Discovery of mixed type thymidine phosphorylase inhibitors endowed with antiangiogenic properties: synthesis, pharmacological evaluation and molecular docking study of 2-thioxo-pyrazolo[1,5-a][1,3,5]triazin-4-ones. Part II.

In our drug discovery program, a series of 2-thioxo-pyrazolo[1,5-a][1,3,5]triazin-4-ones were designed, synthesized and evaluated for their TP inhibitory potential. All the synthesized analogues conferred a varying degree of TP inhibitory activity, comparable or better than positive control, 7-deazaxanthine (7-DX, 2) (IC50 value = 42.63 μM).

Liposome co-encapsulation of synergistic combination of irinotecan and doxorubicin for the treatment of intraperitoneally grown ovarian tumor xenograft.

Liposome co-encapsulation of synergistic anti-cancer drug combination is an emerging area that has demonstrated therapeutic benefit in clinical trials. Remote loading of two or more drugs into a single liposome constitutes a new challenge that calls for a re-examination of drug loading strategies to allow the loading of the drug combination efficiently and with high drug content. In this study, the Mn(2+) gradient coupled with A23187 ionophore was applied in the sequential co-encapsulation of doxorubicin and irinotecan, as this drug loading method is capable of remotely loading drugs by apparently two different mechanisms, namely, coordination complexation and pH gradient.

A structure-activity relationship study of 1,2,4-triazolo[1,5-a][1,3,5]triazin-5,7-dione and its 5-thioxo analogues on anti-thymidine phosphorylase and associated anti-angiogenic activities.

Thirty-three 1,2,4-triazolo[1,5-a][1,3,5]triazin-5,7-dione and its 5-thioxo analogues were designed and synthesized which contained different substituents at meta- and/or para-positions of 2-phenyl or 2-benzyl ring attached to the fused ring structure. The preliminary pharmacological evaluation demonstrated that the 5-thioxo analogues of 1,2,4-triazolo[1,5-a][1,3,5]triazine exhibited a varying degree of inhibitory activity towards thymidine phosphorylase, comparable or better than reference compound, 7-Deazaxanthine (7-DX, 2) (IC50 value = 42.63 μM).

Role of oxidative stress, endoplasmic reticulum stress and ERK activation in triptolide-induced apoptosis.

Since its isolation from Tripterygium wilfordii in 1972, triptolide has been shown to possess potent anticancer activity against a variety of cancers, and has entered phase I clinical trial. It is a diterpenoid triepoxide that acts through multiple molecular targets and signaling pathways. The mitogen-activated protein kinases are well known for their modulation of cell survival and proliferation.

Perorally active nanomicellar formulation of quercetin in the treatment of lung cancer.

Background: Realizing the therapeutic benefits of quercetin is mostly hampered by its low water solubility and poor absorption. In light of the advantages of nanovehicles in the delivery of flavanoids, we aimed to deliver quercetin perorally with nanomicelles made from the diblock copolymer, polyethylene glycol (PEG)-derivatized phosphatidylethanolamine (PE).

Methods: Quercetin-loaded nanomicelles were prepared by using the film casting method, and were evaluated in terms of drug incorporation efficiency, micelle size, interaction with Caco-2 cells, and anticancer activity in the A549 lung cancer cell line and murine xenograft model.

Functionalized carbon nanomaterials: exploring the interactions with Caco-2 cells for potential oral drug delivery.

Although carbon nanomaterials (CNMs) have been increasingly studied for their biomedical applications, there is limited research on these novel materials for oral drug delivery. As such, this study aimed to explore the potential of CNMs in oral drug delivery, and the objectives were to evaluate CNM cytotoxicity and their abilities to modulate paracellular transport and the P-glycoprotein (P-gp) efflux pump. Three types of functionalized CNMs were studied, including polyhydroxy small-gap fullerenes (OH-fullerenes), carboxylic acid functionalized single-walled carbon nanotubes (f SWCNT-COOH) and poly(ethylene glycol) functionalized single-walled carbon nanotubes (f SWCNT-PEG), using the well-established Caco-2 cell monolayer to represent the intestinal epithelium.

Effect of triptolide on focal adhesion kinase and survival in MCF-7 breast cancer cells.

Triptolide, a diterpene from Tripterygium wilfordii, has been shown to have potent anticancer activity, exerting its effects through multiple molecular targets and signaling pathways. Yet, its effect on focal adhesion kinase (FAK), a non-receptor tyrosine kinase overexpressed in breast cancer that regulates cellular adhesion and survival, has not been reported. The current study is the first to report on the effect of triptolide on FAK expression, cell adhesion and survival using MCF-7 breast cancer cells.

Liposomal M-V-05: formulation development and activity testing of a novel dihydrofolate reductase inhibitor for breast cancer therapy.

In the management of metastatic breast cancer, fewer recognized therapeutic standards are available as compared to the early stages of the disease. Thus, it is pertinent to search for new, effective therapy to improve survival, tolerability and quality of life of patients. In this study, a liposomal formulation was developed for a novel dihydrofolate reductase (DHFR) inhibitor, M-V-05.

Lipid-based nanoparticulate systems for the delivery of anti-cancer drug cocktails: Implications on pharmacokinetics and drug toxicities.

The use of drug cocktails has become a widely adopted strategy in clinical cancer therapy. Cytotoxic drug cocktails are often administered based on maximum tolerated dose (MTD) of each agent, with the belief of achieving maximum cell kill through tolerable toxicity level. Yet, MTD administration may not have fully captured the therapeutic synergism that exists among the individual agents in the drug cocktail, as the response to a cocktail regimen, that is, whether the effect is synergistic or not, could be highly sensitive to the concentration ratios of the individual drugs at the site of action.

The C-terminus of PRK2/PKNgamma is required for optimal activation by RhoA in a GTP-dependent manner.

PRK2/PKNgamma is a Rho effector and a member of the protein kinase C superfamily of serine/threonine kinases. Here, we explore the structure-function relationship between various motifs in the C-terminal half of PRK2 and its kinase activity and regulation. We report that two threonine residues at conserved phosphoacceptor position in the activation loop and the turn motif are essential for the catalytic activity of PRK2, but the phosphomimetic Asp-978 at hydrophobic motif is dispensable for kinase catalytic competence.

The last 10 amino acid residues beyond the hydrophobic motif are critical for the catalytic competence and function of protein kinase Calpha.

The segment C-terminal to the hydrophobic motif at the V5 domain of protein kinase C (PKC) is the least conserved both in length and in amino acid identity among all PKC isozymes. By generating serial truncation mutants followed by biochemical and functional analyses, we show here that the very C terminus of PKCalpha is critical in conferring the full catalytic competence to the kinase and for transducing signals in cells. Deletion of one C-terminal amino acid residue caused the loss of approximately 60% of the catalytic activity of the mutant PKCalpha, whereas deletion of 10 C-terminal amino acid residues abrogated the catalytic activity of PKCalpha in immune complex kinase assays.

The very C-terminus of PRK1/PKN is essential for its activation by RhoA and downstream signaling.

PRK1 is a lipid- and Rho GTPase-activated serine/threonine protein kinase implicated in the regulation of receptor trafficking, cytoskeletal dynamics and tumorigenesis. Although Rho binding has been mapped to the HR1 region in the regulatory domain of PRK1, the mechanism involved in the control of PRK1 activation following Rho binding is poorly understood. We now provide the first evidence that the very C-terminus beyond the hydrophobic motif in PRK1 is essential for the activation of this kinase by RhoA.

The very C-terminus of protein kinase Cepsilon is critical for the full catalytic competence but its hydrophobic motif is dispensable for the interaction with 3-phosphoinositide-dependent kinase-1.

In this article, we explore the role of the C-terminus (V5 domain) of PKCepsilon plays in the catalytic competence of the kinase using serial truncations followed by immune-complex kinase assays. Surprisingly, removal of the last seven amino acid residues at the C-terminus of PKCepsilon resulted in a PKCepsilon-Delta731 mutant with greatly reduced intrinsic catalytic activity while truncation of eight amino acid residues at the C-terminus resulted in a catalytically inactive PKCepsilon mutant. Computer modeling and molecular dynamics simulations showed that the last seven and/or eight amino acid residues of PKCepsilon were involved in interactions with residues in the catalytic core.

Identification of an integral plasma membrane pool of protein kinase C in mammalian tissues and cells.

Protein kinase C (PKC) is a family of serine/threonine protein kinases that are pivotal in cellular regulation. Since its discovery in 1977, PKCs have been known as cytosolic and peripheral membrane proteins. However, there are reports that PKC can insert into phospholipids vesicles in vitro.

The last five amino acid residues at the C-terminus of PRK1/PKN is essential for full lipid responsiveness.

PRK1/PKN is a member of the protein kinase C (PKC) superfamily of serine/threonine protein kinases. Despite its important role as a RhoA effector, limited information is available regarding how this kinase is regulated. We show here that the last seven amino acid residues at the C-terminus is dispensable for the catalytic activity of PRK1 but is critical for the in vivo stability of this kinase.

The PKCalpha-D294G mutant found in pituitary and thyroid tumors fails to transduce extracellular signals.

Protein kinase C (PKC) is a key regulator of cell proliferation, differentiation, and apoptosis and is one of the drug targets of anticancer therapy. Recently, a single point mutation (D294G) in PKCalpha has been found in pituitary and thyroid tumors with more invasive phenotype. Although the PKCalpha-D294G mutant is implicated in the progression of endocrine tumors, no apparent biochemical/cell biological abnormalities underlying tumorigenesis with this mutant have been found.

Signaling via a novel integral plasma membrane pool of a serine/threonine protein kinase PRK1 in mammalian cells.

Mammalian serine/threonine protein kinases, except for TGF-beta receptor kinase family, are intracellular proteins. PRK1/PKN is a member of the protein kinase C superfamily of serine/threonine kinases and is one of the first identified effectors for RhoA GTPase. However, the role of PRK1 in mediating signaling downstream of activated RhoA is largely unknown.