T-Cell Receptor and Immunoglobulin Gene Rearrangements in Acute Myeloid and Undifferentiated Leukemias of Adults: Correlation with Weak Surface Expression of CD45 and CDw52 Antigens

Toward a Unified Theory of Why Young People Develop Cancer

Epidemiologic and genetic studies have now defined specific patterns of incidence and distinct molecular features of cancers in young versus aging people. Here, I review a general framework for the causes of cancer in children and young adults by relating somatic genetic mosaicism and developmental tissue mutagenesis. This framework suggests how aging-associated cancers such as carcinomas, glioblastomas, and myelodysplastic leukemias are causally distinct from cancers that predominantly affect children and young adults, including lymphoblastic and myeloid leukemias, sarcomas, neuroblastomas, medulloblastomas, and other developmental cancers. I discuss the oncogenic activities of known developmental mutators RAG1/2, AID, and PGBD5, and describe strategies needed to define missing developmental causes of young-onset cancers. Thus, a precise understanding of the mechanisms of tissue-specific somatic mosaicism, developmental mutators, and their control by human genetic variation and environmental exposures is needed for improved strategies for cancer screening, prevention, and treatment.

Clonotypic VDJ Rearrangements in Mixed Phenotype Acute Leukemia can be Successfully Utilized to Track Minimal Residual Disease

INTRODUCTION

Multiplex polymerase chain reaction (PCR) and next-generation sequencing (NGS) can both be used to identify a neoplastic clonotype by targeting CDR3 and assessing rearrangements in IgH, IgK, IgL, TCR-β, and TCR-gamma loci. The clonotypic sequence can be robustly used to track minimal residual disease (MRD). The ability to track MRD by NGS in mixed phenotype acute leukemia (MPAL) is unknown and warrants investigation.

METHODS

Institutional Review Board (IRB) approval was obtained. Central Moffitt Cancer Center (MCC) database was searched to locate any patients with MPAL from over 600,000 entries. Patient charts were manually curated to identify those with clonoSEQ data, and clinical data was procured from the electronic medical record (EMR).

RESULTS

Twenty-nine patients with MPAL were identified. Only 2 patients with clonoSEQ testing were found. Both demonstrated a B/myeloid phenotype, and both were bilineal. NGS (clonoSEQ) identified 4 dominant (IGH) (patient A; 8/2019) and 2 dominant sequences (patient B; 10/2019), respectively. In both patients, clonoSEQ testing successfully tracked minimal residual disease and mirrored clinical disease burden.

CONCLUSIONS

This report is the first to confirm the utility of NGS-based MRD tracking in patients with MPAL and shows increased sensitivity of NGS over MRD flow cytometry.

Acute myelomonocytic leukemia with t(10;11)(p13;q23): heterogeneity of breakpoints at 11q23 and association with recombinase activation

The human trithorax homolog gene (MLL) is directly involved in over 90% of cases of acute leukemia with abnormalities of 11q23. However, involvement of other genes at 11q23 both centromeric and telomeric of MLL has been identified in different subtypes of leukemia and lymphoma. We describe a case of acute myelomonocytic leukemia (AMML; FAB type M4) with t(10;11)(p13;q23) in which the breakpoint at 11q23 was centromeric to the MLL gene and distinct from the breakpoint seen in promyelocytic leukemias with t(11;17)(q23;q22), thus providing further evidence of heterogeneity of breakpoints in 11q23 in acute leukemia. Rearrangements of immunoglobulin (IG) and T-cell receptor (TCR) genes were also observed, with no immunophenotypic evidence for commitment to the lymphoid lineages, indicating that inappropriate activation of the recombinases may be a feature of this particular variant translocation.