[Efficacy and safety of VRD regimen of autologous hematopoietic stem cell transplantation in patients with newly diagnosed multiple myeloma]

Objective: To explore the stem cell collection rate and efficacy and safety of patients aged 70 and below with newly diagnosed multiple myeloma (MM) treated with the VRD (bortezomib, lenalidomide and dexamethasone) regimen followed by autologous stem cell transplantation (ASCT). Methods: Retrospective case series study. The clinical data of 123 patients with newly diagnosed MM from August 1, 2018, to June 30, 2020, at the First Affiliated Hospital of Soochow University and Suzhou Hopes Hematology Hospital, who were eligible for VRD regimen sequential ASCT, were collected. The clinical characteristics, efficacy after induction therapy, mobilization regimen of autologous stem cells, autologous stem cell collection rate, and side effects and efficacy of ASCT were retrospectively analyzed. Results: Of the 123 patients, 67 were males. The median patient age was 56 (range: 31-70) years. Patients with IgG, IgA, IgD, and light-chain types accounted for 47.2% (58/123), 23.6% (29/123), 3.2% (4/123), and 26.0% (32/123) of patients, respectively. In addition, 25.2% (31/123) of patients had renal insufficiency (creatinine clearance rate<40 ml/min). Patients with Revised-International Staging System (R-ISS) Ⅲ accounted for 18.2% (22/121) of patients. After induction therapy, the rates of partial response and above, very-good partial response (VGPR) and above, and complete response (CR)+stringent CR were 82.1% (101/123), 75.6% (93/123), and 45.5% (56/123), respectively. Overall, 90.3% (84/93) of patients were mobilized with cyclophosphamide+granulocyte colony-stimulating factor (G-CSF) and 8 patients with G-CSF or G-CSF+plerixafor due to creatinine clearance rate<30 ml/min and one of them was mobilized with DECP (cisplatin, etoposide, cyclophosphamide and dexamethasone)+G-CSF for progressive disease. The rate of autologous stem cell collection (CD34⁺cells≥2×10⁶/kg) after four courses of VRD regimen was 89.1% (82/92), and the rate of collection (CD34⁺cells≥5×10⁶/kg) was 56.5% (52/92). Seventy-seven patients treated with the VRD regimen sequential ASCT. All patients had grade 4 neutropenia and thrombocytopenia. Among the nonhematologic adverse events during ASCT, the highest incidence was observed for gastrointestinal reactions (76.6%, 59/77), followed by oral mucositis (46.8%, 36/77), elevated aminotransferases (44.2%, 34/77), fever (37.7%, 29/77), infection (16.9%, 13/77) and heart-related adverse events (11.7%, 9/77). Among the adverse events, grade 3 adverse events included nausea (6.5%, 5/77), oral mucositis (5.2%, 4/77), vomiting (3.9%, 3/77), infection (2.6%, 2/77), elevated blood pressure after infusion (2.6%, 2/77), elevated alanine transaminase (1.3%, 1/77), and perianal mucositis (1.3%, 1/77); there were no grade 4 or above nonhematologic adverse events. The proportion of patients who achieved VGPR and above after VRD sequential ASCT was 100% (75/75), and the proportion of patients who were minimal residual disease-negative (<10^-4 level) was 82.7% (62/75). Conclusion: In patients aged 70 and below with newly diagnosed MM treated with VRD induction therapy, the collection rate of autologous stem cells was good, and good efficacy and tolerability were noted after follow-up ASCT.

[The expression level of secretory mature B cell surface antigen in primary diagnosed multiple myeloma and its clinical significance]

Objective: To explorer Secretory mature B cell surface antigen (sBCMA) expression level, changes during treatment and clinical significance in newly diagnosed MM patients. Methods: Clinical data of 158 MM patients admitted to the Department of Hematology, the First Affiliated Hospital of Soochow University from August 2018 to September 2020 were analyzed retrospectively. The concentration of sBCMA in the patients was determined by BCMA ELISA and compared with the normal range. The results were compared with clinical efficacy, age, type, R-ISS stage, renal impairment, and humoral immune function. Results: The median age of the patients was 57 (31-73 years old), 86 (54.5%) males and 72 (45.5%) females, mainly IgG type, 81 patients(51.2%). SBCMA value M(Q₁,Q₃) was 76.50 (55.50, 94.40) μg/L, 100% higher than the upper limit of normal value. According to the efficacy evaluation, the patients were divided into complete remission(CR) group, very good partial remission(VGPR) group, partial remission(PR) group and ineffiecacy group, the results showed the level of sBCMA in CR group[80.10 (58.05, 96.90) vs 15.70 (9.85, 28.65) μg/L] and VGPR group[74.60 (52.20, 93.00) vs 17.20 (13.30, 38.80) μg/L]was significantly higher than that before treatment(all P<0.001), and there was no significant difference in PR group and ineffective group before and after treatment (all P>0.05).The amount of serum intact protein M protein was positively correlated with the level of sBCMA expression in newly diagnosed patients (r=0.22, P=0.040), and there was no correlation between the proportion of bone marrow plasma cells and sBCMA expression (r=0.07, P=0.449).The correlation between sBCMA levels at initial diagnosis and MM type[IgG type, IgA type vs light chain type:(78.6±3.5), (72.4±5.4) vs (83.8±6.9)μg/L], age[≥65 vs<65 years: (73.6±5.5)vs (79.3±3.1)μg/L], R-ISS stage[stage Ⅰ, Ⅱ vs Ⅲ:(80.2±3.1) vs (69.4±6.1)μg/L], renal impairment [Creatinine clearance rate (Ccr) ≤30 vs>30 ml/min:(81.6±4.8) vs (76.5±3.4)μg/L], and high-risk karyotype[high-risk vs standard-risk:(73.6±5.7) vs (80.2±3.2)μg/L] were not associated (all P>0.05). Expression levels of sBCMA were negatively correlated with IgM levels in MM patients (r=-0.39, P=0.002) and after treatment (r=-0.25, P=0.015). Conclusions: The expression of sBCMA in MM patients is a reliable indicator of the clinical efficacy of MM and is related to the occurrence of MM immune deficiency and recovery after treatment. sBCMA can be used as a new independent marker for monitoring and predicting the efficacy of MM patients.

[Clinical implication of minimal residual disease monitoring by 10-color flow cytometry in multiple myeloma]

目的

采用十色流式细胞术监测多发性骨髓瘤（MM）患者治疗后骨髓微小残留病（MRD），探讨其对MM患者预后的预测价值。

方法

回顾性分析2015年7月至2017年7月苏州大学附属第一医院收治的150例MM患者的临床资料，十色流式细胞术检测MRD水平。

结果

①诱导治疗结束后采用十色流式细胞术监测MRD的87例MM患者中，MRD阴性者34例（39.1%）。自体造血干细胞移植后1年内行十色流式细胞术监测MRD的69例患者中，MRD阴性者34例（49.3%），诱导治疗结束和移植后MRD阴性患者的无进展生存（PFS）期优于MRD阳性患者（未达到对21个月，P=0.022；未达到对18个月，P<0.001）。②根据移植前后MRD的动态改变将MM患者分为MRD持续阴性、阳性转阴性、持续阳性、阴性转阳性四组，四组的2年PFS率分别为83%、82%、44%、0（P=0.002）。③多因素分析显示诱导治疗结束后的MRD水平是影响PFS的独立预后因素[P=0.002，HR=4.808（95%CI 1.818~12.718）]。

结论

治疗后MRD转阴提示更好的临床预后，MRD水平对于MM患者的预后价值优于血清学疗效评估，可以联合R-ISS分期及细胞遗传学异常评估患者预后。

Synthesis of peptides and proteins without cysteine residues by native chemical ligation combined with desulfurization

The highly chemoselective reaction between unprotected peptides bearing an N-terminal Cys residue and a C-terminal thioester enables the total and semi-synthesis of complex polypeptides. Here we extend the utility of this native chemical ligation approach to non-cysteine containing peptides. Since alanine is a common amino acid in proteins, ligation at this residue would be of great utility. To achieve this goal, a specific alanine residue in the parent protein is replaced with cysteine to facilitate synthesis by native chemical ligation. Following ligation, selective desulfurization of the resulting unprotected polypeptide product with H(2)/metal reagents converts the cysteine residue to alanine. This approach, which provides a general method to prepare alanyl proteins from their cysteinyl forms, can be used to chemically synthesize a variety of polypeptides, as demonstrated by the total chemical syntheses of the cyclic antibiotic microcin J25, the 56-amino acid streptococcal protein G B1 domain, and a variant of the 110-amino acid ribonuclease, barnase.

Genes of the sbo-alb locus of Bacillus subtilis are required for production of the antilisterial bacteriocin subtilosin

Bacillus subtilis JH642 and a wild strain of B. subtilis called 22a both produce an antilisterial peptide that can be purified by anion-exchange and gel filtration chromatography. Amino acid analysis confirmed that the substance was the cyclic bacteriocin subtilosin. A mutant defective in production of the substance was isolated from a plasmid gene disruption library. The plasmid insertion conferring the antilisterial-peptide-negative phenotype was located in a seven-gene operon (alb, for antilisterial bacteriocin) residing immediately downstream from the sbo gene, which encodes the precursor of subtilosin. An insertion mutation in the sbo gene also conferred loss of antilisterial activity. Comparison of the presubtilosin and mature subtilosin sequences suggested that certain residues undergo unusual posttranslational modifications unlike those occurring during the synthesis of class I (lantibiotic) or some class II bacteriocins. The putative products of the genes of the operon identified show similarities to peptidases and transport proteins that may function in processing and export. Two alb gene products resemble proteins that function in pyrroloquinoline quinone biosynthesis. The use of lacZ-alb and lacZ-sbo gene fusions, along with primer extension analysis, revealed that the sbo-alb genes are transcribed from a major promoter, residing upstream of sbo, that is very likely utilized by the sigma(A) form of RNA polymerase. The sbo and alb genes are negatively regulated by the global transition state regulator AbrB and are also under positive autoregulation that is not mediated by the subtilosin peptide but instead requires one or more of the alb gene products.

Solution structure of carnobacteriocin B2 and implications for structure-activity relationships among type IIa bacteriocins from lactic acid bacteria

Carnobacteriocin B2 (CbnB2), a type IIa bacteriocin, is a 48 residue antimicrobial peptide from the lactic acid bacterium Carnobacterium pisicola LV17B. Type IIa bacteriocins have a conserved YGNGVXC sequence near the N-terminus and usually contain a disulfide bridge. CbnB2 seemed to be unique in that its two cysteines (Cys9 and Cys14) could be isolated as free thiols [Quadri et al. (1994) J. Biol. Chem. 26, 12204-12211]. To establish the structural consequences of the presence or absence of a disulfide bridge and to investigate if the YGNGVXC sequence is a receptor-binding motif [Fleury et al. (1996) J. Biol. Chem. 271, 14421-14429], the three-dimensional solution structure of CbnB2 was determined by two-dimensional (1)H nuclear magnetic resonance (NMR) techniques. Mass spectroscopic and thiol modification experiments on CbnB2 and on model peptides, in conjunction with activity measurements, were used to verify the redox status of CbnB2. The results show that CbnB2 readily forms a disulfide bond and that this peptide has full antimicrobial activity. NMR results indicate that CbnB2 in trifluoroethanol (TFE) has a well-defined central helical structure (residues 18-39) but a disordered N terminus. Comparison of the CbnB2 structure with the refined solution structure of leucocin A (LeuA), another type IIa bacteriocin, indicates that the central helical structure is conserved between the two peptides despite differences in sequence but that the N-terminal structure (a proposed receptor binding site) is not. This is unexpected because LeuA and CbnB2 exhibit >66% sequence identity in the first 24 residues. This suggests that the N-terminus, which had been proposed [Fleury et al. (1996) J. Biol. Chem. 271, 14421-14429] to be a receptor binding site of type IIa bacteriocins, may not be directly involved and that recognition of the amphiphilic helical portion is the critical feature.

Effect of amino acid substitutions on the activity of carnobacteriocin B2. Overproduction of the antimicrobial peptide, its engineered variants, and its precursor in Escherichia coli

Carnobacteriocin B2, a 48-amino acid antimicrobial peptide containing a YGNGV motif that is produced by the lactic acid bacterium Carnobacterium piscicola LV17B, was overexpressed as fusion with maltose-binding protein in Escherichia coli. This fusion protein was cleaved with Factor Xa to allow isolation of the mature bacteriocin that was identical in all respects to that obtained from C. piscicola. Similar methodology permitted production of the precursor precarnobacteriocin B2 (CbnB2P), which has an 18-amino acid leader, as well as six mutants of the mature peptide: CbnF3 (Tyr3 --> Phe), CbnS33 (Phe33 --> Ser), CbnI34 (Val34 --> Ile), CbnI37 (Val37 --> Ile), CbnG46 (Arg46 --> Gly), and Cbn28 (truncated frameshift mutation: (carnobacteriocin B2 1-28) + ELTHL). Examination of these compounds for antimicrobial activity showed that although CbnI34, CbnI37, and CbnG46 were fully active, CbnB2P, CbnF3, CbnS33, Cbn28, and all of the fusion proteins had greatly reduced or no antimicrobial activity. Expression of the immunity protein that protects against the action of the parent carnobacteriocin B2 in a previously sensitive organism also protects against the active mutants. Because carnobacteriocin B2 also acts as an inducer of bacteriocin production in C. piscicola, the ability of the precursor CbnB2P and the mutants to exert this effect was examined. All were able to induce Bac- cultures and reestablish the Bac+ phenotype except for the truncated Cbn28. The results demonstrate that very minor changes in the peptide sequence may drastically alter antimicrobial activity but that the induction of bacteriocin production is much more tolerant of structural modification, especially at the N terminus.