The STAT3 inhibitor stattic overcome bortezomib-resistance in multiple myeloma via decreasing PSMB6.

Bortezomib, an FDA approved drug in 2003 for newly diagnosed and relapsed/refractory MM, had showed great efficacy in different clinical settings. However, many patients still developed resistance to Bortezomib, and the mechanism of action remains unelucidated. Here, we showed that Bortezomib resistance can be partially overcome by targeting a different subunit of 20 S complex - PSMB6. PSMB6 knock down by shRNA increased sensitivity to Bortezomib in resistant and sensitive cell line. Interestingly, a STAT3 inhibitor, Stattic, is shown to selectively inhibit PSMB6 and induce apoptosis in Bortezomib resistant and sensitive MM cells, even with IL-6 induction. Therefore, PSMB6 is a novel target for Bortezomib resistance and Stattic may offer a potential therapeutic strategy.

Halting Multiple Myeloma with MALT1 Inhibition: Suppressing BCMA-Induced NF-κB and Inducing Immunogenic Cell Death.

As multiple myeloma (MM) poses a formidable therapeutic challenge despite recent progress, exploring novel targets is crucial. Mucosa-associated lymphoid tissue lymphoma translocation protein-1 (MALT1) emerges as a promising paracaspase with druggable potential, especially unexplored in MM. Our study provided compelling evidence demonstrating a statistically significant elevation of MALT1 expression in human primary MM cells. Moreover, elevated MALT1 expression was associated with a poorer prognosis in MM. Genetic deletion of MALT1 reduced cell growth, colony formation, and tumor growth in vivo. Pharmacological inhibition with 1 µM Mi-2 effectively inhibited cell growth, inducing mitochondria-dependent apoptotic cell death. Mechanistically, MALT1 inhibition disrupted diverse signal transduction pathways, notably impeding nuclear factor κB (NF-κB). Significantly, the inhibition of MALT1 demonstrated a substantial suppression of NF-κB activation by elevating IκB, disrupting the nuclear localization of p65 and c-Rel. This effect was observed in both the basal state and when stimulated by BCMA, highlighting the pivotal role of MALT1 inhibition in influencing MM cell survival. It was noteworthy that Mi-2 induces properties associated with immunogenic cell death (ICD), as evidenced by increased calreticulin (CRT), ATP release, and high-mobility group protein B1 (HMGB1) upregulation, consequently triggering ICD-associated immune activation and enhancing CD8+ T - cell cytotoxicity in vitro. In conclusion, our research highlights MALT1 as a promising druggable target for therapeutic interventions in MM, providing insights into its molecular mechanisms in MM progression.

[The Inhibiting Effect of Autophagy Inhibitor ROC-325 on Multiple Myeloma].

OBJECTIVE: To investigate the effects of autophagy inhibitor ROC-325 and its combination with bortezomib on the proliferation, apoptosis and autophagy of multiple myeloma cell lines. METHODS: Multiple myeloma cells were treated with ROC-325 at different concentration. The cell proliferation was detected by CCK-8. Apoptosis was determined by Caspase-3/7 and Caspase-9 activity assays. Autophagy was detected by monodansylcadaverine staining. The apoptosis-related proteins (PARP and Caspase-3) and autophagy-related proteins (P62, Beclin-1, and LC3A/B) were analyzed by Western blot. The combined effect with bortezomib on bortezomib-resistant cell line was detected by CCK-8. RESULTS: ROC-325 inhibited the proliferation of RPMI 8226, RPMI 8226-BTZ100, U266 and IM9 cells in a dose-dependent manner (r=-0.8275, r=-0.9079, r=-0.9422, r=-0.9305), the 72 h IC50 values were 2.795, 4.020, 5.432 and 4.755 µmol/L, respectively. The activity assays of Caspase-3/7 and Caspase-9 showed that their relative activity was increased gradually in proportion to the drug concentration with the statistically significant difference (r=0.9648, r=0.9377, r=0.9318; r=0.9087, r=0.9431, r=0.8914). MDC staining results showed that the number of autophagic vacuoles increased with the rise of ROC-325 concentration (r=0.9565, r=0.9373, r=0.9233). ROC-325 could increase the expression of apoptosis-related proteins (PARP and Caspase-3) and autophagy-related proteins (P62 and LC3-Ⅱ/LC3-Ⅰ), but decrease the expression of Beclin-1 detected by Western blot. The CCK-8 assay showed that ROC-325 combined with bortezomib had synergistic effect on the inhibition of drug resistant cell line RPMI 8226-BTZ100. CONCLUSION: ROC-325 can inhibit the proliferation, induce the apoptosis of myeloma cells through the mitochondrial pathway, inhibit the autophagy of myeloma cells by affecting the fusion of autophagosomes and lysosomes, and overcome bortezomib resistance by the combination of ROC-325 with bortezomib.

Simultaneous determination of mangiferin and neomangiferin in rat plasma by UPLC-MS/MS and its application for pharmacokinetic study.

In this study, a sensitive and rapid ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed to determine mangiferin and neomangiferin in rat plasma simultaneously. Chromatographic separation was carried out on an Acquity UPLC BEH C18 column and mass spectrometric analysis was performed using a Xevo TQD triple quadruple mass spectrometer coupled with an electrospray ionization (ESI) source. The MRM transitions of m/z 423.2 → 303.1 and m/z 585.0 → 273.1 were used to quantify for mangiferin and neomangiferin, respectively. The linearity of this method was found to be within the concentration range of 5-2000 ng/mL for mangiferin, and 2-1000 ng/mL for neomangiferin in rat plasma, respectively. Only 3.0 min was needed for an analytical run. This assay was used to support a preclinical study to investigate the pharmacokinetics of mangiferin and neomangiferin in rats.