MYC gene amplification in double minute chromosomes in an aggressive large B-cell lymphoma with leukemic presentation: a case report

EYA2 tyrosine phosphatase inhibition reduces MYC and prevents medulloblastoma progression

BACKGROUND

Medulloblastoma is the most common pediatric brain malignancy. Patients with the Group 3 subtype of medulloblastoma (MB) often exhibit MYC amplification and/or overexpression and have the poorest prognosis. While Group 3 MB is known to be highly dependent on MYC, direct targeting of MYC remains elusive.

METHODS

Patient gene expression data were used to identify highly expressed EYA2 in Group 3 MB samples, assess the correlation between EYA2 and MYC, and examine patient survival. Genetic and pharmacological studies were performed on EYA2 in Group 3 derived MB cell models to assess MYC regulation and viability in vitro and in vivo.

RESULTS

EYA2 is more highly expressed in Group 3 MB than other MB subgroups and is essential for Group 3 MB growth in vitro and in vivo. EYA2 regulates MYC expression and protein stability in Group 3 MB, resulting in global alterations of MYC transcription. Inhibition of EYA2 tyrosine phosphatase activity, using a novel small molecule inhibitor (NCGC00249987, or 9987), significantly decreases Group 3 MB MYC expression in both flank and intracranial growth in vivo. Human MB RNA-seq data show that EYA2 and MYC are significantly positively correlated, high EYA2 expression is significantly associated with a MYC transcriptional signature, and patients with high EYA2 and MYC expression have worse prognoses than those that do not express both genes at high levels.

CONCLUSIONS

Our data demonstrate that EYA2 is a critical regulator of MYC in Group 3 MB and suggest a novel therapeutic avenue to target this highly lethal disease.

Hi-C detects novel structural variants in HL-60 and HL-60/S4 cell lines

Cancer cell lines often have large structural variants (SVs) that evolve over time. There are many reported differences in large scale SVs between HL-60 and HL-60/S4, two cell lines derived from the same acute myeloid leukemia sample. However, the stability and variability of inter- and intra-chromosomal structural variants between different sources of the same cell line is unknown. Here, we used Hi-C and RNA-seq to identify and compare large SVs in HL-60 and HL-60/S4 cell lines. Comparisons with previously published karyotypes identified novel SVs in both cell lines. Hi-C was used to characterize the known expansion centered on the MYC locus. The MYC expansion was integrated into known locations in HL-60/S4, and a novel location (chr4) in HL-60. The HL-60 cell line has more within-line structural variation than the HL-60/S4 derivative cell line. Collectively we demonstrate the usefulness of Hi-C and with RNA-seq data for the identification and characterization of SVs.

Successful treatment of both double minute of C-MYC and BCL-2 rearrangement containing large B-cell lymphoma with subsequent unfortunate development of therapy-related acute myeloid leukemia with t(3;3)(q26.2;q21)

Double minute chromosomes (DMs), although relatively frequently encountered in solid tumors, are rare in hematologic neoplasms such as acute myeloid leukemia (AML), and even rarer in lymphoid neoplasms. t(3;3)(q26.2;q21) is a very rare genetic alteration observed in myeloid neoplasm. Herein we report an interesting and unique case of concomitant C-MYC DMs and t(14;18)-containing large B-cell lymphoma, which was successfully treated with R-hyper-CVAD; unfortunately, the patient has developed a therapy-related AML (t-AML) 2 years since the start of his lymphoma treatment. His t-AML contains both t(3;3)(q26.2;q21) and monosomy 7, and the patient died of AML 10 months after the initial diagnosis of t-AML despite clinical remission. To the best of our knowledge, this is the first reported case of C-MYC DM-containing de novo large B-cell lymphoma, which was successfully treated with complete remission, but unfortunately died of t-AML harboring t(3;3)(q21;q26).