Ingemar Ernberg Group
Project Leaders in the Ingemar Ernberg Group
In Ingemar Ernbergs and LiFu Hu's groups we focus on experimental systems and clinical collaborations to understand better the connection between infections and cancer in man. Anneka Ehrnst's group study HIV, in particular mother-child transmission.
Epstein-Barr virus (EBV) infection in man is the model" that we are using to elucidate the complex sequence of events leading to tumor development. This is the most common virus in man and at the same time associated with a dozen tumors in man. With this natural infection we study viral and cellular genes involved in tumorigenicity and cell-cell interactions. LiFu Hu's group focuses on the EBV-associated Nasopharyngeal Carcinoma (NPC).
A subgroup works with bioinformatics and computational tools in cancer and infections, designated the Biocomplexity group, collaborating with the Royal School of Technology (KTH).
We are also developing tools to allow comparisons of the normal flora of the gut.
Natural infections are involved in the pathogenesis of 15-20% of all cancer in humans. In particular persistent viral infections and some bacterial infections are linked to cancer risks: hepatitis B virus, human hepatit C virus, human T-cell lymphoma virus, papilloma virus, Epstein-Barr virus (EBV), HHV-8 and H.pylori. Understanding the biology of the interaction between the host and the invading microorganism is crucial for future design of epidemiologic surveys, for identification of risk-groups, prevention, diagnosis and treatment. On the other hand natural infections as a cause of cancer opens unique possibilities to reduce the human cancer burden, by using several of these measures. Characteristic of all the cancer-associated infections known until now is that they may cause chronic or latent persistence of the virus, or bacteria in or at cells of the target tissues. This is either the result of natural strategy or of biological accidents. The subsequent cancer risk depends on direct effects of microbial genes on cellular control systems, and/or on tissue damage and inflammatory type of responses.
All tumor-associated viruses have evolved strategies for survival and spread as part of their physiologic infection, which affects cell cycle and apoptosis control. By inducing transient proliferation in their target organ/cells they prepare for lytic replication by engaging more cells, as an amplification mechanism. Virus infections per se induce apoptosis, which may be regarded as a defense mechanism by the host/host cell. Progression from cells at risk to overt tumor only takes place if late replicative events are truncated or blocked (e.g. by integration, accidental infection of wrong cell type), if the infection cannot be handled by the immune system and/or if the infection raises an inappropriate host reaction.
Epstein-Barr virus (EBV) infection in man, illustrates these points, due to extensive though incomplete knowledge on several of these issues. EBV is the most common virus in the human population (>90% of adults carry the virus). It normally gives rise to an inconspicuous or benign infection, paradoxically, however, under rare circumstances it induces tumors and in vitro it is very efficient in transforming its natural host cell, the B-lymphocyte.
We are studying the following aspects:
- The switch between viral programs controlling B-cell activation and proliferation or resting cell states (latency programs)
- Immune escape and latency in patients at risk detected as virus load and infected cells in different latency programs
- The Biocomplexity group is developing tools and using them to analyze and model from high through put data, such as transcriptomes, microRNAs arrays, statistical mechanics. One project addresses the issue of cells as 'dynamic attractors'
Latent EBV Infection
Latent EBV infection controlling B-cell switches
EBV cooperates with the host B-cell in controlling its fate, either proliferation or G0-rest. This switch is likely to be a cornerstone in that the virus is a risk factor for human B-cell lymphomas.
The minimal requirement for this switch are two viral promoters, the virus household protein EBNA 1 and cellulat transcription factors. We have identified cellular transcription factors of the oct-family and its co-regulators that cooperate with the virus in executing this switch with dramatic downstream consequences for the host cell. A mechanical statistical model for the switch was elaborated with professor Erik Aurell and graduate student Mia Werner, KTH and the model is presently being validated using shRNA knock down and transfection upregulation of the key regulatory proteins.
Viral Latency in Risk Patients
Viral latency in patients at risk detected as virus load and infected cells in different latency programs
The impact of variation of virus infected cells in blood and solid lymphoid organs is studied. We compare healthy EBV-carriers with groups with high risk of lymphoma, HIV-carriers and bone marrow transplant patients. Also, the form of latent infection in vivo is studied in order to find out if this affects lymphoma risk.
The purpose is to understand the basis for increased risk of lymphomatous malignancies in HIV-carriers. Four studies have been completed and are under publication: 1) EBV genome load in blood B-lymphocyte populations increase after HIV-infection, but decrease upon development of AIDS. The individual span of virus load is conspicuously wide ranging. 2) Immunostimulatory treatment such as vaccine adjuvant (alun) contributes to considerable increase of EB virus load in HIV-carriers, further enhanced by history of symtoms upon primary HIV-infection. 3) Primary HIV-infection without adjuvant treatment as above results in no significant increase compared to a group of long term survivors (> 10 years). HIV-RNA levels and EBV-DNA levels in B-cells correlate before treatment with HAART, while the decrease of HIV-RNA after HAART treatment does not correlate to a decrease of EBV genomes after short term observation. 4) Long term follow up of EBV-DNA load for more than three years of HIV-carriers reveals a correlation between high genome levels and various complications.
This project is performed by post doc Jie-Zhi Zou and graduate students Qin Li and Anna Friis in collaboration with clinicians at Huddinge Hospital (Åsa Jernberg-Gustavsson, Jacek Winiarski, Börje Åkerlund and Katarina Gyllensten).
Signal transduction, migration and invasion
Subversion of signal transduction: control of latency
NPC is one of the most common malignancies in certain geographical regions as in Greenland (31 cases /105 inhabitants / year) and Southern China ( 42 cases /105 inhabitants /year) with the highest incidence in the world , although it is rare in other countries (0.6 cases /105 /year in Sweden). Such a pronounced, uneven distribution and the high rate of familial clustering of this cancer strongly suggest that environmental risk factors, including the EBV infection, cooperate with the genetically susceptible background in the high risk populations
In this project we study the impact of EB-viral genes that are expressed in NPC, particularly latent membrane protein 1 (LMP 1) and latent membrane protein 2 (LMP 2). Their effects on signal transduction and cell cycle are studied in in vitro model epithelial systems.
The LMP2A messages are constantly detected in NPC tumor biopsies and, along with EBNA1, is the only protein-coding EBV-specific message detected in individuals harboring EBV latent infection, suggesting that LMP2A plays an important role in vivo for control of latency and EBV-related diseases in humans.
It is quite established a role of LMP2A as a modulator of cell signaling. LMP2A does it by snapping away tyrosine kinases Syk and Lyn from B-cell receptor (BCR) in B cells, and Zap70 and Lck from TCR in T cells. We have shown, in close collaboration with Tony Pawsons group in Toronto, that LMP2A binds and initiates proteasomal degradation of these kinases, which lead to impaired BCR and TCR signaling. The more LMP2A is expressed, such as during the initial step of EBV infection of naïve B cells, the more it interferes with BCR signaling while at the lower expression level, such as in the resting, memory type B cells, LMP2A may even mimic the cellular receptor function by sending tonic, survival signals. LMP2A does it by activating the major pro-survival kinase, Akt. The differential effects of LMP2A are tuned to the viral strategy of latency and sporadic reactivation, as for other herpesviruses.
It is much less known about LMP2A-mediated interference with cell signaling in epithelial cells apart that LMP2A interacts with Syk in epithelial cells as well. We have found a novel interacting partner for LMP2A in epithelial cells, a scaffolding protein Shb. Moreover, we have demonstrated that the LMP2A-Shb complex is functional in epithelial cells, it corroborates Syk-mediated activation of Akt pathway. We focus on impact the LMP2A-rewired signaling may have on function of epithelial cell surface receptors, integrins. We work on another aspect of LMP2A expression in epithelial cells, its impact on endo- and exo-somal traffic of cell surface receptors, such as EGFR, CXCR4, GPCR and pattern recognition receptors of TLR family (TLR 3/7/9).
This work is done by Ingemar Ernberg, Liudmilla Matskova, research associate and graduate student Xiaoying Zhou in collaboration with Tony Pawsons group in Toronto. The LMP1 work was performed by XiangNing Zhang, former graduate student of the group in collaboration with LiFu Hu's group.
The role of EBV latency in Hodgkins lymphoma
In collaboration with the Hematology Unit at the Dept of Medicine, Karolinska University Hospital, we are studying the impact of EBV in subtypes of Hogkins lymphoma. The trascriptomes of the Nodular Sclerosis (NS) and Mixed Cellularity (MC) are correlated to presence of EBV in the tumors. Experimental validation of genes of interest are performed in in vitro cell lines, including a 3-dimensional cell culture system.
This project is perfomed in collaboration with Magnus Björkholm, Anja Porwit-MacDonald and Jan Sjöberg at the Dept of Medicine. Former graduate student Anna Birgersdotter presented a thesis on this.
The Normal Flora of the Gut
We develop techniques to compare the normal flora of the gut between healthy persons and those suffering from bowel problems (with E Zabarovsky, T Midvedt and R Möllby, MTC, and O Ljungqvist, Ersta hospital).
The main concept is to select representative short sequences from the gut microbiome in an unbiased manner. These are analyzed by sequencing and with arrays. Differences in microbiome composition are identified by cross-clonal hybridization between patient samples and controls. This is most likely the only way to make such comparisons until many full microbiomes have been fully sequenced.
Ernberg, I. Et al.
Vad är liv? I människan, i kosmos, i cellen
y Press, Stockholm, 2010.
|Ingemar Ernberg||Professor, senior|
|Iurii Petrov||Doktorand, Forskarstuderande|
|Jie-Zhi Zou||Senior lab manager|