Impact of the expression of cyclin-dependent kinase inhibitor p27Kip1 and apoptosis in tumor cells on the overall survival of patients with non-early stage gastric carcinoma

Effect of p27(KIP1) on cell cycle and apoptosis in gastric cancer cells

AIM

To elucidate the effect of p27(KIP1) on cell cycle and apoptosis regulation in gastric carcinoma cells.

METHODS

The whole length of p27(KIP1) cDNA was transfected into human gastric cancer cell line SCG7901 by lipofectamine. Expression of p27(KIP1) protein or mRNA was analyzed by Western blot and RNA dot blotting, respectively. Effect of p27(KIP1) on cell growth was observed by MTT assay and anchorage-independent growth in soft agar. Tumorigenicity in nude mice was used to assess the in vivo biological effect of p27(KIP1). Flow cytometry, TUNEL, and electron microscopy were used to assess the effect of p27(KIP1) on cell cycle and apoptosis.

RESULTS

Expression of p27(KIP1) protein or mRNA increased evidently in SCG7901 cells transfected with p27(KIP1). The cell growth was reduced by 31% at 48 h after induction with zinc determined by cell viability assay. The alteration of cell malignant phenotype was evidently indicated by the loss of anchorage-independent growth ability in soft agar. The tumorigenicity in nude mice was reduced evidently (0.55+/-0.14 cm vs 1.36+/-0.13 cm, P<0.01). p27(KIP1) overexpression caused cell arrest with 36% increase (from 33.7% to 69.3%, P<0.01) in G1 population. Prolonged p27(KIP1) expression induced apoptotic cell death reflected by pre-G1 peak in the histogram of FACS, which was also confirmed by TUNEL assay and electron microscopy.

CONCLUSION

p27(KIP1) can prolong cell cycle in G1 phase and lead to apoptosis. p27(KIP1) may be a good candidate for cancer gene therapy.

Relation of overexpression of S phase kinase-associated protein 2 with reduced expression of p27 and PTEN in human gastric carcinoma

AIM: To investigate the significance of S phase kinase-associated protein 2 (Skp2) expression in human gastric carcinoma and the relation between expressions of Skp2, p27 and PTEN.

METHODS: Immunohistochemical analysis was performed on 138 gastric carcinoma specimens, their paired adjacent mucosa specimens, 102 paired lymphatic metastatic carcinoma tissue specimens, 30 dysplasia specimens, 30 intestinal metaplasia specimens, 10 chronic superficial gastritis specimens and 5 normal gastric mucosa specimens for Skp2 expression and on 138 gastric carcinoma specimens for p27 and PTEN expression.

RESULTS: Skp2 labeling frequency was significantly higher in intestinal metaplasia (12.68±0.86) and adjacent mucosa (19.32±1.22) than in normal gastric mucosa (0.53±0.13) and chronic superficial gastritis (0.47±0.19) (P = 0.000); in dysplasia (16.74±0.82) than in intestinal metaplasia (P = 0.000); in gastric primary carcinoma (31.34±2.17) than in dysplasia and adjacent mucosa (P = 0.000); in metastasis gastric carcinoma in lymph nodes (39.76±2.00) than in primary gastric carcinoma (P = 0.037), respectively. Skp2 labeling frequency was positively associated with differentiation degree (rho = 0.315, P = 0.000), vessel invasion (rho = 0.303, P = 0.000) and lymph node metastasis (rho = 0.254, P = 0.000) of gastric cancer. Expression of Skp2 was negatively associated with p27 (rho = -0.451, P = 0.000) and PTEN (rho = -0.480, P = 0.000) expression in gastric carcinoma. p27 ex-pression was positively associated with PTEN expression in gastric carcinoma (rho = 0.642, P = 0.000).

CONCLUSION: Skp2 overexpression may be involved in carcinogenesis and progression of human gastric carcinoma in vivo, possibly via p27 proteolysis. PTEN may regulate the expression of p27 by negatively regulating Skp2 expression.

Influence Of Ganoderm applanatum polysaccharide on tumor suppressor genes P16, P27 and Rb in mice

AIM: To probe into the underlying mechanism of Ganoderm applanatum polysaccharide against cancer.

METHODS: By immunohistochemistry and ELISA, we detected the expression of tumor suppressor gene P16, P27 and Rb in tumor tissues and blood serum respectively; By electron microscopy, we observed whether the apoptotic body existed or not in the tumor tissues.

RESULTS: After the treatment of Ganoderm applanatum polysaccharide, there was obvious difference in the quantities of P16, P27 and Rb genes expression between the experimental and control groups (P < 0.01), and there was a negative correlation of P16 and P27 expression with that of Rb (^mr = -0.094, ⁿr = -0.446). We observed the existence of apoptotic body in the tumor cells in the experimental group under electron microscope.

CONCLUSION: By activating tumor suppressor gene, Ganoderm applanatum polysaccharide can control the growth of tumor and accelerate the tumor cell apoptosis.

Expression of p27, cyclin E and cyclin A in hepatocellular carcinoma and its clinical significance

AIM: To investigate the expression of p27, cyclin E and cyclin A in hepatocellular carcinoma (HCC) and its potential clinical significance.

METHODS: Expression of p27, cyclin E and cyclin A in 45 HCC specimens and 30 adjacent noncancerous lesions obtained from 45 patients during surgery was examined by immunohistochemical SABC assay. The diameter of tumor ranged from 1 cm to 19 cm (d ≤ 5 cm, 9 samples; 5 cm < d ≤ 10 cm, 19 samples; d > 10 cm, 17 samples). The tumors were graded according to the criteria described by Edmondson-Steiner: well-differentiated HCC group (Grade I + II), 26 samples; poorly-differentiated HCC group (Grade III + IV), 19 samples. According to the clinical-pathologic features, 19 samples were poorly encapsulated, 15 samples had portal invasion of cancer, 11 samples had extrahepatic metastasis, and 12 samples had intrahepatic metastasis. All of the samples were classified as the invasive and metastatic group, while the remaining was classified as the non-invasive and non- metastatic group.

RESULTS: The average labeling index (LI) of p27 in HCC lesions was significantly higher than that in adjacent noncancerous lesions (45.87 ± 14.21 vs 33.77 ± 12.92, t = 3.745, P < 0.001). The LI of p27 was associated with differentiation, invasiveness and metastasis of the tumors (34.46 ± 12.29 vs 52.80 ± 11.36, t = 5.17; 41.42 ± 12.86 vs 51.44 ± 14.10, t = 2.48; P < 0.05). Cyclin E was overexpressed in 16 cases (35.6%) while cyclin A was overexpressed in 21 cases (46.7%) in HCC lesions. No overexpression of cyclin E or cyclin A could be observed in adjacent non-carcinoma lesions and normal liver tissues. The overexpressions of cyclin E and cyclin A were correlated with differentiation, tumor thrombus, invasiveness and metastasis (P < 0.05). Expression of cyclin E was significantly correlated with expression of cyclin A (r = 0.329, P < 0.05). The LI of p27 was significantly decreased in cyclin E, cyclin A positive groups (40.33 ± 11.91 vs 49.50 ± 13.76, t = 3.05; 38.86 ± 11.19 vs 52.57 ± 12.62, t = 3.89; P < 0.05).

CONCLUSION: p27, cyclin E, cyclin A play cooperative roles in HCC tumorigenesis, differentiation, invasiveness and metastasis. Detection of their expression may be helpful in prediction of tumor progression.