Current Molecular Medicine - Volume 7, Issue 6, 2007

Peroxisomal proliferator activated receptor γ(PPARγ) belongs to the family of nuclear hormone receptors (NHRs), which directly regulate transcription of target genes. The regulatory role of this receptor on lipid metabolism and insulin sensitization is well established. Recently, the overexpression of this receptor in many human cancers has been identified and understanding its biological significance forms the current theme. PPARγ activation by specific agonists leads to growth inhibition, apoptosis and differentiation of tumor cells. PPARγ possess evident tumor promoting properties but the receptor independent effects of its ligands compound the understanding of its biology in cancers. This review highlights the multifaceted role of PPARγ in cancer progression with specific reference to colon, breast, gastric, lung and urological cancers. Molecular events as well as the mediators involved are analyzed in detail along with PPARγ independent effects of ligands under each cancer type. The crucial cross talk that exists between Wnt and PPARγ signaling is also summarized. An attempt has been made to identify the existing lacunae in understanding the biology of PPARγ in cancers along with suggestions for possible rectification.

Disorders of the central nervous system are a major concern in modern human societies. Studies of these disorders require the use of suitable model systems that accurately reproduce the human situation. In this article we focus on the possibilities of using the human NT-2 teratocarcinoma cell line for studies on neuronal differentiation, cellular function and neurodegeneration. Neurons generated from undifferentiated NT-2 precursor cells show neuronal morphology, express neuronal markers, exhibit action potentials and have the advantage of homogeneous cellular composition of clonally derived cells. They release a number of different neurotransmitters, respond to stimulation with glutamate, gamma-amino-butyric acid, and nitric oxide, and form functional synapses in culture. Depending on the differentiation protocol, NT-2 cells also have the capacity to develop into glial cells. Different neuronal differentiation procedures and biological properties of NT-2 neurons are described in the text. In transplantation experiments, differentiated NT-2 neurons integrated successfully into the nervous systems of both experimental animals and human patients without evidence for tumor formation, underlining their value for both basic research and clinical applications. We discuss some potential applications in the fields of basic research, drug discovery, and therapy of CNS damage with particular emphasis on neuronal transplantation and different cell death mechanisms in neuronal degeneration. Grafting of NT-2 neurons has been shown to effectively reverse functional defects in animal disease models. Moreover, an ongoing phase 2 randomized clinical trial indicates the safety and feasibility of NT- 2 neuron transplantation for the treatment of human patients with cerebral stroke.

Extensive research on molecular genetics in recent decades has provided a wealth of information regarding the underlying mechanisms of primary immunodeficiency diseases. The microarray technology has made its entry into the molecular biology research area and hereby enabled signature expression profiling of whole species genomes. Perhaps no other methodological approach has transformed molecular biology more in recent years than the use of microarrays. Microarray technology has led the way from studies of the individual biological functions of a few related genes, proteins or, at best, pathways towards more global investigations of cellular activity. The development of this technology immediately yielded new and interesting information, and has produced more data than can be currently dealt with. It has also helped to realize that even a ‘horizontally exhaustive’ molecular analysis is insufficient. Applications of this tool in primary immunodeficiency studies have generated new information, which has led to a better understanding of the underlying basic biology of the diseases. Also, the technology has been used as an exploratory tool to disease genes in immunodeficiency diseases of unknown cause as in the case of the CD3δ-chain and the MAPBPIP deficiency. For Xlinked agammaglobulinemia, the technique has provided better understanding of the genes influenced by Btk. There is considerable hope that the microarray technology will lead to a better understanding of disease processes and the molecular phenotypes obtained from microarray experiments may represent a new tool for diagnosis of the disease.

LT, LIGHT, and TNF are core family members of the TNFR superfamily of cytokines. LT and LIGHT, produced primarily by lymphocytes, interact with LTβR expressed by stromal and epithelial cells. Extensive studies over the last decade have revealed a critical role of LT-LTβR interactions for organogenesis and maintenance of the secondary lymphoid organs and in the generation of an efficient humoral immune response to various pathogens. LTβR's function beyond the lymphoid organs shows valuable potential yet remains largely undefined. Recent studies indicate that LTβR signaling is required for liver regeneration, hepatitis, and hepatic lipid metabolism. The balance of beneficial and detrimental effects of LTβR is critical for understanding the mechanisms of autoimmune disease and liver function and may open a new avenue for therapeutic intervention. This review will discuss recent advances in understanding LTβR's role in various human and murine disease models while focusing on its regulation of and implications in various liver related diseases.

Huntington's disease is a genetic, neurodegenerative disorder causing cell dysfunction prior to cell death. Mechanisms that underlie the pathological changes continue to be elucidated, which in turn increases the number of potential therapeutic targets which have the ability to reverse or prevent further cell damage. As well as cell protection strategies, cell replacement techniques have been developed with the aim of replacing dead cells and restoring functional circuits. This review describes therapies used in clinical practice, therapies that have shown promise in experimental models either at the genetic or molecular level, and therapies that are subject to human clinical trials. It is likely that any successful therapy in clinical practice will involve a number of different approaches aimed at different targets in order to achieve both cell protection and cell replacement.

Each year, malaria parasites cause more than 500 million infections and 0.5-3 million deaths worldwide, mostly among children under five living in sub-Saharan Africa. In contrast with several viral and bacterial pathogens, which elicit long-lived immunity after a primary infection, these parasites require several years of continuous exposure to confer partial, usually non-sterilizing immune protection. One of the main obstacles to the acquisition of antimalarial immunity is the high degree of antigenic diversity in potential target antigens, which enables parasites to evade immune responses elicited by past exposure to variant forms of the same antigen. Allelic polymorphism, the existence of genetically stable alternative forms of antigen-coding genes, originates from nucleotide replacement mutations and intragenic recombination. In addition, malaria parasites display antigenic variation, whereby a clonal lineage of parasites expresses successively alternate forms of an antigen without changes in genotype. This review focuses on molecular and evolutionary processes that promote allelic polymorphism and antigenic variation in natural malaria parasite populations and their implications for naturally acquired immunity and vaccine development.

Juvenile neuronal ceroid-lipofuscinosis (JNCL, Batten disease, Spielmeyer-Vogt-Sjogren disease, CLN3) is the most common inherited, autosomal recessive, neurodegenerative disorder in man. Like the other neuronal ceroid-lipofuscinoses, it is characterized by progressive loss of vision, seizures, and loss of cognitive and motor functions, leading to premature demise. JNCL is caused by mutations of CLN3, a gene that encodes a hydrophobic transmembrane protein, which localizes to membrane lipid rafts in lysosomes, endosomes, synaptosomes, and cell membrane. While the primary function of the CLN3 protein (CLN3P) may be debated, its absence affects numerous cellular functions including pH regulation, arginine transport, membrane trafficking, and apoptosis. We have recently suggested that the unifying primary function of CLN3P may be in a novel palmitoyl-protein Δ-9 desaturase (PPD) activity that in our opinion could explain all of the various functional abnormalities seen in the JNCL cells. Another group of researchers has recently shown a correlation between the CLN3P expression and the synthesis of bis(monoacylglycerol)phosphate (BMP) and suggested that CLN3P may play a role in the biosynthesis of BMP. In this review, following an introduction to the neuronal ceroidlipofuscinoses, we provide a brief overview and an update of the most recent research in JNCL, specifically that related to the function of CLN3P.