Glioblastoma multiforme (GBM) tumors are highly malignant in nature and despite an aggressive therapy regimen, long–term survival for glioma patients is uncommon as cells with intrinsic or acquired resistance to treatment repopulate the tumor. This creates the need to investigate new therapies for enhancing GBM treatment outside of the standard of care, which includes Temozolomide (TMZ). Our lab focused on two novel strategies to overcome resistance in GBMs. In our first approach, the cellular responses of GBM cell lines to two new TMZ analogues, DP68 and DP86, are reported. The efficacy of these compounds was independent of DNA repair mediated by Methyl Guanine Methyl Transferase (MGMT) and the mismatch repair (MMR) pathway. DP68 or DP86 treated cells do not give rise to secondary spheres, demonstrating that they are no longer capable of self-renewal. DP68-induced damage includes interstrand DNA crosslinks and exhibits a distinct S-phase accumulation before G2/M arrest; a profile that is not observed for TMZ-treated cells. DP68 induces a strong DNA damage response and suppression of FANCD2 expression or ATR expression/kinase activity enhanced the anti-GBM effects of DP68. Collectively, these data demonstrate that DP68, and to a lesser extent DP86, are potent anti-GBM compounds that circumvent TMZ resistance and inhibit recovery of cultures. Our second approach stems from a previous discovery in our lab which demonstrated that the combination of TMZ with Notch inhibition, using a gamma secretase inhibitor (GSI), enhances GBM therapy. Efficacy of TMZ + GSI treatment is partially due to GBM cells shifting into a permanent senescent state. We sought to identify a miR signature that mimics the effects of TMZ + GSI as an alternative vi approach to enhance GBM therapy. MiR-34a expression was highly upregulated in response to TMZ or TMZ + GSI treatment. Exogenous expression of miR-34a revealed that it functions as a tumor suppressor and mimicked the in vitro effects of TMZ + GSI treatment. Additionaly, miR-34a overexpression leads to the downregulation of Notch family members. Together these two studies contribute to our understanding of the complex mechanisms driving resistance in GBM tumors and suggest strategies to develop more effective therapies.

O melanoma maligno é a forma mais agressiva dos tumores cutâneos. Sendo o responsável por mais de 75% das mortes relativas á este tipo de câncer. O principal quimioterápico utilizado no tratamento do melanoma é a dacarbazina (DTIC), entretanto, as taxas de resposta são insatisfatórias. O composto DM-1 é um análogo estrutural da curcumina, e por esta razão possui propriedades biológicas semelhantes, como agente antiproliferativo e próapoptótico. A terapia de captura de nêutrons por boro (BNCT) atua por meio da deposição do isótopo 10Boro nas células tumorais e após a irradiação de nêutrons térmicos há produção de partículas alfa e lítio que destroem a célula. Neste trabalho estudou-se o mecanismo de ação destas três terapias, DTIC, DM-1 e BNCT no tratamento do melanoma e seus efeitos em células normais in vitro com a finalidade de obtenção de modalidades terapêuticas diferentes para o tratamento desta neoplasia. A IC50 foi obtida pela metodologia de MTT, além da análise da progressão do ciclo celular e marcadores de morte celular por citometria de fluxo. O composto DM-1 e a BNCT apresentaram efeito citotóxico seletivo para as linhagens de melanoma, com alta produção de radicais livres peroxidados. Nas mesmas condições, estes efeitos foram mínimos em células normais, diferente do tratamento com DTIC. Houve diminuição da proporção de matriz extracelular e colágeno solúvel sintetizado em células de melanoma tratadas com DM-1, BNCT e DTIC, entretanto, o quimioterápico ocasionou isoladamente diminuição também em células normais. O potencial elétrico mitocondrial das células de melanoma foi diminuído nos três protocolos de tratamento, assim como houve aumento na quantidade de DNA fragmentado. Este efeito não foi encontrado em células normais tratadas com DM-1 e BNCT. O composto DM-1 foi capaz de induzir apoptose via intrínseca e extrínseca, avaliado pela Anexina V e por marcadores de cinética e de morte celular. A terapia de BNCT induziu apoptose e necrose, indicando que esta terapia atua por diferentes vias em cada linhagem celular. BNCT e DM-1 induziram aumento na expressão dos marcados próapoptóticos, como Bax, citocromo c, caspase 3 e 8 clivadas, além de diminuir os valores na expressão de ciclina D1 e Ki-67, relacionados com a progressão do ciclo celular e proliferação. O quimioterápico DTIC apresentou alguns indícios de apoptose em células de melanoma, mas seus efeitos em células normais foram extensivos, ocasionando morte e parada do ciclo celular em melanócitos, células endoteliais e fibroblastos. O composto DM-1 apresentou formação de corpos apoptóticos, modificações no citoesqueleto e clivagem de caspase 9 e Parp em linhagens de melanoma humano. Desta forma, o composto DM-1 e a BNCT mostraram-se ferramentas terapêuticas mais eficazes no controle da progressão e no aumento da morte celular em células de melanoma. O poder efetivo da terapia de BNCT e do composto DM-1 faz com que a possibilidade de terapias combinatórias tenha resultados extremamente favoráveis na modulação da resposta proliferativa desses tumores. / Malignant melanoma is the most aggressive skin cancer. It is responsible for more than 75% of deaths. The main and most active chemotherapy in the melanoma treatment is represented by dacarbazine (DTIC), however, response rates are disappointing. The DM-1 compound is a curcumin structural analogue and it has similar biological properties, such as an antiproliferative and pro-apoptotic agent. Boron Neutron Capture Therapy (BNCT) works through the deposition of the isotope 10Boron in tumor cells, with subsequent irradiation of thermal neutrons, which produce alpha particles and lithium that destroy the cell. In this study, the action mechanism of these three therapies, DTIC, DM-1 and BNCT in the melanoma treatment and its effects in vitro on normal cells were studied in order to obtain different therapeutic modalities for cancer treatment. The IC50 was obtained by MTT method, besides the analysis of cell cycle progression and cell death markers by flow cytometry. The DM-1 and BNCT showed selective cytotoxic in melanoma cell lines, with high of free radicals production. In the same conditions, these effects were minimal in normal cells, unlike the treatment with DTIC. There was a decrease in the proportion of extracellular matrix and soluble collagen synthesized in melanoma cells treated with DM-1, BNCT and DTIC, however, only DTIC also resulted in decreased in normal cells. The mitochondrial electrical potential of melanoma cells was decreased in the three treatment protocols, as there was an increase in the amount of fragmented DNA. This effect was not found in normal cells treated with DM-1 and BNCT. The compound DM-1 was able to induce apoptosis by the intrinsic and extrinsic pathways, as assessed by Annexin V, cell death and kinetic markers. BNCT induced apoptosis and necrosis, indicating that this therapy acts through different pathways in each cell line. DM-1 and BNCT induced an increase of pro-apoptotic markers, such as Bax, cytochrome c, cleaved caspase 3 and 8 expression, and they reduced cyclin D1 and Ki-67, expression related to the progression of the cell cycle and proliferation. The DTIC has shown some signs of apoptosis in melanoma cells, but its effect on normal cells were extensive, causing death and cell cycle arrest in melanocytes, fibroblasts and endothelial cells. The DM-1 showed apoptotic bodies formation, cytoskeleton changes and caspase 9 and Parp cleavage in human melanoma cell lines. Thus, the DM-1 and BNCT showed as therapeutic tools more with high effectiveness in controlling the cell cycle progression and cell death increase in melanoma cells. The effectiveness of BNCT and DM-1 makes the possibility of combinatorial therapies, with extremely favorable results in the modulation of the proliferative response of these tumors.

O melanoma maligno é a forma mais agressiva dos tumores cutâneos. Sendo o responsável por mais de 75% das mortes relativas á este tipo de câncer. O principal quimioterápico utilizado no tratamento do melanoma é a dacarbazina (DTIC), entretanto, as taxas de resposta são insatisfatórias. O composto DM-1 é um análogo estrutural da curcumina, e por esta razão possui propriedades biológicas semelhantes, como agente antiproliferativo e próapoptótico. A terapia de captura de nêutrons por boro (BNCT) atua por meio da deposição do isótopo 10Boro nas células tumorais e após a irradiação de nêutrons térmicos há produção de partículas alfa e lítio que destroem a célula. Neste trabalho estudou-se o mecanismo de ação destas três terapias, DTIC, DM-1 e BNCT no tratamento do melanoma e seus efeitos em células normais in vitro com a finalidade de obtenção de modalidades terapêuticas diferentes para o tratamento desta neoplasia. A IC50 foi obtida pela metodologia de MTT, além da análise da progressão do ciclo celular e marcadores de morte celular por citometria de fluxo. O composto DM-1 e a BNCT apresentaram efeito citotóxico seletivo para as linhagens de melanoma, com alta produção de radicais livres peroxidados. Nas mesmas condições, estes efeitos foram mínimos em células normais, diferente do tratamento com DTIC. Houve diminuição da proporção de matriz extracelular e colágeno solúvel sintetizado em células de melanoma tratadas com DM-1, BNCT e DTIC, entretanto, o quimioterápico ocasionou isoladamente diminuição também em células normais. O potencial elétrico mitocondrial das células de melanoma foi diminuído nos três protocolos de tratamento, assim como houve aumento na quantidade de DNA fragmentado. Este efeito não foi encontrado em células normais tratadas com DM-1 e BNCT. O composto DM-1 foi capaz de induzir apoptose via intrínseca e extrínseca, avaliado pela Anexina V e por marcadores de cinética e de morte celular. A terapia de BNCT induziu apoptose e necrose, indicando que esta terapia atua por diferentes vias em cada linhagem celular. BNCT e DM-1 induziram aumento na expressão dos marcados próapoptóticos, como Bax, citocromo c, caspase 3 e 8 clivadas, além de diminuir os valores na expressão de ciclina D1 e Ki-67, relacionados com a progressão do ciclo celular e proliferação. O quimioterápico DTIC apresentou alguns indícios de apoptose em células de melanoma, mas seus efeitos em células normais foram extensivos, ocasionando morte e parada do ciclo celular em melanócitos, células endoteliais e fibroblastos. O composto DM-1 apresentou formação de corpos apoptóticos, modificações no citoesqueleto e clivagem de caspase 9 e Parp em linhagens de melanoma humano. Desta forma, o composto DM-1 e a BNCT mostraram-se ferramentas terapêuticas mais eficazes no controle da progressão e no aumento da morte celular em células de melanoma. O poder efetivo da terapia de BNCT e do composto DM-1 faz com que a possibilidade de terapias combinatórias tenha resultados extremamente favoráveis na modulação da resposta proliferativa desses tumores. / Malignant melanoma is the most aggressive skin cancer. It is responsible for more than 75% of deaths. The main and most active chemotherapy in the melanoma treatment is represented by dacarbazine (DTIC), however, response rates are disappointing. The DM-1 compound is a curcumin structural analogue and it has similar biological properties, such as an antiproliferative and pro-apoptotic agent. Boron Neutron Capture Therapy (BNCT) works through the deposition of the isotope 10Boron in tumor cells, with subsequent irradiation of thermal neutrons, which produce alpha particles and lithium that destroy the cell. In this study, the action mechanism of these three therapies, DTIC, DM-1 and BNCT in the melanoma treatment and its effects in vitro on normal cells were studied in order to obtain different therapeutic modalities for cancer treatment. The IC50 was obtained by MTT method, besides the analysis of cell cycle progression and cell death markers by flow cytometry. The DM-1 and BNCT showed selective cytotoxic in melanoma cell lines, with high of free radicals production. In the same conditions, these effects were minimal in normal cells, unlike the treatment with DTIC. There was a decrease in the proportion of extracellular matrix and soluble collagen synthesized in melanoma cells treated with DM-1, BNCT and DTIC, however, only DTIC also resulted in decreased in normal cells. The mitochondrial electrical potential of melanoma cells was decreased in the three treatment protocols, as there was an increase in the amount of fragmented DNA. This effect was not found in normal cells treated with DM-1 and BNCT. The compound DM-1 was able to induce apoptosis by the intrinsic and extrinsic pathways, as assessed by Annexin V, cell death and kinetic markers. BNCT induced apoptosis and necrosis, indicating that this therapy acts through different pathways in each cell line. DM-1 and BNCT induced an increase of pro-apoptotic markers, such as Bax, cytochrome c, cleaved caspase 3 and 8 expression, and they reduced cyclin D1 and Ki-67, expression related to the progression of the cell cycle and proliferation. The DTIC has shown some signs of apoptosis in melanoma cells, but its effect on normal cells were extensive, causing death and cell cycle arrest in melanocytes, fibroblasts and endothelial cells. The DM-1 showed apoptotic bodies formation, cytoskeleton changes and caspase 9 and Parp cleavage in human melanoma cell lines. Thus, the DM-1 and BNCT showed as therapeutic tools more with high effectiveness in controlling the cell cycle progression and cell death increase in melanoma cells. The effectiveness of BNCT and DM-1 makes the possibility of combinatorial therapies, with extremely favorable results in the modulation of the proliferative response of these tumors.

My thesis research began with a project in which we were trying to determine the function of embryonic stem cell (ESC)-specific miRNAs. Using luciferase constructs containing miRNA binding sites, luciferase expression was inhibited by endogenous miRNAs in ESCs, and by exogenous miRNAs in HeLa cells. Inhibition of luciferase expression by miRNAs was inhibited in HeLa cells using 2’O-methyl-oligonucleotides. In ESCs, 2’O-methyl-oligonucleotides were only effective in partially inhibiting miR290 function. Partial inhibition of miR290 did not result in any obvious phenotypic changes in mESCs. Later studies using 2’O-methyl-oligonucleotides in ESCs were also unsuccessful. The function of ESC-specific miRNAs has since been studied by re-introducing miRNAs into Dicer -/- cells which cannot make miRNAs. These studies have shown that ESC-specific miRNAs are involved in de novo DNA methylation, self-renewal, and cell-cycle regulation. Newly diagnosed glioblastoma (GBM) patients rarely survive more than two years even after surgery, radiotherapy, and chemotherapy using temozolomide (TMZ) or 1,3-bis(2-chloroethy)-1-nitrosourea (BCNU). Eventual regrowth of the tumor indicates that some tumor cells are resistant to therapy. GBM neurosphere-initiating cells (NICs) are thought to be similar to tumor-initiating cells in vivo, and will form invasive tumors in mice, making neurosphere cultures a good model system for studying GBMs. To test whether GBM NICs were resistant to chemotherapy, we used a neurosphere formation assay to measure the number of proliferating NICs in the presence of TMZ or BCNU. The concentrations of chemotherapy drugs required to inhibit neurosphere formation were much less than those required to inhibit bulk cell proliferation or to induce cell death in our neurosphere cultures. For some cultures, there was a robust recovery of neurosphere formation after chemotherapy treatment which appeared to be DNA damage independent. Some of the cultures that showed significant recovery of neurosphere formation underwent reversible cell cycle arrest, possibly reducing chemotoxicity in these cultures. Collectively, these results indicate that GBM neurosphere cultures can regrow after being treated with clinically relevant doses of chemotherapy drugs. Chemotherapy-treated neurosphere cultures remained viable, and formed tumors when injected into mice. Our experiments show that these in vitro assays may be useful in predicting in vivo responses to chemotherapeutic agents.

Glioma therapy relies on induction of cytotoxicity; however, the current combination of surgery, irradiation (IR) and temozolomide (TMZ) treatment does not result in a long-term cure. Our lab previously demonstrated that a small population of glioma cells enters a transient cell cycle arrest in response to chemotherapy. Treatment with TMZ significantly decreases initial neurosphere formation; however, after a short recovery period, a small number of cells resume neurosphere formation and repopulate the culture. This recovery of neurosphere growth recapitulates the inevitable glioma recurrence in the clinic. The focus of our laboratory is to study direct-target therapies that can be combined with TMZ to inhibit neurosphere recovery. The Notch pathway is a promising target because it is involved in cell growth and survival. Here, we demonstrate that blocking the Notch pathway using gamma-secretase inhibitors (GSIs) enhances TMZ treatment. The combination of TMZ and GSI treatments targets the cells capable of recovery. TMZ + GSI treated cells do not recover and are no longer capable of self-renewal. Interestingly, recovery is inhibited when the GSI is administered 24 hrs after TMZ treatment, demonstrating a sequence-dependent mechanism. TMZ + GSI treatment also decreases tumorigenicity. When glioma cell lines were treated in vitro and implanted in NU/NU nude mice, TMZ + GSI treatment extended latency and greatly increased survival. In addition, in vivo TMZ + GSI treatment completely blocked tumor progression and resulted in the loss of a palpable tumor in 50% of mice, while none of the TMZ-only treated mice survived. TMZ + GSI treated cultures and xenografts display a senescent phenotype. Cultures treated with TMZ + GSI have decreased proliferation, but no increase in cell death. We observed an increase in the number of cells expressing senescence-associated β-galactosidase in vitro and in vivo. This demonstrates that inhibition of the Notch pathway shifts TMZ-treated cells from a transient cell cycle arrest into a permanent senescent state. Senescent cells can stimulate the innate immune system. Here we demonstrate that TMZ + GSI treatment increases phagocytosis in vitro. New therapy combinations, such as TMZ + GSI, are arising in the field of therapy-induced senescence (TIS). Overall, this data demonstrates the importance of the Notch pathway in chemoprotection and maintenance of TMZ-treated gliomas. The addition of GSIs to current treatments is a promising target-directed therapy to decrease the rate of brain tumor recurrence by inducing senescence and tumor clearance.

Glioblastoma multiforme (GBM) is a deadly grade IV brain tumor characterized by a heterogeneous population of cells that are drug resistant, aggressive, and infiltrative. The current standard of care, which has not changed in over a decade, only provides GBM patients with 12-14 months survival post diagnosis. We asked if the addition of a novel endoplasmic reticulum (ER) stress inducing agent, JLK1486, to the standard chemotherapy, temozolomide (TMZ), which induces DNA double strand breaks (DSBs), would enhance TMZ’s efficacy. Because GBMs rely on the ER to mitigate their hypoxic environment and DNA repair to fix TMZ induced DSBs, we reasoned that DSBs occurring during heightened ER stress would be deleterious. Treatment of GBM cells with TMZ+JLK1486 decreased cell viability and increased cell death due to apoptosis. We found that TMZ+JLK1486 prolonged ER stress induction, as indicated by elevated ER stress marker BiP, ATF4, and CHOP, while sustaining activation of the DNA damage response pathway. This combination produced unresolved DNA DSBs due to RAD51 reduction, a key DNA repair factor. The combination of TMZ+JLK1486 is a potential novel therapeutic combination and suggests an inverse relationship between ER stress and DNA repair pathways.

No description available.

This study aims at tackling some of the problems often encountered in photostability testing and liquid formulation development. Three anti-cancer drugs will be employed as models; Dacarbazine (DBZ) has well established photostability issues, Axitinib (AXI) and Sunitinib (SUT) are two new drugs only commercially available in solid dosage forms. In ethanol, the photokinetics of these drugs were well described by the newly proposed Φ-order kinetic mathematical model. This has confirmed the photoreversible character of AXI and SUT’s and unimolecular photoreaction of DBZ’s photodegradations. Also, the Φ-order kinetics is proven to describe them better than the usually used classic thermal reaction orders. In aqueous solution, the drugs were found to undergo thermal and photochemical complex degradations, involving at least 3 photoproducts. A new photokinetic approach has been proposed in this work to solving and unravelling the attributes of such complex mechanisms. For the first time, the quantum yields (QY) of the three drugs were determined and found to increase with irradiation wavelength. SUT’s QY were comparable in ethanol and water (QY460 = 0.02), DBZ was found to be more photoefficient in water (QY330 = 0.04 and 0.1, respectively) and AXI in water (QY330 = 0.06 and 0.03). Φ-order kinetics’ potential for the development of reliable actinometers of the three drugs, without prior knowledge of unknown reaction parameters, has also been established. A general equation to describe the isotherm of a (Gn:Hm) guest-host multicomponent complex was proposed in this work to palliate the lack of a strategy for characterising nanosponge-drug complexes. It provides information on both stiochiometry and association constant of the complex. The results indicate that hydrophobic AXI forms a 1:0.8 complex, indicating the possibility of multiple association sites and/or different types of binding. The newly developed AXI/nanosponge liquid formulation has significantly increased solubility (5000-fold) and thermal stability. Furthermore, the photostability of DBZ and SUT were considerably improved by using a strategy based on light-absorption competitors. Their initial velocities reduced from 10 and 3 s-1 (respectively) to 1 and 0.13 s-1. The successful application of these methods to the model anti-cancer drugs has set out new approaches that might be found useful for future treatments of photodegradation data, development of drug-actinometers and liquid formulations of drugs.