Jessica C. Shand

Minor Antigen Distribution Predicts Site-Specific Graft-versus-Tumor Activity of Adoptively Transferred, Minor Antigen-Specific CD8 T Cells

The clinical success of allogeneic T cell therapy for cancer relies on the selection of antigens that can effectively elicit antitumor responses with minimal toxicity toward nonmalignant tissues. Although minor histocompatibility antigens (MiHA) represent promising targets, broad expression of these antigens has been associated with poor responses and T cell dysfunction that may not be prevented by targeting MiHA with limited expression. In this study, we hypothesized that antitumor activity of MiHA-specific CD8 T cells after allogeneic bone marrow transplantation (BMT) is determined by the distribution of antigen relative to the site of tumor growth. To test this hypothesis, we utilized the clinically relevant male-specific antigen HY and studied the fate of adoptively transferred, HY-CD8(+) T cells (HY-CD8) against a HY-expressing epithelial tumor (MB49) and pre-B cell leukemia (HY-E2APBX ALL) in BMT recipients. Transplants were designed to produce broad HY expression in nonhematopoietic tissues (female → male BMT, [F → M]), restricted HY expression in hematopoietic tissues (male → female BMT, [M → F]) tissues, and no HY tissue expression (female → female BMT, [F → F]). Broad HY expression induced poor responses to MB49 despite sublethal graft-versus-host disease and accumulation of HY-CD8 in secondary lymphoid tissues. Antileukemia responses, however, were preserved. In contrast, restriction of HY expression to hematopoietic tissues restored MB49 responses but resulted in a loss of antileukemia responses. We concluded that target alloantigen expression in the same compartment of tumor growth impairs CD8 responses to both solid and hematologic tumors.

Adolescents and young adults successfully restore lymphocyte homeostasis after intensive T-cell depleting therapy for cancer

Long-term impairment of T-cell regeneration has been widely recognized in humans rendered lymphopenic by disease or therapy (Hakim & Gress, 2005). Successful restoration of T-cell homeostasis following lymphodepletion requires residual thymic function, and age-associated declines in thymic function prevent full immune reconstitution in a substantial percentage of adolescents and adults following the induction of lymphopenia. These observations raise the possibility that only young children are capable of full restoration of T-cell homeostasis following lymphocyte depletion. However, most studies demonstrating incomplete restoration of lymphocyte homeostasis are either limited by relatively short follow-up periods (<2 years) (Hakim et al, 2005) or are confounded by ongoing thymotoxic diseases, such as graft-versus-host disease (Weinberg et al, 2001) or human immunodeficiency virus infection (Douek et al, 2000). In one study, persistent depletion of naı̈ve subsets was observed as long as 30 years following treatment for Hodgkin lymphoma (Watanabe et al, 1997), but an important effect of thymic irradiation in this population could not be ruled out. In order to address whether populations rendered lymphopenic during late childhood, adolescence and young adulthood are capable of full immune reconstitution, we analysed peripheral lymphocyte subsets as part of a crosssectional study examining late effects of treatment for paediatric sarcomas. Thirty-two patients, described previously (Mansky et al, 2006), treated for the Ewing sarcoma family of tumours (ESFT), rhabdomyosarcoma (RMS) and non-rhabdomyosarcoma soft tissue sarcomas (NR-STS) at the Pediatric Oncology Branch of National Cancer Institute (1965–1998), were studied. All patients received multimodality therapy known to induce profound lymphopenia, which included high dose ciclophosphamide (mean 16Æ7 gm/m, range 5Æ8–18Æ4 gm/ m). Peripheral blood CD4, naı̈ve CD4 (CD4CD62L CD45RA), total CD8, naı̈ve CD8 (CD8CD62LCD45RA), B (CD20), and natural killer (NK; CD16CD56CD3) subsets were enumerated using standard techniques and compared with 53 healthy controls studied in the same laboratory. Comparisons were made using two-tailed t-tests, with P £ 0Æ01 considered significant. Median age at treatment was 15Æ4 years (range 7Æ1–34Æ2 years), median age at time of analysis was 37Æ4 years (range 17Æ5–55Æ4 years) and median time elapsed from completion of therapy to analysis was 17Æ3 years (2Æ9– 32Æ6 years). Median age of controls was 38Æ6 years (range 25Æ2– 62Æ8 years). Sarcoma survivors demonstrated normal levels of total circulating CD4 and CD8 T cells, and NK cells and a modest increase in total B cells (Fig 1). Furthermore, they all demonstrated recovery of normal naı̈ve CD4 subsets and there was a statistically significant increase in naı̈ve CD8 cells, indicative of thymic-dependent immune reconstitution. No patient presented clinical evidence for immune deficiency or autoimmunity following completion of therapy. Thus, in the absence of intercurrent disease and high-dose mediastinal irradiation, humans that were rendered lymphopenic during adolescence and early adulthood successfully restored lymphocyte homeostasis when followed for prolonged periods. Whether populations of older individuals also reliably restore lymphocyte homeostasis with prolonged follow-up will require long-term studies.

Differential gene expression in acute lymphoblastic leukemia cells surviving allogeneic transplant

The effectiveness of allogeneic graft-versus-leukemia (GVL) activity in control of acute lymphoblastic leukemia is generally regarded as poor. One possible factor is dynamic adaptation of the leukemia cell to the allogeneic environment. This work tested the hypothesis that the pattern of gene expression in acute lymphoblastic leukemia cells in an allogeneic environment would differ from that in a non-allogeneic environment. Expression microarray studies were performed in murine B lineage acute lymphoblastic leukemia cells recovered from mice that had undergone allogeneic MHC-matched but minor histocompatibility antigen mismatched transplants. A limited number of genes were found to be differentially expressed in ALL cells surviving in the allogeneic environment. Functional analysis demonstrated that genes related to immune processes, antigen presentation, ubiquitination and GTPase function were significantly enriched. Several genes with known immune activities potentially relevant to leukemia survival (Ly6a/Sca-1, TRAIL and H2-T23) were examined in independent validation experiments. Increased expression in vivo in allogeneic hosts was observed, and could be mimicked in vitro with soluble supernatants of mixed lymphocyte reactions or interferon-gamma. The changes in gene expression were reversible when the leukemia cells were removed from the allogeneic environment. These findings suggest that acute lymphoblastic leukemia cells respond to cytokines present after allogeneic transplantation and that these changes may reduce the effectiveness of GVL activity.

“Existential Fridays”—reflection in action

The practice of pediatric oncology provides a unique lens through which to reflect on the profound challenge of caring for suffering children. Pediatric residents and oncology fellows often ask me how they can learn to cope with the suffering they encounter, and maintain that coping mechanism through the long arc of a healthy career. When we consider the rising prevalence of unwellness among physicians, the answer to this question becomes more immediate. Through many informal conversations with pediatric residents over the years, it is clear that many want an opportunity to reflect upon their experiences with patient suffering, but lack the time and role modeling to do so effectively. Inspired by their requests, I devised a pedagogical experiment while attending our inpatient service; once a week (on Fridays), I replaced my daily afternoon didactic with an hour-long, open invitation to discusswhat residents foundmost difficult, or rewarding, about their experienceonourunit. In this essay, Iwill describea central theme that emerged from these discussions, which I came to call “Existential Fridays”—the struggle for residents to incorporate spiritual awareness into their practice—and how I used my experience as both a physician and teacher of theology to answer this call. All of the residents who participated in the sessions described feelings of helplessness and fear when caring for children with cancer— particularly for children who were suffering physically and emotionally. Many expressed that something “just felt different” about caring for a child suffering with cancer compared to children they encountered in other acute care settings. We decoded that “something” to be a more immediate sense of the possibility of death, and of the difficult emotional and moral conundrum represented by dying children. Many residents expressed the profound conflict they felt trying to separate their own personal beliefs about suffering and death from the rational process of clinical decision making. More than half expressed a particular frustration with feeling they were “not allowed” to discuss spiritual matters with patients and families, even if the situation seemed appropriate for them to do so. As a teacher of both medicine and theology, the latter point struck a resonant chord. As we navigate the presentmoment of rapidly evolving oncology therapy, emphasis on patient engagement, and physician resilience, is there an opportunity to revisit the integration of science and spirit? Our attitudes about suffering and death are inextricably linked to our own cultural, social, and spiritual rubric—regardless of whether those perspectives are anchored in a specific faith tradition. Recognizing the need to cultivate a larger sense of self-awareness into professional identity and patient communication skills, many medical schools have developed curricula that encourage students to explore such attitudes—and their impact on patient care—while building their fundamental clinical knowledge. There remains a large gap, however, between exploring ones attitudes about suffering as a student, and integrating that awareness into mature practice as a resident on a demanding hospital service. As amedical educator, I felt that therewas little inmy ownmedical training that preparedme to help young physicians close that gap. As a student and teacher of theology, however, I am fortunate to have a complementary perspective on how healers—whether medical, pastoral, or both—engage human suffering. A critical theme in practical theological education, particularly for those training for careers in ministry or chaplaincy, is the concept of bearing witness. To bear witness means to be present with a person in need, affirming their suffering, without trying to change the outcome. While the minister (or chaplain, or pastoral care professional) may be expected to heal certain things for a suffering person—for example, to help solve a challenging family dynamic, organize community support, or navigate a particular spiritual question—it is fundamental that they first meet the person where they are, bearing witness to their suffering in its unique context. As physicians, our training prepares us to heal with the very best that science andmedicine has to offer. The excellent survival of many pediatric cancers affirms this. Whether or not the patient is cured, we must also pause, meet our patients where they are, and bear witness to their suffering. In so doing, we can also affirm themost important medicine we have to offer—hope—in all of its many shades and expressions. It is here that there is still much good to be done, and much healing that can happen, where treatments fall short of our expectations. At the concluding “Existential Friday” of each resident rotation, I am always asked how I come to terms with the suffering and death of my own patients. Over time, my answer has evolved into a mantra of

Successful reduced-intensity conditioning hematopoietic stem cell transplantation for paroxysmal nocturnal hemoglobinuria with aplastic anemia in two children

Paroxysmal nocturnal hemoglobinuria (PNH) is an extremely rare cause of bone marrow failure in children. We report two children who presented with pancytopenia, and were diagnosed with PNH with severe aplastic anemia. Both children underwent upfront, successful hematopoietic stem cell transplantation with reduced‐intensity conditioning. One patient had a syngeneic donor, and one patient had a 10/10 matched unrelated donor. Neither patient developed graft versus host disease, infections, or recurrent PNH. Reduced‐intensity conditioning hematopoietic stem cell transplantation is a reasonable therapy for PNH with marrow failure in children.

Recurrent scarring papulovesicular lesions on sun-exposed skin in a 22-year-old man

KEY TEACHING POINTS.

Looking up for AML in Down syndrome

In this issue of Blood , Taub et al report improved survival with reduced-intensity therapy and the prognostic significance of end-induction residual disease from the largest prospective trial to date in children with myeloid leukemia of Down syndrome (ML-DS): the Children’s Oncology Group AAML0431 study. 1

One giant leap for pediatric AMKL.

In this issue of Blood , [de Rooij et al][1] report, through the largest-ever molecular assessment in a multinational cohort, the prognostic significance of several recurrent genetic aberrations in children with acute megakaryoblastic leukemia (AMKL).[1][2] ![Figure][3] Survival curves