The clinical value of circulating free tumor DNA in testicular germ cell tumor patients.

BACKGROUND: Testicular germ cell tumors (TGCT) are unique malignancies of young adult men; their biology is, however, underexplored and there has not been much progress in their treatment for decades. Circulating free tumor DNA (cfDNA) analysis represents a promising way of discovering novel diagnostic and treatment options. OBJECTIVE: The study evaluates the clinical value of cfDNA detection in TGCT patients. DESIGN AND METHODS: Total cfDNA concentration and ratio of its 2 main fragments (180 and 360 bp) were evaluated by spectrophotometry, capillary electrophoresis and qPCR in peripheral blood plasma of 96 TGCT patients (173 samples) and 31 normal controls. Non-parametric tests were used for statistical analyses. RESULTS: The total cfDNA concentration was significantly higher in TGCT than in controls (P < 0.0001), with the highest levels at disease progression, but with no clear threshold between malignant and normal samples. Patients with positive tumor markers had higher cfDNA concentrations than those with negative markers (P = 0.01). Longer 360 bp cfDNA fragments were found in 58% of TGCT patients including almost all samples from relapse or disease progression but no normal controls (P < 0.0001). CONCLUSION: Total cfDNA levels are significantly increased in TGCT patients but without a clear threshold separating normal and tumor samples, thus total cfDNA amount itself is not a sensitive enough marker to identify or monitor TGCT. Longer cfDNA fragments have been found exclusively in a proportion of tumors and predominantly at disease progression, representing a novel potential marker for TGCT monitoring that would deserve further exploration.

Low HOX gene expression in PML-RARα-positive leukemia results from suppressed histone demethylation.

Homeobox (HOX) genes are frequently dysregulated in leukemia. Previous studies have shown that aberrant HOX gene expression accompanies leukemogenesis and affects disease progression and leukemia patient survival. Patients with acute myeloid leukemia (AML) bearing PML-RARα fusion gene have distinct HOX gene signature in comparison to other subtypes of AML patients, although the mechanism of transcription regulation is not completely understood. We previously found an association between the mRNA levels of HOX genes and those of the histone demethylases JMJD3 and UTX in PML-RARα- positive leukemia patients. Here, we demonstrate that the release of the PML-RARα-mediated block in PML-RARα-positive myeloid leukemia cells increased both JMJD3 and HOX gene expression, while inhibition of JMJD3 using the specific inhibitor GSK-J4 reversed the effect. This effect was driven specifically through PML-RARα fusion protein since expression changes did not occur in cells with mutated RARα and was independent of differentiation. We confirmed that gene expression levels were inversely correlated with alterations in H3K27me3 histone marks localized at HOX gene promoters. Furthermore, data from chromatin immunoprecipitation followed by sequencing broaden a list of clustered HOX genes regulated by JMJD3 in PML-RARα-positive leukemic cells. Interestingly, the combination of GSK-J4 and all-trans retinoic acid (ATRA) significantly increased PML-RARα-positive cell apoptosis compared with ATRA treatment alone. This effect was also observed in ATRA-resistant NB4 clones, which may provide a new therapeutic opportunity for patients with acute promyelocytic leukemia (APL) resistant to current treatment. The results of our study reveal the mechanism of HOX gene expression regulation and contribute to our understanding of APL pathogenesis.