Phase II study of the efficacy and tolerability of two dosing regimens of the farnesyl transferase inhibitor, R115777, in advanced breast cancer

Role of Molecular Targeted Therapeutic Drugs in Treatment of Breast Cancer: A Review Article

Breast cancer is a multifactor, multistage, and heterogeneous disease. Systemic treatment of breast cancer has changed significantly over the last decade. With a better knowledge of the pathogenesis, researchers and scientists have discovered numerous signaling pathways and synonymous therapeutic targets in breast cancer. Because of the molecular nature of breast cancer, which makes it difficult to understand, previous attempts to treat or prevent it have failed. However, recent decades have provided effective therapeutic targets for treatment. In this review, literature or information on various targeted therapy for breast cancer is discussed. English language articles were explored in numerous directory or databases like PubMed, Web of Sciences, Google Scholar, ScienceDirect, and Scopus. The important keywords used for searching databases are "Breast cancer," "Targeted therapy in breast cancer," "Therapeutic drugs in breast cancer," and "Molecular targets in breast cancer."

RhoB as a tumor suppressor: It’s all about localization

The small GTPase RhoB is distinguished from other Rho proteins by its unique subcellular localization in endosomes, multivesicular bodies, and nucleus. Despite high sequence homology with RhoA and RhoC, RhoB is mainly associated with tumor suppressive function, while RhoA and RhoC support oncogenic transformation in most malignancies. RhoB regulates the endocytic trafficking of signaling molecules and cytoskeleton remodeling, thereby controlling growth, apoptosis, stress response, immune function, and cell motility in various contexts. Some of these functions may be ascribed to RhoB's unique subcellular localization to endocytic compartments. Here we describe the pleiotropic roles of RhoB in cancer suppression in the context of its subcellular localization, and we discuss possible therapeutic avenues to pursue and highlight priorities for future research.

Targeting Harvey rat sarcoma viral oncogene homolog in head and neck cancer: how to move forward?

PURPOSE OF REVIEW

Despite recent advances, treatment personalization remains an issue for recurrent metastatic head and neck squamous cell carcinoma (RM HNSCC) patients. After human papilloma virus (HPV) and programmed death ligand 1 (PDL1) expression, Harvey rat sarcoma viral oncogene homolog (HRAS) appears as an emerging target in this field. In this review, we summarize the features of HRAS -mutated HNSCC and its targeting by farnesyl transferase inhibitors.

RECENT FINDINGS

HRAS mutations define a small subgroup of RM HNSCC patients with a poor prognosis and often refractory to the standard treatments. Posttranslational processing of HRAS being dependent on farnesylation, farnesyl transferase inhibitors have been evaluated in HRAS -mutated tumors. Tipifarnib, a first in class farnesyl transferase inhibitor, has shown efficacy in phase 2 trials with HRAS -mutated tumors. Despite reported high response rates in selected population, the efficacy of Tipifarnib is inconsistent and always transient, probably because of limiting hematological toxicities leading to dose reduction and occurrence of secondary resistance mutations.

SUMMARY

Tipifarnib is the first in the class of farnesyl transferase inhibitors to show efficacy in HRAS -mutated RM HNSCC. The understanding of mechanisms of resistance will pave the way for the design of second-generation farnesyl transferases inhibitors.

Development of Cyclic Peptides Targeting the Epidermal Growth Factor Receptor in Mesenchymal Triple-Negative Breast Cancer Subtype

Triple-negative breast cancer (TNBC) is an aggressive malignancy characterized by the lack of expression of estrogen and progesterone receptors and amplification of human epidermal growth factor receptor 2 (HER2). Being the Epidermal Growth Factor Receptor (EGFR) highly expressed in mesenchymal TNBC and correlated with aggressive growth behavior, it represents an ideal target for anticancer drugs. Here, we have applied the phage display for selecting two highly specific peptide ligands for targeting the EGFR overexpressed in MDA-MB-231 cells, a human TNBC cell line. Molecular docking predicted the peptide-binding affinities and sites in the extracellular domain of EGFR. The binding of the FITC-conjugated peptides to human and murine TNBC cells was validated by flow cytometry. Confocal microscopy confirmed the peptide binding specificity to EGFR-positive MDA-MB-231 tumor xenograft tissues and their co-localization with the membrane EGFR. Further, the peptide stimulation did not affect the cell cycle of TNBC cells, which is of interest for their utility for tumor targeting. Our data indicate that these novel peptides are highly specific ligands for the EGFR overexpressed in TNBC cells, and thus they could be used in conjugation with nanoparticles for tumor-targeted delivery of anticancer drugs.

Antitumor effects of low-dose tipifarnib on the mTOR signaling pathway and reactive oxygen species production in HIF-1α-expressing gastric cancer cells

Farnesyltransferase inhibitors (FTIs) suppress tumor aggressiveness in several malignancies by inhibiting Ras signaling. However, treatment of cells with a low dose of the FTI tipifarnib suppresses the expression of hypoxia‐inducible factor‐1α (HIF‐1α) and results in antitumor effects without inhibiting the Ras pathway. Although we previously reported that elevated HIF‐1α expression is associated with an aggressive phenotype in gastric cancer (GC), little is known about the antitumor effects of FTIs on GC. In this study, we examined the relationship between the antitumor effects of low‐dose tipifarnib and HIF‐1α expression in GC cells. Under normoxic conditions, HIF‐1α was expressed only in MKN45 and KATOIII cells. The inhibitory effect of tipifarnib on HIF‐1α was observed in HIF‐1α‐positive cells. Low‐dose tipifarnib had antitumor effects only on HIF‐1α‐positive cells both in vitro and in vivo. Furthermore, low‐dose tipifarnib inactivated ras homolog enriched in brain (Rheb)/mammalian target of rapamycin (mTOR) signaling and decreased intracellular reactive oxygen species (ROS) levels in HIF‐1α‐positive GC cells. Our results that the antitumor effects of low‐dose tipifarnib are at least partially mediated through suppression of mTOR signaling and HIF‐1α expression via inhibition of Rheb farnesylation and reduction in ROS levels. These findings suggest that low‐dose tipifarnib may be capable of exerting an antitumor effect that is dependent on HIF‐1α expression in GC cells. Tipifarnib may have potential as a novel therapeutic agent for HIF‐1α‐expressing GC exhibiting an aggressive phenotype.

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.

Signaling pathways essential for triple-negative breast cancer stem-like cells

Since the discovery of breast cancer stem cells (CSCs), a significant effort has been made to identify and characterize these cells. It is a generally believe that CSCs play an important role in cancer initiation, therapy resistance, and progression of triple-negative breast cancer (TNBC), an aggressive breast cancer subtype with poor prognosis. Thus, therapies targeting these cells would be a valuable addition to standard treatments that primarily target more differentiated, rapidly dividing TNBC cells. Although several cell surface and intracellular proteins have been described as biomarkers for CSCs, none of these are specific to this population of cells. Recent research is moving toward cellular signaling pathways as targets and biomarkers for CSCs. The WNT pathway, the nuclear factor-kappa B (NF-κB) pathway, and the cholesterol biosynthesis pathway have recently been identified to play a key role in proliferation, survival, and differentiation of CSCs, including those of breast cancer. In this review, we assess recent findings related to these three pathways in breast CSC, with particular focus on TNBC CSCs, and discuss how targeting these pathways, in combination with current standard of care, might prove effective and improve the prognosis of TNBC patients.

Increased Cholesterol Biosynthesis Is a Key Characteristic of Breast Cancer Stem Cells Influencing Patient Outcome

Tumor eradication may be greatly improved by targeting cancer stem cells (CSCs), as they exhibit resistance to conventional therapy. To gain insight into the unique biology of CSCs, we developed patient-derived xenograft tumors (PDXs) from ER^- breast cancers from which we isolated mammospheres that are enriched for CSCs. Comparative global proteomic analysis was performed on patient tumor tissues and corresponding PDXs and mammospheres. Mammospheres exhibited increased expression of proteins associated with de novo cholesterol synthesis. The clinical relevance of increased cholesterol biosynthesis was verified in a large breast cancer cohort showing correlation with shorter relapse-free survival. RNAi and chemical inhibition of the cholesterol biosynthesis pathway reduced mammosphere formation, which could be rescued by a downstream metabolite. Our findings identify the cholesterol biosynthesis pathway as central for CSC propagation and a potential therapeutic target, as well as providing a mechanistic explanation for the therapeutic benefit of statins in breast cancer.

Biology, pathology, and therapeutic targeting of RAS

RAS was identified as a human oncogene in the early 1980s and subsequently found to be mutated in nearly 30% of all human cancers. More importantly, RAS plays a central role in driving tumor development and maintenance. Despite decades of effort, there remain no FDA approved drugs that directly inhibit RAS. The prevalence of RAS mutations in cancer and the lack of effective anti-RAS therapies stem from RAS' core role in growth factor signaling, unique structural features, and biochemistry. However, recent advances have brought promising new drugs to clinical trials and shone a ray of hope in the field. Here, we will exposit the details of RAS biology that illustrate its key role in cell signaling and shed light on the difficulties in therapeutically targeting RAS. Furthermore, past and current efforts to develop RAS inhibitors will be discussed in depth.

Prediction of postoperative survival of triple-negative breast cancer based on nomogram model combined with expression of HIF-1α and c-myc

The aims of this study were to explore the expression of hypoxia inducible factor-1α (HIF-1α) and c-myc protein in triple-negative breast cancer (TNBC) and its clinical prognostic significance, and to establish a prediction model for postoperative survival of TNBC based on nomogram.A total of 87 patients with TNBC at the Department of Breast Surgery, Beijing Chaoyang Hospital, Capital Medical University from January 2012 to December 2015 were enrolled in this study. Immunohistochemistry was performed to detect the expression of HIF-1α and c-myc protein in breast cancer tissues. Cox regression analyses were performed to explore the correlation between HIF-1α/c-myc expression and clinical pathological parameters as well as prognosis. Receiver-operating characteristic curve was generated for cox multivariate analysis. A nomogram was generated based on the cox multivariate analysis, and a calibration curve was prepared for the nomogram to evaluate the consistency between the predicted probability of the nomogram and the actual observed probability. The stability of nomogram model was validated with an external cohort including 39 TNBC patients.The positive expression rates of HIF-1α and c-myc protein in breast cancer tissues were 41.4% (36/87) and 55.2% (48/87), respectively. HIF-1α expression was significantly correlated with age, tumor diameter, histological grade, lymph node status, and tumor TNM stage; c-myc expression was significantly associated with tumor diameter, histological grade, lymph node status, and tumor TNM stage. Cox univariate and multivariate analyses showed that HIF-1α and c-myc protein expression, histological grade, lymph node status, and tumor TNM stage were the independent risk factors for postoperative survival in TNBC patients. The AUC of prediction model was 0.843 (0.809-0.887). The nomogram could predict the probability of 3-year disease-free survival according to each patient's condition. The calibration curve displayed good agreement of the predicted probability with the actual observed probability, indicating that the nomogram model had great value of prediction. The external validation indicated the prediction model had good stability.HIF-1α-positive expression, c-myc positive expression, histological grade III, lymph node positive, and TNM stage III tumors suggested that TNBC patients had a poor prognosis. This prediction model can be used to predict postoperative survival of TNBC.

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.

RhoB: Team Oncogene or Team Tumor Suppressor?

Although Rho GTPases RhoA, RhoB, and RhoC share more than 85% amino acid sequence identity, they play very distinct roles in tumor progression. RhoA and RhoC have been suggested in many studies to contribute positively to tumor development, but the role of RhoB in cancer remains elusive. RhoB contains a unique C-terminal region that undergoes specific post-translational modifications affecting its localization and function. In contrast to RhoA and RhoC, RhoB not only localizes at the plasma membrane, but also on endosomes, multivesicular bodies and has even been identified in the nucleus. These unique features are what contribute to the diversity and potentially opposing functions of RhoB in the tumor microenvironment. Here, we discuss the dualistic role that RhoB plays as both an oncogene and tumor suppressor in the context of cancer development and progression.

A phase II study of tipifarnib and gemcitabine in metastatic breast cancer

Background Tipifarnib is an orally active, competitive inhibitor of farnesyltransferase which has shown encouraging signs of activity either alone or when combined with other agents. Clinical studies of tipifarnib in combination with anti-estrogen therapy have yielded disappointing results. In contrast, tipifarnib appears to be synergistic in combination with anthracycline based chemotherapy. Here we report the results of the first prospective phase II trial evaluating the efficacy of the novel combination of tipifarnib and gemcitabine in the treatment of metastatic breast cancer. Patients and Methods 30 postmenopausal women with metastatic breast cancer were treated on a 21-day cycle with tipifarnib 300 mg PO twice daily from days 1 through 14. Gemcitabine was administered intravenously at a dose of 1000 mg/m² on days 1 and 8. Patients were treated until disease progression or unacceptable toxicity. Results There was one complete response and four partial responses yielding an objective response rate of 16.7%. Median progression-free survival and overall survival was 2.5 months (95% confidence interval: 1.6-5.7 months) and 13.1 months (95% confidence interval: 9.1-20.6 months), respectively. 40% of patients experienced grade 4 neutropenia in this study. Conclusion The combination of tipifarnib and gemcitabine is not well tolerated with high rates of myelosuppression and is not more effective than gemcitabine monotherapy in the treatment of metastatic breast cancer.

Molecularly Targeted Therapies for Breast Cancer

Background:

The management of patients with localized and advanced breast cancer continues to evolve. Chemotherapy, endocrine therapy, and trastuzumab are effective therapies but leave considerable room for improvement. As the cellular aberrations inherent to cancer cells in general and breast cancer cells specifically are better understood, therapies to target specific cellular pathways continue to be developed with the goal of expanding available effective therapy through better patient selection.

Methods:

We conducted a computerized search of the medical literature as well as a manual search of selected meeting abstracts.

Results:

Several targeted therapies are in phase III clinical trials testing their promise in the treatment of breast cancer. Many other agents are completing phase I and II testing. An overview of the most promising agents in clinical development is discussed herein.

Conclusions:

Targeted therapy for breast cancer is a reality at this time, and several new agents hold promise for expanding and refining the pool of patients likely to further benefit from this approach in the near future.

Molecular-Targeted Agents in Pancreatic Cancer

Background

Despite the acceptance of gemcitabine as the standard first-line agent for the treatment of advanced pancreatic cancer as well as the improved response rates seen with gemcitabine combinations, novel therapies are needed for this disease, which has one of the lowest survival rates. The growing understanding of the molecular basis of pancreatic cancer and the recent introduction of targeted therapeutic agents have initiated novel studies that have the potential to improve on existing treatments.

Methods

We review the rationale and the clinical studies of therapeutic agents that target some of the molecular abnormalities commonly found in pancreatic cancer.

Results

Matrix metalloproteinase inhibitors (MMPIs), farnesyltransferase inhibitors (FTIs), and tyrosine-kinase inhibitors and monoclonal antibodies against growth factors or their receptors are novel agents that have undergone phase II or III trials. Phase III studies of MMPIs, alone or in combination with gemcitabine, and phase III studies of FTIs have produced disappointing results. Other agents in earlier phases of clinical development remain promising.

Conclusions

Despite the negative studies of MMPIs and FTIs, the results of phase II trials of other drugs are encouraging. Targeted agents may improve the prognosis of pancreatic cancer.

Farnesyltransferase Inhibitors and Their Role in the Treatment of Multiple Myeloma

BACKGROUND

Ras mutations are among the most common oncogene mutations found in multiple myeloma (MM). Patients with mutated Ras are less likely to respond to chemotherapy and have a shortened median survival. Therefore, targeting Ras farnesylation may be a valuable approach to treatment of MM. R115777 (tipifarnib) is a potent farnesyltransferase inhibitor (FTI) presently undergoing phase II/III clinical trials.

METHODS

We reviewed the preclinical and clinical experience of FTIs as antineoplastic agents and describe their potential role in the treatment of MM.

RESULTS

FTIs are a novel group of agents that selectively inhibit farnesyltransferase, an enzyme responsible for the posttranslational modification of several proteins including Ras. Since Ras is among the most commonly mutated oncogenes associated with cancer, this class of drugs has been evaluated in clinical trials in a diversity of tumors. R115777 has been evaluated in a phase II clinical trial in patients with advanced myeloma and found to be well tolerated. It induced disease stabilization in more than 60% of patients with advanced myeloma.

CONCLUSIONS

The drug selectively targets farnesyltransferase, but this effect did not correlate with disease stabilization, suggesting that these drugs may be targeting a survival pathway independent of Ras processing. Further studies will evaluate the use of FTI in maintenance therapy as well as in combination with other agents in advanced myeloma.

Low-Dose Farnesyltransferase Inhibitor Suppresses HIF-1α and Snail Expression in Triple-Negative Breast Cancer MDA-MB-231 Cells In Vitro

The aggressiveness of triple-negative breast cancer (TNBC), which lacks estrogen receptor, progesterone receptor and epidermal growth factor receptor 2 (HER2), represents a major challenge in breast cancer. Migratory and self-renewal capabilities are integral components of invasion, metastasis and recurrence of TNBC. Elevated hypoxia-inducible factor-1α (HIF-1α) expression is associated with aggressiveness of cancer. Nonetheless, how HIF-1α expression is regulated and how HIF-1α induces aggressive phenotype are not completely understood in TNBC. The cytotoxic effects of farnesyltransferase (FTase) inhibitors (FTIs) have been studied in cancer and leukemia cells. In contrast, the effect of FTIs on HIF-1α expression has not yet been studied. Here, we show that clinically relevant low-dose FTI, tipifarnib (300 nM), decreased HIF-1α expression, migration and tumorsphere formation in human MDA-MB-231 TNBC cells under a normoxic condition. In contrast, the low-dose FTIs did not inhibit cell growth and activity of the Ras pathway in MDA-MB 231 cells. Tipifarnib-induced decrease in HIF-1α expression was associated with amelioration of the Warburg effect, hypermetabolic state, increases in Snail expression and ATP release, and suppressed E-cadherin expression, major contributors to invasion, metastasis and recurrence of TBNC. These data suggest that FTIs may be capable of ameliorating the aggressive phenotype of TNBC by suppressing the HIF-1α-Snail pathway. J. Cell. Physiol. 232: 192-201, 2017. © 2016 Wiley Periodicals, Inc.

A novel role of farnesylation in targeting a mitotic checkpoint protein, human Spindly, to kinetochores

The mitotic checkpoint protein Spindly is farnesylated in vivo and this modification is required for its interaction with the RZZ complex and its localization to kinetochores.

Kinetochore (KT) localization of mitotic checkpoint proteins is essential for their function during mitosis. hSpindly KT localization is dependent on the RZZ complex and hSpindly recruits the dynein–dynactin complex to KTs during mitosis, but the mechanism of hSpindly KT recruitment is unknown. Through domain-mapping studies we characterized the KT localization domain of hSpindly and discovered it undergoes farnesylation at the C-terminal cysteine residue. The N-terminal 293 residues of hSpindly are dispensable for its KT localization. Inhibition of farnesylation using a farnesyl transferase inhibitor (FTI) abrogated hSpindly KT localization without affecting RZZ complex, CENP-E, and CENP-F KT localization. We showed that hSpindly is farnesylated in vivo and farnesylation is essential for its interaction with the RZZ complex and hence KT localization. FTI treatment and hSpindly knockdown displayed the same mitotic phenotypes, indicating that hSpindly is a key FTI target in mitosis. Our data show a novel role of lipidation in targeting a checkpoint protein to KTs through protein–protein interaction.

Gene signature-guided dasatinib therapy in metastatic breast cancer

PURPOSE

Dasatinib has limited single-agent activity in unselected patients with metastatic breast cancer. Several gene signatures predictive of dasatinib response in vitro have been reported. The purpose of this three-arm, phase II study was to prospectively assess the utility of three previously published gene signatures to select patients with clinical benefit from dasatinib.

EXPERIMENTAL DESIGN

Patients with metastatic breast cancer underwent biopsy for gene expression profiling in an academic CLIA laboratory; those who were positive for any one of three predictive gene signatures (dasatinib sensitivity signature, SRC pathway activity signature, and dasatinib target index) received dasatinib 100 mg orally daily. The three marker-defined cohorts were analyzed separately, using early stopping rules for futility.

RESULTS

Ninety-seven patients were enrolled, 93 underwent biopsy, and 80% of the biopsies were sufficient for molecular testing. Thirty patients were positive for at least one signature and received treatment. Only 1 patient experienced clinical benefit and had stable disease over 300 days. All three arms were closed early for futility. There was one serious biopsy-related adverse event (hematoma and pain following a liver biopsy). There were no unexpected toxicities from dasatinib.

CONCLUSION

None of the three predictive gene signatures, although supported by preclinical evidence, defined tumors clinically sensitive to dasatinib as a single agent.

A RAS renaissance: emerging targeted therapies for KRAS-mutated non-small cell lung cancer

Of the numerous oncogenes implicated in human cancer, the most common and perhaps the most elusive to target pharmacologically is RAS. Since the discovery of RAS in the 1960s, numerous studies have elucidated the mechanism of activity, regulation, and intracellular trafficking of the RAS gene products, and of its regulatory pathways. These pathways yielded druggable targets, such as farnesyltransferase, during the 1980s to 1990s. Unfortunately, early clinical trials investigating farnesyltransferase inhibitors yielded disappointing results, and subsequent interest by pharmaceutical companies in targeting RAS waned. However, recent advances including the identification of novel regulatory enzymes (e.g., Rce1, Icmt, Pdeδ), siRNA-based synthetic lethality screens, and fragment-based small-molecule screens, have resulted in a "Ras renaissance," signified by new Ras and Ras pathway-targeted therapies that have led to new clinical trials of patients with Ras-driven cancers. This review gives an overview of KRas signaling pathways with an emphasis on novel targets and targeted therapies, using non-small cell lung cancer as a case example.

Phase I-II study of the farnesyl transferase inhibitor tipifarnib plus sequential weekly paclitaxel and doxorubicin-cyclophosphamide in HER2/neu-negative inflammatory carcinoma and non-inflammatory estrogen receptor-positive breast carcinoma

Tipifarnib (T) is a farnesyl transferase inhibitor (FTI) that enhances the antineoplastic effects of cytotoxic therapy in vitro, has activity in metastatic breast cancer, and enhances the pathologic complete response (pCR) rate to neoadjuvant doxorubicin-cyclophosphamide (AC) chemotherapy. We, therefore, performed a phase I-II trial of T plus neoadjuvant sequential weekly paclitaxel and 2-week AC chemotherapy in locally advanced breast cancer. Eligible patients with HER2-negative clinical stage IIB-IIIC breast cancer received 12 weekly doses of paclitaxel (80 mg/m(2)) followed by AC (60/600 mg/m(2) every 2 weeks and filgrastim), plus T (100 or 200 mg PO on days 1-3 of each P dose, and 200 mg PO on days 2-7 of each AC cycle). The trial was powered to detect an improvement in breast pCR rate from 15 to 35 % (α = 0.10, β = 0.10) in two strata, including ER and/or PR-positive, non-inflammatory (stratum A) and inflammatory carcinoma (stratum B). Of the 60 patients accrued, there were no dose-limiting toxicities among the first six patients treated at the first T dose level (100 mg BID; N = 3) or second T dose level (200 mg BID; N = 3) plus paclitaxel. Breast pCR occurred in 6/33 patients (18 %, 95 % confidence intervals (CI) 7-36 %) and 1/22 patients (4 %, 95 % CI 0-8 %) in stratum B. Combination of the FTI T with weekly paclitaxel-AC is unlikely to be associated with a breast pCR rate of 35 % or higher in patients with locally advanced HER2/neu-negative inflammatory or non-inflammatory ER- and/or PR-positive breast carcinoma.

Ras and Ras mutations in cancer

Ras genes are pre-eminent genes that are frequently linked with cancer biology. The functional loss of ras protein caused by various point mutations within the gene, is established as a prognostic factor for the genesis of a constitutively active Ras-MAPK pathway leading to cancer. Ras signaling circuit follows a complex pathway, which connects many signaling molecules and cells. Several strategies have come up for targeting mutant ras proteins for cancer therapy, however, the clinical benefits remain insignificant. Targeting the Ras-MAPK pathway is extremely complicated due its intricate networks involving several upstream and downstream regulators. Blocking oncogenic Ras is still in latent stage and requires alternative approaches to screen the genes involved in Ras transformation. Understanding the mechanism of Ras induced tumorigenesis in diverse cancers and signaling networks will open a path for drug development and other therapeutic approaches.

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.

Lonafarnib for cancer and progeria

INTRODUCTION

Lonafarnib is a non-peptidomimetic inhibitor of farnesyl transferase, an enzyme responsible for the post-translational lipid modification of a wide variety of cellular proteins that are involved in the pathogenic pathways of various diseases including cancer and progeria. Although extensive clinical research indicates limited activity of lonafarnib in solid tumors, there is recent interest in combinations of farnesyl transferase inhibitors with imatinib or bortezomib in hematological malignancies and to investigate the role of lonafarnib in progeria.

AREAS COVERED

This review examines the in vitro and in vivo pharmacology of lonafarnib and the available clinical data for lonafarnib monotherapy and combination therapy in the treatment of solid and hematological malignancies as well as progeria, using studies identified from the PubMed database supplemented by computerized search of relevant abstracts from major cancer and hematology conferences.

EXPERT OPINION

There is no evidence to support the use of lonafarnib in solid tumors. There is ongoing interest to explore lonafarnib for progeria and to investigate other farnesyl transferase inhibitors for chronic and acute leukemias.

A phase II trial of capecitabine in combination with the farnesyltransferase inhibitor tipifarnib in patients with anthracycline-treated and taxane-resistant metastatic breast cancer: an Eastern Cooperative Oncology Group Study (E1103)

Capecitabine produces an objective response rate of up to 25% in anthracycline-treated, taxane-resistant metastatic breast cancer (MBC). The farnesyltransferase inhibitor tipifarnib inhibits Ras signaling and has clinical activity when used alone in MBC. The objective of this study was to determine the efficacy and safety of tipifarnib-capecitabine combination in MBC patients who were previously treated with an anthracycline and progressed on taxane therapy. Eligible patients received oral capecitabine 1,000 mg/m2 twice daily plus oral tipifarnib 300 mg twice daily on days 1-14 every 21 days. The primary endpoint was ORR. The trial was powered to detect an improvement in response rate from 25 to 40%. Among 63 eligible, partial response occurred in six patients (9.5%; 90% CI 4.2-17.9%), median progression-free survival was 2.6 months (95% CI 2.1-4.4), and median overall survival was 11.4 months (95% CI 7.7-14.0). Dose modifications were required for 43 patients (68%) for either tipifarnib and/or capecitabine. Grades 3 and 4 toxicities were seen in 30 patients (44%; 90% CI 44.4-67.0%) and 11 patients (16%; 90% CI 10.8-29.0%), respectively. The most common grade 3 toxicities included neutropenia, nausea, and vomiting; and the most common grade 4 toxicity was neutropenia (8 out of 11 cases). The tipifarnib-capecitabine combination is not more effective than capecitabine alone in MBC patients who were previously treated with an anthracycline and taxane therapy.

Preclinical metabolism of LB42908, a novel farnesyl transferase inhibitor, and its effects on the cytochrome P450 isozyme activities

Metabolism of LB42908, a novel farnesyl transferase inhibitor, was investigated for preclinical development. In vitro hepatic metabolism of LB42908 gave rise to at least 9 metabolites via phase I biotransformation pathways, which were characterized by HPLC-UV, LC-MS, and LC-MS/MS analyses. N-Dealkylation was shown to be a major phase I metabolic pathway. Species-specific in vitro metabolism of LB42908 was studied in liver fractions of rat, dog, monkey, and human. Order of metabolic stability is human≈dog>rat≈monkey in both S9 and microsomal fractions. Tissue-specific metabolism of LB42908 in various tissue homogenates of rats demonstrated that the liver was the major organ responsible for phase I metabolism of LB42908. The results from both qualitative and quantitative metabolism studies such as metabolic profiling and metabolic clearance indicated that dog would be the animal model of choice for preclinical toxicology studies. In addition, LB42908 was a potent CYP3A4 inhibitor in human liver microsomes and induced the activities of several CYP isozymes, implying that it has the potential for drug-drug interactions. Repeated dosing of LB42908 in rats did not significantly affect its own metabolism, indicating that long-term administration of LB42908 would not alter its pharmacokinetic profiles.

Neurotoxicity of biologically targeted agents in pediatric cancer trials

Biologically targeted agents offer the promise of delivering specific anticancer effects while limiting damage to healthy tissue, including the central and peripheral nervous systems. During the past 5-10 years, these agents were examined in preclinical and adult clinical trials, and are used with increasing frequency in children with cancer. This review evaluates current knowledge about neurotoxicity from biologically targeted anticancer agents, particularly those in pediatric clinical trials. For each drug, neurotoxicity data are reviewed in adult (particularly studies of brain tumors) and pediatric studies when available. Overall, these agents are well tolerated, with few serious neurotoxic effects. Data from younger patients are limited, and more neurotoxicity may occur in the pediatric population because these agents target pathways that control not only tumorigenesis but also neural maturation. Further investigation is needed into long-term neurologic effects, particularly in children.

A phase I multicenter study of continuous oral administration of lonafarnib (SCH 66336) and intravenous gemcitabine in patients with advanced cancer

We conducted a phase I study to assess safety, pharmacokinetics, pharmacodynamics, and activity of lonafarnib plus gemcitabine. Subjects received oral lonafarnib twice daily and gemcitabine on days 1, 8, and 15 every 28 days; multiple dose levels were explored. Lonafarnib had no apparent effect on gemcitabine PK. Mean lonafarnib half-life ranged from 4 to 7 hr; median T(max) values ranged from 4 to 8 hr. Two patients had partial response; seven patients had stable disease at least 6 months. Oral lonafarnib at 150 mg a.m./100 mg p.m. plus gemcitabine at 1,000 mg/m(2) is the maximum tolerated dose with acceptable safety and tolerability.

[Management of inflammatory breast cancer after neo-adjuvant chemotherapy]

PURPOSE

To assess the benefit of breast surgery for inflammatory breast cancer.

PATIENTS AND METHODS

This retrospective series was based on 232 patients treated for inflammatory breast cancer. All patients received primary chemotherapy followed by either exclusive radiotherapy (118 patients, 51%) or surgery with or without radiotherapy (114 patients, 49%). The median follow-up was 11 years.

RESULTS

The two groups were comparable apart from fewer tumors smaller than 70 mm (43% vs 33%, P=0.003), a higher rate of clinical stage N2 (15% vs 5%, P=0.04) and fewer histopathological grade 3 tumors (46% vs 61%, P<0.05) in the no-surgery group. The addition of surgery was associated with a significant improvement in locoregional disease control (P=0.04) but with no significant difference in overall survival rates or disease-free intervals. Late toxicities were not significantly different between the two treatment groups except for a higher rate of fibrosis in the no-surgery group (P<0.0001), and more lymphedema in the surgery group (P=0.002).

CONCLUSION

Our data suggest an improvement in locoregional control in patients treated by surgery, in conjunction with chemotherapy and radiotherapy, for inflammatory breast cancer.

Cytotoxicity of farnesyltransferase inhibitors in lymphoid cells mediated by MAPK pathway inhibition and Bim up-regulation

The mechanism of cytotoxicity of farnesyltransferase inhibitors is incompletely understood and seems to vary depending on the cell type. To identify potential determinants of sensitivity or resistance for study in the accompanying clinical trial (Witzig et al, page 4882), we examined the mechanism of cytotoxicity of tipifarnib in human lymphoid cell lines. Based on initial experiments showing that Jurkat variants lacking Fas-associated death domain or procaspase-8 undergo tipifarnib-induced apoptosis, whereas cells lacking caspase-9 or overexpressing Bcl-2 do not, we examined changes in Bcl-2 family members. Tipifarnib caused dose-dependent up-regulation of Bim in lymphoid cell lines (Jurkat, Molt3, H9, DoHH2, and RL) that undergo tipifarnib-induced apoptosis but not in lines (SKW6.4 and Hs445) that resist tipifarnib-induced apoptosis. Further analysis demonstrated that increased Bim levels reflect inhibition of signaling from c-Raf to MEK1/2 and ERK1/2. Additional experiments showed that down-regulation of the Ras guanine nucleotide exchange factor RasGRP1 diminished tipifarnib sensitivity, suggesting that H-Ras or N-Ras is a critical farnesylation target upstream of c-Raf in lymphoid cells. These results not only trace a pathway through c-Raf to Bim that contributes to tipifarnib cytotoxicity in human lymphoid cells but also identify potential determinants of sensitivity to this agent.

Promising molecular targeted therapies in breast cancer

In recent years, there has been a significant improvement in the understanding of molecular events and critical pathways involved in breast cancer. This has led to the identification of novel targets and development of anticancer therapies referred to as targeted therapy. Targeted therapy has high specificity for the molecules involved in key molecular events that are responsible for cancer phenotype such as cell growth, survival, migration, invasion, metastasis, apoptosis, cell-cycle progression, and angiogenesis. Targeted agents that have been approved for breast cancer include trastuzumab and lapatinib, directed against human epidermal growth factor receptor 2 (HER2) and bevacizumab, directed against vascular endothelial growth factor (VEGF). Several other targeted agents currently under evaluation in preclinical and clinical trials include inhibitors of epidermal growth factor receptor (EGFR), dual EGFR and HER2 inhibitors, VEGF/VEGFR inhibitors, and agents that interfere with crucial signaling pathways such as PI3K/AKT/mTOR and RAS/MEK/ERK; agents against other tyrosine kinases such as Src, insulin-like growth factor (IGF)/IGF-receptor (IGFR); agents that promote apoptosis such as Poly ADP ribose polymerase inhibitors; agents that target invasion and metastasis such as matrix metalloproteinases inhibitors and others. In this review, we highlight the most promising targeted agents and their combination with mainstream chemotherapeutic drugs in clinical trials.

Present and future evolution of advanced breast cancer therapy

Although the introduction of novel therapies and drug combinations has improved the prognosis of metastatic breast cancer, the disease remains incurable. Increased knowledge of the biology and the molecular alterations in breast cancer has facilitated the design of targeted therapies. These agents include receptor and nonreceptor tyrosine kinase inhibitors (epidermal growth factor receptor family), intracellular signaling pathways (phosphatidylinositol-3-kinase, AKT, mammalian target of rapamycin) angiogenesis inhibitors and agents that interfere with DNA repair (poly(ADP-ribose) polymerase inhibitors). In the present review, we present the most promising studies of these new targeted therapies and novel combinations of targeted therapies with cytotoxic agents.

Targeting DNA replication before it starts: Cdc7 as a therapeutic target in p53-mutant breast cancers

Treatment options for triple-receptor negative (ER-/PR-/Her2-) and Her2-overexpressing (ER-/PR-/Her2+) breast cancers with acquired or de novo resistance are limited, and metastatic disease remains incurable. Targeting of growth signaling networks is often constrained by pathway redundancy or growth-independent cancer cell cycles. The cell-cycle protein Cdc7 regulates S phase by promoting DNA replication. This essential kinase acts as a convergence point for upstream growth signaling pathways and is therefore an attractive therapeutic target. We show that increased Cdc7 expression during mammary tumorigenesis is linked to Her2-overexpressing and triple-negative subtypes, accelerated cell cycle progression (P < 0.001), arrested tumor differentiation (P < 0.001), genomic instability (P = 0.019), increasing NPI score (P < 0.001), and reduced disease-free survival (HR = 1.98 [95% CI: 1.27-3.10]; P = 0.003), thus implicating its deregulation in the development of aggressive disease. Targeting Cdc7 with RNAi, we demonstrate that p53-mutant Her2-overexpressing and triple-negative breast cancer cell lines undergo an abortive S phase and apoptotic cell death due to loss of a p53-dependent Cdc7-inhibition checkpoint. In contrast, untransformed breast epithelial cells arrest in G1, remain viable, and are able to resume cell proliferation on recovery of Cdc7 kinase activity. Thus, Cdc7 appears to represent a potent and highly specific anticancer target in Her2-overexpressing and triple-negative breast cancers. Emerging Cdc7 kinase inhibitors may therefore significantly broaden the therapeutic armamentarium for treatment of the aggressive p53-mutant breast cancer subtypes identified in this study.

Emerging targeted therapies for breast cancer

Increased understanding of the molecular events involved in cancer development has led to the identification of a large number of novel targets and, in parallel, to the development of multiple approaches to anticancer therapy. Targeted therapy focuses on specific molecules in the malignant cell signal transduction machinery, including crucial molecules involved in cell invasion, metastasis, apoptosis, cell-cycle control, and tumor-related angiogenesis. In breast cancer, two new targeted agents have recently been approved: lapatinib, directed against the human epidermal growth factor receptor 2 (HER2); and bevacizumab, directed against vascular endothelial growth factor (VEGF). Multiple other targeted agents are under evaluation in clinical trials, including inhibitors of the epidermal growth factor receptor (EGFR), dual EGFR and HER2 inhibitors, other VEGF or VEGF-receptor inhibitors, and agents that alter crucial signaling pathways, such as RAS/MEK/ERK; phosphatidylinositol-3-kinase/Akt/ mammalian target of rapamycin; insulin-like growth factor/insulin-like growth factor receptor; poly (ADP-ribose) polymerase 1; and others. In this review, we present the most promising studies of these new targeted therapies and novel combinations of targeted therapies with traditional cytotoxic agents.

Therapeutic modulation of k-ras signaling in colorectal cancer

KRAS has an important role in colorectal carcinogenesis and mutant KRAS leads to a permanently activated k-ras protein. To exert its biological activity, k-ras requires post-translational modification by prenylation. K-ras modulation has become a promising concept for new therapies, mostly by interference with the mevalonate pathway and subsequently by the prenylation of k-ras. Clinical data of agents interfering with the mevalonate pathway and the prenylation of ras are summarized and suggest that these agents might be effective when administered in combination with anticancer drugs that target k-ras. Here, we discuss the novel concept that modulation of k-ras might potentiate EGFR therapy by altering the KRAS phenotype.

Management of inflammatory breast cancer after neoadjuvant chemotherapy

PURPOSE

To assess the benefit of breast surgery for inflammatory breast cancer (IBC).

METHODS AND MATERIALS

This retrospective series was based on 232 patients treated for IBC. All patients received primary chemotherapy followed by either exclusive radiotherapy (118 patients; 51%) or surgery with or without radiotherapy (114 patients; 49%). The median follow-up was 11 years.

RESULTS

The two groups were comparable apart from fewer tumors <70 mm (43% vs. 33%, p = 0.003), a higher rate of clinical stage N2 (15% vs. 5%, p = 0.04), and fewer histopathologic Grade 3 tumors (46% vs. 61%, p <0.05) in the no-surgery group. The addition of surgery was associated with a significant improvement in locoregional disease control (p = 0.04) at 10 years locoregional free interval 78% vs. 59% but with no significant difference in overall survival rates or disease-free intervals. Late toxicities were not significantly different between the two treatment groups except for a higher rate of fibrosis in the no-surgery group (p <0.0001) and more lymphedema in the surgery group (p = 0.002).

CONCLUSION

Our data suggest an improvement in locoregional control in patients treated by surgery, in conjunction with chemotherapy and radiotherapy, for IBC. Efforts must be made to improve overall survival.

Biology and management of inflammatory breast cancer

Inflammatory breast cancer is an aggressive subtype of a locally advanced breast cancer that is thought to account for approximately 1-5% of all newly diagnosed breast cancers diagnosed in the USA. Historically, IBC was considered to be a uniformly fatal disease with less than 5% of patients surviving past 5 years. With the advent of a multidisciplinary approach to management, survival outcomes have improved with 5-year survival rates of over 40% being reported. Research efforts are now focused on trying to better understand the epidemiological and molecular characteristics of this disease to further improve survival. Two genes, Rhoc GTPase and WISP3, have been identified that have been found to be concordantly altered in the majority of inflammatory breast cancer tumors and may serve as potential targets for future therapeutic agents. The purpose of this review is to summarize the latest epidemiological and molecular characteristics of IBC, describe the difficulties encountered in trying to clinically diagnose this entity, highlight the importance of a multidisciplinary approach and present some of the latest data on the management of this disease.

Targeting signal transduction pathways in metastatic breast cancer: a comprehensive review

Greater understanding of the underlying etiology and biology of breast cancer is enabling the clinical development of targeted therapies for metastatic breast cancer (MBC). Following the successful introduction of trastuzumab, the first human epidermal growth factor receptor (HER) biologically targeted therapy to become widely used in MBC patients, other agents have been developed. Novel agents include monoclonal antibodies such as pertuzumab, which bind to receptors on the cell surface, and tyrosine kinase inhibitors (TKIs) such as lapatinib, which target intracellular pathways such as that of the epidermal growth factor receptor. There is also growing clinical experience with antiangiogenic agents, particularly in combination with chemotherapy. These include the monoclonal antibody bevacizumab, which targets vascular endothelial growth factor receptor, and multitargeted TKIs with antiangiogenic and antiproliferative activities, such as sunitinib. Combination treatment with multiple agents targeting both the HER family and angiogenic pathways (e.g., trastuzumab plus bevacizumab) is also showing activity in the clinical setting. Despite recent advances, there are unanswered questions regarding the management of MBC with targeted agents. Future studies are necessary to determine the optimal combinations, doses, and schedules required to maximize clinical activity while minimizing toxicity. Despite the temptation to use a targeted agent in all patients, identification of patient subgroups most likely to benefit must be a key goal and will be critical to the successful future use of these treatments. The aim of this review is to summarize some of the key signaling pathways involved in tumor progression and some of the novel therapies that are in development for MBC.

Farnesyl Transferase Inhibitors for Patients with Lung Cancer

The ras family of genes have been identified as potential targets for therapeutic intervention because of somatic mutations in different human cancers. They are mutated in non-small cell lung cancer (NSCLC) approximately 20% of the time. The enzyme farnesyl transferase is involved in posttranslational modification of the ras proteins by covalently linking a farnesyl group to the ras protein. This permits the ras protein to be translocated to the surface membrane, allowing the protein to be involved in signaling for increased proliferation and inhibition of apoptosis. The class of farnesyl transferase inhibitors is designed to block farnesylation and prevent the mature ras signaling and thus inhibit cell proliferation and facilitate apoptosis. Multiple agents that inhibit farnesylation have been developed, and two farnesyl transferase inhibitors have been tested in patients with lung cancer in three Phase II trials. R115777 has been studied in patients with NSCLC and in patients with relapsed small cell lung cancer (SCLC) after chemotherapy. There has been a single trial of L-778,123 in patients with untreated NSCLC. No objective tumor responses in patients with stage IIIB/IV NSCLC were seen in these studies. There were also no objective responses among the 22 patients with relapsed SCLC treated with R115777. The median survival for the 44 patients with NSCLC treated with R115777 was approximately 8 months, whereas it was 11 months for the 23 patients treated with L-778,123. R115777 and L-778,123 were well tolerated in these studies but showed no significant activity as single-agent therapy in relapsed SCLC or untreated NSLC.

Recent advances in systemic therapy. When HER2 is not the target: advances in the treatment of HER2-negative metastatic breast cancer

The anti-human epidermal growth factor receptor 2 (HER2) agent trastuzumab has improved outcomes in breast cancer patients with HER2 over-expressing tumours. However, systemic treatment for patients with HER2-negative disease is still limited to endocrine and cytotoxic therapies. The increasing use of the anthracyclines and taxanes in early stage disease has reduced the available therapeutic options for patients with relapsed disease, and choices are further limited for patients with triple-negative tumours, who typically have a poor prognosis. The novel agents bevacizumab and ixabepilone were recently approved for metastatic breast cancer, and numerous other agents are currently in clinical development that may contribute further valuable therapeutic options.