Current Cancer Drug Targets - Volume 15, Issue 9, 2015

Malignant brain tumors including primary brain tumors (e.g., glioblastoma multiforme) and metastases, are aggressive and lethal entities for the majority of affected patients. Current standard treatments involving combinations of surgery, radiotherapy and systemic chemotherapy offer only modest improvements in survival. Faced with dismal survival, great efforts are deployed to find interesting treatment alternatives. However, the blood-brain barrier (BBB) and the blood-tumor barrier (BTB) remain great obstacles to significant drug delivery to brain tumors. The need to optimize delivery strategies for better patient outcome in the treatment of malignant brain tumors is well acknowledged. Certain interesting strategies use surgical or physical techniques to enhance the distribution of therapeutic agents to the central nervous system. The following strategies will be discussed in this review: intra-arterial delivery, osmotic BBB disruption, intranasal delivery, convection-enhanced delivery and osmotic pumps, implanted polymers, magnetic microspheres and ultrasound BBB disruption. The purpose of this paper is to review the importance of the BBB and the BTB and to review the current status and future perspectives of these delivery procedures.

Mouse double minute 4 (MDM4) as a member of MDM family, is an oncogene emerging as an imperative negative regulator of p53. Tumor suppressor protein p53 plays a crucial role in cell cycle arrest, apoptosis and homeostasis. It has been reported that frequent inactivation of p53 was observed in numerous human cancers including hematologic malignancies. MDM4, the newly discovered modulator of p53 protein, is frequently amplified in various solid tumors such as cutaneous melanoma, retinoblastoma and hematological malignances such as chronic lymphocytic leukemia, acute myeloid leukemia and mantle cell lymphoma. Multiple evidences implicate that over-expression of MDM4 is associated with tumor progression and poor prognosis which can be reversed by knockdown of MDM4 expression or restoration of p53 function, and support the rationale for the design of future MDM4-specific therapeutics. This article discusses and focuses on using MDM4 as a novel biomarker as well as a therapeutic target for hematologic malignancies.

Aberrant increase in protein kinase B (AKT) phosphorylation (pAKT), due to a gain-of-function mutation of phosphatidylinositol-3-kinase (PI3K) or loss-of-function mutation or deletion of phosphatase and tensin homolog (PTEN), is a common alteration in prostate cancer and associated with poor prognosis. Cytosolic phospholipase A2α (cPLA2α) is a lipid modifying enzyme by catalyzing the hydrolysis of arachidonic acid from membrane phospholipid. The released arachidonic acid and its metabolites contribute to survival and proliferation of prostate cancer cells. In this mini-review, we summarize the relationship between pAKT and cPLA2α in prostate cancer cells. There was a concordant increase in pAKT and cPLA2α levels in prostate tissue of prostate epithelial-specific PTEN-knockout mice compared to PTEN-wild type mice. Restoration of PTEN expression or inhibition of PI3K action decreased cPLA2α expression in PTEN-mutated or deleted prostate cancer cells. An increase in AKT phosphorylation elevated, whereas inhibition of AKT phosphorylation diminished, cPLA2α protein levels. pAKT had no influence on cPLA2α expression at mRNA levels but stabilized cPLA2α at protein levels by protecting it from degradation. Conversely, an induction of cPLA2α expression led to an increase in pAKT levels in PTEN-mutated or deleted prostate cancer cells, while silencing of cPLA2α expression or pharmacological blocking cPLA2α action decreased pAKT levels. The diminishment of pAKT by either genetic silencing or pharmacological blocking of cPLA2α was mitigated by the addition of arachidonic acid. The stimulatory effect of arachidonic acid on pAKT levels was lessened by inhibiting the production of arachidonic acid metabolites. These studies have revealed a link between oncogenic pathway and lipid metabolism and provided potential molecular targets for treating prostate cancer.

Dysregulation of epidermal growth factor receptor (EGFR) signaling due to receptor overexpression or activating mutation is associated with cancer cell proliferation, metastasis, and survival. EGFR has become an important therapeutic target for non–small cell lung cancer (NSCLC), and several EGFR-targeted agents, such as tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAbs), have been developed. The EGFR-TKIs gefitinib, erlotinib, and afatinib have been approved for the treatment of advanced NSCLC, and sensitivity to these drugs has been shown to be associated with the presence of EGFR mutations. Various mAbs to EGFR have also been evaluated in preclinical and clinical studies. In particular, phase III trials have shown a clinically significant survival benefit for addition of the anti-EGFR mAbs cetuximab or necitumumab to a platinum doublet in chemotherapy-naïve patients with advanced NSCLC. We here summarize the results of completed and ongoing clinical trials of EGFR-targeted mAbs for the treatment of NSCLC.

Acute Myeloid Leukemia (AML) is a highly aggressive clonal hematopoietic disorder that has been managed with largely unchanged treatment protocols for the past decades. Although conventional chemotherapy bears the potential to cure some AML patients, the course of the disease is frequently fatal despite treatment highlighting the need for novel therapeutic concepts. Recent progress in genetic technologies significantly furthered our understanding of the molecular events leading to the disease, but these advances have not yet been successfully translated into improved treatment outcomes. Here, we review some of the new promising targets expressed by leukemic blasts, including important signaling pathways involved in AML stem/progenitor cell maintenance and drug resistance. We furthermore discuss novel targeted therapies in pre-clinical and clinical development thereby focusing on new compounds targeting receptor and non-receptor tyrosine kinases, farnesyltransferase proteins, and epigenetic modifiers.

α-Methylacyl-CoA racemase (AMACR) has recently been reported as a vital solid tumor marker and is an attractive target for designing anti-tumor agents. It is a mitochondrial and peroxisomal enzyme which plays a central role in the oxidation of cholesterol metabolites and branched chain fatty acids. The three dimensional structure of human AMACR is still unknown. In the current study, homology model using Modeller and different modelling servers based on 1X74A as template is reported. The three dimensional model generated was validated and evaluated using various available programs like PROCHECK, ERRAT, ProSA energy plots, etc. In order to find potent inhibitors of AMACR, a docking study using compounds reported to be active against this enzyme of other organisms was conducted. Among the studied inhibitors, 2-methylmyristoyl- CoA effectively binds to and inhibits the enzyme by means of hydrogen bond interactions with the key residues of pocket. Moreover, molecular dynamics simulation was carried out to check the stability of AMACR/2-methylmyristoyl-CoA complex. The results illustrated the ligand’s high binding affinity with enzyme and the stability of hydrogen bond interactions in dynamic condition. Hence, 2-methylmyristoyl-CoA has been suggested to be a promising lead compound for the design of new inhibitors against AMACR.

X-linked inhibitor of apoptosis (XIAP) is a member of inhibitor of apoptosis (IAP) family and involved in the suppression of apoptosis in cancer cells. This property makes it a therapeutic target for the cancer therapy. In the present study, we have developed QSAR models using chemical descriptors, fingerprints, principal components, docking energy parameters and similarity-based approach against XIAP. We have achieved correlation (R) of 0.803 with R2 value of 0.645 at 10-fold cross validation using SMOreg algorithm. We have evaluated these models on independent dataset to ascertain its robustness and achieved correlation (R) of 0.793 with R2 value of 0.628. Further, we have used these models for the screening of FDA approved drugs and drug-like molecules from ZINC database and prioritized them on the basis of their predicted pIC50 values. Docking studies of top hits with XIAP-BIR3 domain shows that Iodixanol (DB01249) and ZINC68678304 have higher binding affinities than well-known tetrapeptide inhibitor, AVPI. We have integrated these models in a web server named as “XIAPin”. We hope that this web server will contribute in the designing of nifty antagonists against XIAP.