Evaluation of the efficacy of MST-312, as a telomerase inhibitor, in the treatment of patients with multiple myeloma after stem cell transplantation

High-dose chemotherapy and stem cell transplantation are the best treatment options in patients with multiple myeloma. Numerous medicines have been studied as a maintenance treatment after transplantation. Still, the use of medications that, in addition to their maintenance properties, eliminate or delay relapse of the disease has always been researchers' purpose. Therefore, this study was performed to evaluate the efficacy of MST-312 after stem cell transplantation in patients with multiple myeloma. For this purpose, 73 patients with multiple myeloma after stem cell transplantation were studied. Thirty-five patients were in the case group, and 37 patients were in the control group. The case group was treated with 100 mg/day MST-312. Stem cell survival was evaluated in the two groups. Also, the expression of TNFα and IL-6 genes were evaluated by the Real-time PCR technique. The results showed no significant difference between the two groups in terms of stem cell survival in the first year (P=0.72) and second years of treatment (P=0.66). But there was a significant difference between the two groups regarding progression-free survival (PFS) in the first year (P=0.041) and the second year (P=0.029). These results indicate that MST-312 inhibits the progress of the disease by inhibiting the telomerase activity of myeloma cells. Genetic evaluations also showed that IL-6 and TNF-α genes were significantly reduced in the case group. Therefore, it could be suggested that MST-312 has a selective inhibitory effect on myeloma cell growth and can be indicated as a suitable candidate for treating multiple myeloma.

PTBP1/HNRNP I controls intestinal epithelial cell regeneration by maintaining stem cell survival and stemness

Properly controlled intestinal epithelial cell regeneration is not only vital for protection against insults from environmental hazards but also crucial for preventing intestinal cancer. Intestinal stem cells located in the crypt region provide the driving force for epithelial regeneration, and thus their survival and death must be precisely regulated. We show here that polypyrimidine tract binding protein 1 (PTBP1, also called heterogeneous nuclear ribonucleoprotein I, or HNRNP I), an RNA-binding protein that post-transcriptionally regulates gene expression, is critical for intestinal stem cell survival and stemness. Mechanistically, we show that PTBP1 inhibits the expression of PHLDA3, an AKT repressor, and thereby maintains AKT activity in the intestinal stem cell compartment to promote stem cell survival and proliferation. Furthermore, we show that PTBP1 inhibits the expression of PTBP2, a paralog of PTBP1 that is known to induce neuron differentiation, through repressing inclusion of alternative exon 10 to Ptbp2 transcript. Loss of PTBP1 results in a significant upregulation of PTBP2, which is accompanied by splicing changes in genes that are important for neuron cell development. This finding suggests that PTBP1 prevents aberrant differentiation of intestinal stem cells into neuronal cells through inhibiting PTBP2. Our results thus reveal a novel mechanism whereby PTBP1 maintains intestinal stem cell survival and stemness through the control of gene function post-transcriptionally.

Endothelial cell signature in muscle stem cells showed by VEGFA-FLT1-AKT1 axis for muscle stem cell survival

Endothelial and skeletal muscle lineages arise from common embryonic progenitors. Despite their shared developmental origin, adult endothelial cells (ECs) and muscle stem cells (MuSCs) (satellite cells) have been thought to possess distinct gene signatures and signaling pathways. Here we shift this paradigm by uncovering how adult MuSC behavior is affected by the expression of a subset of EC transcripts. We used several computational analyses including single-cell RNAseq to show that MuSCs express low levels of canonical EC markers. We demonstrate that MuSC survival is regulated by one such prototypic endothelial signaling pathway (VEGFA-FLT1). Using pharmacological and genetic gain- and loss-of-function studies, we identify the FLT1-AKT1 axis as the key effector underlying VEGFA-mediated regulation of MuSC survival. All together, our data support that the VEGFA-FLT1-AKT1 pathway promotes MuSC survival during muscle regeneration, and highlights how the minor expression of select transcripts is sufficient for affecting cell behavior.

An insight into the cancer stem cell survival pathways involved in chemoresistance in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most complex, aggressive and fatal subtype of breast cancer. Owing to the lack of targeted therapy and heterogenic nature of TNBC, chemotherapy remains the sole treatment option for TNBC, with taxanes and anthracyclines representing the general chemotherapeutic regimen in TNBC therapy. But unfortunately, patients develop resistance to the existing chemotherapeutic regimen, resulting in approximately 90% treatment failure. Breast cancer stem cells (BCSCs) are one of the major causes for the development of chemoresistance in TNBC patients. After surviving the chemotherapy damage, the presence of BCSCs results in relapse and recurrence of TNBC. Several pathways are known to regulate BCSCs’ survival, such as the Wnt/β-catenin, Hedgehog, JAK/STAT and HIPPO pathways. Therefore it is imperative to target these pathways in the context of eliminating chemoresistance. In this review we will discuss the novel strategies and various preclinical and clinical studies to give an insight into overcoming TNBC chemoresistance. We present a detailed account of recent studies carried out that open an exciting perspective in relation to the mechanisms of chemoresistance.

TAF8 regions important for TFIID lobe B assembly, or for TAF2 interactions, are required for embryonic stem cell survival

The human general transcription factor TFIID is composed of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs). In eukaryotic cells, TFIID is thought to nucleate RNA polymerase II (Pol II) preinitiation complex formation on all protein coding gene promoters and thus, be crucial for Pol II transcription. TFIID is composed of three lobes, named A, B and C. Structural studies showed that TAF8 forms a histone fold pair with TAF10 in lobe B and participates in connecting lobe B to lobe C. In the present study, we have investigated the requirement of the different regions of TAF8 for in vitro TFIID assembly, and the importance of certain TAF8 regions for mouse embryonic stem cell (ESC) viability. We have identified a TAF8 region, different from the histone fold domain of TAF8, important for assembling with the 5TAF core complex in lobe B, and four regions of TAF8 each individually required for interacting with TAF2 in lobe C. Moreover, we show that the 5TAF core-interacting TAF8 domain, and the proline rich domain of TAF8 that interacts with TAF2, are both required for mouse embryonic stem cell survival. Thus, our study demonstrates that distinct TAF8 regions involved in connecting lobe B to lobe C are crucial for TFIID function and consequent ESC survival.

Magnetic iron oxide nanoparticles have potential on gene therapy effectiveness and biocompatibility

Recent breakthroughs in employing magnetic iron oxide nanoparticles (IONPs) to improve gene transmission to stem cells are outlined in this study, which highlights IONPs' unique properties as biocompatible metal-based gene delivery vectors. The physicochemical characteristics of IONPs, as discussed in this study, have a major effect on gene transmission effectiveness and biocompatibility with stem cells. Regulated syntheses of homogeneous IONPs are preferable for successful, reproducible gene delivery. In addition, synthesizing or assembling IONPs with higher ARs can boost cell absorption, enhancing the effectiveness of gene transmission to stem cells. In addition, magnetofection technology has a substantial influence on stem cell gene transmission. An unoptimized transfection approach resulted in severe cytotoxicity and a significant reduction in levels of gene expression. Gene delivery using IONPs and external magnetic force, on the other hand, has demonstrated excellent results in overcoming serum interference and boosting target gene transmission to 3D cell cultures. Notably, serum-resistant and 3D gene transfer are beneficial for maintaining stem cell survival and stem after magnetofection.However, considerable challenges remain in the way IONP-assisted gene trafficking to stem cells, including the unknown bioeffects of IONPs on stem cell behavior and the large-scale fabrication of controlled size and shape monodispersed IONPs. Used at appropriate concentrations for gene delivery, IONPs exhibit no deleterious influence on stem cell survival, proliferation, and differentiation capacity. However, the dose-dependent toxicity of IONPs and the potential hazards associated with using transfection agents such as PEI require extra attention. Moreover, the potential bio-influences of IONPs and ionized ions on stem cell biological behaviors should be thoroughly examined and studies of new undiscovered bio-effects should continue. Meanwhile, another issue worth addressing for the real use of IONPs as a powerful and omnipresent platform tool to transport target genes to stem cells for medicinal reasons is the large-scale synthesis of homogeneous IONPs with low interbatch variations. IONPs have shown their extraordinary ability to increase the effectiveness of gene transport to stem cells, making them superior to other gene delivery techniques in terms of multifunctional stem cell engineering, paired with their high biocompatibility and promising functionality. However, the challenges of using IONPs to deliver genes to stem cells involve chemistry, physics, material science, pharmaceutics, and cell biology and require more multidisciplinary collaborations to achieve breakthroughs and translate this promising stem cell gene delivery strategy into medical practice.

The Transcriptional Repressor Orphan Nuclear Receptor TLX Is Responsive to Caffeine and Istradefylline

The orphan nuclear receptor TLX is expressed almost exclusively in neural stem cells. TLX acts as an essential factor for neural stem cell survival and is hence considered as a promising drug target in neurodegeneration. However, few studies have characterized the roles of TLX due to a lack of ligands and limited functional understanding. Here, we identify caffeine and istradefylline as TLX ligands that counteract the receptor’s intrinsic repressor activity in reporter gene assays and modulate TLX regulated SIRT1 and p21 expression. Mutagenesis of residues lining a cavity within the TLX ligand binding domain altered activity of these ligands suggesting direct interactions with helix 5. Using istradefylline as a tool compound, we observed ligand-sensitive recruitment of the co-repressor SMRT and heterodimerization of TLX with RXR. Both protein-protein complexes evolve as factors that modulate TLX function and suggest an unprecedented role of TLX in directly repressing other nuclear receptors.