Kathy H.Y. Shair, PhD
1.8 Hillman Cancer Center
5117 Centre Avenue
Pittsburgh, PA 15213
Epstein-Barr virus (EBV) is an oncogenic γ-herpesvirus that is associated with epithelial and B cell malignancies in humans. The Shair lab studies the molecular mechanisms of cancer induced by this latent virus with the purpose of defining how these mechanisms contribute to the oncogenic and metastatic properties of EBV-associated diseases.
EBV-associated cancers have a characteristic latent gene expression pattern (Table 1) of which the latent membrane proteins (LMP) 1 and 2A have been directly linked to oncogenic and pro-survival properties. EBV can immortalize primary B cells and LMP1 is critically required for this process. Additionally, epithelial cells expressing LMP1 and LMP2A have enhanced growth and migratory properties, rendering them tumorigenic in vivo as tumor xenografts in mice. Our recent studies using transgenic mice have shown that LMP2A can function in collaboration with LMP1 to increase carcinoma progression and can also induce unique gene expression changes in B cells that are only apparent in the presence of both proteins. This provided the first in vivo evidence that LMP1 and LMP2A functionally intersect to result in a unique phenotypic outcome. Using this knowledge, we are dissecting how EBV alters the infected cell and the tumor microenvironment through the combined activities of LMP1 and LMP2A. A major goal of the Shair lab is to translate these studies using in vivo mouse models in order to address which pathways are most relevant to tumorigenesis and metastasis in vivo.
Table 1. Viral latency gene expression patterns in EBV-associated cancers.
|Latency Type||Latency Transcripts||Associated Cancer|
(LMP1) v.low levels when expressed
EBNA 3A, 3B, 3C
Post-transplant lymphoproliferative disease
The tumor microenvironment
Interactions with the tumor microenvironment affect the biological properties of the tumor cells. We have observed that epithelial cells expressing LMP1 can induce the formation of focal adhesions, which serve as signaling complexes regulated through interactions with the extracellular environment. A good example where these dynamic interactions occur is metastasis. Cancer cells detach from the primary tumor, gains access to the blood system by breaking down the junctional barriers of the endothelium, exits the blood stream and finally attaches to distal sites forming secondary tumors. The majority of what we know about EBV is based on studies of the producer cell, but the consequence of its interaction with the recipient tumor microenvironment are not fully understood. These interactions may play a significant role in the metastatic nature of EBV-associated epithelial cell cancers, which remains a challenging property to treat.
One mechanism employed by EBV involves the transfer of proteins and microRNAs through endosome-derived membrane vesicles produced by the infected cell called exosomes. Recent studies have demonstrated that LMP1 can facilitate the functional delivery of itself and other modified cellular proteins as a form of intercellular communication. Using imaging techniques to track producer cells and proteins, the Shair lab is investigating how LMP1 and LMP2A can exploit additional mechanisms in the transfer of secreted factors and cell-associated proteins. The goal is to understand how these mechanisms modify the biological properties of neighboring cells as well as cells that act as barriers to metastasis.
Induction of focal adhesions by LMP1 in epithelial cells
Translating the oncogenic properties of EBV encoded proteins
To fully understand the molecular events that are modulated by the oncogenic EBV proteins, the Shair lab is translating these studies to in vivo mouse models and testing these pathways in the context of viral infection. Previous work has demonstrated that transgenic mice can faithfully recapitulating the oncogenic and signaling effects induced by LMP1 and LMP2A. In addition to using mouse models, some of the in vitro discovered effects on cellular pathways such as the down-regulation of the junctional protein plakoglobin, has also been confirmed in clinical biopsies. The Shair lab is developing more pathologically relevant models of nasopharyngeal carcinoma and generating improved transgenic models of B cell lymphomas that can be monitored and tracked longitudinally for tumor growth and metastasis. In addition to molecular, biological and in vivo assays, techniques involving the use of recombinant viruses will also be employed to study the role of the viral proteins in latently infected cells.
Dr. Shair conducts research through the University of Pittsburgh Cancer Institute (UPCI) Cancer Virology Program at the Hillman Cancer Center located in Shadyside. Learn more>
Josh Korber -Undergraduate Research Assistant
Cynthia Thomas -Undergraduate Research Assistant
Laura Wasil -Post Doctoral Associate