The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue-nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected.

Mutations of the retinoblastoma tumor suppressor gene (RB1) or components regulating the CDK-RB-E2F pathway have been identified in nearly every human malignancy. Re-establishing cell cycle control through CDK inhibition has therefore emerged as an attractive option in the development of targeted cancer therapy. The most successful example of this today is the use of the CDK4/6 inhibitor palbociclib combined with aromatase inhibitors for the treatment of estrogen receptor-positive breast cancers. Multiple studies have demonstrated that the CDK-RB-E2F pathway is critical for the control of cell proliferation. More recently, studies have highlighted additional roles of this pathway, especially E2F transcription factors themselves, in tumor progression, angiogenesis and metastasis. Specific E2Fs also have prognostic value in breast cancer, independent of clinical parameters. We discuss here recent advances in understanding of the RB-E2F pathway in breast cancer. We also discuss the application of genome-wide genetic screening efforts to gain insight into synthetic lethal interactions of CDK4/6 inhibitors in breast cancer for the development of more effective combination therapies.

BackgroundA phase II trial of dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin and rituximab (DA-EPOCH-R) from the National Cancer Institute showed promising activity in untreated diffuse large B-cell lymphoma. The Cancer and Leukemia Group B conducted a study to determine if these results could be reproduced in a multi-institutional setting. Design and MethodsThe study included 69 patients with untreated diffuse large B-cell lymphoma at least 18 years of age and at least stage II. Radiaton therapy was not permitted on study. Median age was 58 years (range 23-83) and 40% had high-intermediate or high International Prognostic Index risk. Immunohistochemical biomarkers for cell of origin and proliferation were performed. ResultsWith a median follow up of 62 months, time to progression and overall survival were 81% and 84%, respectively, and time to progression was 87%, 92% and 54% for low/low-intermediate, high-intermediate and high International Prognostic Index risk groups, respectively, at 5-years and beyond. The time to progression and event-free survival of germinal center B-cell lymphoma were 100% and 94%, respectively, and non-germinal center B-cell GCB diffuse large Bcell lymphoma were 67% and 58%, respectively, at 62 months (germinal center vs. non-germinal center B cell P=0.008). DA-EPOCH-R was tolerated without significant grade 4 non-hematologic toxicities. ConclusionsThese results provide the first confirmation by a multi-institutional group that DA-EPOCH-R provides high durable remissions in diffuse large B-cell lymphoma and is effective in both germinal center and non-germinal center B-cell subtypes. The trial was registered at ClinicalTrials.Gov (NCT00032019).Key words: diffuse large B-cell lymphoma, DA-EPOCH-rituximab, untreated, outome, molecular. subtype. Haematologica 2012;97(5):758-765. doi:10.3324/haematol.2011 This is an open-access paper. Citation: Wilson WH, Jung S-H, Porcu P, Hurd D, Johnson J, Martin SE, Czuczman M, Lai R, Said J, Chadburn A, Jones D, Dunleavy K, Canellos G, Zelenetz AD, Cheson BD, and Hsi ED for the Cancer and Leukemia Group B. A Cancer and Leukemia Group B multi-center study of DA-EPOCH-rituximab in untreated diffuse large B-cell lymphoma with analysis of outcome by molecular A Cancer and Leukemia Group B multi-center study of DA-EPOCH-rituximab

The Rb-E2F transcriptional regulatory pathway plays a major role in cell cycle regulation, but its role in invasion and metastasis is less understood. We find that many genes involved in the invasion of cancer cells, such as matrix metalloproteinases, have potential E2F binding sites in their promoters. E2F binding sites were predicted on all 23 human MMP gene promoters, many of which harbored multiple E2F binding sites. Studies presented here show that MMP genes such as MMP9, MMP14, and MMP15 which are overexpressed in non-small cell lung cancer (NSCLC) have multiple E2F binding sites and are regulated by the Rb-E2F pathway. Chromatin immunoprecipitation assays showed the association of E2F1 with the MMP9, MMP14, and MMP15 promoters and transient transfection experiments showed that these promoters are E2F responsive. Correspondingly, depletion of E2F family members by RNAi techniques reduced the expression of these genes with a corresponding reduction in collagen degradation activity. Further, activating Rb by inhibiting the interaction of Raf-1 with Rb using the Rb-Raf-1 disruptor RRD-251 was sufficient to inhibit MMP transcription. This led to reduced invasion and migration of cancer cells in vitro and metastatic foci development in a tail vein lung metastasis model in mice. These results suggest that E2F transcription factors may play a role in promoting metastasis through regulation of MMP genes, and that targeting the Rb-Raf-1 interaction is a promising approach for the treatment of metastatic disease.