Better understanding of the mechanisms promoting malignancies associated with EBV will allow us to personalize monitoring of at-risk subjects (e.g., transplant patients) and to design new strategies to prevent/cure EBV-driven malignancies.
Research topic
Studies to assess the host characteristcics which allow EBV expansion and the mechanisms by which EBV promotes viral latent cycle and immortalization of infected cells, two key motifs for EBV-driven malignancies.
Background
Infection of B cells with EBV in vitro causes sustained cell proliferation which may generate immortalized lymphoblastoid cell lines (LCL). This growth-transforming activity is central to the etiology of B-cell malignancies arising in a context of immunodepression, such as post-transplant lymphoproliferative disorders (PTLD) and Non Hodgkin’s Lymphoma. Organ transplantation is often the only treatment for end state organ failure, such as heart, liver and kidney failure, with more than 117,000 transplants performed worldwide in 2013 (31,000 in Europe). EBV is found in more than 90% of PTLD occurring during the first year after transplantation, with a significant increase in EBV-DNA levels in peripheral blood. Besides immunodepression, immune activation by microbial pathogen-associated molecular patterns (PAMPs) and endogenous damage-associated molecular patterns (DAMPs) may play an important role in the expansion of B cells and increase in EBV level. In addition, persistent immune activation/inflammation may promote accelerated immunesenescence, favoring the onset of solid tumors in which the virus may play an indirect role. Notably, EBV-driven malignancies are associated with the selective expression of latent oncogenic viral proteins, including LMP1, and cell telomerase, which is essential for tumor formation/progression.
Research achievements
- Relationship between immune activation and EBV load. Studies have demonstrated a strong relationship between proinflammatory cytokines ( IL-6, IL-10, TNF-α) and level of EBV load in cells and plasma (Petrara et al, J Clin Virol , 2012; Petrara et al, Front Microbiol, 2013; Petrara et al, J Infect Dis 2014; Petrara et al, Cancer Lett, 2015).
- Cross-talk talk between EBV and telomerase. Our studies demonstrate that EBV oncoprotein LMP1 activates at transcriptional levels TERT, the catalytic component of telomerase (Terrin et al, Int J Cancer 2007; J Virol, 2008). In turn, TERT plays an important role in inhibiting the virus lytic cycle, thereby favouring the induction and maintenance of EBV latency in primary B lymphocytes, a prerequisite for EBV-transformation. (Giunco et al, Clin Cancer Res 2013). The mechanism by which TERT inhibits viral lytic cycle occurs through the NOTCH2 pathway: TERT activates NOTCH2, the major NOTCH family member in B cells, which in turn activates BATF, a trancriptional factor which negatively affects the expression of BZLF1, the master regulator of viral lytic cycle. Inhibition of TERT induces the expression of viral lytic cycle (Giunco et al, Cell Death Dis, 2015). As the viral lytic cycle is accompanied by the death of infected cells, inhibition of TERT may be a useful approach for setting up new therapeutic strategies.
Perspectives
- To study the relationship between PAMPs, DAMPs, immune stimulation, EBV reactivation and expansion of EBV infected cells.
- To study the role of circulating TERT mRNA as a diagnostic/prognostic marker of EBV-related malignancies.
- To study the inhibition of TERT as a therapeutic strategy against EBV-driven malignancies.
The definition of the prognostic/predictive value of telomere and telomerase, main drivers of the unlimited replicative capacity of tumor cells, will allow us to design new approaches for minimally invasive monitoring of tumor onset/progression and response to therapy.
Research topic
Unlimited replicative potential is the hallmark of cancer cells. Telomere/telomerase interplay is the major driver of replicative potential. Understanding the value of costitutive telomere length and circulating levels of TERT, the catalytic component of telomerase, as prognostic/predictive factors may allow us to design new approaches for minimally invasive monitoring of tumor onset/progression and response to therapy.
Background
Telomere shortening, which occurs at each cell division, restricts cell proliferation in normal somatic cells. Maintenance of telomere length, required for the unlimited cell proliferation displayed by cancer cells, is provided by telomerase activity, expressed in the vast majority of tumors. Many tumor-based studies have demonstrated that neoplastic cells generally have shorter telomeres than their adjacent non-cancerous mucosa, strongly supporting the concept that telomere erosion is a critical event in carcinogenesis, by promoting genetic instability. Telomerase reverse transcriptase (TERT), the catalytic component of the telomerase complex, is usually absent in normal somatic cells, but is expressed at variable levels in tumors, and specific mutations in its promoter may influence TERT levels. A body of data indicates that telomere length and levels of TERT/telomerase activity may be prognostic markers in cancers. Circulating cell-free TERT RNA may also be a promising marker for minimally invasive monitoring of disease progression and response to therapy.
Research activities
The team has set up molecular methods based on multiplex PCR and Digital PCR to estimate telomere length, levels of TERT mRNA and telomerase activity. The main results of studies performed in collaboration with clinical centers have demonstrated that:
- telomere length and/or TERT levels are independent prognostic factors in chronic lymphocytic leukemia (Terrin et al, Leukemia 2007; Rampazzo et al, Heamatologica, 2012;) and in colon cancer ( Terrin et al, Clin cancer Res 2008; Bertorelle et al, Brit J Cancer, 2013);
- in head and neck tumors, TERT levels are prognostic of disease progression, and telonmere length in mucosa adjacent to tumors is a marker of field cancerization and prognostic of local relapse (Boscolo-Rizzo et al, Oral Oncol 2015);
- constitutive short telomere, while reducing the risk of familial melanoma, is a risk factor for the onset of sporadic melanoma (Menin et al, Br J Dermatol, 2015);
- constitutive short telomere and low thymic output are independent risk factors for tumor onset in elderly patients (Falci et al, Exp Gerontol,2013);
- circulating TERT mRNA may be a marker of therapy response in patients with rectal cancer (Pucciarelli et al, Ann Surg Oncol, 2012);
- high levels of endogenous or ectopic expression of TERT improve resistance to apoptosis in in vitro cultured tumor cells exposed to antineoplastic agents, thus suggesting that TERT, besides maintaining telomere length, may have additional functions in tumor cells (ongoing research).
Perspectives
- evaluation of predictive/prognostic role of constitutive telomere length in response to therapy/disease progression in elderly patients with colorectal cancer;
- evaluation of predictive role of circulating TERT in response to neoadjuvant therapy in patients with rectal cancer;
- evaluation of prognostic role of circulating TERT in patients with solid tumors (colorectal cancer, head and neck cancers);
- studies of extra-telomeric functions of TERT in in vitro models of viral-driven and viral-independent B-cell malignancies.
