Yin Yang 1 contains G-quadruplex structures in its promoter and 5'-UTR and its expression is modulated by G4 resolvase 1.

Yin Yang 1 (YY1) is a multifunctional protein with regulatory potential in tumorigenesis. Ample studies demonstrated the activities of YY1 in regulating gene expression and mediating differential protein modifications. However, the mechanisms underlying YY1 gene expression are relatively understudied. G-quadruplexes (G4s) are four-stranded structures or motifs formed by guanine-rich DNA or RNA domains. The presence of G4 structures in a gene promoter or the 5'-UTR of its mRNA can markedly affect its expression. In this report, we provide strong evidence showing the presence of G4 structures in the promoter and the 5'-UTR of YY1. In reporter assays, mutations in these G4 structure forming sequences increased the expression of Gaussia luciferase (Gluc) downstream of either YY1 promoter or 5'-UTR. We also discovered that G4 Resolvase 1 (G4R1) enhanced the Gluc expression mediated by the YY1 promoter, but not the YY1 5'-UTR. Consistently, G4R1 binds the G4 motif of the YY1 promoter in vitro and ectopically expressed G4R1 increased endogenous YY1 levels. In addition, the analysis of a gene array data consisting of the breast cancer samples of 258 patients also indicates a significant, positive correlation between G4R1 and YY1 expression.

The poison oligonucleotide F10 is highly effective against acute lymphoblastic leukemia while sparing normal hematopoietic cells.

F10 is an oligonucleotide based on the thymidylate synthase (TS) inhibitory 5-fluorouracil (5-FU) metabolite, 5-fluoro-2'-deoxyuridine-5'-O-monophosphate. We sought to determine the activity of F10 against preclinical models of acute lymphoblastic leukemia (ALL). F10 treatment resulted in robust induction of apoptosis that could not be equaled by 100 fold more 5-FU. F10 was more potent than Ara-C and doxorubicin against a panel of murine and human ALL cells with an average IC50 value of 1.48 nM (range 0.07 to 5.4 nM). F10 was more than 1000 times more potent than 5-FU. In vivo, F10 treatment significantly increased survival in 2 separate syngeneic ALL mouse models and 3 separate xenograft models. F10 also protected mice from leukemia-induced weight loss. In ALL cells made resistant to Ara-C, F10 remained highly active in vitro and in vivo. Using labeled F10, uptake by the ALL cell lines DG75 and SUP-B15 was rapid and profoundly temperature-dependent. Both cell lines demonstrated increased uptake compared to normal murine lineage- depleted marrow cells. Consistent with this decreased uptake, F10 treatment did not alter the ability of human hematopoietic stem cells to engraft in immunodeficient mice.

Inhibition of GSK-3ß activity can result in drug and hormonal resistance and alter sensitivity to targeted therapy in MCF-7 breast cancer cells.

The PI3K/Akt/mTORC1 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance, and metastasis. One molecule regulated by this pathway is GSK-3ß. GSK-3ß is phosphorylated by Akt on S9, which leads to its inactivation; however, GSK-3ß also can regulate the activity of the PI3K/Akt/mTORC1 pathway by phosphorylating molecules such as PTEN, TSC2, p70S6K, and 4E-BP1. To further elucidate the roles of GSK-3ß in chemotherapeutic drug and hormonal resistance of MCF-7 breast cancer cells, we transfected MCF-7 breast cancer cells with wild-type (WT), kinase-dead (KD), and constitutively activated (A9) forms of GSK-3ß. MCF-7/GSK-3ß(KD) cells were more resistant to doxorubicin and tamoxifen compared with either MCF-7/GSK-3ß(WT) or MCF-7/GSK-3ß(A9) cells. In the presence and absence of doxorubicin, the MCF-7/GSK-3ß(KD) cells formed more colonies in soft agar compared with MCF-7/GSK-3ß(WT) or MCF-7/GSK-3ß(A9) cells. In contrast, MCF-7/GSK-3ß(KD) cells displayed an elevated sensitivity to the mTORC1 blocker rapamycin compared with MCF-7/GSK-3ß(WT) or MCF-7/GSK-3ß(A9) cells, while no differences between the 3 cell types were observed upon treatment with a MEK inhibitor by itself. However, resistance to doxorubicin and tamoxifen were alleviated in MCF-7/GSK-3ß(KD) cells upon co-treatment with an MEK inhibitor, indicating regulation of this resistance by the Raf/MEK/ERK pathway. Treatment of MCF-7 and MCF-7/GSK-3ß(WT) cells with doxorubicin eliminated the detection of S9-phosphorylated GSK-3ß, while total GSK-3ß was still detected. In contrast, S9-phosphorylated GSK-3ß was still detected in MCF-7/GSK-3ß(KD) and MCF-7/GSK-3ß(A9) cells, indicating that one of the effects of doxorubicin on MCF-7 cells was suppression of S9-phosphorylated GSK-3ß, which could result in increased GSK-3ß activity. Taken together, these results demonstrate that introduction of GSK-3ß(KD) into MCF-7 breast cancer cells promotes resistance to doxorubicin and tamoxifen, but sensitizes the cells to mTORC1 blockade by rapamycin. Therefore GSK-3ß is a key regulatory molecule in sensitivity of breast cancer cells to chemo-, hormonal, and targeted therapy.

A phase I study of the first-in-class antimitochondrial metabolism agent, CPI-613, in patients with advanced hematologic malignancies.

PURPOSE: The lipoate derivative CPI-613 is a first-in-class agent that targets mitochondrial metabolism. This study determined the effects of CPI-613 on mitochondrial function and defined the MTD, pharmacokinetics, and safety in patients with relapsed or refractory hematologic malignancies. EXPERIMENTAL DESIGN: Human leukemia cell lines were exposed to CPI-613 and mitochondrial function was assayed. A phase I trial was conducted in which CPI-613 was given as a 2-hour infusion on days 1 and 4 for 3 weeks every 28 days. RESULTS: CPI-613 inhibited mitochondrial respiration of human leukemia cells consistent with the proposed mechanism of action. In the phase I trial, 26 patients were enrolled. CPI-613 was well tolerated with no marrow suppression observed. When the infusion time was shortened to 1 hour, renal failure occurred in 2 patients. At 3,780 mg/m(2), there were two dose-limiting toxicities (DLT). At a dose of 2,940 mg/m(2) over 2 hours, no DLTs were observed, establishing this as the MTD. Renal failure occurred in a total of 4 patients and resolved in all but 1, who chose hospice care. CPI-613 has a triphasic elimination with an alpha half-life of approximately 1.34 hours. Of the 21 evaluable, heavily pretreated patients, 4 achieved an objective response and 2 achieved prolonged stabilization of disease for a clinical benefit rate of 29%. Following drug exposure, gene expression profiles of peripheral blood mononuclear cells from responders demonstrated immune activation. CONCLUSION: CPI-613 inhibits mitochondrial function and demonstrates activity in a heavily pretreated cohort of patients.

Deregulation of the EGFR/PI3K/PTEN/Akt/mTORC1 pathway in breast cancer: possibilities for therapeutic intervention.

The EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance and metastasis. The expression of this pathway is frequently altered in breast cancer due to mutations at or aberrant expression of: HER2, ERalpha, BRCA1, BRCA2, EGFR1, PIK3CA, PTEN, TP53, RB as well as other oncogenes and tumor suppressor genes. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway and upstream HER2 has been associated with breast cancer initiating cells (CICs) and in some cases resistance to treatment. The anti-diabetes drug metformin can suppress the growth of breast CICs and herceptin-resistant HER2+ cells. This review will discuss the importance of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway primarily in breast cancer but will also include relevant examples from other cancer types. The targeting of this pathway will be discussed as well as clinical trials with novel small molecule inhibitors. The targeting of the hormone receptor, HER2 and EGFR1 in breast cancer will be reviewed in association with suppression of the EGFR/PI3K/PTEN/Akt/mTORC1/GSK-3 pathway.

Involvement of Akt-1 and mTOR in sensitivity of breast cancer to targeted therapy.

Elucidating the response of breast cancer cells to chemotherapeutic and hormonal based drugs is clearly important as these are frequently used therapeutic approaches. A signaling pathway often involved in chemo- and hormonal-resistance is the Ras/PI3K/PTEN/Akt/mTOR cascades. In the studies presented in this report, we have examined the effects of constitutive activation of Akt on the sensitivity of MCF-7 breast cancer cells to chemotherapeutic- and hormonal-based drugs as well as mTOR inhibitors. MCF-7 cells which expressed a constitutively-activated Akt-1 gene [∆Akt-1(CA)] were more resistant to doxorubicin, etoposide and 4-OH-tamoxifen (4HT) than cells lacking ∆Akt-1(CA). Cells which expressed ∆Akt-1(CA) were hypersensitive to the mTOR inhibitor rapamycin. Furthermore, rapamycin lowered the IC50s for doxorubicin, etoposide and 4HT in the cells which expressed ∆Akt-1(CA), demonstrating a potential improved method for treating certain breast cancers which have deregulated PI3K/PTEN/Akt/mTOR signaling. Understanding how breast cancers respond to chemo- and hormonal-based therapies and the mechanisms by which they can become drug resistant may enhance our ability to treat breast cancer. These results also document the potential importance of knowledge of the mutations present in certain cancers which may permit more effective therapies.

Akt as a therapeutic target in cancer.

BACKGROUND: The phosphatidylinositol 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/v-akt murine thymoma viral oncogene homolog (Akt)/mammalian target of rapamycin (mTOR) pathway is central in the transmission of growth regulatory signals originating from cell surface receptors. OBJECTIVE: This review discusses how mutations occur that result in elevated expression the PI3K/PTEN/Akt/mTOR pathway and lead to malignant transformation, and how effective targeting of this pathway may result in suppression of abnormal growth of cancer cells. METHODS: We searched the literature for articles which dealt with altered expression of this pathway in various cancers including: hematopoietic, melanoma, non-small cell lung, pancreatic, endometrial and ovarian, breast, prostate and hepatocellular. RESULTS/CONCLUSIONS: The PI3K/PTEN/Akt/mTOR pathway is frequently aberrantly regulated in various cancers and targeting this pathway with small molecule inhibitors and may result in novel, more effective anticancer therapies.