Purpose: Leukemic stem cells (LSCs) may harbor important resistance to tyrosine kinase inhibitors in chronic myelogenous leukemia (CML). We identified Philadelphia chromosome (Ph)–positive CD34+CD38− bone marrow cells (here denoted LSCs) and addressed their response-predictive value in patients with CML (n = 48) subjected to nilotinib in the ENEST1st trial (NCT01061177). Experimental design: Two flow cytometry–based cell sorting methods were used with multiparameter-directed CD45- (MPFC) and BCR-ABL1 probe-linked (FISH) identification of Ph-positive cells, respectively. Results: We observed a positive correlation between the proportion of LSCs at diagnosis and established prognostic markers (blast count, spleen size, Sokal score, and hemoglobin). Conversely, a high LSC burden predicted for an inferior molecular response at 3 (MPFC and FISH), 6 (MPFC), 9 (FISH), and 15 months (FISH). During nilotinib therapy, the proportion of LSCs decreased rapidly. At 3 months, a median of only 0.3% LSCs remained among CD34+CD38− cells, and in 33% of the patients the LSC clone was not detectable anymore (FISH). The response kinetics was similar in LSC fractions as it was in the progenitor and unseparated bone marrow cell fractions. Conclusions: The proportion of LSCs at diagnosis, as analyzed by two independent methodologies, reflects the biology of the disease and appeared as a prognostic and response-predictive marker in patients with CML subjected to first-line nilotinib therapy. Clin Cancer Res; 22(16); 4030–8. ©2016 AACR.

Purpose Immunologic surveillance of minimal residual disease in chronic myelogenous leukemia (CML) may be relevant for long-term control or cure of CML. Little is known about immune-modulatory effects of nilotinib in vivo, potentially predicting response to therapy. Patients and Methods A prospective and comprehensive flow cytometry-based immunomonitoring program paralleled the ENEST1st clinical study, investigating 52 nilotinib-naïve patients with chronic-phase CML. Data were verified in independent validation cohorts. Results T cells of patients with CML at diagnosis expressed low l-selectin (CD62L) levels, which was not a result of proportional aberrations of T-cell subsets. Low numbers of CD62L-expressing CD4 and CD8 T cells correlated with higher Sokal score, increased spleen size, and high leukocyte and peripheral-blood blast counts. At month 6 during nilotinib therapy, CD62L expression returned to levels of healthy individuals. The level of CD62L loss on T cells directly correlated with the extent of soluble CD62L (sCD62L) elevation. In parallel, the proteolytic activity of tumor necrosis factor α-converting enzyme (TACE; ADAM17, CD156b), the metalloproteinase shedding CD62L, was increased at diagnosis and significantly decreased during nilotinib treatment. High CD62L expression on both CD4 and CD8 T cells and, vice versa, low sCD62L levels at CML diagnosis were linked to superior molecular responses. These findings were corroborated in independent validation cohorts. Conclusion We demonstrate the prognostic impact of CD62L shedding from T cells and increased sCD62L plasma levels at CML diagnosis on molecular response to tyrosine kinase inhibitor therapy in early chronic-phase CML. Functionally, decreased CD62L may be a consequence of increased TACE-mediated CD62L cleavage and potentially impairs immune-cell function. Larger prospective studies are ongoing to confirm the prognostic relevance of this finding.

Background The Covid-19 pandemic has created the largest disruption of education in history. In a response to this, we aimed to evaluate the knee arthroscopy learning curve among medical students and orthopaedic residents. Methods An arthroscopy simulator was used to compare the learning curves of two groups. Medical students with any prior knowledge of arthroscopy ( n=24) were compared to a residents group ( n=16). Analyzed parameters were “time to complete a task,” assessment of the movement of tools and values scoring damage to the surrounding tissues. Results After several repetitions, both groups improved their skills in terms of time and movement. Residents were on average faster, had less camera movement, and touched the cartilage tissue less often than did students. Students showed a steeper improvement curve than residents for certain parameters, as they started from a different experience level. Conclusion The participants were able to reduce the time to complete a task. There was also a decrease in possible damage to the virtual surrounding tissues. In general, the residents had better mean values, but the students had the steeper learning curve. Particularly less experienced surgeons can especially train their hand–eye coordination skills required for arthroscopy surgery. Training simulators are an important training tool that supplements cadaveric training and participation in arthroscopic operations and should be included in training.