Efficacy and safety of FLT3 inhibitors in monotherapy of hematological and solid malignancies: a systemic analysis of clinical trials.

Introduction: FLT3 mutations are closely associated with the occurrence of hematological and solid malignancies, especially with acute myeloid leukemia. Currently, several FLT3 inhibitors are in clinical trials, and some have been applied in clinic. However, the safety, efficacy and pharmacodynamics of these FLT3 inhibitors have not been systemically analyzed before. Methods: We searched and reviewed clinical trial reports on the monotherapy of 13 FLT3 inhibitors, including sorafenib, lestaurtinib, midostaurin, gilteritinib, quizartinib, sunitinib, crenolanib, tandutinib, cabozantinib, pexidartinib, pacritinib, famitinib, and TAK-659 in patients with hematological and solid malignancies before May 31, 2023. Results: Our results showed the most common adverse events (AEs) were gastrointestinal adverse reactions, including diarrhea, hand-foot syndrome and nausea, while the most common hematological AEs were febrile neutropenia, anemia, and thrombocytopenia. Based on the published data, the mean overall survival (OS) and the mean progression-free survival (PFS) were 9.639 and 5.905 months, respectively. The incidence of overall response rate (ORR), complete remission (CR), partial response (PR), and stable disease (SD) for all these FLT3 inhibitors was 29.0%, 8.7%, 16.0%, and 42.3%, respectively. The ORRs of FLT3 inhibitors in hematologic malignancies and solid tumors were 40.8% and 18.8%, respectively, indicating FLT3 inhibitors were more effective for hematologic malignancies than for solid tumors. In addition, time to maximum plasma concentration (Tmax) in these FLT3 inhibitors ranged from 0.7-12.0 hours, but the elimination half-life (T1/2) range was highly variable, from 6.8 to 151.8 h. Discussion: FLT3 inhibitors monotherapy has shown significant anti-tumor effect in clinic, and the effectiveness may be further improved through combination medication.

TRAF3 interacts with Smac/DIABLO and enhances the proapoptotic effect of Smac/DIABLO in cytoplasm.

Smac/DIABLO (second mitochondria-derived activator of caspase/direct IAP-binding protein with low PI) is a 29 kDa mitochondrial precursor protein, which is proteolytically processed in mitochondria into a 23 kDa mature protein. It is released from the mitochondrial intermembrane space to cytosol after an apoptotic trigger. Smac/DIABLO acts as a dimer and it contributes to caspase activation by sequestering the inhibitor of apoptosis proteins (IAPs). In order to further investigate the mechanism of Smac/DIABLO action, we used the mature form of Smac/DIABLO as a bait and screened proteins that interact with mature Smac/DIABLO in human liver cDNA library using the yeast two-hybrid system. Forty-two colonies were obtained after 5.8x10(6) colonies were screened by nutrition limitation and X-galactosidase assay. After DNA sequence analysis and homology retrieval, one of the candidate proteins was identified as TRAF domain of the TNF receptor associated factor 3 (TRAF3). The interaction site between TRAF3 and Smac/DIABLO was identified by beta-galactosidase test. The interaction between TRAF3 and Smac/DIABLO via TRAF domain was identified in vivo by co-immunoprecipitation in HepG2 cells, and the direct interaction between TRAF3 and Smac/DIABLO in vitro was identified by GST-pull down assay. Co-expression of TRAF3 and mature Smac/DIABLO in 293 cells could enhance the Smac/DIABLO-mediated apoptosis. These results suggested that TRAF3 interacted with Smac/DIABLO via TRAF domain, leading to an increased proapoptotic effect of Smac/DIABLO in cytoplasm.

An analysis on transcriptional regulation activity of human XBP1 gene 5' upstream DNA sequences.

OBJECTIVE: To analyze the transcription activation and possible regulation mechanism of human X-box binding protein 1(XBP1)gene 5'upstream DNA sequence in different cell lines. METHODS: Six kinds of XBP1 promoter deletion mutants were cloned into pGEM-Teasy vector, which included XBP1 gene 5' upstream -1039 to 66 bp,-859 to 66 bp,-623 to 66 bp,-351 to 66 bp,-227 to 66 bp,-227 to -45 bp respectively. Every deletion mutant sequence was cut from Teasy-XBP1p by KpnI and Xho I, and subcloned into pCAT3-Basic to produce a set of constructs termed as p1-XBP1p, p2-XBP1p, p3-XBP1p, p4-XBP1p, p5-XBP1p, p6-XBP1p, respectively. The transcription activity of each construct was detected after transiently transfecting K562, HepG2,NIH-3T3 and L0(2)cell with FuGENE 6 transfection reagent. Cells transfected by pCAT3-Basic or pCAT3-Promoter were used as negative and positive controls. The activity of chloramphenicol acetyltransferase(CAT), which reflects the transcription activation of the XBP1 gene promoter, was detected by ELISA after 48 hours of transfection. RESULTS: The reporter vectors of six kinds of XBP1 promoter deletion mutants were successfully constructed, as confirmed by restriction enzyme digestion and sequencing. The activities of p4-XBP1p and p5-XBP1p were higher than the other deletion mutants in K562 and HepG2. And the activity of p5-XBP1p was the highest in HepG2. There was no activity detected from any transfected NIH-3T3. CONCLUSION: The XBP1 gene promoter can transactivate its downstream gene to transcription. The core sequence of XBP1 promoter was implied between -227 bp and 66 bp. This sequence was connected with the transcriptional activity of XBP1 promoter closely. Its transcription activity varies with different cell lines. XBP1 promoter might drive gene expression with cell-type specificity.