Modulation of cisplatin sensitivity and resistance by buthionine sulfoximine and cyclosporin A in human esophageal cancer cells.

We established a 2.4-fold cisplatin (CDDP)-resistant human esophageal cancer cell line (TE2R) from the parent TE2 line. CDDP accumulation was reduced in TE2R. The Na+, K+-ATPase inhibitor ouabain inhibited CDDP accumulation in TE2 but not TE2R, suggesting that TE2R may have alterations in the Na+, K+-ATPase and defective CDDP uptake mechanism. Buthionine sulfoximine (BSO) enhanced CDDP sensitivity of both cell lines and cyclosporin A (CsA) modified CDDP resistance in TE2R. These effects were associated with increased CDDP accumulation. Thus, BSO and CsA may be useful for modulation of CDDP sensitivity or resistance in esophageal cancer.

Augmentation of 5-fluorouracil cytotoxicity by epidermal growth factor in a newly established human signet-ring cell carcinoma of the stomach in culture.

A cell line designated TSG6 was established from a signet-ring cell gastric carcinoma developed in a 57-year-old female patient. The TSG6 cells had well preserved the features of signet-ring cell carcinoma based on morphology. The cells exhibited both epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) immunoreactivities, and also secreted EGF. Moreover, the growth of TSG6 cells was stimulated in the presence of exogenous EGF. These results suggest that the possible presence of an EGF/EGFR autocrine growth mechanism is expressed in the TSG6 cells. The simultaneous treatment with EGF and 5-fluorouracil (5-FU) produced a nearly 2.4-fold enhancement of 5-FU cytotoxicity against TSG6 cells. A bromodeoxyuridine/DNA flow cytometry analysis revealed that EGF augmented 5-FU cytotoxicity by inducing the accumulation of S phase cells which might be more susceptible to 5-FU. Moreover, we found that the incorporation of 5-FU into the TSG6 cells was increased with the addition of EGF. These data indicate that EGF may be a potent agent as a biological response modifier for 5-FU against the tumors which express the EGF/EGFR autocrine mechanism, and that the TSG6 cell line is useful in furthering our understanding of the interaction between anticancer drugs and EGF.

Flow cytometric analysis of early steps in development of adriamycin resistance in a human gastric cancer cell line.

We have established a low-level adriamycin (ADM)-resistant human gastric cancer cell line (MKN45R) from the parental cell line (MKN45) by exposure to stepwise increases of ADM concentration (final concentration, 0.026 microgram/ml). The purpose of this study was to identify the early steps in the development of ADM resistance in MKN45R by flow cytometric (FCM) analysis. Comparison of the concentration required for 50% growth inhibition, determined by a tetrazolium-based colorimetric assay, showed that MKN45R was about 2.6-fold more resistant to ADM than MKN45. However, the inhibition index values were 89.5% for MKN45 and 86.4% for MKN45R, respectively, showing that ADM was judged to be "effective" against both cell lines. On the other hand, cell kinetic analysis by FCM revealed that the increase of the ratio of G2M accumulation induced by ADM treatment was significantly lower (P < 0.01) in MKN45R. Moreover, the efflux of ADM estimated by FCM analysis was significantly increased (P < 0.05) in MKN45R even though there was no significant increase of P-glycoprotein expression. These results suggest that although ADM was still effective based on a standard drug sensitivity test, the cancer cells were already acquiring resistance to ADM as judged from FCM analysis. Moreover, the mechanism of this ADM resistance is considered to be independent of P-glycoprotein expression. Thus, FCM analysis is useful for detecting the early steps in the development of drug resistance of cancer cells.

[Flow cytometric BrdU/DNA assay for anticancer agent sensitivity test].

The significance of BrdU/DNA double staining method using flow cytometry as a chemosensitivity test of anticancer agents is herein reported. Experimentally, CDDP, ADM and MMC yielded a significant increase of G2 phase fraction at 24, 48 and 72 hours, and caused a significant decrease of BrdU labeling index at 48 hours. The changes of G2 phase fraction and BrdU labeling index were correlated well with the result of colony forming test, and, therefore, were considered as a useful index of lethal effect of anticancer agents. For the clinical application, enzymatic preparation and discontinuous Ficoll density gradient method might be advantageous to collect viable tumor cells from solid specimen. Flow cytometric BrdU/DNA assay can be clinically applied as a chemosensitivity test in selecting effective anticancer drugs.

Adenocarcinoma arising in Barrett's esophagus after total gastrectomy.

A 64-yr-old Japanese male who underwent a partial gastrectomy for a duodenal ulcer at the age of 21, a total resection of the remnant stomach for a stomal ulcer at age 25, and in whom Barrett's esophagus was diagnosed at age 47, was found to have a tumor at the distal esophagus and was operated on by thoracic esophagectomy. The tumor was a well to moderately differentiated adenocarcinoma invading down to the muscularis propria. The entire esophageal mucosa in the resected specimen was lined by columnar epithelium. This tumor was thought to derive from the Barrett's esophageal epithelium.

[A carcinoma of the reconstructed gastric tube after a radical esophageal cancer operation].

Reported are five patients who developed a carcinoma of the reconstructed gastric tube. In 3 of the 5 patients, the esophageal cancer was preceded by a gastric cancer, and the intervals before the gastric cancer was detected were 34, 24, and 60 months. The gastric tube the had been reconstructed by the retrosternal rout was resected with a median sternotomy in cases 1 and 2. In case 3, since a liver and lung metastasis had been detected by routine examination, surgery was not performed. Cases 4 and 5 had an esophageal cancer associated with a simultaneous early gastric cancer located in the lesser curvature of the upper body. Thus, a esophagectomy and a partial gastrectomy were performed. Twenty-eight and 21 months later, respectively, an early gastric cancer was found at the stump of the gastric tube that had been reconstructed by the retrosternal route. Endoscopic laser therapy was subsequently employed for both patients. Because of these findings, the author have concluded that postoperative serial examination of the gastric tube are very important, since cases of a gastric tube cancer are increasing.

[An experimental study of anticancer agent sensitivity test in human gastric cancer cell lines by flow cytometry].

The purpose of this study is to assess the lethal and kinetic effects of CDDP, ADM, MMC and 5FU on human gastric cancer cell lines, MKN28, MKN45 and KATO III. The lethal effect was examined by growth inhibition test and colony forming test. The DNA content and DNA synthesis rate of individual cells were simultaneously measured by DNA/BrdU double staining method. In growth inhibition test, MKN45 was sensitive to CDDP, and all cell lines were sensitive to ADM, MMC and 5FU. On the other hand, in colony forming test, these cell lines were sensitive to all drugs. In the cell kinetics, CDDP, ADM and MMC yielded a significant increase of G2 phase fraction at 24, 48 and 72 hours, and caused a significant decrease of BrdU labeling index at 48 hours. The changes of G2 phase fraction and BrdU labeling index were correlated well to the lethal effect of CDDP, ADM and MMC. However, 5FU did not cause these changes to the cell lines employed in the cell kinetic study. Therefore, it was suggested that these results of the cell kinetics might be applied to anticancer agent sensitivity test by selecting adequate anticancer drugs.