Decreased expression of p33ING1 mRNA in lymphoid malignancies

Genetic alterations and expression of inhibitor of growth 1 in human sporadic colorectal cancer

AIM: To explore the effect and significance of inhibitor of growth 1 (ING1) gene in carcinogenesis and progression of human sporadic colorectal cancer.

METHODS: mRNA expression, mutation, and loss of heterozygosity (LOH) of ING1 gene in 35 specimens of sporadic colorectal cancer tissues and the matched normal mucous membrane tissues were detected by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), PCR-single strain conformation polymorphism (PCR-SSCP) and PCR-simple sequence length polymorphism (PCR-SSLP) using microsatellite markers, respectively.

RESULTS: The average ratios of light intensities of p33^ING1b and p47^ING1a mRNA expression in the cancerous tissues were significantly lower than those in normal tissues. The difference between the two mRNA splices was not significant in the matched tissues. In addition, the ratios of light intensities of p33^ING1b and p47^ING1a mRNA expression in the cancerous tissues of Dukes?stages C and D were significantly lower than those in cancerous tissues of Dukes?stages A and B. However, no mutation of ING1 gene was detected in all 35 cases; only 4 cases of LOH (11.4%) were found.

CONCLUSION: p33^ING1b and p47^ING1a mRNA expressions are closely related with the carcinogenesis and progression of human sporadic colorectal cancer. No mutation of ING1 gene is found, and there are only few LOH in sporadic colorectal cancers. These might not be the main reasons for the down regulation of ING1 expression. Its low expression may happen in transcription or post-transcription.

Inhibitory effect of tumor suppressor p33ING1b and its synergy with p53 gene in hepatocellular carcinoma

AIM: To investigate the inhibitory effect of tumor suppressor p33^ING1b and its synergy with p53 gene in hepatocellular carcinoma (HCC).

METHODS: Recombinant sense and antisense p33^ING1b plasmids were transfected into hepatoma cell line HepG2 with lipofectamine. Apoptosis, G₀/G₁ arrest, cell growth rate and cloning efficiency in soft agar of HepG2 were analyzed after transfection. In three hepatoma cell lines with different endogenous p53 gene expressions, the synergistic effect of p33^ING1b with p53 was analyzed by flow cytometry and luciferase assay was performed to detect the activation of p53 downstream gene p21^WAF1/CIP1. In addition, the expression and mutation rates of p33^ING1b in HCC tissues were measured by immunohistochemistry and polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP).

RESULTS: Overexpression of p33^ING1b inhibited cell growth of HepG2, induced more apoptosis and protected cells from growth in soft agar. Combined transfer of p33^ING1b and p53 gene promoted hepatoma cell apoptosis, G₀/G₁ arrest and elevated expression of p21^WAF1/CIP1. Immunostaining results showed co-localized p33^ING1b with P53 protein in HCC tissues and there was a significant relation between protein expression rates of these two genes (P<0.01). Among 28 HCC samples, p33^ING1b presented a low gene mutation rate (7.1%).

CONCLUSION: p33^ING1b collaborates with p53 in cell growth inhibition, cell cycle arrest and apoptosis in HCC. Loss or inactivation of p33^ING1b normal function may be an important mechanism for the development of HCC retaining wild-type p53.

Genetic alterations and reduced expression of tumor suppressor p33ING1b in human exocrine pancreatic carcinoma

AIM: To detect the expression of p33^ING1b protein and the change of p33^ING1b gene in pancreatic carcinoma and to evaluate the significance of p33^ING1b in pancreatic cell carcinogenesis.

METHODS: Pathological specimens from pancreatic carcinoma and matched non-tumor pancreatic tissues were examined for p33^ING1b expression and mutation by immunohistochemistry, polymerase chain reaction single-strand conformation polymorphisms (PCR-SSCP) and loss of heterozygosity (LOH).

RESULTS: The rate of p33^ING1b protein expression was 85% (34/40). A single germline missense mutation was detected in 1 of 40 tumors located at codon 215: TGC-TCC (Cys-Ser). Fourteen (60.9%) of 23 tumor samples showed LOH in all of the informative markers tested, but no mutation was detected in these tumors and only two of the informative tumors lacked expressions of p33^ING1b protein.

CONCLUSION: Mutation and loss of expression are not the main reasons for the disfunction of p33^ING1b in pancreatic carcinoma, an abnormality at the level of chromosome and/or transcription may inhibit their normal functions, potentially contributing to pancreatic cell carcinogenesis.