Gemcitabine plus enzastaurin or single-agent gemcitabine in locally advanced or metastatic pancreatic cancer: results of a phase II, randomized, noncomparative study. Invest New Drugs. 2011;29:144-153. [PMID: 19714296 DOI: 10.1007/s10637-009-9307-8]

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Emerging kinase inhibitors for the treatment of pancreatic ductal adenocarcinoma

INTRODUCTION

Pancreatic cancer is one of the deadliest solid organ cancers. In the absence of specific warning symptoms pancreatic cancer is diagnosed notoriously late. Current systemic chemotherapy regimens extend survival by a mere few months. With the advances in genetic, proteomic, and immunological profiling there is strong rationale to test kinase inhibitors to improve outcome.

AREAS COVERED

This review article provides a comprehensive summary of approved treatments and past, present, and future developments of kinase inhibitors in pancreatic cancer. Emerging roles of protein kinase inhibitors are discussed in the context of the unique stroma, the lack of high-prevalence therapeutic targets and rapid emergence of acquired resistance, novel immuno-oncology kinase targets, and recent medicinal chemistry advances.

EXPERT OPINION

Due to the to-date frequent failure of protein kinase inhibitors indiscriminately administered to unselected pancreatic cancer patients, there is a shift toward the development of these agents in molecularly defined subgroups which are more likely to respond. The development of accurate biomarkers to select patients who are the best candidates based on a detailed understanding of mechanism of action, pro-survival roles, and mediation of resistance of targeted kinases will be critical for the future development of protein kinase inhibitors in this disease.

Activators and Inhibitors of Protein Kinase C (PKC): Their Applications in Clinical Trials

Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinase, is classed into three subfamilies based on their structural and activation characteristics: conventional or classic PKC isozymes (cPKCs; α, βI, βII, and γ), novel or non-classic PKC isozymes (nPKCs; δ, ε, η, and θ), and atypical PKC isozymes (aPKCs; ζ, ι, and λ). PKC inhibitors and activators are used to understand PKC-mediated intracellular signaling pathways and for the diagnosis and treatment of various PKC-associated diseases, such as cancers, neurological diseases, cardiovascular diseases, and infections. Many clinical trials of PKC inhibitors in cancers showed no significant clinical benefits, meaning that there is a limitation to design a cancer therapeutic strategy targeting PKC alone. This review will focus on the activators and inhibitors of PKC and their applications in clinical trials.

Advances in Targeted Therapy and Immunotherapy for Pancreatic Cancer

Pancreatic cancer is a highly aggressive malignancy with an overall 5-year survival rate of <6% due to therapeutic resistance and late-stage diagnosis. These statistics have not changed despite 50 years of research and therapeutic development. Pancreatic cancer is predicted to become the second leading cause of cancer mortality by the year 2030. Currently, the treatment options for pancreatic cancer are limited. This disease is usually diagnosed at a late stage, which prevents curative surgical resection. Chemotherapy is the most frequently used approach for pancreatic cancer treatment and has limited effects. In many other cancer types, targeted therapy and immunotherapy have made great progress and have been shown to be very promising prospects; these treatments also provide hope for pancreatic cancer. The need for research on targeted therapy and immunotherapy is pressing due to the poor prognosis of pancreatic cancer, and in recent years, there have been some breakthroughs for targeted therapy and immunotherapy in pancreatic cancer. This review summarizes the current preclinical and clinical studies of targeted therapy and immunotherapy for pancreatic cancer and ends by describing the challenges and outlook.

Two decades of research toward the treatment of locally advanced and metastatic pancreatic cancer: Remarkable effort and limited gain

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy that is diagnosed at the locally advanced or metastatic stage in approximately 80% of cases. Relative to other tumor types, progress in the treatment of this disease has been painfully slow. While agents targeting DNA repair have proven successful in a subset of patients, the majority of PDACs do not exhibit validated molecular targets. Hence, conventional chemotherapy remains at the forefront of therapy for this disease. In this review, we study two decades of efforts to improve upon the gemcitabine backbone - 67 phase II and III trials enrolling 16,446 patients - that culminated in the approvals of gemcitabine/nab-paclitaxel (Gem/NabP) and FOLFIRINOX. Today, these remain gold standards for the first-line treatment of locally advanced unresectable and metastatic PDAC, while ongoing efforts focus on improving upon the Gem/NabP backbone. Because real world data often do not reflect the data of randomized controlled trials (RCTs), we also summarize the retrospective evidence comparing the efficacy of Gem/NabP and FOLFIRINOX in the first-line setting - 29 studies reporting a median overall survival of 10.7 and 9.1 months for FOLFIRINOX and Gem/NabP, respectively. These values are surprisingly comparable to those reported by the pivotal RCTs at 11.1 and 8.5 months. Finally, there is a paucity of RCT data regarding the efficacy of second-line therapy. Hence, we conclude this review by summarizing the data that ultimately demonstrate a small but significant survival benefit of second-line therapy with Gem/NabP or FOLFIRINOX. Collectively, these studies describe the long journey, the steady effort, and the myriad lessons to be learned from 20 years of PDAC trials to inform strategies for success in clinical trials moving forward.

Cardiotoxicity Associated with Gemcitabine: Literature Review and a Pharmacovigilance Study

BACKGROUND

Gemcitabine is a nucleoside analog, widely used either alone or in combination, for the treatment of multiple cancers. However, gemcitabine may also be associated with cardiovascular adverse-drug-reactions (CV-ADR).

METHODS

First, we searched for all cases of cardiotoxicity associated with gemcitabine, published in MEDLINE on 30 May 2019. Then, we used VigiBase, the World Health Organization's global database of individual case safety reports, to compare CV-ADR reporting associated with gemcitabine against the full database between inception and 1 April 2019. We used the information component (IC), an indicator value for disproportionate Bayesian reporting. A positive lower end of the 95% credibility interval for the IC (IC₀₂₅) ≥ 0, is deemed significant.

RESULTS

In VigiBase, 46,898 reports were associated with gemcitabine on a total of 18,908,940 in the full database. Gemcitabine was associated with higher reporting for myocardial ischemia (MI, n: 119), pericardial diseases (n: 164), supraventricular arrhythmias (SVA, n: 308) and heart failure (HF, n: 484) versus full database with IC₀₂₅ ranging between 0.40 and 2.81. CV-ADR were associated with cardiovascular death in up to 17% of cases.

CONCLUSION

Treatment with gemcitabine is associated with potentially lethal CV-ADRs, including MI, pericardial diseases, SVA and HF. These events should be considered in patient care and clinical trial design.

Evaluation of Phase II Trial Design in Advanced Pancreatic Cancer

OBJECTIVES

We evaluated how well phase II trials in locally advanced and metastatic pancreatic cancer (LAMPC) meet current recommendations for trial design.

METHODS

We conducted a systematic review of phase II first-line treatment trial for LAMPC. We assessed baseline characteristics, type of comparison, and primary end point to examine adherence to the National Cancer Institute recommendations for trial design.

RESULTS

We identified 148 studies (180 treatment arms, 7505 participants). Forty-seven (32%) studies adhered to none of the 5 evaluated National Cancer Institute recommendations, 62 (42%) followed 1, 31 (21%) followed 2, and 8 (5%) followed 3 recommendations. Studies varied with respect to the proportion of patients with good performance status (range, 0%-80%) and locally advanced disease (range, 14%-100%). Eighty-two (55%) studies concluded that investigational agents should progress to phase III testing; of these, 24 (16%) had documented phase III trials. Three (8%) phase III trials demonstrated clinically meaningful improvements for investigational agents. One of 38 phase II trials that investigated biological investigational agents was enriched for a biomarker.

CONCLUSIONS

Phase II trials do not conform well to current recommendations for trial design in LAMPC.

First-line chemotherapy regimens for locally advanced and metastatic pancreatic adenocarcinoma: a Bayesian analysis

Background

Systemic chemotherapy is the standard treatment for locally advanced and metastatic pancreatic cancer, but there is no consensus on the optimum regimen. We aimed to compare and rank the locally advanced and metastatic pancreatic adenocarcinoma chemotherapy regimens evaluated in randomized controlled trials (RCTs) in the past 15 years.

Materials and methods

PubMed, Embase, Cochrane Collaboration database, and ClinicalTrials.gov were searched for RCTs comparing chemotherapy regimens as first-line treatment for locally advanced and metastatic pancreatic adenocarcinomas. By using Bayesian network meta-analysis, we compared and ranked all included chemotherapy regimens in terms of overall survival, progression-free survival, response rate, and hematological toxicity.

Results

The analysis included 68 RCTs, with 14,908 patients and 63 treatment strategies. For overall survival, NSC-631570 (hazard ratio [HR] vs gemcitabine monotherapy 0.44, 95% credible interval: 0.24–0.76) and gemcitabine+NSC-631570 (HR 0.45, 0.24–0.86) were the two top-ranked chemotherapy regimens. For progression-free survival, PEFG (cisplatin + epirubicin + fluorouracil + gemcitabine) ranked first (HR 0.51, 0.34–0.77). PG (gemcitabine + pemetrexed) (odds ratio [OR] 4.68, 2.24–9.64) and FLEC (fluorouracil + leucovorin + epirubicin + carboplatin) (OR 4.52, 1.14–24.00) were ranked the most hematologically toxic, with gastrazole having the least toxicity (OR 0.03, 0.00–0.46).

Conclusion

The chemotherapy regimens NSC-631570 and gemcitabine+NSC-631570 were ranked the most efficacious for locally advanced and metastatic pancreatic adenocarcinomas in terms of overall survival, which warrants further confirmation in large-scale RCTs.

Chemotherapy and radiotherapy for advanced pancreatic cancer

BACKGROUND

Pancreatic cancer (PC) is a highly lethal disease with few effective treatment options. Over the past few decades, many anti-cancer therapies have been tested in the locally advanced and metastatic setting, with mixed results. This review attempts to synthesise all the randomised data available to help better inform patient and clinician decision-making when dealing with this difficult disease.

OBJECTIVES

To assess the effect of chemotherapy, radiotherapy or both for first-line treatment of advanced pancreatic cancer. Our primary outcome was overall survival, while secondary outcomes include progression-free survival, grade 3/4 adverse events, therapy response and quality of life.

SEARCH METHODS

We searched for published and unpublished studies in CENTRAL (searched 14 June 2017), Embase (1980 to 14 June 2017), MEDLINE (1946 to 14 June 2017) and CANCERLIT (1999 to 2002) databases. We also handsearched all relevant conference abstracts published up until 14 June 2017.

SELECTION CRITERIA

All randomised studies assessing overall survival outcomes in patients with advanced pancreatic ductal adenocarcinoma. Chemotherapy and radiotherapy, alone or in combination, were the eligible treatments.

DATA COLLECTION AND ANALYSIS

Two review authors independently analysed studies, and a third settled any disputes. We extracted data on overall survival (OS), progression-free survival (PFS), response rates, adverse events (AEs) and quality of life (QoL), and we assessed risk of bias for each study.

MAIN RESULTS

We included 42 studies addressing chemotherapy in 9463 patients with advanced pancreatic cancer. We did not identify any eligible studies on radiotherapy.We did not find any benefit for chemotherapy over best supportive care. However, two identified studies did not have sufficient data to be included in the analysis, and many of the chemotherapy regimens studied were outdated.Compared to gemcitabine alone, participants receiving 5FU had worse OS (HR 1.69, 95% CI 1.26 to 2.27, moderate-quality evidence), PFS (HR 1.47, 95% CI 1.12 to 1.92) and QoL. On the other hand, two studies showed FOLFIRINOX was better than gemcitabine for OS (HR 0.51 95% CI 0.43 to 0.60, moderate-quality evidence), PFS (HR 0.46, 95% CI 0.38 to 0.57) and response rates (RR 3.38, 95% CI 2.01 to 5.65), but it increased the rate of side effects. The studies evaluating CO-101, ZD9331 and exatecan did not show benefit or harm when compared with gemcitabine alone.Giving gemcitabine at a fixed dose rate improved OS (HR 0.79, 95% CI 0.66 to 0.94, high-quality evidence) but increased the rate of side effects when compared with bolus dosing.When comparing gemcitabine combinations to gemcitabine alone, gemcitabine plus platinum improved PFS (HR 0.80, 95% CI 0.68 to 0.95) and response rates (RR 1.48, 95% CI 1.11 to 1.98) but not OS (HR 0.94, 95% CI 0.81 to 1.08, low-quality evidence). The rate of side effects increased. Gemcitabine plus fluoropyrimidine improved OS (HR 0.88, 95% CI 0.81 to 0.95), PFS (HR 0.79, 95% CI 0.72 to 0.87) and response rates (RR 1.78, 95% CI 1.29 to 2.47, high-quality evidence), but it also increased side effects. Gemcitabine plus topoisomerase inhibitor did not improve survival outcomes but did increase toxicity. One study demonstrated that gemcitabine plus nab-paclitaxel improved OS (HR 0.72, 95% CI 0.62 to 0.84, high-quality evidence), PFS (HR 0.69, 95% CI 0.58 to 0.82) and response rates (RR 3.29, 95% CI 2.24 to 4.84) but increased side effects. Gemcitabine-containing multi-drug combinations (GEMOXEL or cisplatin/epirubicin/5FU/gemcitabine) improved OS (HR 0.55, 95% CI 0.39 to 0.79, low-quality evidence), PFS (HR 0.43, 95% CI 0.30 to 0.62) and QOL.We did not find any survival advantages when comparing 5FU combinations to 5FU alone.

AUTHORS' CONCLUSIONS

Combination chemotherapy has recently overtaken the long-standing gemcitabine as the standard of care. FOLFIRINOX and gemcitabine plus nab-paclitaxel are highly efficacious, but our analysis shows that other combination regimens also offer a benefit. Selection of the most appropriate chemotherapy for individual patients still remains difficult, with clinicopathological stratification remaining elusive. Biomarker development is essential to help rationalise treatment selection for patients.

Efficacy of PI3K/AKT/mTOR pathway inhibitors for the treatment of advanced solid cancers: A literature-based meta-analysis of 46 randomised control trials

Background

The phosphatidylinositol-3- kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway (PI3K/AKT/mTOR pathway) plays a key role in cancer. We performed this meta-analysis to assess the clinical effect of using PI3K/AKT/mTOR pathway inhibitors on advanced solid tumours.

Methods

All the randomised controlled trials (RCT) that compared the therapy with PI3K/AKT/mTOR pathway inhibitors with other therapies were included. The main end-point was progression-free survival (PFS); other end-points included overall survival (OS) and objective response rate (ORR). A subgroup analysis was performed mainly for PFS.

Results

In total, 46 eligible RCT were included. The pooled results showed that PI3K/AKT/mTOR pathway inhibitor-based regimens significantly improved the PFS of patients with advanced solid tumours (hazard ratios (HR) = 0.79; 95% confidence intervals (CI): 0.71–0.88) and PI3K pathway mutations (HR = 0.69; 95% CI: 0.56–0.85). All single PI3K/AKT/mTOR pathway inhibitor therapies were compared with other targeted therapies (HR = 0.99; 95% CI: 0.93–1.06) and dual targeted therapies, including PI3K/AKT/mTOR pathway inhibitors and other targeted therapies (HR = 1.04; 95% CI: 0.62–1.74), which showed no significant differences in the PFS. Additional PI3K/AKT/mTOR pathway inhibitors showed no advantage with respect to the OS (HR = 0.98; 95% CI: 0.90–1.07) or ORR (risk ratio (RR) = 1.02; 95% CI: 0.87–1.20).

Conclusion

Our meta-analysis results suggest that the addition of the PI3K pathway inhibitors to the therapy regiment for advanced solid tumours significantly improves PFS. The way that patients are selected to receive the PI3K pathway inhibitors might be more meaningful in the future.

Protein kinase C (PKC) isoforms in cancer, tumor promotion and tumor suppression

The AGC family of serine/threonine kinases (PKA, PKG, PKC) includes more than 60 members that are critical regulators of numerous cellular functions, including cell cycle and differentiation, morphogenesis, and cell survival and death. Mutation and/or dysregulation of AGC kinases can lead to malignant cell transformation and contribute to the pathogenesis of many human diseases. Members of one subgroup of AGC kinases, the protein kinase C (PKC), have been singled out as critical players in carcinogenesis, following their identification as the intracellular receptors of phorbol esters, which exhibit tumor-promoting activities. This observation attracted the attention of researchers worldwide and led to intense investigations on the role of PKC in cell transformation and the potential use of PKC as therapeutic drug targets in cancer diseases. Studies demonstrated that many cancers had altered expression and/or mutation of specific PKC genes. However, the causal relationships between the changes in PKC gene expression and/or mutation and the direct cause of cancer remain elusive. Independent studies in normal cells demonstrated that activation of PKC is essential for the induction of cell activation and proliferation, differentiation, motility, and survival. Based on these observations and the general assumption that PKC isoforms play a positive role in cell transformation and/or cancer progression, many PKC inhibitors have entered clinical trials but the numerous attempts to target PKC in cancer has so far yielded only very limited success. More recent studies demonstrated that PKC function as tumor suppressors, and suggested that future clinical efforts should focus on restoring, rather than inhibiting, PKC activity. The present manuscript provides some historical perspectives on the tumor promoting function of PKC, reviewing some of the observations linking PKC to cancer progression, and discusses the role of PKC in the pathogenesis of cancer diseases and its potential usage as a therapeutic target.

A pharmacokinetic and safety study of a fixed oral dose of enzastaurin HCl in native Chinese patients with refractory solid tumors and lymphoma

Purpose

This study was conducted to assess the pharmacokinetics and safety of enzastaurin in native Chinese patients with refractory solid tumors and lymphoma.

Methods

Eligible patients received 500 mg of enzastaurin orally once daily. The pharmacokinetics of enzastaurin and its metabolites were assessed on days 14 to 18. Patients were allowed to continue receiving the agent in a safety extension phase until disease progression or presentation with unacceptable toxicity.

Results

Twenty-five patients received at least 1 dose of enzastaurin, and twenty-one patients completed the pharmacokinetic phase. Fifteen patients entered the safety extension phase. Except for transient, asymptomatic grade 3 QT interval prolongation in one patient who had baseline grade 2 QT prolongation, other adverse events were of grade 1 to 2. The t_1/2, C_{av, ss,} and AUC_{τ, ss} for enzastaurin and its primary active metabolite LSN326020 were 14 and 42 h, 1,210 and 907 nmol/L, and 29,100 and 21,800 nmol•h/L, respectively. One patient with relapsed diffuse large B-cell lymphoma achieved a partial response that lasted for 8.1 months.

Conclusions

The pharmacokinetics of enzastaurin in Chinese cancer patients were consistent with those observed in previous studies abroad. Enzastaurin 500 mg daily was well tolerated by Chinese patients. We recommend 500 mg daily as the phase II dose in this population. Its efficacy in lymphoma deserves further investigation.

Trial Registration

ClinicalTrials.gov: NCT01432951

Molecular targeted therapy for pancreatic adenocarcinoma: A review of completed and ongoing late phase clinical trials

Molecular targeted therapy is widely utilized and effective in a number of solid tumors. In pancreatic adenocarcinoma, targeted therapy has been extensively evaluated; however, survival improvement of this aggressive disease using a targeted strategy has been minimal. The purpose of this study is to review therapeutic molecular targets in completed and ongoing later phase (II and III) clinical trials to have a better understanding of the rationale and progress towards targeted molecular therapies for pancreatic cancer. The PubMed database and the NCDI clinical trial website (www.clinicaltrials.gov) were queried to identify phase II and III completed and published (PubMed) and ongoing (clinicaltrials.gov) trials using the keywords: pancreatic cancer and molecular targeted therapy. The search engines were further limited by adding Phase II or III, active enrollment and North American. A total of 14 completed and published phase II/III clinical trials and 17 ongoing trials were identified. Evaluated strategies included inhibition of growth factor receptors (EGFR, PDGFR, VGFR, IGF-1R), tyrosine kinase inhibitors, MEK1/2, mTOR blockade and PI3K and HER2-neu pathway inhibitors. Only one trial conducted by the National Cancer Institute of Canada and the PANTAR trial have demonstrated a survival improvement from EGFR inhibition using erlotinib. These trials ultimately led to FDA approval of erlotinib/Tarceva in advanced stage disease. It remains unclear whether new combinations of cytotoxic chemotherapy or immunotherapy plus molecular targeted therapy will be beneficial in management of pancreatic adenocarcinoma. Despite a number of phase II and III trials, to date, only erlotinib has emerged as an approved targeted therapy in pancreatic adenocarcinoma. There are several ongoing late phase trials evaluating a number of targets, the results of which will become available over the next 1 to 2 years.

Systematic review and meta-analysis on targeted therapy in advanced pancreatic cancer

AIM

A systematic review and meta-analysis from literature has been performed to assess the impact of targeted therapy in advanced pancreatic cancer.

METHODS

By searching different literature databases and major cancer meetings proceedings, data from all randomized clinical trials designed to investigate molecular targeted agents in the treatment of advanced pancreatic cancer were collected. The time-frame between January 2007 and March 2015 was selected. Data on predefined end-points, including overall survival, progression-free survival in terms of Hazard Ratio and response-rate were extracted and analyzed by a random effects model. Pooled data analysis was performed according to the DerSimonian and Laird test. The occurrence of publication bias was investigated through Begg's test by visual inspection of funnel plots.

RESULTS

Twenty-seven randomized clinical trials for a total of 8205 patients were selected and included in the final analysis. A significant benefit was demonstrated for anti-EGFR agents on overall survival (HR = 0.880; 95% confidence interval (CI) 0.797-0.972; p = 0.011). In the pooled analysis no benefit on overall survival (OS: pooled HR = 0.957; 95%CI 0.900-1.017; p = 0.153), or progression-free survival (PFS: pooled HR = 0.908; 95%CI 0.817-1.010; p = 0.075) for targeted-based therapies as compared to conventional treatments could be demonstrated. No advantage was reported in response-rate (OR for RR = 1.210; 95%CI 0.990-1.478; p = 0.063). Begg's funnel plot showed no evidence of publication bias.

CONCLUSION

The use of molecular targeted agents does not translate into clinical benefit. Therefore, our work highlights the need to identify predictive factors for patient selection and rationally designed clinical trials.

Does chemotherapy improve health-related quality of life in advanced pancreatic cancer? A systematic review

Chemotherapy is increasingly being used in advanced pancreatic cancer, but side-effects are common. The aim of this systematic review was to assess whether chemotherapy improves health-related quality of life (HRQoL), pain or cachexia. Thirty studies were reviewed. Four of 23 studies evaluating HRQoL, 7 of 24 studies evaluating pain and 0 of 8 studies evaluating cachexia found differences between treatment arms. Change in HRQoL from baseline was evaluated in 14 studies: five studies reported an improvement in at least one treatment arm; three a worsening and the remaining stable scores. Change in pain intensity from baseline was evaluated in eight studies, and improvement was observed in seven. Of the four studies reporting improved survival, three reported improved HRQoL or pain. In conclusion, chemotherapy can stabilize HRQoL and improve pain control. Effects on cachexia are hard to elucidate. Improved survival does not come at the expense of HRQoL or pain control.

Analysis of Response-Related and Time-to-event Endpoints in Randomized Trials of Gemcitabine-Based Treatment Versus Gemcitabine Alone as First-Line Treatment of Patients With Advanced Pancreatic Cancer

BACKGROUND

Gemcitabine-based combinations in advanced pancreatic cancer have been reported to have superior activity compared with gemcitabine alone. The results of the commonly used endpoints of clinical trials after chemotherapy or targeted therapy have been poorly reported.

METHODS AND MATERIALS

We performed a search of randomized trials of systemic treatment that included gemcitabine plus chemotherapy or targeted therapy versus gemcitabine alone. For selected trials, the differences between the treatment arms for every endpoint were calculated, and a correlation analysis between these differences and the differences in overall survival was performed for every intermediate endpoint. Whenever a correlation coefficient was significant, regression analysis was performed. Finally, an analysis was performed to evaluate the factors that could mediate and moderate the effect of progression-free survival on overall survival.

RESULTS

In addition to overall survival, progression-free survival, the overall response rate, and the disease control rate were the most frequently reported endpoints. Of the possible surrogate endpoints of overall survival, progression-free survival appears to be a reliable endpoint to assess chemotherapy (R(2) = 0.646) and chemotherapy plus targeted therapy (R(2) = 0.530) regimens and the disease control rate to assess chemotherapy (R(2) = 0.569). Of the factors that could limit the effect of progression-free survival on overall survival, the interval of radiologic evaluation could play a role.

CONCLUSION

In the selected trials, progression-free survival and the disease control rate were the most reliable surrogate endpoints of overall survival. Similar to the time-to-event endpoints, a standardization of response-related endpoints is strongly recommended.

Phase II clinical trials on investigational drugs for the treatment of pancreatic cancers

INTRODUCTION

Despite some recent advances in treatment options, pancreatic cancer remains a devastating disease with poor outcomes. In a trend contrary to most malignancies, both incidence and mortality continue to rise due to pancreatic cancer. The majority of patients present with advanced disease and there are no treatment options for this stage that have demonstrated a median survival > 1 year. As the penultimate step prior to Phase III studies involving hundreds of patients, Phase II clinical trials provide an early opportunity to evaluate the efficacy of new treatments that are desperately needed for this disease.

AREAS COVERED

This review covers the results of published Phase II clinical trials in advanced pancreatic adenocarcinoma published within the past 5 years. The treatment results are framed in the context of the current standards of care and the historic challenge of predicting Phase III success from Phase II trial results.

EXPERT OPINION

Promising therapies remain elusive in pancreatic cancer based on recent Phase II clinical trial results. Optimization and standardization of clinical trial design in the Phase II setting, with consistent incorporation of biomarkers, is needed to more accurately identify promising therapies that warrant Phase III evaluation.

New targeted therapies in pancreatic cancer

Patients with pancreatic cancer have a poor prognosis with a median survival of 4-6 mo and a 5-year survival of less than 5%. Despite therapy with gemcitabine, patient survival does not exceed 6 mo, likely due to natural resistance to gemcitabine. Therefore, it is hoped that more favorable results can be obtained by using guided immunotherapy against molecular targets. This review summarizes the new leading targeted therapies in pancreatic cancers, focusing on passive and specific immunotherapies. Passive immunotherapy may have a role for treatment in combination with radiochemotherapy, which otherwise destroys the immune system along with tumor cells. It includes mainly therapies targeting against kinases, including epidermal growth factor receptor, Ras/Raf/mitogen-activated protein kinase cascade, human epidermal growth factor receptor 2, insulin growth factor-1 receptor, phosphoinositide 3-kinase/Akt/mTOR and hepatocyte growth factor receptor. Therapies against DNA repair genes, histone deacetylases, microRNA, and pancreatic tumor tissue stromal elements (stromal extracellular matric and stromal pathways) are also discussed. Specific immunotherapies, such as vaccines (whole cell recombinant, peptide, and dendritic cell vaccines), adoptive cell therapy and immunotherapy targeting tumor stem cells, have the role of activating antitumor immune responses. In the future, treatments will likely include personalized medicine, tailored for numerous molecular therapeutic targets of multiple pathogenetic pathways.

Targeting protein kinase C subtypes in pancreatic cancer

In preclinical studies, protein kinase C (PKC) enzymes have been implicated in regulating many aspects of pancreatic cancer development and progression. However, clinical Phase I or Phase II trials with compounds targeting classical PKC isoforms were not successful. Recent studies implicate that mainly atypical and novel PKC enzymes regulate oncogenic signaling pathways in pancreatic cancer. Members of these two subgroups converge signaling induced by mutant Kras, growth factors and inflammatory cytokines. Different approaches for the development of inhibitors for atypical PKC and novel PKC have been described; and new compounds include allosteric inhibitors and inhibitors that block ATP binding.

A phase 1 and pharmacokinetic study of enzastaurin in pediatric patients with refractory primary central nervous system tumors: a pediatric brain tumor consortium study

BACKGROUND

We sought to estimate the maximum tolerated or recommended phase 2 dose and describe the pharmacokinetics and toxicities of enzastaurin, an oral inhibitor of protein kinase Cβ, in children with recurrent central nervous system malignancies.

METHODS

Enzastaurin was administered continuously once daily at 3 dose levels (260, 340, and 440 mg/m(2)) and twice daily at 440 mg/m(2)/day. Plasma pharmacokinetics were evaluated following a single dose and at steady state. Inhibition of protein kinase C and Akt cell signaling in peripheral blood mononuclear cells was evaluated. Akt pathway activity was measured in pretreatment tumor samples.

RESULTS

Thirty-three patients enrolled; 1 was ineligible, and 3 were nonevaluable secondary to early progressive disease. There were no dose-limiting toxicities during the dose-finding phase. Two participants receiving 440 mg/m(2) given twice daily experienced dose-limiting toxicities of grade 3 thrombocytopenia resulting in delayed start of course 2 and grade 3 alanine transaminase elevation that did not recover within 5 days. There were no grade 4 toxicities during treatment. The concentration of enzastaurin increased with increasing dose and with continuous dosing; however, there was not a significant difference at the 440 mg/m(2) dosing level when enzastaurin was administered once daily versus twice daily. There were no objective responses; however, 11 participants had stable disease >3 cycles, 7 with glioma, 2 with ependymoma, and 2 with brainstem glioma.

CONCLUSION

Enzastaurin was well tolerated in children with recurrent CNS malignancies, with chromaturia, fatigue, anemia, thrombocytopenia, and nausea being the most common toxicities. The recommended phase 2 dose is 440 mg/m(2)/day administered once daily.

Personalising pancreas cancer treatment: When tissue is the issue

The treatment of advanced pancreatic cancer has not moved much beyond single agent gemcitabine until recently when protocols such as FOLFIRINOX (fluorouracil, leucovorin, irinotecan and oxaliplatin) and nab-paclitaxel-gemcitabine have demonstrated some improved outcomes. Advances in technology especially in massively parallel genome sequencing has progressed our understanding of the biology of pancreatic cancer especially the candidate signalling pathways that are involved in tumourogenesis and disease course. This has allowed identification of potentially actionable mutations that may be targeted by new biological agents. The heterogeneity of pancreatic cancer makes tumour tissue collection important with the aim of being able to personalise therapies for the individual as opposed to a one size fits all approach to treatment of the condition. This paper reviews the developments in this area of translational research and the ongoing clinical studies that will attempt to move this into the everyday oncology practice.

Comparison of gemcitabine combined with targeted agent therapy versus gemcitabine monotherapy in the management of advanced pancreatic cancer

PURPOSE

Targeted therapy has brought great clinical benefits for patients with multiple solid tumors, but its effects in patients with locally advanced/metastatic pancreatic cancer (LA/MPC) are disputed. This systematic evaluation compared the efficacy and safety profiles of gemcitabine combined with targeted agents (GEM + TA) versus gemcitabine administered as monotherapy or combined with placebo (GEM ± PLC) in LA/MPC patients.

METHODS

PubMed and EMBASE were searched for relevant randomized controlled trials published on or before April 30, 2013. The primary end points were overall survival (OS) and progression-free survival (PFS); the secondary end points were 1-year survival rate, objective response rate (ORR), and toxicity rates (TRs), defined as the prevalence of grade 3/4 adverse events. The systematic evaluation was performed by using Review Manager version 5.1.7.

FINDINGS

A total of 10 randomized controlled trials involving 3899 patients (2195 males; mean age, 63.6 years) were included in the systematic evaluation. The results reported that there was no significant difference in OS (hazard ratio [HR] = 0.97 [P = 0.85]), PFS (HR = 0.95 [P = 0.14]), or ORR (odds ratio [OR] = 0.95 [P = 0.69]) between GEM + TA and GEM ± PLC. However, a marginal difference in 1-year survival rate (OR = 0.80 [P = 0.05]) between the 2 groups was observed. The grade 3/4 TRs of anemia, diarrhea, nausea, neutropenia, thrombocytopenia, and vomiting were not significantly different between the 2 groups. However, the prevalence of grade 3/4 rash was significantly greater in the GEM + TA group (OR = 8.31 [P < 0.01]).

IMPLICATIONS

Based on the results from this analysis, the addition of targeted agents to a regimen of gemcitabine treatment does not bring survival benefits except 1-year survival rate to patients with LA/MPC.

Modulation of pancreatic tumor potential by overexpression of protein kinase C β1

OBJECTIVE

This study aimed to investigate whether the overexpression of protein kinase C β1 (PKCβ1) is able to modulate the malignant phenotype displayed by the human ductal pancreatic carcinoma cell line PANC1.

METHODS

PKCβ1 overexpression was achieved using a stable transfection approach. PANC1-PKCβ1 and control cells were analyzed both in vitro and in vivo.

RESULTS

PANC1-PKCβ1 cells displayed a lower growth capacity associated with the down-regulation of the MEK/ERK pathway and cyclin expression. Furthermore, PKCβ1 overexpression was associated with an enhancement of cell adhesion to fibronectin and with reduced migratory and invasive phenotypes. In agreement with these results, PANC1-PKCβ1 cells showed an impaired ability to secrete proteolytic enzymes. We also found that PKCβ1 overexpressing cells were more resistant to cell death induced by serum deprivation, an event associated with G0/G1 arrest and the modulation of PI3K/Akt and NF-κB pathways. Most notably, the overexpression of PKCβ1 completely abolished the ability of PANC1 cells to induce tumors in nude mice.

CONCLUSIONS

Our results established an important role for PKCβ1 in PANC1 cells suggesting it would act as a suppressor of tumorigenic behavior in pancreatic cancer.

Randomized, Phase II, Placebo-Controlled, Double-Blind Study With and Without Enzastaurin in Combination With Paclitaxel and Carboplatin As First-Line Treatment Followed by Maintenance Treatment in Advanced Ovarian Cancer

Purpose

Enzastaurin is an oral serine/threonine kinase inhibitor antitumor agent. Our phase II trial tested the efficacy and safety of enzastaurin added to a standard carboplatin/paclitaxel chemotherapy regimen in patients with newly diagnosed advanced ovarian cancer.

Patients and Methods

This was a randomized, placebo-controlled study in patients with International Federation of Gynecology and Obstetrics stage IIB to IV ovarian, fallopian tube, or peritoneal epithelial carcinoma. Patients were randomly assigned to six cycles of chemotherapy (paclitaxel/carboplatin ± enzastaurin [PCE/PC]) followed by maintenance therapy (enzastaurin/placebo). Primary end point was progression-free survival (PFS). Secondary measures included response rate, safety assessment, and translational research.

Results

A total of 142 patients were randomly assigned to PCE (n = 69) or PC (n = 73). Patients in the PCE group had a 3.7-month longer median PFS compared with patients in the PC group; this was not statistically significant (hazard ratio [HR], 0.80; 95% CI, 0.50 to 1.29; P = .37). Safety profiles of the treatment arms were comparable. Frequency of discontinuation because of adverse events was similar (PCE, 11.9%; PC, 9.7%). Multivariate analyses confirmed the importance of optimal debulking with regard to PFS (debulking optimal v suboptimal: HR, 0.51; 95% CI, 0.30 to 0.85; P = .009). HR for covariate stage (stage IIB to IIIB v IIIC to IV) was not statistically significant (0.75; 95% CI, 0.38 to 1.47; P = .40). Translational research of immunohistochemistry protein assays did not identify any markers significantly associated with treatment difference regarding PFS.

Conclusion

The PCE combination increased PFS, but it was not significantly superior to PC in this phase II study.

Molecularly targeted therapies in metastatic pancreatic cancer: a systematic review

Pancreatic cancer is the fourth leading cause of cancer-related death. Most patients present with an advanced stage of disease that has a dismal outcome, with a median survival of approximately 6 months. Evidently, there is a clear need for the development of new agents with novel mechanisms of action in this disease. A number of biological agents modulating different signal transduction pathways are currently in clinical development, inhibiting angiogenesis and targeting epidermal growth factor receptor, cell cycle, matrix metalloproteinases, cyclooxygenase-2, mammalian target of rapamycin, or proteasome. This is the first systematic review of the literature to synthesize all available data coming from trials and evaluate the efficacy and safety of molecular targeted drugs in unresectable and metastatic pancreatic cancer. However, it should be stressed that although multiple agents have been tested, only 9 phase 3 trials have been conducted and one agent (erlotinib) has been approved by the Food and Drug Administration for use in clinical practice. As knowledge accumulates on the molecular mechanisms underlying carcinogenesis in the pancreas, the anticipated development and assessment of molecularly targeted agents may offer a promising perspective for a disease which, to date, remains incurable.

Toward the goal of personalized therapy in pancreatic cancer by targeting the molecular phenotype

The purpose of this article is to provide a critical review of the molecular alterations in pancreatic cancer that are clinically investigated as therapeutic targets and their potential impact on clinical outcomes. Adenocarcinoma of exocrine pancreas is generally associated with poor prognosis and the conventional therapies are marginally effective. Advances in understanding the genetic regulation of normal and neoplastic development of pancreas have led to development and clinical evaluation of new therapeutic strategies that target the signaling pathways and molecular alterations in pancreatic cancer. Applications have begun to utilize the genetic targets as biomarkers for prediction of therapeutic responses and selection of treatment options. The goal of accomplishing personalized tumor-specific therapy with tolerable side effects for patients with pancreatic cancer is hopefully within reach in the foreseeable future.

Does gemcitabine-based combination therapy improve the prognosis of unresectable pancreatic cancer?

AIM: To assess whether gemcitabine-based combination therapy improves the prognosis of unresectable pancreatic cancer compared with gemcitabine treatment alone.

METHODS: A quantitative up-to-date meta-analysis was undertaken to investigate the efficacy of gemcitabine-based combination treatment compared with gemcitabine monotherapy in locally advanced or metastatic pancreatic cancer. Inclusion was limited to high-quality randomized clinical trials.

RESULTS: Twenty-six studies were included in the present analysis, with a total of 8808 patients recruited. The studies were divided into four subgroups based on the different kinds of cytotoxic agents, including platinum, fluoropyrimidine, camptothecin and targeted agents. Patients treated with gemcitabine monotherapy had significantly lower objective response rate [risk ratio (RR), 0.72; 95% confidence interval (CI): 0.63-0.83; P < 0.001], and lower 1-year overall survival (RR, 0.90; 95%CI: 0.82-0.99; P = 0.04). Gemcitabine monotherapy caused fewer complications, including fewer grade 3-4 toxicities: including vomiting (RR, 0.75; 95%CI: 0.62-0.89; P = 0.001), diarrhea (RR, 0.66; 95%CI: 0.49-0.89; P = 0.006), neutropenia (RR, 0.88; 95%CI: 0.72-1.06; P = 0.18), anemia (RR, 0.96; 95%CI: 0.82-1.12; P = 0.60), and thrombocytopenia (RR, 0.76; 95%CI: 0.60-0.97; P = 0.03) compared with gemcitabine combination therapies.

CONCLUSION: Gemcitabine combination therapy provides a modest improvement of survival, but is associated with more toxicity compared with gemcitabine monotherapy.

Role of gemcitabine-based combination therapy in the management of advanced pancreatic cancer: a meta-analysis of randomised trials

BACKGROUND

Pancreatic cancer is the fourth leading cause of cancer-related death worldwide. Gemcitabine is the mainstay treatment for advanced disease. However, almost all up-to-date trials, that evaluated the benefit of gemcitabine-combination schedules, failed to demonstrate an improvement in overall survival (OS). In this study, we performed a systematic review and a meta-analysis of randomised clinical trials (RCTs) to investigate the efficacy and safety of gemcitabine-based combination regimens as compared to gemcitabine alone in the management of pancreatic cancer.

METHODS

Clinical trials were collected by searching different databases (PubMed, Embase and the Central Registry of Controlled Trials of the Cochrane Library) and abstracts from major cancer meetings. We considered period ranging from January 1997 to January 2012. Primary end-point was OS, secondary end-points were response rate (RR), disease control rate (DCR) and safety. Hazard ratios (HRs) of OS, odds-ratios (ORs) of RR, DCR and risk ratios of grade 3-4 toxicity rates (TRs), were extracted as presented in retrieved studies and used for statistical analysis. Meta-analytic estimates were derived using random-effects model.

FINDINGS

Thirty-four trials for a total of 10,660 patients were selected and included in the final analysis. The analysis showed that combination chemotherapy confers benefit in terms of OS (HR: 0.93; 95% confidence interval (CI): 0.89-0.97; p=0.001). ORs for both RR and DCR demonstrated a significant advantage for combination therapy (OR for RR: 0.60, 95%CI: 0.47-0.76, p<0.001; OR for DCR: 0.79; 95%CI: 0.66-0.93; p=0.006). Toxicities were more frequent with the combination treatment and significance in terms of risk ratio was reached for diarrhoea (0.53, 95%CI: 0.36-0.79), nausea (0.74, 95%CI: 0.56-0.96), neutropenia (0.71, 95%CI: 0.59-0.85) and thrombocytopenia (0.57, 95%CI: 0.43-0.75).

INTERPRETATION

The combination chemotherapy as compared to gemcitabine alone significantly improves OS in advanced pancreatic cancer (APC). However, this advantage is marginal whereas the treatment-related toxicity is increased, suggesting the use of gemcitabine-based combination regimens only in selected patient populations. New prospective trials, based on translational approaches and innovative validated biomarkers, are eagerly awaited on this topic.

Overcoming nucleoside analog chemoresistance of pancreatic cancer: a therapeutic challenge

Clinical refractoriness to nucleoside analogs (e.g., gemcitabine, capecitabine) is a major scientific problem and is one of the main reasons underlying the extremely poor prognostic state of pancreatic cancer. The drugs' effects are suboptimal partly due to cellular mechanisms limiting their transport, activation, and overall efficacy. Nonetheless, novel therapeutic approaches are presently under study to circumvent nucleoside analog resistance in pancreatic cancer. With these new approaches come additional challenges to be addressed. This review describes the determinants of chemoresistance in the gemcitabine cytotoxicity pathways, provides an overview of investigational approaches for overcoming chemoresistance, and discusses new challenges presented. Understanding the future directions of the field may assist in the successful development of novel treatment strategies for enhancing chemotherapeutic efficacy in pancreatic cancer.

Downregulation of the CCK-B receptor in pancreatic cancer cells blocks proliferation and promotes apoptosis

Gastrin stimulates the growth of pancreatic cancer cells through the activation of the cholecystokinin-B receptor (CCK-BR), which has been found to be overexpressed in pancreatic cancer. In this study, we proposed that the CCK-BR drives growth of pancreatic cancer; hence, interruption of CCK-BR activity could potentially be an ideal target for cancer therapeutics. The effect of CCK-BR downregulation in the human pancreatic adenocarcinoma cells was examined by utilizing specific CCK-BR-targeted RNA interference reagents. The CCK-BR receptor expression was both transiently and stably downregulated by transfection with selective CCK-BR small-interfering RNA or short-hairpin RNA, respectively, and the effects on cell growth and apoptosis were assessed. CCK-BR downregulation resulted in reduced cancer cell proliferation, decreased DNA synthesis, and cell cycle arrest as demonstrated by an inhibition of G(1) to S phase progression. Furthermore, CCK-BR downregulation increased caspase-3 activity, TUNEL-positive cells, and decreased X-linked inhibitor of apoptosis protein expression, suggesting apoptotic activity. Pancreatic cancer cell mobility was decreased when the CCK-BR was downregulated, as assessed by a migration assay. These results show the importance of the CCK-BR in regulation of growth and apoptosis in pancreatic cancer. Strategies to decrease the CCK-BR expression and activity may be beneficial for the development of new methods to improve the treatment for patients with pancreatic cancer.

Targeting protein kinase C by Enzastaurin restrains proliferation and secretion in human pancreatic endocrine tumors

Dysregulation of the protein kinase C (PKC) signaling pathway has been implicated in tumor progression. In this study, we investigate the effects of a PKC inhibitor, Enzastaurin, in human pancreatic neuroendocrine neoplasms (PNN) primary cultures and in the human pancreatic endocrine cancer cell line, BON1. To this aim six human PNN dispersed in primary cultures and BON1 cells were treated without or with 1-10 μM Enzastaurin and/or 100 nM IGF1 in the presence or absence of serum. Cell viability and apoptosis were evaluated after 48-72 h; Chromogranin A (CgA) and/or insulin secretion was assessed after 6 h of incubation. PKC expression was investigated by immunofluorescence and western blot. We found that Enzastaurin significantly reduced human PNN primary culture cell viability, as well as CgA and insulin secretion. Moreover, in the BON1 cell line Enzastaurin inhibited cell proliferation at 5 and 10 μM by inducing caspase-mediated apoptosis, and reduced phosphorylation of glycogen synthetase kinase 3β (GSK3β) and of Akt, both downstream targets of PKC pathway and pharmacodynamic markers for Enzastaurin. In addition, Enzastaurin blocked the stimulatory effect of IGF1 on cell proliferation, and reduced CgA expression and secretion in BON1 cells. Two different PKC isoforms are expressed at different levels and have partially different subcellular localization in BON1 cells. In conclusion, Enzastaurin reduces cell proliferation by inducing apoptosis, with a mechanism likely involving GSK3β signaling, and inhibits secretory activity in PNN in vitro models, suggesting that Enzastaurin might represent a possible medical treatment of human PNN.

A Gynecologic Oncology Group phase II trial of the protein kinase C-beta inhibitor, enzastaurin and evaluation of markers with potential predictive and prognostic value in persistent or recurrent epithelial ovarian and primary peritoneal malignancies

OBJECTIVES

Protein kinase C (PKC) activation contributes to proliferation and angiogenesis in epithelial ovarian or primary peritoneal carcinoma (EOC/PPC). A multi-institutional phase II trial was conducted to evaluate the efficacy and safety of PKCβ inhibitor enzastaurin in persistent or recurrent EOC/PPC and to explore potential prognostic and predictive biomarkers.

METHODS

Eligible women with measurable platinum-sensitive and resistant EOC/PPC were treated with continuous administration of oral enzastaurin until disease progression or unacceptable toxicity. A two-stage sequential design was used to evaluate progression-free survival (PFS) ≥6-months, tumor response, and toxicity. Translational studies included sequencing of the TP53, PTEN, PIK3CA and PKCβII genes for somatic mutations, quantitative PCR assays for AKT2 and PTEN copy number alterations, and measurement of circulating VEGF-A plasma levels.

RESULTS

Among 27 eligible and evaluable patients, 3 women with PFS≥6-months (11%) and 2 women with partial responses (7%) were observed. One of them achieved a durable response and remains on the study. No grade 4 adverse events were observed. Most common grade 3 adverse events were constitutional (4) and gastrointestinal (3). Mutations in the TP53 gene and abnormal copy number in the PTEN gene were common (56% and 48% of cases, respectively).

CONCLUSIONS

Enzastaurin was tolerable but had insufficient activity to proceed with the second stage of accrual. However, 1 patient has been progression-free for 44 months. No association between a biomarker and response to enzastaurin has been found. Exploratory analysis suggested an association between survival and PTEN copy number losses.

Enzastaurin inhibits invasion and metastasis in lung cancer by diverse molecules

BACKGROUND

Enzastaurin (Enz) is a serine/threonine kinase inhibitor blocking protein kinase C (PKC)beta/AKT pathway. However, an ability of this compound to inhibit cancer invasion and metastasis is not yet clearly elucidated.

METHODS

The ability of Enz to inhibit invasion and metastasis, and to target molecules was investigated in non-small cell lung cancer (NSCLC) by RT-PCR validated microarray, Matrigel, and in vivo chorionallantoic membrane (CAM) assays.

RESULTS

Enzastaurin significantly reduced migration, invasion, and in vivo metastasis to lungs and liver (CAM assay) of diverse NSCLC cell lines. Genes promoting cancer progression (u-PAR, VEGFC, and HIF1alpha) and tumour suppression (VHL, RASSF1, and FHIT) of NSCLC were significantly (P<0.05) down- or upregulated after Enz treatment in H460, A549, and H1299 cells, respectively. Luciferase/chromatin immunoprecipitation analysis showed that Enz transcriptionally controls urokinase-type plasminogen activator receptor (u-PAR) expression by promoter inhibition through Sp1, Sp3, and c-Jun(AP-1). Moreover, siRNA knockdown of u-PAR re-sensitised Enz-resistant cells and induced apoptosis, suggesting u-PAR as a marker of Enz resistance.

CONCLUSION

This study shows that Enz inhibits migration, invasion, and in vivo metastasis by targeting u-PAR, besides further targeting progression-related and tumour-suppressor genes in NSCLC. Together with u-PAR being a novel putative marker of Enz response, these data encourage molecularly tailored clinical studies on Enz in NSCLC therapy.

Protein kinase C-beta gene variants, pathway activation, and enzastaurin activity in lung cancer

BACKGROUND

Protein kinase C-beta2 (PKCbeta2) is a splice-variant of the PRKCB1 gene and belongs to a family of serine/threonine-specific kinases that are predominantly activated by diacylglycerol, calcium, and phorbol ester. Cellular functions associated with PKCbeta2 activation include transformation, proliferation, and inhibition of apoptosis. Enzastaurin (LY317615) is an oral, selective, potent inhibitor of the PKCbeta2 kinase. Preclinical activity for this agent was predominantly reported in lymphoma, glioblastoma, and colorectal cancer. In patients with advanced non-small-cell lung cancer (NSCLC) whose previous therapy had failed, 13% of patients had disease control for 6 months with single-agent therapy.

PATIENTS AND METHODS

We investigated whether biologically relevant variants of PRKCB1 exist in lung cancer cell lines in the context of enzastaurin-induced proliferation and kinase inhibition, using exon sequencing, immunoblotting, and cytotoxicity assays in NSCLC and small-cell lung cancer (SCLC) cell lines.

RESULTS

We discovered a total of 6 single-nucleotide variants, but only 1 resulted in an amino acid substitution (T40I). This substitution was not located in the kinase domain of PKCbeta2 and did not affect enzastaurin's antiproliferative or phosphorylation-inhibitory activity. We found enzastaurin to be equally active in NSCLC and SCLC cell lines, with values of the 50% inhibitory concentration in a range of 0.05-0.2 microM.

CONCLUSION

The inhibition of phosphorylation of PKCbeta2 and the downstream molecules glycogen synthase kinase-3beta, S6RP, Akt, and forkhead transcription factor was evident in the same concentration range, which suggests the premise that the determination of phosphorylation levels of these molecules in human tissue specimens may be a useful pharmacodynamic parameter for in vivo target inhibition by enzastaurin.