Kinome screening for regulators of the estrogen receptor identifies LMTK3 as a new therapeutic target in breast cancer

LMTK3 regulation of EV biogenesis and cargo sorting promotes tumour growth by reducing monocyte infiltration and driving pro-tumourigenic macrophage polarisation in breast cancer

BACKGROUND

Lemur Tail Kinase 3 (LMTK3) promotes cell proliferation, invasiveness and therapy resistance, and its expression correlates with poor survival in several different malignancies, including breast cancer. Crosstalk through extracellular vesicles (EVs) is an increasingly appreciated mechanism of cell communication within the tumour immune microenvironment, which contributes to different aspects of cancer progression and plays a pivotal role in shaping tumour fate.

METHODS

Nanoparticle tracking analysis and transmission electron microscopy were used to study the effects of LMTK3 on EV size, while single particle interferometry allowed us to examine LMTK3-dependent effects on the subpopulation distribution of EVs. Quantitative mass spectrometry was used to profile LMTK3-dependent proteomics changes in breast cancer-derived EVs. Bioinformatics analysis of clinical data along with in vitro and cell-based assays were implemented to explore the effects of LMTK3-dependent EV protein cargo on the tumour immune microenvironment. To elucidate the mechanism through which LMTK3 impacts endosomal trafficking and regulates EV biogenesis, we used a variety of approaches, including in vitro kinase assays, confocal and electron microscopy, as well as in vivo subcutaneous and orthotopic breast cancer mouse models.

RESULTS

Here, we report that LMTK3 increases the average size of EVs, modulates immunoregulatory EV proteomic cargo and alters the subpopulation distribution of EVs released by breast cancer cells. Mechanistically, we provide evidence that LMTK3 phosphorylates Rab7, a key regulator of multivesicular body (MVB) trafficking, thereby reducing the fusion of MVBs with lysosomes and subsequent degradation of intralumenal vesicles, resulting in altered EV release. Moreover, LMTK3 causes increased packaging of phosphoserine aminotransferase 1 (PSAT1) in EVs, leading to a paracrine upregulation of phosphoglycerate dehydrogenase (PHGDH) in monocytes when these EVs are taken up. PSAT1 and PHGDH play key roles in the serine biosynthesis pathway, which is closely linked to cancer progression and regulation of monocyte behaviour. LMTK3 EV-induced elevated PHGDH expression in monocytes reduces their infiltration into breast cancer 3D spheroids and in vivo breast cancer mouse models. Furthermore, these infiltrating monocytes preferentially differentiate into pro-tumourigenic M2-like macrophages. Additional breast cancer mouse studies highlight the contribution of LMTK3-dependent EVs in the observed immunosuppressive macrophage phenotype. Finally, in vitro experiments show that pharmacological inhibition of LMTK3 reverses the pro-tumourigenic and immunomodulatory effects mediated by EVs derived from LMTK3 overexpressing cells.

CONCLUSION

Overall, this study advances our knowledge on the mechanisms of EV biogenesis and highlights a novel oncogenic role of LMTK3 in the breast TME, further supporting it as a target for cancer therapy.

The lemur tail kinase family in neuronal function and disfunction in neurodegenerative diseases

The complex neuronal architecture and the long distance of synapses from the cell body require precisely orchestrated axonal and dendritic transport processes to support key neuronal functions including synaptic signalling, learning and memory formation. Protein phosphorylation is a major regulator of both intracellular transport and synaptic functions. Some kinases and phosphatases such as cyclin dependent kinase-5 (cdk5)/p35, glycogen synthase kinase-3β (GSK3β) and protein phosphatase-1 (PP1) are strongly involved in these processes. A primary pathological hallmark of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis/frontotemporal dementia, is synaptic degeneration together with disrupted intracellular transport. One attractive possibility is that alterations to key kinases and phosphatases may underlie both synaptic and axonal transport damages. The brain enriched lemur tail kinases (LMTKs, formerly known as lemur tyrosine kinases) are involved in intracellular transport and synaptic functions, and are also centrally placed in cdk5/p35, GSK3β and PP1 signalling pathways. Loss of LMTKs is documented in major neurodegenerative diseases and thus can contribute to pathological defects in these disorders. However, whilst function of their signalling partners became clearer in modulating both synaptic signalling and axonal transport progress has only recently been made around LMTKs. In this review, we describe this progress with a special focus on intracellular transport, synaptic functions and neurodegenerative diseases.

Transcriptomic analysis of the 12 major human breast cell types reveals mechanisms of cell and tissue function

A fundamental question in biology, central to our understanding of cancer and other pathologies, is determining how different cell types coordinate to form and maintain tissues. Recognizing the distinct features and capabilities of the cells that compose these tissues is critical. Unfortunately, the complexity of tissues often hinders our ability to distinguish between neighboring cell types and, in turn, scrutinize their transcriptomes and generate reliable and tractable cell models for studying their inherently different biologies. We have recently introduced a novel method that permits the identification and purification of the 12 cell types that compose the human breast-nearly all of which could be reliably propagated in the laboratory. Here, we explore the nature of these cell types. We sequence mRNAs from each purified population and investigate transcriptional patterns that reveal their distinguishing features. We describe the differentially expressed genes and enriched biological pathways that capture the essence of each cell type, and we highlight transcripts that display intriguing expression patterns. These data, analytic tools, and transcriptional analyses form a rich resource whose exploration provides remarkable insights into the inner workings of the cell types composing the breast, thus furthering our understanding of the rules governing normal cell and tissue function.

Lemur tail kinase 3 serves as a predictor of patient outcomes and a target for the treatment of ovarian cancer

Lemur tail kinase 3 (LMTK3) belongs to a family of tyrosine kinases that are known to correlate with tumor grade and patient survival in some cancers. Here, we validated LMTK3 as a specific target and a prognostic biomarker in ovarian cancer (OC). In samples from 204 stage I-II OC patients, immunohistochemical studies revealed a higher cytoplasmic-to-nuclear staining intensity of LMTK3, which correlated with worse overall survival (p < 0.001). Efficacy studies utilizing novel LMTK3 binding peptides (LMTK3BPs) showed that all chemosensitive and chemoresistant OC cells were killed without affecting normal cells (p < 0.005), with synergistic effects shown following cisplatin and docetaxel treatment. In an orthotopic xenograft mouse model of OC, we saw a 35% tumor reduction in response to intravenous injections of 2 mg/kg LMTK3BP given three times a week for 3 weeks. Furthermore, in vivo safety studies showed no signs of toxicity after LMTK3BP treatment, even at doses as high as 40 mg/kg. This study highlights LMTK3 as a predictor of patient clinical outcomes. More importantly, novel LMTK3BPs represent potential safe treatment options, either alone or in combination with therapies, for OC.

The brain-specific kinase LMTK3 regulates neuronal excitability by decreasing KCC2-dependent neuronal Cl- extrusion

LMTK3 is a brain-specific transmembrane serine/threonine protein kinase that acts as a scaffold for protein phosphatase-1 (PP1). Although LMKT3 has been identified as a risk factor for autism and epilepsy, its physiological significance is unknown. Here, we demonstrate that LMTK3 copurifies and binds to KCC2, a neuron-specific K+/Cl- transporter. KCC2 activity is essential for Cl--mediated hyperpolarizing GABAAR receptor currents, the unitary events that underpin fast synaptic inhibition. LMTK3 acts to promote the association of KCC2 with PP1 to promote the dephosphorylation of S940 within its C-terminal cytoplasmic domain, a process the diminishes KCC2 activity. Accordingly, acute inhibition of LMTK3 increases KCC2 activity dependent upon S940 and increases neuronal Cl- extrusion. Consistent with this, LMTK3 inhibition reduced intrinsic neuronal excitability and the severity of seizure-like events in vitro. Thus, LMTK3 may have profound effects on neuronal excitability as an endogenous modulator of KCC2 activity.

Chemoinformatics and machine learning techniques to identify novel inhibitors of the lemur tyrosine kinase-3 receptor involved in breast cancer

Breast cancer is still the largest cause of cancer death in women, and around 70% of primary breast cancer patients are estrogen receptor (ER)-positive, which is the most frequent kind of breast cancer. The lemur tyrosine kinase-3 (LMTK3) receptor has been linked to estrogen responsiveness in breast cancer. However, the function of LMTK3 in reaction to cytotoxic chemotherapy has yet to be studied. Breast cancer therapy research remains tricky due to a paucity of structural investigations on LMTK3. We performed structural investigations on LMTK3 using molecular docking and molecular dynamics (MD) simulations of the LMTK3 receptor in complex with the top three inhibitor molecules along with a control inhibitor. Analysis revealed the top three compounds show the best binding affinities during docking simulations. Interactive analysis of hydrogen bonds inferred hotspot residues Tyr163, Asn138, Asp133, Tyr56, Glu52, Ser132, Asp313, and Asp151. Some other residues in the 5-Å region determined strong alkyl bonds and conventional hydrogen bond linkages. Furthermore, protein dynamics analysis revealed significant modifications among the top complexes and the control system. There was a transition from a loop to a-helix conformation in the protein-top1 complex, and in contrast, in complexes top2 and top3, the formation of a stabilizing sheet in the C chain was observed, which limited significant mobility and increased complex stability. Significant structural alterations were observed in the protein-top complexes, including a shorter helix region and the creation of some loop regions in comparison to the control system. Interestingly, binding free energies, including MMGB/PBSA WaterSwap analysis estimation, reveals that the top1 complex system was more stable than other systems, especially in comparison to the control inhibitor complex system. These results suggest a the plausible mode of action for the novel inhibitors. Therefore, the current investigation contributes to understanding the mechanism of action, serving as a basis for future experimental studies.

Kinome-Wide Synthetic Lethal Screen Identifies PANK4 as a Modulator of Temozolomide Resistance in Glioblastoma

Temozolomide (TMZ) represents the cornerstone of therapy for glioblastoma (GBM). However, acquisition of resistance limits its therapeutic potential. The human kinome is an undisputable source of druggable targets, still, current knowledge remains confined to a limited fraction of it, with a multitude of under-investigated proteins yet to be characterized. Here, following a kinome-wide RNAi screen, pantothenate kinase 4 (PANK4) isuncovered as a modulator of TMZ resistance in GBM. Validation of PANK4 across various TMZ-resistant GBM cell models, patient-derived GBM cell lines, tissue samples, as well as in vivo studies, corroborates the potential translational significance of these findings. Moreover, PANK4 expression is induced during TMZ treatment, and its expression is associated with a worse clinical outcome. Furthermore, a Tandem Mass Tag (TMT)-based quantitative proteomic approach, reveals that PANK4 abrogation leads to a significant downregulation of a host of proteins with central roles in cellular detoxification and cellular response to oxidative stress. More specifically, as cells undergo genotoxic stress during TMZ exposure, PANK4 depletion represents a crucial event that can lead to accumulation of intracellular reactive oxygen species (ROS) and subsequent cell death. Collectively, a previously unreported role for PANK4 in mediating therapeutic resistance to TMZ in GBM is unveiled.

Innovative strategies for measuring kinase activity to accelerate the next wave of novel kinase inhibitors

The development of protein kinase inhibitors (PKIs) has gained significance owing to their therapeutic potential for diseases like cancer. In addition, there has been a rise in refining kinase activity assays, each possessing unique biological and analytical characteristics crucial for PKI development. However, the PKI development pipeline experiences high attrition rates and approved PKIs exhibit unexploited potential because of variable patient responses. Enhancing PKI development efficiency involves addressing challenges related to understanding the PKI mechanism of action and employing biomarkers for precision medicine. Selecting appropriate kinase activity assays for these challenges can overcome these attrition rate issues. This review delves into the current obstacles in kinase inhibitor development and elucidates kinase activity assays that can provide solutions.

KIT mutations and expression: current knowledge and new insights for overcoming IM resistance in GIST

Gastrointestinal stromal tumor (GIST) is the most common sarcoma located in gastrointestinal tract and derived from the interstitial cell of Cajal (ICC) lineage. Both ICC and GIST cells highly rely on KIT signal pathway. Clinically, about 80-90% of treatment-naive GIST patients harbor primary KIT mutations, and special KIT-targeted TKI, imatinib (IM) showing dramatic efficacy but resistance invariably occur, 90% of them was due to the second resistance mutations emerging within the KIT gene. Although there are multiple variants of KIT mutant which did not show complete uniform biologic characteristics, most of them have high KIT expression level. Notably, the high expression level of KIT gene is not correlated to its gene amplification. Recently, accumulating evidences strongly indicated that the gene coding, epigenetic regulation, and pre- or post- protein translation of KIT mutants in GIST were quite different from that of wild type (WT) KIT. In this review, we elucidate the biologic mechanism of KIT variants and update the underlying mechanism of the expression of KIT gene, which are exclusively regulated in GIST, providing a promising yet evidence-based therapeutic landscape and possible target for the conquer of IM resistance. Video Abstract.

A revised nomenclature for the lemur family of protein kinases

The lemur family of protein kinases has gained much interest in recent years as they are involved in a variety of cellular processes including regulation of axonal transport and endosomal trafficking, modulation of synaptic functions, memory and learning, and they are centrally placed in several intracellular signalling pathways. Numerous studies have also implicated role of the lemur kinases in the development and progression of a wide range of cancers, cystic fibrosis, and neurodegenerative diseases. However, parallel discoveries and inaccurate prediction of their kinase activity have resulted in a confusing and misleading nomenclature of these proteins. Herein, a group of international scientists with expertise in lemur family of protein kinases set forth a novel nomenclature to rectify this problem and ultimately help the scientific community by providing consistent information about these molecules.

Integrated multi-omics approach to distinct molecular characterization and classification of early-onset colorectal cancer

Incidence of early-onset colorectal cancer (EOCRC), defined by a diagnosed age under 50 years, is increasing, but its heterogeneous etiologies that differ from general CRC remain undetermined. We initially characterize the genome, epigenome, transcriptome, and proteome of tumors from 79 patients in a Chinese CRC cohort. Data for an additional 126 EOCRC subjects are obtained from the International Cancer Genome Consortium Chinese cohort and The Cancer Genome Atlas European cohort. We observe that early-onset tumors have a high tumor mutation burden; increased DNA repair features by mutational signature 3 and multi-layer pathway enrichments; strong perturbations at effects of DNA methylation and somatic copy-number alteration on gene expression; and upregulated immune infiltration as hot tumors underlying immunophenotypes. Notably, LMTK3 exhibits ancestral mutation disparity, potentially being a functional modulator and biomarker that drives molecular alterations in EOCRC development and immunotherapies. This integrative omics study provides valuable knowledge for precision oncology of CRC.

Developmental programming: Adipose depot-specific regulation of non-coding RNAs and their relation to coding RNA expression in prenatal testosterone and prenatal bisphenol-A -treated female sheep

Inappropriate developmental exposure to steroids is linked to metabolic disorders. Prenatal testosterone excess or bisphenol A (BPA, an environmental estrogen mimic) leads to insulin resistance and adipocyte disruptions in female lambs. Adipocytes are key regulators of insulin sensitivity. Metabolic tissue-specific differences in insulin sensitivity coupled with adipose depot-specific changes in key mRNAs, were previously observed with prenatal steroid exposure. We hypothesized that depot-specific changes in the non-coding RNA (ncRNA) - regulators of gene expression would account for the direction of changes seen in mRNAs. Non-coding RNA (lncRNA, miRNA, snoRNA, snRNA) from various adipose depots of prenatal testosterone and BPA-treated animals were sequenced. Adipose depot-specific changes in the ncRNA that are consistent with the depot-specific mRNA expression in terms of directionality of changes and functional implications in insulin resistance, adipocyte differentiation and cardiac hypertrophy were found. Importantly, the adipose depot-specific ncRNA changes were model-specific and mutually exclusive, suggestive of different regulatory entry points in this regulation.

Optimal modeling of anti-breast cancer candidate drugs screening based on multi-model ensemble learning with imbalanced data

The imbalanced data makes the machine learning model seriously biased, which leads to false positive in screening of therapeutic drugs for breast cancer. In order to deal with this problem, a multi-model ensemble framework based on tree-model, linear model and deep-learning model is proposed. Based on the methodology constructed in this study, we screened the 20 most critical molecular descriptors from 729 molecular descriptors of 1974 anti-breast cancer drug candidates and, in order to measure the pharmacokinetic properties and safety of the drug candidates, the screened molecular descriptors were used in this study for subsequent bioactivity, absorption, distribution metabolism, excretion, toxicity, and other prediction tasks. The results show that the method constructed in this study is superior and more stable than the individual models used in the ensemble approach.

The Inhibitory Properties of a Novel, Selective LMTK3 Kinase Inhibitor

Recently, the oncogenic role of lemur tyrosine kinase 3 (LMTK3) has been well established in different tumor types, highlighting it as a viable therapeutic target. In the present study, using in vitro and cell-based assays coupled with biophysical analyses, we identify a highly selective small molecule LMTK3 inhibitor, namely C36. Biochemical/biophysical and cellular studies revealed that C36 displays a high in vitro selectivity profile and provides notable therapeutic effect when tested in the National Cancer Institute (NCI)-60 cancer cell line panel. We also report the binding affinity between LMTK3 and C36 as demonstrated via microscale thermophoresis (MST). In addition, C36 exhibits a mixed-type inhibition against LMTK3, consistent with the inhibitor overlapping with both the adenosine 5'-triphosphate (ATP)- and substrate-binding sites. Treatment of different breast cancer cell lines with C36 led to decreased proliferation and increased apoptosis, further reinforcing the prospective value of LMTK3 inhibitors for cancer therapy.

The Rattlesnake W Chromosome: A GC-Rich Retroelement Refugium with Retained Gene Function Across Ancient Evolutionary Strata

Sex chromosomes diverge after the establishment of recombination suppression, resulting in differential sex-linkage of genes involved in genetic sex determination and dimorphic traits. This process produces systems of male or female heterogamety wherein the Y and W chromosomes are only present in one sex and are often highly degenerated. Sex-limited Y and W chromosomes contain valuable information about the evolutionary transition from autosomes to sex chromosomes, yet detailed characterizations of the structure, composition, and gene content of sex-limited chromosomes are lacking for many species. In this study, we characterize the female-specific W chromosome of the prairie rattlesnake (Crotalus viridis) and evaluate how recombination suppression and other processes have shaped sex chromosome evolution in ZW snakes. Our analyses indicate that the rattlesnake W chromosome is over 80% repetitive and that an abundance of GC-rich mdg4 elements has driven an overall high degree of GC-richness despite a lack of recombination. The W chromosome is also highly enriched for repeat sequences derived from endogenous retroviruses and likely acts as a "refugium" for these and other retroelements. We annotated 219 putatively functional W-linked genes across at least two evolutionary strata identified based on estimates of sequence divergence between Z and W gametologs. The youngest of these strata is relatively gene-rich, however gene expression across strata suggests retained gene function amidst a greater degree of degeneration following ancient recombination suppression. Functional annotation of W-linked genes indicates a specialization of the W chromosome for reproductive and developmental function since recombination suppression from the Z chromosome.

Decoding the Therapeutic Implications of the ERα Stability and Subcellular Distribution in Breast Cancer

Approximately 70% of all breast cancer cases are estrogen receptor-alpha positive (ERα+) and any ERα signaling pathways deregulation is critical for the progression of malignant mammary neoplasia. ERα acts as a transcription factor that promotes the expression of estrogen target genes associated with pro-tumor activity in breast cancer cells. Furthermore, ERα is also part of extranuclear signaling pathways related to endocrine resistance. The regulation of ERα subcellular distribution and protein stability is critical to regulate its functions and, consequently, influence the response to endocrine therapies and progression of this pathology. This minireview highlights studies that have deciphered the molecular mechanisms implicated in controlling ERα stability and nucleo-cytoplasmic transport. These mechanisms offer information about novel biomarkers, therapeutic targets, and promising strategies for breast cancer treatment.

Anastrozole Regulates Fatty Acid Synthase in Breast Cancer

Our previous matched case-control study of postmenopausal women with resected early-stage breast cancer revealed that only anastrozole, but not exemestane or letrozole, showed a significant association between the 6-month estrogen concentrations and risk of breast cancer. Anastrozole, but not exemestane or letrozole, is a ligand for estrogen receptor α. The mechanisms of endocrine resistance are heterogenous and with the new mechanism of anastrozole, we have found that treatment of anastrozole maintains fatty acid synthase (FASN) protein level by limiting the ubiquitin-mediated FASN degradation, leading to increased breast cancer cell growth. Mechanistically, anastrozole decreases the guided entry of tail-anchored proteins factor 4 (GET4) expression, resulting in decreased BCL2-associated athanogene cochaperone 6 (BAG6) complex activity, which in turn, prevents RNF126-mediated degradation of FASN. Increased FASN protein level can induce a negative feedback loop mediated by the MAPK pathway. High levels of FASN are associated with poor outcome only in patients with anastrozole-treated breast cancer, but not in patients treated with exemestane or letrozole. Repressing FASN causes regression of breast cancer cell growth. The anastrozole-FASN signaling pathway is eminently targetable in endocrine-resistant breast cancer.

Association between the rs3802201 polymorphism of the lncRNA MIR2052HG gene and the risk of recurrent miscarriage in a Southern Chinese population

BACKGROUND

Plenty of studies have indicated that some genetic polymorphisms of the breast cancer which associated with its susceptibility may also be related to the susceptibility of abortion. MIR2052HG plays an important role in the onset and progression of breast cancer by maintaining the level of ERα, but to the best of our knowledge, the correlation between risk of recurrent abortion and MIR2052HG rs3802201 C>G polymorphism is still unclear. Therefore, we conducted this case-control study to investigate whether MIR2052HG rs3802201 C>G polymorphism is associated with susceptibility of recurrent miscarriage (RM).

METHODS

We recruited 392 healthy controls and 248 patients with RM to process this research, the participants were all from southern China, and genotyping was performed by TaqMan method.

RESULTS

Our results showed that there was no evidence indicates the MIR2052HG rs3802201 C>G is related to RM (CG and CC: adjusted OR = 0.970, 95% CI = 0.694-1.355, p = 0.8577; GG and CC: adjusted OR = 0.743, 95% CI = 0.416-1.330, p = 0.3174; dominant model: adjusted OR = 0.925, 95% CI = 0.672-1.272, p = 0.6298; recessive model: adjusted OR = 0.751, 95% CI = 0.430-1.321, p = 0.3233).

CONCLUSION

We verified that the MIR2052HG rs3802201 C>G allele might be uncorrelated to the RM risk, but these findings require further validation in multicenter studies with larger sample size and different ethnicities.

Knockdown of LMTK3 in the Endometrioid Adenocarcinoma Cell Line Ishikawa: Inhibition of Growth and Estrogen Receptor α

Objective

The curative effect of high-efficiency progesterone and other therapeutic drugs for endometrioid adenocarcinoma patients with preservation of reproductive capacity has not been satisfactory so far. Novel therapeutic drugs need to be explored.

Methods

We investigated the cytoplastic and nuclear expression levels of LMTK3 between endometrioid adenocarcinoma tissues and adjacent endometrial tissues by immunohistochemistry. We detected the effects of LMTK3 on cell viability of Ishikawa cells by CCK-8. We detected the effects of LMTK3 on cell cycle and apoptosis of Ishikawa cells by flow cytometry. We also detected the effects of LMTK3 knockdown on mRNA and protein levels of ERα by qRT-PCR and western blotting, respectively. We also used the cBioPortal online database to analyze the coexpression of LMTK3 and ESR1 in 1647 UCEC samples.

Results

We used TMAs to identify that LMTK3 was mainly detected in the cytoplasm of endometrioid tissues, and cytoplasmic LMTK3 expression in endometrioid tissues was higher than that in adjacent endometrial tissues (P < 0.05). LMTK3 knockdown decreased the proliferation of Ishikawa cells through decreasing cell viability (P < 0.01), increasing G1 (P < 0.001) arrest, and promoting apoptosis (P < 0.01). There was a positive correlation between the mRNA expression levels of LMTK3 and ESR1 (Spearman: P=2.011e-5, R=0.13; Pearson: P=7.18e-8, R=0.17). Knockdown of LMTK3 also reduced the mRNA (P < 0.001) and protein (P < 0.001) levels of ERα.

Conclusions

Inhibitors of LMTK3 may be a possible future treatment for ERα and LMTK3 highly expressed endometrioid adenocarcinoma following appropriate studies.

The multifaceted role of lemur tyrosine kinase 3 in health and disease

In the last decade, LMTK3 (lemur tyrosine kinase 3) has emerged as an important player in breast cancer, contributing to the advancement of disease and the acquisition of resistance to therapy through a strikingly complex set of mechanisms. Although the knowledge of its physiological function is largely limited to receptor trafficking in neurons, there is mounting evidence that LMTK3 promotes oncogenesis in a wide variety of cancers. Recent studies have broadened our understanding of LMTK3 and demonstrated its importance in numerous signalling pathways, culminating in the identification of a potent and selective LMTK3 inhibitor. Here, we review the roles of LMTK3 in health and disease and discuss how this research may be used to develop novel therapeutics to advance cancer treatment.

Role and mechanism of autophagy-regulating factors in tumorigenesis and drug resistance

A hallmark feature of tumorigenesis is uncontrolled cell division. Autophagy is regulated by more than 30 genes and it is one of several mechanisms by which cells maintain homeostasis. Autophagy promotes cancer progression and drug resistance. Several genes play important roles in autophagy-induced tumorigenesis and drug resistance including Beclin-1, MIF, HMGB1, p53, PTEN, p62, RAC3, SRC3, NF-2, MEG3, LAPTM4B, mTOR, BRAF and c-MYC. These genes alter cell growth, cellular microenvironment and cell division. Mechanisms involved in tumorigenesis and drug resistance include microdeletions, genetic mutations, loss of heterozygosity, hypermethylation, microsatellite instability and translational modifications at a molecular level. Disrupted or altered autophagy has been reported in hematological malignancies like lymphoma, leukemia and myeloma as well as multiple solid organ tumors like colorectal, hepatocellular, gall bladder, pancreatic, gastric and cholangiocarcinoma among many other malignancies. In addition, defects in autophagy also play a role in drug resistance in cancers like osteosarcoma, ovarian and lung carcinomas following treatment with drugs such as doxorubicin, paclitaxel, cisplatin, gemcitabine and etoposide. Therapeutic approaches that modulate autophagy are a novel future direction for cancer drug development that may help to prevent issues with disease progression and overcome drug resistance.

A New Anti-Estrogen Discovery Platform Identifies FDA-Approved Imidazole Anti-Fungal Drugs as Bioactive Compounds against ERα Expressing Breast Cancer Cells

17β-estradiol (E2) exerts its physiological effects through the estrogen receptor α (i.e., ERα). The E2:ERα signaling allows the regulation of cell proliferation. Indeed, E2 sustains the progression of ERα positive (ERα+) breast cancers (BCs). The presence of ERα at the BC diagnosis drives their therapeutic treatment with the endocrine therapy (ET), which restrains BC progression. Nonetheless, many patients develop metastatic BCs (MBC) for which a treatment is not available. Consequently, the actual challenge is to complement the drugs available to fight ERα+ primary and MBC. Here we exploited a novel anti-estrogen discovery platform to identify new Food and Drug Administration (FDA)-approved drugs inhibiting E2:ERα signaling to cell proliferation in cellular models of primary and MBC cells. We report that the anti-fungal drugs clotrimazole (Clo) and fenticonazole (Fenti) induce ERα degradation and prevent ERα transcriptional signaling and proliferation in cells modeling primary and metastatic BC. The anti-proliferative effects of Clo and Fenti occur also in 3D cancer models (i.e., tumor spheroids) and in a synergic manner with the CDK4/CDK6 inhibitors palbociclib and abemaciclib. Therefore, Clo and Fenti behave as “anti-estrogens”-like drugs. Remarkably, the present “anti-estrogen” discovery platform represents a valuable method to rapidly identify bioactive compounds with anti-estrogenic activity.

Developmental programming: Adipose depot-specific transcriptional regulation by prenatal testosterone excess in a sheep model of PCOS

Prenatal testosterone (T)-treated female sheep manifest adipose depot-specific disruptions in inflammatory/oxidative state, adipocyte differentiation and thermogenic adipocyte distribution. The objective of this study was to identify common and divergent gene pathways underlying prenatal T excess-induced adipose depot-specific disruptions. RNA sequencing and network analyses were undertaken with visceral (VAT), subcutaneous (SAT), epicardiac (ECAT) and perirenal (PRAT) adipose tissues from control and prenatal T-treated (100 mg T propionate twice a week from days 30-90 of gestation) female sheep at 21 months of age. Increased expression of adiposity and inflammation-related genes in VAT and genes that promote differentiation of white adipocytes in SAT were congruous with their metabolic roles with SAT favoring uptake/storage of free fatty acids and triglycerides and VAT favoring higher rate of fatty acid turnover and lipolysis. Selective upregulation of cardiac muscle and renoprotection genes in ECAT and PRAT respectively are suggestive of protective paracrine actions. Expression profile in prenatal T-treated sheep paralleled depot-specific dysfunctions with increased proinflammatory genes in VAT, reduced adipocyte differentiation genes in VAT and SAT and increased vascular related gene expression in PRAT. The high expression of genes involved in cardiomyocyte function in ECAT is suggestive of cardioprotective function being maintained to overcome the prenatal T-induced cardiac dysfunction and hypertension. These findings coupled with changes in gene pathways and networks involved in chromatin modification, extracellular matrix, immune and mitochondrial function, and endoplasmic reticulum to Golgi transport suggest that dysregulation in gene expression underlie prenatal T-treatment induced functional differences among adipose depots and manifestation of metabolic dysfunction.

The structure-function relationship of oncogenic LMTK3

Elucidating signaling driven by lemur tyrosine kinase 3 (LMTK3) could help drug development. Here, we solve the crystal structure of LMTK3 kinase domain to 2.1Å resolution, determine its consensus motif and phosphoproteome, unveiling in vitro and in vivo LMTK3 substrates. Via high-throughput homogeneous time-resolved fluorescence screen coupled with biochemical, cellular, and biophysical assays, we identify a potent LMTK3 small-molecule inhibitor (C28). Functional and mechanistic studies reveal LMTK3 is a heat shock protein 90 (HSP90) client protein, requiring HSP90 for folding and stability, while C28 promotes proteasome-mediated degradation of LMTK3. Pharmacologic inhibition of LMTK3 decreases proliferation of cancer cell lines in the NCI-60 panel, with a concomitant increase in apoptosis in breast cancer cells, recapitulating effects of LMTK3 gene silencing. Furthermore, LMTK3 inhibition reduces growth of xenograft and transgenic breast cancer mouse models without displaying systemic toxicity at effective doses. Our data reinforce LMTK3 as a druggable target for cancer therapy.

AKT1 Polymorphism (rs10138227) and Risk of Colorectal Cancer in Moroccan Population: A Case Control Study

BACKGROUND

LMTK3 and AKT1 each have a role in carcinogenesis and tumor progression. The analysis of single nucleotide polymorphisms of AKT1 and LMTK3 could lead to more complete and accurate risk estimates for colorectal cancer.

AIM

We evaluated the association between single nucleotide polymorphisms (SNPs) of AKT1 and LMTK3 and the risk of colorectal cancer in a case-control study in Moroccan population.

METHODS

Genomic DNA from 70 colorectal cancer patients and 50 healthy control subjects was extracted from whole blood. Genotyping was performed by direct sequencing after polymerase chain reactions for the 7 SNPs (AKT1rs1130214G/T, AKT1rs10138227C/T, AKT1rs3730358C/T, AKT1rs1000559097G/A, AKT1rs2494737A/T, LMTK3rs8108419G/A, and LMTK3rs9989661A/G.). Study subjects provided detailed information during the collection. All P values come from bilateral tests.

RESULTS

In the logistic regression analysis, a significantly high risk of colorectal cancer was associated with TC/TT genotypes of rs10138227 with adjusted odds ratio [OR] equal to 2.82 and 95% confidence interval [CI] of 1.15 to 6.91.

CONCLUSION

Our results suggest that the SNP AKT1rs10138227 could affect susceptibility to CRC, probably by modulating the transcriptional activity of AKT1. However, larger independent studies are needed to validate our results.

LMTK3 promotes tumorigenesis in bladder cancer via the ERK/MAPK pathway

Lemur tyrosine kinase 3 (LMTK3) is a key member of the serine–threonine tyrosine kinase family. It plays an important role in breast cancer tumorigenesis and progression. However, its biological role in bladder cancer remains elusive. In this study, we demonstrated that LMTK3 was overexpressed in bladder cancer and was positively correlated with bladder cancer malignancy. High LMTK3 expression predicted poor overall survival. Knockdown of LMTK3 in bladder cancer cells triggered cell‐cycle arrest at G2/M phase, suppressed cell growth, and induced cell apoptosis in bladder cancer cells. Furthermore, Transwell assays revealed that reduction of LMTK3 decreased cell migration by regulating the epithelial‐to‐mesenchymal transition pathway. Conversely, LKTM3 overexpression was shown to promote proliferation and migration of bladder cancer cells. We assessed phosphorylation of MEK and ERK1/2 in bladder cancer cells depleted of LMTK3 and demonstrated a reduced phosphorylation status compared with the control group. Using an MAPK signaling‐specific inhibitor, U0126, we could rescue the promotion of proliferation and viability in LMTK3‐overexpressing cells. In conclusion, we extend the status of LMTK3 as an oncogene in bladder cancer and provide evidence for its function via the activation of the ERK/MAPK pathway. Thus, targeting LMTK3 may hold potential as a diagnostic and prognostic biomarker and as a possible future treatment for bladder cancer.

Functional genomics based on germline genome-wide association studies of endocrine therapy for breast cancer

Breast cancer is the most common invasive cancer in women worldwide. Functional follow-up of breast cancer genome-wide association studies has led to the discovery of genes that regulate endocrine therapy response in a SNP- and drug-dependent manner. Here, we will present four examples in which functional genomic studies from breast cancer clinical trials led to novel pharmacogenomic insights and molecular mechanisms of selective estrogen receptor modulators and aromatase inhibitors. The approach utilized for studying genetic variability described in this review offers substantial potential for meaningful discoveries that move the field toward precision medicine for patients.

Long Noncoding RNAs Involved in the Endocrine Therapy Resistance of Breast Cancer

Long noncoding RNAs (lncRNAs) are defined as RNAs longer than 200 nucleotides that do not encode proteins. Recent studies have demonstrated that numerous lncRNAs are expressed in humans and play key roles in the development of various types of cancers. Intriguingly, some lncRNAs have been demonstrated to be involved in endocrine therapy resistance for breast cancer through their own mechanisms, suggesting that lncRNAs could be promising new biomarkers and therapeutic targets of breast cancer. Here, we summarize the functions and mechanisms of lncRNAs related to the endocrine therapy resistance of breast cancer.

Discovery of cyclic guanidine-linked sulfonamides as inhibitors of LMTK3 kinase

Lemur tyrosine kinase 3 (LMTK3) is oncogenic in various cancers. In breast cancer, LMTK3 phosphorylates and modulates the activity of estrogen receptor-α (ERα) and is essential for the growth of ER-positive cells. LMTK3 is highly expressed in ER-negative breast cancer cells, where it promotes invasion via integrin β1. LMTK3 abundance and/or high nuclear expression have been linked to shorter disease free and overall survival time in a variety of cancers, supporting LMTK3 as a potential target for anticancer drug development. We sought to identify small molecule inhibitors of LMTK3 with the ultimate goal to pharmacologically validate this kinase as a novel target in cancer. We used a homogeneous time resolve fluorescence (HTRF) assay to screen a collection of mixture-based combinatorial chemical libraries containing over 18 million compounds. We identified several cyclic guanidine-linked sulfonamides with sub-micromolar activity and evaluated their binding mode using a 3D homology model of the LMTK3 K_D.

The Eleanor ncRNAs activate the topological domain of the ESR1 locus to balance against apoptosis

MCF7 cells acquire estrogen-independent proliferation after long-term estrogen deprivation (LTED), which recapitulates endocrine therapy resistance. LTED cells can become primed for apoptosis, but the underlying mechanism is largely unknown. We previously reported that Eleanor non-coding RNAs (ncRNAs) upregulate the ESR1 gene in LTED cells. Here, we show that Eleanors delineate the topologically associating domain (TAD) of the ESR1 locus in the active nuclear compartment of LTED cells. The TAD interacts with another transcriptionally active TAD, which is 42.9 Mb away from ESR1 and contains a gene encoding the apoptotic transcription factor FOXO3. Inhibition of a promoter-associated Eleanor suppresses all genes inside the Eleanor TAD and the long-range interaction between the two TADs, but keeps FOXO3 active to facilitate apoptosis in LTED cells. These data indicate a role of ncRNAs in chromatin domain regulation, which may underlie the apoptosis-prone nature of therapy-resistant breast cancer cells and could be good therapeutic targets.

Long term estrogen deprivation can result in apoptosis in breast cancer cells. Here, the authors show that this apoptosis is induced by the long-range chromatin interaction of loci containing the ESR1 and FOXO3 genes, resulting in FOXO3-mediated apoptosis.

Hypoxia differentially regulates estrogen receptor alpha in 2D and 3D culture formats

Hypoxia is a common feature in solid tumors. Clinical samples show a positive correlation between the expression of the hypoxia-inducible factor HIF-1α and estrogen receptor alpha (ERα) and a negative correlation between HIF-1α and hormone sensitivity. Results from monolayer cultures are in contention with clinical observations, showing that ER (+) cell lines no longer express ERα under hypoxic conditions (1% O2). Here, we compared the impact of hypoxia on the ERα signaling pathway for T47D cells in a 2D and 3D culture format. In the 2D format, the cells were cultured as monolayers. In the 3D format, paper-based scaffolds supported cells suspended in a collagen matrix. Using ELISA, Western blot, and immunofluorescence measurements, we show that hypoxia differentially regulates ERα protein levels in a culture environment-dependent manner. In the 2D format, the protein levels are significantly decreased in hypoxia. In the 3D format, the protein levels are maintained in hypoxia. Hypoxia reduced ERα transcriptional activation in both culture formats. These results highlight the importance of considering tissue dimensionality for in vitro studies. They also show that ERα protein levels in hypoxia are not an accurate indicator of ERα transcriptional activity, and confirm that a positive stain for ERα in a clinical sample may not necessarily indicate hormone sensitivity.

The lncRNA MIR2052HG regulates ERα levels and aromatase inhibitor resistance through LMTK3 by recruiting EGR1

Background

Our previous genome-wide association study using the MA.27 aromatase inhibitors adjuvant trial identified SNPs in the long noncoding RNA MIR2052HG associated with breast cancer-free interval. MIR2052HG maintained ERα both by promoting AKT/FOXO3-mediated ESR1 transcription and by limiting ubiquitin-mediated ERα degradation. Our goal was to further elucidate MIR2052HG’s mechanism of action.

Methods

RNA-binding protein immunoprecipitation assays were performed to demonstrate that the transcription factor, early growth response protein 1 (EGR1), worked together with MIR2052HG to regulate that lemur tyrosine kinase-3 (LMTK3) transcription in MCF7/AC1 and CAMA-1 cells. The location of EGR1 on the LMTK3 gene locus was mapped using chromatin immunoprecipitation assays. The co-localization of MIR2052HG RNA and the LMTK3 gene locus was determined using RNA-DNA dual fluorescent in situ hybridization. Single-nucleotide polymorphisms (SNP) effects were evaluated using a panel of human lymphoblastoid cell lines.

Results

MIR2052HG depletion in breast cancer cells results in a decrease in LMTK3 expression and cell growth. Mechanistically, MIR2052HG interacts with EGR1 and facilitates its recruitment to the LMTK3 promoter. LMTK3 sustains ERα levels by reducing protein kinase C (PKC) activity, resulting in increased ESR1 transcription mediated through AKT/FOXO3 and reduced ERα degradation mediated by the PKC/MEK/ERK/RSK1 pathway. MIR2052HG regulated LMTK3 in a SNP- and aromatase inhibitor-dependent fashion: the variant SNP increased EGR1 binding to LMTK3 promoter in response to androstenedione, relative to wild-type genotype, a pattern that can be reversed by aromatase inhibitor treatment. Finally, LMTK3 overexpression abolished the effect of MIR2052HG on PKC activity and ERα levels.

Conclusions

Our findings support a model in which the MIR2052HG regulates LMTK3 via EGR1, and LMTK3 regulates ERα stability via the PKC/MEK/ERK/RSK1 axis. These results reveal a direct role of MIR2052HG in LMTK3 regulation and raise the possibilities of targeting MIR2052HG or LMTK3 in ERα-positive breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1130-3) contains supplementary material, which is available to authorized users.

The Functions of DNA Damage Factor RNF8 in the Pathogenesis and Progression of Cancer

The really interesting new gene (RING) finger protein 8 (RNF8) is a central factor in DNA double strand break (DSB) signal transduction. DSB damage is the most toxic type of DNA damage to cells and is related to genomic instability. Multiple roles for RNF8 have been identified in DNA damage response as well as in other functions, such as telomere protection, cell cycle control and transcriptional regulation. These functions are closely correlated to tumorigenesis and cancer progression. Indeed, deficiency of RNF8 caused spontaneous tumorigenesis in a mouse model. Deciphering these mechanisms of RNF8 may shed light on strategies for cancer treatment. In this review, we summarize the current understanding of both classical and nonclassical functions of RNF8, and discuss its roles in the pathogenesis and progression of tumor.

Endocrine Resistance in Hormone Receptor Positive Breast Cancer-From Mechanism to Therapy

The importance and role of the estrogen receptor (ER) pathway has been well-documented in both breast cancer (BC) development and progression. The treatment of choice in women with metastatic breast cancer (MBC) is classically divided into a variety of endocrine therapies, 3 of the most common being: selective estrogen receptor modulators (SERM), aromatase inhibitors (AI) and selective estrogen receptor down-regulators (SERD). In a proportion of patients, resistance develops to endocrine therapy due to a sophisticated and at times redundant interference, at the molecular level between the ER and growth factor. The progression to endocrine resistance is considered to be a gradual, step-wise process. Several mechanisms have been proposed but thus far none of them can be defined as the complete explanation behind the phenomenon of endocrine resistance. Although multiple cellular, molecular and immune mechanisms have been and are being extensively studied, their individual roles are often poorly understood. In this review, we summarize current progress in our understanding of ER biology and the molecular mechanisms that predispose and determine endocrine resistance in breast cancer patients.

The LMTK-family of kinases: Emerging important players in cell physiology and pathogenesis

Lemur Tail (former tyrosine) Kinases (LMTKs) comprise a novel family of regulated serine/threonine specific kinases with three structurally and evolutionary related members. LMTKs exercise a confusing variety of cytosolic functions in cell signalling and membrane trafficking. Moreover, LMTK2 and LMTK3 also reside in the nucleus where they participate in gene transcription/regulation. As a consequence, LMTKs impact cell proliferation and apoptosis, cell growth and differentiation, as well as cell migration. All these fundamental cell behaviours can turn awry, most prominently during neuropathologies and tumour biogenesis. In cancer cells, LMTK levels are often correlated with poor overall prognosis and therapy outcome, not least owned to acquired drug resistance. In brain tissue, LMTKs are highly expressed and have been linked to neuronal and glia cell differentiation and cell homeostasis. For one member of the LMTK-family (LMTK2) a role in cystic fibrosis has been identified. Due to their role in fundamental cell processes, altered LMTK physiology may also warrant a hitherto unappreciated role in other diseases, and expose them as potential valuable drug targets. On the backdrop of a compendium of LMTK cell functions, we hypothesize that the primary role of LMTKs may dwell within the endocytic cargo recycling and/or nuclear receptor transport pathways.

Molecular screening and docking analysis of LMTK3and AKT1 combined inhibitors

The abnormal activation of AKT/mTOR signaling pathway and overexpression of LMTK3, are the main factors involved in the generation of drug resistance. Therefore, the use of computer-aided drug design in the inhibitors discovery offers an advantage to provide new candidates for the treatment of this resistance. We realised the virtual screening and molecular docking of AKT1 and LMTK3 proteins by the Dockblaster server. In addition, with abundance of candidates under development for AKT1 kinase, we have also conducted a Quantitative Structure-Activity Relationship (QSAR) study based on these compounds, in order to design more active compounds and predict their activity for development of a new inhibitor of AKT1. QSAR tests were performed for AKT1 using the Partial Least Squares method with a correlation coefficient of R2=0.8062 and a cross-validation of q2=0.6995. This test has selected five compounds as competitive inhibitors-AKT1-ATP with a better biological activities. In parallel the molecular screening has selected five other compounds as competitive ATP-inhibitors of LMTK3. One of them is a common inhibitor with AKT1, and it is marketed as a moderate to severe pain therapy. The ADME predictions confirmed the inhibitors pharmacological activity of these compounds for potential consideration as drug candidates.

LMTK3 is essential for oncogenic KIT expression in KIT-mutant GIST and melanoma

Certain cancers, including gastrointestinal stromal tumor (GIST) and subsets of melanoma, are caused by somatic KIT mutations that result in KIT receptor tyrosine kinase constitutive activity, which drives proliferation. The treatment of KIT-mutant GIST has been revolutionized with the advent of KIT-directed cancer therapies. KIT tyrosine kinase inhibitors (TKI) are superior to conventional chemotherapy in their ability to control advanced KIT-mutant disease. However, these therapies have a limited duration of activity due to drug-resistant secondary KIT mutations that arise (or that are selected for) during KIT TKI treatment. To overcome the problem of KIT TKI resistance, we sought to identify novel therapeutic targets in KIT-mutant GIST and melanoma cells using a human tyrosine kinome siRNA screen. From this screen, we identified lemur tyrosine kinase 3 (LMTK3) and herein describe its role as a novel KIT regulator in KIT-mutant GIST and melanoma cells. We find that LMTK3 regulated the translation rate of KIT, such that loss of LMTK3 reduced total KIT, and thus KIT downstream signaling in cancer cells. Silencing of LMTK3 decreased cell viability and increased cell death in KIT-dependent, but not KIT-independent GIST and melanoma cell lines. Notably, LMTK3 silencing reduced viability of all KIT-mutant cell lines tested, even those with drug-resistant KIT secondary mutations. Furthermore, targeting of LMTK3 with siRNA delayed KIT-dependent GIST growth in a xenograft model. Our data suggest the potential of LMTK3 as a target for treatment of patients with KIT-mutant cancer, particularly after failure of KIT TKIs.

Polyubiquitination inhibition of estrogen receptor alpha and its implications in breast cancer

Estrogen receptor alpha (ERα) is detected in more than 70% of the cases of breast cancer. Nuclear activity of ERα, a transcriptional regulator, is linked to the development of mammary tumors, whereas the extranuclear activity of ERα is related to endocrine therapy resistance. ERα polyubiquitination is induced by the estradiol hormone, and also by selective estrogen receptor degraders, resulting in ERα degradation via the ubiquitin proteasome system. Moreover, polyubiquitination is related to the ERα transcription cycle, and some E3-ubiquitin ligases also function as coactivators for ERα. Several studies have demonstrated that ERα polyubiquitination is inhibited by multiple mechanisms that include posttranslational modifications, interactions with coregulators, and formation of specific protein complexes with ERα. These events are responsible for an increase in ERα protein levels and deregulation of its signaling in breast cancers. Thus, ERα polyubiquitination inhibition may be a key factor in the progression of breast cancer and resistance to endocrine therapy.

Structure-Based Virtual Screening of High-Affinity ATP-Competitive Inhibitors Against Human Lemur Tyrosine Kinase-3 (LMTK3) Domain: A Novel Therapeutic Target for Breast Cancer

Human lemur tyrosine kinase-3 (LMTK3) is an oncogenic kinase known to regulate ER-α through phosphorylation and is considered to be a novel therapeutic target for breast cancer. In this work, we have studied the ATP-binding mechanism with LMTK3 domain and also carried out virtual screening on LMTK3 to identify lead compounds using Dock blaster server. The top scored compounds obtained from Dock blaster were then narrowed down further to six lead compounds (ZINC37996511, ZINC83363046, ZINC3745998, ZINC50456700, ZINC83351792 and ZINC83364581) based on high-binding affinity and non-bonding interactions with LMTK3 using Autodock 4.2 program. We found in comparison to ATP, the lead compounds bind relatively stronger to LMTK3. The relative binding free energy results from MM-PBSA/GBSA method further indicate the strong binding affinity of lead compounds over ATP to LMTK3 in the dynamic system. Further, potential of mean force (PMF) study for ATP and lead compounds with LMTK3 have been performed to explore the unbinding processes and the free energy barrier. From the PMF results, we observed that the lead compounds have higher dissociation energy barriers than the ATP. Our findings suggest that these lead compounds may compete with ATP, and could act as probable potential inhibitors for LMTK3.

LMTK3 confers chemo-resistance in breast cancer

Lemur tyrosine kinase 3 (LMTK3) is an oncogenic kinase that is involved in different types of cancer (breast, lung, gastric, colorectal) and biological processes including proliferation, invasion, migration, chromatin remodeling as well as innate and acquired endocrine resistance. However, the role of LMTK3 in response to cytotoxic chemotherapy has not been investigated thus far. Using both 2D and 3D tissue culture models, we found that overexpression of LMTK3 decreased the sensitivity of breast cancer cell lines to cytotoxic (doxorubicin) treatment. In a mouse model we showed that ectopic overexpression of LMTK3 decreases the efficacy of doxorubicin in reducing tumor growth. Interestingly, breast cancer cells overexpressing LMTK3 delayed the generation of double strand breaks (DSBs) after exposure to doxorubicin, as measured by the formation of γH2AX foci. This effect was at least partly mediated by decreased activity of ataxia-telangiectasia mutated kinase (ATM) as indicated by its reduced phosphorylation levels. In addition, our RNA-seq analyses showed that doxorubicin differentially regulated the expression of over 700 genes depending on LMTK3 protein expression levels. Furthermore, these genes were found to promote DNA repair, cell viability and tumorigenesis processes / pathways in LMTK3-overexpressing MCF7 cells. In human cancers, immunohistochemistry staining of LMTK3 in pre- and post-chemotherapy breast tumor pairs from four separate clinical cohorts revealed a significant increase of LMTK3 following both doxorubicin and docetaxel based chemotherapy. In aggregate, our findings show for the first time a contribution of LMTK3 in cytotoxic drug resistance in breast cancer.

Identification of curcumin derivatives as human LMTK3 inhibitors for breast cancer: a docking, dynamics, and MM/PBSA approach

Human lemur tyrosine kinase-3 (LMTK3) is primarily involved in regulation of estrogen receptor-α (ERα) by phosphorylation activity. LMTK3 acts as key biomarker for ERα positive breast cancer and identified as novel drug target for breast cancer. Due to the absence of experimental reports, the computational approach has been followed to screen LMTK3 inhibitors from natural product curcumin derivatives based on rational inhibitor design. The initial virtual screening and re-docking resulted in identification of top three leads with favorable binding energy and strong interactions in critical residues of ATP-binding cavity. ADME prediction confirmed the pharmacological activity of the leads with various properties. The stability and binding affinity of leads were well refined in dynamic system from 25 ns MD simulations. The behavior of protein motion towards closure of ATP-binding cavity was evaluated based on eigenvectors by PCA. In addition, MM/PBSA calculations also confirmed the relative binding free energy of LMTK3-lead complexes in favor of the effective binding. From our study, novel LMTK3 inhibitors tetrahydrocurcumin, curcumin 4,4'-diacetate, and demethoxycurcumin have been proposed with inhibition mechanism. Further experimental evaluation on reported lead candidates might prove its role in breast cancer therapeutics.

Applications of RNA Indexes for Precision Oncology in Breast Cancer

Precision oncology aims to offer the most appropriate treatments to cancer patients mainly based on their individual genetic information. Genomics has provided numerous valuable data on driver mutations and risk loci; however, it remains a formidable challenge to transform these data into therapeutic agents. Transcriptomics describes the multifarious expression patterns of both mRNAs and non-coding RNAs (ncRNAs), which facilitates the deciphering of genomic codes. In this review, we take breast cancer as an example to demonstrate the applications of these rich RNA resources in precision medicine exploration. These include the use of mRNA profiles in triple-negative breast cancer (TNBC) subtyping to inform corresponding candidate targeted therapies; current advancements and achievements of high-throughput RNA interference (RNAi) screening technologies in breast cancer; and microRNAs as functional signatures for defining cell identities and regulating the biological activities of breast cancer cells. We summarize the benefits of transcriptomic analyses in breast cancer management and propose that unscrambling the core signaling networks of cancer may be an important task of multiple-omic data integration for precision oncology.

αMβ2 Is Antiatherogenic in Female but Not Male Mice

Atherosclerosis is a complex inflammatory process characterized by monocyte recruitment into the arterial wall, their differentiation into macrophages, and lipid accumulation. Because integrin α_Mβ₂ (CD11b/CD18) mediates multiple diverse functions of leukocytes, we examined its role in atherogenesis. α_M^-/-/ApoE^-/- and ApoE^-/- mice were fed a control or high fat diet for 3 or 16 wk to induce atherogenesis. Unexpectedly, α_M deficiency accelerated development of atherosclerosis in female but not in male mice. The size of aortic root lesions was 3-4.5-fold larger in female α_M^-/-/ApoE^-/- than in ApoE^-/- mice. Monocyte and macrophage content within the lesions was increased 2.5-fold in female α_M^-/-/ApoE^-/- mice due to enhanced proliferation. α_Mβ₂ elimination promoted gender-dependent foam cell formation due to enhanced uptake of cholesterol by α_M^-/-/ApoE^-/- macrophages. This difference was attributed to enhanced expression of lipid uptake receptors, CD36 and scavenger receptor A1 (SR-A1), in female mice. Macrophages from female α_M^-/-/ApoE^-/- mice showed dramatically reduced expression of FoxM1 transcription factor and estrogen receptors (ER) α and β. As their antagonists inhibited the effect of 17β-estradiol (E₂), E₂ decreased CD36, SR-A1, and foam cell formation in ApoE^-/- macrophages in an ERα- and ERβ-dependent manner. However, female α_M^-/-/ApoE^-/- macrophages failed to respond to E₂ and maintained elevated CD36, SR-A1, and lipid accumulation. FoxM1 inhibition in ApoE^-/- macrophages reduced ERs and enhanced CD36 and SR-A1 expression, whereas FoxM1 overexpression in α_M^-/-/ApoE^-/- macrophages reversed their proatherogenic phenotype. We demonstrate a new, surprising atheroprotective role of α_Mβ₂ in female ApoE^-/- mice. α_Mβ₂ maintains ER expression in macrophages and E₂-dependent inhibition of foam cell formation.