Pre-treatment levels of circulating free IGF-1 identify NSCLC patients who derive clinical benefit from figitumumab

BACKGROUND

Phase III trials of the anti-insulin-like growth factor type 1 receptor (IGF-IR) antibody figitumumab (F) in unselected non-small-cell lung cancer (NSCLC) patients were recently discontinued owing to futility. Here, we investigated a role of free IGF-1 (fIGF-1) as a potential predictive biomarker of clinical benefit from F treatment.

MATERIALS AND METHOD

Pre-treatment circulating levels of fIGF-1 were tested in 110 advanced NSCLC patients enrolled in a phase II study of paclitaxel and carboplatin given alone (PC) or in combination with F at doses of 10 or 20 mg kg(-1) (PCF10, PCF20).

RESULTS

Cox proportional hazards model interactions were between 2.5 and 3.5 for fIGF-1 criteria in the 0.5-0.9 ng ml(-1) range. Patients above each criterion had a substantial improvement in progression-free survival on PCF20 related to PC alone. Free IGF-1 correlated inversely with IGF binding protein 1 (IGFBP-1, ρ=-0.295, P=0.005), and the pre-treatment ratio of insulin to IGFBP-1 was also predictive of F clinical benefit. In addition, fIGF-1 levels correlated with tumour vimentin expression (ρ=0.594, P=0.021) and inversely with E-cadherin (ρ=-0.389, P=0.152), suggesting a role for fIGF-1 in tumour de-differentiation.

CONCLUSION

Free IGF-1 may contribute to the identification of a subset of NSCLC patients who benefit from F therapy.

Molecular bases for sensitivity to figitumumab (CP-751,871) in NSCLC

8091

Background: Signaling of Insulin like Growth Factors (IGFs) through the IGF type 1 receptor (IGF-IR) induces tumor resistance to cancer therapy. Bioavailability of IGFs is regulated by IGF-binding proteins (IGFBP), of which IGFBP3 is the most abundant. Figitumumab (F) (CP-751,871), a specific IGF-IR inhibitor, has shown phase 2 activity in NSCLC in some histologies (i.e., squamous cell and adenocarcinoma) but not others (i.e, large cell or NOS tumors). Methods: Protein expression of members of the IGF-IR pathway, EGFR and differentiation markers was determined in core biopsies from 230 NSCLC pts, including 52 pts enrolled in F trials. Plasma concentration of IGF-1 and related proteins was determined in 159 NSCLC pts in F trials. Gene expression profiling was conducted in 35 NSCLC cell lines treated with F. Results: Squamous NSCLC had the highest IGF-IR expression (p=0.057). An association with better outcome was seen for E-cadherin expression (HR =0.62, 0.46–0.82 95% CI, p=0.005) and clustering by E-cadherin levels revealed a strong correlation between IGF-IR and EGFR expression in the high E-cadherin group (p<0.001). This subset included 73% of the squamous cell tumors investigated (N=44). Plasma levels of free IGF-1 (fIGF-1) were low and not predictive of response in squamous cell. In contrast, pts with adenocarcinoma had high plasma fIGF-1 levels (p=0.06) that correlated with vimentin expression (Rho=0.732, p=0.06), and both fIGF-1 and vimentin were predictive of F clinical benefit (p=0.03). Large cell/NOS NSCLC expressed the highest levels of vimentin (p<0.001) but had low E-cadherin and IGF-IR expression and low fIGF-1 plasma levels. Analysis of anchorage independent growth in NSCLC cell lines confirmed that F activity is independently associated to IGF-IR overexpression (p=0.02) and IGFBP3 under-expression (p=0.009). Conclusions: IGF-IR overexpression and increased free IGFs/low IGFBP are key independent mechanisms of sensitivity to F in NSCLC of squamous and adenocarcinoma cell histologies.

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Continued high activity of figitumumab (CP-751,871) combination therapy in squamous lung cancer

8072

Background: Figitumumab (CP-751,871) is a fully human, IgG2monoclonal antibody against the insulin-like growth factor type I receptor (IGF-IR). We reported in a randomized phase II study (ASCO 2008), preliminary evidence of high activity of the combination of paclitaxel (T), carboplatin (C) and figitumumab (F) in advanced treatment-naïve NSCLC of squamous cell histology (n=11 pts). A single arm trial extension cohort was conducted to confirm those findings. Methods: Fifty-six pts with non-adenocarcinoma NSCLC were enrolled. Pts received T (200 mg/m2), C (AUC of 6) and F (20 mg/kg) q3weeks for up to 6 cycles; pts with response (PR) or stable disease were eligible to continue F as single agent until disease progression. Statistical hypotheses were 30% (null) versus 50% (response of interest). Protein expression of the IGF-IR in core tumor biopsies was quantified using automated quantitative analysis (AQUA) technology. Results: Pts were 72% male, 28% >70 years old and 91% stage IV. Median number of treatment cycles was 4, with 46% of pts receiving single agent F beyond cycle 4. TCF was well tolerated. The most common all-causality grade 3, 4 CTCAE adverse events were neutropenia (21%), hyperglycemia (14%) and fatigue (14%). Hyperglycemia adverse events almost always occurred within the first treatment cycle and were manageable with standard measures. Responses in squamous pts are currently 25 out of 40 pts according to RECIST, with final response assessment still pending for 7 additional pts (≥53%, p<0.001). One complete response and 7 striking PRs (50–80% tumor size reduction at cycle 2) were observed. Tumor size reductions with F maintenance treatment were also seen in 2 pts. Median progression free survival has not been yet reached at 4 months follow up. A trend (p=0.1) for higher IGF-IR expression in patients responding to TCF was observed in a small data set (n=12). Median tumor IGF-IR expression in pts responding to TCF therapy and non-responders were respectively 6287 and 4131 AQUA scores. Analysis of IGF-IR and other members of the IGF-IR pathway continues. Conclusions: These data further support the activity of figitumumab combination therapy in pts with squamous NSCLC.

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Correlation of plasma levels of free insulin-like growth factor 1 and clinical benefit of the IGF-IR inhibitor figitumumab (CP- 751, 871)

3539

Background: Free IGF-1 (fIGF-1) represents the biologically active fraction of IGF-1, the main circulating ligand of the Insulin-like Growth Factor type I Receptor (IGF-IR). Signaling through the IGF-IR induces tumor survival and resistance to cancer therapy. Figitumumab (F) (CP-751,871) inhibits IGF-1-induced IGF-IR autophosphorylation with an IC50 of 0.42 nmol/L. Methods: Plasma levels of fIGF-1 were measured in a phase 1b/2 multi-center study of Paclitaxel (T) and Carboplatin (C) and F in patients (pts) with treatment-naïve NSCLC. Other serum markers of the IGF-IR pathway, including circulating soluble IGF-IR (sIGF-IR), IGFBP3 and ALS (acid-labile subunit), were also investigated. The Kaplan-Meier method was used to estimate median survival times. Results: A total of 536 blood samples from 159 pts were analyzed. Baseline median and range fIGF-1 were 0.53 and 0.07–1.99 ng/mL. fIGF-1 directly correlated with IGFBP3 and ALS, and inversely with sIGF-IR (Rho=-0.430, p=0.03). Treatment with F resulted in dose-dependent accumulation of fIGF-1 with a sustained >10 fold increase in fIGF-1 plasma levels at the 20 mg/kg dose, suggesting complete systemic blockade of fIGF-1 binding to the IGF-IR. sIGF-IR decreased and IGFBP3 increased in response to F, but increases in IGBP3 were more modest than those of fIGF-1. Baseline plasma levels of fIGF-1 had a 96.6% negative predictive value for PFS status at 6 months (p=0.03). Median PFS were respectively 2.73 and 6.53 months for TC alone and TC with F (20 mg/kg) in the high fIGF-1 group (p=0.001) while no significant treatment effect of F was observed in the low (<0.54 ng/mL) fIGF-1 group. Sixty three percent of pts with high fIGF-1 had tumors of adenocarcinoma histology. Conclusions: IGF-1 is a key element in the biology of NSCLC of adenocarcinoma histology and its determination may contribute to the identification of pts who benefit from figitumumab therapy.

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Safety of the anti-IGF-1R antibody CP-751,871 in combination with exemestane in patients with advanced breast cancer

Abstract #2136

Background: Aromatase inhibitors (AIs) are established first-line treatment for postmenopausal estrogen receptor (ER)+ metastatic breast cancer. However, not all patients benefit from AIs and those whose tumors initially respond eventually relapse. One hypothesized mechanism for tumor insensitivity to hormonal agents seems to be cross-talk between the ER pathway and other growth factor signaling pathways, in particular the insulin-like growth factor receptor type 1 (IGF-1R). In xenograft breast cancer models, CP-751,871 administration increased tumor growth inhibition induced by tamoxifen. Thus our trial addresses the effect of combining AI with an IGF-1R antagonist.&#x2028; Methods: A phase II, multicenter, randomized, two-arm, comparative, two-stage trial to determine PFS of CP-751,871, a fully human IgG2 monoclonal antibody targeting IGF-1R, in combination with exemestane versus exemestane alone as first-line treatment in patients with hormone receptor positive, advanced breast cancer. Secondary endpoints include clinical benefit (CR, PR, or SD ≥6 months), safety/tolerability and PK. Patients included in the study are post menopausal, ≥18 years with locally advanced/metastatic breast cancer (stage IIIB or IV), ECOG PS 0–2, and adequate hematological, biochemical, and cardiac functions. CP-751,871 is given by intravenous infusion at a dose of 20 mg/kg every 21 days while 25 mg exemestane was given p.o. daily.&#x2028; Results: To date 37 patients have been dosed with CP-751,871 plus exemestane. Median age is 60.5 years (range 34–84). Patients received a median of 9.5 treatment cycles (range 1–22). One GR 4 CP-751,871-related AE (hoarse voice) was reported, which resolved after 3 days without intervention. GR 3 CP-751,871-related toxicities included 8.1% hyperglycemia (n=3), 8.1% GGT elevation (n=3), 5.4% allergic reaction (n=2), 5.4% hearing loss (n=2), 5.4% weight loss (n=2), and 2.7% anorexia (n=1). GR 2 CP-751,871-related AEs &gt;10% were headaches, muscle cramps, and nail changes. Both hyperglycemia and hypersensitivity reactions were manageable (with oral hypoglycemic drug/insulin and antihistamine), while GGT elevation seems to be reversible.&#x2028; Conclusions: CP-751,871 in combination with exemestane is well tolerated. The most frequent GR 3 side effects are either well managed with medications or appear to be reversible. Therefore, CP-751,871, due to its safety profile, is a good targeted agent to combine with standard hormonal therapy. The stage I portion of the study to determine efficacy and toxicity is ongoing.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2136.

Circulating tumor cells expressing the insulin growth factor-1 receptor (IGF-1R): Method of detection, incidence and potential applications

3507

Purpose: To detect IGF-1R on circulating tumor cells (CTCs) as a biomarker in the clinical development of a monoclonal human antibody, CP-751,871, targeting IGF-1R. Experimental Design: An automated sample preparation and analysis system for enumerating CTCs (Celltracks) was adapted for detecting IGF-1R positive CTCs with a diagnostic antibody targeting a different IGF-1R epitope to CP-751,871. This assay was utilized in three phase I trials of CP-751,871 as a single agent or with chemotherapy and was validated using cell lines and blood samples from healthy volunteers and patients with metastatic carcinoma. Results: There was no interference between the analytical and therapeutic antibodies. CP-751,871 was well tolerated as a single agent, and in combination with docetaxel or carboplatin and paclitaxel, at doses ranging from 0.05 mg/kg to 20 mg/kg. Eighty patients were enrolled on phase 1 studies of CP-751,871, with 47 (59%) patients having CTCs detected during the study. Prior to treatment 26 patients (33%) had CTCs, with 23 having detectable IGF-1R positive CTCs. CP-751,871 alone, and CP-751,871 with cytotoxic chemotherapy, decreased CTCs and IGF-1R positive CTCs; these increased towards the end of the 21-day cycle in some patients, falling again with retreatment. CTCs were commonest in advanced hormone refractory prostate cancer (11/20). Detectable IGF-1R expression on CTCs before treatment with CP-751,871 and docetaxel was associated with a higher frequency of PSA decline by more than 50% (6/10 vs 2/8 patients). A relationship was observed between sustained falls in CTCs counts and PSA declines by more than 50%. Conclusions: IGF-1R expression is detectable by immunofluorescence on CTCs. These data support the further evaluation of CTCs in pharmacodynamic studies and patient selection, particularly in advanced prostate cancer.

No significant financial relationships to disclose.

Pharmacodynamic properties of the anti-IGF-IR monoclonal antibody CP-751,871 in cancer patients

3587

Background: The Insulin like Growth Factor I receptor (IGF-IR), a tyrosine kinase, is widely expressed in human tissues. IGF- IR and its ligands (IGF-I and IGF-II) are expressed by many human cancers (e.g., breast, prostate, colorectal and non-small cell lung). Binding of the ligands to the IGF-IR activates key cellular signaling pathways important for stimulating cellular proliferation and inhibiting apoptosis. IGF- I and IGF-II are present in the circulation, but also locally expressed in neoplastic tissue. Bioavailability of these ligands is regulated by a family of IGF binding proteins (IGFBPs1–6). CP-751,871, a fully human monoclonal antibody, is a highly specific and potent inhibitor of IGF-IR activation. In vitro experiments show that binding of CP 751,871 to IGF-IR induces receptor internalization and degradation. This antibody has been shown to have antineoplastic activity using both in vivo and in vitro pre-clinical models. Methods: Blood samples were collected for characterization of the pharmacokinetic and pharmacodynamic properties of CP-751,871 in phase 1 trials of this agent given to cancer patients either alone or in combination with chemotherapy. The endpoints assessed included among others: CP-751,871 plasma concentrations, total and free IGF-I, IGFBP-3, soluble IGF-IR and IGF-IR expression on granulocytes and tumor cells. Results: CP 751,871 exposure increased with dose over the 800-fold dose range investigated. Pharmacokinetic profiles were consistent with target-mediated disposition. A dose-dependent downregulation of soluble IGF-IR serum concentration and IGF-IR expression was observed, with sustained inhibition for the entire dosing period (3–4 week cycles) observed at doses ≥ 1.5 mg/kg. As predicted for an agent that interferes with IGF-I action, IGF-I and IGFBP-3 serum levels were up-regulated in a similar dose-dependent manner. Conclusions: The pharmacodynamic endpoints of clinical trials provide evidence that CP-751,871 targets IGF-IR in granulocytes, tumor cells and tissues involved in regulation of the growth hormone -IGF-I axis. These data provide proof of principle for the use of CP-751,871 as a first-in-class therapeutic approach to inhibit the IGF-IR pathway in cancer patients.

No significant financial relationships to disclose.

Phase I dose escalation study of the anti-IGF-1R monoclonal antibody CP-751,871 in patients with refractory solid tumors

3586

Background: The insulin-like growth factor 1 receptor (IGF-IR), a tyrosine kinase, and its ligands (IGF-I & -2) are upregulated in many human tumors (e.g., breast, prostate, colon and non-small cell lung cancer) and enhance proliferative and prosurvival signaling. Inhibition of IGF-IR activation in tumor models suppresses tumor growth and increases tumor sensitivity to chemotherapy, supporting the development of agents targeting IGF-IR. CP-751,871 is a potent, highly specific, fully humanized, monoclonal antibody that inhibits IGF-IR autophosphorylation and induces receptor internalization. Methods: A Phase I dose escalation study was initiated to define the safety and tolerability, and to characterize the pharmacokinetic properties of CP-751,871 in patients with advanced solid tumors refractory to standard therapies. Results: Following informed consent and screening, a total of 24 patients with refractory solid tumors (e.g. colorectal, NSCLC, sarcoma and prostate cancer; 1–6 previous regimens) were enrolled. Patients received 3 to 20 mg/kg of CP-751,871 by IV infusion on Day 1 of 3-week cycles in four dose-escalation cohorts of 3 patients. No dose limiting toxicities were identified and the maximum feasible dose (MFD) cohort of 20 mg/kg was extended with 12 additional patients. No higher than grade 3 CTCAE v3.0 toxicities, attributed to study drug, have been so far reported. Grade 3 toxicities, all reported in patients dosed with 20 mg/kg of CP-751,871, are increased GGT (4%) and fatigue (4%). Grade 2 toxicities include: anorexia (7%), diarrhea (7%), increased GGT (4%), hyperglycemia (4%), fatigue (4%), increased urinary frequency (4%), nausea (4%), increased ALT (4%) and increased AST (4%). Pharmacokinetic analysis is currently ongoing. No objective responses were observed. At the MFD, patients received a median of 4 cycles (1–16). Three patients were stable for > 6 months and one patient, currently at cycle 16, remains on study. An additional cohort of 12 adrenocortical cancer patients is under evaluation. Conclusions: These data indicate that CP-751,871 is safe and well tolerated. Due to its good safety profile, CP-751,871 may constitute a suitable targeted agent to use in combination with approved therapies in multiple tumor types.

No significant financial relationships to disclose.

Efficacy of the anti-insulin like growth factor I receptor (IGF-IR) antibody CP-751871 in combination with paclitaxel and carboplatin as first-line treatment for advanced non-small cell lung cancer (NSCLC)

7506

Background: CP-751871 is a fully human, IgG2 monoclonal antibody against the IGF-IR active in preclinical models of NSCLC. Methods: We are conducting a phase II, randomized, non-comparative study in ten centers to evaluate the safety and efficacy of combination paclitaxel (T), carboplatin (C) and CP-751871 (I) versus TC alone in stage IIIB, IV or recurrent, treatment-naive NSCLC pts with performance status 0–1. The statistical hypotheses are 28% (null) versus 40% (response of interest). Pts are randomized (2:1) to T (200 mg/m2), C (AUC of 6) and I (10 mg/kg), or TC alone every 3 weeks for up to 6 cycles; pts receiving TCI with response (PR) or stable disease following discontinuation of chemotherapy are eligible to continue I as single agent until disease progression. Pts progressing on TC alone are eligible to receive I as single agent or in combination with TC at the judgment of the investigator. Responses are assessed by investigator using RECIST. Results: An interim analysis for futility has been conducted with 73 pts enrolled: 48 treated with TCI; 25 with TC. TCI was well tolerated. All causality grade 3,4 toxicity included (TCI, TC): hyperglycemia (20%, 10%), fatigue (15%, 8%), neutropenia (13%, 20%) and neuropathy (10%, 4%). 22/48 pts receiving TCI (46%) and 8/32 pts on TC (32%) had objective responses. Furthermore, 14 out of 27 TCI pts (52%) with non-adenocarcinoma responded to treatment. In addition, a PR was observed in 1 out of 4 TC pts who elected to receive single agent I after progression on TC alone. Conclusions: CP-751871 appears safe in combination with TC. Interim TCI activity warranted further investigation. An additional 83 pts will be enrolled to assess further the safety and efficacy of this combination treatment.

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Phase I trial involving the pharmacodynamic (PD) study of circulating tumour cells, of CP-751,871 (C), a monoclonal antibody against the insulin-like growth factor 1 receptor (IGF-1R), with docetaxel (D) in patients (p) with advanced cancer

3023

Background: C is the first specific, fully human, monoclonal antibody to target IGF-1R in clinical trials. It potently inhibits IGF-1R signaling, enhancing D antitumour activity. This trial investigated the safety, feasibility, dose limiting toxicity (DLT), PK and antitumor activity of D administered with C every 3 weeks. PD studies evaluated circulating tumor cell (CTC) IGF-1R expression and CTC counts pre- and post-treatment. Methods: The C doses tested were 0.1, 0.4, 0.8, 1.5, 3.0, 6.0 and 10 mg/kg in sequential cohorts of 3–6 p. D was fixed at 75mg/m2. P achieving disease control continued on C alone if experiencing D toxicity. Results: 21 p (20 male) have received 100 courses of C with D. 7 p received 8 or more courses of the combination. A further 21 courses of C alone have been administered. No toxicity has been attributed to C to date with the observed toxicities being attributable to D. Grade 3/4 toxicities were neutropenia (16/21 p) and neutropenic fever in 2/21 p. Grade 3 diarrhea was reported in 3 p, but this was easily controlled with antidiarrheals. Transient grade 1 hyperglycaemia was noted largely on day 1, following steroid premedication (14 p), but no significant C related hyperglycemia has been observed. An MTD has not been reached. Serial echocardiograms demonstrated no cardiac toxicity. Of 18 castration resistant prostate cancer (CRPC) p treated, 4 have had a confirmed PR, with 2 unconfirmed PR and 2 having disease stabilization for > 6 months (median number of courses: 10; range: 3–12). 5 p have maintained SD with C alone for 2–7 courses. CTC were detected in 16 of 18 p (CTC numbers ranged from 1 to 202 in 7.5ml of blood). IGF-1R expression was detected in 12 p. CTC IGF-1R was undetectable following treatment with C at doses above 3 mg/kg. Conclusions: This combination is safe and feasible with no toxicity attributed to C and encouraging antitumor activity in CRPC.

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Phase 1 first-in-human dose escalation study of cp-751,871, a specific monoclonal antibody against the insulin like growth factor 1 receptor

7609

Background: Multiple lines of evidence indicate that the Insulin Like Growth Factor 1 Receptor (IGF-1R) plays a key role in the progression of multiple myeloma (MM). IGF-1 is a growth factor for MM cells. It promotes survival to the cytotoxic effects of chemotherapy in animal models of MM and its blood levels has been shown to correlate with those of paraprotein in MM patients. CP-751,871, a fully human monoclonal antibody, is a highly specific and potent inhibitor of the autophosphorylation of IGF-1R. Methods: Based on its mechanism of action and the potential relevance of IGF-1R in MM, a Phase 1 First-in-Human dose escalation study was initiated with the objective to define the safety and tolerability, and to characterize the pharmacokinetic and pharmacodynamic properties of CP-751,871 in this patient population. Patient’s eligibility included previously treated multiple myeloma in relapse or refractory phase and/or less than complete remission following autologous stem cell transplant or tandem transplant. Results: Following informed consent and screening, 10 dose-escalation cohorts of patients received from 0.025 to 10 mg/kg of CP-751,871 by iv infusion on Day 1 of 4-week cycles. In patients with a suboptimal response to CP-751,871 alone, oral dexamethasone was added to the treatment regimen. Patients received up to 14 cycles of CP-751,871 therapy, alone or in combination with dexamethasone. No dose limiting toxicities have been identified to date. Plasma CP-751,871 exposure increases with dose, and the pharmacokinetic characteristics are consistent with target-mediated disposition. Pharmacodynamic measurements indicate complete target saturation by CP-751,871 for the complete length of the dosing period. One near CR and 2 PR in combination with dexamethasone have been reported. Conclusions: These data indicate that CP-751,871 is well tolerated and may constitute a therapeutic approach for patients with multiple myeloma.

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Antigen-specific T cell responses in patients with melanoma treated with the CTLA4 blocking mAb ticilimumab

8033

Background: We previously defined the magnitude of the minimum statistically significant change in value for the MHC tetramer and ELISPOT assays (Comin-Anduix, Clin Cancer Res 2006). We used those reference change values (RCV) to determine if the administration of ticilimumab to patients with melanoma expands the circulating populations of tumor antigen-specific T cells. Methods: HLA-A2.1+ pts with sIIIc or IV melanoma and baseline circulating MART-1-specific T cells above the low limit of detection by tetramer assay (LLD, 0.03% of CD8+ T cells) received ticilimumab at 10 mg/kg monthly. Two 40 ml blood samples were collected at baseline, and one at 1 and 2 weeks after each dose for 4 cycles. Primary endpoint was immune response for MART-1 by tetramer assay, for which the RCV is 80% (expressed as percent change from baseline). Results: Of 15 pts (2 sIIIc, 5 sIVa, 2 sIVb, 6 sIVc), 1 was not treated and 2 received only 1 dose due to rapid progression. The 12 remaining pts received 2–11 doses. Clinical immunologic response to ticilimumab was evidenced by immune-related toxicity (G3 diarrhea in 2 pts, G2 hypophysitis in 1 pt, G3 hepatitis in 2 pts) and by anti-tumor activity: CR in 1 pt (15+ mo), PR in 2 pts (9+, 8 mo), and SD in 3 pts (11, 8+ and 4 mo); the rest had PD at 4 mo or less. A mean of 2 baseline and 7 follow up (range 5–9) time points were tested by tetramer and ELISPOT assays. 4 pts had an increase in MART-1-specific T cells beyond the RCV on 1 or more occasions, but no pt had a consistent pattern of change over time. Indeed, there was no consistent pattern of change in any pt in circulating T cells specific for MART-1, gp100, tyrosinase, EBV, or CMV by tetramer or by ELISPOT assay. One pt had accessible regressing lesions which on biopsy showed heavy infiltration by CD8+/Granzyme B+ CTL and a 10-fold enrichment of gp100-specific T cells compared to his peripheral blood. Conclusion: Ticilimumab administered monthly induces immune-related phenomena and tumor responses in patients with melanoma without a demonstrable expansion of circulating melanoma antigen-specific T cells. Evaluation of melanoma antigen-specific T cells within the tumor may be a better way to study the mechanism of antitumor activity of CTLA4 blocking mAb.

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Macrophage inducible nitric oxide synthase gene expression is blocked by a benzothiophene derivative with anti-HIV properties

Nitric oxide (NO) has been shown to mediate multiple physiological and toxicological functions. The inducible nitric oxide synthase (iNOS) is responsible for the high output generation of NO by macrophages following their stimulation by cytokines or bacterial antigens. The inhibition of TNF alpha-stimulated HIV expression and the anti-inflammatory property of PD144795, a new benzothiophene derivative, have been recently described. We have now analyzed whether some of these properties could be mediated by an effect of PD144795 on NO-dependent inflammatory events. We show that PD144795 suppresses the lipopolysaccharide-elicited production of nitrite (NO(-)(2)) by primary peritoneal mouse macrophages and by a macrophage-derived cell line, RAW 264.7. This effect was dependent on the dose and timing of addition of PD144795 to the cells. Suppression of NO(-)(2) production was associated with a decrease in the amount of iNOS protein, iNOS enzyme activity and mRNA expression. The effect of PD144795 was partially abolished by coincubation of the cells with LPS and IFN gamma. However, the inhibitory effect of PD144795 was not abrogated by the simultaneous addition of LPS and TNF alpha, which indirectly suggests that the effect of PD144795 was not due to the inhibition of TNF alpha synthesis. Additionally, PD144795 did not block NF-kappa B nuclear translocation induced by LPS. Inhibition of iNOS gene expression represents a novel mechanism of PD144795 action that underlines the anti-inflammatory effects of this immunosuppressive drug.

Cks1 mediates vascular smooth muscle cell polyploidization

Vascular smooth muscle cells (VSMC) at capacitance arteries of hypertensive individuals and animals undergo dramatic polyploidization that contributes toward their hypertrophic phenotype. We report here the identification of a defective mitotic spindle cell cycle checkpoint in VSMC isolated from capacitance arteries of pre-hypertensive rats. These cells demonstrated a high predisposition to polyploidization in culture and failed to maintain cyclin B protein levels in response to colcemid, a mitotic inhibitor. Furthermore, this altered mitotic spindle checkpoint status was associated with the overexpression of Cks1, a Cdc2 adapter protein that promotes cyclin B degradation. Cks1 up-regulation, cyclin B down-regulation, and VSMC polyploidization were evidenced at the smooth muscle of capacitance arteries of genetically hypertensive and Goldblatt-operated rats. In addition, angiotensin II infusion dramatically increased Cks1 protein levels at capacitance arteries of normotensive rats, and angiotensin II treatment of isolated VSMC abrogated their ability to down-regulate Cks1 and maintain cyclin B protein expression in response to colcemid. Finally, transduction of VSMC from normotensive animals with a retrovirus that drives the expression of Cks1 was sufficient to alter their mitotic spindle cell cycle checkpoint status and promote unscheduled cyclin B metabolism, cell cycle re-entry, and polyploidization. These data demonstrate that Cks1 regulates cyclin B metabolism and ploidy in VSMC and may contribute to the understanding of the phenomena of VSMC polyploidization during hypertension.

Akt1/PKB upregulation leads to vascular smooth muscle cell hypertrophy and polyploidization

Vascular smooth muscle cells (VSMCs) at capacitance arteries of hypertensive individuals and animals undergo marked age- and blood pressure-dependent polyploidization and hypertrophy. We show here that VSMCs at capacitance arteries of rat models of hypertension display high levels of Akt1/PKB protein and activity. Gene transfer of Akt1 to VSMCs isolated from a normotensive rat strain was sufficient to abrogate the activity of the mitotic spindle cell-cycle checkpoint, promoting polyploidization and hypertrophy. Furthermore, the hypertrophic agent angiotensin II induced VSMC polyploidization in an Akt1-dependent manner. These results demonstrate that Akt1 regulates ploidy levels in VSMCs and contributes to vascular smooth muscle polyploidization and hypertrophy during hypertension.

Calcineurin is activated in rat hearts with physiological left ventricular hypertrophy induced by voluntary exercise training

BACKGROUND

Calcineurin may play a pivotal role in the signaling of cardiac hypertrophy; since this hypothesis was first put forward, controversial reports have been published using various experimental models. This study was designed to compare the physiological left ventricular hypertrophy (LVH) induced by voluntary exercise with LVH induced by aortic constriction and to determine whether calcineurin participates in the signaling of exercise-induced LVH.

METHODS AND RESULTS

Wistar rats were assigned to 1 of the following 5 groups: 10 weeks of voluntary exercise (EX), a sedentary regimen, a 1-week (AC1) or 4-week (AC4) ascending aortic constriction period, or a sham operation. EX rats ran 2.4+/-0.7 km/day voluntarily in specially manufactured cages; this was associated with an increase of LV diastolic dimension and stroke volume. Myocardial calcineurin activity markedly increased in EX rats (46.4+/-8.3 versus 18.4+/-0.5 pmol. min(-1). mg(-1) in sedentary rats; P<0.001) and in AC1 rats (44.9+/-6.7 versus 22.1+/-3.7 pmol. min(-1). mg(-1) in sham-operated rats; P<0.001), but not in AC4 rats (29.0+/-3.4 pmol. min(-1). mg(-1)). Treatment with cyclosporin A completely inhibited the development of LVH in EX rats, but it only partially attenuated the development of LVH in AC4 rats.

CONCLUSIONS

Calcineurin was activated in exercise-induced physiological LVH and in the developing phase of LVH (AC1), but not in decompensated pressure-overload hypertrophy (AC4). Cyclosporin therapy for the prevention of LVH may be harmful because it does not block the development of pathological hypertrophy but rather that of favorable adaptive hypertrophy.

Gain of function properties of mutant p53 proteins at the mitotic spindle cell cycle checkpoint

Mutations in the p53 tumor suppressor gene locus predispose human cells to chromosomal instability. This is due in part to interference of mutant p53 proteins with the activity of the mitotic spindle and postmitotic cell cycle checkpoints. Recent data demonstrates that wild type p53 is required for postmitotic checkpoint activity, but plays no role at the mitotic spindle checkpoint. Likewise, structural dominant p53 mutants demonstrate gain-of-function properties at the mitotic spindle checkpoint and dominant negative properties at the postmitotic checkpoint. At mitosis, mutant p53 proteins interfere with the control of the metaphase-to-anaphase progression by up-regulating the expression of CKs1, a protein that mediates activatory phosphorylation of the anaphase promoting complex (APC) by Cdc2. Cells that carry mutant p53 proteins overexpress CKs1 and are unable to sustain APC inactivation and mitotic arrest. Thus, mutant p53 gain-of-function at mitosis constitutes a key component to the origin of chromosomal instability in mutant p53 cells.

The control of mitosis

A precise coordination of multiple cell cycle events is required to ensure proper mitosis. Chromosome cohesion must be maintained until all chromosomes are attached to opposite poles of the mitotic spindle and aligned at the metaphase plate. At the onset of anaphase, the activity of separins contributes to the release of cohesins from chromosomes, allowing for the segregation of bivalents to opposite spindle poles. Separin activity is blocked by binding to a class of proteins known as securins, whose turnover at the metaphase-to-anaphase transition is triggered by the Anaphase Promoting Complex or cyclosome. The mitotic spindle cell cycle checkpoint coordinates the timing of these events and acts as input mechanism for DNA damage/stress pathways. Failure of this precise network leads to genomic instability and/or cell death.

p53 is a transcriptional activator of the muscle-specific phosphoglycerate mutase gene and contributes in vivo to the control of its cardiac expression

The role that the p53 tumor suppressor gene product plays in cellular differentiation remains controversial. However, recent evidence indicates that p53 is required for proper embryogenesis. We have studied the effect of p53 on the expression mediated by the promoter of the rat muscle-specific phosphoglycerate mutase gene (M-PGAM), a marker for cardiac and skeletal muscle differentiation. Experiments involving transient transfection, mobility shift assay, and site-directed mutagenesis demonstrated that p53 specifically binds and transactivates the M-PGAM promoter. The p53-related proteins p51A and p73L also transactivated M-PGAM. Moreover, stable expression of a p53 dominant mutant in C2C12 cells blocked the induction of M-PGAM expression during the myoblast to myotube transition and the ability of p53, p51A, and p73L to transactivate the M-PGAM promoter. In addition, impaired expression of M-PGAM was observed in a subset of p53-null animals in heart and muscle tissues of anterior-ventral location. These results demonstrate that p53 is a transcriptional activator of M-PGAM that contributes in vivo to the control of its cardiac expression. These data support previous findings indicating a role for p53 in cellular differentiation.

Ectopic expression of cdc2/cdc28 kinase subunit Homo sapiens 1 uncouples cyclin B metabolism from the mitotic spindle cell cycle checkpoint

Primary human fibroblasts arrest growth in response to the inhibition of mitosis by mitotic spindle-depolymerizing drugs. We show that the mechanism of mitotic arrest is transient and implicates a decrease in the expression of cdc2/cdc28 kinase subunit Homo sapiens 1 (CKsHs1) and a delay in the metabolism of cyclin B. Primary human fibroblasts infected with a retroviral vector that drives the expression of a mutant p53 protein failed to downregulate CKsHs1 expression, degraded cyclin B despite the absence of chromosomal segregation, and underwent DNA endoreduplication. In addition, ectopic expression of CKsHs1 interfered with the control of cyclin B metabolism by the mitotic spindle cell cycle checkpoint and resulted in a higher tendency to undergo DNA endoreduplication. These results demonstrate that an altered regulation of CKsHs1 and cyclin B in cells that carry mutant p53 undermines the mitotic spindle cell cycle checkpoint and facilitates the development of aneuploidy. These data may contribute to the understanding of the origin of heteroploidy in mutant p53 cells.

Prevention of cardiac hypertrophy in mice by calcineurin inhibition

Hypertrophic cardiomyopathy (HCM) is an inherited form of heart disease that affects 1 in 500 individuals. Here it is shown that calcineurin, a calcium-regulated phosphatase, plays a critical role in the pathogenesis of HCM. Administration of the calcineurin inhibitors cyclosporin and FK506 prevented disease in mice that were genetically predisposed to develop HCM as a result of aberrant expression of tropomodulin, myosin light chain-2, or fetal beta-tropomyosin in the heart. Cyclosporin had a similar effect in a rat model of pressure-overload hypertrophy. These results suggest that calcineurin inhibitors merit investigation as potential therapeutics for certain forms of human heart disease.

An oncogenic form of p53 confers a dominant, gain-of-function phenotype that disrupts spindle checkpoint control

Although it is well-established that p53 functions as a tumor suppressor gene, certain mutations exhibit gain-of-function activities that increase oncogenic transformation. We have found a common class of p53 missense mutation that exhibits a dominant, gain-of-function activity that generates genomic instability. Fibroblasts from Li-Fraumeni syndrome heterozygotes with such mutations generate polyploid cells when exposed to spindle depolymerizing agents. Expression of such mutant alleles in normal fibroblasts yields the same phenotype. This class of dominant, gain-of-function p53 mutation (p53(RSC), relaxed spindle checkpoint allele) does not require the transcriptional activation function of p53 for this behavior. Thus p53 mutations can contribute to progression of a cancer cell not only by absence of p53 tumor suppressor activity but also by the presence of an activity that promotes genetic instability.