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Eliassen E, Lum E, Pritchett J, Ongradi J, Krueger G, Crawford JR, Phan TL, Ablashi D, Hudnall SD. Human Herpesvirus 6 and Malignancy: A Review. Front Oncol 2018; 8:512. [PMID: 30542640 PMCID: PMC6277865 DOI: 10.3389/fonc.2018.00512] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 10/19/2018] [Indexed: 12/21/2022] Open
Abstract
In order to determine the role of human herpesvirus 6 (HHV-6) in human disease, several confounding factors, including methods of detection, types of controls, and the ubiquitous nature of the virus, must be considered. This is particularly problematic in the case of cancer, in which rates of detection vary greatly among studies. To determine what part, if any, HHV-6 plays in oncogenesis, a review of the literature was performed. There is evidence that HHV-6 is present in certain types of cancer; however, detection of the virus within tumor cells is insufficient for assigning a direct role of HHV-6 in tumorigenesis. Findings supportive of a causal role for a virus in cancer include presence of the virus in a large proportion of cases, presence of the virus in most tumor cells, and virus-induced in-vitro cell transformation. HHV-6, if not directly oncogenic, may act as a contributory factor that indirectly enhances tumor cell growth, in some cases by cooperation with other viruses. Another possibility is that HHV-6 may merely be an opportunistic virus that thrives in the immunodeficient tumor microenvironment. Although many studies have been carried out, it is still premature to definitively implicate HHV-6 in several human cancers. In some instances, evidence suggests that HHV-6 may cooperate with other viruses, including EBV, HPV, and HHV-8, in the development of cancer, and HHV-6 may have a role in such conditions as nodular sclerosis Hodgkin lymphoma, gastrointestinal cancer, glial tumors, and oral cancers. However, further studies will be required to determine the exact contributions of HHV-6 to tumorigenesis.
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Affiliation(s)
- Eva Eliassen
- HHV-6 Foundation, Santa Barbara, CA, United States
| | - Emily Lum
- HHV-6 Foundation, Santa Barbara, CA, United States
| | - Joshua Pritchett
- Department of Internal Medicine, Mayo Clinic, Rochester, MN, United States
| | - Joseph Ongradi
- Institute of Medical Microbiology, Semmelweis University, Budapest, Hungary
| | - Gerhard Krueger
- Department of Pathology and Laboratory Medicine, University of Texas- Houston Medical School, Houston, TX, United States
| | - John R Crawford
- Department of Neurosciences and Pediatrics, University of California San Diego and Rady Children's Hospital, San Diego, CA, United States
| | - Tuan L Phan
- HHV-6 Foundation, Santa Barbara, CA, United States.,Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA, United States
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The product of Kaposi's sarcoma-associated herpesvirus immediate early gene K4.2 regulates immunoglobulin secretion and calcium homeostasis by interacting with and inhibiting pERP1. J Virol 2013; 87:12069-79. [PMID: 23986581 DOI: 10.1128/jvi.01900-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chaperones are proteins that assist the noncovalent folding and assembly of macromolecular polypeptide chains, ultimately preventing the formation of nonfunctional or potentially toxic protein aggregates. Plasma cell-induced-endoplasmic reticulum (ER)-resident protein 1 (pERP1) is a cellular chaperone that is preferentially expressed in marginal-zone B cells and is highly upregulated during plasma cell differentiation. While initially identified as a dedicated factor for the assembly of secreted IgM, pERP1 has since been implicated in suppressing calcium mobilization, and its expression is misregulated in multiple tumors. A number of herpesvirus immediate early gene products play important roles in the regulation of viral gene expression and/or evasion of host immune responses. Here, we report that the Kaposi's sarcoma-associated herpesvirus (KSHV) immediate early viral gene K4.2 encodes an endoplasmic reticulum-localized protein that interacts with and inhibits pERP1. Consequently, K4.2 expression interfered with immunoglobulin secretion by delaying the kinetics of immunoglobulin assembly and also led to increased responsiveness of B-cell receptor signal transduction by enhancing phosphotyrosine signals and intracellular calcium fluxes. Furthermore, K4.2 expression also appeared to contribute to maximal lytic replication by enhancing viral glycoprotein expression levels and ultimately promoting infectious-virus production. Finally, immunohistochemistry analysis showed that pERP1 expression was readily detected in KSHV-positive cells from multicentric Castleman's disease (MCD) and Kaposi's sarcoma (KS) lesions, suggesting that pERP1 may have potential roles in the KSHV life cycle and malignancy. In conclusion, our data suggest that K4.2 participates in lytic replication by enhancing calcium flux and viral glycoprotein expression, but also by interfering with immunoglobulin assembly to potentially dampen the adaptive immune response.
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