A Novel miRNA Restores the Chemosensitivity of AML Cells Through Targeting FosB

AP-1 inhibitor induces ferroptosis via the PI3K/AKT pathway in multiple myeloma cells

Multiple myeloma (MM) is an incurable malignancy of plasma cells that is sensitive to T-5224, an AP-1 inhibitor. Previous study indicated that T-5224 inhibits proliferation and induces apoptosis in MM cells. However, the high mortality cannot be fully explained. To date, no studies have investigated ferroptosis induced by T-5224 in MM. Therefore, we further investigated the mechanism by which T-5224 kills MM cells. We observed that T-5224 exhibits antimyeloma properties both in vitro and in vivo. T-5224-induced MM cell death was reversed by the ferroptosis-specific inhibitor ferropstatin-1 (Fer-1). The protein levels of the key ferroptosis regulators GPX4 and SLC7A11 were decreased by T-5224 in MM cells. Furthermore, T-5224 reduced the phosphorylation of PI3K and AKT signaling pathway components, ultimately causing MM cell death. Using 740 Y-P, a PI3K activator, and Fer-1, a ferroptosis inhibitor, we discovered that T-5224 induces ferroptosis through the PI3K/AKT pathway. Bortezomib (BTZ), an FDA-approved drug for MM treatment, can be administered in combination with other agents. We evaluated the synergistic effect of BTZ combined with AP-1 inhibitors on MM in vivo. Our findings provide a better theoretical basis for the potential mechanism of T-5224 and a new perspective on MM treatment.

The selective activator protein-1 inhibitor T-5224 regulates the IRF4/MYC axis and exerts cooperative antimyeloma activity with bortezomib

The activating protein-1 (AP-1) transcription factors (TFs) have been associated with many different cancer types and are promising therapeutic targets in logical malignancies. However, the mechanisms of their role in multiple myeloma (MM) remain elusive. The present study determined and compared the mRNA and protein expression levels of the AP-1 family member JunB in CD138+ mononuclear cells from MM patients and healthy donors. Herein, we investigated the effect of T-5224, an inhibitor of JUN/AP-1, on MM. We found that the cytotoxicity of T-5224 toward myeloma is due to its ability to induce cell apoptosis, inhibit proliferation, and induce cell cycle arrest by increasing the levels of cleaved caspase3/7 and concomitantly inhibiting the IRF4/MYC axis. We also noticed that siJunB-mediated deletion of JunB/AP-1 enhanced MM cell apoptosis and affected cell proliferation. The software PROMO was used in the present study to predict the AP-1 TF that may bind the promoter region of IRF4. We confirmed the correlation between JunB/AP-1 and IRF4. Given that bortezomib (BTZ) facilitates IRF4 degradation in MM cells, we applied combination treatment of BTZ with T-5224. T-5224 and BTZ exerted synergistic effects, and T-5224 reversed the effect of BTZ on CD138+ primary resistance in MM cells, in part due to suppression of the IRF4/MYC axis. Our results suggest that targeting AP-1 TFs is a promising therapeutic strategy for MM. Additionally, targeting both AP-1 and IRF4 with T-5224 may be a synergistic therapeutic strategy for this clinically challenging subset of MM.

c-FOS is an integral component of the IKZF1 transactivator complex and mediates lenalidomide resistance in multiple myeloma

BACKGROUND

The immunomodulatory drug lenalidomide, which is now widely used for the treatment of multiple myeloma (MM), exerts pharmacological action through the ubiquitin-dependent degradation of IKZF1 and subsequent down-regulation of interferon regulatory factor 4 (IRF4), a critical factor for the survival of MM cells. IKZF1 acts principally as a tumour suppressor via transcriptional repression of oncogenes in normal lymphoid lineages. In contrast, IKZF1 activates IRF4 and other oncogenes in MM cells, suggesting the involvement of unknown co-factors in switching the IKZF1 complex from a transcriptional repressor to an activator. The transactivating components of the IKZF1 complex might promote lenalidomide resistance by residing on regulatory regions of the IRF4 gene to maintain its transcription after IKZF1 degradation.

METHODS

To identify unknown components of the IKZF1 complex, we analyzed the genome-wide binding of IKZF1 in MM cells using chromatin immunoprecipitation-sequencing (ChIP-seq) and screened for the co-occupancy of IKZF1 with other DNA-binding factors on the myeloma genome using the ChIP-Atlas platform.

RESULTS

We found that c-FOS, a member of the activator protein-1 (AP-1) family, is an integral component of the IKZF1 complex and is primarily responsible for the activator function of the complex in MM cells. The genome-wide screening revealed the co-occupancy of c-FOS with IKZF1 on the regulatory regions of IKZF1-target genes, including IRF4 and SLAMF7, in MM cells but not normal bone marrow progenitors, pre-B cells or mature T-lymphocytes. c-FOS and IKZF1 bound to the same consensus sequence as the IKZF1 complex through direct protein-protein interactions. The complex also includes c-JUN and IKZF3 but not IRF4. Treatment of MM cells with short-hairpin RNA against FOS or a selective AP-1 inhibitor significantly enhanced the anti-MM activity of lenalidomide in vitro and in two murine MM models. Furthermore, an AP-1 inhibitor mitigated the lenalidomide resistance of MM cells.

CONCLUSIONS

C-FOS determines lenalidomide sensitivity and mediates drug resistance in MM cells as a co-factor of IKZF1 and thus, could be a novel therapeutic target for further improvement of the prognosis of MM patients.

Phosphorylation at Ser 727 Increases STAT3 Interaction with PKCε Regulating Neuron–Glia Crosstalk via IL-6-Mediated Hyperalgesia In Vivo and In Vitro

Methods

A rat hyperalgesia model was induced using an intraplantar injection of Freund's complete adjuvant (FCA) or an intrathecal injection of IL-6. Mechanical allodynia was evaluated using von Frey filament tests after intrathecal injections of T-5224 (c-Fos/AP-1 inhibitor), minocycline (Mino, a specific microglia inhibitor), L-2-aminoadipic acid (LAA, an astroglial toxin), PKCε inhibitor peptide, APTSTAT3-9R (STAT3 inhibitor), or anti-IL-6 antibody. The c-Fos, GFAP, Iba-1, PKCε, STAT3, pSTAT3^Tyr705 and pSTAT3^Ser727, and IL-6 expression at the spinal cord level was assessed by Western blot analysis. The interactive effects of PKCε and STAT3 were determined using immunofluorescence staining and immunoprecipitation in vivo and in vitro. Interleukin-6 promoter activity was examined using luciferase assays.

Results

T-5224, Mino, and LAA attenuated FCA- or IL-6-mediated inflammatory pain, with a decrease in c-Fos, GFAP, Iba-1, PKCε, and IL-6 expression. PKCε inhibitor peptide and APTSTAT3-9R reversed FCA-induced nociceptive behavior, while decreasing pSTAT3^Ser727, IL-6, c-Fos, GFAP, and Iba-1 expression and PKCε and STAT3 coexpression. Interleukin-6 promoter activity increased in the presence of PKCε and STAT3. The interaction with PKCε increased on phosphorylating STAT3 at Ser727 but not at Tyr705.

Conclusion

STAT3 phosphorylation at Ser 727 and the interaction with PKCε contribute to hyperalgesia via the IL-6-mediated signaling pathway, thus regulating neuron–glia crosstalk during inflammatory pain.

Interplay between endoplasmic reticulum stress and non-coding RNAs in cancer

To survive, cancer cells are subjected to various internal and external adverse factors, including genetic mutations, hypoxia, nutritional deficiencies, and drug toxicity. All of these factors result in the accumulation of unfolded proteins in the endoplasmic reticulum, which leads to a condition termed endoplasmic reticulum stress (ER stress) and triggers the unfolded protein response (UPR). UPR downstream components strictly control transcription and translation reprogramming to ensure selective gene expression, including that of non-coding RNA (ncRNAs), to adapt to adverse environments. NcRNAs, including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), play important roles in regulating target gene expression and protein translation, and their aberrant expression is related to tumor development. Dysregulation of ncRNAs is involved in the regulation of various cellular characteristics of cancer cells, including growth, apoptosis, metastasis, angiogenesis, drug sensitivity, and tumor stem cell properties. Notably, ncRNAs and ER stress can regulate each other and collaborate to determine the fate of tumor cells. Therefore, investigating the interaction between ER stress and ncRNAs is crucial for developing effective cancer treatment and prevention strategies. In this review, we summarize the ER stress-triggered UPR signaling pathways involved in carcinogenesis followed by the mutual regulation of ER stress and ncRNAs in cancer, which provide further insights into the understanding of tumorigenesis and therapeutic strategies.