Primarily due to recent advances of detection techniques, microchimerism (the proportion of minor variant population is below 1%) has recently gained increasing attention in the field of transplantation. Availability of polymorphic markers, such as deletion insertion or single nucleotide polymorphisms along with a vast array of high sensitivity detection techniques, allow the accurate detection of small quantities of donor- or recipient-related materials. This diagnostic information can improve monitoring of allograft injuries in solid organ transplantations (SOT) as well as facilitate early detection of relapse in allogeneic hematopoietic stem cell transplantation (allo-HSCT). In the present review, genetic marker and detection platform options applicable for microchimerism detection are discussed. Furthermore, current results of relevant clinical studies in the context of microchimerism and SOT or allo-HSCT respectively are also summarized.
Monitoring measurable residual disease (MRD) in acute myeloid leukemia (AML) plays an important role in predicting relapse and outcome. The applicability of the leukemia-initiating nucleophosmin1 (NPM1) gene mutations in MRD detection is well-established, while that of isocitrate dehydrogenase1/2 (IDH1/2) mutations are matter of debate. The aim of this study was to investigate the stability of NPM1 and IDH1/2 mutations at diagnosis and relapse retrospectively in 916 adult AML patients. The prognostic value of MRD was evaluated by droplet digital PCR on the DNA level in a selected subgroup of patients in remission. NPM1 re-emerged at relapse in 91% (72/79), while IDH1/2 in 87% (20/23) of mutation-positive cases at diagnosis. NPM1 mutation did not develop at relapse, on the contrary novel IDH1/2 mutations occurred in 3% (3/93) of previously mutation-negative cases. NPM1 MRD-positivity after induction (n = 116) proved to be an independent, adverse risk factor (MRDpos 24-month OS: 39.3±6.2% versus MRDneg: 58.5±7.5%, p = 0.029; HR: 2.16; 95%CI: 1.25–3.74, p = 0.006). In the favorable subgroup of mutated NPM1 without fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) or with low allelic ratio, NPM1 MRD provides a valuable prognostic biomarker (NPM1 MRDpos versus MRDneg 24-month OS: 42.9±6.7% versus 66.7±8.6%; p = 0.01). IDH1/2 MRD-positivity after induction (n = 62) was also associated with poor survival (MRDpos 24-month OS: 41.3±9.2% versus MRDneg: 62.5±9.0%, p = 0.003; HR 2.81 95%CI 1.09–7.23, p = 0.032). While NPM1 variant allele frequency decreased below 2.5% in remission in all patients, IDH1/2 mutations (typically IDH2 R140Q) persisted in 24% of cases. Our results support that NPM1 MRD even at DNA level is a reliable prognostic factor, while IDH1/2 mutations may represent pre-leukemic, founder or subclonal drivers.
Összefoglaló. Bevezetés: Az allogén hematopoetikus őssejt-transzplantáció (allo-HSCT) kiemelkedő szerepet tölt be a hematológiai betegségek gyógyításában. A kimérizmusvizsgálat a donor és a recipiens típusú vérképzés jelenlétét különíti el örökletes genetikai markerek segítségével. Az allo-HSCT kimenetele (pl. az engraftment dinamikája vagy a relapsus előrejelzése) jól követhető kimérizmusvizsgálatokkal, akár a betegségspecifikus markerek hiányában is. Célkitűzés: Munkánk során a kimérizmusvizsgálatok terén arany standardnak számító short tandem repeat (STR) és a fluoreszcens in situ hibridizáció (FISH) módszereket hasonlítottuk össze, valamint vizsgáltuk az allo-HSCT kimenetelét a kimérizmuseredményektől függően. Módszer: Az STR és FISH módszerek összehasonlítását 2018-ban gyűjtött, a két különböző vizsgálatra ugyanazon a napon beküldött 210 mintán végeztük. A kimérizmusvizsgálatok klinikai jelentőségét 2015. január és 2018. február között 378 allogén HSCT-n átesett beteg adatainak elemzésével vizsgáltuk. Eredmények: A két vizsgálati módszerrel kapott eredmények 95,2%-ban megegyeztek. A teljes kimérizmust elért betegek (n = 311) összesített túlélése (OS) kedvezőbb volt, mint azoké, akik nem értek el teljes kimérizmust (n = 44; OS 24 hónapban: 59,4% vs. 23,6%; p < 0,001). Következtetések: Vizsgálatunkban a két kimérizmusvizsgálati módszer (STR és FISH) eredményei jól korreláltak egymással, mindkettő alkalmasnak bizonyult a betegek allo-HSCT utáni követésére. A teljes donorkimérizmus elérése szignifikánsan jobb túléléssel társult. A kevert kimérizmus hatékonyan visszafordítható donor lymphocytainfúzió adásával, mely fokozza a graft alloreaktivitását. Summary. Introduction: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) plays a pivotal role in the cure of hematologic malignancies. Chimerism testing can differentiate recipient and donor hematopoiesis by hereditary genetic markers. The outcome of allo-HSCT (e.g. the dynamics of engraftment and the prediction of relapse) can be monitored by chimerism testing even in the case of lacking disease specific markers. Aims: In the current study we compared the gold standard short tandem repeat (STR) and the fluorescent in situ hybridization (FISH) chimerism testing methods; and we examined the outcome of allo-HSCT depending on chimerism results. Methods: The comparison of STR and FISH methods was performed on 210 samples parallelly tested for chimerism by both methods on the same day in 2018. The clinical significance of chimerism testing was investigated by clinical data analysis of 378 patients treated by allo-HSCT between 1 January 2015 and 28 February 2018. Results: Chimerism results tested by the two methods showed 95.2% concordance. Patients with complete donor chimerism (n = 311) had a more favourable overall survival (OS) than patients without complete donor chimerism (n = 44; OS at 24 month years 59.4% vs. 23.6%, respectively, p < 0.001). Conclusion: In our comparison both chimerism testing methods correlated well, and proved to be suitable for chimerism monitoring after allo-HSCT. Achieving complete donor chimerism was associated with better survival. In case of mixed chimerism, donor lymphocyte infusion can be an effective therapeutic option since it increases graft alloreactivity.
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