Elevated alpha1-acid glycoprotein in gastric cancer patients inhibits the anticancer effects of paclitaxel, effects restored by co-administration of erythromycin

Abstract

Paclitaxel (PTX) which easily elutes into ascites is widely used to treat gastric cancer patients with peritoneal carcinomatosis (PC), but clinical outcomes are suboptimal. Increased concentrations of α1-acid glycoprotein (AGP), an important drug-binding protein, have been reported in the plasma and ascites of cancer patients. This study sought to clarify whether AGP binds to PTX and alters its anticancer effects. AGP concentrations were measured in the serum and ascites of gastric cancer patients with PC and in the serum of healthy volunteers. The in vitro effects of AGP and AGP plus erythromycin (EM) on PTX were evaluated by MTT assays in the gastric cancer cell lines. We also measured AGP concentrations in the ascites of PC model mice and examined the effects of EM plus PTX on PC. The mean AGP concentrations in the serum and ascites of gastric cancer patients with PC were 1524 and 834 μg/mL, respectively, higher than the mean AGP concentration of 650 μg/mL observed in the sera of healthy volunteers. AGP > 400 μg/mL significantly suppressed the cell growth inhibitory effect of PTX in vitro, but the co-administration of EM restored it. Elevated AGP concentrations were observed in the ascites of PC model mice. Administration of PTX alone did not markedly diminish PC, whereas co-administration of PTX and EM significantly reduced PC (p = 0.011). AGP is an important regulatory factor modulating the anticancer activity of intraperitoneal PTX. The co-administration of PTX and EM may be effective in treating gastric cancer patients with PC.

Keywords: Erythromycin; Gastric cancer; Paclitaxel; Peritoneal carcinomatosis; α1-Acid glycoprotein.

Conflict of interest statement

The authors declare that they have no conflict of interest. Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Human and animal rights All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional review board at Kanazawa University and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All procedures performed in studies involving animals adhere to the Standard Guidelines for Animal Experiments at Kanazawa University. Informed consent Informed consent was obtained from all individual participants included in the study.

Figures

Fig. 1

Concentrations of AGP in the serum of gastric cancer patients with PC were about 2.5-fold higher than those of healthy volunteers. The mean concentration of AGP was higher in ascites of gastric cancer patients with PC than in the serum of healthy volunteer, but this difference was not statistically significant. Data are presented as mean ± SD. *p < 0.05 versus serum of healthy volunteers

Fig. 2

AGP concentrations in ascites of our xenograft model mouse increased with cancer progression, starting on day 10 and reaching a maximum of 400 μg/mL on day 21. Data are presented as mean ± SD. *p < 0.05 versus day 3

Fig. 3

Effect of PTX was assessed by MTT assays. a OCUM-2MD3 cell viability, b NUGC-3 cell viabilities. Results reported as mean ± SD of three independent experiments

Fig. 4

Effect of AGP (0–1200 μg/mL) on PTX-suppressed conditions was assessed by MTT assays. a OCUM-2MD3 cell viability, b NUGC-3 cell viability. Results reported as mean ± SD of three independent experiments. *p < 0.05 versus cells added culture medium alone

Fig. 5

Effect of the co-administration of PTX and EM on OCUM-2MD3 and NUGC-3 cell viabilities in a high-AGP environment was determined using MTT assays. OCUM-2MD3 and NUGC-3 cells were incubated with EM (0.1, 1, 10, 100 μM), AGP (800 μg/mL), and PTX (10 nM), and cell viabilities were measured. Data are presented as mean ± SD of three independent experiments. *p < 0.05 versus cells treated with PTX and AGP

Fig. 6

Effect of co-administration of PTX and EM without AGP on NUGC-3 cell viability was determined using MTT assays. NUGC-3 cells were incubated with EM (0.1, 1, 10, 100 μM), and PTX (10 nM), and cell viabilities were measured. The difference of cell viability between the group treated with PTX alone and the groups treated with PTX plus EM was not statistically significant. Data are presented as mean ± SD of three independent experiments

Fig. 7

Xenograft model was made by incubating OCUM-2MD3 into nu/nu mice intraperitoneally. Effect of PTX plus EM on metastatic nodules was assessed. a Macroscopic views of peritoneal nodules (arrow head). b Relative number and weight of metastatic peritoneal nodules in the xenograft model. Data are shown as mean ± SD. *p < 0.05 versus untreated group