Notch signaling is implicated in stem cell self-renewal, differentiation, and other developmental processes, and the Drosophila hairy and enhancer of split (HES) 1 basic helix-loop-helix protein is a major downstream effector in the Notch pathway. We found that HES1 was expressed at high levels in the hematopoietic stem cell (HSC)–enriched CD34+/[CD38/Lin]− /low subpopulation but at low levels in more mature progenitor cell populations. When CD34+ cells were cultured for 1 week, the level of HES1 remained high in the CD34+ subset that had remained quiescent during ex vivo culture but was reduced in CD34+ cells that had divided. To investigate the effects of HES1 in human and mouse hematopoietic stem–progenitor cells (HSPCs), we constructed conditional lentiviral vectors (lentivectors) to introduce transgenes encoding either wild-type HES1 or a mutant lacking the DNA-binding domain (ΔBHES1). We found that lentivector-mediated HES1 expression in CD34+ cells inhibited cell cycling in vitro and cell expansion in vivo, associated with upregulation of the cell cycle inhibitor p21cip1/Waf1 (p21). The HES1 DNA–binding domain was required for these actions. HES1 did not induce programmed cell death or alter differentiation in HSPCs, and while short-term repopulating activity was reduced in HES1-transduced mouse and human cells, long-term reconstituting HSC function was preserved. Our data characterize the complex, cell context–dependent actions of HES1 as a major downstream Notch signaling regulator of HSPC function.

Background: The goal of this study is to determine the efficacy and toxicity of weekly irinotecan as second-line chemotherapy in advanced gastric cancer after failure of cisplatin-based regimen. Methods: Gastric cancer patients failing cisplatin-based chemotherapy received 125 mg/m² of irinotecan weekly for 4 weeks followed by 2-week rest, until disease progression. Results: Thirty-seven patients were enrolled into this study. The objective response was documented in seven of 35 patients with measurable lesion (response rate 20%, 95% CI: 6.1–33.9). Eight patients (22.9%) had stable disease and overall tumor control rate was 42.9%. The disease remained stable in both of two patients without measurable disease. At a median follow-up duration of 15.8 months, median time to progression and overall survival were 2.6 months (95% CI: 2.4–2.8) and 5.2 months (95% CI: 3.6–6.7), respectively. Neutropenia and diarrhea were the main toxicities. Among 37 patients treated, grade 3/4 (G3/4) neutropenia occurred in 43.2/24.3% of patients, respectively, and was accompanied with fever in three patients. Non-hematologic toxicities consisted mainly of delayed diarrhea (G3/4, 18.9/0%) and nausea/vomiting (G3/4, 18.9/0%). These toxicities were manageable and there was no treatment-related death. Conclusions: This weekly schedule of irinotecan was modestly active against cisplatin-refractory gastric cancer and relatively well-tolerated with appropriate dose modification.

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.

To gain insight into clinically relevant mechanisms of irinotecan resistance, we undertook oligonucleotide microarray analyses on paired malignant effusion samples obtained from eight gastric cancer patients treated with weekly irinotecan. Pretreatment and posttreatment (48 h) effusion samples were obtained for each patient, and the change in expression profile was compared between clinical responders and nonresponders. When differences in the expression of genes were examined using SAM (Significance Analysis of Microarrays) software, five isoforms of the metallothionein family were identified to have significantly higher signal log ratios in five nonresponders, compared with three responders. Compared with control cells, metallothionein 1X (MT1X)-transfected AGS cells showed a 1.4-fold higher irinotecan IC50 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and tended to form more colonies. These findings collectively suggest that irinotecan-induced up-regulation of metallothionein might be associated with irinotecan resistance in patients with gastric cancer, although it remains to be confirmed in a larger data set.

In several recent reports, docetaxel (75–85 mg/m2) combined with fluorouracil (5-FU) and cisplatin has shown considerable efficacy but significant toxicities, especially neutropenia, in patients with advanced gastric cancer. The authors tested the efficacy and safety of a lower dose (50 mg/m2) of docetaxel, combined with 5-FU and cisplatin, in metastatic gastric cancer (MGC). Chemonaive patients with MGC received docetaxel (50 mg/m2 on day 1), cisplatin (80 mg/m2 on day 1), and 5-FU (1200 mg/m2 on days 1–3) every 21 days. Forty-seven patients with a median age of 55 years (range, 30–73 years) received a median of 4 cycles (range, 1–13+ cycles). Of the 42 efficacy-“evaluable” patients, 17 showed a partial response (response rate, 40%; 95% confidence interval [CI], 26–55) according to the independent review panel. With a median follow-up of 12.6 months for all patients, the median time to progression was 4.6 months (95% CI, 3.6–5.6 months) and overall survival was 9.7 months (95% CI, 8.4–11.0 months). Grade 3/4 neutropenia developed in 68% of patients, and febrile neutropenia/neutropenic infection occurred in 26%. The most common grade 3/4 nonhematologic toxicity was stomatitis (21%), followed by syncope (6%), diarrhea (4%), peripheral neuropathy (4%), dizziness (2%), constipation (2%), and abnormal liver function tests (2%). There was 1 possible treatment-related death. Lower dose (50 mg/m2) docetaxel combined with 5-FU and cisplatin was active in MGC with a tolerable toxicity profile.