Growth Of Multiple Myeloma Xenografts Research Articles

Anti-bacterial and anti-viral nanchangmycin displays anti-myeloma activity by targeting Otub1 and c-Maf

As a deubiqutinase Otub1 stabilizes and promotes the oncogenic activity of the transcription factor c-Maf in multiple myeloma (MM), a malignancy of plasma cells. In the screen for bioactive inhibitors of the Otub1/c-Maf axis for MM treatment, nanchangmycin (Nam), a polyketide antibiotic, was identified to suppress c-Maf activity in the presence of Otub1. By suppressing Otub1, Nam induces c-Maf polyubiquitination and subsequent degradation in proteasomes but does not alter its mRNA level. Consistently, Nam downregulates the expression of CCND2, ARK5, and ITGB7, the downstream genes regulated by c-Maf, and promotes MM cell apoptosis as evidenced by PARP and Caspase-3 cleavage, as well as Annexin V staining. In line with the hypothesis, overexpression of Otub1 partly rescues Nam-induced MM cell apoptosis, and interestingly, when Otub1 is knocked down, Nam-decreased MM cell survival is also partly ablated, suggesting Otub1 is essential for Nam anti-MM activity. Nam also displays potent anti-MM activity synergistically with Doxorubicin or lenalidomide. In the in vivo assays, Nam almost completely suppresses the growth of MM xenografts in nude mice at low dosages but it shows no toxicity. Given its safety and efficacy, Nam has a potential for MM treatment by targeting the Otub1/c-Maf axis.

Proteolysis targeting chimeric molecules as therapy for multiple myeloma: efficacy, biomarker and drug combinations.

Proteolysis targeting chimeric molecule ARV 825 causes ubiquitination of bromodomains resulting in their efficient degradation by proteasome activity. Bromodomain degradation down-regulates MYC transcription contributing to growth inhibition of various human cancers. We examined the therapeutic potential of ARV 825 against multiple myeloma (MM) cells both in vitro and in vivo. In a dose-dependent manner, ARV 825 inhibited proliferation of 13 human MM cell lines and three fresh patient samples, and was associated with cell cycle arrest and apoptosis. ARV 825 rapidly and efficiently degraded BRD 2 and BRD 4. Sensitivity of MM cells to ARV 825 was positively correlated with cereblon levels. RNA sequencing analysis showed important genes such as CCR1, RGS, MYB and MYC were down-regulated by ARV 825. A total of 170 small molecule inhibitors were screened for synergy with ARV 825. Combination of ARV 825 with inhibitor of either dual PI3K/mTOR, CRM1, VEGFR, PDGFRα/b, FLT3, IGF-1R, protein kinase C, CBP-EP300 or JAK1/2 showed synergistic activity. Importantly, ARV 825 significantly inhibited the growth of MM xenografts and improved mice survival. Taken together, our results, in conjunction with recently published findings, provide a rationale for investigating the efficacy of ARV 825 for MM, use of cereblon as a biomarker for therapy of MM patients, and the combination of ARV 825 with small molecule inhibitors to improve the outcome of MM patients.

Small molecule CP-31398 induces reactive oxygen species-dependent apoptosis in human multiple myeloma.

Reactive oxygen species (ROS) are normal byproducts of a wide variety of cellular processes. ROS have dual functional roles in cancer cell pathophysiology. At low to moderate levels, ROS act as signaling transducers to activate cell proliferation, migration, invasion, and angiogenesis. In contrast, high levels of ROS induce cell death. In multiple myeloma (MM), ROS overproduction is the trigger for apoptosis induced by several anticancer compounds, including proteasome inhibitors. However, no drugs for which oxidative stress is the main mechanism of action are currently used for treatment of MM in clinical situations. In this study, we demonstrate that the p53-activating small molecule CP-31398 (CP) effectively inhibits the growth of MM cell lines and primary MM isolates from patients. CP also suppresses the growth of MM xenografts in mice. Mechanistically, CP was found to induce intrinsic apoptosis in MM cells via increasing ROS production. Interestingly, CP-induced apoptosis occurs regardless of the p53 status, suggesting that CP has additional mechanisms of action. Our findings thus indicate that CP could be an attractive candidate for treatment of MM patients harboring p53 abnormalities; this satisfies an unmet clinical need, as such individuals currently have a poor prognosis.

3-Aroylindoles display antitumor activity in vitro and in vivo: Effects of N1-substituents on biological activity

A series of 3-aroylindole hydroxamic acids (10–17) were developed based on the concept of a structural combination of tubulin and histone deacetylase (HDAC) inhibitors. This was accomplished by introducing hydroxamic acid-containing moieties at the N1 position of the tubulin assembly inhibitor, compound 9 (SCB01A, BPR0L075, phase II trial). Most of synthetic compounds produced in this way displayed comparable HDAC inhibitory activity, and four (10, 12–14) of them also inhibit tubulin assembly. Notably, compound 12 possesses not only tubulin and HDAC inhibitory activity but also shows HDAC6 selectivity over other HDAC isoforms. In addition, it exhibits remarkable inhibitory activity against the growth cancer cells in vitro and in vivo (PC3 and RPMI-8226 cells). Notably, it suppresses the growth of multiple myeloma xenografts without leading to the death of teated animals like reference compound. In sum, this study provided potential compounds with safer profiles for cancer treatment.

Highlights of This Issue

The evidence that aspirin prevents cancer is compelling; however, the underlying mechanism leading to its anti-cancer effect is enigmatic. In this research article, cyclin A2 and CDK2 are demonstrated to be novel targets of aspirin and its primary metabolite, salicylic acid. Both therapeutic agents caused down-regulation of cyclin A2 and CDK2, at the protein and mRNAs levels, in a diverse panel of cancer cells and resulted in a reduction in CDK2 activity. Importantly, it is also demonstrated that CDK2 is a novel salicylic acid binding protein. These results show that the anti-cancer effects of aspirin occur through down-regulation of cell cycle regulatory proteins.Multiple myeloma resides in a hypoxic environment and shows signs of an induced hypoxic response that contributes to tumorigenesis and tumor drug resistance. Targeting this adaptive hypoxic response would have important ramifications for treating this disease. To test this, Mysore and colleagues used a Pyrrole-Imidazole polyamide that can displace a major regulator of hypoxic response, HIF1, from its DNA-binding site. Evidence shows that the polyamide suppressed growth of multiple myeloma xenografts in mice and inhibited the hypoxic response in vitro and in vivo; thus, revealing the therapeutic utility of these molecules in the treatment of multiple myeloma.Pancreatic cancer is a deadly and highly metastatic disease frequently harboring activating mutations in the KRAS oncogene. MicroRNAs (miRs) are important regulators of gene expression with an established role in cancer pathogenesis. Here, miR-31 is identified as a transcriptional target of the RAS-MAPK signaling pathway. The miR-31 host gene promoter is activated by the transcription factor ELK1. Enforced expression of miR-31 enhanced invasion-migration of pancreatic cancer cells via down regulation of the miR-31 target RASA1 and activation of RHOA. These results implicate miR-31 as a novel effector in the RAS-transformation program and demonstrate a mechanism for the metastatic behavior of pancreatic cancer.Cancer-associated fibroblasts (CAFs) are a vital cellular component of the tumor microenvironment (TME) and are a recognized source of intratumoral collagen. This study is important because it shows that CAFs not only produce collagen but also regulate the types of cross-links that form between collagen strands and contribute to the biomechanical properties of tumor stroma. Mechanistically, this activity of CAFs was mediated by lysyl hydroxylase 2 (PLOD2/LH2), which strengthens the growing body of evidence that targeting LH2 has the potential to suppress the growth and metastasis of tumors in patients.

A Cyclin-Dependent Kinase Inhibitor, Dinaciclib, Impairs Homologous Recombination and Sensitizes Multiple Myeloma Cells to PARP Inhibition.

PARP1/2 are required for single-strand break repair, and their inhibition causes DNA replication fork collapse and double-strand break (DSB) formation. These DSBs are primarily repaired via homologous recombination (HR), a high-fidelity repair pathway. Should HR be deficient, DSBs may be repaired via error-prone nonhomologous end-joining mechanisms, or may persist, ultimately resulting in cell death. The combined disruption of PARP and HR activities thus produces synthetic lethality. Multiple myeloma cells are characterized by chromosomal instability and pervasive DNA damage, implicating aberrant DNA repair. Cyclin-dependent kinases (CDK), upstream modulators of HR, are dysregulated in multiple myeloma. Here, we show that a CDK inhibitor, dinaciclib, impairs HR repair and sensitizes multiple myeloma cells to the PARP1/2 inhibitor ABT-888. Dinaciclib abolishes ABT-888-induced BRCA1 and RAD51 foci and potentiates DNA damage, indicated by increased γH2AX foci. Dinaciclib treatment reduces expression of HR repair genes, including Rad51, and blocks BRCA1 phosphorylation, a modification required for HR repair, thus inhibiting HR repair of chromosome DSBs. Cotreatment with dinaciclib and ABT-888 in vitro resulted in synthetic lethality of multiple myeloma cells, but not normal CD19(+) B cells, and slowed growth of multiple myeloma xenografts in SCID mice almost two-fold. These findings support combining dinaciclib with PARP inhibitors for multiple myeloma therapy. Mol Cancer Ther; 15(2); 241-50. ©2015 AACR.

Pleurocidin-family cationic antimicrobial peptides mediate lysis of multiple myeloma cells and impair the growth of multiple myeloma xenografts

Multiple myeloma is a common hematological malignancy that urgently requires new approaches to treatment, since the disease is not curable using current chemotherapeutic regimens. The aim of this study was to determine whether human and mouse multiple myeloma cells are killed by the pleurocidin-like cationic antimicrobial peptides NRC-03 and NRC-07, previously shown to be active against breast cancer cells. We demonstrate here that NRC-03 and NRC-07 bound to and rapidly killed multiple myeloma cells by causing extensive membrane damage, as well as DNA cleavage. NRC-03 showed greater binding to multiple myeloma cells and a more potent cytotoxic effect than NRC-07. In addition, intratumoral injections of NRC-03 impaired the growth of multiple myeloma xenografts in immune-deficient mice. We conclude that NRC-03 warrants further investigation for its possible use in the treatment of multiple myeloma.