoplasmic region of the receptor (eg, gefitinib), thus further blocking the cascade of reactions that is activated by the pathway.

	NOTES

 
Supported by AstraZeneca, Macclesfield, Cheshire, United Kingdom.

Presented in part at the 39th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 31, June 3, 2003.

Terms in blue are defined in the glossary, found at the end of this article and online at www.jco.org.

Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.

	REFERENCES

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13. Moasser MM, Basso A, Averbuch SD, et al: The tyrosine kinase inhibitor ZD1839 ("Iressa") inhibits HER2-driven signaling and suppresses the growth of HER2-overexpressing tumor cells. Cancer Res 61:7184-7188, 2001[Abstract/Free Full Text]

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15. Fei G, Ebert MPA, Mawrin C, et al: Reduced PTEN expression in gastric cancer and in the gastric mucosa of gastric cancer relatives. Eur J Gastroenterol Hepatol 14:297-303, 2002[CrossRef][Medline]

16. Li Y-L, Tian Z, Wu D-Y, et al: Loss of heterozygosity on 10q23.3 and mutation of tumor suppressor gene PTEN in gastric cancer and precancerous lesions. World J Gastroenterol 11:285-288, 2005[Medline]

17. Castillo SS, Brognard J, Petukhov PA, et al: Preferential inhibition of Akt and killing of Akt-dependent cancer cells by rationally designed phosphatidylinositol ether lipid analogues. Cancer Res 64:2782-2792, 2004[Abstract/Free Full Text]

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Submitted February 27, 2006; accepted May 17, 2006.

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