ctDNA improves prognostic prediction in relapsed/refractory MM receiving ixazomib, lenalidomide, and dexamethasone.

It remains elusive how driver mutations, including those detected in circulating tumor DNA (ctDNA), affect prognosis in relapsed/refractory multiple myeloma (RRMM). Here we performed targeted-capture sequencing using bone marrow plasma cells (BMPC) and ctDNA of 261 RRMM cases uniformly treated with ixazomib, lenalidomide, and dexamethasone in a multicenter, prospective, observational study. We detected 24 and 47 recurrently mutated genes in BMPC and ctDNA, respectively. In addition to clonal hematopoiesis-associated mutations, varying proportion of driver mutations, particularly TP53 mutations (59.2% of mutated cases), were present in only ctDNA, suggesting their subclonal origin. In univariable analyses, ctDNA mutations of KRAS, TP53, DIS3, BRAF, NRAS, and ATM were associated with worse progression-free survival (PFS). BMPC mutations of TP53 and KRAS were associated with inferior PFS, while KRAS mutations were prognostically relevant only when detected in both BMPC and ctDNA. A total number of ctDNA mutations in the six relevant genes was a strong prognostic predictor (2-year PFS rates: 57.3%, 22.7%, and 0% for 0, 1, and ≥ 2 mutations, respectively) and independent of clinical factors and plasma DNA concentration. Using the number of ctDNA mutations, plasma DNA concentration, and clinical factors, we developed a prognostic index (ctRRMM-PI), classifying patients into three categories with 2-year PFS rates of 57.9%, 28.6%, and 0%. Serial analysis of ctDNA mutations in 94 cases revealed that TP53 and KRAS mutations frequently emerge after therapy. Thus, we clarify the genetic characteristics and clonal architecture of ctDNA mutations and demonstrate their superiority over BMPC mutations for prognostic prediction in RRMM.

Primary analysis of a prospective cohort study of Japanese patients with plasma cell neoplasms in the novel drug era (2016-2021).

The emergence of novel drugs has significantly improved outcomes of patients with plasma cell neoplasms (PCN). The Japanese Society of Hematology conducted a prospective observational study in newly diagnosed PCN patients between 2016 and 2021. The analysis focused on 1385 patients diagnosed with symptomatic PCN between 2016 and 2018. The primary endpoint was the 3-year overall survival (OS) rate among patients requiring treatment (n = 1284), which was 70.0% (95%CI 67.4-72.6%). Approximately 94% of these patients received novel drugs as frontline therapy. The 3-year OS rate was 90.3% (95%CI 86.6-93.1%) in the 25% of patients who received upfront autologous stem cell transplantation (ASCT), versus just 61.4% (95%CI 58.0-64.6%) in those who did not receive upfront ASCT. The only unfavorable prognostic factor that affected OS in ASCT recipients was an age of 65 or higher. For patients who did not receive ASCT, independent unfavorable prognostic factors included frontline treatment with conventional chemotherapies, international staging system score of 2/3, extramedullary tumors, and Freiberg comorbidity index of 2/3. This study unequivocally demonstrates that use of novel drugs improved OS in Japanese myeloma patients, and underscores the continued importance of upfront ASCT as the standard of care in the era of novel drugs.

A prospective, multicenter, observational study of ixazomib plus lenalidomide-dexamethasone in patients with relapsed/refractory multiple myeloma in Japan.

Real-world studies permit inclusion of a more diverse patient population and provide more information on the effectiveness of treatments used in routine clinical practice. This prospective, multicenter, observational study investigated the effectiveness and safety of ixazomib plus lenalidomide and dexamethasone (IRd) in 295 patients with relapsed/refractory multiple myeloma (RRMM) in routine clinical practice in Japan. Patients had a median age of 74 years, 80.0% were aged ≥ 65 years, 42.0% had received ≥ 3 lines of prior treatment, and 28.5% were "frail" according to the International Myeloma Working Group frailty score. After a median follow-up of 25.0 months, median progression-free survival (PFS) was 15.3 (95% CI 12.4-19.5) months, while median overall survival was not reached. The overall response rate was 53.9%, and 31.5% of patients had a very good partial response or better. In the subgroup analysis, median PFS was better in patients with 1 versus 2 or ≥ 3 lines of prior treatment (29.0 vs 19.2 or 6.9 months) and paraprotein versus clinical relapse (16.0 vs 7.9 months), but median PFS was not notably affected by frailty score or age group. Dose adjustment was more frequent among patients aged > 75 years, especially early after IRd treatment initiation. Treatment-emergent adverse events (TEAEs) of any grade occurred in 84.4% of patients and 24.7% of patients discontinued treatment due to TEAEs; no new safety concerns were found. These findings suggest that oral IRd triplet regimen is an effective and tolerable treatment option for RRMM patients in real-world settings outside of clinical trials.ClinicalTrials.gov identifier: NCT03433001; Date of registration: 14 February 2018.

Immune checkpoint molecule DNAM-1/CD112 axis is a novel target for natural killer-cell therapy in acute myeloid leukemia.

Acute myeloid leukemia (AML) is a hematologic malignancy that frequently relapses, even if remission can be achieved with intensive chemotherapy. One known relapse mechanism is the escape of leukemic cells from immune surveillance. Currently, there is no effective immunotherapy for AML because of the lack of specific antigens. Here, we aimed to elucidate the association between CD155 and CD112 in AML cell lines and primary AML samples and determine the therapeutic response. Briefly, we generated NK-92 cell lines (NK-92) with modified DNAX-associated molecule 1 (DNAM-1) and T-cell immunoglobulin and ITIM domain (TIGIT), which are receptors of CD155 and CD112, respectively. Analysis of 200 cases of AML indicated that the survival of patients with high expression of CD112 was shorter than that of patients with low expression. NK-92 DNAM-1 exhibited enhanced cytotoxic activity against AML cell lines and primary cells derived from patients with AML. DNAM-1 induction in NK-92 cells enhanced the expression of cytotoxicity-related genes, thus overcoming the inhibitory activity of TIGIT. Between CD155 and CD112, CD112 is an especially important target for natural killer (NK)-cell therapy of AML. Using a xenograft model, we confirmed the enhanced antitumor effect of NK-92 DNAM-1 compared with that of NK-92 alone. We also discovered that CD112 (Nectin-2), an immune checkpoint molecule belonging to the Nectin/Nectin-like family, functions as a novel target of immunotherapy. In conclusion, modification of the DNAM-1/CD112 axis in NK cells may be an effective novel immunotherapy for AML. Furthermore, our findings suggest that the levels of expression of these molecules are potential prognostic markers in AML.

Guest Editorial: what can be done to improve cancer immunotherapies?

Cancer immunotherapies including immune checkpoint inhibitor and cell-based regimens such as chimeric antigen receptor T cell therapy have progressed markedly in the last decade. However, the efficacy of those cancer immunotherapies is still limited in some patient populations due to the many mechanisms of antitumor immunomodulation, including immune checkpoint molecules expressed by both tumor cells and the tumor microenvironment, immunosuppressive cells, and tumor cell-derived factors such as extracellular vesicles. In this PIH review series, we focus on new knowledge and strategies to improve immunotherapies for cancer patients.

The levels of serum soluble CD86 are correlated with the expression of CD86 variant 3 gene and are prognostic indicators in patients with myeloma.

We previously showed that cell-surface CD86 expressed on multiple myeloma (MM) cells contributed to not only tumor growth but also antitumor cytotoxic T-lymphocyte responses mediated by induction of IL-10-producing CD4+ T cells. The soluble form of CD86 (sCD86) was also detected in serum from patients with MM. Thus, to determine whether sCD86 levels are a useful prognostic factor, we investigated the association of serum sCD86 levels with disease progression and prognosis in 103 newly diagnosed patients with MM. Serum sCD86 was detected in 71% of the patients with MM but was only rarely detected in patients with monoclonal gammopathy of undetermined significance and healthy controls, and the level was significantly increased in patients with advanced-stage MM. When we examined differences in clinical characteristics according to the level of serum sCD86, those in the high (≥2.18 ng/mL, n = 38) group exhibited more aggressive clinical characteristics, with shorter overall survival times compared with those in the low (<2.18 ng/mL, n = 65) group. On the other hand, it was difficult to stratify the patients with MM into different risk groups based on the expression levels of cell-surface CD86. The levels of serum sCD86 were significantly correlated with the expression levels of the messenger RNA (mRNA) transcripts of CD86 variant 3, which lack exon 6, resulting in a truncated transmembrane region, and its variant transcripts were upregulated in the high group. Thus, our findings suggest that sCD86 can be easily measured in peripheral blood samples and is a useful prognostic marker in patients with MM.

CD155 and CD112 as possible therapeutic targets of FLT3 inhibitors for acute myeloid leukemia.

Acute myeloid leukemia (AML) relapse is considered to be related to escape from antitumor immunity. Changes in the expression of immune checkpoints, including B7 homolog (H)1 and B7-H2, have been reported to contribute to AML progression. Binding of T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) among other immune checkpoints on natural killer (NK) and T cells to CD155/CD112 in tumors is supposed to be inhibitory; however, the mechanism by which changes in CD155 and CD112 expression affect tumor immunity remains unclear. When the increased expression of CD155 and CD112 activates Raf-MEK-ERK pathway and Raf-MEK-ERK pathway is one of the targets of FMS-like tyrosine kinase 3 (FLT3) inhibition. The present study investigated the alterations in CD155 and CD112 expression under FLT3 inhibition (quizartinib and gilteritinib) and studied its effect on NK and T cell cytotoxicity. CD155 and CD112 expression was analyzed using flow cytometry and reverse transcription-quantitative PCR in AML cell lines with or without FLT3 mutation using FLT3 inhibitors. CD155 and CD112 expression was specifically downregulated by FLT3 inhibition in FLT3-mutated cell lines. Direct cytotoxicity and antibody-dependent cellular cytotoxicity against these cells by NK cells were enhanced. However, the cytotoxicity of γδ T cells with low TIGIT expression compared with NK cells was not enhanced in direct cytotoxicity assay using luciferase luminescence. The analysis of clinical trials from The Cancer Genome Atlas (TCGA) revealed that high CD155 and CD112 expression is associated with poor overall survival. The enhanced cytotoxicity of NK cells against CD155- and CD112-downregulated cells following FLT3 inhibition indicated CD155 and CD112 as possible targets of immunotherapy for AML using FLT3 inhibitors.

Clinicopathologic Characteristics and A20 Mutation in Primary Thyroid Lymphoma.

BACKGROUND: Primary thyroid lymphoma (PTL) is a rare disease frequently arising against a background of autoimmune thyroiditis. It has recently been reported that the inactivation of the NF-κB negative regulator A20 by deletion and/or mutation could be involved in the pathogenesis of subsets of B-cell lymphomas. This study investigated the clinicopathologic characteristics and A20 mutation in patients with PTL. METHODS: We analyzed the characteristics of 45 PTL patients (14 men and 31 women), with a median age of 71 (range, 35-90) years. A20 mutations were analyzed in DNA extracted from 20 samples consisting of 19 tumor tissue samples and 1 sample from Hashimoto's thyroiditis. RESULTS: Thirty-five patients (82%) had a history of Hashimoto's thyroiditis, and 29 (64%) had diffuse large B-cell lymphoma (DLBCL) and presented with larger tumors including bulky mass, elevated soluble interleukin-2 receptor levels, and a longer history of Hashimoto's thyroiditis than that of patients with mucosa-associated lymphoid tissue (MALT) lymphoma (n=16). A20 mutations were identified in 3 of 19 PTL patients (16%), in 2 of the 10 (20%) with DLBCL and in 1 of the 9 (11%) with MALT lymphoma. Interestingly, all patients with A20 mutations had Hashimoto's thyroiditis. Furthermore, they had a common missense variant in exon 3 (rs2230926 380T>G; F127C), which reduces the ability of A20 to inhibit NF-κB signaling. CONCLUSION: Our study suggests that the histological features of PTL affect clinical outcomes and that A20 mutations are related to PTL pathogenesis in some patients with Hashimoto's thyroiditis.

Circulating cell-free DNA in the peripheral blood plasma of patients is an informative biomarker for multiple myeloma relapse.

BACKGROUND: Multiple myeloma (MM) is an incurable hematological malignancy. Despite the introduction of several novel drugs, most patients relapse. Biomarkers to identify the early signs of relapse will make it possible to adjust the therapeutic strategy before the disease worsens. Although understanding genetic changes is important for the treatment of MM, currently known biomarkers of relapse, including serum free-light chains and monoclonal paraproteins, are not associated with genetic changes. METHODS: We therefore performed a multicenter study to examine the usefulness of circulating cell-free DNA (cfDNA) present in the peripheral blood (PB) plasma of patients as a biomarker for MM relapse. RESULTS: We identified several driver mutations by combined analysis of next-generation sequencing and existing databases of candidate oncogenes. Furthermore, relapse was detected more sensitively by monitoring the circulating cfDNA with these driver mutations than by conventional serum free-light chain examination. CONCLUSION: These results suggest the potential utility of cfDNA in the PB plasma of patients as a relevant early biomarker for MM relapse.

Durvalumab Combined with Immunomodulatory Drugs (IMiD) Overcomes Suppression of Antitumor Responses due to IMiD-induced PD-L1 Upregulation on Myeloma Cells.

We previously showed that the interaction of programmed death-ligand 1 (PD-L1) on multiple myeloma (MM) cells with PD-1 not only inhibits tumor-specific cytotoxic T-lymphocyte activity via the PD-1 signaling pathway but also induces drug resistance via PD-L1-mediated reverse signals. We here examined the regulation of PD-L1 expression by immunomodulatory drugs (IMiDs) and antimyeloma effects of the anti-PD-L1 antibody durvalumab in combination with IMiDs. IMiDs induced PD-L1 expression on IMiD-insensitive MM cells and plasma cells from patients newly diagnosed with MM. Gene-expression profiling analysis demonstrated that not only PD-L1, but also a proliferation-inducing ligand (APRIL), was enhanced by IMiDs. PD-L1 induction by IMiDs was suppressed by using the APRIL inhibitor recombinant B-cell maturation antigen (BCMA)-Ig, the antibody against BCMA, or an MEK/ERK inhibitor in in vitro and in vivo assays. In addition, its induction was abrogated in cereblon (CRBN)-knockdown MM cells, whereas PD-L1 expression was increased and strongly induced by IMiDs in Ikaros-knockdown cells. These results demonstrated that PD-L1 upregulation by IMiDs on IMiD-insensitive MM cells was induced by (i) the BCMA-APRIL pathway via IMiD-mediated induction of APRIL and (ii) Ikaros degradation mediated by CRBN, which plays a role in inhibiting PD-L1 expression. Furthermore, T-cell inhibition induced by PD-L1-upregulated cells was effectively recovered after combination treatment with durvalumab and IMiDs. PD-L1 upregulation by IMiDs on MM cells might promote aggressive myeloma behaviors and immune escape in the bone marrow microenvironment.

Immune Functions of Signaling Lymphocytic Activation Molecule Family Molecules in Multiple Myeloma.

The signaling lymphocytic activation molecule (SLAM) family receptors are expressed on various immune cells and malignant plasma cells in multiple myeloma (MM) patients. In immune cells, most SLAM family molecules bind to themselves to transmit co-stimulatory signals through the recruiting adaptor proteins SLAM-associated protein (SAP) or Ewing's sarcoma-associated transcript 2 (EAT-2), which target immunoreceptor tyrosine-based switch motifs in the cytoplasmic regions of the receptors. Notably, SLAMF2, SLAMF3, SLAMF6, and SLAMF7 are strongly and constitutively expressed on MM cells that do not express the adaptor proteins SAP and EAT-2. This review summarizes recent studies on the expression and biological functions of SLAM family receptors during the malignant progression of MM and the resulting preclinical and clinical research involving four SLAM family receptors. A better understanding of the relationship between SLAM family receptors and MM disease progression may lead to the development of novel immunotherapies for relapse prevention.

[SLAM family proteins as therapeutic targets in multiple myeloma].

Reports have described the excellent efficacies of new immunotherapeutic strategies, such as monoclonal antibody (mAb) therapies, in multiple myeloma (MM) patients. Signaling lymphocytic activation molecule family (SLAMF) molecules are expressed strongly on normal lymphocytes and plasma cells from MM patients. The anti-SLAMF7 mAb elotuzumab (ELO) has been approved for the treatment of relapsed/refractory MM (RRMM). In MM patients, a high serum soluble SLAMF7 (sSLAMF7) concentration is associated with aggressive clinical characteristics. This suggests a proliferative function of the SLAMF7-sSLAMF7 interaction that could be inhibited by ELO. SLAMF3 is also expressed strongly and constitutively on myeloma cells. We observed the aggressive characteristics of SLAMF3+ MM in vitro and in vivo. SLAMF3 interacts directly with the adaptor proteins SHP2 and GRB2. A gene expression analysis revealed that SLAMF3 transmits positive signals to MM cells via the MAPK/ERK signaling pathway and that sSLAMF3 levels are increased markedly in advanced MM. Thus, SLAMF3 may be a novel immunotherapeutic target in MM. SLAMF2 and SLAMF6 are also expressed strongly on MM cells, and the safety of antibody-drug conjugates that target these molecules in patients with RRMM is currently under study. Our and others' reports demonstrate the value of SLAMF molecules as promising new targets for antimyeloma immunotherapies.

The SLAMF3 rs509749 polymorphism correlates with malignant potential in multiple myeloma.

The signaling lymphocytic activation molecule family 3 (SLAMF3) is highly expressed on plasma cells from patients with multiple myeloma (MM) and induces high malignant potential by ERK signaling mediated via the interaction with adaptor proteins SHP2 and GRB2. This study focused on the single-nucleotide polymorphism (SNP) of the SLAMF3 gene (rs509749, 1804A>G, M602V) in MM. The SNP G allele was a major type, and the frequencies of the GG, GA, and AA genotypes were 61.8%, 29.4%, and 8.8%, respectively, in patients with MM, which was almost the same as in healthy the control group in the Japanese population. Interestingly, patients with GG genotypes had significantly shorter overall survival times than patients with GA/AA genotypes. Consistent with those results, SLAMF3-overexpressing KMS-34 cells with the G allele (V602) had higher cell proliferation potential and were more resistant to anti-MM agents than those with the A allele (M602). When those cells were subcutaneously inoculated into NOG mice, tumor sizes in mice receiving V602 cells rapidly increased, and survival was significantly shorter than in mice injected with M602 cells. Furthermore, SLAMF3 V602 molecules bound more tightly to SHP2 and GRB2, with increased SHP2 and ERK phosphorylation compared with M602 cells. The mRNA expression of cell cycle-related genes (CCND1 and CCNE1) and anti-apoptotic genes (BCL2L and p21) was increased in V602 cells compared with M602 cells. The results thus suggested that the G allele of SLAMF3 SNP rs509749 may be associated with MM disease progression.

PD-L1-PD-1 Pathway in the Pathophysiology of Multiple Myeloma.

PD-L1 expressed on tumor cells contributes to disease progression with evasion from tumor immunity. Plasma cells from multiple myeloma (MM) patients expressed higher levels of PD-L1 compared with healthy volunteers and monoclonal gammopathy of undetermined significance (MGUS) patients, and its expression is significantly upregulated in relapsed/refractory patients. Furthermore, high PD-L1 expression is induced by the myeloma microenvironment and PD-L1+ patients with MGUS and asymptomatic MM tend to show disease progression. PD-L1 expression on myeloma cells was associated with more proliferative potential and resistance to antimyeloma agents because of activation of the Akt pathway through PD-1-bound PD-L1 in MM cells. Those data suggest that PD-L1 plays a crucial role in the disease progression of MM.

SLAMF3-Mediated Signaling via ERK Pathway Activation Promotes Aggressive Phenotypic Behaviors in Multiple Myeloma.

The signaling lymphocytic activation molecule family 3 (SLAMF3) is a member of the immunoglobulin superfamily expressed on T, B, and natural killer cells and modulates the activation and cytotoxicity of these cells. SLAMF3 is also expressed on plasma cells from patients with multiple myeloma (MM), although its role in MM pathogenesis remains unclear. This study found that SLAMF3 is highly and constitutively expressed on MM cells regardless of disease stage and that SLAMF3 knockdown/knockout suppresses proliferative potential and increases drug-induced apoptosis with decreased levels of phosphorylated ERK protein in MM cells. SLAMF3-overexpressing MM cells promote aggressive myeloma behavior in comparison with cytoplasmic domain-truncated SLAMF3 (ΔSLAMF3) cells. SLAMF3 interacts directly with adaptor proteins SH2 domain-containing phosphatase 2 (SHP2) and growth factor receptor bound 2 (GRB2), which also interact with each other. SLAMF3 knockdown, knockout, ΔSLAMF3, and SHP2 inhibitor-treated MM cells decreased phosphorylated ERK protein levels. Finally, serum soluble SLAMF3 (sSLAMF3) levels were markedly increased in advanced MM. Patients with high levels of sSLAMF3 progressed to the advanced stage significantly more often and had shorter progression-free survival times than those with low levels. This study revealed that SLAMF3 molecules consistently expressed on MM cells transmit MAPK/ERK signals mediated via the complex of SHP2 and GRB2 by self-ligand interaction between MM cells and induce a high malignant potential in MM. Furthermore, high levels of serum sSLAMF3 may reflect MM disease progression and be a useful prognostic factor. IMPLICATIONS: SLAMF3 may be a new therapeutic target for immunotherapy and novel agents such as small-molecule inhibitors.

A combination of check-point blockade and α-galactosylceramide elicits long-lasting suppressive effects on murine hepatoma cell growth in vivo.

Immunotherapy for cancer cells induced by interfering with PD-1/PD-L1 engagement via check-point blockades was initiated by tumour-specific PD-1+ CD8+ cytotoxic T lymphocytes (CTLs) within a tumour mass and eliminate the tumour. Here, we used C57BL/6 (B6) mice implanted with the syngeneic hepatoma cell line Hepa1-6-1, and confirmed that the dendritic cells (DCs) within Hepa1-6-1 tumour mass were tolerogenic with downmodulated co-stimulatory molecules by tumour-derived factors. Although Hepa1-6-1 cells did not prime tumour-specific CTLs within the tumour, specific CTLs primed in the regional lymph nodes seemed to be invaded into the tumour mass. The specific CTLs gained PD-1+ expression when associated with PD-L1+ Hepa1-6-1 cells within the tumour mass. Their cytotoxic activity in vivo was revitalised after intraperitoneal (i.p.) administration of the anti-PD-1 monoclonal antibody (mAb), indicating that PD-1/PD-L1 engagement within the tumour was abrogated by check-point blockade. Nonetheless, the tolerogenic DCs within the Hepa1-6-1 tumour mass remained tolerogenic even after three shots of PD-1-blockade administration, and the suppressed Hepa1-6-1 growth was revisited. In this study, we show here an excellent therapeutic effect consisting of three injections of anti-PD1 mAb and the sequential administration of the CD1d molecule-restricted ligand α-galactosylceramide (α-GalCer), an immuno-potent lipid/glycolipid, which converts tolerogenic DCs into immunogenic DCs with upregulated expression of co-stimulatory molecules. The α-GalCer-activated DCs secreted a large amount of IL-12, which can activate tumour-specific CTLs in vivo. The check-point blockade was not sufficiently effective, but the dose needed for tumour eradication was reduced by 90% when tumour-bearing mice were also administered i.p. α-GalCer.

Immunotherapy for Multiple Myeloma.

Despite therapeutic advances over the past decades, multiple myeloma (MM) remains a largely incurable disease with poor prognosis in high-risk patients, and thus new treatment strategies are needed to achieve treatment breakthroughs. MM represents various forms of impaired immune surveillance characterized by not only disrupted antibody production but also immune dysfunction of T, natural killer cells, and dendritic cells, although immunotherapeutic interventions such as allogeneic stem-cell transplantation and dendritic cell-based tumor vaccines were reported to prolong survival in limited populations of MM patients. Recently, epoch-making immunotherapies, i.e., immunomodulatory drug-intensified monoclonal antibodies, such as daratumumab combined with lenalidomide and chimeric antigen receptor T-cell therapy targeting B-cell maturation antigen, have been developed, and was shown to improve prognosis even in advanced-stage MM patients. Clinical trials using other antibody-based treatments, such as antibody drug-conjugate and bispecific antigen-directed CD3 T-cell engager targeting, are ongoing. The manipulation of anergic T-cells by checkpoint inhibitors, including an anti-T-cell immunoglobulin and ITIM domains (TIGIT) antibody, also has the potential to prolong survival times. Those new treatments or their combination will improve prognosis and possibly point toward a cure for MM.

Flow Cytometry-Based Photodynamic Diagnosis with 5-Aminolevulinic Acid for the Detection of Minimal Residual Disease in Multiple Myeloma.

Multiple myeloma is the cancer of plasma cells. Along with the development of new and effective therapies, improved outcomes in patients with multiple myeloma have increased the interest in minimal residual disease (MRD) monitoring. However, the considerable heterogeneity of immunophenotypic and molecular markers of myeloma cells has limited its clinical application. 5-Aminolevulinic acid (ALA) is a natural compound in the heme biosynthesis pathway. Following ALA treatment, tumor cells preferentially accumulate porphyrins because of the differential activities of aerobic glycolysis, known as Warburg effect. Among various porphyrins, protoporphyrine IX is a strong photosensitizer; thus, ALA-based photodynamic diagnosis has been widely used in various solid cancers. Here, the feasibility of flow cytometry-based photodynamic detection of MRD was tested in multiple myeloma. Among various human cell lines of hematological malignancies, including K562 erythroleukemia, Jurkat T-cell leukemia, Nalm6 pre-B cell leukemia, KG1a myeloid leukemia, and U937 monocytic leukemia, human myeloma cell line, KMS18, and OPM2 abundantly expressed ALA transporters, such as SLC36A1 and SLC15A2, and 1 mM ALA treatment for 24 h resulted in nearly 100% porphyrin fluorescence expression, which could be competitively inhibited by ALA transport with gamma-aminobutyric acid. Titration studies revealed that the lowest ALA concentration required to achieve nearly 100% porphyrin fluorescence in KMS18 cells was 0.25 mM, with an incubation period of 2 h. Under these conditions, incubation of primary peripheral blood mononuclear cells resulted in only 1.8 % of the cells exhibiting porphyrin fluorescence. Therefore, flow cytometry-based photodynamic diagnosis is a promising approach for detecting MRD in multiple myeloma.

[Amebic liver abscesses developing during R-CHOP chemotherapy in a patient with mantle cell lymphoma].

A 51-year-old man was diagnosed with stage IV mantle cell lymphoma based on terminal ileum biopsy and treated with the R-CHOP regimen. Abdominal CT to assess continuous fever after three courses of R-CHOP revealed three low-density areas in the liver. PCR of the fluid obtained by percutaneous drainage revealed Entamoeba histolytica positivity, although the cultures were negative. Metronidazole treatment achieved cure. The patient was not a homosexual but had an 8-month stay in Lesotho 21 years ago, leading to the possibility that E. histolytica infection at the time continued as an asymptomatic colonization until the initiation of corticosteroid-containing chemotherapy.