Maria Monica Gramatges

T cells expressing constitutively active Akt resist multiple tumor-associated inhibitory mechanisms.

Adoptive transfer of antigen-specific cytotoxic T lymphocytes has shown promise for the therapy of cancer. However, tumor-specific T cells are susceptible to diverse inhibitory signals from the tumor microenvironment. The Akt/protein kinase B plays a central role in T-cell proliferation, function, and survival and we hypothesized that expression of constitutively active Akt (caAkt) in T cells could provide resistance to many of these tumor-associated inhibitory mechanisms. caAkt expression in activated human T cells increased proliferation and cytokine production, a likely result of their sustained expression of nuclear factor-κB (NF-κB) and provided resistance to apoptosis by upregulating antiapoptotic molecules. caAkt expressing T cells (caAkt-T-cells) were also relatively resistant to suppression by and conversion into regulatory T cells (Tregs). These characteristics provided a survival advantage to T cells cocultured with tumor cells in vitro; CD3/28-stimulated T cells expressing a chimeric antigen receptor (CAR) specific for disialoganglioside (GD2) that redirected their activity to the immunosuppressive, GD2-expressing neuroblastoma cell line, LAN-1, resisted tumor-induced apoptosis when co-expressing transgenic caAkt. In conclusion, caAkt-transduced T cells showed resistance to several evasion strategies employed by tumors and may therefore enhance the antitumor activity of adoptively transferred T lymphocytes.

Short telomeres: from dyskeratosis congenita to sporadic aplastic anemia and malignancy

Telomeres are DNA-protein structures that form a protective cap on chromosome ends. As such, they prevent the natural ends of linear chromosomes from being subjected to DNA repair activities that would result in telomere fusion, degradation, or recombination. Both the DNA and protein components of the telomere are required for this essential function, because insufficient telomeric DNA length, loss of the terminal telomeric DNA structure, or deficiency of key telomere-associated factors may elicit a DNA damage response and result in cellular senescence or apoptosis. In the setting of failed checkpoint mechanisms, such DNA-protein defects can also lead to genomic instability through telomere fusions or recombination. Thus, as shown in both model systems and in humans, defects in telomere biology are implicated in cellular and organismal aging as well as in tumorigenesis. Bone marrow failure and malignancy are 2 life-threatening disease manifestations in the inherited telomere biology disorder dyskeratosis congenita. We provide an overview of basic telomere structure and maintenance. We outline the telomere biology defects observed in dyskeratosis congenita, focusing on recent discoveries in this field. Last, we review the evidence of how telomere biology may impact sporadic aplastic anemia and the risk for various cancers.

Telomere Content and Risk of Second Malignant Neoplasm in Survivors of Childhood Cancer: A Report from the Childhood Cancer Survivor Study

Purpose: Shorter constitutional telomere length has been associated with increased cancer incidence. Furthermore, telomere shortening is observed in response to intensive chemotherapy and/or ionizing radiation exposure. We aimed to determine whether less telomere content was associated with treatment-related second malignant neoplasms (SMN) in childhood cancer survivors. Experimental Design: Using a nested case–control design, 147 cancer survivors with breast cancer, thyroid cancer, or sarcoma developing after treatment for childhood cancer (cases) were matched (1:1) with childhood cancer survivors without a SMN (controls). Cases and controls were matched by primary cancer diagnosis, years since diagnosis, age at the time of sample collection, years of follow-up from childhood cancer diagnosis, exposure to specific chemotherapy agents, and to specific radiation fields. We performed conditional logistic regression using telomere content as a continuous variable to estimate ORs with corresponding 95% confidence intervals (CI) for development of SMN. ORs were also estimated for specific SMN types, i.e., breast cancer, thyroid cancer, and sarcoma. Results: There was an inverse relationship between telomere content and SMN, with an adjusted OR of 0.3 per unit change in telomere length to single-copy gene ratio (95% CI, 0.09–1.02; P = 0.05). Patients with thyroid cancer SMN were less likely to have more telomere content (OR, 0.04; 95% CI, 0.00–0.55; P = 0.01), but statistically significant associations could not be demonstrated for breast cancer or sarcoma. Conclusions: A relation between less telomere content and treatment-related thyroid cancer was observed, suggesting that shorter telomeres may contribute to certain SMNs in childhood cancer survivors. Clin Cancer Res; 20(4); 904–11. ©2013 AACR.

A homozygous telomerase T motif variant resulting in markedly reduced repeat addition processivity in siblings with Hoyeraal Hreidarsson syndrome

Hoyeraal Hreidarsson syndrome (HHS) is a form of dyskeratosis congenita (DC) characterized by bone marrow failure, intrauterine growth retardation, developmental delay, microcephaly, cerebellar hypoplasia, immunodeficiency, and extremely short telomeres. As with DC, mutations in genes encoding factors required for telomere maintenance, such as telomerase reverse transcriptase (TERT), have been found in patients with HHS. We describe 2 sibling HHS cases caused by a homozygous mutation (p.T567M) within the TERT T motif. This mutation resulted in a marked reduction in the capacity of telomerase to processively synthesize telomeric repeats, indicating a role for the T motif in this unique aspect of telomerase function. We support this finding by demonstrating defective processivity in the previously reported p.K570N T-motif mutation. The consanguineous, heterozygous p.T567M parents exhibited telomere lengths around the first percentile and no evidence of a DC phenotype. Although heterozygous processivity defects have been associated with familial, adult-onset pulmonary fibrosis, these cases demonstrate the severe clinical and functional impact of biallelic processivity mutations. Thus, despite retaining the capacity to add short stretches of telomeric repeats onto the shortest telomeres, sole expression of telomerase processivity mutants can lead to a profound failure of telomere maintenance and early-onset multisystem disease.

Shorter Remission Telomere Length Predicts Delayed Neutrophil Recovery After Acute Myeloid Leukemia Therapy: A Report From the Children’s Oncology Group

Purpose Suboptimal outcomes for children with acute myeloid leukemia (AML) necessitate maximally intensive therapy. Consequently, serious adverse events, such as prolonged periods of profound myelosuppression, contribute to AML treatment-related mortality. Telomeres, the repetitive DNA-protein structures at chromosome ends, influence cellular replicative capacity in that critically short telomeres can induce cell senescence or apoptosis. Our objective was to evaluate the impact of telomere length on duration of post-therapy neutropenia in a pediatric AML cohort. Patients and Methods Patients were diagnosed with de novo AML, enrolled in Childrens Oncology Group study AAML0531, and included those with (n = 53) and without (n = 62) significantly delayed neutrophil recovery after chemotherapy. We used quantitative polymerase chain reaction to measure telomere content (TC), a validated proxy for telomere length, from remission bone marrow samples obtained after the second induction chemotherapy course. Results Less TC was significantly associated with prolonged neutropenia after the fourth ( P < .001) and fifth chemotherapy courses ( P = .002). Cox regression adjusting for age at diagnosis confirmed that TC remained independently predictive of time to recovery of absolute neutrophil count for both the fourth and fifth courses ( P = .002 and .009, respectively). DNA from patients was analyzed for germline mutations in four telomere maintenance genes associated with telomere biology disorders. Sequence analysis revealed no enrichment of rare or novel variants in the delayed recovery group. Conclusion Our results suggest that TC at end of AML induction is associated with hematopoietic reconstitution capacity independently of age and may identify those at highest risk for markedly delayed bone marrow recovery after AML therapy.

Somatic mutations in children with GATA2-associated myelodysplastic syndrome who lack other features of GATA2 deficiency

Approximately 10% of children with primary myelodysplastic syndrome (MDS) have germ line GATA2 mutations, leading to the proposal that all children with primary MDS and certain cytogenetic findings, including monosomy 7, be tested for germ line GATA2 mutations regardless of family history or other clinical features associated with GATA2 deficiency. In adults with familial GATA2-MDS, those with somatic mutations in ASXL1 experience rapid disease progression to acute myeloid leukemia (AML) and poor prognosis after stem cell transplantation; however, the prevalence of somatic mutations in primary pediatric GATA2-MDS is unclear. Here, we studied a cohort of 8 pediatric patients with MDS and lacking additional GATA2-associated clinical features or significant family history and identified heterozygous germ line GATA2 mutations in 5 patients, including 1 with a normal karyotype. For those with GATA2-MDS, we screened for somatic mutations in genes with prognostic relevance in AML/MDS, using a targeted next-generation sequencing panel. Although no somatic mutations in ASXL1 were observed, somatic mutations were found in RUNX1, SETBP1, IKZF1, and CRLF2. One subject with deleterious mutations in RUNX1, SETBP1, and IKZF1 rapidly progressed to AML with disease that was refractory to treatment. Our findings confirm the importance of GATA2 testing in primary pediatric MDS, even in the absence of other clinical features of GATA2 deficiency. Further, similar to what has been observed in adults with GATA2-MDS, somatic mutations with potential prognostic effect occur in children with MDS associated with mutations in GATA2.

Identifying patient- and family-centered outcomes relevant to inpatient versus at-home management of neutropenia in children with acute myeloid leukemia

Efficacy of therapeutic strategies relative to patient‐ and family‐centered outcomes in pediatric oncology must be assessed. We sought to identify outcomes important to children with acute myeloid leukemia and their families related to inpatient versus at‐home management of neutropenia. We conducted qualitative interviews with 32 children ≥8 years old and 54 parents. Analysis revealed the impact of neutropenia management strategy on siblings, parent anxiety, and child sleep quality as being outcomes of concern across respondents. These themes were used to inform the design of a questionnaire that is currently being used in a prospective, multiinstitutional comparative effectiveness trial.

Monozygotic twins with non-Down syndrome associated MLL-rearranged hematologic malignancy and megakaryoblastic differentiation

Jennifer H. Foster, Chris L. Williams, Mohamed Tarek Elghetany, Pengfei Liu, Robert A. Krance, Alison A. Bertuch and Maria Monica Gramatges Department of Pediatrics, Section of Hematology and Oncology, Baylor College of Medicine, Houston, TX, USA; Texas Children’s Hospital, Texas Children’s Cancer and Hematology Centers, Houston, TX, USA; Department of Pathology, Division of Anatomic Pathology, Baylor College of Medicine, Houston, TX, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA

Premature Physiologic Aging as a Paradigm for Understanding Increased Risk of Adverse Health Across the Lifespan of Survivors of Childhood Cancer

The improvement in survival of childhood cancer observed across the past 50 years has resulted in a growing acknowledgment that simply extending the lifespan of survivors is not enough. It is incumbent on both the cancer research and the clinical care communities to also improve the health span of survivors. It is well established that aging adult survivors of childhood cancer are at increased risk of chronic health conditions, relative to the general population. However, as the first generation of survivors age into their 50s and 60s, it has become increasingly evident that this population is also at risk of early onset of physiologic aging. Geriatric measures have uncovered evidence of reduced strength and speed and increased fatigue, all components of frailty, among survivors with a median age of 33 years, which is similar to adults older than 65 years of age in the general population. Furthermore, frailty in survivors independently increased the risk of morbidity and mortality. Although there has been a paucity of research investigating the underlying biologic mechanisms for advanced physiologic age in survivors, results from geriatric populations suggest five biologically plausible mechanisms that may be potentiated by exposure to cancer therapies: increased cellular senescence, reduced telomere length, epigenetic modifications, somatic mutations, and mitochondrial DNA infidelity. There is now a critical need for research to elucidate the biologic mechanisms of premature aging in survivors of childhood cancer. This research could pave the way for new frontiers in the prevention of these life-changing outcomes.

Evidence for Genetic Risk Contributing to Long-Term Adverse Treatment Effects in Childhood Cancer Survivors

Survivors of childhood cancer are at increased risk for therapy-related morbidities and mortality. Although the demographic and clinical factors predicting the risk for long-term effects of cancer therapy are well known, the impact of genetic risk for specific late effects is less clearly defined. Here, we review the extant literature and recent research describing genetic modifiers to risk for the more common late effects of childhood cancer therapy. Results of this research support the need for clinical trials that attempt to further refine risk prediction by incorporating genetic testing into existing algorithms that are primarily based on clinical and demographic factors. Confirmation of genetic predisposition, as defined by reproducibility and prospective validation, would permit therapeutic modification and discussion of individualized survivor care plans even at initial cancer diagnosis.