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Near haploidy (23-29 chromosomes) is a numerical cytogenetic aberration in childhood acute lymphoblastic leukemia (ALL) associated with particularly poor outcome. In contrast, high hyperdiploidy (51-67 chromosomes) has a favorable prognosis. Correct classification and appropriate risk stratification of near haploidy is frequently hampered by the presence of apparently high hyperdiploid clones that arise by endoreduplication of the original near haploid clone. We evaluated next-generation-sequencing (NGS) to distinguish between "high hyperdiploid" leukemic clones of near haploid and true high hyperdiploid origin. Five high hyperdiploid ALL cases and the "high hyperdiploid" cell line MHH-CALL-2, derived from a near haploid clone, were tested for uniparental isodisomy. NGS showed that all disomic chromosomes of MHH-CALL-2, but none of the patients, were of uniparental origin, thus reliably discriminating these subtypes. Whole-exome- and whole-genome-sequencing of MHH-CALL-2 revealed homozygous non-synonymous coding mutations predicted to be deleterious for the protein function of 63 genes, among them known cancer-associated genes, such as FANCA, NF1, TCF7L2, CARD11, EP400, histone demethylases, and transferases (KDM6B, KDM1A, PRDM11). Only eight of these were also, but heterozygously, mutated in the high hyperdiploid patients. Structural variations in MHH-CALL-2 include a homozygous deletion (MTAP/CDKN2A/CDKN2B/ANRIL), a homozygous inversion (NCKAP5), and an unbalanced translocation (FAM189A1). Together, the sequence variations provide MHH-CALL-2 with capabilities typically acquired during cancer development, e.g., loss of cell cycle control, enhanced proliferation, lack of DNA repair, cell death evasion, and disturbance of epigenetic gene regulation. Poorer prognosis of near haploid ALL most likely results from full penetrance of a large array of detrimental homozygous mutations.

Oral chronic graft vs. host disease (GVHD) frequently presents in patients with sclerotic features of skin GVHD and is often associated with considerable limitations of oral food intake and decreased quality of life. Systemic tacrolimus is efficacious for prophylaxis and treatment of acute and chronic GVHD and topical tacrolimus has shown activity in chronic GVHD skin lesions. We therefore initiated a pilot study to investigate the safety and efficacy of topical tacrolimus ointment in children with oral GVHD. Six patients suffering from oral GVHD (five chronic and one acute) were included in the study. Tacrolimus ointment 0.1% was applied twice daily using sterile gauze. The only side-effects observed were a slight burning discomfort after the first application in one patient and after food intake in another patient. Tacrolimus was absorbed systemically in four of six patients. Of six patients, we observed a complete response in two, a very good partial response (VGPR) in two, and a PR in two patients, respectively. We conclude that topical application of tacrolimus ointment holds promise as a safe and efficacious treatment for oral GVHD in children. The Food and Drug Administration has recently issued a health advisory about a potential cancer risk associated with topical tacrolimus treatment of the skin; therefore, its benefits should be weighed against its potential risks and diligent long-term follow-up should be carried out especially in children.