Lawrence C. Panasci

Metformin blocks the stimulative effect of a high-energy diet on colon carcinoma growth in vivo and is associated with reduced expression of fatty acid synthase

The molecular mechanisms responsible for the association of obesity with adverse colon cancer outcomes are poorly understood. We investigated the effects of a high-energy diet on growth of an in vivo colon cancer model. Seventeen days following the injection of 5x10(5) MC38 colon carcinoma cells, tumors from mice on the high-energy diet were approximately twice the volume of those of mice on the control diet. These findings were correlated with the observation that the high-energy diet led to elevated insulin levels, phosphorylated AKT, and increased expression of fatty acid synthase (FASN) by the tumor cells. Metformin, an antidiabetic drug, leads to the activation of AMPK and is currently under investigation for its antineoplastic activity. We observed that metformin blocked the effect of the high-energy diet on tumor growth, reduced insulin levels, and attenuated the effect of diet on phosphorylation of AKT and expression of FASN. Furthermore, the administration of metformin led to the activation of AMPK, the inhibitory phosphorylation of acetyl-CoA carboxylase, the upregulation of BNIP3 and increased apoptosis as estimated by poly (ADP-ribose) polymerase (PARP) cleavage. Prior work showed that activating mutations of PI3K are associated with increased AKT activation and adverse outcome in colon cancer; our results demonstrate that the aggressive tumor behavior associated with a high-energy diet has similar effects on this signaling pathway. Furthermore, metformin is demonstrated to reverse the effects of the high-energy diet, thus suggesting a potential role for this agent in the management of a metabolically defined subset of colon cancers.

Pegylated Liposomal Doxorubicin and Trastuzumab in HER-2 Overexpressing Metastatic Breast Cancer: A Multicenter Phase II Trial

PURPOSE Cardiotoxicity precludes the concurrent use of doxorubicin and trastuzumab. Because pegylated liposomal doxorubicin (PLD) has equal efficacy but significantly less cardiotoxicity than conventional doxorubicin, this phase II study assessed the rate of cardiotoxicity and efficacy of first-line PLD plus trastuzumab in HER-2-positive metastatic breast cancer (MBC). PATIENTS AND METHODS Women with HER-2-positive, measurable MBC, and a baseline left ventricular ejection fraction (LVEF) > or = 55% were treated with PLD 50 mg/m2 every 4 weeks for six cycles and weekly trastuzumab (4 mg/kg loading dose then 2 mg/kg thereafter). Cardiotoxicity was defined as symptomatic congestive heart failure (CHF) with > or = 10% decline in LVEF to below lower limits of normal, > or = 15% decline in LVEF without symptomatic CHF, or less than 10% LVEF decline to less than 45%. RESULTS Thirty women were enrolled, 13 had received prior adjuvant anthracyclines. A median 5.5 cycles of PLD were administered. Mean baseline LVEF was 62.8%, 59.5% after cycle four, and 58.3% after cycle six. Three patients (10%) developed protocol-defined cardiotoxicity. No patients developed symptomatic CHF. Response rate was 52%, with an additional 38% stable disease rate. At a median follow-up of 13.9 months, the median progression-free survival was 12.0 months; median overall survival has not yet been reached. The most common adverse events were grade 3 hand-foot syndrome (30%) and grade 3/4 neutropenia (27%). CONCLUSION The combination of PLD and trastuzumab is a well tolerated and active regimen in HER-2-positive MBC. Cardiotoxicity was observed, but limited to asymptomatic declines in LVEF. Further evaluation of this combination is warranted.

Fulvestrant 500 mg versus anastrozole 1 mg for hormone receptor-positive advanced breast cancer (FALCON): an international, randomised, double-blind, phase 3 trial

BACKGROUND Aromatase inhibitors are a standard of care for hormone receptor-positive locally advanced or metastatic breast cancer. We investigated whether the selective oestrogen receptor degrader fulvestrant could improve progression-free survival compared with anastrozole in postmenopausal patients who had not received previous endocrine therapy. METHODS In this phase 3, randomised, double-blind trial, we recruited eligible patients with histologically confirmed oestrogen receptor-positive or progesterone receptor-positive, or both, locally advanced or metastatic breast cancer from 113 academic hospitals and community centres in 20 countries. Eligible patients were endocrine therapy-naive, with WHO performance status 0-2, and at least one measurable or non-measurable lesion. Patients were randomly assigned (1:1) to fulvestrant (500 mg intramuscular injection; on days 0, 14, 28, then every 28 days thereafter) or anastrozole (1 mg orally daily) using a computer-generated randomisation scheme. The primary endpoint was progression-free survival, determined by Response Evaluation Criteria in Solid Tumors version 1·1, intervention by surgery or radiotherapy because of disease deterioration, or death from any cause, assessed in the intention-to-treat population. Safety outcomes were assessed in all patients who received at least one dose of randomised treatment (including placebo). This trial is registered with ClinicalTrials.gov, number NCT01602380. FINDINGS Between Oct 17, 2012, and July 11, 2014, 524 patients were enrolled to this study. Of these, 462 patients were randomised (230 to receive fulvestrant and 232 to receive anastrozole). Progression-free survival was significantly longer in the fulvestrant group than in the anastrozole group (hazard ratio [HR] 0·797, 95% CI 0·637-0·999, p=0·0486). Median progression-free survival was 16·6 months (95% CI 13·83-20·99) in the fulvestrant group versus 13·8 months (11·99-16·59) in the anastrozole group. The most common adverse events were arthralgia (38 [17%] in the fulvestrant group vs 24 [10%] in the anastrozole group) and hot flushes (26 [11%] in the fulvestrant group vs 24 [10%] in the anastrozole group). 16 (7%) of 228 patients in in the fulvestrant group and 11 (5%) of 232 patients in the anastrozole group discontinued because of adverse events. INTERPRETATION Fulvestrant has superior efficacy and is a preferred treatment option for patients with hormone receptor-positive locally advanced or metastatic breast cancer who have not received previous endocrine therapy compared with a third-generation aromatase inhibitor, a standard of care for first-line treatment of these patients. FUNDING AstraZeneca.

Xenografts of Human Hepatocellular Carcinoma: A Useful Model for Testing Drugs

Purpose: Our aims were to establish and characterize primary human hepatocellular carcinoma xenografts. They were used to screen new drugs and improve our current treatment regimens used in hepatocellular carcinoma. Experimental Design: Primary hepatocellular carcinomas were used to create the xenografts. Western blotting was used to determine the changes in proteins in these xenografts before and after therapies. Apoptotic and cell proliferation were analyzed by immunohistochemistry. Results: Seven lines of xenografts were established from primary human hepatocellular carcinomas. Lines 4-1318, 2-1318, 2006, and 26-1004 grew rapidly in severe combined immunodeficient (SCID) mice and doubled its volume every 48 to 72 hours. Series 5-1318 (5-1318, 30-1004, and 29-1104) grew relatively slowly in SCID mice and required ∼6 to 10 days to double its tumor volume. Western blot analysis revealed that the growth rate of these xenografts was associated with abnormal expression of proteins associated with the cell cycle, signaling pathways, and tumor suppressor genes. Although hepatocellular carcinoma xenografts expressed the receptors for androgens, estrogens, and progesterone, their growth rate was not affected by either castration or sex steroid hormone supplementation. Cisplatin, oxaliplatin, vitamin D analogue EB1089, and Iressa had no effects on the growth rate in SCID mice. Although 5-fluorouracil exerted mild growth inhibition of these xenografts, i.p. delivery of 2-chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU) or doxorubicin resulted in a significant growth inhibition. Doxorubicin-induced growth suppression was associated with elevation of p53 and p21Cip1/Waf1. In addition to up-regulation of p53 and p21Cip1/Waf1, SarCNU also increased the levels of phosphorylated cdc-2 at Tyr15. Conclusion: Hepatocellular carcinoma xenografts are powerful tools for screening drugs and SarCNU may be useful in the treatment of this fatal disease.

Small Molecules, Inhibitors of DNA-PK, Targeting DNA Repair, and Beyond.

Many current chemotherapies function by damaging genomic DNA in rapidly dividing cells ultimately leading to cell death. This therapeutic approach differentially targets cancer cells that generally display rapid cell division compared to normal tissue cells. However, although these treatments are initially effective in arresting tumor growth and reducing tumor burden, resistance and disease progression eventually occur. A major mechanism underlying this resistance is increased levels of cellular DNA repair. Most cells have complex mechanisms in place to repair DNA damage that occurs due to environmental exposures or normal metabolic processes. These systems, initially overwhelmed when faced with chemotherapy induced DNA damage, become more efficient under constant selective pressure and as a result chemotherapies become less effective. Thus, inhibiting DNA repair pathways using target specific small molecule inhibitors may overcome cellular resistance to DNA damaging chemotherapies. Non-homologous end joining a major mechanism for the repair of double-strand breaks (DSB) in DNA is regulated in part by the serine/threonine kinase, DNA dependent protein kinase (DNA-PK). The DNA-PK holoenzyme acts as a scaffold protein tethering broken DNA ends and recruiting other repair molecules. It also has enzymatic activity that may be involved in DNA damage signaling. Because of its’ central role in repair of DSBs, DNA-PK has been the focus of a number of small molecule studies. In these studies specific DNA-PK inhibitors have shown efficacy in synergizing chemotherapies in vitro. However, compounds currently known to specifically inhibit DNA-PK are limited by poor pharmacokinetics: these compounds have poor solubility and have high metabolic lability in vivo leading to short serum half-lives. Future improvement in DNA-PK inhibition will likely be achieved by designing new molecules based on the recently reported crystallographic structure of DNA-PK. Computer based drug design will not only assist in identifying novel functional moieties to replace the metabolically labile morpholino group but will also facilitate the design of molecules to target the DNA-PKcs/Ku80 interface or one of the autophosphorylation sites.

Phase II study of the progesterone antagonist mifepristone in patients with untreated metastatic breast carcinoma: a National Cancer Institute of Canada Clinical Trials Group study.

PURPOSE Mifepristone (RU486) is a progesterone receptor (PgR) antagonist that has been shown to be active in some preclinical hormone-dependent breast cancer tumor models and to produce a few responses in patients with pretreated metastatic disease in two small trials. This trial was designed to assess the response rate and toxic effects of mifepristone in a favorable group of women with PgR-positive recurrent breast cancer who had received no prior therapy. METHODS Postmenopausal patients with PgR-positive, bidimensionally measurable disease were eligible provided they had received no other therapy for recurrence. Prior adjuvant hormonal treatment was permitted if a disease-free interval of at least 24 months had been observed. Mifepristone 200 mg was given daily and disease was reassessed every 4 weeks. Standard criteria for tumor response and toxic effects were used. RESULTS A total of 28 patients were registered in the trial: all were eligible and assessable. Three partial responses were noted for an overall response rate of 10.7% (95% confidence interval [CI], 2% to 28%). Toxic effects were generally mild to moderate and consisted primarily of nausea, lethargy, anorexia, and hot flashes. CONCLUSION Mifepristone had minimal activity in this optimal group of patients. While there may be reason to conduct some clinical studies with it in combination with antiestrogens on the basis of some preclinical work, our data do not support its use as a single agent in the management of breast cancer.

Correlation of resistance to nitrogen mustards in chronic lymphocytic leukemia with enhanced removal of melphalan-induced DNA cross-links

To better define the kinetics of DNA interstrand cross-link formation and removal, we determined the percentage of DNA interstrand cross-links following 35 min incubation with 5 or 10 μm melphalan and a variable drug-free incubation period

A phase II trial of ZD1839 (Iressa™) 750 mg per day, an oral epidermal growth factor receptor-tyrosine kinase inhibitor, in patients with metastatic colorectal cancer

SummaryPurpose: The epidermal growth factor receptor (EGFR) appears relevant in the pathogenesis and progression of colorectal cancer. After completing a phase I pharmacodynamic trial of ZD1839, we undertook a dose expansion trial to examine the antitumour efficacy and adverse effect profile of this agent in a homogeneous group of patients with metastatic colorectal cancer (CRC). Experimental design: Eligible patients with metastatic or recurrent CRC received ZD1839 750 mg daily by mouth. This dose was selected based on a phase I trial conducted by the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG). Treatment was continued until unacceptable toxicity or disease progression. Results: Twenty-eight patients were enrolled at three NCIC CTG centers. Twenty-three patients had received prior chemotherapy; 12 patients had received three or more regimens. No objective responses were observed in 24 evaluable patients, although 8 patients had stable disease (median duration of 2.2 months). The most frequent drug related adverse events were diarrhea, rash and nausea. Eleven patients required dosing modification (hold or reduction), while 3 patients discontinued therapy because of toxicity. There were no treatment related deaths. Conclusions: ZD1839, when given at 750 mg/day to patients with pre-treated metastatic colorectal cancer, does not result in significant tumor regression.

Chlorambucil Cytotoxicity in Malignant B Lymphocytes Is Synergistically Increased by 2-(Morpholin-4-yl)-benzo[h]chomen-4-one (NU7026)-Mediated Inhibition of DNA Double-Strand Break Repair via Inhibition of DNA-Dependent Protein Kinase

Chlorambucil (CLB) treatment is used in chronic lymphocytic leukemia (CLL) but resistance to CLB develops in association with accelerated repair of CLB-induced DNA damage. Phosphorylated histone H2AX (γH2AX) is located at DNA double-strand break (DSB) sites; furthermore, it recruits and retains damage-responsive proteins. This damage can be repaired by nonhomologous DNA end-joining (NHEJ) and/or homologous recombinational repair (HR) pathways. A key component of NHEJ is the DNA-dependent protein kinase (DNA-PK) complex. Increased DNA-PK activity is associated with resistance to CLB in CLL. We used the specific DNA-PK inhibitor 2-(morpholin-4-yl)-benzo[h]chomen-4-one (NU7026) to sensitize CLL cells to chlorambucil. Our results indicate that in a CLL cell line (I83) and in primary CLL-lymphocytes, chlorambucil plus NU7026 has synergistic cytotoxic activity at nontoxic doses of NU7026. CLB treatment results in G2/M phase arrest, and NU7026 increases this CLB-induced G2/M arrest. Moreover, a kinetic time course demonstrates that CLB-induced DNA-PK activity was inhibited by NU7026, providing direct evidence of the ability of NU7026 to inhibit DNA-PK function. DSBs, visualized as γH2AX, were enhanced 24 to 48 h after CLB and further increased by CLB plus NU7026, suggesting that the synergy of the combination is mediated by NU7026 inhibition of DNA-PK with subsequent inhibition of DSB repair.

Homologous recombinational repair vis-à-vis chlorambucil resistance in chronic lymphocytic leukemia

The objective of this study was to further define the role of homologous recombinational repair (HRR) in resistance to the nitrogen mustards in B-cell chronic lymphocytic leukemia (B-CLL). We have demonstrated previously that increased chlorambucil (CLB)-induced HsRad51 nuclear foci formation correlated with a CLB-resistant phenotype in B-CLL lymphocytes. In this report, we measured the protein levels of HsRad51 and Xrcc3 (an HsRad51 paralog) and correlated them with the in vitro CLB cytotoxicity (LD(50)) in lymphocytes from seventeen B-CLL patients. Both HsRad51 (r=0.75, P=0.0005) and Xrcc3 (r=0.52, P=0.03) protein levels correlated with the in vitro CLB LD(50). In addition, multiple linear regression analysis showed a significant correlation between Xrcc3 and Rad51 protein levels versus the CLB LD(50) (r=0.78, P=0.0014), suggesting that both proteins influence CLB cytotoxicity. Moreover, since HsRad51 expression varies in cell lines during the cell cycle, we determined proliferating cell nuclear antigen (PCNA) protein levels to assess possible differences in cell cycle progression. There was no correlation between PCNA protein levels and the CLB LD(50) (r=0.042, P=0.87) or with HsRad51/Xrcc3 protein levels. Our data suggest that HsRad51 and Xrcc3 protein expression may be predictive of the response in B-CLL patients to treatment with nitrogen mustards.