Epigenetics is alive and growing

Caveolin-1 regulates metastatic behaviors of anoikis resistant lung cancer cells

Caveolin-1 (Cav-1), a protein component of cellular membrane, has been reported to regulate several cancer cell behaviors. However, its role on cancer metastasis in anoikis resistant cells is unknown. The present study aimed to investigate the correlation between Cav-1 level and aggressive behaviors of anoikis resistant cancer cells. Cav-1 and ShRNACav-1 stably transfected lung carcinoma cells, and anoikis resistant H_AR1 and H_AR2 cells expressing different levels of Cav-1 were subjected to anoikis, cell growth, anchorage-independent growth, extracellular matrix adhesion, cisplatin sensitivity, migration, and invasion assays. The correlations between cellular Cav-1 level and such cancer aggressive behaviors were evaluated. Results revealed that anoikis resistant lung cancer cells as well as Cav-1 overexpressing cells exhibit a significant increase in anchorage-independent growth, extracellular matrix adhesion, migration, and invasion in comparison to those of their parental H460 cells. Knock-down of Cav-1 by ShRNA transfection was able to reverse such metastatic potentials in H_AR2 cells. In addition, basal Cav-1 level of these cells was positively correlated with anoikis resistance, anchorage-independent growth, migration, and invasion behaviors of the cells, whereas such Cav-1 level showed poor correlation to cisplatin sensitivity, cell adhesion, and growth in attached condition. These findings give more information regarding role of Cav-1 in the regulation of behaviors of lung cancer cells.

The prima donna of epigenetics: the regulation of gene expression by DNA methylation

This review focuses on the mechanisms of DNA methylation, DNA methylation pattern formation and their involvement in gene regulation. Association of DNA methylation with imprinting, embryonic development and human diseases is discussed. Furthermore, besides considering changes in DNA methylation as mechanisms of disease, the role of epigenetics in general and DNA methylation in particular in transgenerational carcinogenesis, in memory formation and behavior establishment are brought about as mechanisms based on the cellular memory of gene expression patterns.

Acquisition of anoikis resistance in human osteosarcoma cells

Under normal circumstances, adhered cells die of anoikis when detached from their extracellular matrix (ECM). Resistance to anoikis has been implicated in the progression of many human malignancies by affording an increased survival time in the absence of matrix attachment, facilitating the migration and eventual colonisation of distant sites. In this study, an anoikis-resistant variant of the human osteosarcoma cell line, SAOS-2 (SAOSar), was generated by sequential cycles of culturing under adhered and suspended conditions. It was also shown that although parental SAOS (SAOSp) cells are a heterogeneous population with varying levels of sensitivity to anoikis, the establishment of anoikis-resistant clones was not necessarily the result of mere selection of a previously resistant subpopulation. Anoikis-resistant cells were also derived from anoikis-sensitive SAOS clones by exposure to anoikis-inducing culture conditions. This suggests that lack of the normal signalling generated by attachment to the ECM could represent a driving force towards anoikis resistance. Resistance to anoikis could not be attributed to a general defect in the apoptotic pathway since apoptosis in both sensitive and resistant populations was induced after treatment with staurosporine, cycloheximide and hydrogen peroxide. This suggests that the apoptotic machinery is intact in both anoikis-sensitive and -resistant SAOS cells and that the death signal in anoikis-sensitive cells is generated by the lack of attachment, most probably by unligated integrins. Anoikis-resistant cells have circumvented this death signal and remain viable despite suspended conditions.

Early detection and risk assessment: proceedings and recommendations from the Workshop on Epigenetics in Cancer Prevention

Recent advances in molecular biology that have provided a greater understanding of multistage carcinogenesis include the use of biomarkers of early detection and risk assessment. Prominent among such biomarkers are epigenetic changes. The field of epigenetics has seen a recent surge of interest among cancer researchers since alterations in DNA methylation have emerged as one of the most consistent molecular alterations in multiple neoplasms. Chromatin condensation, histone deacetylation, and promoter methylation are major steps in the epigenetic regulation of gene expression. Epigenetic changes may occur due to environmental factors, aging, and genomic imprinting. An important distinction between genetic and epigenetic alterations in cancer prevention is that the latter might be more easily reversed using therapeutic interventions. In the workshop the following areas of research were recognized for emphasis in future work: (1) basic epigenetic mechanisms in cancer need further investigation; (2) technology development in the area of epigenetics, such as high-throughput quantitative assays and increased sensitivity/specificity, is essential for the early detection and risk assessment of cancer; (3) the clinical application of epigenetic changes to cancer prevention and risk assessment needs further investigation. Further research will lead to the identification of new targets for cancer prevention.

RNA-binding ability of PIPPin requires the entire protein

Post-transcriptional fate of eukaryotic mRNAs depends on association with different classes of RNA-binding proteins (RBPs). Among these proteins, the cold-shock domain (CSD)-containing proteins, also called Y-box proteins, play a key role in controlling the recruitment of mRNA to the translational machinery, in response to environmental cues, both in development and in differentiated cells. We recently cloned a rat cDNA encoding a new CSD-protein that we called PIPPin. This protein also contains two putative double-stranded RNA-binding motifs (PIP(1) and PIP(2)) flanking the central CSD, and is able to bind mRNAs encoding H1 degrees and H3.3 histone variants. In order to clarify the role of each domain in the RNA-binding activity of PIPPin, we constructed a number of different recombinant vectors, encoding different regions of the protein. Here we report that only recombinant proteins that contain all the putative PIPPin domains show RNA-binding ability.