The discovery of G-rich oligonucleotides (GROs) that have non-antisense antiproliferative activity against a number of cancer cell lines has been recently described. This biological activity of GROs was found to be associated with their ability to form stable G-quartet-containing structures and their binding to a specific cellular protein, most likely nucleolin (Bates, P. J., Kahlon, J. B., Thomas, S. D., Trent, J. O., and Miller, D. M. (1999) J. Biol. Chem. 274, 26369 -26377). In this report, we further investigate the novel mechanism of GRO activity by examining their effects on cell cycle progression and on nucleic acid and protein biosynthesis. Cell cycle analysis of several tumor cell lines showed that cells accumulate in S phase in response to treatment with an active GRO. Analysis of 5-bromodeoxyuridine incorporation by these cells indicated the absence of de novo DNA synthesis, suggesting an arrest of the cell cycle predominantly in S phase. At the same time point, RNA and protein synthesis were found to be ongoing, indicating that arrest of DNA replication is a primary event in GRO-mediated inhibition of proliferation. This specific blockade of DNA replication eventually resulted in altered cell morphology and induction of apoptosis. To characterize further GRO-mediated inhibition of DNA replication, we used an in vitro assay based on replication of SV40 DNA. GROs were found to be capable of inhibiting DNA replication in the in vitro assay, and this activity was correlated to their antiproliferative effects. Furthermore, the effect of GROs on DNA replication in this assay was related to their inhibition of SV40 large T antigen helicase activity. The data presented suggest that the antiproliferative activity of GROs is a direct result of their inhibition of DNA replication, which may result from modulation of a replicative helicase activity.Oligonucleotides can recognize both nucleic acids and proteins with a high degree of specificity. This is a major reason why they have been widely investigated as potential therapeutic agents for cancer, viral infections, and inflammatory diseases. Oligonucleotides can achieve target recognition by sequence-specific interactions with nucleic acids or proteins such as in the antisense, antigene, or decoy approaches (1-4). Alternatively, target recognition can be due to the specific threedimensional structure of an oligonucleotide, as in the aptamer approach (5, 6). These aptameric oligonucleotides often contain secondary structure elements such as hairpins or G-quartets. The formation of G-quartet structures is also thought to contribute to non-antisense growth inhibitory effects of G-rich phosphodiester and phosphorothioate oligonucleotides (7-9).Recently, we reported (9) on a novel class of phosphodiester G-rich oligonucleotides (GROs) 1 that could strongly inhibit the in vitro proliferation of tumor cells derived from prostate, breast, and cervical carcinomas. The antiproliferative GROs were able to form stable secondary structures consistent with G-quartet format...

Shp2 tyrosine phosphatase plays a critical role in hematopoiesis, and dominant active mutations have been detected in the human gene PTPN11, encoding Shp2, in child leukemia patients. We report here that although no such mutations were detected in 44 adult leukemia patients screened, Shp2 expression levels were significantly elevated in primary leukemia cells and leukemia cell lines, as compared with normal hematopoietic progenitor cells. The Shp2 protein amounts correlated well with the hyperproliferative capacity but were inversely associated with the differentiation degree of leukemia cells. Suppression of Shp2 expression induced apoptosis and inhibition of leukemic cell clonogenic growth. Notably, the majority of Shp2 was preferentially localized to the plasma membrane and was constitutively phosphorylated on tyrosine in leukemia cells, and also in normal hematopoietic cells following mitogenic stimulation. Based on these results, we propose that aberrantly increased expression of Shp2 may contribute, collaboratively with other factors, to leukemogenesis. IntroductionThe Src homology 2 (SH2) domain containing phosphotyrosine phosphatase 2 (Shp2), a ubiquitously expressed enzyme, plays a crucial role in normal hematopoietic cell development. [1][2][3] In vitro hematopoietic differentiation assay showed a severe suppression of erythroid/myeloid progenitor cell development from homozygous mutant (Shp2 ⌬46-110 ) embryonic stem (ES) cells. 1 Consistently, neither erythroid nor myeloid progenitor cells of Shp2 ⌬46-110 origin were detectable in the fetal liver or bone marrow of chimeric animals that were derived from aggregation of mutant ES cells and wild-type embryos, although a significant contribution of mutant cells was observed in a few other organs or tissue of the chimeras. 2 Subsequent experiments using the Rag-2 (recombination activating protein-2)-deficient blastocyst complementation assay demonstrated a function of Shp2 for lymphopoiesis in a cell-autonomous manner, and differentiation of lymphoid cell lineages in Shp2 Ϫ/Ϫ / Rag-2 Ϫ/Ϫ chimeric mice was blocked before pro-T-and pro-B-cell stages. 4 Together, these observations suggest a stringent requirement for a functional Shp2 in normal hematopoietic cell development in mammals.Upon stimulation of factor-dependent cell lines with interleukin-6 (IL-6), leukemia inhibitory factor (LIF), IL-3/granulocyte macrophage-colony-stimulating factor (GM-CSF), or erythropoietin (Epo), Shp2 rapidly becomes tyrosine-phosphorylated. 5,6 Cells expressing a mutant gp130 that results in elimination of tyrosine phosphorylation fail to proliferate upon ligand stimulation. 7 Shp2 appears to play a positive role in activation of Akt and Erk signaling pathways, which promote cell proliferation/ survival and block cell apoptosis, critical events in tumorigenesis. [8][9][10] Functional analysis suggested that Shp2 may act in both catalytic-dependent and -independent manners in mediating IL-3-stimulated proliferation and survival of hematopoietic cells. 11 Several studies have...

Bcr-Abl tyrosine kinase inhibitors (TKIs) have been a remarkable success for the treatment of Ph ؉ chronic myeloid leukemia (CML). However, a significant proportion of patients treated with TKIs develop resistance because of leukemia stem cells (LSCs) and T315I mutant Bcr-Abl. Here we describe the unknown activity of the natural product berbamine that efficiently eradicates LSCs and T315I mutant BcrAbl clones. Unexpectedly, we identify CaMKII ␥ as a specific and critical target of berbamine for its antileukemia activity. Berbamine specifically binds to the ATPbinding pocket of CaMKII ␥, inhibits its phosphorylation and triggers apoptosis of leukemia cells. More importantly, CaMKII ␥ is highly activated in LSCs but not in normal hematopoietic stem cells and coactivates LSC-related ␤-catenin and Stat3 signaling networks. The identification of CaMKII ␥ as a specific target of berbamine and as a critical molecular switch regulating multiple LSC-related signaling pathways can explain the unique antileukemia activity of berbamine. These findings also suggest that berbamine may be the first ATP-competitive inhibitor of CaMKII ␥, and potentially, can serve as a new type of molecular targeted agent through inhibition of the CaMKII ␥ activity for treatment of leukemia. (Blood. 2012; 120(24):4829-4839) IntroductionChronic myeloid leukemia (CML), which accounts for approximately 20% of all adult leukemias, 1 is characterized by the presence of the Philadelphia chromosome (Ph ϩ ), which results from a chromosomal translocation between the Bcr gene on chromosome 22 and the Abl gene on chromosome 9. 2 This translocation produces the fusion protein Bcr-Abl that has constitutive kinase activity 3 and is essential for the growth of CML cells and has become an attractive target for treatment of Ph ϩ CML cases, and the Abl tyrosine kinase inhibitors (TKIs) are now first-line therapeutic agents. [4][5][6] Inhibition of Bcr-Abl with Abl tyrosine kinase inhibitors (TKIs), such as imatinib (IM), is highly effective in controlling CML at chronic phase but not curing the disease. This is largely because of the inability of these kinase inhibitors to kill leukemia stem cells (LSCs) responsible for initiation, drug resistance, and relapse of CML 4-6 and Bcr-Abl gene mutation, particularly T315I mutant Bcr-Abl clones. 7-9 Thus, drug resistance associated with TKIs has created a need for more potent and safer therapies against other targets apart from the Bcr-Abl oncogenic kinase.Increasing evidence shows that traditional Chinese medicine (TCM) products not only play important roles in the discovery and development of drugs, but can also be used as molecular probes for identifying therapeutic targets. Homoharringtonine, arsenic trioxide, and triptolide are 3 famous examples. 9-11 Berbamine (BBM) is a structurally unique bisbenzylisoquinoline isolated from TCM Berberis amurensis, and has been used in traditional Chinese medicine for treating a variety of diseases from inflammation to tumors for many years. 12,13 It possesses a unique profile ...