Phase III study (MONET1) of motesanib plus carboplatin/paclitaxel in patients with advanced nonsquamous nonsmall-cell lung cancer (NSCLC): Asian subgroup analysis

BACKGROUND

This preplanned subset analysis of the phase III MONET1 study aimed to determine whether motesanib combined with carboplatin/paclitaxel (C/P) would result in improved overall survival (OS) versus chemotherapy alone, in a subset of Asian patients with nonsquamous nonsmall-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients with nonsquamous NSCLC (stage IIIB/IV or recurrent) and no prior systemic therapy for advanced disease were randomized to IV carboplatin (AUC, 6 mg/ml min) and paclitaxel (200 mg/m2) for up to six 3-week cycles, plus either oral motesanib 125 mg q.d. or placebo. Primary end point was OS; secondary end points included progression-free survival (PFS), objective response rate (ORR), and safety.

RESULTS

Two hundred twenty-seven Asian patients from MONET1 were included in this descriptive analysis. Median OS was 20.9 months in the motesanib plus C/P arm and 14.5 months in the placebo plus C/P arm (P=0.0223); median PFS was 7.0 and 5.3 months, respectively, (P=0.0004); and ORR was 62% and 27%, respectively, (P<0.0001). Grade≥3 adverse events were more common in the motesanib plus C/P arm versus placebo plus C/P (79% versus 61%).

CONCLUSION

In this preplanned subset analysis of Asian patients with nonsquamous NSCLC, motesanib plus C/P significantly improved OS, PFS, and ORR versus placebo plus C/P.

CLINICAL TRIAL NUMBER

NCT00460317.

A randomized, placebo-controlled phase 2 study of ganitumab or conatumumab in combination with FOLFIRI for second-line treatment of mutant KRAS metastatic colorectal cancer

BACKGROUND

Targeted agents presently available for mutant KRAS metastatic colorectal cancer (mCRC) are bevacizumab and aflibercept. We evaluated the efficacy and safety of conatumumab (an agonistic monoclonal antibody against human death receptor 5) and ganitumab (a monoclonal antibody against the type 1 insulin-like growth factor receptor) combined with standard FOLFIRI chemotherapy as a second-line treatment in patients with mutant KRAS mCRC.

PATIENTS AND METHODS

Patients with mutant KRAS metastatic adenocarcinoma of the colon or rectum refractory to fluoropyrimidine- and oxaliplatin-based chemotherapy were randomized 1 : 1 : 1 to receive intravenous FOLFIRI plus conatumumab 10 mg/kg (Arm A), ganitumab 12 mg/kg (Arm B), or placebo (Arm C) Q2W. The primary end point was progression-free survival (PFS).

RESULTS

In total, 155 patients were randomized. Median PFS in Arms A, B, and C was 6.5 months (HR, 0.69; P = 0.147), 4.5 months (HR, 1.01; P = 0.998), and 4.6 months, respectively; median overall survival was 12.3 months (HR, 0.89; P = 0.650), 12.4 months (HR, 1.27; P = 0.357), and 12.0 months; and objective response rate was 14%, 8%, and 2%. The most common grade ≥3 adverse events in Arms A/B/C included neutropenia (30%/25%/18%) and diarrhea (18%/2%/10%).

CONCLUSIONS

Conatumumab, but not ganitumab, plus FOLFIRI was associated with a trend toward improved PFS. Both combinations had acceptable toxicity.

A phase II, multicenter, open-label randomized study of motesanib or bevacizumab in combination with paclitaxel and carboplatin for advanced nonsquamous non-small-cell lung cancer

BACKGROUND

This phase II study estimated the difference in objective response rate (ORR) among patients with advanced nonsquamous non-small-cell lung cancer (NSCLC) receiving paclitaxel-carboplatin (CP) plus motesanib or bevacizumab.

PATIENTS AND METHODS

Chemotherapy-naive patients (N = 186) were randomized 1:1:1 to receive CP plus motesanib 125 mg once daily (qd) (arm A), motesanib 75 mg twice daily (b.i.d.) 5 days on/2 days off (arm B), or bevacizumab 15 mg/kg every 3 weeks (q3w) (arm C). The primary end point was ORR (per RECIST). Other end points included progression-free survival (PFS), overall survival (OS), motesanib pharmacokinetics, and adverse events (AEs).

RESULTS

ORRs in the three arms were as follows: arm A, 30% (95% confidence interval 18% to 43%); arm B, 23% (13% to 36%); and arm C, 37% (25% to 50%). Median PFS in arm A was 7.7 months, arm B 5.8 months, and arm C 8.3 months; median OS for arm A was 14.0 months, arm B 12.8 months, and arm C 14.0 months. Incidence of AEs was greater in arms A and B than in arm C. More grade 5 AEs not attributable to disease progression occurred in arm B (n = 10) than in arms A (n = 4) and C (n = 4). Motesanib plasma C(max) and C(min) values were consistent with its pharmacokinetic properties observed in previous studies.

CONCLUSIONS

The efficacy of 125 mg qd motesanib or bevacizumab plus CP was estimated to be comparable. Toxicity was higher but manageable in both motesanib arms. Efficacy and tolerability of motesanib 125 mg qd plus CP in advanced nonsquamous NSCLC are being further investigated in a phase III study.

Nuclear localization conferred by the pocket domain of the retinoblastoma gene product

The tumor suppressor Rb is a nuclear phosphoprotein that controls cell growth and differentiation by modulating the activity of certain transcription factors. Transport of Rb to the nucleus is affected by both a bipartite nuclear localization signal (NLS) in the C-terminus of the protein and a central domain, termed A/B or pocket, through which Rb interacts with transcription factors and viral oncoproteins. Mutations in either the A or B subdomains of the pocket render a NLS-deficient Rb completely cytoplasmic. Fusing the A/B domain of Rb to the Escherichia coli beta-galactosidase, to create betagal-A/B, confers nuclear localization upon this bacterial protein. Moreover, co-expression with the adenovirus oncoprotein, E1A, further augments nuclear localization of betagal-A/B. These findings provide direct evidence that the pocket domain of Rb is not only required but also sufficient to induce nuclear transport by a 'piggyback' mechanism. Thus, nuclear localization of Rb is dictated by two independent and autonomous domains: (i) the bipartite NLS and (ii) the pocket domain. We suggest that via these domains, Rb chaperons and co-compartmentalizes with its associated factors and preempts their activity prior to nuclear transport.

Stimulation of MAP kinase and S6 kinase by vanadium and selenium in rat adipocytes

To explore the mechanism underlying the insulin-mimetic actions of vanadium and selenium we examined their effects on the mitogen activated protein/myelin basic protein kinases (MAPK) and ribosomal S6 protein kinases, which are among the best characterized of the kinases that comprise the phosphorylation cascade in insulin signal transduction. We observed a transient activation of MAPK and S6 kinases by insulin in rat adipocytes, while both sodium selenate and vanadyl sulphate produced prolonged activation of the kinases. Vanadyl sulphate stimulated the activity of MAPK and S6 kinase by as much as 6 fold and 15 fold, respectively. Pretreatment of the cells with genistein did not affect the activation of MAPK by insulin, but partially blocked the effects of sodium selenate and vanadyl sulphate. Genistein did not change the activation of S6 kinase by insulin, but blocked the activation in vanadyl sulphate- and sodium selenate-treated-cells, suggesting that a genistein sensitive tyrosine kinase may be involved in the activation by these two compounds. Rapamycin, a specific inhibitor of the p70s6k isoform of S6 kinase, partially reduced the activation of S6 kinase activity by sodium selenate, indicating a role for this kinase in the overall activity of the S6 kinase in sodium selenate-treated cells. A similar trend was noted in vanadyl sulphate-treated cells. Thus, this study supports the involvement of MAPK and S6 kinases in the insulin-mimetic actions of vanadium and selenium.

Loss of Rb and Myc activation co-operate to suppress cyclin D1 and contribute to transformation

Cyclin D1 can bind and phosphorylate the product (pRb) of the retinoblastoma gene (RB-1) and recent evidence suggests pRb, in turn, may regulate cyclin D1 protein expression. In transformed cell lines, loss of pRb activity strongly correlates with a decrease in cyclin D1 protein expression, and conversely, introduction of pRb can induce cyclin D1 promoter activity. We show here that pRb does not regulate cyclin D1 directly as basal and serum-stimulated levels of cyclin D1 protein and kinase activity are similar in wildtype and pRb-deficient primary mouse embryonic fibroblasts (MEFs). These observations suggest that the suppression of cyclin D1 in pRb-minus tumour cell lines requires both loss of pRb and at least one additional genetic event. We have determined that constitutive, ectopic Myc expression in pRb-deficient, but not wildtype, MEFs suppresses cyclin D1 protein expression and kinase activity. Regulation is evident at either the level of RNA or protein expression. Phenotypically, pRb-deficient MEFs consistently exhibited a delayed growth response in comparison to wildtype MEFs. This growth delay is abrogated in pRb-deficient MEFs which are expressing ectopic Myc protein, coincident with the loss of cyclin D1 protein expression. Moreover, these cells exhibit an increased proliferative capacity, and they no longer show contact inhibition. Our results support a cross-regulatory mechanism between Myc, pRb and cyclin D1 and suggest a novel role for cyclin D1 in tumorigenesis.

Skeletal muscle mitogen-activated protein kinases and ribosomal S6 kinases. Suppression in chronic diabetic rats and reversal by vanadium

The mitogen-activated protein (MAP) kinases and ribosomal S6 protein kinases in the skeletal muscle of insulin-resistant long-term (2 and 6 months' duration) diabetic rats were investigated to understand further the changes in insulin intracellular signaling pathways that accompany diabetes. The effects of insulin-mimetic vanadium compounds on the activity of these kinases were also examined. In the insulin-resistant 2-month diabetic rats, the basal activities of MAP kinases were relatively unchanged, while the basal activities of S6 kinases were significantly increased. Intravenous injection of insulin moderately activated both the 42-kDa MAP kinase (p42mapk) and a 44-kDa MAP kinase (p44erk1) in the 2-month control rats but not in the 2-month diabetic rats. Insulin treatment markedly stimulated the activity of a novel 31-kDa S6 kinase and the previously described 90-kDa ribosomal S6 kinase encoded by one of the rsk genes (p90rsk) in the 2-month control rats, while the effect was substantially reduced in the diabetic rats. In the 6-month diabetic rats, the basal phosphotransferase activities of both MAP kinases were depressed threefold or greater. This correlated with reductions in the amount of immunoreactive p42mapk and p44erk1 proteins in extracts from the diabetic rats. The basal activity of the 31-kDa S6 kinase activity was also reduced fourfold in the 6-month diabetic rats. Treatment of the 2-month diabetic rats with vanadyl sulfate resulted in euglycemia, prevented the increase in the basal activity of S6 kinase, and improved the activation of S6 kinase by insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and characterization of a novel ribosomal S6 kinase from skeletal muscle of insulin-treated rats

The predominant 40 S ribosomal protein S6 kinase in skeletal muscle extracts from insulin-treated rats was purified over 10,000-fold to near homogeneity with approximately 4.5% recovery of starting activity. This S6 kinase was resolved from the catalytic subunit of cAMP-dependent protein kinase only by the seventh and final column chromatography step. The purified S6 kinase migrated as a tight doublet of approximately 31 kDa on an SDS-polyacrylamide gel, and it was eluted from gel filtration columns with a similar apparent M(r), which indicated that the enzyme exists as a monomer. This S6 kinase was immunologically distinct from the other known insulin-activated S6 kinases, i.e. p70S6K and p90rsk. It was inhibited by [ethylenebis(oxyethylenenitrilo)]tetraacetic acid and beta-glycerophosphate at concentrations routinely used to stabilize p70S6K and p90rsk. In addition to S6, phosvitin was also a substrate, whereas myelin basic protein, casein, protamine, and histones were poorly phosphorylated if at all by the purified S6 kinase. The purified enzyme was inactivated upon incubation with serine/threonine-specific protein phosphatase 2A, which indicated that it may be an intermediary component in a cascade of insulin-activated protein kinases.

Distribution of MAP kinase, S6 kinase, and casein kinase II in rat tissues: activation by insulin in spleen

We examined the distribution of mitogen-activated protein (MAP) kinase, S6 kinase, and casein kinase II (CK-II) in the muscle, spleen, brain, and testes of Wistar rats. It was observed that spleen extracts contained the highest activity of all the kinases. Anion-exchange chromatography of spleen extracts by a MonoQ column resolved a single peak of myelin basic protein phosphotransferase activity that eluted after the usual position of the previously described p42 and p44 MAP kinases. Immunoblotting of the peak fractions with anti-MAP kinase antibody did not detect any immunoreactive bands that coincided with the activity peak, suggesting that the activity may represent a potentially novel MAP kinase. The MonoQ fractionation also resolved a single peak of phosvitin phosphotransferase activity which coincided with the intensity of two immunoreactive bands of 39 and 43 kilodaltons that were detected with antibodies against CK-II. The chromatographic behaviour and immunoblotting data indicate that the phosvitin kinase peak represented CK-II and suggested that the rat spleen CK-II had a molecular structure of alpha alpha ' beta 2. Furthermore, using an intact rat model, we showed that the potentially novel spleen MAP kinase and CK-II were markedly activated following intravenous injection of insulin. The significance of these findings remains to be determined.

Characterization of insulin-stimulated seryl/threonyl protein kinases in rat skeletal muscle

Post-insulin receptor signal transduction is mediated by a cascade of seryl/threonyl protein kinases which includes a family of mitogen-activated protein (MAP) kinases, ribosomal protein S6 kinases, and casein kinase-2. Previous studies have characterized these kinases primarily in cultured or isolated cells. We have demonstrated that intravenous injection of insulin into fasted rats significantly stimulated the activities of MAP kinases and S6 kinases in skeletal muscle, independently of the blood glucose levels in these animals. Anion exchange chromatography on Mono Q afforded the resolution of at least five peaks of insulin-stimulated myelin basic protein kinase activity. By immunological criteria, these myelin basic protein kinases included the p42mapk and p44erk1 as well as other potentially novel 44-kDa MAP kinases. Insulin-activated ribosomal S6 kinases were resolved into two major peaks by Mono Q chromatography, the latter of which contained a 100-kDa isoform of p90rsk as revealed by immunoblotting with an anti-rsk-peptide antibody. A 32-kDa S6 kinase in the earlier peak may represent a novel protein kinase in this tissue. Skeletal muscle casein kinase-2 was not significantly stimulated following insulin injection into rats under our experimental conditions. These results indicate that the intact rat can serve as a useful model system to investigate the mechanisms of insulin signal transduction.

Alterations of G protein function in cardiac tissues from streptozotocin-induced chronic diabetic rats

1. This study was performed to investigate G protein function in cardiac tissues from chronic diabetic rats by using pertussis toxin (PTX) and cholera toxin (CTX) as probes for G(i) and Gs proteins, respectively. 2. In the 10-week control group, i.v. injection of PTX significantly elevated the basal heart rate without having any effect on the chronotropic response of right atria to increasing concentrations of isoproterenol (ISO). In the 10-week diabetic rats, PTX treatment had no effect on the basal heart rate or on the response of right atria to ISO. In the 6-month groups, PTX did not exert any effects on basal or ISO-stimulated heart rate in either control or diabetic rat. 3. The inhibitory effect of carbachol (CCH) on cardiac tension in ISO-stimulated left atria was completely abolished by i.v. injection of PTX in the 10-week groups (both control and diabetic rats). The same treatment, however, only slightly reduced the effect of CCH on left atria contraction in rats from 6-month groups. 4. In both control and diabetic rats in the 10-week groups, incubation with CTX caused a significant increase in heart rate in right atria, and in developed cardiac tension in left atria preparations. The magnitude of the increase was the same in both control and diabetic rats. 5. Studies carried out using ADP-ribosylation technique indicated that the amount of G(i) protein was not changed in the ventricular muscle of the 10-week diabetic rat. Labelling of Gs protein could not be detected in either control or diabetic rat heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of correlation between activation of cyclic AMP-dependent protein kinase and inhibition of contraction of rat vas deferens by cyclic AMP analogs

The effects of N6,O2-dibutyrl-adenosine-3',5'-cyclic monophosphate (db-cAMP) and 8-bromo-adenosine-3',5'-cyclic monophosphate (8-Br-cAMP) on tension and cAMP-dependent protein kinase (PKA) activities in rat vas deferens were investigated. A soluble enzyme fraction obtained from the vas deferens was found to contain both type I and type II isozymes of PKA, whereas a particulate fraction contained only the type II isozyme. Exposure of the vas deferens to db-cAMP (1-100 microM) for 30 min caused a concentration-dependent inhibition of phenylephrine-induced contractions, with an EC50 of less than 10 microM. 8-Br-cAMP had no significant effect on contractions over a similar concentration range. Both of the analogs were able to activate PKA significantly at a concentration of 10 microM, and the magnitude of the PKA activation was greater with 8-Br-cAMP than with db-cAMP. Charcoal was added to the homogenization buffer in these experiments to prevent the artifactual activation of PKA by cAMP analogs trapped in the extracellular space. The ability of db-cAMP, but not 8-Br-cAMP, to inhibit the contraction of vas deferens could not be explained on the basis of differential activation of soluble or particulate PKA or of specific isozymes of the enzyme. It is, therefore, concluded that activation of PKA is not responsible for the relaxant effects of cAMP analogs in some smooth muscle.