Though miR-205 function has been largely characterized, the nature of its host gene, MIR205HG, is still completely unknown. Here, we show that only lowly expressed alternatively spliced MIR205HG transcripts act as de facto pri-miRNAs, through a process that involves Drosha to prevent unfavorable splicing and directly mediate miR-205 excision. Notably, MIR205HG-specific processed transcripts revealed to be functional per se as nuclear long noncoding RNA capable of regulating differentiation of human prostate basal cells through control of the interferon pathway. At molecular level, MIR205HG directly binds the promoters of its target genes, which have an Alu element in proximity of the Interferon-Regulatory Factor (IRF) binding site, and represses their transcription likely buffering IRF1 activity, with the ultimate effect of preventing luminal differentiation. As MIR205HG functions autonomously from (albeit complementing) miR-205 in preserving the basal identity of prostate epithelial cells, it warrants reannotation as LEADeR (Long Epithelial Alu-interacting Differentiation-related RNA).

Acute promyelocytic leukemia (APL) is epitomized by the chromosomal translocation t(15;17) and the resulting oncogenic fusion protein PML‐RARα. Although acting primarily as a transcriptional repressor, PML‐RARα can also exert functions of transcriptional co‐activation. Here, we find that PML‐RARα stimulates transcription driven by HIF factors, which are critical regulators of adaptive responses to hypoxia and stem cell maintenance. Consistently, HIF‐related gene signatures are upregulated in leukemic promyelocytes from APL patients compared to normal promyelocytes. Through in vitro and in vivo studies, we find that PML‐RARα exploits a number of HIF‐1α‐regulated pro‐leukemogenic functions that include cell migration, bone marrow (BM) neo‐angiogenesis and self‐renewal of APL blasts. Furthermore, HIF‐1α levels increase upon treatment of APL cells with all‐ trans retinoic acid (ATRA). As a consequence, inhibiting HIF‐1α in APL mouse models delays leukemia progression and exquisitely synergizes with ATRA to eliminate leukemia‐initiating cells (LICs).

Epithelioid sarcoma (ES) is a rare mesenchymal malignancy marked by SMARCB1/INI1 deficiency. Retrospective clinical data report on the activity of anthracycline- and gemcitabine-based regimens. EZH2 inhibitors are currently being tested in clinical trials. Since comparisons of these agents are unlikely to be prospectively evaluated in the clinics, we took advantage of an INI1-deficient proximal-type ES patient-derived xenograft (PDX ES-1) to comparatively assess its preclinical antitumor activity. Mice were treated with doxorubicin and ifosfamide, singly or in combination, gemcitabine, and the EZH2 inhibitor EPZ-011989. Comparable antitumor activity (max tumor volume inhibition: ~90%) was caused by gemcitabine, EPZ-011989, and the doxorubicin–ifosfamide combination. The integration of RNAseq data, generated on tumors obtained from untreated and EPZ-011989-treated mice, and results from functional studies, carried out on the PDX-derived ES-1 cell line, revealed autophagy induction as a possible survival mechanism in residual tumor cells following EPZ-011989 treatment and identified HMGA2 as a main player in this process. Our data support the clinical use of gemcitabine and the doxorubicin–ifosfamide combination, confirm EZH2 as a therapeutic target in proximal-type ES, and suggest autophagy as a cytoprotective mechanism against EZH2 inhibition.

Background: Acute promyelocytic leukemia (APL) is a sub-type of acute myeloid leukemia (AML) characterized by a block of myeloid differentiation at the promyelocytic stage and the predominant t(15:17) chromosomal translocation. We have previously determined that cells from APL patients show increased expression of genes regulated by hypoxia-inducible transcription factors (HIFs) compared to normal promyelocytes. HIFs regulate crucial aspects of solid tumor progression and are currently being implicated in leukemogenesis. Methods: To investigate the contribution of hypoxia-related signaling in APL compared to other AML sub-types, we reverse engineered a transcriptional network from gene expression profiles of AML patients’ samples, starting from a list of direct target genes of HIF-1. A HIF-1-dependent subnetwork of genes specifically dysregulated in APL was derived from the comparison between APL and other AMLs. Results: Interestingly, this subnetwork shows a unique involvement of genes related to extracellular matrix interaction and cell migration, with decreased expression of genes involved in cell adhesion and increased expression of genes implicated in motility and invasion, thus unveiling the presence of characteristics of epithelial-mesenchymal transition (EMT). We observed that the genes of this subnetwork, whose dysregulation shows a peculiar pattern across different AML sub-types, distinguish malignant from normal promyelocytes, thus ruling out dependence on a myeloid developmental stage. Also, expression of these genes is reversed upon treatment of APL-derived NB4 cells with all-trans retinoic acid and cell differentiation. Conclusions: Our data suggest that pathways related to EMT-like processes can be implicated also in hematological malignancies besides solid tumors, and can identify specific AML sub-types.

Hypoxia inducible factor-1α regulates a pro-invasive phenotype in acute monocytic leukemia Hypoxia inducible factor-1α regulates a pro-invasive phenotype in acute monocytic leukemia

Triple-negative breast cancer (TNBC) is an aggressive disease with limited therapeutic options. Here, we pursued a combinatorial therapeutic approach to enhance the activity of selinexor, the first-in-class XPO1 inhibitor, by miR-34a ectopic expression in human TNBC experimental models. Anti-proliferative activity induced by selinexor and miR-34a expression, singly and in combination, was evaluated by MTS assay and cell counting. The effect of treatments on survivin and apoptosis-related proteins was assessed by western blotting and ELISA. The antitumor and toxic effects of individual and combined treatments were evaluated on TNBC orthotopic xenografts in SCID mice. Selinexor consistently showed anti-proliferative activity, although to a variable extent, in the different TNBC cell lines and caused the impairment of survivin expression and intracellular distribution, accompanied by apoptosis induction. Consistent with in vitro data, the XPO1 inhibitor variably affected the growth of TNBC orthotopic xenografts. miR-34a cooperated with selinexor to reduce survivin expression and improved its anti-proliferative activity in TNBC cells. Most importantly, miR-34a expression markedly enhanced selinexor antitumor activity in the less sensitive TNBC xenograft model, in absence of toxicity. Our data form a solid foundation for promoting the use of a miR-34a-based approach to improve the therapeutic efficacy of selinexor in TNBC patients.