Bidirectional signal transduction is a newly elucidated mechanism in intercellular communication. The bidirectional signal transduction mediated by the Eph-ephrin is an important representative in this field. The Eph family receptor tyrosine kinases and their membrane-bound ligands, the ephrins, play pivotal roles in the development of nervous system, angiogenesis, etc. The signal transduction into cells by Eph receptors is the forward signal, whereas the signal transduction by ephrins is the reverse signal. Based on their molecular structures, the ephrins can be divided into two subclasses, i.e. ephrinA and ephrinB. The ephrinBs are transmembrane proteins, which can activate FAK, JNK and Wnt signal transduction pathways through phosphotyrosine-dependent signaling and PDZ-binding motif-dependent signaling. The ephrinAs are glycosylphosphotidylinositol (GPI) anchored proteins, which can also mediate reverse signal transduction.

Viral etiology of tumor has been studied for a century.Seven human tumor viruses were identified over the past half century.The complexity and regularity of the pathogenic mechanisms of human tumor viruses have been elucidated preliminarily.Human genome sequencing indicated that 8 ％ of human genes were composed of human endogenous retroviruses (HERVs).Owing to the findings that adult T-cell leukemia virus (HTLV) can cause human adult T-cell leukemia and animal exogenous and HERVs can induce tumors and malignant diseases,the relationship between HERVs and human tumors has attracted much attention receutly.Here this article discusses the association of the expression of HERVs with leukemia and solid tumors progression,which may be an important aspect of tumor virology.

As novel organisms,tumors undergo microevolution in limited time and space in vivo.Due to genetic mutations and epigenetic mechanisms,tumor cell clones undergo linear or branching evolution.In most clinic patients,tumors develop through branching evolution pathways,causing tumor heterogeneity and affecting tumor progression.Microevolution is the biological basis for the refractoriness and recurrence of tumors and has been paid attention in research and clinic recently.In this paper,acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) are used as examples to demonstrate tumor microevolution and the concept of linear and branching evolution.Questions and perspective in the field of tumor microevolution research are also discussed.

Human herpesvirus 6 (HHV-6) is recognized as a ubiquitous dsDNA virus in human with widespread cell tropism in vivo, which could induce lifelong latent infection and be reactivated in some immunocompromised individuals leading to serious diseases. With the increasing application of hematopoietic stem cell transplantation (HSCT), it is obvious that HHV-6 reactivation has a close relationship with several complications including encephalitis after transplantation. On the other hand, among about 1 % infected people, HHV-6 and subtelomeric region of cell chromosomes in the state of endogenous persistent infection play a part in activated virus infection. As the detection methods make a great progress in HHV-6 detection, clinical data reveals the relationship between HHV-6 reactivation and lots of chronic diseases, especially lymphoma, leukemia as well as some chronic hematopoietic and immunological diseases.

Cancer stem cells (CSCs) are units in cancer evolution.The elucidation the origin of CSCs has great significance on prevention and treatment of cancers.This paper discusses possible origins,genetic pathways and mechanisms of CSC on the basis of the literature and authors' research.Normal stem cells could be malignantly transformed to CSC through long term accumulation of gene mutations.Induction to pluripotent stem cells by reprogramming is a possible pathway for somatic cells to become CSCs.Dedifferentiation of cancer cells to CSCs is another pathway.Epithelial-mesenchymal transition (EMT),which is an important mechanism for cellular plasticity,plays important roles in cancer metastasis and stemness of cancer cells.Cell-fusion inducing EMT could be a mechanism for the genesis of CSCs.Infection of some virus is also related to the genesis of CSCs.The complexity of cancer biology was also discussed.

Human herpesviruses (HHV) are widespread all over the world,and persist in human in latent infection.When reactivated,HHV plays an important role in the pathogenesis and development of tumor and other diseases.Much attention has been paid on EB virus which can cause different tumors and other diseases.Studies within this half century have elucidated the mechanism of oncogenesis of γ-HHV.Recently it was reported that other HHV may have oncomodulation functions.

Cell death as the partner of cell proliferation is one of the basic mechanism in cell biology. Recently, it became obscure since more and more patterns of cell death were reported. However, the classification of cell death, which was recommended by the Nomenclature Committee on Cell Death (NCCD) in 2009, clarified the criteria. The theme of the recommendation and recent data from the literature were discussed in this review. The significance of studies on cell death was discussed.

After near a century of research,the diverse and complicated relationship between viruses and tumors has been elucidated gradually.Last century it was demonstrated that some retroviruses and some herpes viruses could induce lymphoma and leukemia in some animals.However,it is more complicated in human.During the last two decades it has been confirmed that several types of hepatitis viruses could cause hepatocellular carcinoma and the relationship between human papillomaviruses and cervix carcinoma has been established.These viral vaccines became useful tools to prevent prevalence of these carcinomas.Because of the successful inoculation of live attenuated viral vaccines all around the world in recent 15 years,oncolytic virotherapy is revived,and provides a novel strategy for treatment of refractory tumors.

Allee effect is a phenomenon in ecology characterized by a correlation between population size or density and the mean individual fitness of population or species.It is consistent with density dependent phenomenon in biomedical field.Recently,Allee effect has been studied by theoretical biologist in detail for oncology biological research.Leukemia cells,which reside in organic microenvironment,show an obvious Allee effect.The authors compared Allee effect with density dependent growth of leukemia cells based on their work experience and literature data.No principle distinction was found between these two terms.In this paper,Allee effect in leukemia cell culture and leukemia,especially in minimal residual disease,will be discussed in the view of ecology.The association between Allee effect and leukemogenesis and relapse dynamics will also be explored in the future research.

Aim To explore the antioxidation of pergolide on rat models of Parkinson disease and its mechanism. Methods Wistar rats were pretreated daily with pergolide(1.0 mg?kg -1,ip),pergolide combined with sulpiride(25 mg?kg -1) or sulpiride alone for 7 days, and then sacrificed by decapitation. The activity of SOD and GSH in striatum was determined. Unilateral Parkinsonian models were made in rest of the rats by stereotaxically injecting 6-OHDA. After two weeks, apomorphine (APO)-induced rotational behavior of each group was compared, and the concentrations of striatal dopamine (DA),dihydroxyphenyl acetic acid(DOPAC) and homovanilic acid(HVA) were determined by high performance liquid chromatography (HPLC). Result Administration of pergolide for 7 days significantly increased the act- ivities of SOD and GSH in the striatum (P