Microstructure,mechanical properties and wear resistance of SiC_(p)/AZ91 composite prepared by vacuum pressure infiltration

SiC_(p)/AZ91 composites were prepared by vacuum pressure infiltration.The microstructure,mechanical properties and wear resistance of composite were studied.Results indicated that SiC particles were uniformly distributed in the metal matrix and had a good interface bonding with the metal matrix.Mg_(17)Al_(12) preferably precipitated near the SiC particles,and high-density dislocations were induced by the mismatch of the coefficient of thermal expansion(CTE)between the SiC particle and the AZ91 matrix,thereby accelerating the aging precipitation of the matrix.Compared with AZ91 alloy,the addition of SiC particles improves the hardness and compressive strength of the composite,which is mainly due to the load transfer strengthening and grain refinement strengthening mechanisms.Furthermore,a stable support surface-protecting matrix formed during the wear process because of the excellent wear resistance of SiC.

Clinicopathological significance of LRP16 protein in 336 gastric carcinoma patients

AIM： To investigate the expression of leukemia related protein 16 （LRP16）, and the possible relationship between LRP16 expression and clinicopathological indices in 336 gastric carcinoma patients. METHODS： Immunohistochemistry was used to detect LRP16 expression in 336 cases of paraffin-embedded gastric carcinoma tissues and 60 cases of distal normal mucosa. The relationships between LRP16 expression and patients＇ age, tumor size, histological grade, clinical stage, metastatic status and prognosis were analysed. RESULTS： The expression of LRP16 was 58.6% （197/336） in gastric carcinoma and 31.7% （19/60） in distal normal gastric mucosa. The expression of LRP16 in carcinoma was significantly higher than that in normal mucosa tissues （x^2 = 14.929, P = 0.001）. LRP16 protein expression was found in 44.1% （63/143） carcinomas at stage Ⅰ and Ⅱ, and 69.4% （134/193） carcinomas at stage Ⅲ and Ⅳ （Z2 = 21.804, P = 0.001）, and in 56.9% （182/320） of cancers without metastasis but 93.8% （15/16） of those with metastasis （2 = 8.543, P = 0.003）. The expression of LRP16 was correlated with tumor size, infiltrative depth, clinical stage, lymphatic invasion and distant metastasis （all P 〈 0.05）. Follow-up data showed that there was a significant difference in median survival time between cancer patients with expression of LRP16 （27.0 mo） and those without （48.0 mo, Log rank =31.644, P = 0.001）. CONCLUSION： The expression of LRP16 may be associated with invasion, metastasis and prognosis of gastric cancer.

Overexpression of carbonic anhydrase Ⅱ and Ki-67 proteins in prognosis of gastrointestinal stromal tumors

AIM: To investigate the expression and prognostic value of carbonic anhydrase Ⅱ (CA Ⅱ) and Ki-67 in gastrointestinal stromal tumors (GISTs). METHODS: One hundred and thirteen GIST patients admitted to Chinese People's Liberation Army General Hospital from January 2004 to December 2010 were retrospectively followed up, and immunohistochemistry was used to detect CA Ⅱ, Ki-67 and CD117 expression in tumor samples. The survival rates of the patients were analyzed using the Kaplan-Meier method. Log-rank test, χ 2 test and Cox proportional hazards model were used to determine the relationships between CA Ⅱ, Ki-67 and CD117 expression and prognostic value in GISTs. RESULTS: The survival rates at 1, 3 and 5 years were 90.0%, 82.0% and 72.0% in all patients. However, in patients with positive CA Ⅱ or Ki-67, the survival rates were 92.0%, 83.0% and 77.0% or 83.0%, 66.6% and 53.0%, respectively. Compared with the negative groups, the survival rates in the positive groups were significantly lower (CA Ⅱ log-rankP = 0.000; Ki-67 logrank P = 0.004). Multivariate Cox analysis revealed that CA Ⅱ, CD117 and Ki-67 were considerable immune factors in prognosis of GIST patients (CA Ⅱ P = 0.043; CD117 P = 0.042; Ki-67 P = 0.007). Besides, tumor diameter, mitotic rate, tumor site, depth of invasion, complete resection, intraoperative rupture, and adjuvant therapy were important prognosis predictive factors. Our study indicated that CA Ⅱ had strong expression in GISTs and the prognosis of GISTs with high CA Ⅱ expression was better than that of GISTs with low or no expression, suggesting that CA Ⅱ is both a diagnostic and prognostic biomarker for GIST. CONCLUSION: CA Ⅱ and Ki-67 are significant prognostic factors for GISTs. CA Ⅱ associated with neovascular endothelia could serve as a potential target for cancer therapy.

Aberrant cytological localization of p16 and CDK4 in colorectal epithelia in the normal adenoma carcinoma sequence

AIM： To study the correlation between the patterns of subcellular expression of p16 and CDK4 in colorectal epithelia in the normal-adenoma-carcinoma sequence.METHODS： Paraffin sections of 43 cases of normal colorectal epithelia and corresponding adenomas as well as carcinomas were analysed immunocytochemically for subcellular expression of p16 and CDK4 proteins.RESULTS： Most carcinomas showed more cytoplasmic overexpression for p16 and CDK4 than the adenomas from which they arised or the adjacent normal mucosa. Most normal or non-neoplastic epithelia showed more p16 and CDK4 expression in the nucleus than their adjacent adenomas and carcinomas. There was a significant difference between the subcellular expression pattern of p16 and CDK4 in normal-adenoma-carcinoma sequence epithelia （P 〈 0.001）. Neither p16 nor CDK4 subcellular patterns correlated with histological grade or Dukes＇ stage.CONCLUSION： Interaction of expression of p16 and CDK4 plays an important role in the Rb/p16 pathway.Overexpression of p16 and CDK4 in the cytoplasm, as well as loss expression of p16 in the nucleusmighlc be important in the evolution of colorectal carcinoma from adenoma and, of adenoma from normal epitheiia.

Growth inhibitory effect of wild-type Kras2 gene on a colonic adenocarcinoma cell line

AIM： To observe the growth inhibitory effect of wild-type Kras2 gene on a colonic adenocarcinoma cell line Caco-2. METHODS： Recombinant plasmid pCI-neo-Kras2 with wild type Kras2 open reading frame was constructed. The Caco-2 cells were transfected with either pCI-neo or pCI-neo-Kras2 using Upofectamine 2000. The expression of wild type Kras2 was examined by Northern blot analysis. And the expression of wild type Kras2 protein was examined by Western blot analysis. The effects of wild-type Kras2 on cell proliferation were analyzed by monotetrazolium （MTT） assay, meanwhile analyses of cell cycle and spontaneous apoptosis rate were carried out by flow cytometry （FCM）. RESULTS： The plasmid of pCI-neo-Kras2 was successfully established. The growth rate of cells transfected with pCI-neo-Kras2 was significantly lower than the control cells transfected with the empty pCI- neo vector （P 〈 0.05）. Cell cycle analysis revealed arrest of the pCI-neo-Kras2 transfected cells in G0/G1 phases, decreased DNA synthesis and decreased fractions of cells in S phase. The proliferative index of cells transfected with pCI-neo-Kras2 was decreased compared with the control cells （49.78% vs 64.21%）, while the apoptotic rate of Caco-2 cells with stable Kras2 expression increased （0.30% vs 0.02%）. CONCLUSION： The wild-type Kras2 gene effectively inhibits the growth of the colonic adenocarcinoma cell line Caco-2.

Loss of heterozygosity of Kras2 gene on 12p12-13 in Chinese colon carcinoma patients

AIM： To study the loss of heterozygosity （LOH） on 12p12-13 in Chinese colon carcinoma patients.METHODS： DNA was extracted from 10 specimens of cancer tissue, 10 specimens of adjacent tissue and 10 specimens of normal tissue, respectively. LOH of Kras2 gene was analyzed by polymerase chain reaction （PCR） and denaturing polyacrylamide gel electrophoresis using 11 microsatellite markers on 12p-12-13.RESULTS： LOH of Kras gene was detected at least on one marker of 12p-12-13 in 30% （3/10） of adjacent tissue specimens. The highest frequency of LOH was identified on D12S1034 in 28.57% （2]7） of adjacent tissue specimens. LOH was detected at least on one marker of 12p12-13 in 60% （6/10） of carcinoma tissue specimens, the most frequent LOH was found on D12S1034 and D12S1591 in 42.86% （3/7） of carcinoma tissue specimens. LOH was detected in 30% （3/10） of carcinoma tissue specimens, 30% （3/10） of adjacent tissue specimens, and no signal in 1% （1/0） carcinoma tissue specimen. The occurrence of LOH did not correlate with sex, age, tumor size and lymph node metastasis.CONCLUSION： Genomic instability may occur on 12p-12-13 of Kras2 gene in the development and progression of colon carcinoma. The high LOH of Kras2 gene may directly influence the transcription and translation of wild type Kras2 gene.