Therapeutic vulnerability of multiple myeloma to MIR17PTi, a first-in-class inhibitor of pri-miR-17-92.

The microRNA (miRNA) cluster miR-17-92 is oncogenic and represents a valuable therapeutic target in c-MYC (MYC)-driven malignancies. Here, we developed novel LNA gapmeR antisense oligonucleotides (ASOs) to induce ribonuclease H-mediated degradation of MIR17HG primary transcripts and consequently prevent biogenesis of miR-17-92 miRNAs (miR-17-92s). The leading LNA ASO, MIR17PTi, impaired proliferation of several cancer cell lines (n = 48) established from both solid and hematologic tumors by on-target antisense activity, more effectively as compared with miR-17-92 inhibitors. By focusing on multiple myeloma (MM), we found that MIR17PTi triggers apoptosis via impairment of homeostatic MYC/miR-17-92 feed-forward loops (FFLs) in patient-derived MM cells and induces MYC-dependent synthetic lethality. We show that alteration of a BIM-centered FFL is instrumental for MIR17PTi to induce cytotoxicity in MM cells. MIR17PTi exerts strong in vivo antitumor activity in nonobese diabetic severe combined immunodeficient mice bearing clinically relevant models of MM, with advantageous safety and pharmacokinetic profiles in nonhuman primates. Altogether, MIR17PTi is a novel pharmacological tool to be tested in early-phase clinical trials against MM and other MYC-driven malignancies.

A p53-dependent tumor suppressor network is induced by selective miR-125a-5p inhibition in multiple myeloma cells.

The analysis of deregulated microRNAs (miRNAs) is emerging as a novel approach to disclose the regulation of tumor suppressor or tumor promoting pathways in tumor cells. Targeting aberrantly expressed miRNAs is therefore a promising strategy for cancer treatment. By miRNA profiling of primary plasma cells from multiple myeloma (MM) patients, we previously reported increased miR-125a-5p levels associated to specific molecular subgroups. On these premises, we aimed at investigating the biological effects triggered by miR-125a-5p modulation in MM cells. Expression of p53 pathway-related genes was down-regulated in MM cells transfected with miR-125a-5p mimics. Luciferase reporter assays confirmed specific p53 targeting at 3'UTR level by miR-125a-5p mimics. Interestingly, bone marrow stromal cells (BMSCs) affected the miR-125a-5p/p53 axis, since adhesion of MM cells to BMSCs strongly up-regulated miR-125a-5p levels, while reduced p53 expression. Moreover, ectopic miR-125a-5p reduced, while miR-125-5p inhibitors promoted, the expression of tumor suppressor miR-192 and miR-194, transcriptionally regulated by p53. Lentiviral-mediated stable inhibition of miR-125a-5p expression in wild-type p53 MM cells dampened cell growth, increased apoptosis and reduced cell migration. Importantly, inhibition of in vitro MM cell proliferation and migration was also achieved by synthetic miR-125a-5p inhibitors and was potentiated by the co-expression of miR-192 or miR-194. Taken together, our data indicate that miR-125a-5p antagonism results in the activation of p53 pathway in MM cells, underlying the crucial role of this miRNA in the biopathology of MM and providing the molecular rationale for the combinatory use of miR-125a inhibitors and miR-192 or miR-194 mimics for MM treatment.

Target therapies plus somatostatin analogs in NETs: a network meta-analysis.

Although combination therapy is not recommended in patients with gastro-entero-pancreatic (GEP) neuroendocrine tumors (NETs), this strategy is widely used in clinical practice. This network meta-analysis of randomized trials evaluates targeted therapies and somatostatin analogues in GEP-advanced NETs, either alone or in combination, comparing the efficacy of different, single or combined treatment strategies in terms of progression-free survival (PFS). Interventions were grouped as analogs, everolimus, everolimus plus SSAs, sunitinib and placebo. In a secondary analysis, we also assessed the efficacy of individual-specific pharmacological treatments vs placebo or each other. From 83 studies identified, 8 randomized controlled trials were selected, with a total of 1849 patients with either functioning or non-functioning NETs. The analysis confirmed the superiority of all treatments over placebo (HR ranging from 0.34, 95% CI: 0.24-0.37 with the combination of everolimus plus SSAs to 0.42, 0.31-0.57 with the analogs; moderate quality of evidence). On ranking analysis, the combination of everolimus plus SSA (P score = 0.86) and then everolimus alone (P score = 0.65) ranked highest in increasing PFS. On comparative evaluation of different interventions, pasireotide (P score = 0.96) and everolimus + octreotide (P score = 0.82) ranked as the best pharmacological treatment options. Our findings support the use of combination therapy in the treatment of functioning and non-functioning GEP NETs. The role of pasireotide should be explored in selected subgroups of patients. Lastly, the combination of everolimus and octreotide appears promising and should be more widely considered in clinical practice.

Systemic Treatment of Patients With Gastrointestinal Cancers During the COVID-19 Outbreak: COVID-19-adapted Recommendations of the National Cancer Institute of Milan.

The current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak poses a major challenge in the treatment decision-making of patients with cancer, who may be at higher risk of developing a severe and deadly SARS-CoV-2 infection compared with the general population. The health care emergency is forcing the reshaping of the daily assessment between risks and benefits expected from the administration of immune-suppressive and potentially toxic treatments. To guide our clinical decisions at the National Cancer Institute of Milan (Lombardy region, the epicenter of the outbreak in Italy), we formulated Coronavirus-adapted institutional recommendations for the systemic treatment of patients with gastrointestinal cancers. Here, we describe how our daily clinical practice has changed due to the pandemic outbreak, with the aim of providing useful suggestions for physicians that are facing the same challenges worldwide.

miR-29b induces SOCS-1 expression by promoter demethylation and negatively regulates migration of multiple myeloma and endothelial cells.

Epigenetic silencing of tumor suppressor genes frequently occurs and may account for their inactivation in cancer cells. We previously demonstrated that miR-29b is a tumor suppressor microRNA (miRNA) that targets de novo DNA methyltransferases and reduces the global DNA methylation of multiple myeloma (MM) cells. Here, we provide evidence that epigenetic activity of miR-29b leads to promoter demethylation of suppressor of cytokine signaling-1 (SOCS-1), a hypermethylated tumor suppressor gene. Enforced expression of synthetic miR-29b mimics in MM cell lines resulted in SOCS-1 gene promoter demethylation, as assessed by Sequenom MassARRAY EpiTYPER analysis, and SOCS-1 protein upregulation. miR-29b-induced SOCS-1 demethylation was associated with reduced STAT3 phosphorylation and impaired NFκB activity. Downregulation of VEGF-A and IL-8 mRNAs could be detected in MM cells transfected with miR-29b mimics as well as in endothelial (HUVEC) or stromal (HS-5) cells treated with conditioned medium from miR-29b-transfected MM cells. Notably, enforced expression of miR-29b mimics increased adhesion of MM cells to HS-5 and reduced migration of both MM and HUVEC cells. These findings suggest that miR-29b is a negative regulator of either MM or endothelial cell migration. Finally, the proteasome inhibitor bortezomib, which induces the expression of miR-29b, decreased global DNA methylation by a miR-29b-dependent mechanism and induced SOCS-1 promoter demethylation and protein upregulation. In conclusion, our data indicate that miR-29b is endowed with epigenetic activity and mediates previously unknown functions of bortezomib in MM cells.