No abstract

No abstract

Background. Multiple myeloma complicated by extramedullary plasmacytoma is an unfavorable variant of the disease. It remains unknown what triggers tumor transformation. The review presents literature data on the pathogenesis of extramedullary disease, as well as a clinical example of a comprehensive study of the tumor substrate.Aim. To study the molecular and biological characteristics of the tumor substrate of the bone marrow and extramedullary plasmacytoma using various research methods.Materials and methods. A 55-year-old patient was admitted to National Medical Research Center for Hematology with a diagnosis of multiple myeloma occurring with extramedullary plasmacytoma of the retroperitoneal space. dNA was isolated from samples of different localization (blood plasma, Cd138+ bone marrow cells, plasmacytoma and buccal epithelial cells). The profile of short tandem dNA repeats (STR) from the obtained samples was studied by multiplex polymerase chain reaction followed by fragment analysis. fluorescent in situ hybridization (fISH) of bone marrow Cd138+ cells was performed using various dNA probes. Comparative genomic hybridization on a microarray (arrayCGH) plasmacytoma dNA was also performed. The mutation profile of the KRAS, NRAS, BRAF genes was studied by Sanger sequencing in tumor samples of various localizations.Results. The induction therapy (vCd (bortezomib + cyclophosphamide + dexamethasone), vRd (bortezomib + lenalidomide + dexamethasone), daratumumab therapy) was ineffective, death occurred 4 months after the first clinical manifestations appeared. Comparison of STR markers of circulating cell-free tumor dNA (cfdNA), Cd138+ bone marrow cells, and plasmacytoma revealed the largest number of involved loci exactly in plasmacytoma’ dNA. A mutation in the NRAS gene was found only in plasmacytoma’ dNA. This indicates the presence of another clone of tumor cells in the extra-medullary plasmacytoma. Molecular karyotyping of plasmacytoma using the arrayCGH method revealed rearrangements of many chromosomes. 1p32.3 bi-allelic deletion, amplification of 1q21, 8q24/MyC rearrangements and del17p13 were confirmed by arrayCGH molecular karyotyping and fISH studies in bone marrow and plasmacytoma.Conclusion. A comprehensive molecular genetic study of the extramedullary plasmacytoma’ substrate is necessary to understand the pathogenesis mechanisms and, on this basis, to develop differentiated therapeutic approaches.

Multiple myeloma (MM) is characterized by heterogeneity of tumor cells. The study of tumor cells from blood, bone marrow, plasmacytoma, etc., allows us to identify similarities and differences in tumor lesions of various anatomical localizations. The aim of this study was to compare the loss of heterozygosity (LOH) by tumor cells by assessing STR profiles of different MM lesions. We examined paired samples of plasma circulating tumor DNA (ctDNA) and CD138+ bone marrow cells in MM patients. For patients with plasmacytomas (66% of 38 patients included), the STR profile of plasmacytomas was also studied when biopsy samples were available. Diverse patterns of LOH were found in lesions of different localization for most patients. LOH in plasma ctDNA, bone marrow, and plasmacytoma samples was found for 55%, 71%, and 100% of patients, respectively. One could expect a greater variety of STR profiles in aberrant loci for patients with plasmacytomas. This hypothesis was not confirmed—no difference in the frequency of LOH in MM patients with or without plasmacytomas was found. This indicates the genetic diversity of tumor clones in MM, regardless of the presence of extramedullar lesions. Therefore, we conclude that risk stratification based on molecular tests performed solely on bone marrow samples may not be sufficient for all MM patients, including those without plasmacytomas. Due to genetic heterogeneity of MM tumor cells from various lesions, the high diagnostic value of liquid biopsy approaches becomes obvious.

Context: TPMTandNUDT15polymorphisms are involved in the toxicity and therapeutic efficacy of thiopurine drugs (6-mercaptopurine (6-MP)). The frequencies of polymorphisms of these genes are different across diverse populations. The role ofTPMTandNUDT15genes in adult patients (pts) with Ph-negative acute lymphoblastic leukemia (ALL) in Russia is still unclear. Objective:Evaluation of frequency and significance ofTPMTandNUDT15polymorphisms in the cohort of adult Ph-negative ALL pts treated by the RALL-2016 protocol. Design and Patients:Since April 2017 till July 2020 56 adult Ph-negative ALL patients treated by RALL-2016 protocol were included in the research ofTPMTandNUDT15polymorphisms. Median age was 32 у (range, 18-54), m/f: 39 (70%) / 17 (30%). B-ALL/LBL were diagnosed in 26 (46,4%) pts, T-ALL- in 26 (46,4%) and MPAL- in 4 (7,2%). Genomic DNA was extracted from peripheral blood samples of given pts. Genetic polymorphisms inNUDT15(*2, *3)and TPMT(*2, *3A, *3B, *3C)genes were detected using the allele-specific RT-PCR. The dose of 6-MP was calculated only for 54 pts from 56 (one of these pts stopped the therapy and another received the 1 st phase of induction by RALL-2016 without 6-MP). According to the RALL-2016 protocol 6-MP dose correction imply: if the level leukocytes<2,0*109/l, thrombocytes <100*109/l pts got 50% from the required dose. The therapy of 6-MP was stopped, if the level leukocytes <1,0*109/l, thrombocytes <50*109/l. On the 2 induction therapy by the protocol, the doses of 6-MP were calculated only for 47 pts with CR. The group of pts who didn't have remission on the 36 day by the protocol took the drug without corrections. Results:From 54 pts CR rate was 87 % (n=47) and resistance - 13% (n=7). One patient died in CR. The frequency ofTPMTandNUDT15polymorphisms in study group was 17,8 % (n=10): 6 (23%) of 26 pts with B-ALL, 3 (11,5 %) of 26 pts -T-ALL and 1 (25%) of 4 pts - MPAL. In our cohort these polymorphisms were found significantly more frequently in pts with B-ALL (p<0.001). These polymorphisms were detected in 8 (80%) men and 2 (20%) women (p=0.432). All detected polymorphisms were presented as heterozygous variants:NUDT15*3was in 2 (20%) pts,TPMT*2-1(10%),TPMT*3A-6 (60%),TPMT*3C-1 (10%). The doses of 6-MP in 5 pts withTPMTandNUDT15and 42 pts withWTwere 54% (27-89%) vs 71% (25-100%), respectively. Statistics analysis didn't show correlation between the 6-MP toxicity (difference of the fact dose of 6-MP therapy) and the polymorphisms in our cohort (fig.1). The frequency of resistance cases didn't different in cohort with/withoutTPMTandNUDT15polymorphisms in 3 (37, 5%) from 8 pts and 4 (10, 5%) from 42 pts, respectively. Only 1 patient with heterozygousTPMT*2died in CR due to toxicity and infection. Two-years overall survival (OS) in pts with the genetic polymorphisms was worse 75 % than in pts without them - 83,6% (p=0,67) (fig.2). Conclusions:In our study the frequency ofTPMTandNUDT15polymorphisms in adult pts with Ph-negative ALL was 17,8%. The statistical analysis showed that polymorphisms of these genes were detected more frequently in pts with В-ALL. Only one patient withTPMT*2had significant toxicity on the therapy of 6-MP and died in CR. However, we don't know whether this is due to deficient 6-MP metabolism. We didn't find a correlation between the 6-MP toxicity and the polymorphisms in our pts. There is a tendency that OS within 2-years in pts withoutTPMTandNUDT15polymorphisms is better than in the group of pts with them. But our cohorts are small and require further study. Keywords:acute lymphoblastic leukemia, toxicity, 6-mercaptopurine,TPMT,NUDT15 Disclosures No relevant conflicts of interest to declare.