New targets for therapy in breast cancer: farnesyltransferase inhibitors

Persianolide-A, an eudesmanolide-type sesquiterpene lactone from Artemisia kopetdaghensis, induces apoptosis by regulating ERK signaling pathways

Background and purpose

Herbal components, particularly sesquiterpenes, are progressively recognized as a crucial resource for developing effective therapeutic agents for breast cancer. In this study, the effect of a sesquiterpene lactone known as 8-O-dihydroxy-11a,13-dihydroeudesma-4(15)-en-12,6a-olide (persianolide- A) was examined in breast cancer cell lines.

Experimental approach

MDA-MB-231 and MCF-7 cancer cells were grown in DMEM solution with 10% FBS. Then, an MTT assay was performed to evaluate cell viability. Apoptosis was detected by annexin-PI staining. A caspase 3/7 activity assay kit was used to assess the activity of caspase-3 and caspase-7. Protein expression of Bcl-2, Bax, and p-ERK1/2 was determined by western blotting.

Findings/Results

This study showed that the IC50 values of the persianolide-A for MCF-7 and MDA-MB- 468 cells are 34.76 and 54.48 μM, respectively. In addition, persianolide-A showed a significant increase in apoptosis in both MDAMB-231 and MCF-7 breast cancer cell lines. Persianolide-A significantly increased the expression of the pro-apoptotic protein Bax and decreased the expression of the anti-apoptotic protein Bcl-2. Also, presinolide-A treatment led to a substantial increase in caspase activity with a ratio of 3/7 in both MCF- 7 and MDA-MB-231 cancer cells. In addition, the study showed that persianolide-A decreased the expression of p-ERK1/2 protein.

Conclusion and implications

The results of this study suggest that persianolide-A, sourced from Artemisia kopetdaghensis, induces cell apoptosis in breast cancer cell types. The molecular mechanisms could be implicated in the modulation of the ERK1/2 signaling pathway.

Potential anti-cancer effects of hibernating common carp (Cyprinus carpio) plasma on B16-F10 murine melanoma: In vitro and in vivo studies

Melanoma is the major type of skin cancer, which its treatment is still a challenge in the world. In recent years, interest in hibernation-based therapeutic approaches for various biomedical applications has been increased. Many studies indicated that some factors in the blood plasma of hibernating animals such as alpha-2-macroglobulin (A2M) cause anti-proliferative effects. Considering that, the present study was conducted to investigate the anti-cancer effects of hibernating common carp plasma (HCCP) on murine melanoma (B16-F10) in vitro and in vivo. The effect of HCCP on cell viability, migration, apoptosis rate, and cell cycle distribution of B16-F10 cells, tumor growth, and rate of survival were evaluated. To investigate the role of A2M in the anti-cancer effects of HCCP, the gene of interest and proteins in HCCP and non-hibernating common carp plasma (NHCCP) were evaluated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry analysis. Based on our findings, HCCP significantly decreased B16-F10 cell viability. Moreover, HCCP caused morphological alternations, inhibition of migration, induction of apoptosis, and significantly induced the cell cycle arrest at the G2/M phase. In addition, A2M level was significantly increased in HCCP compared with NHCCP. Taken together, our findings suggested that HCCP had the potential to be a promising novel therapeutic target for cancer treatment because of its anti-cancer properties.

Enzyme Inhibitors from Gorgonians and Soft Corals

For decades, gorgonians and soft corals have been considered promising sources of bioactive compounds, attracting the interest of scientists from different fields. As the most abundant bioactive compounds within these organisms, terpenoids, steroids, and alkaloids have received the highest coverage in the scientific literature. However, enzyme inhibitors, a functional class of bioactive compounds with high potential for industry and biomedicine, have received much less notoriety. Thus, we revised scientific literature (1974-2022) on the field of marine natural products searching for enzyme inhibitors isolated from these taxonomic groups. In this review, we present representative enzyme inhibitors from an enzymological perspective, highlighting, when available, data on specific targets, structures, potencies, mechanisms of inhibition, and physiological roles for these molecules. As most of the characterization studies for the new inhibitors remain incomplete, we also included a methodological section presenting a general strategy to face this goal by accomplishing STRENDA (Standards for Reporting Enzymology Data) project guidelines.

Structure-activity relationship study to improve cytotoxicity and selectivity of lonafarnib against breast cancer cells

Lonafarnib is designed as a farnesyltransferase (FTase) inhibitor and displays inhibitory activities against a wide range of tumor cells. However, a major disadvantage is its unselective activity and high cytotoxicity against nonmalignant cells. Therefore, we structurally modified the terminal 4-methylpiperidine-1-carboxamide residue of lonafarnib and evaluated the antiproliferative effects of the resulting derivatives in Michigan Cancer Foundation - 7 (MCF-7) breast cancer cells as well as simian virus 80 (SV-80) fibroblasts. The highest cytotoxicity against both cell lines (IC₅₀ about 2 µM) was shown by the piperidin-4-yl carbamate 15i and the S-(piperidin-4-yl) carbamothioate 15j. Selectivity for tumor cells was realized in the case of the 1-cyclohexyl-1-methylurea derivative 15b. It reduced the growth of MCF-7 cells with an IC₅₀ of 11.4 µM (lonafarnib: IC₅₀  = 10.8 µM) without influence on the growth of SV-80 cells (IC₅₀  > 50 µM; lonafarnib: IC₅₀  = 14.0 µM). Molecular modeling studies were performed to correlate the cytotoxicity with possible FTase interactions. The theoretical investigations, however, documented a comparable attachment of active, less active, and inactive compounds and did not allow an interpretation of the biological results based on these theoretical considerations.

Lycorine inhibits cell proliferation and induced oxidative stress-mediated apoptosis via regulation of the JAK/STAT3 signaling pathway in HT-3 cells

Human cervical cancer is the fourth most common carcinoma in women in the world. The JAK/STAT3 signaling pathways crucially regulate cell growth and apoptosis. It is a significant target signaling pathway for the development of novel antitumor medicine. This study intended to explore whether lycorine could prevent HT-3 proliferation and induce apoptosis by targeting the JAK/STAT3 signaling cascade. The HT-3 cells were treated with various lycorine dosages and we analyzed cell growth, lipid peroxidation, antioxidants, mitochondrial membrane potential (ΔΨm), DNA damage, apoptosis markers by different in vitro methodologies. Our results revealed that lycorine substantially reserved cell growth via decreased antioxidants, augmented reactive oxygen species (ROS) generation which leads to loss of ΔΨm, increased nuclear crumbling and chromatin condensation, thus resulting in representative increased apoptotic cell death. Furthermore, we analyzed that the molecular mechanical action of lycorine considerably repressed JAK1/STAT3 transactional activation and decrease its downstream molecules Bcl-2, and enhances the expressional activity of Bax, cytochrome c, caspase 3 and 9 in HT-3 cells. Finally, the fact that N-acetylcysteine inhibits lycorine-induced ROS-mediated apoptosis was confirmed in HT-3 cells. Thus, the results indicate that lycorine efficiently enhances apoptosis and inhibits HT-3 cell proliferation. These outcomes collectively proposed that lycorine could be a beneficial chemotherapeutic agent for treating and managing human cervical carcinoma.

Ras Signaling in Breast Cancer

Ras proteins mediate extracellular and cytoplasmic signaling networks via receptor tyrosine kinase. The Ras pathway induces activation of signaling molecules involved in cell proliferation and growth, cell survival and apoptosis, metabolism, and motility. Although Ras mutations in breast cancer are not frequently reported, hyperactivation of Ras signaling plays an important role in breast cancer growth and progression. Oncogenic Ras activation occurs via loss of Ras GTPase-activating proteins, overexpression of growth factor receptor, and stimulation by various cytokines. Effective control of oncogenic Ras is one of the therapeutic strategies in breast cancer. The mechanisms of intracellular localization, activation, and signaling pathway of Ras in cancer have been used to develop therapeutic candidates. Recent studies have reported an effective therapy for breast cancer by inhibition of enzymes involved in the posttranslational modification of Ras, such as farnesyltransferase and geranylgeranyltransferase 1, and anti-cancer therapies targeting the epidermal growth factor receptor (EGFR). Emerging targets involved in EGF-mediated Ras activity in breast cancer have shed new insight into Ras activation in breast cancer progression. These alternative mechanisms for Ras signaling pathway may suggest novel therapeutic approaches for targeting Ras in breast cancer. In spite of the difficulties in targeting Ras protein, important discoveries highlight the direct inhibition of Ras activity. Further studies may elucidate the effects of targeting Ras protein and the clinical relevance thereof.

Understanding Breast cancer: from conventional therapies to repurposed drugs

Breast cancer is the most common cancer among women and is considered a developed country disease. Moreover, is a heterogenous disease, existing different types and stages of breast cancer development, therefore, better understanding of cancer biology, helps to improve the development of therapies. The conventional treatments accessible after diagnosis, have the main goal of controlling the disease, by improving survival. In more advance stages the aim is to prolong life and symptom palliation care. Surgery, radiation therapy and chemotherapy are the main options available, which must be adapted to each person individually. However, patients are developing resistance to the conventional therapies. This resistance is due to alterations in important regulatory pathways such as PI3K/AKt/mTOR, this pathway contributes to trastuzumab resistance, a reference drug to treat breast cancer. Therefore, is proposed the repurposing of drugs, instead of developing drugs de novo, for example, to seek new medical treatments within the drugs available, to be used in breast cancer treatment. Providing safe and tolerable treatments to patients, and new insights to efficacy and efficiency of breast cancer treatments. The economic and social burden of cancer is enormous so it must be taken measures to relieve this burden and to ensure continued access to therapies to all patients. In this review we focus on how conventional therapies against breast cancer are leading to resistance, by reviewing those mechanisms and discussing the efficacy of repurposed drugs to fight breast cancer.

Cholesterol and beyond - The role of the mevalonate pathway in cancer biology

Cancer is a multifaceted global disease. Transformation of a normal to a malignant cell takes several steps, including somatic mutations, epigenetic alterations, metabolic reprogramming and loss of cell growth control. Recently, the mevalonate pathway has emerged as a crucial regulator of tumor biology and a potential therapeutic target. This pathway controls cholesterol production and posttranslational modifications of Rho-GTPases, both of which are linked to several key steps of tumor progression. Inhibitors of the mevalonate pathway induce pleiotropic antitumor-effects in several human malignancies, identifying the pathway as an attractive candidate for novel therapies. In this review, we will provide an overview about the role and regulation of the mevalonate pathway in certain aspects of cancer initiation and progression and its potential for therapeutic intervention in oncology.

Therapeutic potential of RAS prenylation pharmacological inhibitors in the treatment of breast cancer, recent progress, and prospective

Breast cancer is one of the most prevalent malignancies among women around the world. RAS proteins require posttranslational modifications, including protein prenylation for proper membrane localization and signaling. Regulation of RAS signaling via specific and novel pharmacological inhibitors is a potentially novel therapeutic approach in breast cancer therapy. This review summarizes the recent knowledge about the clinical value of RAS prenylation pharmacological inhibitors in breast cancer treatment.

Cytotoxic effect of Drimia maritima bulb extract and induction of mitochondrial apoptotic signaling in human breast cancer cells, MCF-7 and MDA-MB-468

Background

Drimia maritima (D. maritima) is a plant belonging to the family Asparagaceae, which has been used for the treatment of several ailments including cancer around the world. To our knowledge, there is no comprehensive study about the molecular mechanisms of anticancer activity of this plant, yet.

Materials and methods

In the current study, cell viability, apoptosis induction, ROS production, mitochondrial apoptotic pathway, and ER stress mediators have been evaluated in breast cancer cells, MCF7, and MDA-MB-468 treated with D. maritima.

Results

Significant cytotoxic effects were observed in MCF-7 and MDA-MB-468 cells after exposure to D. maritima. Apoptosis induction was determined using Annexin-V-FITC and propidium iodide staining. Furthermore, an increase of ROS, loss of mitochondrial membrane potential, the release of cytochrome c, activation of caspases, and elevation in the Bax/Bcl-2 ratio was determined. D. maritima dose-dependently increased the mRNA expression of ER stress markers such as CHOP, ATF-4, GADD34, and TRIB3 in MCF-7, and MDA-MB-468 cells.

Conclusion

These data suggest that D. maritima induces apoptosis in human breast cancer cells via the mitochondrial-mediated pathway. In addition, endoplasmic reticulum stress seems to be involved in D. maritima-induced cell death.

Lycorine inhibits the growth and metastasis of breast cancer through the blockage of STAT3 signaling pathway

Signal transducer and activator of transcription 3 (STAT3) is involved in the growth and metastasis of breast cancer, and represents a potential target for developing new anti-tumor drugs. The purpose of this study is to investigate whether Lycorine, a pyrrolo[de]phenanthridine ring-type alkaloid extracted from Amaryllidaceae genera, could inhibit breast cancer by targeting STAT3 signaling pathway. The human breast cancer cell lines were incubated with various concentrations of Lycorine, and cell proliferation, colony formation, cell cycle distribution, apoptosis, migration and invasion were assayed by several in vitro approaches. Results showed that Lycorine significantly suppressed cell proliferation, colony formation, migration and invasion, as well as induced cell apoptosis, but showed no apparent impact on cell cycle. In addition, the effect of Lycorine on tumor growth and metastasis in nude mouse models was investigated, and results showed that Lycorine significantly inhibited tumor growth and metastasis in vivo. Mechanistically, Lycorine significantly inhibited STAT3 phosphorylation and transcriptional activity through upregulating SHP-1 expression. Lycorine also downregulated the expressions of STAT3 target genes, including Mcl-1, Bcl-xL, MMP-2, MMP-9, which are involved in apoptosis and invasion of breast cancer. Taken together, these findings suggest that Lycorine may be a promising candidate for the prevention and treatment of human breast cancer.

Induction of G1-phase cell cycle arrest and apoptosis pathway in MDA-MB-231 human breast cancer cells by sulfated polysaccharide extracted from Laurencia papillosa

Background

Marine algae consumption is linked to law cancer incidences in countries that traditionally consume marine products. Hence, Phytochemicals are considered as potential chemo-preventive and chemotherapeutic agents against cancer. We investigated the effects of the algal sulfated polysaccharide extract (ASPE) from the red marine alga L. papillosa on MDA-MB-231 human breast cancer cell line.

Methods

Flow cytometry analysis was performed to study the cell viability, cell cycle arrest and apoptosis. Changes in the expression of certain genes associated with cell cycle regulation was conducted by PCR real time analyses. Further investigations on apoptotic molecules was performed by ROS measurement and protein profiling.

Results

ASPE at low doses (10 µg/ml), inhibited cell proliferation, and arrested proliferating MDA-MB-231 cells at G1-phase. However, higher doses (50 µg/ml), triggered apoptosis in those cells. The low dose of ASPE also caused up-regulation of Cip1/p21 and Kip1/p27 and down-regulation of cyclins D1, D2, and E1 transcripts and their related cyclin dependent kinases: Cdk2, Cdk4, and Cdk6. The higher doses of ASPE initiated a dose-dependent apoptotic death in MDA-MB-231 by induction of Bax transcripts, inhibition of Bcl-2 and cleavage of Caspase-3 protein. Over-generation of reactive oxygen species (ROS) were also observed in MDA-MB-231 treated cells.

Conclusions

These findings indicated that ASPE induces G1-phase arrest and apoptosis in MDA-MB-231 cells. ASPE may serve as a potential therapeutic agent for breast cancer.

Salidroside inhibits the growth of human breast cancer in vitro and in vivo

Salidroside has been identified as one of the most potent compounds isolated from the plant Rhodiola rosea, and was found to have several important biological properties, including antioxidant and anti-inflammatory activity; however, its anticancer effects are poorly understood. Thus, the present study focused on evaluating the effects of purified salidroside on the growth of human breast cancer in vitro and in vivo, and on further investigating its possible molecular mechanisms. The human breast cancer cell line, MCF-7, was incubated with various concentrations of salidroside, and cell proliferation, colony formation, cell cycle distribution, apoptosis, migration and invasion were assayed by several in vitro approaches. As a result, it was found that salidroside treatment significantly inhibited cell proliferation, colony formation, migration and invasion, as well as induced cell apoptosis and cell cycle arrest at the G0/G1 phase in vitro. In addition, we also evaluated the effect of salidroside on tumor growth in a nude mouse model, and found that salidroside treatment significantly suppressed tumor growth in vivo. We also further disclosed that salidroside treatment significantly inhibited the intracellular reactive oxygen species (ROS) formation and MAPK pathway activation, which may contribute to the inhibition of tumor growth of breast cancer and reduction of oxidative stress. In conclusion, these findings suggest that salidroside may be a promising candidate target for the prevention and treatment of human breast cancer.

Anti-proliferative and apoptotic activities of constituents of chloroform extract of Juglans regia leaves

OBJECTIVES

To evaluate anti-proliferative as well as apoptotic activities of compounds identified in chloroform extract of Juglans regia leaves, on human breast and oral cancer cell lines (MCF-7 and BHY).

MATERIALS AND METHODS

Column chromatography, MTT assay, flowcytometry and western blotting have all been used in the study.

RESULTS

Bioassay-guided fractionation of chloroform extract of J. regia afforded isolation of 5-hydroxy-3,7,4'-trimethoxyflavone [1], lupeol [2], daucosterol [3], 4-hydroxy-α-tetralone [4], β-sitosterol [5], 5,7- dihydroxy-3,4'-dimethoxyflavone [6] and regiolone [7]. Structures of the compounds were established on the basis of spectroscopic analyses [Nuclear magnetic resonance (NMR) and mass]. All compounds inhibited proliferation of MCF-7 (human breast adenocarcinoma) and BHY (human oral squamous carcinoma) cells in a concentration-dependent manner. Compounds 6 and 7 had potent cytotoxic effects on both MCF-7 and BHY cells (IC50 21-51 μm), yet were not toxic to normal cells. MCF-7 growth inhibition was attributed to apoptosis; population of apoptotic cells increased from 1.12% in controls to 5.64 and 8.1% after 48-h treatment with compounds 6 and 7, indicating their potential at inducing early and late apoptosis. The caspase cascade was not activated, as indicated by only insignificant cleavage of caspase-3.

CONCLUSIONS

Our results suggest that compounds 6 and 7 can induce apoptosis in MCF-7 cells through the caspase-3 independent pathway.

Phase I study of lonafarnib (SCH66336) in combination with trastuzumab plus paclitaxel in Her2/neu overexpressing breast cancer: EORTC study 16023

PURPOSE

This phase I study was performed to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLT), safety profile, recommended dose for phase II studies, the pharmacokinetics, and antitumor activity of the combination of lonafarnib (farnesyl transferase inhibitor), trastuzumab, and paclitaxel in Her2-positive advanced breast cancer.

METHODS

Twenty-three patients with Her2-overexpressing breast cancer received in the first cycle paclitaxel and trastuzumab and from cycle 2 onwards lonafarnib which was added to the combination. Dose-limiting toxicity (DLT) was determined during the second cycle.

RESULTS

The MTD and the recommended dose for phase II trials are lonafarnib: 250 mg/day [125 mg/bi-daily (BID)] continuously, paclitaxel: 175 mg/m² 3-h infusion every 3 weeks, and trastuzumab: 4 mg/kg loading dose and 2 mg/kg/week thereafter. The most frequently observed adverse events starting from cycle 1 onwards were alopecia, myalgia, sensory neuropathy, fatigue, arthralgia, leukocytopenia, and neutropenia. From cycle 2 onwards, additional adverse events appeared, such as diarrhea, nausea, dyspepsia, vomiting, and allergy. The mean systemic exposures of both lonafarnib and paclitaxel through all dose levels were higher in the regimen with all three study medications but with no statistically significant difference. Preliminary antitumor activity (CR + PR) was observed in 58% of all patients.

CONCLUSION

Lonafarnib can be safely combined and tolerated with full doses of paclitaxel and trastuzumab in Her2-positive advanced breast cancer patients. Promising preliminary antitumor activity warrants further evaluation of lonafarnib in combination with paclitaxel and trastuzumab in Her2-positive breast cancer.

Wortmannin induces MCF-7 breast cancer cell death via the apoptotic pathway, involving chromatin condensation, generation of reactive oxygen species, and membrane blebbing

BACKGROUND

Apoptosis can be used as a reliable marker for evaluating potential chemotherapeutic agents. Because wortmannin is a microbial steroidal metabolite, it specifically inhibits the phosphatidyl inositol 3-kinase pathway, and could be used as a promising apoptosis-based therapeutic agent in the treatment of cancer. The objective of this study was to investigate the biomolecular mechanisms involved in wortmannin-induced cell death of breast cancer-derived MCF-7 cells.

METHODS AND RESULTS

Our experimental results demonstrate that wortmannin has strong apoptotic effects through a combination of different actions, including reduction of cell viability in a dose-dependent manner, inhibition of proliferation, and enhanced generation of intracellular reactive oxygen species.

CONCLUSION

Our findings suggest that wortmannin induces MCF-7 cell death via a programmed pathway showing chromatin condensation, nuclear fragmentation, reactive oxygen species, and membrane blebbing, which are characteristics typical of apoptosis.

The farnesyltransferase inhibitor LB42708 suppresses vascular endothelial growth factor-induced angiogenesis by inhibiting ras-dependent mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt signal pathways

Farnesyltransferase (FTase) inhibitors induce growth arrest and apoptosis in various human cancer cells by inhibiting the post-translational activation of Ras. FTase inhibitors also function to suppress the release of vascular endothelial growth factor (VEGF) from tumor cells by inhibiting Ras activation; however, the effects of FTase inhibitors on VEGF-induced angiogenesis in endothelial cells have not been studied. We have investigated the antiangiogenic effect and molecular mechanism of 4-((1-((1-((4-bromophenyl)methyl)-1H-imidazol-5-yl)methyl)-4-(1-napthalenyl)-1H-pyrrol-3-yl)carbonyl)-(9C1)-morpholine (LB42708), a selective nonpeptidic FTase inhibitor, using in vitro and in vivo assay systems. LB42708 inhibited VEGF-induced Ras activation and subsequently suppressed angiogenesis in vitro and in vivo by blocking the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase/p38 mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt/endothelial nitric-oxide synthase pathways in endothelial cells without altering FAK/Src activation. In addition, this inhibitor suppressed VEGF-induced endothelial cell cycle progression at the G(1) phase by suppressing cyclin D1 expression and retinoblastoma phosphorylation as well as up-regulating the cyclin-dependent kinase inhibitors p21 and p27. Knockdown of Ras by short interfering RNA revealed similar inhibitory effects on VEGF-induced angiogenic signal events compared with LB42708. Moreover, the inhibitory effects of LB42708 were significantly higher than those of 4-(2-(4-(8-chloro-3,10-dibromo-6,11-dihydro-5H-benzo-(5,6)-cyclohepta(1,2-b)-pyridin-11(R)-yl)-1-piperidinyl)-2-oxo-ethyl)-1-piperidinecarboxamide (SCH66336), a well known FTase inhibitor. LB42708 suppressed tumor growth and tumor angiogenesis in both xenograft tumor models of Ras-mutated HCT116 cells and its wild-type Caco-2 cells, indicating its potential application in the treatment of both Ras-mutated and wild type tumors. These data indicate that the antitumor effect of LB42708 can be associated with direct inhibition of VEGF-induced tumor angiogenesis by blocking Ras-dependent MAPK and PI3K/Akt signal pathways in tumor-associated endothelial cells.

Role of caspases and Bax protein in saffron-induced apoptosis in MCF-7 cells

Saffron (Crocus sativus), widely used as a spice in Middle Eastern cuisine and is known for anti-cancer properties. The mechanism of saffron-induced cytotoxicity, in tumor cells has not been adequately explored. Therefore, we investigated the role of caspases and Bax protein in saffron-induced apoptosis in MCF-7 cells, a commonly used cell culture system for in vitro studies on breast cancer. Cells were incubated with different concentrations of saffron extract. Cell viability was quantitated by MTT assay. Apoptotic cells were determined using PI staining of DNA fragmentation by flow cytometry (sub-G1 peak). Role of caspase were studied using the pan-caspase inhibitor. Bax protein expression was analysed by western blotting. Saffron extract (200-2000 microg/ml) decreased cell viability in MCF-7 cells as a concentration- and time-dependent manner with an IC50 of 400+/-18.5 microg/ml after 48 h. Analysis of DNA fragmentation by flow cytometry showed apoptotic cell death in MCF-7 cell treated with saffron extract. Saffron-induced apoptosis could be inhibited by pan-caspase inhibitors, indicating caspase-dependent pathway was induced by saffron in MCF-7 cells. Bax protein expression was also increased in saffron-treated cells. Thus saffron exerts proapoptotic effects in a breast cancer-derived cell line and could be considered as a potential chemotherapeutic agent in breast cancer.

A phase I safety, pharmacological, and biological study of the farnesyl protein transferase inhibitor, lonafarnib (SCH 663366), in combination with cisplatin and gemcitabine in patients with advanced solid tumors

PURPOSE

This phase I study was conducted to evaluate the safety, tolerability, pharmacological properties and biological activity of the combination of the lonafarnib, a farnesylproteintransferase (FTPase) inhibitor, with gemcitabine and cisplatin in patients with advanced solid malignancies.

EXPERIMENTAL DESIGN

This was a single institution study to determine the maximal tolerated dose (MTD) of escalating lonafarnib (75-125 mg po BID) with gemcitabine (750-1,000 mg/m(2) on days 1, 8, 15) and fixed cisplatin (75 mg/m(2) day 1) every 28 days. Due to dose-limiting toxicities (DLTs) of neutropenia and thrombocytopenia in initial patients, these patients were considered "heavily pre-treated" and the protocol was amended to limit prior therapy and re-escalate lonafarnib in "less heavily pre-treated patients" on 28-day and 21-day schedules. Cycle 1 and 2 pharmacokinetics (PK), and farnesylation of the HDJ2 chaperone protein and FPTase activity were analyzed.

RESULTS

Twenty-two patients received 53 courses of therapy. Nausea, vomiting, and fatigue were frequent in all patients. Severe toxicities were observed in 91% of patients: neutropenia (41%), nausea (36%), thrombocytopenia (32%), anemia (23%) and vomiting (23%). Nine patients withdrew from the study due to toxicity. DLTs of neutropenia, febrile neutropenia, thrombocytopenia, and fatigue limited dose-escalation on the 28-day schedule. The MTD was established as lonafarnib 75 mg BID, gemcitabine 750 mg/m(2) days 1, 8, 15, and cisplatin 75 mg/m(2) in heavily pre-treated patients. The MTD in the less heavily pre-treated patients could not be established on the 28-day schedule as DLTs were observed at the lowest dose level, and dose escalation was not completed on the 21-day schedule due to early study termination by the Sponsor. No PK interactions were observed. FTPase inhibition was not observed at the MTD, however HDJ-2 gel shift was observed in one patient at the 100 mg BID lonafarnib dose. Anti-cancer activity was observed: four patients had stable disease lasting >2 cycles, one subject had a complete response, and another had a partial response, both with metastatic breast cancer.

CONCLUSION

Lonafarnib 75 mg BID, gemcitabine 750 mg/m(2) days 1, 8, 15, and cisplatin 75 mg/m(2) day 1 on a 28-day schedule was established as the MTD. Lonafarnib did not demonstrate FTPase inhibition at these doses. Despite the observed efficacy, substantial toxicity and questionable contribution of anti-tumor activity of lonafarnib to gemcitabine and cisplatin limits further exploration of this combination.

The molecular genetics of breast cancer and targeted therapy

Breast cancer is a complex, molecular disease, in which a number of cellular pathways involving cell growth and proliferation, such as the MAPK, RB/E2F, P13K/AKT/mTOR, and TP53 pathways, are altered. These pathways represent molecular mechanisms that are composed and regulated by various genes. The genes that are altered in terms of cell growth and proliferation include the oncogenes HER2, c-MYC, and RAS, the ER genes, and the genes for cell cyclin D1 and E, and the tumor suppressor genes RB, TP53, and PTEN, and the breast cancer susceptibility genes BRCA1 and BRCA2. Although the nature of breast cancer is complex and has frustrated previous attempts at treatment or prevention, the elucidation of its molecular nature over the last several decades is now providing targets for effective therapies to treat the disease and hopefully one day to prevent it.

DNA-damage sensitizers: Potential new therapeutical tools to improve chemotherapy

Agents that induce DNA damage in cells--the so-called genotoxins--have successfully been used for decades to treat patients with tumors. Genotoxins alter the DNA of cells, which is detected by DNA damage sensors and which leads to the activation of p53. Activation of p53 can lead to the death of cancer cells. The efficacy of genotoxins in humans is however limited by their toxicity to normal tissues. Specific sensitization of tumor cells to the action of genotoxins would reduce the efficacious doses of genotoxins to be used in patients, diminishing the detrimental side-effects of the drugs on normal tissues. A series of compounds able to sensitize cancer cells to DNA-damaging drugs have recently been identified that have the potential to increase the efficacy of currently used anti-cancer treatments.

The emerging role of targeted therapy for hematologic malignancies: update on bortezomib and tipifarnib

As therapy for hematologic malignancy evolves, new regimens and novel agents that target specific cellular processes allow a more optimistic prognosis for many patients. Bortezomib and tipifarnib are two new, targeted treatments for hematologic malignancies. Bortezomib, a proteasome inhibitor, has shown impressive efficacy in patients with relapsed multiple myeloma and as initial treatment, including before autologous stem cell transplantation. It has been studied as monotherapy and in combination with standard treatments such as dexamethasone, and with newer agents such as the immunomodulators thalidomide and lenalidomide; response is encouraging, even in patients who have relapsed after previously receiving components of a regimen as single agents. Bortezomib is generally well tolerated, including in combination with novel and conventional agents. Tipifarnib is a specific inhibitor of farnesyltransferase. Clinical trials in patients with high-risk acute leukemias and myelodysplastic syndromes have demonstrated good efficacy with tipifarnib. Continued investigation with these new, targeted treatments will further define their use as treatment options in patients with hematologic cancer.

Pathways to tamoxifen resistance

Therapies that target the synthesis of estrogen or the function of estrogen receptor(s) have been developed to treat breast cancer. While these approaches have proven to be beneficial to a large number of patients, both de novo and acquired resistance to these drugs is a significant problem. Recent advances in our understanding of the molecular mechanisms that contribute to resistance have provided a means to begin to predict patient responses to these drugs and develop rational approaches for combining therapeutic agents to circumvent or desensitize the resistant phenotype. Here, we review common mechanisms of antiestrogen resistance and discuss the implications for prediction of response and design of effective combinatorial treatments.

Capecitabine in Combination with Novel Targeted Agents in the Management of Metastatic Breast Cancer: Underlying Rationale and Results of Clinical Trials

At present there is no established standard of care for metastatic breast cancer and prognosis remains poor, although the use of newer chemotherapeutic regimens has led to modest improvements in survival. Capecitabine, an oral prodrug of 5-fluorouracil, is a promising addition to these approaches, having already shown single-agent activity against metastatic breast cancer. Following a pivotal trial demonstrating that capecitabine confers increased survival when used in combination with docetaxel, it is being investigated intensively in combined regimens using other standard chemotherapeutic agents, as well as with novel molecularly targeted therapies. Among the novel agents, the most intensively studied in combination with capecitabine is trastuzumab. Despite preclinical data suggesting that these two agents might not show additive effects, clinical trials have been very encouraging for both heavily pretreated patients and for patients receiving first-line therapy in the metastatic setting. This work is being further extended in an ongoing trial in the neoadjuvant setting. An initial trial in combination with bevacizumab, enrolling heavily pretreated patients, was less successful, but following the example of the E2100 trial, this combination is being re-examined in less heavily treated patients. In addition, this review discusses ongoing trials with an array of newer molecularly targeted agents. Significant improvement in time to progression has already been demonstrated in the combination of lapatinib and capecitabine compared with capecitabine monotherapy; for the most part, however, these trials are still in early stages.

Targeting downstream effectors of epidermal growth factor receptor/HER2 in breast cancer with either farnesyltransferase inhibitors or mTOR antagonists

In breast cancer, there is an increasing recognition of the pivotal role played by the epidermal growth factor receptor (EGFR) and HER2 together with the various downstream signal transduction pathways, in particular the Ras/Raf/Mek/erk1/2 pathway that regulates cell proliferation together with the phosphatidylinositol-3-OH kinase (PI3K)/Akt/mTOR pathway that is implicated in cell survival. While monoclonal antibodies and small molecule tyrosine kinase inhibitors targeted against EGFR/HER2 are now being used for breast cancer therapy, there is considerable interest in also targeting the critical downstream pathways that cells may remain dependent upon. Activation of these downstream pathways in breast cancer may be associated with resistance to either conventional endocrine or cytotoxic therapies or, indeed, lack of response to EGFR/HER2-targeted approaches. Farnesyltransferase inhibitors (FTIs) were initially developed to target Ras activation, although their mechanism of action may be more nonspecific. Trials in breast cancer have been completed with FTIs alone or in combination with endocrine or cytotoxic therapy. Activation of the PI3K/Akt pathway has also been associated with resistance to either tamoxifen or estrogen deprivation, and preclinical studies have shown that the mTOR antagonists can restore endocrine sensitivity in breast cancer cells. Randomized phase II/III trials of aromatase inhibitors combined with mTOR antagonists are in progress and have been powered to detect whether combined therapy can significantly prolong time to disease progression compared to endocrine therapy alone. Finally, preclinical experiments are now investigating whether downstream agents should be combined with upstream EGFR/HER2 therapies to produce maximal blockade of vertical signal transduction pathways. Subsequent trials will be needed to see whether combinations of novel STIs are well tolerated and how they may further enhance clinical benefit in breast cancer.

Effects of the farnesyl transferase inhibitor R115777 (Zarnestra) on mammary carcinogenesis: prevention, therapy, and role of HaRas mutations

The ability of the farnesyl transferase inhibitor R115777 to act as a cancer therapeutic/preventive agent and to modulate proliferation/apoptosis markers was determined in the methylnitrosourea-induced model of mammary carcinogenesis. Female Sprague-Dawley rats were given methylnitrosourea at 50 days of age. In the prevention study, R115777 (5, 16, or 50 mg/kg body weight/d), beginning 5 days after methylnitrosourea treatment, decreased the formation of mammary cancers by 6%, 42%, and 75%, respectively. Approximately 50% of the mammary cancers that developed had HaRas mutations. Only 1 of 15 tumors that grew out in the presence of R115777 (16 or 50 mg/kg body weight/d) had a HaRas mutation. In the therapeutic study, a surgical biopsy of a mammary cancer was done to determine HaRas status, and growth of the cancer was then followed during treatment of the rat with R115777. Virtually every cancer with a HaRas mutation underwent complete regression within 3 weeks, whereas tumors without a HaRas mutation had variable responses to the inhibitor. Both of these studies implied a high sensitivity of tumors with HaRas mutations to the effects of R115777. In order to understand the preferential susceptibility of tumors with HaRas mutations, rats with a palpable cancer were treated with R115777 for a period of 36 or 96 hours prior to sacrifice, and the proliferation and apoptosis levels in the cancers were determined. The proliferative index was significantly (>85%) decreased in all mammary cancers with HaRas mutations, whereas variable responses were observed in cancers without HaRas mutations. Apoptosis was also measured and a 5-fold increase was observed in HaRas mutant tumors, again with varying responses in the HaRas wild-type cancers. Thus, R115777 was active in the prevention and therapy of these chemically induced mammary cancers, but was strikingly more effective in cancers with HaRas mutations.

Reversible inactivation of the transcriptional function of P53 protein by farnesylation

Background

The use of integrating viral vectors in Gene therapy clinical trials has pointed out the problem of the deleterous effect of the integration of the ectopic gene to the cellular genome and the safety of this strategy. We proposed here a way to induce the death of gene modified cells upon request by acting on a pro-apoptotic protein cellular localization and on the activation of its apoptotic function.

Results

We constructed an adenoviral vector coding a chimeric p53 protein by fusing p53 sequence with the 21 COOH term amino acids sequence of H-Ras. Indeed, the translation products of Ras genes are cytosolic proteins that become secondarily associated with membranes through a series of post-translational modifications initiated by a CAAX motif present at the C terminus of Ras proteins. The chimeric p53HRCaax protein was farnesylated efficiently in transduced human osteosarcoma p53-/- cell line. The farnesylated form of p53 resided mainly in the cytosol, where it is non-functional. Farnesyl transferase inhibitors (FTIs) specifically inhibited farnesyl isoprenoid lipid modification of proteins. Following treatment of the cells with an FTI, p53HRCaax underwent translocation into the nucleus where it retained transcription factor activity. Shifting p53 into the nucleus resulted in the induction of p21^waf1/CIP1 and Bax transcription, cell growth arrest, caspase activation and apoptosis.

Conclusion

Artificial protein farnesylation impaired the transcriptional activity of p53. This could be prevented by Farnesyl transferase inhibition. These data highlight the fact that the artificial prenylation of proteins provides a novel system for controlling the function of a transactivating factor.

Computational studies of the farnesyltransferase ternary complex part I: substrate binding

Farnesyltransferase (FTase) catalyzes the transfer of farnesyl from farnesyl diphosphate (FPP) to cysteine residues at or near the C-terminus of protein acceptors with a CaaX motif (a, aliphatic; X, Met). Farnesylation is a critical modification to many switch proteins involved in the extracellular signal transduction pathway, which facilitates their fixation on the cell membrane where the extracellular signal is processed. The malfunction caused by mutations in these proteins often causes uncontrolled cell reproduction and leads to tumor formation. FTase inhibitors have been extensively studied as potential anticancer agents in recent years, several of which have advanced to different phases of clinical trials. However, the mechanism of this biologically important enzyme has not been firmly established. Understanding how FTase recruits the FPP substrate is the first and foremost step toward further mechanistic investigations and the design of effective FTase inhibitors. Molecular dynamic simulations were carried out on the ternary structure of FTase complexed with the FPP substrate and an acetyl-capped tetrapeptide (acetyl-CVIM), which revealed that the FPP substrate maintains an inactive conformation and the binding of the diphosphate group can be largely attributed to residues R291beta, K164alpha, K294beta, and H248beta. The FPP substrate assumes an extended conformation in the binding site with restricted rotation of the backbone dihedral angles; however, it does not have a well-defined conformation when unbound in solution. This is evident from multinanosecond MD simulations of the FPP substrate in a vacuum and solution. Our conclusion is further supported by theoretical J coupling calculations. Our results on the FPP binding are in good agreement with previous experimental kinetic studies on FTase mutants. The hypothetical conformational activation of the FPP substrate is currently under investigation.

Thematic review series: Lipid Posttranslational Modifications. Farnesyl transferase inhibitors

Some proteins undergo posttranslational modification by the addition of an isoprenyl lipid (farnesyl- or geranylgeranyl-isoprenoid) to a cysteine residue proximal to the C terminus. Protein isoprenylation promotes membrane association and contributes to protein-protein interactions. Farnesylated proteins include small GTPases, tyrosine phosphatases, nuclear lamina, cochaperones, and centromere-associated proteins. Prenylation is required for the transforming activity of Ras. Because of the high frequency of Ras mutations in cancer, farnesyl transferase inhibitors (FTIs) were investigated as a means to antagonize Ras function. Evaluation of FTIs led to the finding that both K- and N-Ras are alternatively modified by geranylgeranyl prenyltransferase-1 in FTI-treated cells. Geranylgeranylated forms of Ras retain the ability to associate with the plasma membrane and activate substrates. Despite this, FTIs are effective at inhibiting the growth of human tumor cells in vitro, suggesting that activity is dependent on blocking the farnesylation of other proteins. FTIs also inhibit the in vivo growth of human tumor xenografts and sensitize these models to chemotherapeutics, most notably taxanes. Several FTIs have entered clinical trials for various cancer indications. In some clinical settings, primarily hematologic malignancies, FTIs have displayed evidence of single-agent activity. Clinical studies in progress are exploring the antitumor activity of FTIs as single agents and in combination. This review will summarize the basic biology of FTIs, their antitumor activity in preclinical models, and the current status of clinical studies with these agents.

Farnesyl-transferase inhibitor R115,777 enhances tamoxifen inhibition of MCF-7 cell growth through estrogen receptor dependent and independent pathways

INTRODUCTION

We have previously shown that FTI-277, a farnesyl transferase inhibitor (FTI), enhances the efficacy of tamoxifen (Tam) in inhibiting the proliferation of the estrogen dependent MCF-7 cell line. As the cellular response to Tam is the result of an inhibition of both estrogen receptor-dependent and -independent pathways, we have used the estrogen receptor selective anti-estrogen ICI182,780 and N-pyrrolidine(-phenylmethyl-phenoxy)-ethanamine-HCl (PBPE), a selective ligand of anti-estrogen binding site (AEBS), to dissect out the mechanism(s) associated with the observed additivity resulting from combination treatment with FTI-277 and Tam. Moreover, for these studies, FTI-277 has been replaced by R115,777, a FTI currently in phase III clinical trials.

METHODS

The quantitative sulphorhodamine B (SRB) colorimetric assay was used to determine the growth inhibitory effect of agents on MCF-7 cells. Dose response interactions between R115,777-Tam, R115,777-ICI182,780 and R115,777-PBPE were evaluated, at the IC50 point, using the isobologram method. Apoptotic cell death (DNA fragmentation, nucleus condensation and cytokeratin 18 cleavage) and inhibition of the mevalonate pathway (western blot) were also determined.

RESULTS

Combinations of the specific FTI R115,777 with either ICI182,780 or PBPE exhibit a synergistic effect on MCF-7 cell growth inhibition, while its combination with Tam is additive, as previously reported for FTI-277. Apoptosis is detected after treatment with combinations of R115,777 with either Tam or PBPE but not with ICI182,780, suggesting that each combination inhibits cell proliferation by different mechanisms. Even though the ER pathway has not yet been deciphered, it is shown here that the AEBS pathway is able to interfere with the mevalonate pathway at the level of protein farnesylation.

CONCLUSION

Overall, this work reveals that combinations of R115,777 with either selective ER ligands or a selective AEBS ligand are able to induce large increases in their anti-proliferative activities on MCF-7 cells. Moreover, these results suggest that it may be of definite interest to evaluate combinations of R115,777 with different anti-estrogens in the treatment of ER positive breast tumours. Based on these experimental data, such combinations may prove beneficial in different clinical scenarios or when used in specific sequences; studying the combination of R115,777 with ICI182,780 for early treatment and reserving combinations with either Tam or a selective AEBS ligand, such as BMS-217380-01, for more resistant disease.

Therapy of breast cancer with molecular targeting agents

Invasive breast cancer is a heterogeneous disease sustained by intercorrelated and complex growth pathways. Classically, human breast carcinoma has been classified for therapeutic purposes in two distinct categories: one hormone-correlated, the other hormone-uncorrelated. However, the recent advancements of the technology applied to molecular biology by genomic and proteomic analyses have suggested that many more factors are involved in breast cancer growth and progression and that some clusters of these distinguish subgroups of patients at different prognosis. The knowledge of the diversities between tumor and normal tissue of origin is the key to identify novel targets for new selective therapeutic strategies. In fact, the principal goal of molecular-targeted therapy is the suppression of the transformed phenotype minimally affecting normal cells. This review focuses on the molecular targeting compounds directed against the known molecular pathways involved in breast cancer such as: type I growth factors (HER-2/neu; epidermal growth factor receptor [EGFR]), angiogenesis, cyclooxigenase-2 (COX-2) and farnesylation. Presently, trastuzumab is the first agent approved for therapy of HER-2/neu overexpressing tumors. Several other compounds directed against different targets have entered clinical evaluation and the preliminary results are here presented and commented. The major challenges on the clinical development of targeted therapy include the proper selection of patients, the identification of the optimal dosage and schedule of administration, the combinations with conventional treatments and the more appropriate therapeutic strategy.