Hyun-Gyung Goh

Allele frequencies of 15 STR loci using AmpF/STR Identifiler kit in a Korean population

The genetic variations for 15 short tandem repeat (STR) loci D8S1179, D21S11, D7S820, CSF1PO, D3S1358, TH01, D13S317, D16S539, D2S1338, D19S433, vWA, TPOX, D18S51, D5S818 and FGA were performed on 231 unrelated Korean population using commercially available AmpF/STR Identifiler kit.

Sensitive quantitation of minimal residual disease in chronic myeloid leukemia using nanofluidic digital polymerase chain reaction assay.

Undetectable BCR–ABL transcripts in patients with chronic myeloid leukemia (CML) should not be regarded as indicative of a cure, due to the sensitivity limit of current real-time quantitative polymerase chain reaction (RQ-PCR) technology. To demonstrate the feasibility of more sensitive approaches, 62 samples from 43 patients with CML were screened by conventional RQ-PCR, replicate RQ-PCR (rRQ-PCR), and/or nanofluidic digital PCR (dPCR). First, we confirmed the correlation of dPCR to conventional RQ-PCR using 30 patient samples with various minimal residual disease (MRD) levels. When the sensitivity limits were determined using cell line and patient sample dilutions, rRQ-PCR and dPCR with pre-amplification showed 2–3 log improvement compared to conventional RQ-PCR, and 24 of 32 PCR negative samples as assayed by conventional RQ-PCR showed detectable BCR–ABL in rRQ-PCR and/or dPCR. More important, using dPCR in conjunction with a pre-amplification step, a continuous decline in MRD level could be precisely monitored even after it became undetectable by conventional RQ-PCR. In this study, both rRQ-PCR and dPCR demonstrated successful detection of BCR–ABL transcripts not detectable in conventional RQ-PCR, and these data show the potential feasibility of highly sensitive PCR approaches for molecular monitoring and clinical relevance in future CML management by allowing further characterization of patients who achieve PCR negativity in a conventional RQ-PCR assay.

Previous best responses can be re-achieved by resumption after imatinib discontinuation in patients with chronic myeloid leukemia: implication for intermittent imatinib therapy.

Although imatinib is considered as a front line therapy in patients with chronic myeloid leukemia (CML), it is still unclear whether transient imatinib discontinuation may adversely affect the outcome. This study was conducted to investigate long-term outcome after discontinuation and resumption of imatinib, and to determine whether intermittent imatinib therapy can be employed in patients with CML. Twenty six Philadelphia chromosome positive (Ph+) patients with CML discontinued imatinib when they achieved complete cytogenetic response (CCyR) or complete molecular response (CMR), and they were retreated with imatinib in case of hematologic, cytogenetic or molecular relapse. Except one patient who progressed and two patients who are in persistent molecular remission without imatinib resumption, all of 23 patients are maintaining the best response achieved after imatinib resumption with a median follow-up of 44 months. This study shows that although imatinib cannot be discontinued completely, intermittent therapy can be considered for the treatment of patients with CML in particular situations.

Analysis of Bcr‐Abl kinase domain mutations in Korean chronic myeloid leukaemia patients: poor clinical outcome of P‐loop and T315I mutation is disease phase dependent

Despite durable responses to imatinib in chronic myeloid leukaemia (CML), mutations in Bcr‐Abl kinase domain (KD) are known to induce imatinib resistance and cause poor clinical outcome. We characterized Bcr‐Abl KD mutations in 137 Korean CML patients with imatinib resistance (n = 111) or intolerance (n = 26) using allele specific oligonucleotide polymerase chain reaction (PCR) and direct sequencing. Seventy (51%) patients harboured 81 mutations of 20 different types with increasing prevalence in advanced phase. Nine (13%) patients had multiple mutations. No mutation was found in intolerant patients. T315I was the most common mutation and P‐loop was the hottest spot in Bcr‐Abl KD. Patients harbouring P‐loop mutation, T315I, or multiple mutations showed poor overall survival and progression free survival compared with patients harbouring other mutations. Survival analysis according to disease phase of mutation being detected and type of mutations provided correlation between P‐loop or T315I mutation and poor overall survival in blast crisis, but not in accelerated phase (AP) or chronic phase (CP), indicating poor clinical outcome of particular mutations depends on disease phase. CML patients with imatinib resistance showed high rate (63%) of mutations in Bcr‐Abl KD and therefore CML patients who do not respond to imatinib should be the candidates for mutation screening as molecular monitoring. Copyright

Long-term pattern of pleural effusion from chronic myeloid leukemia patients in second-line dasatinib therapy.

Dasatinib is a potent second-generation tyrosine kinase inhibitor approved for the treatment of chronic myeloid leukemia after imatinib failure. However, some patients treated with dasatinib experience pleural effusions (PEs). The determinants of pleural effusion in long-term dasatinib treatment (median 35 months, range 1–55) were investigated in single-center data of 65 patients enrolled in global phase 2 and phase 3 trials. Of the 65 patients, 35 (54%) developed dasatinib-induced pleural effusion (a median onset time, 20 months; range 0.2–54). The first pleural effusion developed in 15 (43%) patients within 12 months of dasatinib therapy. Disease phase (P = 0.02), dose schedule (P = 0.002) and actual daily mean dose (P = 0.0002) were significantly associated with an increased risk of pleural effusion. Twice-daily administration of dasatinib resulted in significantly more patients developing pleural effusions compared with the once-daily dosing schedule, particularly in advanced disease. In addition, a strong correlation was found between actual daily mean dose and time to onset of pleural effusions in patients treated with a daily mean dose >100 mg/day of dasatinib (P = 0.01). These data emphasize the need for dasatinib dose and schedule optimization and long-term monitoring of dasatinib-treated patients to prevent the negative clinical implications of pleural effusion.

Chronic myeloid leukemia in the Asia-Pacific region: Current practice, challenges and opportunities in the targeted therapy era

Chronic myeloid leukemia (CML) management varies across Asia due to disparities in affluence and healthcare provision. We surveyed CML management practice at 33 hospitals in 14 countries/regions to identify treatment challenges and opportunities for harmonization. Patients were generally treated according to international guidelines; however, tyrosine kinase inhibitors (TKIs) and molecular monitoring are inaccessible to many patients not covered by national insurance or eligible for subsidized treatment. Late diagnosis and suboptimal monitoring, often due to cost and accessibility issues, are challenges. Priorities for Asia include: extending accessibility to TKIs; specialist laboratory monitoring; and enriching data to support regional CML management guidelines.

Structural modeling of V299L and E459K Bcr-Abl mutation, and sequential therapy of tyrosine kinase inhibitors for the compound mutations

Sequential treatment with different tyrosine kinase inhibitors (TKIs) is one of the strategies for handling chronic myeloid leukemia (CML) in which dynamic change in Bcr-Abl kinase domain mutation is often an obstacle faced during TKI therapy. Here we report successful sequential therapy with different TKIs for the CML patient harboring V299L and E459K compound mutations. Molecular monitoring including quantitative analysis of BCR-ABL transcript level and mutation analysis were performed regularly for successful treatment. Additionally a drug-target complex was structurally modeled to investigate influence of amino acid substitutions on drug resistance, and to choose alternative TKI in sequential therapy, suggesting protein structural modeling can be useful approach in selecting alternative TKIs.

Dynamic change of T315I BCR-ABL kinase domain mutation in Korean chronic myeloid leukaemia patients during treatment with Abl tyrosine kinase inhibitors.

We analysed the dynamic change of imatinib‐resistant mutations in BCR‐ABL kinase domain focusing on T315I mutation during dasatinib or nilotinib therapy. Fifty‐five imatinib‐resistant chronic myeloid leukaemia patients (32 patients with imatinib‐resistant mutations and 23 patients without mutation) in different disease phases were treated with dasatinib (median 17.3 months) or nilotinib (median 6.8 months). Among the 32 patients with baseline mutation, mutations including M244V, G250E, E255K, M351T, H396R, S417Y, E450K and E459K disappeared in 8 patients and new mutations were detected in 9 patients, all of which were T315I. Among the 23 patients without baseline mutation, 4 patients showed newly developed mutations including T315I, T315I + E459K, M244V and F359V. The T315I was the most frequently detected mutation in imatinib therapy (16%, 9 of 55) as well as in dasatinib or nilotinib therapy (24%, 11 of 44). Patients with imatinib resistant baseline mutations had a higher rate of mutation development during dasatinib or nilotinib treatment compared to patients without baseline mutations (28% vs. 17%). Copyright