Hark Kyun Kim

Identification of Genes with Differential Expression in Acquired Drug-Resistant Gastric Cancer Cells Using High-Density Oligonucleotide Microarrays

Purpose: A major obstacle in chemotherapy is treatment failure due to anticancer drug resistance. The emergence of acquired resistance results from host factors and genetic or epigenetic changes in the cancer cells. The purpose of this study was to identify differentially expressed genes associated with acquisition of resistance in human gastric cancer cells. Experimental Design: We performed global gene expression analysis in the acquired drug-resistant gastric cancer cell lines to the commonly used drugs 5-fluorouracil, doxorubicin, and cisplatin using Affymetrix HG-U133A microarray. The gene expression patterns of 10 chemoresistant gastric cancer cell lines were compared with those of four parent cell lines using fold-change and Wilcoxon’s test for data analysis. Results: We identified over 250 genes differentially expressed in 5-fluorouracil-, cisplatin-, or doxorubicin-resistant gastric cancer cell lines. Our expression analysis also identified eight multidrug resistance candidate genes that were associated with resistance to two or more of the tested chemotherapeutic agents. Among these, midkine (MDK), a heparin-binding growth factor, was overexpressed in all drug-resistant cell lines, strongly suggesting that MDK might contribute to multidrug resistance in gastric cancer cells. Conclusions: Our investigation provides comprehensive gene information associated with acquired resistance to anticancer drugs in gastric cancer cells and a basis for additional functional studies.

Assessment of lymph node metastases using 18F-FDG PET in patients with advanced gastric cancer

PurposeThe aim of this study was to assess the diagnostic accuracy of 18F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) with respect to lymph node (LN) metastasis in patients with advanced gastric cancer, and to ascertain the factors that affect this accuracy.MethodsSeventy-three patients with advanced gastric cancer, verified in all cases by endoscopic biopsy, were enrolled in this prospective study. We conducted FDG PET and other routine preoperative studies, including abdominal computed tomography (CT). Patients underwent either curative-intent gastrectomy and lymphadenectomy (n=67) or exploratory laparotomy. The Japanese system for the classification of gastric cancer was used for LN assessment.ResultsFDG PET was able to detect primary lesions in 70 of the 73 cases. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value of FDG PET for LN metastasis were 40%, 95%, 91% and 56%, respectively. Signet-ring cell carcinoma was associated with the lowest sensitivity (15%), whereas other cell types could be detected with moderate sensitivity (30–71%) and high specificity (93–100%). According to multiple logistic regression, the standardised uptake value for primary tumours was the only independent variable to be significantly related to sensitivity for LN metastasis (p=0.02, odds ratio=1.14). CT was superior to PET in terms of sensitivity (p<0.0001), and PET was superior to CT in terms of specificity (p<0.0001) and PPV (p=0.05).ConclusionFDG PET exhibits good specificity for LN staging of gastric cancer, and FDG uptake in the primary tumour is significantly related to the accuracy of FDG PET. Despite some clear limitations, FDG PET proved useful in the LN staging of FDG-avid gastric cancer.

Gefitinib as a First-Line Therapy of Advanced or Metastatic Adenocarcinoma of the Lung in Never-Smokers

Purpose: A subset of patients with adenocarcinoma of the lung who had never smoked cigarettes showed excellent tumor responses to gefitinib therapy. To evaluate the efficacy of gefitinib as a first-line therapy in this subgroup of patients, we conducted a phase II study. Experimental Design: Eligible patients had no smoking history, stage IIIB or IV adenocarcinoma, Eastern Cooperative Oncology Group performance status 0 to 2, and adequate organ functions. Treatment consisted of daily oral administration ofF 250 mg gefitinib for 28 days until disease progression. Responses were assessed after every two cycles of therapy. Results: Of 37 patients enrolled, 36 were assessed for response. Twenty-five patients (69%) had partial response, 4 (11%) had stable disease, and 7 (19%) had progressive disease. Of 10 patients with evaluable brain metastases, 7 had objective responses in both intracranial and extracranial lesions, 1 had stable disease in the brain and dramatic response in the extracranial lesions, and 2 had progressive disease in both sites. After a median follow-up of 48 weeks (range, 4-70 weeks), 26 patients had disease progression, with median progression-free survival of 33 weeks, and 9 patients died, all due to disease progression. The median survival time has not been reached yet but the estimated 1-year survival rate was 73%. Common toxicities were skin rash and mild diarrhea but there was no significant hematologic toxicity. Conclusions: Gefitinib showed very dramatic antitumor activity, even in the brain, with unprecedented survival outcome in never-smoker adenocarcinoma patients. These data support the use of gefitinib as a first-line therapy in this particular subgroup.

miRNA signature associated with outcome of gastric cancer patients following chemotherapy

BackgroundIdentification of patients who likely will or will not benefit from cytotoxic chemotherapy through the use of biomarkers could greatly improve clinical management by better defining appropriate treatment options for patients. microRNAs may be potentially useful biomarkers that help guide individualized therapy for cancer because microRNA expression is dysregulated in cancer. In order to identify miRNA signatures for gastric cancer and for predicting clinical resistance to cisplatin/fluorouracil (CF) chemotherapy, a comprehensive miRNA microarray analysis was performed using endoscopic biopsy samples.MethodsBiopsy samples were collected prior to chemotherapy from 90 gastric cancer patients treated with CF and from 34 healthy volunteers. At the time of disease progression, post-treatment samples were additionally collected from 8 clinical responders. miRNA expression was determined using a custom-designed Agilent microarray. In order to identify a miRNA signature for chemotherapy resistance, we correlated miRNA expression levels with the time to progression (TTP) of disease after CF therapy.ResultsA miRNA signature distinguishing gastric cancer from normal stomach epithelium was identified. 30 miRNAs were significantly inversely correlated with TTP whereas 28 miRNAs were significantly positively correlated with TTP of 82 cancer patients (P<0.05). Prominent among the upregulated miRNAs associated with chemosensitivity were miRNAs known to regulate apoptosis, including let-7g, miR-342, miR-16, miR-181, miR-1, and miR-34. When this 58-miRNA predictor was applied to a separate set of pre- and post-treatment tumor samples from the 8 clinical responders, all of the 8 pre-treatment samples were correctly predicted as low-risk, whereas samples from the post-treatment tumors that developed chemoresistance were predicted to be in the high-risk category by the 58 miRNA signature, suggesting that selection for the expression of these miRNAs occurred as chemoresistance arose.ConclusionsWe have identified 1) a miRNA expression signature that distinguishes gastric cancer from normal stomach epithelium from healthy volunteers, and 2) a chemoreresistance miRNA expression signature that is correlated with TTP after CF therapy. The chemoresistance miRNA expression signature includes several miRNAs previously shown to regulate apoptosis in vitro, and warrants further validation.

Gastric Cancer-Specific Protein Profile Identified Using Endoscopic Biopsy Samples via MALDI Mass Spectrometry

To date, proteomic analyses on gastrointestinal cancer tissue samples have been performed using surgical specimens only, which are obtained after a diagnosis is made. To determine if a proteomic signature obtained from endoscopic biopsy samples could be found to assist with diagnosis, frozen endoscopic biopsy samples collected from 63 gastric cancer patients and 43 healthy volunteers were analyzed using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. A statistical classification model was developed to distinguish tumor from normal tissues using half the samples and validated with the other half. A protein profile was discovered consisting of 73 signals that could classify 32 cancer and 22 normal samples in the validation set with high predictive values (positive and negative predictive values for cancer, 96.8% and 91.3%; sensitivity, 93.8%; specificity, 95.5%). Signals overexpressed in tumors were identified as alpha-defensin-1, alpha-defensin-2, calgranulin A, and calgranulin B. A protein profile was also found to distinguish pathologic stage Ia (pT1N0M0) samples (n = 10) from more advanced stage (Ib or higher) tumors (n = 48). Thus, protein profiles obtained from endoscopic biopsy samples may be useful in assisting with the diagnosis of gastric cancer and, possibly, in identifying early stage disease.

A Gene Expression Signature of Acquired Chemoresistance to Cisplatin and Fluorouracil Combination Chemotherapy in Gastric Cancer Patients

Background We initiated a prospective trial to identify transcriptional alterations associated with acquired chemotherapy resistance from pre- and post-biopsy samples from the same patient and uncover potential molecular pathways involved in treatment failure to help guide therapeutic alternatives. Methodology/Principal Findings A prospective, high-throughput transcriptional profiling study was performed using endoscopic biopsy samples from 123 metastatic gastric cancer patients prior to cisplatin and fluorouracil (CF) combination chemotherapy. 22 patients who initially responded to CF were re-biopsied after they developed resistance to CF. An acquired chemotherapy resistance signature was identified by analyzing the gene expression profiles from the matched pre- and post-CF treated samples. The acquired resistance signature was able to segregate a separate cohort of 101 newly-diagnosed gastric cancer patients according to the time to progression after CF. Hierarchical clustering using a 633-gene acquired resistance signature (feature selection at P<0.01) separated the 101 pretreatment patient samples into two groups with significantly different times to progression (2.5 vs. 4.7 months). This 633-gene signature included the upregulation of AKT1, EIF4B, and RPS6 (mTOR pathway), DNA repair and drug metabolism genes, and was enriched for genes overexpressed in embryonic stem cell signatures. A 72-gene acquired resistance signature (a subset of the 633 gene signature also identified in ES cell-related gene sets) was an independent predictor for time to progression (adjusted P = 0.011) and survival (adjusted P = 0.034) of these 101 patients. Conclusion/Significance This signature may offer new insights into identifying new targets and therapies required to overcome the acquired resistance of gastric cancer to CF.

Decreased pyruvate kinase M2 activity linked to cisplatin resistance in human gastric carcinoma cell lines

Resistance to anticancer drugs is a major obstacle preventing effective treatment of disseminated cancers. Understanding the molecular basis to chemoresistance is likely to provide better treatment. Cell lines resistant to cisplatin or 5‐fluorouracil (5‐FU) were established from human gastric carcinoma cell lines SNU‐638 and SNU‐620. Comparative proteomics involving 2‐dimensional gel electrophoresis (2‐DE) and matrix‐associated laser desorption ionization‐mass spectroscopy (MALDI‐MS) was performed on protein extracts from these parental and drug‐resistant derivative lines to screen drug resistance‐related proteins. Pyruvate kinase M2 (PK‐M2) was identified as a protein showing lower expression in cisplatin‐resistant cells compared to parental cells. Consistent with this finding, PK‐M2 activity was also lower in cisplatin‐resistant cells. Suppression of PK‐M2 expression by antisense oligonucleotide resulted in acquired cisplatin resistance in SNU‐638 cells. Furthermore, PK‐M2 activity in 11 individual human gastric carcinoma cell lines positively correlated with cisplatin sensitivity. Taken together, PK‐M2 protein and activity levels were lower in cisplatin‐resistant human gastric carcinoma cell lines compared to their parental cell lines. Furthermore, suppression of PK‐M2 expression using antisense oligonucleotides increased cisplatin resistance. These data clearly link PK‐M2 and cisplatin resistance mechanisms.

Weekly docetaxel in combination with capecitabine in patients with metastatic gastric cancer.

Docetaxel (T) and capecitabine (X) are active agents against gastric cancer with synergistic antitumor effects. We conducted the current phase II study to assess the response rate and toxicity of combination TX regimen in patients with metastatic gastric cancer. Eligible patients were treated with docetaxel (36 mg/m2 intravenously) on days 1 and 8 and capecitabine (1000 mg/m2 orally twice a day) on days 1–14 of a 3-week schedule until progression occurred. From December 2001 to May 2003, 55 patients with median age of 54 years (range, 22–73 years) were enrolled; 47 patients had measurable lesions. A total of 358 courses of treatment were given, with a median of 5 (range, 1–22+) per patient. Objective responses were documented in 19 of 47 patients with measurable lesions (response rate, 40.4%; 95% confidence interval [CI], 25.9–54.9), with the median response duration of 5.6 months (range, 2.1–13.6+). At a median follow up of 15.9 months for all of 55 study patients, the median time to progression and survival were 4.5 months (95% CI, 3.4–5.6) and 12.0 months (95% CI, 7.5–16.6), respectively. Hematologic toxicities were mild to moderate, and the observed grade 3 nonhematologic toxicities, the most frequent of which was stomatitis, were generally manageable. Four patients experienced pneumonitis, but all of them responded to steroid treatment. The TX regimen was relatively well tolerated and effective against metastatic gastric cancer, with the added advantage of being an outpatient regimen.

Circulating numbers of endothelial progenitor cells in patients with gastric and breast cancer

Angiogenic factors like VEGF or G-CSF were reported to mobilize endothelial progenitor cells (EPCs) from the bone marrow. These EPCs were shown to be incorporated in the neovessels of developing tumors. Although the concentrations of angiogenic factors in the peripheral blood were reported to be elevated in cancer patients, the number of circulating EPCs has not been previously investigated. In this study, the number of EPCs circulating in the blood in 16 healthy controls and 71 newly diagnosed cancer patients was examined by a culture assay of peripheral blood mononuclear cells. The number of circulating EPCs was not found to be increased in cancer patients, although the plasma levels of VEGF were elevated. It is suggested that VEGF, at concentrations typical of those observed in the blood of cancer patients, does not mobilize EPCs into the peripheral blood.

Endoscopic Ultrasound and Computed Tomography in Restaging and Predicting Prognosis After Neoadjuvant Chemotherapy in Patients With Locally Advanced Gastric Cancer

The objective of the current study was to assess the staging accuracy and prognostic role of preoperative endoscopic ultrasound (EUS) and computed tomography (CT) in patients with locally advanced gastric cancer (LAGC) after neoadjuvant chemotherapy.