Targeting of cholecystokinin B/gastrin receptor in colonic, pancreatic and hepatocellular carcinoma cell lines.

Gastrin is a growth factor for both gastrointestinal and non-gastrointestinal tumours. Endocytosis of gastrin has been demonstrated in tumour cell lines expressing cholecystokinin-B/gastrin receptor (CCK-BR); this has raised the possibility of receptor targeted therapy. The aim of this study was to examine endocytosis of gastrin and CCK-BR in tumour cell lines. A small gastrin analogue, RG-G7, and the anti-CCK-BR antibody, anti-GRE1, were fluorescently labelled and uptake by cancer cell lines including AR42J, HepG2, and C170HM2 as well as transfected NIH3T3 fibroblast cells was assessed using standard and confocal fluorescence microscopy. CCK-BR expression of cell lines was assayed by reverse transcription-polymerase chain reaction and Western blotting. Apoptosis was detected using a fluorescent TUNEL method. RG-G7 and anti-GRE1 antibody were specifically taken up by all cell lines expressing CCK-BR. In addition to cytoplasmic uptake with RG-G7 and anti-GRE1 the latter also showed specific uptake into the nucleus. A coincidence of anti-GRE1 and apoptosis was seen. Targeting CCK-BR by peptide or antibody may offer therapeutic opportunities for some cancers.

An open-label, multinational, multicenter study of G17DT vaccination combined with cisplatin and 5-fluorouracil in patients with untreated, advanced gastric or gastroesophageal cancer: the GC4 study.

BACKGROUND: Gastrin hormone is trophic to in vitro gastric cancer, and the antigastrin antibodies (AGAs) are antiproliferative and antimetastatic. Human gastric cancers overexpress gastrin genes and receptors that react to gastrin's trophic effects. Immunogen G17DT elicits a specific and high-affinity AGA. The authors evaluated G17DT vaccination given with cisplatin plus 5-fluorouracil for the treatment gastric adenocarcinoma. METHODS: In this multicenter, Phase II study, patients received G17DT vaccination intramuscularly on Weeks 1, 5, 9 and 25 and cisplatin plus 5-fluorouracil every 28 days. Eligible patients had untreated, metastatic, or unresectable gastric or gastroesophageal adenocarcinoma with near-normal organ function. The primary endpoint of the study was the over response rate (ORR), and secondary endpoints included overall survival (OS), safety, and the impact of successful vaccination on patient outcome. RESULTS: In total, 103 patients were enrolled in 5 countries. Seven patients who were overdosed inadvertently with 5-fluorouracil (a major protocol violation) were removed from the analysis. The confirmed ORR was 30% in 79 patients who were evaluated for response. The median time-to-progression (TTP) was 5.4 months, and the median survival (MS) was 9.0 months (n = 96 patients). Sixty-five of 94 patients who were vaccinated (69%) had 2 consecutive AGA titers of > or =1 units (successfully vaccinated patients or immune-responders). The TTP was longer in immune-responders than in immune-nonresponders (P = .0005). Similarly, the MS was longer in immune-responders than in immune-nonresponders (10.3 months vs. 3.8 months; P < or =.0001). In a multivariate analysis, successful vaccination was an independent OS prognosticator (P = .0001). G17DT did not have an adverse effect on safety. CONCLUSIONS: The results demonstrated that successful G17DT vaccination was correlated with longer TTP and MS. AGA response was an independent OS prognosticator. A Phase III evaluation of G17DT in gastric cancer is warranted.

Expression of gastrin and its receptor in human gastric cancer tissues.

PURPOSE: Gastrin is a growth factor of cancerous and normal cells of the gastrointestinal tract, and its effect is known to be mediated by gastrin/cholecystokinin B (CCKB) receptor. This study was performed to investigate the prognostic significance and the expression profiles of gastrin and gastrin receptor in human gastric carcinoma tissues. METHODS: We analyzed the expressions of gastrin and gastrin receptor by immunohistochemical staining using anti-gastrin Ab (Sigma, St. Louis, MO, USA) and anti-gastrin receptor Ab (Aphton Corp., Woodland, CA, USA) in 279 gastric adenocarcinoma patients. Patients' clinicopathologic features and prognoses were analyzed. RESULTS: The gastrin expression rate in these patients was 47.7% (133/279) and the gastrin receptor expression rate was 56.5% (158/279). Gastrin expression was significantly higher in men than in women (54.3% vs. 34.1%), and higher in differentiated gastric adenocarcinoma than in the undifferentiated type (55.1% vs. 43.0%). The gastrin receptor expression rate was also significantly higher in men than in women (61.2% vs. 47.3%), and was higher in the differentiated type than in the undifferentiated type (72.9% vs. 46.5%), and significantly higher in the intestinal type than in the diffuse type (75.2% vs. 42.9%). Gastrin and gastrin/CCKB receptor expressions were not found to be significant prognostic factors in themselves. When focused on correlation between the co-expression of gastrin and gastrin/CCKB receptor and the survival, the prognosis of patients positive for both gastrin and gastrin receptor was significantly poorer than for those negative for gastrin and gastrin receptor in diffuse-type gastric cancer patients. However, multivariate analysis showed that only TNM stage was an independent prognostic factor of survival in diffuse-type gastric cancer patients. CONCLUSIONS: This study shows that the expression rates of gastrin and gastrin receptor are high (about a half) in gastric carcinoma tissues, and that there is an association between gastrin and gastrin receptor expression. We also found that patients with diffuse-type gastric carcinoma tissues expressing both gastrin and gastrin receptor have a poorer prognosis than those negative for both, which suggests that gastrin acts as an autocrine growth factor in a subgroup of gastric carcinomas.

Growth effect of gastrin on gastric cancer and its clinical implications for gastric cancer surgery.

This study was aimed at investigating the effect of gastrin on the growth of gastric cancer and evaluating postoperative hypergastrinemia in patients that had received various types of gastrectomy for gastric cancer. RT-PCR for gastrin/CCKB receptor mRNA was performed in human gastric cancer cell lines and tissue. The effect of gastrin or glycine-extended gastrin on the growth of gastric cancer cell lines was determined by MTT assay. Serum gastrin levels were compared with respect to the resection type of gastric cancer surgery. Gastrin/CCKB receptor mRNA expression was detected in all 9 gastric cancer cell lines, and in 19 of 29 (62%) gastric cancer tissue samples. Growth of gastric cancer cell lines containing the gastrin/CCKB receptor was significantly enhanced by gastrin and glycine-extended gastrin. The proximal gastrectomy group had a significantly higher mean serum gastrin level than the distal subtotal gastrectomy, total gastrectomy, or preoperative groups (p<0.05). Our study confirms that a high proportion of gastric cancer tissue samples express the gastrin/CCKB receptor, which can stimulate the growth of gastrin/CCKB receptor-positive gastric cancer cells. In addition, we confirm that hypergastrinemia can be induced in about half of patients after proximal gastrectomy. More studies are needed to clarify the relationship between hypergastrinemia and tumor recurrence after proximal gastrectomy.

Vaccines and monoclonal antibodies.

The immunoglobulin molecule contains structural features that make it a powerful tool for cancer therapy (eg, an extremely high specificity and binding affinity for the target molecule that results in low toxicity). Several approaches have been used: monoclonal antibodies targeting a ligand (eg, bevacizumab, anti-vascular endothelial growth factor), monoclonal antibodies targeting a receptor (eg, cetuximab, anti-epidermal growth factor receptor), vaccines targeting a ligand (eg, G17DT, anti-gastrin), or a cell surface antigen (eg, carcinoembryonic antigen-TRIad of COstimulatory Molecules, anti-CEA). Another approach attempts to harness the cellular arm of the immune response (ie, cytotoxic T cells, natural killer cells) for specific killing of tumor cells. The putative underlying mechanism of antibody strategy is the inhibition of intracellular signaling pathways and induction of apoptosis. Clinical evidence suggests that while most of these antibodies achieve limited antitumor activity as monotherapy, they are significantly more efficacious than single agents when combined with chemotherapy. Future use of these agents will include optimized combination chemotherapy/immunotherapy regimens as well as monoclonal antibodies conjugated to cytotoxic molecules and radionuclides.