Lung cancer cells survive epidermal growth factor receptor tyrosine kinase inhibitor exposure through upregulation of cholesterol synthesis

Discovery and Validation of Survival-Specific Genes in Papillary Renal Cell Carcinoma Using a Customized Next-Generation Sequencing Gene Panel

PURPOSE

Papillary renal cell carcinoma (PRCC), the second most common kidney cancer, is morphologically, genetically, and molecularly heterogeneous with diverse clinical manifestations. Genetic variations of PRCC and their association with survival are not yet well-understood. This study aimed to identify and validate survival-specific genes in PRCC and explore their clinical utility.

MATERIALS AND METHODS

Using machine learning, 293 patients from the Cancer Genome Atlas-Kidney Renal Papillary Cell Carcinoma (TCGA-KIRP) database were analyzed to derive genes associated with survival. To validate these genes, DNAs were extracted from the tissues of 60 Korean PRCC patients. Next generation sequencing was conducted using a customized PRCC gene panel of 202 genes, including 171 survival-specific genes. Kaplan-Meier and Log-rank tests were used for survival analysis. Fisher's exact test was performed to assess the clinical utility of variant genes.

RESULTS

A total of 40 survival-specific genes were identified in the TCGA-KIRP database through machine learning and statistical analysis. Of them, 10 (BAP1, BRAF, CFDP1, EGFR, ITM2B, JAK1, NODAL, PCSK2, SPATA13, and SYT5) were validated in the Korean-KIRP database. Among these survival gene signatures, three genes (BAP1, PCSK2, and SPATA13) showed survival specificity in both overall survival (OS) (p = 0.00004, p = 1.38 × 10-7, and p = 0.026, respectively) and disease-free survival (DFS) (p = 0.00002, p = 1.21 × 10-7, and p = 0.036, respectively). Notably, the PCSK2 mutation demonstrated survival specificity uniquely in both the TCGA-KIRP (OS: p = 0.010 and DFS: p = 0.301) and Korean-KIRP (OS: p = 1.38 × 10-7 and DFS: p = 1.21 × 10-7) databases.

CONCLUSIONS

We discovered and verified genes specific for the survival of PRCC patients in the TCGA-KIRP and Korean-KIRP databases. The survival gene signature, including PCSK2 commonly obtained from the 40 gene signature of TCGA and the 10 gene signature of the Korean database, is expected to provide insight into predicting the survival of PRCC patients and developing new treatment.

Proteomic Analysis Highlights the Impact of the Sphingolipid Metabolizing Enzyme β-Galactosylceramidase on Mitochondrial Plasticity in Human Melanoma

Mitochondrial plasticity, marked by a dynamism between glycolysis and oxidative phosphorylation due to adaptation to genetic and microenvironmental alterations, represents a characteristic feature of melanoma progression. Sphingolipids play a significant role in various aspects of cancer cell biology, including metabolic reprogramming. Previous observations have shown that the lysosomal sphingolipid-metabolizing enzyme β-galactosylceramidase (GALC) exerts pro-oncogenic functions in melanoma. Here, mining the cBioPortal for a Cancer Genomics data base identified the top 200 nuclear-encoded genes whose expression is negatively correlated with GALC expression in human melanoma. Their categorization indicated a significant enrichment in Gene Ontology terms and KEGG pathways related to mitochondrial proteins and function. In parallel, proteomic analysis by LC-MS/MS of two GALC overexpressing human melanoma cell lines identified 98 downregulated proteins when compared to control mock cells. Such downregulation was confirmed at a transcriptional level by a Gene Set Enrichment Analysis of the genome-wide expression profiling data obtained from the same cells. Among the GALC downregulated proteins, we identified a cluster of 42 proteins significantly associated with GO and KEGG categorizations related to mitochondrion and energetic metabolism. Overall, our data indicate that changes in GALC expression may exert a significant impact on mitochondrial plasticity in human melanoma cells.

Lipid metabolism and its implications in tumor cell plasticity and drug resistance: what we learned thus far?

Metabolic reprogramming, a hallmark of cancer, allows cancer cells to adapt to their specific energy needs. The Warburg effect benefits cancer cells in both hypoxic and normoxic conditions and is a well-studied reprogramming of metabolism in cancer. Interestingly, the alteration of other metabolic pathways, especially lipid metabolism has also grabbed the attention of scientists worldwide. Lipids, primarily consisting of fatty acids, phospholipids and cholesterol, play essential roles as structural component of cell membrane, signalling molecule and energy reserves. This reprogramming primarily involves aberrations in the uptake, synthesis and breakdown of lipids, thereby contributing to the survival, proliferation, invasion, migration and metastasis of cancer cells. The development of resistance to the existing treatment modalities poses a major challenge in the field of cancer therapy. Also, the plasticity of tumor cells was reported to be a contributing factor for the development of resistance. A number of studies implicated that dysregulated lipid metabolism contributes to tumor cell plasticity and associated drug resistance. Therefore, it is important to understand the intricate reprogramming of lipid metabolism in cancer cells. In this review, we mainly focused on the implication of disturbed lipid metabolic events on inducing tumor cell plasticity-mediated drug resistance. In addition, we also discussed the concept of lipid peroxidation and its crucial role in phenotypic switching and resistance to ferroptosis in cancer cells. Elucidating the relationship between lipid metabolism, tumor cell plasticity and emergence of resistance will open new opportunities to develop innovative strategies and combinatorial approaches for the treatment of cancer.

EGFR-driven lung adenocarcinomas coopt alveolar macrophage metabolism and function to support EGFR signaling and growth

The limited efficacy of currently approved immunotherapies in EGFR-driven lung adenocarcinoma (LUAD) underscores the need to better understand alternative mechanisms governing local immunosuppression to fuel novel therapies. Elevated surfactant and GM-CSF secretion from the transformed epithelium induces tumor-associated alveolar macrophage (TA-AM) proliferation which supports tumor growth by rewiring inflammatory functions and lipid metabolism. TA-AM properties are driven by increased GM-CSF-PPARγ signaling and inhibition of airway GM-CSF or PPARγ in TA-AMs suppresses cholesterol efflux to tumor cells, which impairs EGFR phosphorylation and restrains LUAD progression. In the absence of TA-AM metabolic support, LUAD cells compensate by increasing cholesterol synthesis, and blocking PPARγ in TA-AMs simultaneous with statin therapy further suppresses tumor progression and increases proinflammatory immune responses. These results reveal new therapeutic combinations for immunotherapy resistant EGFR-mutant LUADs and demonstrate how cancer cells can metabolically co-opt TA-AMs through GM-CSF-PPARγ signaling to provide nutrients that promote oncogenic signaling and growth.

EGFR TKI resistance in lung cancer cells using RNA sequencing and analytical bioinformatics tools

Epidermal Growth Factor Receptor (EGFR) signaling and EGFR mutations play key roles in cancer pathogenesis, particularly in the development of drug resistance. For the ∼20% of all non-small cell lung cancer (NSCLC) patients that harbor an activating mutation, EGFR tyrosine kinase inhibitors (TKIs) provide initial clinical responses. However, long-term efficacy is not possible due to acquired drug resistance. Despite a gradually increasing knowledge of the mechanisms underpinning the development of resistance in tumors, there has been very little success in overcoming it and it is probable that many additional mechanisms are still unknown. Herein, publicly available RNASeq (RNA sequencing) datasets comparing lung cancer cell lines treated with EGFR TKIs until resistance developed with their corresponding parental cells and protein array data from our own EGFR TKI treated xenograft tumors, were analyzed for differential gene expression, with the intent to investigate the potential mechanisms of drug resistance to EGFR TKIs. Pathway analysis, as well as structural disorder analysis of proteins in these pathways, revealed several key proteins, including DUSP1, DUSP6, GAB2, and FOS, that could be targeted using novel combination therapies to overcome EGFR TKI resistance in lung cancer.

How Neuromembrane Lipids Modulate Membrane Proteins: Insights from G-Protein-Coupled Receptors (GPCRs) and Receptor Tyrosine Kinases (RTKs)

Lipids play a diverse and critical role in cellular processes in all tissues. The unique lipid composition of nerve membranes is particularly interesting because it contains, among other things, polyunsaturated lipids, such as docosahexaenoic acid, which the body only gets through the diet. The crucial role of lipids in neurological processes, especially in receptor-mediated cell signaling, is emphasized by the fact that in many neuropathological diseases there are significant deviations in the lipid composition of nerve membranes compared to healthy individuals. The lipid composition of neuromembranes can significantly affect the function of receptors by regulating the physical properties of the membrane or by affecting specific interactions between receptors and lipids. In addition, it is worth noting that the ligand-binding pocket of many receptors is located inside the cell membrane, due to which lipids can even modulate the binding of ligands to their receptors. These mechanisms highlight the importance of lipids in the regulation of membrane receptor activation and function. In this article, we focus on two major protein families: G-protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) and discuss how lipids affect their function in neuronal membranes, elucidating the basic mechanisms underlying neuronal function and dysfunction.

EGFR + lung adenocarcinomas coopt alveolar macrophage metabolism and function to support EGFR signaling and growth

The limited efficacy of currently approved immunotherapies in EGFR-mutant lung adenocarcinoma (LUAD) underscores the need to better understand mechanisms governing local immunosuppression. Elevated surfactant and GM-CSF secretion from the transformed epithelium induces tumor-associated alveolar macrophages (TA-AM) to proliferate and support tumor growth by rewiring inflammatory functions and lipid metabolism. TA-AM properties are driven by increased GM-CSF-PPARγ signaling and inhibition of airway GM-CSF or PPARγ in TA-AMs suppresses cholesterol efflux to tumor cells, which impairs EGFR phosphorylation and restrains LUAD progression. In the absence of TA-AM metabolic support, LUAD cells compensate by increasing cholesterol synthesis, and blocking PPARγ in TA-AMs simultaneous with statin therapy further suppresses tumor progression and increases T cell effector functions. These results reveal new therapeutic combinations for immunotherapy resistant EGFR-mutant LUADs and demonstrate how such cancer cells can metabolically co-opt TA-AMs through GM-CSF-PPARγ signaling to provide nutrients that promote oncogenic signaling and growth.

Role of Cannabidiol for Improvement of the Quality of Life in Cancer Patients: Potential and Challenges

There is currently a growing interest in the use of cannabidiol (CBD) to alleviate the symptoms caused by cancer, including pain, sleep disruption, and anxiety. CBD is often self-administered as an over-the-counter supplement, and patients have reported benefits from its use. However, despite the progress made, the mechanisms underlying CBD’s anti-cancer activity remain divergent and unclear. Herein, we provide a comprehensive review of molecular mechanisms to determine convergent anti-cancer actions of CBD from pre-clinical and clinical studies. In vitro studies have begun to elucidate the molecular targets of CBD and provide evidence of CBD’s anti-tumor properties in cell and mouse models of cancer. Furthermore, several clinical trials have been completed testing CBD’s efficacy in treating cancer-related pain. However, most use a mixture of CBD and the psychoactive, tetrahydrocannabinol (THC), and/or use variable dosing that is not consistent between individual patients. Despite these limitations, significant reductions in pain and opioid use have been reported in cancer patients using CBD or CBD+THC. Additionally, significant improvements in quality-of-life measures and patients’ overall satisfaction with their treatment have been reported. Thus, there is growing evidence suggesting that CBD might be useful to improve the overall quality of life of cancer patients by both alleviating cancer symptoms and by synergizing with cancer therapies to improve their efficacy. However, many questions remain unanswered regarding the use of CBD in cancer treatment, including the optimal dose, effective combinations with other drugs, and which biomarkers/clinical presentation of symptoms may guide its use.

Inhibition of epidermal growth factor receptor suppresses parathyroid hormone-related protein expression in tumours and ameliorates cancer-associated cachexia

BACKGROUND

Lung cancer is the primary cause of cancer deaths worldwide. Activation of epidermal growth factor receptor (EGFR) leads to lung cancer progression and poor prognosis while involuntary weight loss remains a major problem. Tumour-derived parathyroid hormone-related protein (PTHrP) emerged as a potential mediator of cachexia. Here, we investigated the modulatory role of EGFR signalling in PTHrP (encoded by Pthlh) gene expression and the impact of this relationship on cancer cachexia.

METHODS

Global gene expression profiles of Lewis lung carcinoma (LLC) cells were analysed. Pthlh mRNA levels were measured by qRT-PCR in LLC cells treated with EGFR ligands and tyrosine kinase inhibitors (TKIs). LLC tumour-bearing mice received EGFR TKI erlotinib for 7 days via intraperitoneal injection or oral gavage. Tumour Pthlh mRNA, weight of fat/muscle tissue, and grip strength were assessed. RNA-seq data from The Cancer Genome Atlas and gene expression analysis tools were used to characterize expression profiles of PTHLH and EGFR along with correlation analysis of PTHLH with EGFR and transforming growth factor alpha (TGFA) in human lung cancer and head and neck squamous carcinoma (HNSC). Survival of lung squamous cell carcinoma (LUSC) and lung adenocarcinoma (LUAD) patients with EGFR gene alterations was analysed in regard to PTHLH expression.

RESULTS

Expression of EGFR ligands, EGFR itself, and PTHrP co-clusters in LLC cells. Activation of EGFR signalling with its ligands significantly increases (3.8-fold, P < 0.0005) while EGFR TKIs significantly decrease (90%, P < 0.0005) Pthlh mRNA levels in LLC cells. Pthlh mRNA drops 65-75% (P < 0.0005) in tumours upon treatment of LLC tumour-bearing mice with erlotinib while their muscle mass and grip strength increase (9.2% P < 0.05, 23% P < 0.005, respectively) compared with tumour-bearing control mice. PTHLH is overexpressed in tumours of LUSC (45.8-fold, P < 0.05) and HNSC (17.5-fold, P < 0.05) compared with normal tissue. PTHLH expression correlates with EGFR and its ligand TGFA in both cancers (LUSC: n = 745, R = 0.32, P < 0.0001 and R = 0.51, P < 0.0001; HNSC: n = 545, R = 0.34, P < 0.001 and R = 0.50, P < 0.001, respectively). High PTHLH mRNA associates with poor overall survival in LUAD patients with activating EGFR mutations (n = 40, log-rank test, P = 0.0451).

CONCLUSIONS

Epidermal growth factor receptor signalling regulates expression of cachexia mediator PTHrP. EGFR inhibition reduces PTHrP expression in LLC tumours and ameliorates cachexia in LLC tumour-bearing mice.

Proteomic characterization of a candidate polygenic driver of metabolism in non-small cell lung cancer

Proteome analysis revealed signatures of co-expressed upregulated metabolism proteins highly conserved between primary and non-small cell lung cancer (NSCLC) patient-derived xenograft tumors (Li et al. 2014, Nat. Communications 5:5469). The C10 signature is encoded by seven genes (ADSS, ATP2A2, CTPS1, IMPDH2, PKM2, PTGES3, SGPL1) and DNA alterations in C10-encoding genes are associated with longer survival in a subset of NSCLC. To explore the C10 signature as an oncogenic driver and address potential mechanisms of action, C10 protein expression and protein-protein interactions were determined. In independent NSCLC cohorts, the coordinated expression of C10 proteins was significant and mutations in C10 genes were associated with better outcome. Affinity purification-mass spectrometry and in vivo proximity-based biotin identification defined a C10 interactome involving 667 proteins including candidate drug targets and clusters associated with glycolysis, calcium homeostasis, and nucleotide and sphingolipid metabolism. DNA alterations in genes encoding C10 interactome components were also found to be associated with better survival. These data support the notion that the coordinated upregulation of the C10 signature impinges metabolic processes that collectively function as an oncogenic driver in NSCLC.

Pretreatment HDL-C and ApoA1 are predictive biomarkers of progression-free survival in patients with EGFR mutated advanced non-small cell lung cancer treated with TKI

BACKGROUND

We aimed to explore the correlation between blood lipids (high density lipoprotein cholesterol [HDL-C] and apolipoprotein A1 [ApoA1]) and epidermal growth factor receptor (EGFR) T790M mutation, as well as its predictive role in clinical efficacy and progression-free survial (PFS) in advanced non-small cell lung cancer (NSCLC) patients treated with EGFR tyrosine kinase inhibitors (EGFR-TKI).

METHODS

We retrospectively collected information of 153 patients with advanced NSCLC harboring exon EGFR mutation and receiving EGFR-TKI.

RESULTS

The best cutoff value for HDL-C and ApoA1 was determined to be 1.15 and 1.14 mmol/l. The overall response rate (ORR) was 67.7% in the high HDL-C group and 46.6% in the low HDL-C group, respectively. The ORR of the high ApoA1 group showed a significant increase than that of the low ApoA1 group (68.1% vs. 38.5%). The mean ApoA1 level of the EGFR T790M mutation-positive group was significantly higher than that of the EGFR T790M mutation-negative group (1.13 g/l vs. 1.01 g/l). Patients with high ApoA1 levels were related to the EGFR T790M mutation (r = 0.324). (3) The median progression-free survival (PFS) of the high HDL-C group and low HDL-C group were 13.00 months and 10.20 months. The median PFS of the high ApoA1 group and the low ApoA1 group were 12.10 and 10.00 months, respectively. Multivariate Cox stepwise regression model analysis demonstrated ECOG PS, pathological type and HDL-C were confirmed as critical and independent predictors of PFS.

CONCLUSIONS

Patients with EGFR T790M mutations often show higher ApoA1 levels. Peripheral serum HDL-C and ApoA1 before treatment can be used as potential significant factors for predicting clinical efficacy and PFS in advanced NSCLC patients treated with EGFR-TKI.

A Transcriptomic Approach to Elucidate the Mechanisms of Gefitinib-Induced Toxicity in Healthy Human Intestinal Organoids

Gefitinib is a tyrosine kinase inhibitor (TKI) that selectively inhibits the epidermal growth factor receptor (EGFR), hampering cell growth and proliferation. Due to its action, gefitinib has been used in the treatment of cancers that present abnormally increased expression of EGFR. However, side effects from gefitinib therapy may occur, among which diarrhoea is most common, that can lead to interruption of the planned therapy in the more severe cases. The mechanisms underlying intestinal toxicity induced by gefitinib are not well understood. Therefore, this study aims at providing insight into these mechanisms based on transcriptomic responses induced in vitro. A 3D culture of healthy human colon and small intestine (SI) organoids was exposed to 0.1, 1, 10 and 30 µM of gefitinib, for a maximum of three days. These drug concentrations were selected using physiologically-based pharmacokinetic simulation considering patient dosing regimens. Samples were used for the analysis of viability and caspase 3/7 activation, image-based analysis of structural changes, as well as RNA isolation and sequencing via high-throughput techniques. Differential gene expression analysis showed that gefitinib perturbed signal transduction pathways, apoptosis, cell cycle, FOXO-mediated transcription, p53 signalling pathway, and metabolic pathways. Remarkably, opposite expression patterns of genes associated with metabolism of lipids and cholesterol biosynthesis were observed in colon versus SI organoids in response to gefitinib. These differences in the organoids’ responses could be linked to increased activated protein kinase (AMPK) activity in colon, which can influence the sensitivity of the colon to the drug. Therefore, this study sheds light on how gefitinib induces toxicity in intestinal organoids and provides an avenue towards the development of a potential tool for drug screening and development.

It Takes More than Two to Tango: Complex, Hierarchal, and Membrane-Modulated Interactions in the Regulation of Receptor Tyrosine Kinases

The search for an understanding of how cell fate and motility are regulated is not a purely scientific undertaking, but it can also lead to rationally designed therapies against cancer. The discovery of tyrosine kinases about half a century ago, the subsequent characterization of certain transmembrane receptors harboring tyrosine kinase activity, and their connection to the development of human cancer ushered in a new age with the hope of finding a treatment for malignant diseases in the foreseeable future. However, painstaking efforts were required to uncover the principles of how these receptors with intrinsic tyrosine kinase activity are regulated. Developments in molecular and structural biology and biophysical approaches paved the way towards better understanding of these pathways. Discoveries in the past twenty years first resulted in the formulation of textbook dogmas, such as dimerization-driven receptor association, which were followed by fine-tuning the model. In this review, the role of molecular interactions taking place during the activation of receptor tyrosine kinases, with special attention to the epidermal growth factor receptor family, will be discussed. The fact that these receptors are anchored in the membrane provides ample opportunities for modulatory lipid-protein interactions that will be considered in detail in the second part of the manuscript. Although qualitative and quantitative alterations in lipids in cancer are not sufficient in their own right to drive the malignant transformation, they both contribute to tumor formation and also provide ways to treat cancer. The review will be concluded with a summary of these medical aspects of lipid-protein interactions.

High Circulating Sonic Hedgehog Protein Is Associated With Poor Outcome in EGFR-Mutated Advanced NSCLC Treated With Tyrosine Kinase Inhibitors

Introduction

Growing preclinical evidence has suggested that the Sonic hedgehog (Shh) pathway is involved in resistance to tyrosine kinase inhibitor (TKI) therapy for EGFR-mutated (EGFRm) non-small cell lung cancer (NSCLC). However, little is known concerning the prognostic value of this pathway in this context.

Materials and Methods

We investigated the relationship between plasma levels of Shh and EGFRm NSCLC patients’ outcome with EGFR TKIs. We included 74 consecutive patients from two institutions with EGFRm advanced NSCLC treated by EGFR TKI as first-line therapy. Plasma samples were collected longitudinally for each patient and were analyzed for the expression of Shh using an ELISA assay. The activation of the Shh–Gli1 pathway was assessed through immunohistochemistry (IHC) of Gli1 and RT-qPCR analysis of the transcripts of Gli1 target genes in 14 available tumor biopsies collected at diagnosis (baseline).

Results

Among the 74 patients, only 61 had baseline (diagnosis) plasma samples, while only 49 patients had plasma samples at the first evaluation. Shh protein was detectable in all samples at diagnosis (n = 61, mean = 1,041.2 ± 252.5 pg/ml). Among the 14 available tumor biopsies, nuclear expression of Gli1 was observed in 57.1% (8/14) of patients’ biopsies. Shh was significantly (p < 0.05) enriched in youth (age < 68), male, nonsmokers, patients with a PS > 1, and patients presenting more than 2 metastatic sites and L858R mutation. Higher levels of Shh correlated with poor objective response to TKI, shorter progression-free survival (PFS), and T790M-independent mechanism of resistance. In addition, the rise of plasma Shh levels along the treatment was associated with the emergence of drug resistance in patients presenting an initial good therapy response.

Conclusion

These data support that higher levels of plasma Shh at diagnosis and increased levels of Shh along the course of the disease are related to the emergence of TKI resistance and poor outcome for EGFR-TKI therapy, suggesting that Shh levels could stand both as a prognostic and as a resistance biomarker for the management of EGFR-mutated NSCLC patients treated with EGFR-TKI.

DPP4 Regulates DHCR24-Mediated Cholesterol Biosynthesis to Promote Methotrexate Resistance in Gestational Trophoblastic Neoplastic Cells

Metabolic reprogramming could promote cellular adaptation in response to chemotherapeutic drugs in cancer cells. Herein, we aimed to characterize the metabolomic profiles regulated by Dipeptidyl Peptidase 4 (DPP4) in methotrexate (MTX)-resistant gestational trophoblastic neoplastic (GTN) cells. A total of eighty metabolites were found to be commonly altered in DPP4-depleted JAR/MTX and JEG3/MTX cells. Cholesterol biosynthesis-related metabolites were markedly impacted by DPP4 knockdown in MTX-resistant sublines. Manipulation of DPP4 expression remarkably affected the level of cellular cholesterol in GTN cells. Our analysis also identified 24-Dehydrocholesterol Reductase (DHCR24) as a potential downstream effector of DPP4. Manipulation of DHCR24 expression affected cellular cholesterol level, reactive oxygen species (ROS) accumulation, and chemosensitivity to MTX in GTN cell models. In addition, over-expression of DHCR24 could markedly restore cellular cholesterol level and rescue cell survival in DPP4-depleted MTX-resistant GTN cells. Highly correlated expression of DPP4 and DHCR24 was observed in clinical GTN specimens. Further, DPP4 inhibitor sitagliptin effectively inhibited cholesterol biosynthesis, reduced DHCR24 expression and enhanced MTX-induced cytotoxicity in vitro and in vivo. In conclusion, our findings suggested that DPP4 might regulate DHCR24-mediated cholesterol biosynthesis to promote methotrexate resistance in GTN cells. Targeting DPP4/DHCR24 signaling might help to sensitize MTX-resistant GTN to MTX treatment.

Mechanistic Insights Delineating the Role of Cholesterol in Epithelial Mesenchymal Transition and Drug Resistance in Cancer

Despite the significant advancements made in targeted anti-cancer therapy, drug resistance constitutes a multifaceted phenomenon leading to therapy failure and ultimately mortality. Emerging experimental evidence highlight a role of cholesterol metabolism in facilitating drug resistance in cancer. This review aims to describe the role of cholesterol in facilitating multi-drug resistance in cancer. We focus on specific signaling pathways that contribute to drug resistance and the link between these pathways and cholesterol. Additionally, we briefly discuss the molecular mechanisms related to the epithelial-mesenchymal transition (EMT), and the documented link between EMT, metastasis and drug resistance. We illustrate this by specifically focusing on hypoxia and the role it plays in influencing cellular cholesterol content following EMT induction. Finally, we provide a proposed model delineating the crucial role of cholesterol in EMT and discuss whether targeting cholesterol could serve as a novel means of combatting drug resistance in cancer progression and metastasis.

Enzymes in the Cholesterol Synthesis Pathway: Interactomics in the Cancer Context

A global protein interactome ensures the maintenance of regulatory, signaling and structural processes in cells, but at the same time, aberrations in the repertoire of protein-protein interactions usually cause a disease onset. Many metabolic enzymes catalyze multistage transformation of cholesterol precursors in the cholesterol biosynthesis pathway. Cancer-associated deregulation of these enzymes through various molecular mechanisms results in pathological cholesterol accumulation (its precursors) which can be disease risk factors. This work is aimed at systematization and bioinformatic analysis of the available interactomics data on seventeen enzymes in the cholesterol pathway, encoded by HMGCR, MVK, PMVK, MVD, FDPS, FDFT1, SQLE, LSS, DHCR24, CYP51A1, TM7SF2, MSMO1, NSDHL, HSD17B7, EBP, SC5D, DHCR7 genes. The spectrum of 165 unique and 21 common protein partners that physically interact with target enzymes was selected from several interatomic resources. Among them there were 47 modifying proteins from different protein kinases/phosphatases and ubiquitin-protein ligases/deubiquitinases families. A literature search, enrichment and gene co-expression analysis showed that about a quarter of the identified protein partners was associated with cancer hallmarks and over-represented in cancer pathways. Our results allow to update the current fundamental view on protein-protein interactions and regulatory aspects of the cholesterol synthesis enzymes and annotate of their sub-interactomes in term of possible involvement in cancers that will contribute to prioritization of protein targets for future drug development.

Drug Tolerance to EGFR Tyrosine Kinase Inhibitors in Lung Cancers with EGFR Mutations

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) serve as the standard of care for the first-line treatment of patients with lung cancers with EGFR-activating mutations. However, the acquisition of resistance to EGFR TKIs is almost inevitable, with extremely rare exceptions, and drug-tolerant cells (DTCs) that demonstrate reversible drug insensitivity and that survive the early phase of TKI exposure are hypothesized to be an important source of cancer cells that eventually acquire irreversible resistance. Numerous studies on the molecular mechanisms of drug tolerance of EGFR-mutated lung cancers employ lung cancer cell lines as models. Here, we reviewed these studies to generally describe the features, potential origins, and candidate molecular mechanisms of DTCs. The rapid development of an optimal treatment for EGFR-mutated lung cancer will require a better understanding of the underlying molecular mechanisms of the drug insensitivity of DTCs.

Roles of Farnesyl-Diphosphate Farnesyltransferase 1 in Tumour and Tumour Microenvironments

Farnesyl-diphosphate farnesyltransferase 1 (FDFT1, squalene synthase), a membrane-associated enzyme, synthesizes squalene via condensation of two molecules of farnesyl pyrophosphate. Accumulating evidence has noted that FDFT1 plays a critical role in cancer, particularly in metabolic reprogramming, cell proliferation, and invasion. Based on these advances in our knowledge, FDFT1 could be a potential target for cancer treatment. This review focuses on the contribution of FDFT1 to the hallmarks of cancer, and further, we discuss the applicability of FDFT1 as a cancer prognostic marker and target for anticancer therapy.