Loss of Heterozygosity and Mutations in the RAS-ERK Pathway Genes in Tumor Cells of Various Loci in Multiple Myeloma.

Multiple myeloma (MM) is a disease characterized by spatiotemporal heterogeneity of tumor clones. Different genetic aberrations can be observed simultaneously in tumor cells from different loci, and as the disease progresses, new subclones may appear. The role of liquid biopsy, which is based on the analysis of tumor DNA circulating in the blood plasma, continues to be explored in MM. Here, we present an analysis of the STR profiles and mutation status of the KRAS, NRAS, and BRAF genes, evaluated in plasma free circulating tumor DNA (ctDNA), CD138+ bone marrow cells, and plasmacytomas. The prospective single-center study included 97 patients, with a median age of 55 years. Of these, 94 had newly diagnosed symptomatic MM, and three had primary plasma cell leukemia. It should be noted that if mutations were detected only in ctDNA, "non-classical" codons were more often affected. A variety of adverse laboratory and clinical factors have been associated with the detection of rare KRAS or NRAS gene mutations in bone marrow or ctDNA, suggesting that these mutations may be factors of an unfavorable prognosis for MM. Liquid biopsy studies provide undeniable fundamental information about tumor heterogeneity and clonal evolution in MM. Moreover, we focus on using liquid biopsy to identify new high-risk factors for MM.

Loss of Heterozygosity in the Circulating Tumor DNA and CD138+ Bone Marrow Cells in Multiple Myeloma.

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.

Inhibitor of BRAFV600E Mutation as a Treatment Option for Hairy Cell Leukemia With Deep Neutropenia and Infectious Complications.

Standard therapy in hairy cell leukemia (HCL) is often impossible at the time of deep neutropenia/agranulocytosis with or without infectious complications; it is thus a complex therapeutic problem. Vemurafenib has been used to treat resistant HCL since 2012. Because vemurafenib does not have a myelotoxic effect, we thought that it could be used to treat HCL associated with deep neutropenia/agranulocytosis with or without the development of infectious complications as a preliminary stage before treatment with cladribine. We conducted a retrospective analysis of treatment with vemurafenib followed by a standard course of cladribine provided to 22 patients with deep neutropenia/agranulocytosis with or without infectious complications at diagnosis. Vemurafenib was provided to 22 patients with HCL. The response to therapy was evaluated by complete blood cell count (absolute neutrophil count [ANC], hemoglobin concentration, platelet count, absence of hairy cells), spleen size (assessed by ultrasound), and reduce infectious complications. After that, a standard course of cladribine was provided. Among the 22 patients, the male/female sex ratio was 2:1, and median (range) age was 52 (24-78) years. There were 7 patients with severe infectious manifestations admitted to the intensive care unit, including 1 patient during extracorporeal membrane oxygenation. The median (range) ANC at diagnosis was 0.3 (0.04-0.7) × 109/L. Vemurafenib was provided at a dosage of 240 mg 1 or 2 times a day. In 20 patients, vemurafenib was provided for 3 months or more. In 1 case, the effect was not obtained during 1 month of treatment, and the patient died from severe infectious complications during prolonged agranulocytosis. In 21 patients treated with vemurafenib, an increase of ANC was observed and the infectious complications resolved, thus allowing the application of cladribine therapy. After a standard course (0.1 mg/kg per day for 7 days) of cladribine chemotherapy, 18 patients (90%) experienced complete clinical remission and 2 patients (10%) experienced partial remission with residual splenomegaly. In 1 patient, vemurafenib therapy was still ongoing 2 months after initiating therapy. In cases of proven BRAFV600E mutation, vemurafenib can be successfully used as an effective preliminary therapy in patients with deep neutropenia/agranulocytosis with or without infectious complications before standard therapy with purine analogs.