Gene expression in colorectal neoplasia: modifications induced by tissue ischaemic time and tissue handling protocol.

AIMS: The heterogeneity within individual distinct cancer types in terms of behaviour, response to therapy and prognosis is well recognized. A major goal of translational research projects has therefore been to define clinically significant subgroups of individual tumour types by analysis of mRNA as well as protein expression. An essential premise of such investigations is that expression of these key molecules is a true reflection of conditions present within the neoplastic cells in vivo. The aim was to investigate the effect of methods of tissue handling and storage on expression of mRNA. METHODS AND RESULTS: mRNA expression in 60 biopsy samples obtained from 10 patients with colorectal tumours was examined. The mRNA expression profile and the level of expression of specific mRNA species were significantly affected by the procedures used for collection and storage of tissue samples. Significant variation in the level of expression (both increased and decreased) of transcripts was detectable after 15 min, and by 120 min there was a fourfold increase in the number of genes with a more than twofold change in the level of expression. CONCLUSIONS: Reliable interpretation of results of gene expression at the mRNA level requires standardized protocols for tissue procurement.

Seliciclib (CYC202, R-roscovitine) enhances the antitumor effect of doxorubicin in vivo in a breast cancer xenograft model.

We sought to determine whether seliciclib (CYC202, R-roscovitine) could increase the antitumor effects of doxorubicin, with no increase in toxicity, in an MCF7 breast cancer xenograft model. The efficacy of seliciclib combined with doxorubicin was compared with single agent doxorubicin or seliciclib administered to MCF7 cells and to nude mice bearing established MCF7 xenografts. Post-treatment cells and tumors were examined by cell cycle analysis, immunohistochemistry and real-time PCR. Seliciclib significantly enhanced the antitumor effect of doxorubicin without additional murine toxicity. MIB1 (ki67) immunohistochemistry demonstrated reduced proliferation with treatment. The levels of p21 and p27 increased after treatment with doxorubicin or seliciclib alone or in combination, compared to untreated controls. However, no changes in p53 protein (DO1, CM1), survivin or p53 phosphorylation (SER15) were observed in treated tumors compared with controls. In conclusion, the CDK inhibitor seliciclib (R-roscovitine) enhances the antitumor effect of doxorubicin in MCF7 tumors without increased toxicity with a mechanism that involves cell cycle arrest rather than apoptosis.

MDM2 SNP309 is associated with high grade node positive breast tumours and is in linkage disequilibrium with a novel MDM2 intron 1 polymorphism.

INTRODUCTION: A functional polymorphism within MDM2, SNP309 T>G, has been linked to early onset cancer. This study examined clinical associations of breast cancer with SNP309 in a Scottish Caucasian population and investigated additional MDM2 intron 1 polymorphisms. METHODS: Intron 1 of MDM2 was PCR amplified and directly sequenced from 299 breast cancer patients and 275 cancer free controls and compared with clinical and pathological parameters. RESULTS: SNP309 was observed, for the control and breast cancer cohorts respectively, at frequencies of: T/T = 44.7% and 39.5%; G/T = 42.2% and 47.2%; G/G = 13.1% and 13.4%, indicating that SNP309 is not a predisposing factor for breast cancer. The 309G/G genotype was associated with high grade tumours (OR = 1.64, 95%CI = 1.06-2.53, p = 0.025) and greater nodal involvement (OR = 2.51, 95%CI = 1.26-4.98, p = 0.009). SNP309 was not associated with an earlier age of cancer diagnosis. No association was observed between genotype and age of breast cancer diagnosis when patients were stratified by menopausal status and estrogen receptor status. Three additional low frequency SNPs were identified: 344T>A, 285G>C and 443G>T, the latter two novel. SNP285 was in complete linkage disequilibrium with SNP309 (D' = 1.0) with the minor alleles being in phase with each other. Moreover, the 285C/C, 309G/G double homozygous genotype was only observed in the breast cancer cohort. CONCLUSION: SNP309G/G is associated with poor prognostic breast cancer features in the Scottish population. Additionally, a novel SNP, SNP285, that is in linkage disequilibrium with SNP309, may also have a role in breast tumorigenesis.

Tumor 18F-FDG incorporation is enhanced by attenuation of P53 function in breast cancer cells in vitro.

UNLABELLED: Mutations in the p53 gene, often resulting in loss of wild-type (WT) p53 expression, are found at high frequencies in several cancer types. High uptake of (18)F-FDG detected using (18)F-FDG PET has been associated with a poor prognosis. To determine whether high (18)F-FDG uptake may be related to decreased expression of WT p53, we examined (18)F-FDG uptake in cells transfected with dominant negative p53 constructs that abrogate WT p53 function. METHODS: Two clones of MCF-7 breast cancer cells were stably transfected with a dominant negative p53 construct. (18)F-FDG uptake, hexokinase (HK) activity, and glucose transport were measured in each clone and in the control WT cells from which the clones had been derived. The expression of glucose transporters, HKs, and glucose-6-phosphatase was determined using microarray technology. RESULTS: Microarray experiments revealed that glucose transporters 1, 8, and 10 were expressed in MCF-7 cells, whereas glucose-6-phosphatase was absent. HK I was the principal HK in MCF-7 cells but was not differentially expressed at the messenger RNA level in the dominant negative p53 clones, compared with WT cells. However, increased HK activity was observed in both dominant negative p53 clones, compared with WT MCF-7. (18)F-FDG uptake was increased in both clones expressing the dominant negative p53 constructs. CONCLUSION: These data suggest that abrogation of p53 in breast cancer is associated with specific changes in glucose metabolism detected by PET.

Evidence that the dephosphorylation of Ser(535) in the epsilon-subunit of eukaryotic initiation factor (eIF) 2B is insufficient for the activation of eIF2B by insulin.

Eukaryotic initiation factor (eIF) 2B is a guanine-nucleotide exchange factor that plays a key role in the regulation of protein synthesis. It is activated by insulin, serum and other agents that stimulate general protein synthesis. The largest (epsilon) subunit of eIF2B is a substrate for glycogen synthase kinase (GSK)-3 in vitro, and phosphorylation by GSK3 inhibits the activity of eIF2B. The site of phosphorylation has previously been identified as Ser(535). GSK3 is inactivated by phosphorylation in response to insulin or serum. In Chinese-hamster ovary cells, insulin and serum bring about the dephosphorylation of Ser(535) in vivo, concomitantly with the phosphorylation of GSK3, and these effects are mediated through signalling via phosphoinositide 3-kinase. We have made use of inhibitors of GSK3 to determine whether GSK3 is responsible for phosphorylation of Ser(535) in vivo and to explore the role of phosphorylation of Ser(535) in the regulation of eIF2B. Treatment of cells with LiCl or with either of two recently developed GSK3 inhibitors, SB-415286 and SB-216763, brought about the dephosphorylation of Ser(535), which strongly indicates that this site is indeed a target for GSK3 in vivo. However, these compounds did not elicit significant activation of eIF2B, indicating, consistent with conclusions from one of our previous studies, that additional inputs are required for the activation of eIF2B. Our results also show that each of the inhibitors used affects overall protein synthesis and have additional effects on translation factors or signalling pathways apparently unrelated to their effects on GSK3, indicating that caution must be exercised when interpreting data obtained using these compounds.