Chemosensitization of carcinoma cells using epithelial cell adhesion molecule-targeted liposomal antisense against bcl-2/bcl-xL

Nanoscale drug delivery systems, such as sterically stabilized immunoliposomes binding to internalizing tumor-associated antigens, can increase therapeutic efficacy and reduce toxicity to normal tissues compared with nontargeted liposomes. The epithelial cell adhesion molecule (EpCAM) is of interest as a ligand for targeted drug delivery because it is abundantly expressed in solid tumors but shows limited distribution in normal tissues. To generate EpCAM-specific immunoliposomes for targeted cancer therapy, the humanized single-chain Fv antibody fragment 4D5MOCB was covalently linked to the exterior of coated cationic liposomes. As anticancer agent, we encapsulated the previously described antisense oligonucleotide 4625 specific for both bcl-2 and bcl-xL. The EpCAM-targeted immunoliposomes (SIL25) showed specific binding to EpCAM-overexpressing tumor cells, with a 10- to 20-fold increase in binding compared with nontargeted control liposomes. No enhanced binding was observed on EpCAM-negative control cells. On cell binding, SIL25 was efficiently internalized by receptor-mediated endocytosis, ultimately leading to down-regulation of both bcl-2 and bcl-xL expression on both the mRNA and protein level, which resulted in enhanced tumor cell apoptosis. In combination experiments, the use of SIL25 led to a 2- to 5-fold sensitization of EpCAM-positive tumor cells of diverse origin to death induction by doxorubicin. Our data show the promise of EpCAM-specific drug delivery systems, such as antisense-loaded immunoliposomes, for targeted cancer therapy.

Effects of butyrate on the colon cancer cell phenotype-chemosensitization and upregulation of proteins implicated in cancer progression

Colon cancer is the second leading cause of cancer mortality in the U.S. Surgery is the only truly effective human colon cancer (HCC) therapy due to marked intrinsic drug resistance. The inefficacy of therapies developed for metastatic HCC suggests that advances in colon cancer chemoprevention and chemotherapy will be needed to reduce HCC mortality. The dietary fiber metabolite butyrate (NaB) is a candidate cancer chemopreventive agent that inhibits growth, promotes differentiation and stimulates apoptosis of HCC cells. Epidemiological and experimental studies suggest that dietary fiber protects against the development of HCC, however, recent large prospective trials have not found significant protection. ^ The first central hypothesis of this dissertation project is that the diversity of phenotypic changes induced by NaB in HCC cells includes molecular alterations that oppose its chemopreventive action and thereby limit its efficacy. We investigated the effect of NaB on the expression/activity of epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) in HCC HT29 cells. NaB treatment induced a 13-fold increase in EGFR expression in concert with its chemopreventive action in vitro, i.e., induction of growth suppression and G1 arrest, apoptosis and a differentiated phenotype. NaB-induced EGFR was active based on multiple lines of evidence. The EGFR was: (1) heavily phosphorylated at Tyrosine (P-Tyr); (2) associated with the cytoskeleton; (3) localized at the cell surface, and activated in response to EGF; and (4) NaB treatment of the cells induced activation of the EGFR effector Erk1/2. NaB treatment also induced a 7-fold increase in COX-2 expression. The NaB-induced COX-2 was active based on significantly increased PGE2 production. ^ The second central hypothesis is that NaB treatment would render HCC cells more chemosensitive to chemotherapy agents based on the increased apoptotic index induced by NaB. NaB treatment chemosensitized HT29 cells to 5-FU and doxorubicin, despite increases in the expression of P-glycoprotein and a related drug resistance protein (MRP). ^ These results raise the intriguing possibility that the chemopreventive effects of fiber may require concomitant treatment with EGFR and/or COX-2 inhibitors. Similarly, NaB may be a rational drug to combine with existing chemotherapeutic agents for the management of advanced HCC patients. ^

CHEMOSENSITIZATION OF HEPATOCELLULAR CARCINOMA TO GEMCITABINE BY NON-INVASIVE RADIOFREQUENCY FIELD-INDUCED HYPERTHERMIA

Gemcitabine is a potent nucleoside analogue against solid tumors however drug resistance rapidly emerges. Removal of gemcitabine incorporated in the DNA by repair mechanisms could potentially contribute to resistance in chemo-refractory solid tumors. In this study, we evaluated homologous recombination repair of gemcitabine-stalled replication forks as a potential mechanism contributing to resistance. We also studied the effect of hyperthermia on homologous recombination pathway to explain the previously reported synergy between gemcitabine and hyperthermia. We found that hyperthermia degrades and inhibits localization of Mre11 to gemcitabine-stalled replication forks. Furthermore, gemcitabine-treated cells that were also treated with hyperthermia demonstrate a prolonged passage through late S/ G2 phase of cell cycle in comparison to cells treated with gemcitabine alone. This coincides with inhibition of resolution of γH2AX foci. Our findings also demonstrate that thermal sensitization of human hepatocellular carcinoma cell lines to gemcitabine is mediated through an Mre11-dependent homologous recombination repair pathway. Combination of non-invasive radiofrequency field-induced hyperthermia and gemcitabine was superior to either therapy alone (p

Tocotrienol as potential anticancer agent

Vitamin E is composed of two structurally similar compounds: tocopherols (TPs) and tocotrienols (T3). Despite being overshadowed by TP over the past few decades, T3 is now considered to be a promising anticancer agent due to its potent effects against a wide range of cancers. A growing body of evidence suggests that in addition to its antioxidative and pro-apoptotic functions, T3 possesses a number of anticancer properties that make it superior to TP. These include the inhibition of epithelial-to-mesenchymal transitions, the suppression of vascular endothelial growth factor tumor angiogenic pathway and the induction of antitumor immunity. More recently, T3, but not TP, has been shown to have chemosensitization and anti-cancer stem cell effects, further demonstrating the potential of T3 as an effective anticancer therapeutic agent. With most of the previous clinical studies on TP producing disappointing results, research has now focused on testing T3 as the next generation vitamin E for chemoprevention and cancer treatment. This review will summarize recent developments in the understanding of the anticancer effects of T3. We will also discuss current progress in clinical trials involving T3 as an adjuvant to conventional cancer therapy.

Vasoactivity of AG014699, a clinically active small molecule inhibitor of poly(ADP-ribose) polymerase: a contributory factor to chemopotentiation in vivo?

Purpose: Poly(ADP-ribose) polymerase (PARP) plays an important role in DNA repair, and PARP inhibitors can enhance the activity of DNA-damaging agents in vitro and in vivo. AG014699 is a potent PARP inhibitor in phase II clinical development. However, the range of therapeutics with which AG014699 could interact via a DNA-repair based mechanism is limited. We aimed to investigate a novel, vascular-based activity of AG014699, underlying in vivo chemosensitization, which could widen its clinical application.

Experimental Design: Temozolomide response was analyzed in vitro and in vivo. Vessel dynamics were monitored using “mismatch” following the administration of perfusion markers and real-time analysis of fluorescently labeled albumin uptake in to tumors established in dorsal window chambers. Further mechanistic investigations used ex vivo assays of vascular smooth muscle relaxation, gut motility, and myosin light chain kinase (MLCK) inhibition.

Results: AG014699 failed to sensitize SW620 cells to temozolomide in vitro but induced pronounced enhancement in vivo. AG014699 (1 mg/kg) improved tumor perfusion comparably with the control agents nicotinamide (1 g/kg) and AG14361 (forerunner to AG014699; 10 mg/kg). AG014699 and AG14361 relaxed preconstricted vascular smooth muscle more potently than the standard agent, hydralazine, with no impact on gut motility. AG014699 inhibited MLCK at concentrations that relaxed isolated arteries, whereas AG14361 had no effect.

Conclusion: Increased vessel perfusion elicited by AG014699 could increase tumor drug accumulation and therapeutic response. Vasoactive concentrations of AG014699 do not cause detrimental side effects to gut motility and may increase the range of therapeutics with which AG014699 could be combined with for clinical benefit.

Variation of strand break yield for plasmid DNA irradiated with high-Z metal nanoparticles.

PURPOSE: Poly(ADP-ribose) polymerase (PARP) plays an important role in DNA repair, and PARP inhibitors can enhance the activity of DNA-damaging agents in vitro and in vivo. AG014699 is a potent PARP inhibitor in phase II clinical development. However, the range of therapeutics with which AG014699 could interact via a DNA-repair based mechanism is limited. We aimed to investigate a novel, vascular-based activity of AG014699, underlying in vivo chemosensitization, which could widen its clinical application. EXPERIMENTAL DESIGN: Temozolomide response was analyzed in vitro and in vivo. Vessel dynamics were monitored using "mismatch" following the administration of perfusion markers and real-time analysis of fluorescently labeled albumin uptake in to tumors established in dorsal window chambers. Further mechanistic investigations used ex vivo assays of vascular smooth muscle relaxation, gut motility, and myosin light chain kinase (MLCK) inhibition. RESULTS: AG014699 failed to sensitize SW620 cells to temozolomide in vitro but induced pronounced enhancement in vivo. AG014699 (1 mg/kg) improved tumor perfusion comparably with the control agents nicotinamide (1 g/kg) and AG14361 (forerunner to AG014699; 10 mg/kg). AG014699 and AG14361 relaxed preconstricted vascular smooth muscle more potently than the standard agent, hydralazine, with no impact on gut motility. AG014699 inhibited MLCK at concentrations that relaxed isolated arteries, whereas AG14361 had no effect. CONCLUSION: Increased vessel perfusion elicited by AG014699 could increase tumor drug accumulation and therapeutic response. Vasoactive concentrations of AG014699 do not cause detrimental side effects to gut motility and may increase the range of therapeutics with which AG014699 could be combined with for clinical benefi

Inhibition of nuclear factor-kappa B by dehydroxymethylepoxyquinomicin induces schedule-dependent chemosensitivity to anticancer drugs and enhances chemoinduced apoptosis in osteosarcoma cells

Osteosarcoma (OS) is the most common primary malignant bone tumor, usually developing in children and adolescents, and is highly invasive and metastatic, potentially developing chemoresistance. Thus, novel effective treatment regimens are urgently needed. This study was the first to investigate the anticancer effects of dehydroxymethylepoxyquinomicin (DHMEQ), a highly specific nuclear factor-kappa B (NF-kappa B) inhibitor, on the OS cell lines HOS and MG-63. We demonstrate that NF-kappa B blockade by DHMEQ inhibits proliferation, decreases the mitotic index, and triggers apoptosis of OS cells. We examined the effects of combination treatment with DHMEQ and cisplatin, doxorubicin, or methotrexate, drugs commonly used in OS treatment. Using the median effect method of Chou and Talalay, we evaluated the combination indices for simultaneous and sequential treatment schedules. In all cases, combination with a chemotherapeutic drug produced a synergistic effect, even at low single-agent cytotoxic levels. When cells were treated with DHMEQ and cisplatin, a more synergistic effect was obtained using simultaneous treatment. For the doxorubicin and methotrexate combination, a more synergistic effect was achieved with sequential treatment using DHMEQ before chemotherapy. These synergistic effects were accompanied by enhancement of chemoinduced apoptosis. Interestingly, the highest apoptotic effect was reached with sequential exposure in both cell lines, independent of the chemotherapeutic agent used. Likewise, DHMEQ decreased cell invasion and migration, crucial steps for tumor progression. Our data suggest that combining DHMEQ with chemotherapeutic drugs might be useful for planning new therapeutic strategies for OS treatment, mainly in resistant and metastatic cases. Anti-Cancer Drugs 23:638-650 (C) 2012 Wolters Kluwer Health broken vertical bar Lippincott Williams & Wilkins.

Quercetin in Cancer Treatment, Alone or in Combination with Conventional Therapeutics?

Cancer is a problem of global importance, since the incidence is increasing worldwide and therapeutic options are generally limited. Thus, it becomes imperative to find new therapeutic targets as well as new molecules with therapeutic potential for tumors. Flavonoids are polyphenolic compounds that may be potential therapeutic agents. Several studies have shown that these compounds have a higher anticancer potential. Among the flavonoids in the human diet, quercetin is one of the most important. In the last decades, several anticancer properties of quercetin have been described, such as cell signaling, pro-apoptotic, anti-proliferative and anti-oxidant effects, growth suppression. In fact, it is now well known that quercetin has diverse biological effects, inhibiting multiple enzymes involved in cell proliferation, as well as, in signal transduction pathways. On the other hand, there are also studies reporting potential synergistic effects when combined quercetin with chemotherapeutic agents or radiotherapy. In fact, several studies which aim to explore the anticancer potential of these combined treatments have already been published, the majority with promising results. Actually it is well known that quercetin can act on the chemosensitization and radiosensitization but also as chemoprotective and radioprotective, protecting normal cells of the side effects that results from chemotherapy and radiotherapy, which obviously provides notable advantages in their use in anticancer treatment. Thus, all these data indicate that quercetin may have a key role in anticancer treatment. In this context, this review is focused on the relationship between flavonoids and cancer, with special emphasis on the role of quercetin.