Isoprenylcysteine Carboxyl Methyltransferase Research Articles

Isoprenylcysteine carboxyl methyltransferase (ICMT) promotes invadopodia formation and metastasis in cancer cells

Isoprenyl cysteine carboxyl methyltransferase (ICMT) catalyzes the last step of the prenylation pathway. Previously, we found that high ICMT levels enhance tumorigenesis in vivo and that its expression is repressed by the p53 tumor suppressor. Based on evidence suggesting that some ICMT substrates affect invasive traits, we wondered if this enzyme may promote metastasis. In this work, we found that ICMT overexpression enhanced lung metastasis in vivo. Accordingly, ICMT overexpression also promoted cellular functions associated with aggressive phenotypes such as migration and invasion in vitro. Considering that some ICMT substrates are involved in the regulation of actin cytoskeleton, we hypothesized that actin-rich structures, associated with invasion and metastasis, may be affected. Our findings revealed that ICMT enhanced the formation of invadopodia. Additionally, by analyzing cancer patient databases, we found that ICMT is overexpressed in several tumor types. Furthermore, the concurrent expression of ICMT and CTTN, which encodes a crucial component of invadopodia, showed a significant correlation with clinical outcome. In summary, our work identifies ICMT overexpression as a relevant alteration in human cancer that promotes the development of metastatic tumors.

An overview of recent advancements in small molecules suppression of oncogenic signaling of K-RAS: an updated review.

RAS (rat sarcoma) oncoproteins are crucial for the growth of some human cancers, including lung, colorectal, and pancreatic adenocarcinomas. The RAS family contains three known human isoforms H(Harvey)-RAS, N(Neuroblastoma)-RAS, and K(Kirsten)-RAS. Mutations in RAS proteins cause up to ~ 30% of cancer cases. For almost 30 years, mutant proteins druggable pockets remained undiscovered, they are nearly identical to their essential, wild-type counterparts and cause cancer. Recent research has increased our knowledge of RAS's structure, processing, and signaling pathways and revealed novel insights into how it works in cancer cells. We highlight several approaches that inhibit RAS activity with small compounds in this review: substances that blocked farnesyltransferase (FTase), isoprenylcysteine carboxyl methyltransferase (Icmt), and RAS-converting enzyme 1 (Rce1) three important enzymes required for RAS localization. Inhibitors block the son of sevenless (SOS) protein's role in nucleotide exchange activity, small molecules that interfered with the phosphodiesterase (PDEδ)-mediated intracellular RAS transport processes, substances that focused on inhibiting RAS-effector interactions. Inhibitors are made to suppress the oncogenic K-RAS G12C mutant only when the nucleophilic cysteine residue at codon 12 is present and many inhibitors with various mechanisms like breaking the organization membrane of K-RAS nano-clustering. So, this is a thorough analysis of the most recent advancements in K-RAS-targeted anticancer techniques, hopefully offering insight into the field's future.

Inhibition of mitochondrial function by approved drugs overcomes nasopharyngeal carcinoma chemoresistance.

The development of chemo-resistance in nasopharyngeal carcinoma (NPC) presents a significant therapeutic challenge, and its underlying mechanisms remain poorly understood. In our previous studies, we highlighted the association between isoprenylcysteine carboxylmethyltransferase (ICMT) and chemoresistance in NPC. In this current research, we revealed that both 5-FU and cisplatin-resistant NPC cells exhibited elevated mitochondrial function and increased expression of mitochondrial genes, independent of ICMT. Our investigations further showed that classic mitochondrial inhibitors, such as oligomycin, antimycin, and rotenone, were notably more effective in reducing viability in chemo-resistant NPC cells compared to parental cells. Moreover, we identified two antimicrobial drugs, tigecycline and atovaquone, recognized as mitochondrial inhibitors, as potent agents for decreasing chemo-resistant NPC cells by targeting mitochondrial respiration. Remarkably, tigecycline and atovaquone, administered at tolerable doses, inhibited chemo-resistant NPC growth in mouse models and extended overall survival rates. This work unveils the efficacy of mitochondrial inhibition as a promising strategy to overcome chemo-resistance in NPC. Additionally, our findings highlight the potential repurposing of clinically available drugs like tigecycline and atovaquone for treating NPC patients who develop chemoresistance.

Isoprenylcysteine carboxyl methyltransferase inhibitors: QSAR, docking and molecular dynamics studies

A quantitative structure-activity relationship (QSAR) investigation was conducted to build models that correlate the structures of 273 compounds to their actions against Isoprenylcysteine Carboxyl Methyltransferase (ICMT) protein. Genetic Algorithm (GA) was used to select the final set of descriptors and create the correlation models that associate the structural characteristics of the chemicals to their biological activity. Three QSAR models (four descriptor based) were identified having coefficient of determination (R2) for the training set as 0.7183, 0.7358 and 0.7475 and for external validation set 0.813, 0.746 and 0.728. Artificial Neural Network(ANN) was used to establish the strength of the QSAR models. ANN model assessed the descriptor's contribution to the structure-activity association. The descriptors that formed the best models were used to form the ANN model. The correlation coefficient(R) of the ANN model was = 0.919. The MSE was 0.24 for the training set, 0.30 for the validation set and 0.15 for the test set. In accordance with the statistical findings, the QSAR models were significant and exhibited excellent stability with respect to data fluctuation in the validation technique. The docking study revealed the best molecule, which formed a hydrophobic contact and hydrogen bond with ICMT amino acid residues and had a docking affinity of -9.5 kcal/mol. Molecular dynamics studies were also performed to understand the interactions between the protein and the ligands. Ligand 264 complex trajectory showed stable behavior with lesser fluctuations and supported the molecular docking result. The results of the QSAR, molecular docking and dynamics study can be further analysed to develop specific inhibitors of ICMT.

CircRNA hsa_circ_0018289 exerts an oncogenic role in cervical cancer progression through miR-1294/ICMT axis.

BackgroundcircRNA hsa_circ_0018289‐mediated growth and metastasis of CC cells were investigated, as well as the mechanistic pathway.MethodsQuantitative real‐time reverse transcription‐polymerase chain reaction (qRT‐PCR) was carried out to examine the expression of hsa_circ_0018289, microRNA (miR)‐1294, and isoprenylcysteine carboxyl methyltransferase (ICMT). CC cell proliferation, migration, and invasion were evaluated by 5‐ethynyl‐2’‐deoxyuridine (EdU) incorporation, colony formation, transwell assays, Western blot analysis of ICMT, and glycolysis‐associated proteins. Dual‐luciferase reporter or RNA pull‐down analysis of the target interaction between miR‐1294 and hsa_hsa_circ_0018289 or ICMT. Xenograft model assay was implemented to assess the role of hsa_circ_0018289 in vivo. Immunofluorescence (IHC) was employed to detect the level of Ki‐67.ResultsHsa_circ_0018289 was elevated in CC tissues and cells, its deficiency could repress growth, metastasis, and glycolysis of CC cells in vitro, as well as hamper tumor growth in vivo. Hsa_circ_0018289 sponged miR‐1294 while miR‐1294 bound with ICMT, and the inhibition of miR‐1294 or addition of ICMT could partially relieve the effect caused by hsa_circ_0018289 depletion.ConclusionHsa_circ_0018289 contributes to malignant development by regulating the miR‐1294/ICMT axis, affording novel insight into CC therapy.

An In Vivo Inflammatory Loop Potentiates KRAS Blockade.

KRAS (KRAS proto-oncogene, GTPase) inhibitors perform less well than other targeted drugs in vitro and fail clinical trials. To investigate a possible reason for this, we treated human and murine tumor cells with KRAS inhibitors deltarasin (targeting phosphodiesterase-δ), cysmethynil (targeting isoprenylcysteine carboxylmethyltransferase), and AA12 (targeting KRASG12C), and silenced/overexpressed mutant KRAS using custom-designed vectors. We showed that KRAS-mutant tumor cells exclusively respond to KRAS blockade in vivo, because the oncogene co-opts host myeloid cells via a C-C-motif chemokine ligand 2 (CCL2)/interleukin-1 beta (IL-1β)-mediated signaling loop for sustained tumorigenicity. Indeed, KRAS-mutant tumors did not respond to deltarasin in C-C motif chemokine receptor 2 (Ccr2) and Il1b gene-deficient mice, but were deltarasin-sensitive in wild-type and Ccr2-deficient mice adoptively transplanted with wild-type murine bone marrow. A KRAS-dependent pro-inflammatory transcriptome was prominent in human cancers with high KRAS mutation prevalence and poor predicted survival. Our findings support that in vitro cellular systems are suboptimal for anti-KRAS drug screens, as these drugs function to suppress interleukin-1 receptor 1 (IL1R1) expression and myeloid IL-1β-delivered pro-growth effects in vivo. Moreover, the findings support that IL-1β blockade might be suitable for therapy for KRAS-mutant cancers.

Isoprenylcysteine carboxyl methyltransferase is critical for glioblastoma growth and survival by activating Ras/Raf/Mek/Erk.

The poor outcomes in glioblastoma necessitate new therapeutic target. Isoprenylcysteine carboxyl methyltransferase (ICMT), a unique enzyme of the final step of prenylation that modifies activities of oncogenic proteins, represents a promising target for many cancers. Expression pattern, function and downstream pathway of ICMT in glioblastoma were analyzed using immunohistochemistry, ELISA, cellular assays and immunoblotting method. Combinatory effect was analyzed using Chou-Talalay approach. Upregulation of ICMT expression is a common phenomenon in glioblastoma patients regardless of clinicopathological characteristics. Gain-of-function and loss-of-function analysis support the role of ICMT in glioblastoma growth and survival but not migration. Importantly, pharmacological inhibitors of ICMT are effectively against glioblastoma cells while sparing normal neuron cells, and furthermore that they act synergistically with chemotherapeutic drugs. Consistently, ICMT inhibitor UCM-1336 significantly inhibits glioblastoma growth without causing toxicity in mice. Mechanistic studies demonstrate that Ras/Raf/Mek/Erk rather than Ras/PI3K/Akt/mTOR is the downstream pathway of ICMT-mediated glioblastoma growth. Our findings provide the proof-of-concept of pharmacologically targeting ICMT in the treatment of glioblastoma via deactivation of Ras/Raf/Mek/Erk.

Isoprenylcysteine carboxyl methyltransferase promotes the progression of tongue squamous cell carcinoma via the K-Ras and RhoA signaling pathways

ObjectiveThis research investigated the biological role of isoprenylcysteine carboxyl methyltransferase (ICMT) in tongue squamous cell carcinoma (TSCC) progression meanwhile to explore the conceivable mechanism. MethodsThe mRNA and protein expression were measured using real-time PCR and Western blot. Cell proliferation, apoptosis, cycle distribution, migration and invasion were evaluated by CCK-8 assay, flow cytometry, wound-healing assay and transwell assay. The anti-tumor activity of ICMT silencing was observed in nude mice. ResultsOur results indicated that silencing of ICMT-mediated methylation effectively inhibited TSCC cells proliferation in vitro and reduced tumor growth in vivo. Moreover, ICMT knockdown also induced cell apoptosis and cell cycle arrest of both CAL-27 and SCC-4 cells. In addition, CAL-27 and SCC-4 cells migration and invasion were weakened by ICMT siRNA. Mechanistically, ICMT deficiency significantly decreased the K-Ras and RhoA membrane targeting localization, leading to the suppression of K-Ras- and RhoA-mediated downstream signaling in CAL-27 and SCC-4 cells. ConclusionsAltogether, our findings identified a crucial role played by ICMT in the progression of TSCC and the potential mechanisms by which exerted its effects, indicating that targeting ICMT may represent a promising therapeutic strategy for TSCC.

Lidocaine exerts anticancer activity in bladder cancer by targeting isoprenylcysteine carboxylmethyltransferase (ICMT).

BackgroundBladder cancer is one of the most common malignant tumors among humans and has a high mortality. Clinically, lidocaine is the most commonly used local anesthetic, which can inhibit the proliferation of bladder cancer cells; however, its downstream specific molecular mechanisms are unclear.MethodsThe SwissTarget and TargetNet databases were used to analyze the target of lidocaine. The online public cancer transcriptome database UALCAN was used to analyze the up-regulated genes in The Cancer Genome Atlas Urothelial Bladder Carcinoma (TCGA-BLCA) data collection, and the intersection of the 2 was used to obtain the core target. The only target, isoprenylcysteine carboxylmethyltransferase (ICMT), was obtained by combining the correlation between the target and the clinical information of bladder cancer and the Kaplan-Meier (K-M) survival curve. Then, UMUC3 and T24 cells were selected as research vectors in vitro. Cell proliferation, cell cycle, and apoptosis were detected by cell counting kit-8, colony formation, flow cytometry, and western blotting.ResultsNetwork pharmacology analysis showed that ICMT might be one of the targets of lidocaine, and the expression level of ICMT was closely related to the clinical phenotype of bladder cancer. Lidocaine treatment (4 and 8 mM) significantly inhibited the proliferation of UMUC3 and T24 cells, promoted apoptosis, and significantly inhibited the mass and volume of xenograft tumors. In vitro experiments showed that ICMT promoted the proliferation of UMUC3 and T24 cells. Lidocaine inhibited the expression of ICMT in UMUC3 and T24 cells in a concentration and time-dependent manner, and inhibited cell proliferation by down-regulating ICMT expression.ConclusionsLidocaine exerts anti-tumor effect by down-regulating the expression of ICMT in bladder cancer.

Suppression of isoprenylcysteine carboxylmethyltransferase compromises DNA damage repair.

DNA damage is a double-edged sword for cancer cells. On the one hand, DNA damage-induced genomic instability contributes to cancer development; on the other hand, accumulating damage compromises proliferation and survival of cancer cells. Understanding the key regulators of DNA damage repair machinery would benefit the development of cancer therapies that induce DNA damage and apoptosis. In this study, we found that isoprenylcysteine carboxylmethyltransferase (ICMT), a posttranslational modification enzyme, plays an important role in DNA damage repair. We found that ICMT suppression consistently reduces the activity of MAPK signaling, which compromises the expression of key proteins in the DNA damage repair machinery. The ensuing accumulation of DNA damage leads to cell cycle arrest and apoptosis in multiple breast cancer cells. Interestingly, these observations are more pronounced in cells grown under anchorage-independent conditions or grown in vivo. Consistent with the negative impact on DNA repair, ICMT inhibition transforms the cancer cells into a "BRCA-like" state, hence sensitizing cancer cells to the treatment of PARP inhibitor and other DNA damage-inducing agents.

Isoprenylcysteine Carboxylmethyltransferase-Based Therapy for Hutchinson-Gilford Progeria Syndrome.

Hutchinson–Gilford progeria syndrome (HGPS, progeria) is a rare genetic disease characterized by premature aging and death in childhood for which there were no approved drugs for its treatment until last November, when lonafarnib obtained long-sought FDA approval. However, the benefits of lonafarnib in patients are limited, highlighting the need for new therapeutic strategies. Here, we validate the enzyme isoprenylcysteine carboxylmethyltransferase (ICMT) as a new therapeutic target for progeria with the development of a new series of potent inhibitors of this enzyme that exhibit an excellent antiprogeroid profile. Among them, compound UCM-13207 significantly improved the main hallmarks of progeria. Specifically, treatment of fibroblasts from progeroid mice with UCM-13207 delocalized progerin from the nuclear membrane, diminished its total protein levels, resulting in decreased DNA damage, and increased cellular viability. Importantly, these effects were also observed in patient-derived cells. Using the LmnaG609G/G609G progeroid mouse model, UCM-13207 showed an excellent in vivo efficacy by increasing body weight, enhancing grip strength, extending lifespan by 20%, and decreasing tissue senescence in multiple organs. Furthermore, UCM-13207 treatment led to an improvement of key cardiovascular hallmarks such as reduced progerin levels in aortic and endocardial tissue and increased number of vascular smooth muscle cells (VSMCs). The beneficial effects go well beyond the effects induced by other therapeutic strategies previously reported in the field, thus supporting the use of UCM-13207 as a new treatment for progeria.

Effects of isoprenylcysteine carboxylmethyltransferase silencing on the migration and invasion of tongue squamous cell carcinoma.

The effect of isoprenylcysteine carboxymethyltransferase (ICMT) silencing on the migration and invasion of tongue squamous cell carcinoma was investigated by constructing the small interfering RNA (siRNA) of ICMT. Through liposomal transfection, siRNA was transfected into human tongue squamous cell carcinoma CAL-27 and SCC-4 cells (ICMT-siRNA group) with a negative control group (transfected with NC-siRNA) and a blank control group (transfected with a transfection reagent but not with siRNA). Quantitative real-time polymerase chain reaction was performed to analyze the mRNA expression of ICMT and RhoA in each group of cells after transfection and to measure the silencing efficiency. Western blot was applied to examine the expression levels of ICMT, total RhoA, membrane RhoA, ROCK1, matrix metalloproteinase (MMP)-2, and MMP-9 proteins in each group. The migration and invasion abilities were evaluated via wound healing and Transwell motility assays. After CAL-27 and SCC-4 cells were transfected with ICMT-siRNA, the expression levels of ICMT genes and proteins decreased significantly in the experimental group compared with those in the negative and blank control groups (P<0.05). The mRNA and total protein expression levels of RhoA in the two groups were not significantly different (P>0.05). The expression levels of RhoA membrane protein, ROCK1, MMP-2, and MMP-9 decreased (P<0.05). The migration and invasion abilities were inhibited (P<0.05). The migration and invasion abilities of CAL-27 and SCC-4 cells were reduced significantly after the transfection of ICMT-siRNA, and the involved mechanism might be related to the RhoA-ROCK signaling pathway.

MicroRNA-99a-5p suppresses cell proliferation, migration, and invasion by targeting isoprenylcysteine carboxylmethyltransferase in oral squamous cell carcinoma.

BackgroundMicroRNA (miR)-99a-5p acts as a tumor suppressor in several tumors, including bladder cancer and breast cancer, but its biological function in oral squamous cell carcinoma (OSCC) is poorly understood.MethodsmiR-99a-5p expression was determined in OSCC tissues and cell lines using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Cell proliferation was assessed by the Cell Counting Kit-8 assay and colony formation assay. Wound healing and Transwell assays were used to analyze migration and invasion abilities, respectively, in OSCC cells. The luciferase reporter assay, RT-qPCR, and western blotting were used to determine the relationship between miR-99a-5p and isoprenylcysteine carboxylmethyltransferase (ICMT).ResultsmiR-99a-5p expression in OSCC tissues and cell lines was significantly decreased compared with corresponding controls, and was significantly associated with clinical stage and lymph node metastasis in OSCC. Functional assays revealed that miR-99a-5p overexpression significantly inhibited the proliferation, migration, and invasion abilities of CAL-27 and TCA-8113 OSCC cells. miR-99a-5p was found to directly target ICMT, while ICMT restoration reversed the role of miR-99a-5p in OSCC cells.ConclusionsOur results indicate that miR-99a-5p-mediates the down-regulation of ICMT, which could be used as a novel potential therapeutic target for OSCC treatment.

ES28.01 Biology of KRAS Targeting Agents

ES28.01 Biology of KRAS Targeting Agents

NRAS is unique among RAS proteins in requiring ICMT for trafficking to the plasma membrane.

Isoprenylcysteine carboxyl methyltransferase (ICMT) is the third of three enzymes that sequentially modify the C-terminus of CaaX proteins, including RAS. Although all four RAS proteins are substrates for ICMT, each traffics to membranes differently by virtue of their hypervariable regions that are differentially palmitoylated. We found that among RAS proteins, NRAS was unique in requiring ICMT for delivery to the PM, a consequence of having only a single palmitoylation site as its secondary affinity module. Although not absolutely required for palmitoylation, acylation was diminished in the absence of ICMT. Photoactivation and FRAP of GFP-NRAS revealed increase flux at the Golgi, independent of palmitoylation, in the absence of ICMT. Association of NRAS with the prenyl-protein chaperone PDE6δ also required ICMT and promoted anterograde trafficking from the Golgi. We conclude that carboxyl methylation of NRAS is required for efficient palmitoylation, PDE6δ binding, and homeostatic flux through the Golgi, processes that direct delivery to the plasma membrane.

A small-molecule ICMT inhibitor delays senescence of Hutchinson-Gilford progeria syndrome cells.

A farnesylated and methylated form of prelamin A called progerin causes Hutchinson-Gilford progeria syndrome (HGPS). Inhibiting progerin methylation by inactivating the isoprenylcysteine carboxylmethyltransferase (ICMT) gene stimulates proliferation of HGPS cells and improves survival of Zmpste24-deficient mice. However, we don't know whether Icmt inactivation improves phenotypes in an authentic HGPS mouse model. Moreover, it is unknown whether pharmacologic targeting of ICMT would be tolerated by cells and produce similar cellular effects as genetic inactivation. Here, we show that knockout of Icmt improves survival of HGPS mice and restores vascular smooth muscle cell numbers in the aorta. We also synthesized a potent ICMT inhibitor called C75 and found that it delays senescence and stimulates proliferation of late-passage HGPS cells and Zmpste24-deficient mouse fibroblasts. Importantly, C75 did not influence proliferation of wild-type human cells or Zmpste24-deficient mouse cells lacking Icmt, indicating drug specificity. These results raise hopes that ICMT inhibitors could be useful for treating children with HGPS.

Effects of isoprenylcysteine carboxyl methyltransferase silencing on the proliferation and apoptosis of tongue squamous cell carcinoma.

This study aimed to explore the effects of silencing isoprenylcysteine carboxyl methyltransfe-rase (Icmt) through small interfering RNA (siRNA) interference on the proliferation and apoptosis of tongue squamous cell carcinoma (TSCC). Three siRNA were designed and constructed for the Icmt gene sequence and were then transfected into TSCC cells CAL-27 and SCC-4 to silence Icmt expression. The tested cells were divided as follows: RNA interference groups Icmt-siRNA-1, Icmt-siRNA-2, and Icmt-siRNA-3, negative control group, and blank control group. The transfection efficiency of siRNA was detected by the fluorescent group Cy3-labeled siRNA, and the expression of Icmt mRNA was screened by quantitive real-time polymerase chain reaction (qRT-PCR) selected the experimental group for subsequent experiments. The expression of Icmt, RhoA, Cyclin D1, p21, extracellular regulated protein kinases (ERK), and phospho-extracellular regulated protein kinases (p-ERK) were analyzed by Western blot. The proliferation abilities of TSCC cells were determined by cell counting kit-8 assay. The change in apoptosis was detected by AnnexinV-APC/propidium staining (PI) assay. Cell-cycle analysis was conducted by flow cytometry. The expression of Icmt mRNA and protein in TSCC cells significantly decreased after Icmt-siRNA transfection (P<0.05). No significant difference in RhoA mRNA and protein expression was detected (P>0.05), but the expression of RhoA membrane protein decreased compared with the negative control group and blank control groups (P<0.05). Cyclin D1 expression decreased, whereas p21 expression significantly increased and the relative expression of ERK protein in the experimental group did not significantly different that in the control group (P>0.05). However, the phosphorylation level of ERK was significantly reduced (P<0.05). The cell cycles of TSCC CAL-27 and SCC-4 were altered in G1/S, cell proliferation activity was inhibited, and apoptosis was induced (P<0.05). Silencing Icmt can effectively downregulate its expression in TSCC cells, reduce the RhoA membrane targeting localization and cell proliferation, and induce apoptosis. Thus, Icmt may be a potential gene therapy target for TSCC.

Isoprenylcysteine carboxyl methyltransferase inhibitors exerts anti-inflammatory activity

Isoprenylcysteine carboxylmethyltransferase (ICMT) has been reported to regulate the inflammatory response through the Ras/MAPK/AP-1 pathway. Nevertheless, the potential of ICMT inhibitors as therapeutic agents against inflammatory diseases has not been examined. Therefore, in this study, we investigated the anti-inflammatory properties of two ICMT inhibitors, cysmethynil (CyM) and 3-methoxy-N-[2–2,2,6,6-tetramethyl-4-phenyltetrahydropyran-4-yl)ethyl]aniline (MTPA), using in vitro analyses and in vivo analyses (lipopolysaccharide (LPS)/D-GalN-triggered hepatitis and DSS-induced colitis mouse models). CyM and MTPA inhibited the production of nitric oxide (NO) and prostaglandin E (PGE)2 and the expression of cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α and interleukin (IL)-1β in LPS-induced RAW264.7 cells and peritoneal macrophages without cytotoxicity. CyM also reduced AP-1-mediated luciferase activity in LPS-stimulated RAW264.7 cells and MyD88- and TRIF-expressing HEK293 cells. In addition, CyM and MTPA suppressed the translocation of Ras to the cell membrane and ER as well as phosphorylation of Ras-dependent AP-1 signaling molecules including Raf, MEK1/2, ERK p38, and JNK. Consistent with these results, CyM diminished the expression of inflammatory genes (COX-2, TNF-α, IL-1β, and IL-6), AP-1-Luc activity, and phosphorylation of Ras-mediated signaling enzymes in Ras-overexpressing HEK 293 cells. Moreover, CyM and MTPA ameliorated symptoms of hepatitis and colitis in mice and restrained the ICMT/Ras-dependent AP-1 pathway in inflammatory lesions of the mouse model systems. Taken together, our results indicate that CyM and MTPA alleviate the LPS-induced ICMT/Ras/AP-1 signaling pathway, thereby inhibiting the inflammatory response as promising anti-inflammatory drugs.

Isoprenylcysteine carboxylmethyltransferase is required for the impact of mutant KRAS on TAZ protein level and cancer cell self-renewal

Cancer stem cells possess the capacity for self-renewal and resistance to chemotherapy. It is therefore crucial to understand the molecular regulators of stemness in the quest to develop effective cancer therapies. TAZ is a transcription activator that promotes stem cell functions in post-development mammalian cells; suppression of TAZ activity reduces or eliminates cancer stemness in select cancers. Isoprenylcysteine carboxylmethyltransferase (ICMT) is the unique enzyme of the last step of posttranslational prenylation processing pathway that modifies several oncogenic proteins, including RAS. We found that suppression of ICMT results in reduced self-renewal/stemness in KRAS-driven pancreatic and breast cancer cells. Silencing of ICMT led to significant reduction of TAZ protein levels and loss of self-renewal ability, which could be reversed by overexpressing mutant KRAS, demonstrating the functional impact of ICMT modification on the ability of KRAS to control TAZ stability and function. Contrary to expectation, YAP protein levels appear to be much less susceptible than TAZ to the regulation by ICMT and KRAS, and YAP is less consequential in regulating stemness characteristics in these cells. Further, we found that the ICMT-dependent KRAS regulation of TAZ was mediated through RAF, but not PI3K, signaling. Functionally, we demonstrate that a signaling cascade from ICMT modification of KRAS to TAZ protein stability supports cancer cell self-renewal abilities in both in vitro and in vivo settings. In addition, studies using the proof-of-concept small molecule inhibitors of ICMT confirmed its role in regulating TAZ and self-renewal, demonstrating the potential utility of targeting ICMT to control aggressive KRAS-driven cancers.

Isoprenylcysteine Carboxyl Methyltransferase and Its Substrate Ras Are Critical Players Regulating TLR-Mediated Inflammatory Responses.

In this study, we investigated the functional role of isoprenylcysteine carboxyl methyltransferase (ICMT) and its methylatable substrate Ras in Toll-like receptor (TLR)-activated macrophages and in mouse inflammatory disease conditions. ICMT and RAS expressions were strongly increased in macrophages under the activation conditions of TLRs by lipopolysaccharide (LPS, a TLR4 ligand), pam3CSK (TLR2), or poly(I:C) (TLR3) and in the colons, stomachs, and livers of mice with colitis, gastritis, and hepatitis. The inhibition and activation of ICMT and Ras through genetic and pharmacological approaches significantly affected the activation of interleukin-1 receptor-associated kinase (IRAK)s, tumor necrosis factor receptor associated factor 6 (TRAF6), transforming growth factor-β-activated kinase 1 (TAK1), mitogen-activated protein kinase (MAPK), and MAPK kinases (MAPKKs); translocation of the AP-1 family; and the expressions of inflammation-related genes that depend on both MyD88 and TRIF. Interestingly, the Ras/ICMT-mediated inflammatory reaction critically depends on the TIR domains of myeloid differentiation primary response 88 (MyD88) and TIR-domain-containing adapter-inducing interferon-β (TRIF). Taken together, these results suggest that ICMT and its methylated Ras play important roles in the regulation of inflammatory responses through cooperation with the TIR domain of adaptor molecules.