👤 Roma Kaul

Evidence shows that the anticancer effects of microtubule targeting agents are not due solely to their antimitotic activities but also their ability to impair microtubule-dependent oncogenic signalling. The effects of microtubule targeting agents on regulators of TGF-β-induced epithelial-to-mesenchymal transition (EMT) were evaluated in breast cancer cell lines using high content imaging, gene and protein expression, siRNA-mediated knockdown and chromatin immunoprecipitation. Microtubule targeting agents rapidly and differentially alter the expression of Snail and Slug, key EMT-promoting transcription factors in breast cancer. Eribulin, vinorelbine and in some cases, ixabepalone, but not paclitaxel, inhibited TGF-β-mediated Snail expression by impairing the microtubule-dependent nuclear localisation of Smad2/3. In contrast, eribulin and vinorelbine promoted a TGF-β-independent increase in Slug in cells with low Smad4. Mechanistically, microtubule depolymerisation induces c-Jun, which consequently increases Slug expression in cells with low Smad4. These results identify a mechanism by which eribulin-mediated microtubule disruption could reverse EMT in preclinical models and in patients. Furthermore, high Smad4 levels could serve as a biomarker of this response. This study highlights that microtubule targeting drugs can exert distinct effects on the expression of EMT-regulating transcription factors and that identifying differences among these drugs could lead to their more rational use. Show less

Genome editing has potential for the targeted correction of germline mutations. Here we describe the correction of the heterozygous MYBPC3 mutation in human preimplantation embryos with precise CRISPR-Cas9-based targeting accuracy and high homology-directed repair efficiency by activating an endogenous, germline-specific DNA repair response. Induced double-strand breaks (DSBs) at the mutant paternal allele were predominantly repaired using the homologous wild-type maternal gene instead of a synthetic DNA template. By modulating the cell cycle stage at which the DSB was induced, we were able to avoid mosaicism in cleaving embryos and achieve a high yield of homozygous embryos carrying the wild-type MYBPC3 gene without evidence of off-target mutations. The efficiency, accuracy and safety of the approach presented suggest that it has potential to be used for the correction of heritable mutations in human embryos by complementing preimplantation genetic diagnosis. However, much remains to be considered before clinical applications, including the reproducibility of the technique with other heterozygous mutations. Show less

Recent studies have revealed critical roles that nuclear receptors like LXR-α (Liver X Receptor- alpha) plays as a class of post-transcriptional gene regulator in skin development and diseases. Keeping in view the fact that LXR-α plays crucial role in keratinocyte proliferation and differentiation, it becomes imperative to dissect the pathways and role of LXR-α genomics in the pathogenesis of psoriasis with ultimate aim to explore novel preventive/therapeutic strategies as treatment options. To explore the effects of agonists and activators of LXR-α on its own gene expression and the putative targets in psoriatic keratinocytes. Identification of promoter sequences for (vitamin D receptor) VDR and Catalase were done using in silico analysis followed by β-galactosidase (β-gal) reporter plasmid assay in keratinocytes from clinically heathy subjects. Determination of relative levels of LXR-α,VDR and catalase in control versus treated cells upon activation of LXR-α with Atorvastatin + 22R hydroxycholestrol and Ascorbic acid + 22R hydroxycholestrol was done by PCR and Cell Proliferation Assay. The cells transfected with the reporter plasmid element for VDR and catalase showed more than 5 and 4 fold increase respectively in the β-gal activity compared to the control. An increase of 55% in LXR-α gene expression at RNA level was observed in Atorvastatin + 22-R hydroxycholestrol compared to 24% in Ascorbic acid + 22-ROH cholesterol. The expression of the VDR and Catalase was significantly increased in both treated keratinocytes compared to its normal counterpart. Show less

In recent times, the role of LXRs in skin physiology and pathology has evolved rapidly because of their role in proliferation, carcinogenesis, differentiation and permeability barrier function. LXRs were identified as promising drug targets for the treatment of many skin diseases. For this study, skin biopsies were taken from 15 patients with vitiligo and six controls to culture melanocytes from clinically active perilesional and normal skin. Gene expression was examined by reverse transcriptase-polymerase chain reaction analysis. Role of LXR-α in regulating the expression of MMPs was checked by gene knock-down, and its role in vitiligo pathogenesis was checked by treatment with LXR-α agonist 22(R)-hydroxycholesterol. After treatment adhesion assay, annexin V staining and proliferation assay were performed. The expression of LXR-α was relatively more in perilesional skin melanocytes as compared to uninvolved skin melanocytes of non-segmental vitiligo patient, and controls on the other hand, perilesional melanocytes were more prone to apoptosis. LXR-α gene knock-down significantly increases the expression of MMPs. LXR-α agonist 22(R)-hydroxycholesterol treatment significantly decreases melanocyte adhesion, apoptosis and proliferation. Higher expression of LXR-α in perilesional skin melanocytes significantly decreases the adhesion, proliferation and matrix metalloproteinases and increases apoptosis. Show less

An accumulation of data from in vitro to in vivo model system has established a pivotal role of three crucial ligand activated nuclear receptors RXR, LXR-alpha and VDR for their ability to regulate an array of genes involved in regulation of fundamental cellular processes to patho-physiological situations. Keeping in view RXR as a common heterodimeric partner for LXR-alpha and VDR, the present study was designed to dissect the interrelationship between these three nuclear receptors in peripheral blood mononuclear cellular model. The present study revealed that all the three nuclear receptors displayed auto regulation in response to their specific ligands; Both LXR-alpha and VDR regulated the expression of their heterodimeric partner RXR; and VDR was regulated by LXR-alpha through its ability to modulate SREBP response element present in the promoter region of VDR gene. Based on these findings, the role of these nuclear receptors could be better understood in various nuclear receptor mediated pathological processes. Show less

There exists a general recognition of the fact that LXR-α, being a member of the nuclear receptor family, plays a crucial role in the biological process that connects inflammation, cholesterol homeostasis, and cellular decisions. In this context the present study was addressed to understand the role of LXR-α gene in the selective and specific reprogramming of cancer cells into a state of apoptosis leaving the normal cells unaffected. The results of this study revealed that LXR-α gene when activated in cancerous cells of diverse origin results in the regulation of genes coding for Bcl-2, AATF, and Par-4 in a fashion, forcing these cells to enter into the state of apoptosis leaving the normal cells unaffected. On the basis of this study we propose that in near future LXR-α agonist (Withaferin A) may definitely find its use in the therapeutic interventions directed towards the treatment of cancer. Show less

Keeping in view the fact that the most pathognomonic feature of Alzheimer's disease is the abnormal processing of neuronal cell membrane amyloid precursor protein accompanied by significantly elevated human serum and CSF levels of 24-hydroxycholesterol recognised widely as the specific endogenous ligand of Liver X receptor (LXR-α), the present study was addressed to explore the epigenomic-pathway (if any) that connects LXR-α activation with the genes recognised to be involved in the regulation of aberrant Abeta production leading to the generation of toxic and inflammatory mediators responsible for neuronal death. The results of such a study revealed that LXR-α activation by its specific endogenous or exogenous ligands within neuroblastoma cells resulted in the over-expression of PAR-4 gene accompanied by suppression of AATF gene through its inherent capacity to regulate genes coding for SREBP and NF-κB. Over-expression of PAR-4 gene was accompanied by aberrant Abeta production followed by ROS generation and subsequent death of neuroblastoma cells used in the present study as a cellular model for neurons. Further based upon these results, it was proposed that Abeta-induced heme oxygenase-1 can ensure cholesterol-oxidation to provide endogenous ligands for the sustained activation of neuronal LXR-α dependent epigenomic-pathway leading to neuronal death observed in Alzheimer's disease. Show less

Liver X receptor-alpha (LXR-alpha), being a member of the nuclear receptor/transcription factor family, has been widely recognized to have a pleiotropic effect in the regulation of genes involved in innate immunity, inflammation and cholesterol homeostasis. Keeping in view the fact that psoriasis is a chronic, inflammatory and autoimmune disease with a high turnover of keratinocytes, this study was addressed to understand the functional RNomics of the LXR-alpha gene in cultured primary keratinocytes derived from skin biopsies of human psoriatic lesions, and from symptomless skin of psoriatic patients and clinically healthy subjects. The results of this study revealed for the first time that the LXR-alpha gene has an inherent capacity to regulate genes coding for inflammatory cytokines, cell cycle, immunomodulation and reactive oxygen species scavenging within human keratinocytes. Moreover, LXR-alpha gene knockdown within normal human keratinocytes simulated the genomic profile observed in psoriatic skin lesions. On the basis of our study, we propose that restoration of LXR-alpha expression/function within a psoriatic lesion may help to switch the transition from psoriatic to symptomless skin. Show less

Vitiligo is a common, non-contagious disorder. The basic pathogenesis of vitiligo generally, or for any of the putative subsets of vitiligo, remains unknown. The liver X receptors (LXRs), LXR-alpha and LXR-beta are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Important genes involved in regulation of melanocytes are target genes of LXRs; it can be speculated that LXRs might be playing an important role in pathogenesis of pigmentary disorders. We have demonstrated in this study that there is expression of LXR-alpha/beta by human melanocytes at both transcriptional and translational levels. Our present data also revealed that the expression of LXR-alpha at both mRNA and protein level was significantly higher in perilesional skin as compared to the normal skin of vitiligo patient. Show less

Recent studies on the liver X receptor-alpha (LXR-alpha) have recognized its crucial protective role in the initiation of a cross-talk between lipid metabolism and inflammation regarded as a prerequisite for the development of atherosclerotic lesions. The present study was directed to explore the functional genomics of LXR-alpha gene within blood mononuclear cells of subjects suffering from coronary heart disease (CHD), revealed a paradoxical relationship between blood cellular LXR-alpha mRNA expression and the severity of coronary occlusion. In order to resolve this apparent paradox, the ligand binding domain of LXR-alpha gene was analyzed. The results of such a study revealed that three critical mutations in the domain comprising of amino acids Asp324, Pro327 and Arg328, were responsible for inability of this domain to interact with its natural ligands leading thereby to deregulation of its effector genes that are known to play crucial role in the cross-talk between lipid peroxidation and inflammation. This phenomenon was in conformity with functional assay of LXR-alpha dependent transcriptional activity within cells derived from normal and CHD subjects. Based upon these results we propose that the mutations in the LXR-alpha gene reported here for the first time not only may be exploited for the diagnosis of CHD in human subjects but also could be used as a marker for exploring the predisposition of human subjects towards CHD. Show less