Outcomes of Measurable Residual Disease in Pediatric Acute Myeloid Leukemia before and after Hematopoietic Stem Cell Transplant: Validation of Difference from Normal Flow Cytometry with Chimerism Studies and Wilms Tumor 1 Gene Expression.

We enrolled 150 patients in a prospective multicenter study of children with acute myeloid leukemia undergoing hematopoietic stem cell transplantation (HSCT) to compare the detection of measurable residual disease (MRD) by a "difference from normal" flow cytometry (ΔN) approach with assessment of Wilms tumor 1 (WT1) gene expression without access to the diagnostic specimen. Prospective analysis of the specimens using this approach showed that 23% of patients screened for HSCT had detectable residual disease by ΔN (.04% to 53%). Of those patients who proceeded to transplant as being in morphologic remission, 10 had detectable disease (.04% to 14%) by ΔN. The disease-free survival of this group was 10% (0 to 35%) compared with 55% (46% to 64%, P < .001) for those without disease. The ΔN assay was validated using the post-HSCT specimen by sorting abnormal or suspicious cells to confirm recipient or donor origin by chimerism studies. All 15 patients who had confirmation of tumor detection relapsed, whereas the 2 patients with suspicious phenotype cells lacking this confirmation did not. The phenotype of the relapse specimen was then used retrospectively to assess the pre-HSCT specimen, allowing identification of additional samples with low levels of MRD involvement that were previously undetected. Quantitative assessment of WT1 gene expression was not predictive of relapse or other outcomes in either pre- or post-transplant specimens. MRD detected by ΔN was highly specific, but did not identify most relapsing patients. The application of the assay was limited by poor quality among one-third of the specimens and lack of a diagnostic phenotype for comparison.

Inefficient dystrophin expression after cord blood transplantation in Duchenne muscular dystrophy.

We report a boy who received two allogeneic stem cell transplantations from umbilical cord donors to treat chronic granulomatous disease (CGD). The CGD was cured after the second transplantation, but 2.5 years later he was diagnosed with Duchenne muscular dystrophy (DMD). Examinations of his DNA, muscle tissue, and myoblast cultures derived from muscle tissue were performed to determine whether any donor dystrophin was being expressed. The boy was found to have a large-scale deletion on the X chromosome that spanned the loci for CYBB and DMD. The absence of dystrophin led to muscle histology characteristic of DMD. Analysis of myofibers demonstrated no definite donor cell engraftment. This case suggests that umbilical cord-derived hematopoietic stem cell transplantation will not be efficacious in the therapy of DMD without additional interventions that induce engraftment of donor cells in skeletal muscle.

Ovarian yolk sac tumor associated with major fibrosarcoma component in a 13-year-old girl.

We are presenting a case of a 13-year-old girl with a chief complaint of lower abdominal pain. A computed tomographic scan showed a 10-cm right ovarian mass. The serologic testing showed high alpha-fetoprotein level. The patient underwent a right adnexectomy and an omentectomy. The final diagnosis was a yolk sac tumor with a major (95%) fibrosarcoma component, based on morphology and further confirmed by an extensive panel of immunohistochemistry. Postoperatively, the alpha-fetoprotein level dropped to normal. The patient completed 7 cycles of multiagent chemotherapy with cisplatin without major complications. At her 7-month follow-up, the patient still remains disease free. To our knowledge, our case is the first of its kind in the literature to document yolk sac tumor associated with fibrosarcoma in a teenage female. Owing to the rarity of this entity, the prognosis of this patient is widely unknown and it is yet still to be seen.

Targeting a mimotope vaccine to activating Fcgamma receptors empowers dendritic cells to prime specific CD8+ T cell responses in tumor-bearing mice.

A major challenge for inducing antitumor immune responses with native or modified tumor/self-Ags in tumor-bearing hosts relates to achieving efficient uptake and processing by dendritic cells (DCs) to activate immune effector cells and limit the generation of regulatory T cell activity. We analyzed the ability of therapeutic DC vaccines expressing a CD166 cross-reactive mimotope of the GD2 ganglioside, 47-LDA, to selectively expand adoptively transferred, tumor-specific T cells in NXS2 neuroblastoma tumor-bearing syngeneic mice. Before the adoptive cell transfer and DC vaccination, the tumor-bearing mice were lymphodepleted by nonmyeloablative total body irradiation or a myeloablative regimen that required bone marrow transplantation. The 47-LDA mimotope was presented to DCs either as a linear polypeptide in conjunction with universal Th epitopes or as a fusion protein with the murine IgG2a Fc fragment (47-LDA-Fcgamma2a) to deliver the antigenic cassette to the activating Fcgamma receptors. We demonstrate that immunization of adoptively transferred T cells in tumor-bearing mice with the 47-LDA mimotope expressed in the context of the activating Fc fusion protein induced higher levels of antitumor immune responses and protection than the 47-LDA polypeptide-DC vaccine. The antitumor efficacy of the therapeutic 47-LDA-Fcgamma2a-DC vaccine was comparable to that achieved by a virotherapy-associated cancer vaccine using a recombinant oncolytic vaccinia virus expressing the 47-LDA-Fcgamma2a fusion protein. The latter treatment, however, did not require total body irradiation or adoptive cell transfer and resulted in induction of antitumor immune responses in the setting of established tolerance, paving the way for testing novel anticancer treatment strategies.