Stephen Gately

β-Carboline Compounds, Including Harmine, Inhibit DYRK1A and Tau Phosphorylation at Multiple Alzheimer's Disease-Related Sites

Harmine, a β-carboline alkaloid, is a high affinity inhibitor of the dual specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) protein. The DYRK1A gene is located within the Down Syndrome Critical Region (DSCR) on chromosome 21. We and others have implicated DYRK1A in the phosphorylation of tau protein on multiple sites associated with tau pathology in Down Syndrome and in Alzheimers disease (AD). Pharmacological inhibition of this kinase may provide an opportunity to intervene therapeutically to alter the onset or progression of tau pathology in AD. Here we test the ability of harmine, and numerous additional β-carboline compounds, to inhibit the DYRK1A dependent phosphorylation of tau protein on serine 396, serine 262/serine 356 (12E8 epitope), and threonine 231 in cell culture assays and in vitro phosphorylation assays. Results demonstrate that the β-carboline compounds (1) potently reduce the expression of all three phosphorylated forms of tau protein, and (2) inhibit the DYRK1A catalyzed direct phosphorylation of tau protein on serine 396. By assaying several β-carboline compounds, we define certain chemical groups that modulate the affinity of this class of compounds for inhibition of tau phosphorylation.

Development of potent autophagy inhibitors that sensitize oncogenic BRAF V600E mutant melanoma tumor cells to vemurafenib.

Autophagy is a dynamic cell survival mechanism by which a double-membrane vesicle, or autophagosome, sequesters portions of the cytosol for delivery to the lysosome for recycling. This process can be inhibited using the antimalarial agent chloroquine (CQ), which impairs lysosomal function and prevents autophagosome turnover. Despite its activity, CQ is a relatively inadequate inhibitor that requires high concentrations to disrupt autophagy, highlighting the need for improved small molecules. To address this, we screened a panel of antimalarial agents for autophagy inhibition and chemically synthesized a novel series of acridine and tetrahydroacridine derivatives. Structure-activity relationship studies of the acridine ring led to the discovery of VATG-027 as a potent autophagy inhibitor with a high cytotoxicity profile. In contrast, the tetrahydroacridine VATG-032 showed remarkably little cytotoxicity while still maintaining autophagy inhibition activity, suggesting that both compounds act as autophagy inhibitors with differential effects on cell viability. Further, knockdown of autophagy-related genes showed no effect on cell viability, demonstrating that the ability to inhibit autophagy is separate from the compound cytotoxicity profiles. Next, we determined that both inhibitors function through lysosomal deacidification mechanisms and ultimately disrupt autophagosome turnover. To evaluate the genetic context in which these lysosomotropic inhibitors may be effective, they were tested in patient-derived melanoma cell lines driven by oncogenic BRAF (v-raf murine sarcoma viral oncogene homolog B). We discovered that both inhibitors sensitized melanoma cells to the BRAF V600E inhibitor vemurafenib. Overall, these autophagy inhibitors provide a means to effectively block autophagy and have the potential to sensitize mutant BRAF melanomas to first-line therapies.

Synthesis of improved lysomotropic autophagy inhibitors.

Autophagy is a conserved cellular pathway used to recycle nutrients through lysosomal breakdown basally and under times of stress (e.g., nutrient deprivation, chemotherapeutic treatment). Oncogenes are known to induce autophagy, which may be exploited by cancers for cell survival. To identify autophagy inhibitors with potential therapeutic value for cancer, we screened a panel of antimalarial agents and found that quinacrine (QN) had 60-fold higher potency of autophagy inhibition than chloroquine (CQ), a well-known autophagy inhibitor that functions by disrupting lysosomal activity. Despite desirable autophagy inhibiting properties, QN showed considerable cytotoxicity. Therefore, we designed and synthesized a novel series of QN analogs and investigated their effects on autophagy inhibition and cell viability. Notably, we found two compounds (33 and 34), bearing a backbone of 1,2,3,4-tetrahydroacridine, had limited cytotoxicity yet strong autophagy inhibition properties. In conclusion, these improved lysomotropic autophagy inhibitors may have use as anticancer agents in combination with conventional therapies.

The vitamin E analog, alpha-tocopheryloxyacetic acid enhances the anti-tumor activity of trastuzumab against HER2/neu-expressing breast cancer

BackgroundHER2/neu is an oncogene that facilitates neoplastic transformation due to its ability to transduce growth signals in a ligand-independent manner, is over-expressed in 20-30% of human breast cancers correlating with aggressive disease and has been successfully targeted with trastuzumab (Herceptin®). Because trastuzumab alone achieves only a 15-30% response rate, it is now commonly combined with conventional chemotherapeutic drugs. While the combination of trastuzumab plus chemotherapy has greatly improved response rates and increased survival, these conventional chemotherapy drugs are frequently associated with gastrointestinal and cardiac toxicity, bone marrow and immune suppression. These drawbacks necessitate the development of new, less toxic drugs that can be combined with trastuzumab. Recently, we reported that orally administered alpha-tocopheryloxyacetic acid (α-TEA), a novel ether derivative of alpha-tocopherol, dramatically suppressed primary tumor growth and reduced the incidence of lung metastases both in a transplanted and a spontaneous mouse model of breast cancer without discernable toxicity.MethodsIn this study we examined the effect of α-TEA plus HER2/neu-specific antibody treatment on HER2/neu-expressing breast cancer cells in vitro and in a HER2/neu positive human xenograft tumor model in vivo.ResultsWe show in vitro that α-TEA plus anti-HER2/neu antibody has an increased cytotoxic effect against murine mammary tumor cells and human breast cancer cells and that the anti-tumor effect of α-TEA is independent of HER2/neu status. More importantly, in a human breast cancer xenograft model, the combination of α-TEA plus trastuzumab resulted in faster tumor regression and more tumor-free animals than trastuzumab alone.ConclusionDue to the cancer cell selectivity of α-TEA, and because α-TEA kills both HER2/neu positive and HER2/neu negative breast cancer cells, it has the potential to be effective and less toxic than existing chemotherapeutic drugs when used in combination with HER2/neu antibody.

Identification of novel HDAC inhibitors through cell based screening and their evaluation as potential anticancer agents

A series of benzimidazole based HDAC inhibitors have been rationally designed, synthesized and screened. The SAR of this new chemotype is described. The lead compound, 11e, showed strong activity in several cellular assays and demonstrated in vivo efficacy in mouse xenograft pancreatic cancer models.

Abstract 3698: ODSH, a heparin derivative, enhances the efficacy of gemcitabine in a refractory human pancreatic tumor xenograft model

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL ODSH, a new chemical entity, is 2-0, 3-0 desulfated heparin, a desulfated heparin analog that has been shown to bind to the receptor for advanced glycation endproducts (RAGE). This interaction prevents RAGE from binding to a principal ligand, HMGB1, as well as to other ligands including S-100 calgranulin, which attenuates the activation of RAGE. RAGE activation is known to induce resistance to chemotherapy and promote pancreatic tumor cell survival. We have shown, in vivo, an increase in response with gemcitabine when combined with ODSH. ODSH was tested alone and in combination with standard of care agent, gemcitabine, against BxPC-3 human pancreatic tumor xenograft model. Single agent ODSH and gemcitabine treatment showed an 18.8% and 16.8% decrease in tumor weight, respectively. The combination regimen of ODSH and gemcitabine increased tumor growth inhibition to 37.9%. This decrease was statistically significant (P<0.05) compared to ODSH and gemcitabine treatments alone according to Students t-test. We believe this is a novel approach to treat metastatic pancreatic cancer. ODSH has already shown a favorable safety profile in Phase I and II studies. A clinical trial with ODSH treatment in combination with gemcitabine+nab-paclitaxel in newly diagnosed patients with metastatic pancreatic cancer is underway. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3698. doi:1538-7445.AM2012-3698

Abstract 2922: NDC-1308 inhibits growth of lung and pancreatic tumors in vivo by blocking chromosome replication of cancer cells

Identification of the cellular mechanisms that alter normal cell growth may be exploited for creating new drugs that treat cancers with unmet needs. For example, recent evidence by our group, and others, suggests that proliferation of lung and pancreatic cancer cells may be controlled by the estrogen receptors alpha (ER-alpha) and beta (ER-beta). If accurate, designing drugs that enhance the proposed inhibitory function of ER-beta versus the stimulatory function of ER-alpha, should lead to cessation of cell division and potentially to cell death. We previously demonstrated that an estradiol-like compound, NDC-1308, is cytotoxic to 14 different tumor cell lines in vitro with an EC 50 of 10-20 uM. As predicted, receptor binding studies confirmed that NDC-1308 binds preferentially to ER-beta compared to ER-alpha. A more detailed in vitro analysis showed that NDC-1308 causes a substantial reduction in the transcription of 27 genes involved in chromosomal replication, likely disrupting the cell cycle of the cancer cells. To determine the efficacy of NDC-1308 to kill tumor cells in vivo, xenograft studies were carried out using SCID mice injected with A549 (lung) and BxPC3 (pancreas) tumor cell lines. Mice (N=15 per treatment group) were administered either 8, 16 or 24 mg/kg of NDC-1308 via tail vein injection. Depending on the schedule, the mice were dosed every other day or every third day and the tumor weights followed for two additional weeks after ending treatment. The results show that tumor size was substantially smaller (2 to 3-fold) in NDC-1308 treated animals versus untreated controls. We conclude that intravenous administration of NDC-1308 can cause a cessation of tumor growth in a mouse model of lung and pancreatic cancer. Consistent with the proposed mechanism of action and recent rat pharmacokinetic data (t 1/2 =120min), increasing the dose or decreasing the time between doses enhanced the effect of NDC-1308 on tumor growth in the xenograft model. Future studies will include large animal safety and toxicity studies leading to IND submission and Phase I clinical trials. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2922.