Suppression of lung cancer tumor growth in a nude mouse model by the Ras inhibitor salirasib (farnesylthiosalicylic acid)

Ras inhibitor farnesylthiosalicylic acid conjugated with IR783 dye exhibits improved tumor-targeting and altered anti-breast cancer mechanisms in mice

Ras has long been viewed as a promising target for cancer therapy. Farnesylthiosalicylic acid (FTS), as the only Ras inhibitor has ever entered phase II clinical trials, has yielded disappointing results due to its strong hydrophobicity, poor tumor-targeting capacity, and low therapeutic efficiency. Thus, enhancing hydrophilicity and tumor-targeting capacity of FTS for improving its therapeutic efficacy is of great significance. In this study we conjugated FTS with a cancer-targeting small molecule dye IR783 and characterized the anticancer properties of the conjugate FTS-IR783. We showed that IR783 conjugation greatly improved the hydrophilicity, tumor-targeting and therapeutic potential of FTS. After a single oral administration in Balb/c mice, the relative bioavailability of FTS-IR783 was increased by 90.7% compared with FTS. We demonstrated that organic anion transporting polypeptide (OATP) and endocytosis synergistically drove the uptake of the FTS-IR783 conjugate in breast cancer MDA-MB-231 cells, resulting in superior tumor-targeting ability of the conjugate both in vitro and in vivo. We further revealed that FTS-IR783 conjugate could bind with and directly activate AMPK rather than affecting Ras, and subsequently regulate the TSC2/mTOR signaling pathway, thus achieving 2-10-fold increased anti-cancer therapeutic efficacy against 6 human breast cancer cell lines compared to FTS both in vivo and in vitro. Overall, our data highlights a promising approach for the modification of the anti-tumor drug FTS using IR783 and makes it possible to return FTS back to the clinic with a better efficacy.

Targeting KRAS in NSCLC: Old Failures and New Options for "Non-G12c" Patients

Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) gene mutations are among the most common driver alterations in non-small cell lung cancer (NSCLC). Despite their high frequency, valid treatment options are still lacking, mainly due to an intrinsic complexity of both the protein structure and the downstream pathway. The increasing knowledge about different mutation subtypes and co-mutations has paved the way to several promising therapeutic strategies. Despite the best results so far having been obtained in patients harbouring KRAS exon 2 p.G12C mutation, even the treatment landscape of non-p.G12C KRAS mutation positive patients is predicted to change soon. This review provides a comprehensive and critical overview of ongoing studies into NSCLC patients with KRAS mutations other than p.G12C and discusses future scenarios that will hopefully change the story of this disease.

Inhibition of ERAD synergizes with FTS to eradicate pancreatic cancer cells

Background

Pancreatic ductal adenocarcinoma (PDAC), one of the most lethal cancers, is driven by oncogenic KRAS mutations. Farnesyl thiosalicylic acid (FTS), also known as salirasib, is a RAS inhibitor that selectively dislodges active RAS proteins from cell membrane, inhibiting downstream signaling. FTS has demonstrated limited therapeutic efficacy in PDAC patients despite being well tolerated.

Methods

To improve the efficacy of FTS in PDAC, we performed a genome-wide CRISPR synthetic lethality screen to identify genetic targets that synergize with FTS treatment. Among the top candidates, multiple genes in the endoplasmic reticulum-associated protein degradation (ERAD) pathway were identified. The role of ERAD inhibition in enhancing the therapeutic efficacy of FTS was further investigated in pancreatic cancer cells using pharmaceutical and genetic approaches.

Results

In murine and human PDAC cells, FTS induced unfolded protein response (UPR), which was further augmented upon treatment with a chemical inhibitor of ERAD, Eeyarestatin I (EerI). Combined treatment with FTS and EerI significantly upregulated the expression of UPR marker genes and induced apoptosis in pancreatic cancer cells. Furthermore, CRISPR-based genetic ablation of the key ERAD components, HRD1 and SEL1L, sensitized PDAC cells to FTS treatment.

Conclusion

Our study reveals a critical role for ERAD in therapeutic response of FTS and points to the modulation of UPR as a novel approach to improve the efficacy of FTS in PDAC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07967-6.

Targeting KRAS mutant cancers by preventing signaling transduction in the MAPK pathway

KRAS genes are the most commonly mutated oncogenes in cancer. Unfortunately, effective therapeutic strategies for targeting KRAS mutant cancers have proven to be difficult to obtain. A key reason for this setback is due to the lack of success direct KRAS mutant inhibitors have received. Researchers have turned their efforts away from targeting the KRAS nucleotide-binding site directly and towards targeting other areas of the MAPK signaling pathway to block KRAS function. Researchers found that inhibiting enzymes and protein-protein interactions involved in the MAPK signaling pathway inhibit the activation of KRAS mutant therefore can lead to a potential therapeutic for KRAS mutated cancers. Throughout the past two decades, various indirect inhibitors have been designed and tested. EGFR and MEK inhibitors have presented with less success; however, significant advances have been made when targeting the plasma membrane localization process and the allosteric site of KRAS mutant. Farnesyltransferase and allosteric inhibitors have both advanced to human clinical trials. This comprehensive review presents the most recent developments of direct and indirect KRAS mutant inhibitors. This review summarizes published data on the inhibitory and anti-cancer activity of compounds that target KRAS activation as well as highlights the most promising strategies for targeting KRAS mutant cancers.

KRAS inhibition in non-small cell lung cancer: Past failures, new findings and upcoming challenges

Despite the high prevalence of Kirsten rat sarcoma (KRAS) mutations in non-small cell lung cancer (NSCLC), for a long time it has been defined as an 'undruggable target', with precision medicine not considered as an adequate approach to treat this subgroup of patients. After several years of efforts, preliminary data from early clinical trials have recently demonstrated that direct pharmacological inhibition of KRAS p.G12C mutation is possible, emerging as an effective targeted treatment for about 10-12% of patients with advanced NSCLC, with potential relevant impact on their long-term survival and quality of life. This review reports the current status of KRAS mutations detection in the Italian real-word scenario, summarises the biological basis of KRAS inhibition in NSCLC and provides an updated overview of therapeutic strategies, discussing the potential reasons for past failures and analysing the upcoming challenges related to the advent of new targeted agents in clinical practice.

Targeting KRAS Mutant Non-Small-Cell Lung Cancer: Past, Present and Future

Lung cancer is the most frequent cancer with an aggressive clinical course and high mortality rates. Most cases are diagnosed at advanced stages when treatment options are limited and the efficacy of chemotherapy is poor. The disease has a complex and heterogeneous background with non-small-cell lung cancer (NSCLC) accounting for 85% of patients and lung adenocarcinoma being the most common histological subtype. Almost 30% of adenocarcinomas of the lung are driven by an activating Kirsten rat sarcoma viral oncogene homolog (KRAS) mutation. The ability to inhibit the oncogenic KRAS has been the holy grail of cancer research and the search for inhibitors is immensely ongoing as KRAS-mutated tumors are among the most aggressive and refractory to treatment. Therapeutic strategies tailored for KRAS+ NSCLC rely on the blockage of KRAS functional output, cellular dependencies, metabolic features, KRAS membrane associations, direct targeting of KRAS and immunotherapy. In this review, we provide an update on the most recent advances in anti-KRAS therapy for lung tumors with mechanistic insights into biological diversity and potential clinical implications.

Drugging the Small GTPase Pathways in Cancer Treatment: Promises and Challenges

Small GTPases are a family of low molecular weight GTP-hydrolyzing enzymes that cycle between an inactive state when bound to GDP and an active state when associated to GTP. Small GTPases regulate key cellular processes (e.g., cell differentiation, proliferation, and motility) as well as subcellular events (e.g., vesicle trafficking), making them key participants in a great array of pathophysiological processes. Indeed, the dysfunction and deregulation of certain small GTPases, such as the members of the Ras and Arf subfamilies, have been related with the promotion and progression of cancer. Therefore, the development of inhibitors that target dysfunctional small GTPases could represent a potential therapeutic strategy for cancer treatment. This review covers the basic biochemical mechanisms and the diverse functions of small GTPases in cancer. We also discuss the strategies and challenges of inhibiting the activity of these enzymes and delve into new approaches that offer opportunities to target them in cancer therapy.

Epidermal growth factor receptor controls glycogen phosphorylase in T cells through small GTPases of the RAS family

We recently uncovered a regulatory pathway of the muscle isoform of glycogen phosphorylase (PYGM) that plays an important role in regulating immune function in T cells. Here, using various enzymatic, pulldown, and immunoprecipitation assays, we describe signaling cross-talk between the small GTPases RAS and RAP1A, member of RAS oncogene family (RAP1) in human Kit 225 lymphoid cells, which, in turn, is regulated by the epidermal growth factor receptor (EGFR). We found that this communication bridge is essential for glycogen phosphorylase (PYG) activation through the canonical pathway because this enzyme is inactive in the absence of adenylyl cyclase type 6 (ADCY6). PYG activation required stimulation of both exchange protein directly activated by cAMP 2 (EPAC2) and RAP1 via RAS and ADCY6 phosphorylation, with the latter being mediated by Raf-1 proto-oncogene, Ser/Thr kinase (RAF1). Consistent with this model, PYG activation was EGFR-dependent and may be initiated by the constitutively active form of RAS. Consequently, PYG activation in Kit 225 T cells could be blocked with specific inhibitors of RAS, EPAC, RAP1, RAF1, ADCY6, and cAMP-dependent protein kinase. Our results establish a new paradigm for the mechanism of PYG activation, which depends on the type of receptor involved.

RASpecting the oncogene: New pathways to therapeutic advances

RAS is the most commonly mutated driver of tumorigenesis, seen in about 30% of all cancer cases. There is a subset of tumors termed RAS-driven cancers in which RAS mutation or overactivation is evident, including as much as 95% in pancreatic and 50% in colon cancer. RAS is a family of small membrane bound GTPases that act as a signaling node to control both normal and cancer biology. Since the discovery of RAS' overall prominence in many tumor types and specifically in RAS-dependent cancers, it has been an obvious therapeutic target for drug development. However, RAS has proved a very elusive target, and after a few prominent RAS targeted drugs failed in clinical trials after decades of research, RAS was termed "undruggable" and research in this field was greatly hampered. An increase in knowledge about basic RAS biology has led to a resurgence in the generation of novel therapeutics targeting RAS signaling utilizing various and distinct approaches. These new drugs target RAS activation directly, block downstream signaling effectors and inhibit proper post-translational processing and trafficking/recycling of RAS. This review will cover how these new drugs were developed and how they have fared in preclinical and early phase clinical trials.

HRAS as a potential therapeutic target of salirasib RAS inhibitor in bladder cancer

The active form of the small GTPase RAS binds to downstream effectors to promote cell growth and proliferation. RAS signal enhancement contributes to tumorigenesis, invasion, and metastasis in various different cancers. HRAS proto-oncogene GTPase (HRAS), one of the RAS isoforms, was the first human oncogene for which mutations were reported in T24 bladder cancer (BC) cells in 1982, and HRAS mutation or upregulation has been reported in several cancers. According to data from The Cancer Genome Atlas, HRAS expression was significantly upregulated in clinical BC samples compared to healthy samples (P=0.0024). HRAS expression was also significantly upregulated in BC with HRAS mutation compared to patients without HRAS mutation (P<0.0001). The tumor suppressive effect of salirasib, a RAS inhibitor, has been reported in several cancer types, but only at relatively high concentrations. As such, RAS inhibitors have not been used for clinical applications. The aim of the current study was to investigate the therapeutic potential of targeting HRAS using salirasib and small interfering RNA (siRNA) and to characterize the mechanism by which HRAS functions using recently developed quantitative in vitro proteome-assisted multiple reaction monitoring for protein absolute quantification (iMPAQT), in BC cells. iMPAQT allows measurement of the absolute abundance of any human protein with the high quantitative accuracy. Salirasib and siRNA targeting of HRAS inhibited cell proliferation, migration and invasion in HRAS wild type and HRAS-mutated cell lines. Proteomic analyses revealed that several metabolic pathways, including the oxidative phosphorylation pathway and glycolysis, were significantly downregulated in salirasib-treated BC cells. However, the expression levels of hexokinase 2, phosphoglycerate kinase 1, pyruvate kinase, muscle (PKM)1, PKM2 and lactate dehydrogenase A, which are downstream of RAS and target genes of hypoxia inducible factor-1α, were not notably downregulated, which may explain the high concentration of salirasib required to inhibit cell viability. These findings provide insight into the mechanisms of salirasib, and suggest the need for novel therapeutic strategies to treat cancers such as BC.

MSH2/BRCA1 expression as a DNA-repair signature predicting survival in early-stage lung cancer patients from the IFCT-0002 Phase 3 Trial

Introduction

DNA repair is a double-edged sword in lung carcinogenesis. When defective, it promotes genetic instability and accumulated genetic alterations. Conversely these defects could sensitize cancer cells to therapeutic agents inducing DNA breaks.

Methods

We used immunohistochemistry (IHC) to assess MSH2, XRCC5, and BRCA1 expression in 443 post-chemotherapy specimens from patients randomized in a Phase 3 trial, comparing two neoadjuvant regimens in 528 Stage I-II non-small cell lung cancer (NSCLC) patients (IFCT-0002). O6MGMT promoter gene methylation was analyzed in a subset of 208 patients of the same trial with available snap-frozen specimens.

Results

Median follow-up was from 90 months onwards. Only high BRCA1 (n = 221, hazard ratio [HR] = 1.58, 95% confidence interval [CI] [1.07-2.34], p = 0.02) and low MSH2 expression (n = 356, HR = 1.52, 95% CI [1.11-2.08], p = 0.008) significantly predicted better overall survival (OS) in univariate and multivariate analysis. A bootstrap re-sampling strategy distinguished three patient groups at high (n = 55, low BRCA1 and high MSH2, median OS >96 months, HR = 2.5, 95% CI [1.45-4.33], p = 0.001), intermediate (n = 82, median OS = 73.4 p = 0.0596), and low (high BRCA1 and low MSH2, n = 67, median OS = ND, HR = 0.51, 95% CI [0.31-0.83], p = 0.006) risk of death.

Interpretation

DNA repair protein expression assessment identified three different groups of risk of death in early-stage lung cancer patients, according to their tumor MSH2 and BRCA1 expression levels. These results deserve prospective evaluation of MSH2/BRCA1 theranostic value in lung cancer patients treated with combinations of DNA-damaging chemotherapy and drugs targeting DNA repair, such as Poly(ADP-ribose) polymerase (PARP) inhibitors.

KRAS oncogene in non-small cell lung cancer: clinical perspectives on the treatment of an old target

Lung neoplasms are the leading cause of death by cancer worldwide. Non-small cell lung cancer (NSCLC) constitutes more than 80% of all lung malignancies and the majority of patients present advanced disease at onset. However, in the last decade, multiple oncogenic driver alterations have been discovered and each of them represents a potential therapeutic target. Although KRAS mutations are the most frequently oncogene aberrations in lung adenocarcinoma patients, effective therapies targeting KRAS have yet to be developed. Moreover, the role of KRAS oncogene in NSCLC remains unclear and its predictive and prognostic impact remains controversial. The study of the underlying biology of KRAS in NSCLC patients could help to determine potential candidates to evaluate novel targeted agents and combinations that may allow a tailored treatment for these patients. The aim of this review is to update the current knowledge about KRAS-mutated lung adenocarcinoma, including a historical overview, the biology of the molecular pathways involved, the clinical relevance of KRAS mutations as a prognostic and predictive marker and the potential therapeutic approaches for a personalized treatment of KRAS-mutated NSCLC patients.

Implications of KRAS mutations in acquired resistance to treatment in NSCLC

Rationale

KRAS is the most common and, simultaneously, the most ambiguous oncogene implicated in human cancer. Despite KRAS mutations were identified in Non Small Cell Lung Cancers (NSCLCs) more than 20 years ago, selective and specific inhibitors aimed at directly abrogating KRAS activity are not yet available. Nevertheless, many therapeutic approaches have been developed potentially useful to treat NSCLC patients mutated for KRAS and refractory to both standard chemotherapy and targeted therapies.

The focus of this review will be to provide an overview of the network related to the intricate molecular KRAS pathways, stressing on preclinical and clinical studies that investigate the predictive value of KRAS mutations in NSCLC patients.

Materials and Methods

A bibliographic search of the Medline database was conducted for articles published in English, with the keywords KRAS, KRAS mutations in non-small cell lung cancer, KRAS and tumorigenesis, KRAS and TKIs, KRAS and chemotherapy, KRAS and monoclonal antibody, KRAS and immunotherapy, KRAS and drugs, KRAS and drug resistance.

A potential non-invasive glioblastoma treatment: Nose-to-brain delivery of farnesylthiosalicylic acid incorporated hybrid nanoparticles

New drug delivery systems are highly needed in research and clinical area to effectively treat gliomas by reaching a high antineoplastic drug concentration at the target site without damaging healthy tissues. Intranasal (IN) administration, an alternative route for non-invasive drug delivery to the brain, bypasses the blood-brain-barrier (BBB) and eliminates systemic side effects. This study evaluated the antitumor efficacy of farnesylthiosalicylic acid (FTA) loaded (lipid-cationic) lipid-PEG-PLGA hybrid nanoparticles (HNPs) after IN application in rats. FTA loaded HNPs were prepared, characterized and evaluated for cytotoxicity. Rat glioma 2 (RG2) cells were implanted unilaterally into the right striatum of female Wistar rats. 10days later, glioma bearing rats received either no treatment, or 5 repeated doses of 500μM freshly prepared FTA loaded HNPs via IN or intravenous (IV) application. Pre-treatment and post-treatment tumor sizes were determined with MRI. After a treatment period of 5days, IN applied FTA loaded HNPs achieved a significant decrease of 55.7% in tumor area, equal to IV applied FTA loaded HNPs. Herewith, we showed the potential utility of IN application of FTA loaded HNPs as a non-invasive approach in glioblastoma treatment.

Farnesylthiosalicylic acid sensitizes hepatocarcinoma cells to artemisinin derivatives

Dihydroartemisinin (DHA) and artesunate (ARS), two artemisinin derivatives, have efficacious anticancer activities against human hepatocarcinoma (HCC) cells. This study aims to study the anticancer action of the combination treatment of DHA/ARS and farnesylthiosalicylic acid (FTS), a Ras inhibitor, in HCC cells (Huh-7 and HepG2 cell lines). FTS pretreatment significantly enhanced DHA/ARS-induced phosphatidylserine (PS) externalization, Bak/Bax activation, mitochondrial membrane depolarization, cytochrome c release, and caspase-8 and -9 activations, characteristics of the extrinsic and intrinsic apoptosis. Pretreatment with Z-IETD-FMK (caspase-8 inhibitor) potently prevented the cytotoxicity of the combination treatment of DHA/ARS and FTS, and pretreatment with Z-VAD-FMK (pan-caspase inhibitor) significantly inhibited the loss of ΔΨm induced by DHA/ARS treatment or the combination treatment of DHA/ARS and FTS in HCC cells. Furthermore, silencing Bak/Bax modestly but significantly inhibited the cytotoxicity of the combination treatment of DHA/ARS and FTS. Interestingly, pretreatment with an antioxidant N-Acetyle-Cysteine (NAC) significantly prevented the cytotoxicity of the combination treatment of DHA and FTS instead of the combination treatment of ARS and FTS, suggesting that reactive oxygen species (ROS) played a key role in the anticancer action of the combination treatment of DHA and FTS. Similar to FTS, DHA/ARS also significantly prevented Ras activation. Collectively, our data demonstrate that FTS potently sensitizes Huh-7 and HepG2 cells to artemisinin derivatives via accelerating the extrinsic and intrinsic apoptotic pathways.

Gemcitabine Mechanism of Action Confounds Early Assessment of Treatment Response by 3'-Deoxy-3'-[18F]Fluorothymidine in Preclinical Models of Lung Cancer

3'-Deoxy-3'-[18F]fluorothymidine positron emission tomography ([18F]FLT-PET) and diffusion-weighted MRI (DW-MRI) are promising approaches to monitor tumor therapy response. Here, we employed these two imaging modalities to evaluate the response of lung carcinoma xenografts in mice after gemcitabine therapy. Caliper measurements revealed that H1975 xenografts responded to gemcitabine treatment, whereas A549 growth was not affected. In both tumor models, uptake of [18F]FLT was significantly reduced 6 hours after drug administration. On the basis of the gemcitabine concentration and [18F]FLT excretion measured, this was presumably related to a direct competition of gemcitabine with the radiotracer for cellular uptake. On day 1 after therapy, [18F]FLT uptake was increased in both models, which was correlated with thymidine kinase 1 (TK1) expression. Two and 3 days after drug administration, [18F]FLT uptake as well as TK1 and Ki67 expression were unchanged. A reduction in [18F]FLT in the responsive H1975 xenografts could only be noted on day 5 of therapy. Changes in ADCmean in A549 xenografts 1 or 2 days after gemcitabine did not seem to be of therapy-related biological relevance as they were not related to cell death (assessed by caspase-3 IHC and cellular density) or tumor therapy response. Taken together, in these models, early changes of [18F]FLT uptake in tumors reflected mechanisms, such as competing gemcitabine uptake or gemcitabine-induced thymidylate synthase inhibition, and only reflected growth-inhibitory effects at a later time point. Hence, the time point for [18F]FLT-PET imaging of tumor response to gemcitabine is of crucial importance. Cancer Res; 76(24); 7096-105. ©2016 AACR.

Targeting the KRAS Pathway in Non-Small Cell Lung Cancer

: Lung cancer remains the leading cause of cancer-related deaths worldwide. However, significant progress has been made individualizing therapy based on molecular aberrations (e.g., EGFR, ALK) and pathologic subtype. KRAS is one of the most frequently mutated genes in non-small cell lung cancer (NSCLC), found in approximately 30% of lung adenocarcinomas, and is thus an appealing target for new therapies. Although no targeted therapy has yet been approved for the treatment of KRAS-mutant NSCLC, there are multiple potential therapeutic approaches. These may include direct inhibition of KRAS protein, inhibition of KRAS regulators, alteration of KRAS membrane localization, and inhibition of effector molecules downstream of mutant KRAS. This article provides an overview of the KRAS pathway in lung cancer and related therapeutic strategies under investigation.

IMPLICATIONS FOR PRACTICE

The identification of oncogene-addicted cancers and specific inhibitors has revolutionized non-small cell lung cancer (NSCLC) treatment and outcomes. One of the most commonly mutated genes in adenocarcinoma is KRAS, found in approximately 30% of lung adenocarcinomas, and thus it is an appealing target for new therapies. This review provides an overview of the KRAS pathway and related targeted therapies under investigation in NSCLC. Some of these agents may play a key role in KRAS-mutant NSCLC treatment in the future.

6-C-(E-phenylethenyl)naringenin induces cell growth inhibition and cytoprotective autophagy in colon cancer cells

6-C-(E-phenylethenyl)naringenin (6-CEPN) is a small molecule found in naringenin fortified fried beef. It has been shown to suppress colon cancer cell proliferation, but the underlying mechanisms are not fully understood. Here we demonstrate that 6-CEPN suppresses tumour cell proliferation through cell cycle arrest in G1 phase, induces necrotic cell death and autophagy in colon cancer cells. Blockade of autophagy by knockdown of the essential autophagy proteins, Atg7 or beclin-1, resulted in aggravated cell death in response to 6-CEPN treatment. In addition, genome-wide transcriptome expression profiling by RNA-sequencing revealed that 6-CEPN-mediated gene expression pattern was extremely similar to the transcriptome response induced by a RAS inhibitor salirasib (farnesylthiosalicylic acid [FTS; salirasib]). Subsequent molecular biological and biochemical experiments demonstrated that 6-CEPN indeed strongly inhibited RAS activation, leading to the inhibition of the downstream effector pathways c-Raf/mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase kinase and phosphoinositide 3-kinase/AKT/mammalian target of rapamycin. More importantly, our computational molecular docking data showed that 6-CEPN could bind to the active site of isoprenylcysteine carboxyl methyltransferase (Icmt), a critical enzyme for the activation of RAS. Icmt activity assay showed that 6-CEPN inhibited its activity significantly. Knockdown of Icmt by siRNA attenuated 6-CEPN-mediated autophagy and cell death. The present study demonstrates that 6-CEPN induces cell growth inhibition and cytoprotective autophagy in colon cancer cells, at least in part, though inhibition of the Icmt/RAS signalling pathways.

Bronchial Artery Angiogenesis Drives Lung Tumor Growth

Angiogenesis is vital for tumor growth but in well-vascularized organs such as the lung its importance is unclear. This situation is complicated by the fact that the lung has two separate circulations, the pulmonary and the systemic bronchial circulation. There are few relevant animal models of non-small cell lung cancer, which can be used to study the lung's complex circulations, and mice, lacking a systemic bronchial circulation cannot be used. We report here a novel orthotopic model of non-small cell lung cancer in rats, where we have studied the separate contributions of each of the two circulations for lung tumor growth. Results show that bronchial artery perfusion, quantified by fluorescent microspheres (206% increase in large tumors) or high-resolution computed tomography scans (276% increase in large tumors), parallels the growth in tumor volume, whereas pulmonary artery perfusion remained unchanged. Ablation of the bronchial artery after the initiation of tumor growth resulted in a decrease in tumor volume over a subsequent course of 4 weeks. These results demonstrate that although the existing pulmonary circulation can supply the metabolic needs for tumor initiation, further growth of the tumor requires angiogenesis from the highly proliferative bronchial circulation. This model may be useful to investigate new therapeutic approaches that target specifically the bronchial circulation. Cancer Res; 76(20); 5962-9. ©2016 AACR.

Computational allosteric ligand binding site identification on Ras proteins

A number of computational techniques have been proposed to expedite the process of allosteric ligand binding site identification in inherently flexible and hence challenging drug targets. Some of these techniques have been instrumental in the discovery of allosteric ligand binding sites on Ras proteins, a group of elusive anticancer drug targets. This review provides an overview of these techniques and their application to Ras proteins. A summary of molecular docking and binding site identification is provided first, followed by a more detailed discussion of two specific techniques for binding site identification in ensembles of Ras conformations generated by molecular simulations.

ATP promotes cell survival via regulation of cytosolic [Ca2+] and Bcl-2/Bax ratio in lung cancer cells

Adenosine triphosphate (ATP) is a ubiquitous extracellular messenger elevated in the tumor microenvironment. ATP regulates cell functions by acting on purinergic receptors (P2X and P2Y) and activating a series of intracellular signaling pathways. We examined ATP-induced Ca(2+) signaling and its effects on antiapoptotic (Bcl-2) and proapoptotic (Bax) proteins in normal human airway epithelial cells and lung cancer cells. Lung cancer cells exhibited two phases (transient and plateau phases) of increase in cytosolic [Ca(2+)] ([Ca(2+)]cyt) caused by ATP, while only the transient phase was observed in normal cells. Removal of extracellular Ca(2+) eliminated the plateau phase increase of [Ca(2+)]cyt in lung cancer cells, indicating that the plateau phase of [Ca(2+)]cyt increase is due to Ca(2+) influx. The distribution of P2X (P2X1-7) and P2Y (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11) receptors was different between lung cancer cells and normal cells. Proapoptotic P2X7 was nearly undetectable in lung cancer cells, which may explain why lung cancer cells showed decreased cytotoxicity when treated with high concentration of ATP. The Bcl-2/Bax ratio was increased in lung cancer cells following treatment with ATP; however, the antiapoptotic protein Bcl-2 demonstrated more sensitivity to ATP than proapoptotic protein Bax. Decreasing extracellular Ca(2+) or chelating intracellular Ca(2+) with BAPTA-AM significantly inhibited ATP-induced increase in Bcl-2/Bax ratio, indicating that a rise in [Ca(2+)]cyt through Ca(2+) influx is the critical mediator for ATP-mediated increase in Bcl-2/Bax ratio. Therefore, despite high ATP levels in the tumor microenvironment, which would induce cell apoptosis in normal cells, the decreased P2X7 and elevated Bcl-2/Bax ratio in lung cancer cells may enable tumor cells to survive. Increasing the Bcl-2/Bax ratio by exposure to high extracellular ATP may, therefore, be an important selective pressure promoting transformation and cancer progression.

Highly porous drug-eluting structures: from wound dressings to stents and scaffolds for tissue regeneration

For many biomedical applications, there is need for porous implant materials. The current article focuses on a method for preparation of drug-eluting porous structures for various biomedical applications, based on freeze drying of inverted emulsions. This fabrication process enables the incorporation of any drug, to obtain an "active implant" that releases drugs to the surrounding tissue in a controlled desired manner. Examples for porous implants based on this technique are antibiotic-eluting mesh/matrix structures used for wound healing applications, antiproliferative drug-eluting composite fibers for stent applications and local cancer treatment, and protein-eluting films for tissue regeneration applications. In the current review we focus on these systems. We show that the release profiles of both types of drugs, water-soluble and water-insoluble, are affected by the emulsion's formulation parameters. The former's release profile is affected mainly through the emulsion stability and the resulting porous microstructure, whereas the latter's release mechanism occurs via water uptake and degradation of the host polymer. Hence, appropriate selection of the formulation parameters enables to obtain desired controllable release profile of any bioactive agent, water-soluble or water-insoluble, and also fit its physical properties to the application.

Interplay Between HGF/SF-Met-Ras Signaling, Tumor Metabolism and Blood Flow as a Potential Target for Breast Cancer Therapy

High glucose uptake and increase blood flow is a characteristic of most metastatic tumors. Activation of Ras signaling increases glycolytic flux into lactate, de novo nucleic acid synthesis and uncoupling of ATP synthase from the proton gradient. Met tyrosine kinase receptor signaling upon activation by its ligand, hepatocyte growth factor/scatter factor (HGF/SF), increases glycolysis, oxidative phosporylation, oxygen consumption, and tumor blood volume. Ras is a key factor in Met signaling. Using the Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS), we investigated interplay between HGF/SF-Met–Ras signaling, metabolism, and tumor blood-flow regulation.

In vitro, HGF/SF-activated Met increased Ras activity, Erk phosphorylation, cell motility and glucose uptake, but did not affect ATP. FTS inhibited basal and HGF/SF-induced signaling and cell motility, while further increasing glucose uptake and inhibiting ATP production. In vivo, HGF/SF rapidly increased tumor blood volume. FTS did not affect basal blood-flow but abolished the HGF/SF effect.

Our results further demonstrate the complex interplay between growth-factor-receptor signaling and cellular and tumor metabolism, as reflected in blood flow. Inhibition of Ras signaling does not affect glucose consumption or basal tumor blood flow but dramatically decreases ATP synthesis and the HGF/SF induced increase in tumor blood volume. These findings demonstrate that the HGF/SF-Met–Ras pathway critically influences tumor-cell metabolism and tumor blood-flow regulation. This pathway could potentially be used to individualize tumor therapy based on functional molecular imaging, and for combined signaling/anti-metabolic targeted therapy.

Disrupting the oncogenic synergism between nucleolin and Ras results in cell growth inhibition and cell death

BACKGROUND

The ErbB receptors, Ras proteins and nucleolin are major contributors to malignant transformation. The pleiotropic protein nucleolin can bind to both Ras protein and ErbB receptors. Previously, we have demonstrated a crosstalk between Ras, nucleolin and the ErbB1 receptor. Activated Ras facilitates nucleolin interaction with ErbB1 and stabilizes ErbB1 levels. The three oncogenes synergistically facilitate anchorage independent growth and tumor growth in nude mice.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study we used several cancer cell lines. The effect of Ras and nucleolin inhibition was determined using cell growth, cell death and cell motility assays. Protein expression was determined by immunohistochemistry. We found that inhibition of Ras and nucleolin reduces tumor cell growth, enhances cell death and inhibits anchorage independent growth. Our results reveal that the combined treatment affects Ras and nucleolin levels and localization. Our study also indicates that Salirasib (FTS, Ras inhibitor) reduces cell motility, which is not affected by the nucleolin inhibitor.

CONCLUSIONS/SIGNIFICANCE

These results suggest that targeting both nucleolin and Ras may represent an additional avenue for inhibiting cancers driven by these oncogenes.

Ras inhibition enhances autophagy, which partially protects cells from death

Autophagy, a process of regulated turnover of cellular constituents, is essential for normal growth control but may be defective under pathological conditions. The Ras/PI3K/mTOR signaling pathway negatively regulates autophagy. Ras signaling has been documented in a large number of human cancers. In this in-vitro study we examined the effect of the Ras inhibitor Salirasib (S-trans, trans-farnesylthiosalicylic acid; FTS) on autophagy induction and cell viability. We show that Ras inhibition by FTS induced autophagy in several cell lines, including mouse embryonic fibroblasts and the human cancer cell lines HeLa, HCT-116 and DLD-1. The autophagy induced by FTS seems to inhibit the cell death induced by FTS, since in the absence of autophagy the death of FTS-treated cells was enhanced. Therefore, inhibition of autophagy may promote the inhibition of tumor cell growth and the cell death mediated by FTS.

Quantitative phosphoproteomic profiling of human non-small cell lung cancer tumors

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related deaths worldwide. Within the molecular scope of NCSLC, a complex landscape of dysregulated cellular signaling has emerged, defined largely by mutations in select mediators of signal transduction, including the epidermal growth factor receptor (EGFR) and anaplastic lymphoma (ALK) kinases. Consequently, these mutant kinases become constitutively activated and targets for chemotherapeutic intervention. Encouragingly, small molecule inhibitors of these pathways have shown promise in clinical trials or are approved for clinical use. However, many protein kinases are dysregulated in NSCLC without genetic mutations. To quantify differences in tumor cell signaling that are transparent to genomic methods, we established a super-SILAC internal standard derived from NSCLC cell lines grown in vitro and labeled with heavy lysine and arginine, and deployed them in a phosphoproteomic workflow. We identified 9019 and 8753 phosphorylation sites in two separate tumors. Relative quantification of phosphopeptide abundance between tumor samples allowed for the determination of specific hubs and pathways differing between each tumor. Sites downstream of Ras showed decreased inhibitory phosphorylation (Raf/Mek) and increased activating phosphorylation (Erk1/2) in one tumor versus another. In this way, we were able to quantitatively access oncogenic kinase signaling in primary human tumors.

BIOLOGICAL SIGNIFICANCE

Through the use of quantitative proteomics, we demonstrated the feasibility and coverage that large scale mass spectrometry can leverage for understanding kinase networks in cancer. By incorporating Super-SILAC based quantitation into a typical pathology workflow, we were able to access and compare tumors from multiple patients in this analysis with high accuracy and dynamic range. We analyzed tumors from patients diagnosed with non-small cell lung cancer and were able to detect comprehensive phosphorylation networks relaying through known hubs of oncogenesis in lung cancer. We hereby show that it is possible to track changes to phosphorylation networks across multiple tumors, opening up the possibility that drug susceptibility and patient-specific stratification can be implemented downstream of classical pathology.

Targeting the RAS oncogene

INTRODUCTION

The Ras proteins (K-Ras, N-Ras, and H-Ras) are GTPases that function as molecular switches for a variety of critical cellular activities and their function is tightly and temporally regulated in normal cells. Oncogenic mutations in the RAS genes, which create constitutively-active Ras proteins, can result in uncontrolled proliferation or survival in tumor cells.

AREAS COVERED

The paper discusses three therapeutic approaches targeting the Ras pathway in cancer: i) Ras itself, ii) Ras downstream pathways, and iii) synthetic lethality. The most adopted approach is targeting Ras downstream signaling, and specifically the PI3K-AKT-mTOR and Raf-MEK pathways, as they are frequently major oncogenic drivers in cancers with high Ras signaling. Although direct targeting of Ras has not been successful clinically, newer approaches being investigated in preclinical studies, such as RNA interference-based and synthetic lethal approaches, promise great potential for clinical application.

EXPERT OPINION

The challenges of current and emerging therapeutics include the lack of "tumor specificity" and their limitation to those cancers which are "dependent" on aberrant Ras signaling for survival. While the newer approaches have the potential to overcome these limitations, they also highlight the importance of robust preclinical studies and bidirectional translational research for successful clinical development of Ras-related targeted therapies.

Synergistic effects of combined Wnt/KRAS inhibition in colorectal cancer cells

Activation of Wnt signalling due to inability to degrade β-catenin is found in >85% of colorectal cancers. Approximately half of colon cancers express a constitutively active KRAS protein. A significant fraction of patients show both abnormalities. We previously reported that simultaneous down-regulation of both β-catenin and KRAS was necessary to induce significant cell death and tumor growth inhibition of colorectal cancer cells. Although attractive, an RNAi-based therapeutic approach is still far from being employed in the clinical setting. Therefore, we sought to recapitulate our previous findings by the use of small-molecule inhibitors of β-catenin and KRAS. We show here that the β-catenin inhibitors PKF115-584 and pyrvinium pamoate block β-catenin-dependent transcriptional activity and synergize with the KRAS inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS, salirasib) in colon cancer cells driven by Wnt and KRAS oncogenic signals, but not in cells carrying BRAF mutations. The combined use of these compounds was superior to the use of any drug alone in inducing cell growth arrest, cell death, MYC and survivin down-modulation, and inhibition of anchorage-independent growth. Expression analysis of selected cancer-relevant genes revealed down-regulation of CD44 as a common response to the combined treatments. These data provide a proof of principle for a combination therapeutic strategy in colorectal cancer.

Recent understanding of the molecular mechanisms for the efficacy and resistance of EGF receptor-specific tyrosine kinase inhibitors in non-small cell lung cancer

INTRODUCTION

The epidermal growth factor receptor (EGFR) and its family members are involved in many aspects of tumor biological processes. Aberrant activation of the EGFR tyrosine kinase by mutations or protein overexpression is observed in various types of human cancer, including lung cancer. EGFR tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib and erlotinib, are highly effective in lung cancer patients who harbor active mutations in the EGFR gene. However, patients who are initially sensitive to EGFR-TKIs eventually relapse within few years.

AREAS COVERED

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer and is associated with a high frequency of EGFR mutations. This review describes the EGFR mutations that determine the sensitivity to EGFR-TKIs and the current understanding of the molecular mechanisms of acquired resistance to EGFR-TKIs in NSCLC. Furthermore, the authors describe recent strategies developed to overcome acquired resistance using second-generation EGFR-TKIs and combination therapies with several molecular-targeting drugs.

EXPERT OPINION

Although recent findings have contributed to our understanding of the mechanism of acquired resistance and helped the development of novel strategies to overcome such resistance, the underlying mechanisms are complex and additional research is necessary to develop effective therapeutic strategies for individual patients with lung cancer.

A phase II trial of Salirasib in patients with lung adenocarcinomas with KRAS mutations

INTRODUCTION

KRAS mutations are present in 30% of lung adenocarcinomas. Salirasib prevents Ras membrane binding thereby blocking the function of all Ras isoforms. This phase II study determined the activity of salirasib in patients with advanced lung adenocarcinomas with KRAS mutations.

METHODS

Two cohorts of patients with stage IIIB/IV lung adenocarcinoma were eligible: patients with tumors with KRAS mutations who were previously treated with chemotherapy and patients receiving initial therapy who had ≥15 pack-year smoking history. Salirasib was given orally from days 1 to 28 of a 35-day cycle. The primary end point was the rate of nonprogression at 10 weeks.

RESULTS

Thirty-three patients were enrolled. Thirty patients had KRAS mutations (23 patients who were previously treated and 7/10 patients who had no prior therapy). Of the previously treated patients, 7 of 23 (30%) had stable disease at 10 weeks, and 4 of 10 (40%) previously untreated patients had stable disease at 10 weeks. No patient had a radiographic partial response (0% observed rate, 95% confidence interval 0-12%). The median overall survival was not reached (>9 months) for previously untreated patients and it was 15 months for patients who received prior chemotherapy. Diarrhea, nausea, and fatigue were the most common toxicities.

CONCLUSIONS

Salirasib at the current dose and schedule has insufficient activity in the treatment of KRAS mutant lung adenocarcinoma to warrant further evaluation. The successful enrollment of 30 patients with tumors with KRAS mutant lung adenocarcinoma over 15 months at a single site demonstrates that drug trials directed at a KRAS-specific genotype in lung cancer are feasible.

Inhibition of contact sensitivity by farnesylthiosalicylic acid-amide, a potential Rap1 inhibitor

We hypothesized that Ras proximate 1 (Rap1) functions as an additional target for farnesylthiosalicylic acid (FTS) or its derivatives, and that the inhibition of Rap1 in lymphocytes by these agents may represent a method for treating inflammatory disorders. Indeed, we found that FTS-amide (FTS-A) was able to inhibit the elicitation phase of delayed cutaneous hypersensitivity in vivo. This effect was associated with the inhibition of Rap1 more than with the inhibition of Harvey rat sarcoma viral oncogene (Ras). Moreover, FTS-A inhibited Rap1 and contact sensitivity far better than FTS. We suggest that FTS-A may serve as a possible therapeutic tool in contact sensitivity in particular and T-cell-mediated inflammation in general.

Serum N-glycome biomarker for monitoring development of DENA-induced hepatocellular carcinoma in rat

BACKGROUND

There is a demand for serum markers for the routine assessment of the progression of liver cancer. We previously found that serum N-linked sugar chains are altered in hepatocellular carcinoma (HCC). Here, we studied glycomic alterations during development of HCC in a rat model.

RESULTS

Rat HCC was induced by the hepatocarcinogen, diethylnitrosamine (DENA). N-glycans were profiled using the DSA-FACE technique developed in our laboratory.In comparison with control rats, DENA rats showed a gradual but significant increase in two glycans (R5a and R5b) in serum total N-glycans during progression of liver cirrhosis and cancer, and a decrease in a biantennary glycan (P5). The log of the ratio of R5a to P1 (NGA2F) and R5b to P1 [log(R5a/P1) and log(R5b/P1)] were significantly (p < 0.0001) elevated in HCC rats, but not in rats with cirrhosis or fibrosis or in control rats. We thus propose a GlycoTest model using the above-mentioned serum glycan markers to monitor the progression of cirrhosis and HCC in the DENA-treated rat model. When DENA-treated rats were subsequently treated with farnesylthiosalicyclic acid, an anticancer drug, progression to HCC was prevented and GlycoTest markers (P5, R5a and R5b) reverted towards non-DENA levels, and the HCC-specific markers, log(R5a/P1) and log(R5b/P1), normalized completely.

CONCLUSIONS

We found an increase in core-alpha-1,6-fucosylated glycoproteins in serum and liver of rats with HCC, which demonstrates that fucosylation is altered during progression of HCC. Our GlycoTest model can be used to monitor progression of HCC and to follow up treatment of liver tumors in the DENA rat. This GlycoTest model is particularly important because a rapid non-invasive diagnostic procedure for tumour progression in this rat model would greatly facilitate the search for anticancer drugs.

Galectin-3 promotes chronic activation of K-Ras and differentiation block in malignant thyroid carcinomas

Anaplastic thyroid carcinomas are deadly tumors that are highly invasive, particularly into the bones. Although oncogenic Ras can transform thyroid cells into a severely malignant phenotype, thyroid carcinomas do not usually harbor ras gene mutations. Therefore, it is not known whether chronically active Ras contributes to thyroid carcinoma cell proliferation, although galectin-3 (Gal-3), which is strongly expressed in thyroid carcinomas but not in benign tumors or normal glands, is known to act as a K-Ras chaperone that stabilizes and drives K-Ras.GTP nanoclustering and signal robustness. Here, we examined the possibility that thyroid carcinomas expressing high levels of Gal-3 exhibit chronically active K-Ras. Using cell lines representing three types of malignant thyroid tumors--papillary, follicular, and anaplastic--we investigated the possible correlation between Gal-3 expression and active Ras content, and then examined the therapeutic potential of the Ras inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS; Salirasib) for thyroid carcinoma. Thyroid carcinoma cells strongly expressing Gal-3 showed high levels of K-Ras.GTP expression, and K-Ras.GTP transmitted strong signals to extracellular signal-regulated kinase. FTS disrupted interactions between Gal-3 and K.Ras, strongly reduced K-Ras.GTP and phospho-extracellular signal-regulated kinase expression, and enhanced the expression of the cell cycle inhibitor p21 as well as of the thyroid transcription factor 1, which is involved in thyroid cell differentiation. FTS also inhibited anaplastic thyroid carcinoma cell proliferation in vitro and tumor growth in nude mice. We conclude that wild-type K-Ras.GTP in association with Gal-3 contributes to thyroid carcinoma malignancy and that Ras inhibition might be a useful treatment strategy against these deadly tumors.

Gankyrin plays an essential role in Ras-induced tumorigenesis through regulation of the RhoA/ROCK pathway in mammalian cells

Activating mutations in Ras proteins are present in about 30% of human cancers. Despite tremendous progress in the study of Ras oncogenes, many aspects of the molecular mechanisms underlying Ras-induced tumorigenesis remain unknown. Through proteomics analysis, we previously found that the protein Gankyrin, a known oncoprotein in hepatocellular carcinoma, was upregulated during Ras-mediated transformation, although the functional consequences of this were not clear. Here we present evidence that Gankyrin plays an essential role in Ras-initiated tumorigenesis in mouse and human cells. We found that the increased Gankyrin present following Ras activation increased the interaction between the RhoA GTPase and its GDP dissociation inhibitor RhoGDI, which resulted in inhibition of the RhoA effector kinase Rho-associated coiled coil-containing protein kinase (ROCK). Importantly, Gankyrin-mediated ROCK inhibition led to prolonged Akt activation, a critical step in activated Ras-induced transformation and tumorigenesis. In addition, we found that Gankyrin is highly expressed in human lung cancers that have Ras mutations and that increased Gankyrin expression is required for the constitutive activation of Akt and tumorigenesis in these lung cancers. Our findings suggest that Gankyrin is a key regulator of Ras-mediated activation of Akt through inhibition of the downstream RhoA/ROCK pathway and thus plays an essential role in Ras-induced tumorigenesis.

Salirasib (farnesyl thiosalicylic acid) for brain tumor treatment: a convection-enhanced drug delivery study in rats

Our aim was to assess the ability of convection-enhanced drug delivery (CED), a novel approach of direct delivery of drugs into brain tissue and brain tumors, to treat brain tumors using salirasib (farsnesyl thiosalicylic acid). CED was achieved by continuous infusion of drugs via intracranial catheters, thus enabling convective distribution of high drug concentrations over large volumes while avoiding systemic toxicity. Several phase II/III CED-based trials are currently in progress but have yet to overcome two major pitfalls of this methodology (the difficulty in attaining efficient CED and the significant nonspecific neurotoxicity caused by high drug doses in the brain). In this study, we addressed both issues by employing our previously described novel CED imaging and increased efficiency methodologies to exclusively target the activated form of the Ras oncogene in a 9L gliosarcoma rat model. The drug we used was salirasib, a highly specific Ras inhibitor shown to exert its suppressive effects on growth and migration of proliferating tumor cells in in vitro and in vivo models, including human glioblastoma, without affecting normal tissues. The results show a significant decrease in tumor growth rate in salirasib-treated rats relative to vehicle-treated rats as well as a significant correlation between CED efficacy and tumor growth rate with no observed toxicity despite drug concentrations an order of magnitude higher than previously detected in the brain. The results show that CED of salirasib is efficient and nontoxic for the treatment of glioblastoma in a rat model, thus suggesting that it may be considered for clinical application.

Novel Ras pathway inhibitor induces apoptosis and growth inhibition of K-ras-mutated cancer cells in vitro and in vivo

MT477 is a novel quinoline with potential activity in Ras-mutated cancers. In this study, MT477 preferentially inhibited the proliferation of K-ras-mutated human pulmonary (A549) and pancreatic (MiaPaCa-2) adenocarcinoma cell lines, compared with a non-Ras-mutated human lung squamous carcinoma cell line (H226) and normal human lung fibroblasts. MT477 treatment induced apoptosis in A549 cells and was associated with caspase-3 activation. MT477 also induced sub-G1 cell-cycle arrest in A549 cells. Although we found that MT477 partially inhibited protein kinase C (PKC), it inhibited Ras directly followed in time by inhibition of 2 Ras downstream molecules, Erk1/2 and Ral. MT477 also caused a reorganization of the actin cytoskeleton and formation of filopodias in A549 cells; this event may lead to decreased migration and invasion of tumor cells. In a xenograft mouse model, A549 tumor growth was inhibited significantly by MT477 at a dose of 1 mg/kg (P < 0.05 vs vehicle control). Taken together, these results support the conclusion that MT477 acts as a direct Ras inhibitor. This quinoline, therefore, could potentially be active in Ras-mutated cancers and could be developed extensively as an anticancer molecule with this in mind.

Determination of salirasib (S-trans,trans-farnesylthiosalicylic acid) in human plasma using liquid chromatography-tandem mass spectrometry

A liquid chromatography/tandem mass spectrometric (LC/MS/MS) assay was developed for the quantitative determination of salirasib (S-trans,trans-farnesylthiosalicylic acid, FTS) in human plasma. Sample pretreatment involved liquid-liquid extraction with methyl t-butyl ether of 0.5-mL aliquots of lithium heparin plasma spiked with the internal standard, S-trans,trans-5-fluoro-farnesylthiosalicylic acid (5-F-FTS). Separation was achieved on Waters X-Terra C(18) (50 mm x 2.1 mm i.d., 3.5 microm) at room temperature using isocratic elution with acetonitrile/10 mM ammonium acetate buffer mobile phase (80:20, v/v) containing 0.1% formic acid at a flow rate of 0.20 mL/min. Detection was performed using electrospray MS/MS by monitoring the ion transitions from m/z 357.2-->153.0 (salirasib) and m/z 375.1-->138.8 (5-F-FTS). Calibration curves were linear in the concentration range of 1-1000 ng/mL. A 5000 ng/mL sample that was diluted 1:10 (v/v) with plasma was accurately quantitated. The values for both within day and between day precision and accuracy were well within the generally accepted criteria for analytical method (<8.0%). This assay was subsequently used for the determination of salirasib concentrations in plasma of cancer patients after oral administration of salirasib at a dose of 400 mg.

The Ras inhibitor farnesylthiosalicylic acid (Salirasib) disrupts the spatiotemporal localization of active Ras: a potential treatment for cancer

Chronic activation of Ras proteins by mutational activation or by growth factor stimulation is a common occurrence in many human cancers and was shown to induce and be required for tumor growth. Even if additional genetic defects are present, "correction" of the Ras defect has been shown to reverse Ras-dependent tumorigenesis. One way to block Ras protein activity is by interfering with their spatiotemporal localization in cellular membranes or in membrane microdomains, a prerequisite for Ras signaling and biological activity. Detailed reports describe the use of this method in studies employing farnesylthiosalicylic acid (FTS, Salirasib), a Ras farnesylcysteine mimetic, which selectively disrupts the association of chronically active Ras proteins with the plasma membrane. FTS competes with Ras for binding to Ras-escort proteins, which possess putative farnesyl-binding domains and interact only with the activated form of Ras proteins, thereby promoting Ras nanoclusterization in the plasma membrane and robust signals. This chapter presents three-dimensional time-lapse images that track the FTS-induced inhibition of membrane-activated Ras in live cells on a real-time scale. It also describes a mechanistic model that explains FTS selectivity toward activated Ras. Selective blocking of activated Ras proteins results in the inhibition of Ras transformation in vitro and in animal models, with no accompanying toxicity. Phase I clinical trials have demonstrated a safe profile for oral FTS, with minimal side effects and promising activity in hematological malignancies. Salirasib is currently undergoing trials in patients with pancreatic cancer and with nonsmall cell lung cancer, with or without identified K-Ras mutations. The findings might indicate whether with the disruption of the spatiotemporal localization of oncogenic Ras proteins and the targeting of prenyl-binding domains by anticancer drugs is worth developing as a means of cancer treatment.

Inhibition of the Ras oncoprotein reduces proliferation of hepatocytes in vitro and in vivo in rats

Ras oncoproteins are probably implicated in normal and malignant cell growth in various organs. Inhibition of Ras interferes with cell proliferation of non-hepatic cells in vitro and in vivo. A potential role for Ras in normal and malignant hepatocyte proliferation prompted us to evaluate the impact of Ras inhibition by FTS (S-farnesylthiosalicylic acid) on hepatocyte proliferation in vitro in the human hepatic tumour cell line HepG2 and in vivo after PH (partial hepatectomy) in rats. Rats were administered with FTS intraperitoneally (1, 8 and 16 h after PH) and killed 12, 24 and 48 h after PH. Cell proliferation, phosphorlyation of members of the MAPK (mitogen-activated protein kinase) pathway and levels and activity of cell cycle effectors (cyclin D, cyclin E, Cdk2 and Cdk4) were assessed in FTS-treated rats compared with controls. FTS significantly decreased overall cell count, PCNA (proliferating-cell nuclear antigen) expression and BrdU (bromodeoxyuridine) incorporation into HepG2 cells after 7 days of culture. FTS treatment significantly reduced BrdU incorporation and PCNA expression in hepatocytes after PH. Unlike control rats, cell-membrane expression of Ras was decreased in FTS-treated animals after PH, resulting in decreased Raf membrane recruitment and phosphorylation and in reduced phosphorylation of ERK1/2 (extracellular-signal-regulated kinase 1/2). The antiproliferative effect of FTS was linked to a decrease in expression and activity of the cyclin E/Cdk2 complex, without affecting cyclin D and Cdk4. Ras inhibition by FTS significantly decreased proliferation of HepG2 cells and normal hepatocytes after a strong and highly synchronized proliferation stimulus elicited by PH. The inhibitory effect was at least partially mediated by inhibition of Ras/Raf/MAPK signalling. It appears worthwhile to evaluate the impact of Ras inhibition on the development of hepatocarcinomas in vivo in adequate animal models.