John Thoms

β1-Integrin Circumvents the Antiproliferative Effects of Trastuzumab in Human Epidermal Growth Factor Receptor-2–Positive Breast Cancer

Resistance to trastuzumab, the monoclonal antibody targeting human epidermal growth factor receptor 2 (HER-2), is a major concern for HER-2-positive metastatic breast cancer (MBC) patients. To date, HER-2 status is the only available biomarker for selecting patients for trastuzumab-based therapy. Beta(1)-integrin, an adhesion molecule involved in cell survival and drug resistance, shares common downstream signaling elements with HER-2, such as the phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase-1/2 (ERK1/2) pathways. The significance of beta(1)-integrin expression in HER-2-positive breast cancer and its involvement in a patients response to trastuzumab-based therapy are unknown. We show here that overexpression of beta(1)-integrin is an independent negative prognostic factor for tumor progression of HER-2-positive MBC patients treated with trastuzumab-based chemotherapy. Enforced overexpression of beta(1)-integrin, its small interfering RNA-induced knockdown or treatment with a beta(1)-integrin-blocking antibody in HER-2-positive breast cancer cells, identified a strong inverse relationship between expression level of beta(1)-integrin and in vitro sensitivity to trastuzumab. Notably, beta(1)-integrin overexpression increased the phosphorylation of Akt-Ser473 and ERK1/2, thereby promoting survival and mitogenic signals to bypass the antiproliferative effects of trastuzumab. Our findings show that beta(1)-integrin provides a novel independent prognostic biomarker of trastuzumab response in HER-2-positive MBC patients and suggest a new target to augment the antiproliferative effects of trastuzumab.

Array CGH as a potential predictor of radiocurability in intermediate risk prostate cancer

Abstract Prostate cancer is the most common male cancer and up to one fifth of diagnosed patients will die of their disease. Current prognostic variables including T-category (of the TNM staging), the absolute or kinetics of prostatic specific antigen (PSA) and the pathologic Gleason score (GS) are utilized to place men in low, intermediate and high-risk prostate cancer risk groupings. There is great heterogeneity within the non-indolent intermediate risk group with respect to clinical response. It is therefore imperative that further genetic and other prognostic factors be identified to better individualize treatment. Somatic alterations in prostate cancer. Herein, we review the potential for somatic alterations in tumor-associated genes (based on comparative genomic hybridization (CGH) in prostate cancers to be novel prognostic, and possibly predictive, factors for prostate cancer radiotherapy response. Intermediate risk prostate cancers show alterations in a number of genes thought to be involved in radiosensitivity, DNA repair, cell death and stem cell renewal. These include deletions at 21q (TMPRSS2: ERG), 13q (RB1), 10q (PTEN), 8p (NKX3.1), additions at 8q21 (containing c-Myc)) and haplo-insufficiency for p53, PARP1, ATM and DNA-PKcs. Conclusions. The use of high-resolution CGH for fine-mapping of deletions and amplifications in pre-radiotherapy prostate cancer biopsies is feasible. Genetic alterations may delineate localized prostate cancer from systemic disease and be used as a predictive factor in that patients would be individually triaged to local (surgery versus radiotherapy) and/or adjuvant (adjuvant androgen ablation or post-operative radiotherapy) therapies in a prospective fashion to improve outcome. The knowledge of abnormal DNA repair pathways within in a given patient could allow for the judicious use of targeted agents (PARP/ATM inhibitors) as personalized medicine.

Plasma osteopontin as a biomarker of prostate cancer aggression: relationship to risk category and treatment response

Background:High plasma osteopontin (OPN) has been linked to tumour hypoxia, metastasis, and poor prognosis. This study aims to assess whether plasma osteopontin was a biomarker of increasing progression within prostate cancer (PCa) prognostic groups and whether it reflected treatment response to local and systemic therapies.Methods:Baseline OPN was determined in men with localised (n=199), locally recurrent (n=9) and castrate-resistant, metastatic PCa (CRPC-MET; n=37). Receiver-operating curves (ROC) were generated to describe the accuracy of OPN for distinguishing between localised risk groups or localised vs metastatic disease. We also measured OPN pre- and posttreatment, following radical prostatectomy, external beam radiotherapy (EBRT), androgen deprivation (AD) or taxane-based chemotherapy.Results:The CRPC-MET patients had increased baseline values (mean 219; 56–513u2009ngu2009ml−1; P<0.0001) compared with the localised, non-metastatic group (mean 72; 12–438u2009ngu2009ml−1). The area under the ROC to differentiate localised vs metastatic disease was improved when OPN was added to prostate-specific antigen (PSA) (0.943–0.969). Osteopontin neither distinguished high-risk PCa from other localised PCa nor correlated with serum PSA at baseline. Osteopontin levels reduced in low-risk patients after radical prostatectomy (P=0.005) and in CRPC-MET patients after chemotherapy (P=0.027), but not after EBRT or AD.Conclusion:Plasma OPN is as good as PSA at predicting treatment response in CRPC-MET patients after chemotherapy. Our data do not support the use of plasma OPN as a biomarker of increasing tumour burden within localised PCa.

Hypoxia disrupts the Fanconi anemia pathway and sensitizes cells to chemotherapy through regulation of UBE2T

BACKGROUND AND PURPOSEnHypoxia is a common feature of the microenvironment of solid tumors which has been shown to promote malignancy and poor patient outcome through multiple mechanisms. The association of hypoxia with more aggressive disease may be due in part to recently identified links between hypoxia and genetic instability. For example, hypoxia has been demonstrated to impede DNA repair by down-regulating the homologous recombination protein RAD51. Here we investigated hypoxic regulation of UBE2T, a ubiquitin ligase required in the Fanconi anemia (FA) DNA repair pathway.nnnMATERIALS AND METHODSnWe analysed UBE2T expression by microarray, quantitative PCR and western blot analysis in a panel of cancer cell lines as a function of oxygen concentration. The importance of this regulation was assessed by measuring cell survival in response to DNA damaging agents under normoxia or hypoxia. Finally, HIF dependency was determined using knockdown cell lines and RCC4 cells which constitutively express HIF1α.nnnRESULTSnHypoxia results in rapid and potent reductions in mRNA levels of UBE2T in a panel of cancer cell lines. Reduced UBE2T mRNA expression is HIF independent and was not due to changes in mRNA or protein stability, but rather reflected reduced promoter activity. Exposure of tumor cells to hypoxia greatly increased their sensitivity to treatment with the interstrand crosslinking (ICL) agent mitomycin C.nnnCONCLUSIONSnExposure to hypoxic conditions down-regulates UBE2T expression which correlates with an increased sensitivity to crosslinking agents consistent with a defective Fanconi anemia pathway. This pathway can potentially be exploited to target hypoxic cells in tumors.

Human tissue Kallikreins: Blood levels and response to radiotherapy in intermediate risk prostate cancer

OBJECTIVESnKallikreins are serine proteases over expressed in many malignancies. In this study, we measure changes in serum kallikrein (KLKs) levels during intensity-modulated radiotherapy (IMRT) in prostate cancer patients, and find potential correlations between serum kallikrein level and normal tissues toxicity during radiation.nnnMETHODSnForty-nine patients with prostate cancer were recruited as follows: group 1, definitive standard fractionation IMRT (78Gy in 39 fractions, n=15); group 2, definitive hypofractionated IMRT (60Gy in 20 fractions, n=15); and group 3, IMRT postprostatectomy (66Gy in 33 fractions, n=19). Patients treated with definitive radiation therapy were intermediate risk. Blood samples were collected at baseline and quarterly during IMRT and at each follow-up visit. Acute toxicity was graded weekly during radiotherapy using CTC-AE v4.0 criteria. Multiplexed immunoassays were used to quantify total, free, and intact Prostate Specific Antigen (PSA), as well as Kallikreins 2, 4, 6, and 11.nnnRESULTSnThe serum kallikreins, PSA (total, free and intact), KLK2, 6, and 11 change significantly after definitive radiotherapy. KLK2 and intact PSA decrease as fast as two weeks after initiation of radiation, while the first significant decrease in total and free PSA is noted only at the completion of radiation. KLK6 and KLK11 surge temporarily during radiation therapy and decrease below baseline levels at 8weeks and 12months, respectively after completion of radiation. KLK4 levels did not change with radiation. There was no correlation between GU or GI toxicities and serum kallikreins.nnnCONCLUSIONSnPSA, KLK2, 6, and 11, change significantly after definitive prostate radiotherapy, though KLK2 and PSA decrease by the end of the radiation course while KLK6 and KLK11 decrease significantly starting at 2 and 12months, respectively, after radiation. There was no correlation between GU or GI toxicities and serum kallikreins.

Abstract 2136: Combined 8q gain and 10q loss predicts for relapse following radical radiotherapy in intermediate risk prostate cancer

Introduction: Gains on 8q with amplification of c-MYC and loss of 10q and PTEN have been associated with aggression in a number of cancers, including prostate cancer. Pre-clinical studies support that altered PTEN and c-MYC expression can alter cellular radiosensitivity. A definitive study of genetic loci containing PTEN deletions and c-Myc as potential predictors of relapse following radiotherapy has not been reported. We hypothesized that increased radiotherapy relapse was associated with 10q deletion and 8q gain (associated with loss of PTEN and amplification of c-MYC). Methods Biopsies were derived from 115 men with intermediate risk prostate cancer (T1-T2 disease and a Gleason score 7 and PSA less than 20 ng/ml, or a Gleason score less than 7 and PSA between 10 and 20 ng/ml). We used high-resolution array comparative genomic hybridization (arrayCGH) to identify copy number alterations (CNAs) in intermediate risk prostate cancer patients treated with 75.6 or 79.8 Gy of conformal radiotherapy. Biochemical failure, defined by Phoenix criteria or the initiation of salvage therapy, was observed in 35 patients after median follow-up of 5.4 years (range 0.9-8.8). Results: In our cohort, the percentage of a patient9s genome which is altered (PGA) ranges from Conclusions: This is the first report of altered loci pertaining to the PTEN and c-MYC genes as determinants of radiotherapy outcome in intermediate risk prostate cancer. Future goals are directed towards using all aCGH hits and FISH validation to stratify the same patients into responders and non-responders. If validated in other radical radiotherapy series, PTEN-cMYC status could be used to individualize patient therapy for localized prostate cancer. (Supported by grants from CCSRI, the Terry Fox Foundation, PCC and CFI). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2136.