Gastric cancer: the role of insulin-like growth factor 2 (IGF 2) and its receptors (IGF 1R and M6-P/IGF 2R)

Up-regulated genes in diethylnitrosamine-induced liver cancer in rats

AIM: To investigate the differentially expressed genes in rat liver cancer induced by diethylnitrosamine (DEN), and to explore mechanism in DEN-induced carcinogenesis.

METHODS: The model of liver cancer was induced by DEN. The RNA was extracted purified from the cancer cells with routine methods. Affymetrix Rat 230A GeneChip and technique were used to detect the dis-crepancies of gene expression between tissues of nor-mal control and liver cancer.

RESULTS: Of 15710 genes in the GeneChip, the positive expression covered a percentage of 84.54% in liver cancer. There were 509 genes whose expression levels in liver cancer were about 5 times as high as those in the normal controls, of which 325 were EST fragments. Of the 325 genes, 184 ones were with known function, of which 168 had been reported in relevant references. Of the 168 genes, 100 ones were associated with the tumor (36 with liver cancer), 4 with liver, and the other 64 had no relation with tumor and liver.

CONCLUSION: DEN-induced up-regulations of genes in liver cancer are fairly complicated, of which 168 ones need paying more attention to.

A 14-kDa cathepsin L-derived carboxyl IGFBP-2 fragment is sequestered by cultured rat ileal crypt cells

IGF-II gut drives mucosal growth during gestation. IGF binding protein-2 (IGFBP-2) has a high affinity for IGF-II and tightly regulates IGF-II availability during fetal and early neonatal growth. We have previously demonstrated that glucocorticoids alter IGF homeostasis in the neonatal ileum, but the mechanism(s) by which this occurs is poorly understood. We hypothesized that dexamethasone alters proteolytic regulation of IGFBP-2 in ileal crypt cells. To test this, ileal crypt [ileal epithelial (IEC)-18] cells were cultured in serum-free media and used to study IGFBP-2 catabolism by immunochemistry, gene array analysis, and pharmacological perturbation with dexamethasone. In addition, isolated human IGFBP-2, IGF-II, and cathepsins B, D, and L were utilized for in vitro protease assays. We found IGFBP-2 to be highly abundant in IEC-18 culture, and sequestration of carboxyl IGFBP-2 antigen was seen within vesicular bodies of some cells. Dexamethasone significantly decreased the number of these cells and decreased IGFBP-2 in the media. On gene array analysis, cathepsin L's message abundance was significantly increased by dexamethasone, and, by in vitro assay, cathepsin L created a 14-kDa carboxyl fragment that corresponded to the sole antigen detected in IEC-18 cell lysates as well as a 16.5-kDa fragment found in the media. The sequestered fragment size was formed preferentially when IGF-II was present, whereas the larger fragment size was formed preferentially when IGF-II was absent. Cathepsins B and D did not produce these fragments in vitro and were not detected in IEC-18 media. We conclude that dexamethasone alters IGFBP-2 catabolism through its effects on cathepsin L.

Expression of some tumor associated factors in human carcinogenesis and development of gastric carcinoma

AIM: To study the effect of IGF-1/IGF-1R and gastrin/CCK-BR on carcinogenesis and development of human gastric carcinoma and to explore its mechanism and provide a credible theoretical foundation for early diagnosis and molecular therapy of gastric carcinoma.

METHODS: mRNA expression levels of IGF-1/IGF-1R and gastrin/CCK-BR were assessed by RT-PCR method in gastric cancer tissues, adjacent mucosa, and tumor-free tissues from 56 patients with gastric carcinoma and normal gastric mucosae from 56 healthy controls. Tissue specimens were obtained by biopsy and confirmed by histological evaluation.

RESULTS: The mRNA levels of IGF-1/IGF-1R were increased in gastric cancer tissues compared with normal tissues from healthy controls and successively increased in tumor-free tissues, adjacent mucosa, and gastric cancer tissues. The mRNA levels of gastrin/CCK-BR were increased in gastric cancer tissues compared with normal tissues from healthy controls. There was a significant difference between gastric cancer tissues and adjacent mucosa and tumor-free tissues, but the mRNA levels of gastrin were not significantly increased in adjacent mucosa and gastric cancer tissues compared with tumor-free tissues. The mRNA levels of CCK-BR were increased in gastric cancer tissues and adjacent mucosa compared with tumor-free tissues, but not significantly increased in adjacent mucosa and gastric cancer tissues compared with gastric cancer tissues.

CONCLUSION: Overexpression of IGF-1/IGF-1R and gastrin/CCK-BR promotes the disorderly proliferation of gastric mucosa epithelia and it is of great significance in the carcinogenesis and development of gastric carcinoma.

High insulin-like growth factor-2 (IGF-2) gene expression is an independent predictor of poor survival for patients with advanced stage serous epithelial ovarian cancer

OBJECTIVE

Epithelial ovarian cancer is the deadliest gynecologic malignancy, yet its molecular etiology remains poorly understood. Evidence is accumulating to support a role for the insulin-like growth factor family in human carcinogenesis, and recently using microarray expression analysis, we demonstrated over-expression of the insulin-like growth factor-2 (IGF-2) gene in advanced stage epithelial ovarian cancers. The purpose of the current study is to further elucidate the role of the IGF-2 gene in ovarian cancer development and progression.

METHODS

Relative expression of IGF-2 was measured in 109 epithelial ovarian cancers and eight normal ovarian surface epithelial (NOSE) samples, using quantitative real-time polymerase chain reaction. Associations with clinicopathological parameters were examined.

RESULTS

Expression of the IGF-2 gene was more than 300-fold higher in ovarian cancers compared with normal ovarian surface epithelium samples (P <0.001). High IGF-2 expression was associated with advanced stage disease at diagnosis (P <0.001), high-grade cancers (P <0.05) and sub-optimal surgical cytoreduction (P = 0.08). In multivariate analysis, relative IGF-2 expression was an independent predictor of poor survival.

CONCLUSIONS

Expression of the IGF-2 gene is significantly higher in ovarian cancers relative to normal ovarian surface epithelium. Further, high IGF-2 gene expression is associated with high grade, advanced stage disease, and is an independent predictor of poor survival in patients with epithelial ovarian cancer. As such, IGF-2 is a molecular marker and potential therapeutic target for the most aggressive epithelial ovarian cancers.

Association between expression of transcription factor Sp1 and increased vascular endothelial growth factor expression, advanced stage, and poor survival in patients with resected gastric cancer

The biological and clinical behaviors of cancer are affected by multiple molecular pathways that are under the control of transcription factors. Improved understanding of how transcription factors affect cancer biology may lead to improved ability to predict clinical outcome and discovery of novel therapeutic strategies. We evaluated the relationship between Sp1 and vascular endothelial growth factor (VEGF) expression, as well as their effect on survival in 86 cases of resected human gastric cancer. The degree of VEGF expression correlated highly with Sp1 expression (P < 0.01). Patients with high Sp1 expression were 98 times more likely to have high VEGF expression compared with those with negative Sp1 expression. Clinically, negative or weak Sp1 expression was associated with early stage (IA) in gastric cancer. Strong Sp1 expression was more frequently observed among patients with stage IB-IV disease (P = 0.035). Similarly, whereas strong Sp1 expression was uncommonly observed among patients with N0 or N1 disease (19 and 16%), N2/N3 gastric cancer was associated with strong Sp1 expression (48%; P = 0.034). Strong Sp1 expression was also associated with inferior survival. The median survival duration in patients who had a tumor with a negative, weak, and strong Sp1 expression was 44, 38, and 8 months (P = 0.0075), respectively, whereas patients with strong VEGF expression had a shorter survival duration; the difference was not statistically significant. When Sp1 and VEGF expression, stage, completeness of resection, histology, and patient age were entered in a Cox proportional hazards model, strong Sp1 expression (P = 0.021) and an advanced disease stage (P < 0.001) were independently prognostic of poor survival. Given the importance of Sp1 in the expression of VEGF, our data suggest that dysregulated Sp1 expression and activation play important roles in VEGF overexpression and, thus, gastric cancer development and progression.

Polymorphism in IGF-2 as a Surrogate Marker for Predisposition towards Tobacco Chewing-Mediated Oral Cancer

Insulin and insulin-like growth factors (IGFs) are major determinants of proliferation and apoptosis, thereby playing a significant role in carcinogenesis. Epidemiological evidence associates high levels of INS and IGFs with an increased risk of cancer. Polymorphism of the genes involved in insulin-signaling pathways has been associated with a variable risk for neoplasms in different ethnic and environmental backgrounds. In this study, using PCR-RFLP-based assays, we investigated the distribution of genetic polymorphism in INS and IGF-2 genes in tobacco chewing-mediated oral cancer patients (n = 60) and healthy controls (n = 45) of Indian ethnic origin. The genotyping was performed for +1127 INS-Pst1 in INS and +3580 IGF-2-Msp1 in IGF-2. The frequencies of the IGF-2 genotypes AG, GG and AA found in oral cancer patients were 0.68, 0.2 and 0.12, respectively, whereas in noncancer controls these frequencies were 0.27, 0.71 and 0.02. Frequencies of each allele, i.e. CT, TT and CC of INS gene, were found to be nearly equal in the tumor (0.22, 0.75 and 0.03) as well as the normal (0.27, 0.67 and 0.06) population. A significant difference was observed in genotypic frequencies of IGF-2 and INS in the Indian ethnic population as compared to the Caucasian, African and Hispanic populations. Polymorphism at +1127 INS-Pst1 locus of INS gene does not show an implication in oral cancer, whereas the genotype AG or AA at +3580 IGF-2-Msp1 locus of IGF-2 is associated with progression and increased risk of oral cancer. From our study we can conclude that single nucleotide polymorphisms in the IGF-2 gene can be used as a marker for prediction of the risk of oral carcinogenesis.

The Consequences of Insulin-Like Growth Factors/Receptors Dysfunction in Lung Cancer

The aim of this study was to investigate the consequences of insulin-like growth factors (IGF) and IGF receptor dysfunction in lung carcinomas. A correlation between increased expression (at mRNA and protein levels) for IGF-1 and IGF-1R and decreased apoptosis were found in large-cell carcinomas and adenocarcinomas. In 40% of informative adenocarcinomas expressing the highest values of IGF-2 and Ki-67 proteins, M6P/IGF-2R gene had LOH at one allele and a mutation in another allele. All four squamous cell carcinoma samples expressed LOH/mutation in the M6P/IGF-2R gene. The alphaIR3 strongly diminished proliferation and increased apoptosis in cultures established from squamous cell carcinomas overexpressing IGF-2 and IGF-1R. Telomerase activity was assessed in four squamous cell carcinomas. Cell treatment with IGF-1 increased telomerase activity. The opposite was observed when the cells were treated with alphaIR3, which inhibits the activity of IGF-1 receptors. Our findings suggest that disruption of the IGF/IGF receptors axis is involved in lung cancer formation.