Potential Leukemic Cells Engraftment After Hematopoietic Stem Cell Transplantation From Unrelated Donors With Undiagnosed Chronic Leukemia

BACKGROUND

Donor-related neoplasms are a potential complication of treatment strategies involving stem cell transplantation. Although mechanisms for detection of short-term complications after these procedures are well developed, complications with delayed onset, notably transmission of chronic diseases such as chronic myeloid leukemia (CML), have been difficult to assess. Consequently, we studied the potential of human CML cells to engraft hematopoietic tissues after intravenous implantation in mice.

METHODS

Human peripheral blood cells, collected from CML patients presenting with moderately increased white blood cells count before treatment, were transplanted into sub-lethally irradiated, immunodeficient mice. Five weeks after transplantation the nuclear cells were isolated from the murine bone marrow, spleen, and peripheral blood and were used to quantitatively detect human CD45 antigen by flow cytometry; qRT-PCR was used to detect the BCR-ABL1 fusion gene, and the human or murine beta-glucuronidase housekeeping gene was used to examine human-murine chimerism.

RESULTS

We found that all evaluated animals had donor chimerism at the selected interval after transplant and the presence of a specific BCR-ABL1 fusion gene transcript was also detected.

CONCLUSIONS

Our results suggest that the risk of neoplasm transmission cannot be eliminated during hematopoietic stem cell transplantation from undiagnosed CML donors with borderline leukocytosis. The obtained data confirms the potential of leukemic cells to viably engraft the hematopoietic organs post-transplantation in an immunosuppressed recipient.

Coexistence of JAK2 or CALR mutation is a rare but clinically important event in chronic myeloid leukemia patients treated with tyrosine kinase inhibitors

INTRODUCTION

There are 7 designated conditions under the category of myeloproliferative neoplasms (MPN), including chronic myelogenous leukemia (CML) and classical MPN, that is, polycythemia vera (PV), essential thrombocythaemia (ET), and primary myelofibrosis (PMF). Recently, reports about Philadelphia and JAK2 V617F-positive MPN cases have been described in literature. The coexistence of different molecular defects may change the clinical and laboratory manifestation of MPN and may result in an inappropriate interpretation of the response to treatment with tyrosine kinase inhibitors in CML patients.

METHODS

The morphological, cytogenetic, and molecular genetic data from a retrospective analysis of 592 adult patients aged 18-86 years diagnosed with CML were analyzed.

RESULTS

In 5 CML patients, the presence of JAK2 V617F or CALR mutation was confirmed. Three of 4 TKI-treated patients did not reach complete hematologic response due to the persistence of thrombocytosis and/or splenomegaly. In all of them (in 3 with JAK2 V617F mutation and 1 with CALR mutation), thrombocytosis was present at the time when complete cytogenetic response was documented. In 3 out of 4 reported CML patients, thrombocytosis and/or splenomegaly were still present even at the time when deep molecular response was reached.

CONCLUSION

In our opinion, a detailed evaluation and appropriate interpretation of clinical and laboratory data in such a category of patients seem to be extremely important, especially when a decision about the TKI change due to therapy failure is considered.

Development and evaluation of a secondary reference panel for BCR-ABL1 quantification on the International Scale

Molecular monitoring of chronic myeloid leukemia patients using robust BCR-ABL1 tests standardized to the International Scale (IS) is key to proper disease management, especially when treatment cessation is considered. Most laboratories currently use a time-consuming sample exchange process with reference laboratories for IS calibration. A World Health Organization (WHO) BCR-ABL1 reference panel was developed (MR¹–MR⁴), but access to the material is limited. In this study, we describe the development of the first cell-based secondary reference panel that is traceable to and faithfully replicates the WHO panel, with an additional MR^4.5 level. The secondary panel was calibrated to IS using digital PCR with ABL1, BCR and GUSB as reference genes and evaluated by 44 laboratories worldwide. Interestingly, we found that >40% of BCR-ABL1 assays showed signs of inadequate optimization such as poor linearity and suboptimal PCR efficiency. Nonetheless, when optimized sample inputs were used, >60% demonstrated satisfactory IS accuracy, precision and/or MR^4.5 sensitivity, and 58% obtained IS conversion factors from the secondary reference concordant with their current values. Correlation analysis indicated no significant alterations in %BCR-ABL1 results caused by different assay configurations. More assays achieved good precision and/or sensitivity than IS accuracy, indicating the need for better IS calibration mechanisms.