The Clinical Effectiveness of Denosumab (Prolia®) for the Treatment of Osteoporosis in Postmenopausal Women, Compared to Bisphosphonates, Selective Estrogen Receptor Modulators (SERM), and Placebo: A Systematic Review and Network Meta-Analysis.

To assess the effectiveness and safety of denosumab (Prolia®) compared to bisphosphonates (alendronate, ibandronate, risedronate, zoledronate), selective estrogen receptor modulators (SERMs; bazedoxifene, raloxifene) or placebo, for the treatment of osteoporosis in postmenopausal women (PMW). Systematic searches were run in PubMed, Embase & Cochrane Library on 27-April-2022. Randomized controlled trials (RCTs) that included osteoporotic PMW allocated to denosumab, SERMs, bisphosphonates, or placebo were eligible for inclusion. RCTs were appraised using Cochrane Risk of Bias 2.0. Bayesian network and/or pairwise meta-analyses were conducted on predetermined outcomes (i.e. vertebral/nonvertebral fractures, bone mineral density [BMD], mortality, adverse events [AEs], serious AEs (SAEs), withdrawals due to AEs, AEs caused by denosumab discontinuation). A total of 12 RCTs (k = 22 publications; n = 25,879 participants) were included in the analyses. Denosumab, reported a statistically significant increase in lumbar spine (LS) and total hip (TH) BMD, compared to placebo. Similarly, denosumab also resulted in a statistically significant increase in TH BMD compared to the raloxifene and bazedoxifene. However, relative to denosumab, alendronate, ibandronate and risedronate resulted in significant improvements in both femoral neck (FN) and LS BMD. With regards to vertebral fractures and all safety outcomes, there were no statistically significant differences between denosumab and any of the comparator. Relative to placebo, denosumab was associated with significant benefits in both LS and TH BMD. Additionally, denosumab (compared to placebo) was not associated with reductions in vertebral and nonvertebral fractures. Finally, denosumab was not associated with improvement in safety outcomes, compared to placebo. These findings should be interpreted with caution as some analyses suffered from statistical imprecision.

The clinical effectiveness of denosumab (Prolia®) in patients with hormone-sensitive cancer receiving endocrine therapy, compared to bisphosphonates, selective estrogen receptor modulators (SERM), and placebo: a systematic review and network meta-analysis.

This systematic review (SR) assessed the use of denosumab (Prolia®) to treat osteoporosis in cancer patients receiving endocrine therapy. Denosumab was found to prevent vertebral fractures and improve bone mineral density in cancer patients with osteoporosis. This is the first SR to assess treating osteoporotic cancer patients with denosumab. PURPOSE: This study assessed the effectiveness and safety of denosumab (Prolia®) compared to bisphosphonates (alendronate, ibandronate, risedronate, zoledronate), selective estrogen receptor modulators (SERMs) (bazedoxifene, raloxifene) and placebo for the treatment of osteoporosis in hormone-sensitive cancer patients receiving endocrine therapy (men with prostate cancer [MPC] on hormone ablation therapy [HAT], and women with breast cancer [WBC] on adjuvant aromatase inhibitor therapy [AAIT]). METHODS: Systematic literature searches were conducted in three biomedical databases to identify randomized controlled trials (RCTs). Frequentist network meta-analyses and/or pairwise meta-analyses were performed on predetermined outcomes (i.e., vertebral/nonvertebral fractures, bone mineral density [BMD], mortality, treatment-related adverse events [AEs], serious AEs [SAEs], withdrawal due to treatment-related AEs). RESULTS: A total of 14 RCTs (15 publications) were included. Denosumab was found to prevent vertebral fractures in cancer patients receiving endocrine therapy, relative to placebo. Similarly, denosumab, zoledronate, and alendronate improved BMD at the femoral neck (FN) and lumbar spine (LS) in MPC on HAT, relative to placebo. Denosumab, ibandronate and risedronate improved BMD at the LS and total hip (TH) in WBC on AAIT, relative to placebo. Denosumab and risedronate improved trochanteric (TRO) BMD in WBC on AAIT, relative to placebo. Similarly, denosumab improved FN BMD in WBC on AAIT. CONCLUSION: In MPC on HAT, denosumab (relative to placebo) was effective at preventing vertebral fractures and improving BMD at the FN and LS. Moreover, in WBC on AAIT, denosumab (relative to placebo) improved BMD at the FN, LS, TH, and TRO, as well as prevent vertebral fracture.

E2F mediates enhanced alternative polyadenylation in proliferation.

BACKGROUND: The majority of mammalian genes contain multiple poly(A) sites in their 3' UTRs. Alternative cleavage and polyadenylation are emerging as an important layer of gene regulation as they generate transcript isoforms that differ in their 3' UTRs, thereby modulating genes' response to 3' UTR-mediated regulation. Enhanced cleavage at 3' UTR proximal poly(A) sites resulting in global 3' UTR shortening was recently linked to proliferation and cancer. However, mechanisms that regulate this enhanced alternative polyadenylation are unknown. RESULTS: Here, we explored, on a transcriptome-wide scale, alternative polyadenylation events associated with cellular proliferation and neoplastic transformation. We applied a deep-sequencing technique for identification and quantification of poly(A) sites to two human cellular models, each examined under proliferative, arrested and transformed states. In both cell systems we observed global 3' UTR shortening associated with proliferation, a link that was markedly stronger than the association with transformation. Furthermore, we found that proliferation is also associated with enhanced cleavage at intronic poly(A) sites. Last, we found that the expression level of the set of genes that encode for 3'-end processing proteins is globally elevated in proliferation, and that E2F transcription factors contribute to this regulation. CONCLUSIONS: Our results comprehensively identify alternative polyadenylation events associated with cellular proliferation and transformation, and demonstrate that the enhanced alternative polyadenylation in proliferative conditions results not only in global 3' UTR shortening but also in enhanced premature cleavage in introns. Our results also indicate that E2F-mediated co-transcriptional regulation of 3'-end processing genes is one of the mechanisms that links enhanced alternative polyadenylation to proliferation.

The poly(A)-binding protein nuclear 1 suppresses alternative cleavage and polyadenylation sites.

Alternative cleavage and polyadenylation (APA) is emerging as an important layer of gene regulation. Factors controlling APA are largely unknown. We developed a reporter-based RNAi screen for APA and identified PABPN1 as a regulator of this process. Genome-wide analysis of APA in human cells showed that loss of PABPN1 resulted in extensive 3' untranslated region shortening. Messenger RNA transcription, stability analyses, and in vitro cleavage assays indicated enhanced usage of proximal cleavage sites (CSs) as the underlying mechanism. Using Cyclin D1 as a test case, we demonstrated that enhanced usage of proximal CSs compromises microRNA-mediated repression. Triplet-repeat expansion in PABPN1 (trePABPN1) causes autosomal-dominant oculopharyngeal muscular dystrophy (OPMD). The expression of trePABPN1 in both a mouse model of OPMD and human cells elicited broad induction of proximal CS usage, linked to binding to endogenous PABPN1 and its sequestration in nuclear aggregates. Our results elucidate a novel function for PABPN1 as a suppressor of APA.

CLEC5A (MDL-1) is a novel PU.1 transcriptional target during myeloid differentiation.

C-type lectin domain family 5, member A (CLEC5A), also known as myeloid DNAX activation protein 12 (DAP12)-associating lectin-1 (MDL-1), is a cell surface receptor strongly associated with the activation and differentiation of myeloid cells. CLEC5A associates with its adaptor protein DAP12 to activate a signaling cascade resulting in activation of downstream kinases in inflammatory responses. Currently, little is known about the transcriptional regulation of CLEC5A. We identified CLEC5A as one of the most highly induced genes in a microarray gene profiling experiment of PU.1 restored myeloid PU.1-null cells. We further report that CLEC5A expression is significantly reduced in several myeloid differentiation models upon PU.1 inhibition during monocyte/macrophage or granulocyte differentiation. In addition, CLEC5A mRNA expression was significantly lower in primary acute myeloid leukemia (AML) patient samples than in macrophages and granulocytes from healthy donors. Moreover, we found activation of a CLEC5A promoter reporter by PU.1 as well as in vivo binding of PU.1 to the CLEC5A promoter. Our findings indicate that CLEC5A expression in monocyte/macrophage and granulocytes is regulated by PU.1.

Inactivation of the hypermethylated in cancer 1 tumour suppressor--not just a question of promoter hypermethylation?

The chromosomal region 17p13.3 is frequently deleted or epigenetically silenced in a variety of human cancers. It includes the hypermethylated in cancer 1 (HIC1) gene placed telomerically to the p53 tumour suppressor gene. HIC1 encodes a transcriptional repressor, and its targets identified to date are genes involved in proliferation, tumour growth and angiogenesis. In addition, HIC1 functionally cooperates with p53 to suppress cancer development. Frequent allelic loss at position 17p13.1 in human cancers often points to mutations of the tumour suppressor p53. However, in a variety of cancer types, allelic loss of the short arm of chromosome 17 may hit regions distal to p53 and, interestingly, without leading to p53 mutations. Furthermore, the neighbouring region 17p13.3 often shows loss of heterozygosity or DNA hypermethylation in various types of solid tumours and leukaemias. In line with this concept, Wales et al. described a new potential tumour suppressor in this region and named it hypermethylated in cancer 1 (HIC1). Further, it was shown that in the majority of cases hypermethylation of this chromosomal region leads to epigenetic inactivation of HIC1. A role for HIC1 in tumour development is further supported by a mouse model, since various spontaneous, age- and gender-specific malignant tumours occur in heterozygous Hic1+/- knockout mice. Furthermore, exogenously delivered HIC1 leads to a significant decrease in clonogenic survival in cancer cell lines. This review highlights the role of HIC1 inactivation in solid tumours and particularly in leukaemia development.

Scavenger chemokine (CXC motif) receptor 7 (CXCR7) is a direct target gene of HIC1 (hypermethylated in cancer 1).

The tumor suppressor gene HIC1 (Hypermethylated in Cancer 1) that is epigenetically silenced in many human tumors and is essential for mammalian development encodes a sequence-specific transcriptional repressor. The few genes that have been reported to be directly regulated by HIC1 include ATOH1, FGFBP1, SIRT1, and E2F1. HIC1 is thus involved in the complex regulatory loops modulating p53-dependent and E2F1-dependent cell survival and stress responses. We performed genome-wide expression profiling analyses to identify new HIC1 target genes, using HIC1-deficient U2OS human osteosarcoma cells infected with adenoviruses expressing either HIC1 or GFP as a negative control. These studies identified several putative direct target genes, including CXCR7, a G-protein-coupled receptor recently identified as a scavenger receptor for the chemokine SDF-1/CXCL12. CXCR7 is highly expressed in human breast, lung, and prostate cancers. Using quantitative reverse transcription-PCR analyses, we demonstrated that CXCR7 was repressed in U2OS cells overexpressing HIC1. Inversely, inactivation of endogenous HIC1 by RNA interference in normal human WI38 fibroblasts results in up-regulation of CXCR7 and SIRT1. In silico analyses followed by deletion studies and luciferase reporter assays identified a functional and phylogenetically conserved HIC1-responsive element in the human CXCR7 promoter. Moreover, chromatin immunoprecipitation (ChIP) and ChIP upon ChIP experiments demonstrated that endogenous HIC1 proteins are bound together with the C-terminal binding protein corepressor to the CXCR7 and SIRT1 promoters in WI38 cells. Taken together, our results implicate the tumor suppressor HIC1 in the transcriptional regulation of the chemokine receptor CXCR7, a key player in the promotion of tumorigenesis in a wide variety of cell types.

The tumor suppressor gene hypermethylated in cancer 1 is transcriptionally regulated by E2F1.

The Hypermethylated in Cancer 1 (HIC1) gene encodes a zinc finger transcriptional repressor that cooperates with p53 to suppress cancer development. We and others recently showed that HIC1 is a transcriptional target of p53. To identify additional transcriptional regulators of HIC1, we screened a set of transcription factors for regulation of a human HIC1 promoter reporter. We found that E2F1 strongly activates the full-length HIC1 promoter reporter. Promoter deletions and mutations identified two E2F responsive elements in the HIC1 core promoter region. Moreover, in vivo binding of E2F1 to the HIC1 promoter was shown by chromatin immunoprecipitation assays in human TIG3 fibroblasts expressing tamoxifen-activated E2F1. In agreement, activation of E2F1 in TIG3-E2F1 cells markedly increased HIC1 expression. Interestingly, expression of E2F1 in the p53(-/-) hepatocellular carcinoma cell line Hep3B led to an increase of endogenous HIC1 mRNA, although bisulfite genomic sequencing of the HIC1 promoter revealed that the region bearing the two E2F1 binding sites is hypermethylated. In addition, endogenous E2F1 induced by etoposide treatment bound to the HIC1 promoter. Moreover, inhibition of E2F1 strongly reduced the expression of etoposide-induced HIC1. In conclusion, we identified HIC1 as novel E2F1 transcriptional target in DNA damage responses.

HIC1 tumour suppressor gene is suppressed in acute myeloid leukaemia and induced during granulocytic differentiation.

A hallmark of acute myeloid leukaemia (AML) is a block in differentiation caused by deregulated gene expression. The tumour suppressor Hypermethylated In Cancer 1 (HIC1) is a transcriptional repressor, which is epigenetically silenced in solid cancers. HIC1 mRNA expression was found to be low in 128 patient samples of AML and CD34+ progenitor cells when compared with terminally differentiated granulocytes. HIC1 mRNA was induced in a patient with t(15;17)-positive acute promyelocytic leukaemia receiving all-trans retinoic acid (ATRA) therapy. We therefore investigated whether HIC1 plays a role in granulocytic differentiation and whether loss of function of this gene might contribute to the differentiation block in AML. We evaluated HIC1 mRNA levels in HL-60 and U-937 cells upon ATRA-induced differentiation and in CD34+ progenitor cells after granulocyte colony-stimulating factor-induced differentiation. In both models of granulocytic differentiation, we observed significant HIC1 induction. When HIC1 mRNA was suppressed in HL-60 cells using stably expressed short hairpin RNA targeting HIC1, granulocytic differentiation was altered as assessed by CD11b expression. Bisulphite sequencing of GC-rich regions (CpG islands) in the HIC1 promoter provided evidence that the observed suppression in HL-60 cells was not because of promoter hypermethylation. Our findings indicate a role for the tumour suppressor gene HIC1 in granulocytic differentiation. Low expression of HIC1 may very well contribute to pathogenic events in leukaemogenesis.