Anthea C. Peters

Constitutive activation of the Wnt canonical pathway in mantle cell lymphoma

Aberrations of the Wnt canonical pathway (WCP) are known to contribute to the pathogenesis of various types of cancer. We hypothesize that these defects may exist in mantle cell lymphoma (MCL). Both the upstream and downstream aspects of WCP were examined in MCL cell lines and tumors. Using WCP-specific oligonucleotide arrays, we found that MCL highly and consistently expressed Wnt3 and Wnt10. beta-catenin, a transcriptional factor that is a downstream target of WCP, is localized to the nucleus and transcriptionally active in all 3 MCL cell lines examined. By immunohistochemistry, 33 (52%) of 64 MCL tumors showed nuclear localization of beta-catenin, which significantly correlated with the expression of the phosphorylated/inactive form of GSK3beta (p-GSK3beta; P = .011, Fisher). GSK3beta inactivation is directly linked to WCP stimulation, since addition of recombinant sFRP proteins (a naturally occurring decoy for the Wnt receptors) resulted in a significant decrease in p-GSK3beta. Down-regulation of DvL-2 (an upstream signaling protein in WCP) by siRNA or selective inhibition of beta-catenin using quercetin significantly decreased cell growth in MCL cell lines. To conclude, WCP is constitutively activated in a subset of MCL and it appears to promote tumorigenesis in MCL.

Mammalian DNA mismatch repair protects cells from UVB-induced DNA damage by facilitating apoptosis and p53 activation.

DNA mismatch repair (MMR) is integral to the maintenance of genomic stability and more recently has been demonstrated to affect apoptosis and cell cycle arrest in response to a variety of adducts induced by exogenous agents. Comparing Msh2-null and wildtype mouse embryonic fibroblasts (MEFs), both primary and transformed, we show that Msh2 deficiency results in increased survival post-UVB, and that UVB-induced apoptosis is significantly reduced in Msh2-deficient cells. Furthermore, p53 phosphorylation at serine 15 is delayed or diminished in Msh2-deficient cells, suggesting that Msh2 may act upstream of p53 in a post-UVB apoptosis or growth arrest response pathway. Taken together, these data suggest that MMR heterodimers containing Msh2 may function as a sensor of UVB-induced DNA damage and influence the initiation of UVB-induced apoptosis, thus implicating MMR in protecting against UV-induced tumorigenesis.

DNA Instability and Human Disease

It is now well established that non-Mendelian examples of DNA instability are associated with human disease. Most malignancies are associated with various chromosomal instabilities, such as aneuploidy, gene amplification, and chromosomal deletion. Furthermore, widespread microsatellite instability (MSI) is associated with a variety of tumors, and instability at specific dynamic repeat expansions underlies a family of neurologic disorders. Inactivation of DNA mismatch repair genes results in genomic instabilities affecting microsatellite regions. Mutations in genes involved in DNA polymerization or Okazaki fragment processing are also associated with MSI. Such instabilities convey a ‘mutator’ phenotype which is pathogenic. The mechanisms controlling trinucleotide repeat expansions are less well understood. Why this type of genomic instability is particularly pathogenic to neurons is also not clear. An understanding of what normally maintains stability is the first step towards preventing such loss of control and maintaining health.

Lymphoproliferative disorders in inflammatory bowel disease patients on immunosuppression: Lessons from other inflammatory disorders.

Immunosuppressive agents, such as thiopurines, methotrexate, and biologics, have revolutionized the treatment of inflammatory bowel disease (IBD). However, a number of case reports, case control studies and retrospective studies over the last decade have identified a concerning link between immunosuppression and lymphoproliferative disorders (LPDs), the oncological phenomenon whereby lymphocytes divide uncontrollably. These LPDs have been associated with Epstein-Barr virus (EBV) infection in which the virus provides the impetus for malignant transformation while immunosuppression hampers the immune systems ability to detect and clear these malignant cells. As such, the use of immunosuppressive agents may come at the cost of increased risk of developing LPD. While little is known about the LPD risk in IBD, more is known about immunosuppression in the post-transplantation setting and the development of EBV associated post-transplantation lymphoproliferative disorders (PTLD). In review of the PTLD literature, evidence is available to demonstrate that certain immune suppressants such as cyclosporine and T-lymphocyte modulators in particular are associated with an increased risk of PTLD development. As well, high doses of immunosuppressive agents and multiple immunosuppressive agent use are also linked to increased PTLD development. Here, we discuss these findings in context of IBD and what future studies can be taken to understand and reduce the risk of EBV-associated LPD development from immunosuppression use in IBD.

Epstein–Barr Virus Infection and Lymphoproliferative Disorders After Transplantation

Epstein–Barr virus (EBV) infection is highly prevalent in both transplant recipients and donors and plays an important role in the pathogenesis of most cases of posttransplant lymphoproliferative disorder (PTLD) seen early after transplant. Over the past decade an epidemiologic shift in PTLD incidence has occurred: PTLD occurring early posttransplant predominantly in high-risk recipients has decreased. This improvement has been attributed to preemptive prevention strategies in these patients and evolving immunosuppression regimens. Efforts have also been made to standardize assays measuring EBV viral load with the goal of improving inter-assay comparisons and standardizing practices. However, EBV-negative PTLD occurring late posttransplant is now emerging as the predominant PTLD subtype, particularly in solid organ transplant recipients. Further research efforts focused on the epidemiology, pathogenesis, and treatment of late PTLDs are required. A prospective, multicenter, controlled trial evaluating sequential therapy with the anti-CD20 monoclonal antibody rituximab followed by chemotherapy has demonstrated prolonged remissions with improved tolerability. But, given the lack of other comparable studies, the standard of care for treatment of PTLD cannot be established. Future therapeutic trials are needed to identify patients that can be spared from chemotherapy, and novel therapeutic approaches must be explored to prevent disease, improve outcomes, and expand the therapeutic armamentarium.

Epstein-Barr virus associated smooth muscle tumors in solid organ transplant recipients: Incidence over 31 years at a single institution and review of the literature

Epstein‐Barr virus (EBV) associated smooth muscle tumors (EBV‐SMT) are a rare complication of solid organ transplantation (SOT). Incidence data related to this EBV‐SMT are limited. EBV DNA is universally present in these tumors. How these cells get infected with EBV, whether this is a result of primary EBV infection vs reactivation, and how persistent active EBV infection post‐transplant influences EBV‐SMT pathogenesis remains unknown.

Autologous transplantation improves survival rates for follicular lymphoma patients who relapse within two years of chemoimmunotherapy: a multi-center retrospective analysis of consecutively treated patients in the real world

Abstract Although chemoimmunotherapy improves outcomes for patients with follicular lymphoma (FL), approximately 20% of patients experience early disease progression within two years of treatment and subsequently poor median survival. We conducted a retrospective study to evaluate survival rates of patients with early relapse who were treated with or without autologous transplantation. Of 517 patients with FL and who received chemoimmunotherapy, 152 relapsed and survived a minimum of four months after progression, including 84 (55.3%) with early relapse ≤2 years following initial therapy and 68 (44.7%) with later relapse. Five-year survival was superior for patients who received autologous transplantation compared to non-transplanted patients within the early relapse group (85.4% vs 57.9%, p = .001), but not within the late relapse group (p = .64). Given the limitations of a retrospective study, our study may suggest that the use of autologous transplantation for FL patients who relapse within two years of initial chemoimmunotherapy is associated with improved survival.

The adverse consequences of initial watchful waiting for patients with follicular lymphoma

Background: Patients with low tumor burden follicular lymphoma (FL) are commonly managed with watchful waiting (WW). The incidence of organ dysfunction and/or transformation at disease progression, and subsequent impact on outcomes is poorly understood. Patients and Methods: Patients managed with WW during 1994 to 2011 were identified through the Alberta Lymphoma Database. Individuals receiving immediate rituximab (R)‐chemotherapy were identified as a comparator group to those on WW who received R‐chemotherapy at progression. Endpoints included transformation, organ dysfunction, time to progression, time to next treatment, progression‐free survival (PFS) after chemotherapy, and overall survival (OS). Results: We identified 238 patients managed with WW (28.9% of registry patients) during this 17‐year period. The median follow up was 8.2 years. At a median of 29.9 months, 58 (24.4%) of these patients developed organ dysfunction and/or transformation. Of 169 (71%) patients who required therapy, 10‐year OS was inferior for those with transformation (hazard ratio, 2.88; P = .002) and organ dysfunction (hazard ratio, 2.10; P = .028). PFS after R‐chemotherapy and OS in patients without organ dysfunction and/or transformation was not affected by the initial WW period, compared with immediate R‐chemotherapy. WW resulted in increased high risk FL International Prognostic Index scores at initiation of R‐chemotherapy (45% vs. 20%), and more frequent transformation at progression (5‐year risk, 17.8% vs. 3.5%; P < .001). Baseline characteristics did not predict organ dysfunction. Conclusion: Patients with FL accepting initial WW should be aware of the 1 in 4 risk of organ dysfunction and/or transformation, and subsequent inferior OS. Physicians should consider surveillance for progression to consider early therapy.

Constitutive Activation of STAT3 in Myeloma Cells Cultured in a Three-Dimensional, Reconstructed Bone Marrow Model

Malignant cells cultured in three-dimensional (3D) models have been found to be phenotypically and biochemically different from their counterparts cultured conventionally. Since most of these studies employed solid tumor types, how 3D culture affects multiple myeloma (MM) cells is not well understood. Here, we compared MM cells (U266 and RPMI8226) in a 3D culture model with those in conventional culture. While the conventionally cultured cells were present in single cells or small clusters, MM-3D cells grew in large spheroids. We discovered that STAT3 was the pathway that was more activated in 3D in both cell lines. The active form of STAT3 (phospho-STAT3 or pSTAT3), which was absent in MM cells cultured conventionally, became detectable after 1–2 days in 3D culture. This elevated pSTAT3 level was dependent on the 3D environment, since it disappeared after transferring to conventional culture. STAT3 inhibition using a pharmacological agent, Stattic, significantly decreased the cell viability of MM cells and sensitized them to bortezomib in 3D culture. Using an oligonucleotide array, we found that 3D culture significantly increased the expression of several known STAT3 downstream genes implicated in oncogenesis. Since most primary MM tumors are naturally STAT3-active, studies of MM in 3D culture can generate results that are more representative of the disease.

The fludarabine, cytarabine, and granulocyte colony-stimulating factor (FLAG) chemotherapy regimen is an alternative to anthracycline-based therapy for the treatment of acute myeloid leukemia for patients with pre-existing cardiac disease

We conducted a retrospective study assessing FLAG (fludarabine, cytarabine, and granulocyte colony‐stimulating factor) as first‐line treatment in 56 newly diagnosed acute myeloid leukemia patients considered ineligible for anthracycline‐based treatment due to advanced age, significant comorbidities, or pre‐existing cardiac disease. The median age was 69 (21–80); 46% received FLAG for pre‐existing cardiac disease and others due to age (32%), non‐cardiac comorbidities (20%), or previous anthracycline exposure (2%). The induction mortality was 16% and, among evaluable patients, 48% achieved a complete remission after the first induction course with an additional patient achieving a remission after a second course for a total complete remission rate of 50%. Four patients proceeded to an allogeneic stem cell transplant including two with pre‐existing cardiac disease. Among non‐transplanted patients, the relapse rate (RR) was 47%. When censored at time of stem cell transplant, the median relapse‐free survival was 14.7 months. The median overall survival was 9.3 months with 1‐ and 2‐yr survivals of 44% and 22%, respectively. There was no difference in clinical outcomes between patients treated with FLAG for cardiac reasons vs. other reasons. In conclusion, FLAG is a useful alternative to anthracycline‐based induction for Acute myeloid leukemia in those with significant comorbidities including pre‐existing cardiac disease.