Stimulatory effect of EGF and inhibitory effect of sialoadenectomy on growth of an EGF receptor-hyperproducing human gastric cancer xenograft in nude mice

Association between EGF +61 A>G polymorphism and gastric cancer risk: A meta-analysis

Previous studies suggested an association between the EGF +61 A>G polymorphism and susceptibility to gastric cancer, but the results have been inconsistent. To draw a more precise risk estimation of the association, we performed a meta-analysis of published studies. PubMed, EMBASE, Google Scholar and the Chinese Wanfang databases were systematically searched to identify relevant studies. There were 7 studies involving 1992 cases of gastric cancer and 3202 controls in this meta-analysis. Our study showed that, overall, the EGF +61 A>G polymorphism was significantly associated with the increased risk of gastric cancer in allele model (G vs. A: OR=1.18, 95% CI=1.00-1.39), dominant model (GG + GA vs. AA: OR=1.28, 95% CI=1.05-1.55), homozygous model (GG vs. AA: OR=1.31, 95% CI=1.06-1.63) and heterozygous model (GA vs. AA: OR=1.25, 95% CI=1.01-1.53). The stratified analysis by ethnicity revealed a significant association between EGF +61 A>G polymorphism and gastric cancer risks in Asians. This meta-analysis indicates that EGF +61 A>G polymorphism may increase the risk of gastric cancer, especially in Asians. Large-sized, well-designed studies involving different ethnic groups should be conducted to confirm this association.

Digest

In his last digest of 1994, Professor Yoshio Mishima, Editor-in-Chief of Surgery Today (The Japanese Journal of Surgery), has selected from the July to September 1994 issues of that journal.

Effect of a submaxillary gland extract on Ehrlich tumor growth in mice

Ablation of host submaxillary glands modifies Ehrlich tumor growth and tumor-infiltrating leukocytes, possibly by modifications in the serum level of growth factors produced by this gland. To extend this research, 7-month-old male EPM-1 mice (N = 30) were divided into two groups: 1) inoculated with tumor cells previously incubated with submaxillary salivary gland extract (SGE) in PBS for 30 min at 37%; 2) inoculated with tumor cells previously incubated with PBS, under the same conditions. Animals were inoculated into the footpad with 40 microl of a suspension containing 4.5 x 10(7) tumor cells/ml, and footpad thickness was measured daily for 10 days. Sections and smears of tumor cells were prepared from the tumor mass to determine mitosis frequency, percent of tumor cells immunopositive to nerve (NGF) and epidermal (EGF) growth factors and percent of tumor-infiltrating leukocytes. The incubation of tumor cells with SGE produced a tumor reduction of about 30% in size (P<0.01). This effect was not related to loss of cell viability during incubation, but a 33% increase (P<0.05) in the percentage of dead or dying tumor cells and a 15% increase in the percent of NGF/EGF-positive tumor cells (P<0.01) were observed in vivo at the end of experiment. Tumor-infiltrating lymphocytes and mitosis frequency did not differ between groups. These data suggest a direct effect of factors present in SGE on tumor cells, which induce degeneration of tumor cells.

The Jun kinase 2 isoform is preferentially required for epidermal growth factor-induced transformation of human A549 lung carcinoma cells

We have previously found that epidermal growth factor (EGF) mediates growth through the Jun N-terminal kinase/stress-activated kinase (JNK/SAPK) pathway in A549 human lung carcinoma cells. As observed here, EGF treatment also greatly enhances the tumorigenicity of A549 cells, suggesting an important role for JNK in cancer cell growth (F. Bost, R. McKay, N. Dean, and D. Mercola, J. Biol. Chem. 272:33422-33429, 1997). Several isoforms families of JNK, JNK1, JNK2, and JNK3, have been isolated; they arise from alternative splicing of three different genes and have distinct substrate binding properties. Here we have used specific phosphorothioate oligonucleotides targeted against the two major isoforms, JNK1 and JNK2, to discriminate their roles in EGF-induced transformation. Multiple antisense sequences have been screened, and two high-affinity and specific candidates have been identified. Antisense JNK1 eliminated steady-state mRNA and JNK1 protein expression with a 50% effective concentration (EC50) of <0.1 microM but did not alter JNK2 mRNA or protein levels. Conversely, antisense JNK2 specifically eliminated JNK2 steady-state mRNA and protein expression with an EC50 of 0.1 microM. Antisense JNK1 and antisense JNK2 inhibited by 40 and 70%, respectively, EGF-induced total JNK activity, whereas sense and scrambled-sequence control oligonucleotides had no effect. The elimination of mRNA, protein, and JNK activities lasted 48 and 72 h following a single Lipofectin treatment with antisense JNK1 and JNK2, respectively, indicating sufficient duration for examining the impact of specific elimination on the phenotype. Direct proliferation assays demonstrated that antisense JNK2 inhibited EGF-induced doubling of growth as well as the combination of active antisense oligonucleotides did. EGF treatment also induced colony formation in soft agar. This effect was completely inhibited by antisense JNK2 and combined-antisense treatment but not altered by antisense JNK1 alone. These results show that EGF doubles the proliferation (growth in soft agar as well as tumorigenicity in athymic mice) of A549 lung carcinoma cells and that the JNK2 isoform but not JNK1 is utilized for mediating the effects of EGF. This study represents the first demonstration of a cellular phenotype regulated by a JNK isoform family, JNK2.

A monoclonal antibody against rat calcitonin inhibits the growth of a rat medullary thyroid carcinoma cell line in vitro

Medullary thyroid carcinoma (MTC) cells synthesize large amounts of calcitonin (CT), which serves clinically as a useful tumor marker. To examine the possibility of CT serving as a target in immunotherapy for MTC, we raised and characterized more than 40 monoclonal antibodies (mAbs) against rat CT (rCT). The affinity constants for the mAbs were between 2.8 x 10(9) and 1.8 x 10(11) M(-1). Some mAbs react preferentially with solid phase rat CT, but not with liquid phase 125I-labeled rCT. Thirty-nine mAbs cross-react with human CT. We evaluated the antitumor effect of the mAbs in vitro by analysis of [3H]thymidine incorporation into the rat MTC cell line CRL-1607. Some antibodies show an antiproliferative effect, but most are inactive. One mAb (2E5G5, IgG2b), which preferentially reacts with solid phase rCT, but not with liquid phase 125I-labeled rCT, exerts an antiproliferative activity on CRL-1607. At 6.25 x 10(-7) M, 2E5G5 killed all of the tumor cells independently of complement in a cytotoxicity assay. We explored the cytotoxic mechanisms by assays for cell cycle arrest and DNA fragmentation. The antitumor effect was manifested by apoptosis and cell cycle arrest. Hence, a secreted peptide may serve as a target in tumor immunotherapy. Therapeutically antibodies may exert antitumor activity by a variety of mechanisms. The antitumor effect of this mAb in a rat animal tumor model is being tested.

Inhibitory effect of anti-epidermal growth factor receptor antibody on a human gastric cancer

BACKGROUND

Blockading the putative epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha)/EGF receptor autocrine pathway with anti-EGF receptor monoclonal antibody (MoAb) might prevent the growth of tumor.

METHODS

The present study was designed to examine the effect of MoAb 528 on the growth of an EGF receptor which was hyperproducing human gastric cancer cells in vitro and in vivo.

RESULTS

Treatment with MoAb 528 inhibited the growth of cultured cells in a dose-dependent manner. Twenty micrograms of MoAb 528 given intraperitoneally after inoculation of 1 x 10(6) cells and 200 micrograms of the MoAb 528 given after inoculation of 1 x 10(7) cells to athymic mice inhibited the growth of the xenograft. Twenty micrograms of MoAb 528 from a miniosmotic pump, which releases its contents over 2 weeks, also prevented the growth of the xenograft when the treatment was started on the day after tumor inoculation. However, no inhibitory effect was observed when the treatment was started 3 weeks after inoculation. The binding capacity of 125I-EGF on the MoAb treated tumors was diminished in comparison with control tumors.

CONCLUSIONS

The results suggest that MoAb 528 blocks the EGF or TGF-alpha/EGF receptor signal pathway, resulting in the inhibition of cancer cell growth. This MoAb 528 may therefore be an effective antitumor agent against human gastric cancer that shows expression of the EGF receptor.

Epidermal growth factor (EGF)

Despite the wealth of information concerning EGF and its related peptides, its precise role in the control of gastrointestinal functions is still not fully resolved. However, there is no doubt that it can have some very potent effects on the gastrointestinal tract. These may be related to the control of growth and development and to the regular control of cell renewal. Nevertheless, in the adult, EGF may only be active in response to luminal damage and repair, and furthermore this may also only occur if the luminal EGF is protected from proteolytic degradation. Notwithstanding this, 'EGF'-like responses may be evoked in the gut by intestinal TGF-alpha. The possible therapeutic use of EGF and members of its family in ulcer therapy will be discussed in later Chapters of this volume, other potential uses are in the control of necrotising enteritis and in the alleviation of the mucositis associated with cancer treatment.

Clinical significance of epidermal growth factor (EGF), EGF receptor, and c-erbB-2 in human gastric cancer

The EGF stimulation system for growth regulation is implicated in normal and neoplastic cell proliferation. The role of EGF, the EGF receptor, and c-erbB-2 in human gastric cancer is reviewed on the basis of several reports, which have been mainly oriented toward their clinical significance. EGF has been shown immunohistochemically to be present in 26% of gastric cancers (n = 395). The presence of EGF in gastric cancer is correlated with the degree of gastric wall invasion and lymph node metastasis. The 5-year survival of patients with EGF-positive tumors is worse than that of patients with EGF-negative tumors. The presence of EGF in human gastric cancer may therefore represent a higher malignant potential. Fifteen percent of gastric cancers (n = 352) were also shown to be positive for both EGF and the EGF receptor immunohistochemically, and the simultaneous occurrence of EGF and the EGF receptor suggests that these tumors grow in an autocrine fashion. Tumors exhibiting EGF and the EGF receptor simultaneously show a greater degree of local invasion and lymph node metastasis. Increased expression of EGF receptor protein in gastric cancer appears to be related to biologic aggressiveness, although gene amplification has occurred only to a small extent. Twelve percent of gastric cancers (n = 486) were found to be positive for c-erbB-2. This type of tumor has a frequent metastasis, and patients with c-erbB-2-positive cancer have a poorer prognosis than those with c-erbB-2-negative tumors. Selective blockade of the EGF receptor and c-erbB-2 from their ligands with monoclonal antibodies (MoAbs) inhibits the growth of human gastric cancer xenografts. These MoAbs may therefore be effective antitumor agents against gastric cancer showing overexpression of EGF receptors or c-erbB-2.