Interleukin-6-independent expression of glucocorticoid receptor is upregulated by triptolide in multiple myeloma

Exploring the nexus of nuclear receptors in hematological malignancies

Hematological malignancies (HM) represent a subset of neoplasms affecting the blood, bone marrow, and lymphatic systems, categorized primarily into leukemia, lymphoma, and multiple myeloma. Their prognosis varies considerably, with a frequent risk of relapse despite ongoing treatments. While contemporary therapeutic strategies have extended overall patient survival, they do not offer cures for advanced stages and often lead to challenges such as acquisition of drug resistance, recurrence, and severe side effects. The need for innovative therapeutic targets is vital to elevate both survival rates and patients' quality of life. Recent research has pivoted towards nuclear receptors (NRs) due to their role in modulating tumor cell characteristics including uncontrolled proliferation, differentiation, apoptosis evasion, invasion and migration. Existing evidence emphasizes NRs' critical role in HM. The regulation of NR expression through agonists, antagonists, or selective modulators, contingent upon their levels, offers promising clinical implications in HM management. Moreover, several anticancer agents targeting NRs have been approved by the Food and Drug Administration (FDA). This review highlights the integral function of NRs in HM's pathophysiology and the potential benefits of therapeutically targeting these receptors, suggesting a prospective avenue for more efficient therapeutic interventions against HM.

Triptolide induces apoptotic cell death of multiple myeloma cells via transcriptional repression of Mcl-1

Triptolide, a diterpenoid trioxide purified from the Chinese herb Tripterygium wilfordii Hook F, has been used as a natural medicine in China for hundreds of years. Several reports have demonstrated that triptolide inhibits the proliferation of cancer cells in vitro and reduces the growth of several types of tumors in vivo. To address the potential of triptolide as a novel therapeutic agent for patients with multiple myeloma, we investigated the effects of triptolide on the induction of apoptosis in human multiple myeloma cells in vitro. Triptolide rapidly induces apoptotic cell death in various myeloma cell lines. Triptolide-induced apoptosis in myeloma cells is associated with the loss of mitochondrial transmembrane potential (∆ψm), the release of cytochrome c and Smac/DIABLO from mitochondria into the cytosol, and the activation of caspase-3 and caspase-9. Furthermore, triptolide induces a rapid decline in the levels of Mcl-1 protein that correlates with caspase activation and induction of apoptosis. Inhibition of Mcl-1 synthesis by triptolide occurs at the level of mRNA transcription and is associated with an inhibition of phosphorylation of RNA polymerase II CTD. These results indicate that Mcl-1 is an important target for triptolide-induced apoptosis in myeloma cells that occurs via inhibition of Mcl-1 mRNA transcription coupled with rapid protein degradation through the ubiquitin-proteasome pathway.

Minnelide reduces tumor burden in preclinical models of osteosarcoma

Osteosarcoma is the most common bone cancer in children and adolescents with a 5-year survival rate of about 70%. In this study, we have evaluated the preclinical therapeutic efficacy of the novel synthetic drug, Minnelide, a prodrug of triptolide on osteosarcoma. Triptolide was effective in significantly inducing apoptosis in all osteosarcoma cell lines tested but had no significant effect on the human osteoblast cells. Notably, Minnelide treatment significantly reduced tumor burden and lung metastasis in the orthotopic and lung colonization models. Triptolide/Minnelide effectively downregulated the levels of pro-survival proteins such as heat shock proteins, cMYC, survivin and targets the NF-κB pathway.

Triptolide enhances the sensitivity of multiple myeloma cells to dexamethasone via microRNAs

Recently triptolide (TPL) has been proved to have the capacity to inhibit the proliferation of multiple myeloma (MM) cells as well as leukemic cells in vitro. In the present study, we found a synergistic effect when TPL was added to dexamethasone to induce apoptosis in MM.1S cells. This combination induced a significantly higher proportion of apoptotic cells compared with those treated with each drug separately. TPL down-regulated the expression of miR142 - 5p and miR181a, which have been shown to inhibit glucocorticoid receptor (GR) expression. MicroRNA mimics and inhibitors inhibited or enhanced the synergistic effect between TPL and dexamethasone in inducing apoptosis in MM.1S cells, suggesting an important role of miR142 - 5p and miR181a in GR regulation by TPL. The in vitro proapoptotic effect of TPL associated with dexamethasone reveals a new lead for further clinical investigation into the treatment of patients with MM with TPL.

Role of triptolide in cell proliferation, cell cycle arrest, apoptosis and histone methylation in multiple myeloma U266 cells

Multiple myeloma is an incurable hematological malignancy. Different studies demonstrated the occurrence of genetic and epigenetic alterations in multiple myeloma. Histone lysine methylation has emerged as a central epigenetic change in the organization of eukaryotic chromatin with far-reaching implications for the regulation of cell proliferation, cell-type differentiation, gene expression, genome stability, overall development, and genesis of cancer. Triptolide is the principal active ingredient in extracts from the Chinese herb Tripterygium wilfordii Hook.F (TwHF), and numerous studies have elucidated its antitumor property. Our experiments discovered that triptolide inhibited the proliferation of multiple myeloma cell line U266 in a time- and dose-dependent manner, induced G2/M cell cycle arrest and caspase-dependent apoptosis. Triptolide could decrease the expression of histone H3K4, H3K27 and H3K36 trimethylation in parallel with histone methyltransferases SMYD3, EZH2 and NSD1 respectively, which possibly was the anti-myeloma mechanism of triptolide.