David J. Waters

Overexpression of the EphA2 tyrosine kinase in prostate cancer

Molecules that are highly expressed by human prostate cancers may serve as therapeutically relevant targets or tumor markers. Tyrosine kinases are frequently overexpressed in metastatic tumor cells and this prompted us to screen for tyrosine kinases that are overexpressed in prostate cancer cells.

IMAGING OF SPONTANEOUS CANINE MAMMARY TUMORS USING FLUORESCENT CONTRAST AGENTS

Abstract— We present near‐infrared frequency‐domain photon migration imaging for the lifetime sensitive detection and localization of exogenous fluorescent contrast agents within tissue‐simulating phantoms and actual tissues. We employ intensity‐modulated excitation light that is expanded and delivered to the surface of a tissue or tissue‐simulating phantom. The intensity‐modulated fluorescence generated from within the volume propagates to the surface and is collected using a gain‐modulated image‐intensified charge‐coupled device camera. From the spatial values of modulation amplitude and phase of the detected fluorescent light, micromolar volumes of dieth‐ylthiatricarbocyanine iodide (π= 1.17 ns) and indocyanine green (ICG) (π= 0.58 ns) embedded 1.0 cm deep in a tissue phantom are localized and discriminated on the basis of their lifetime differences. To demonstrate the utility of frequency‐domain fluorescent measurements for imaging disease, we image the fluorescence emitted from the surface of in vivo and ex vivo canine mammary gland tissues containing lesions with preferential uptake of ICG. Pathology confirms the ability to detect spontaneous mammary tumors and regional lymph nodes amidst normal mammary tissue and fat as deep as 1.5 cm from the tissue surface.

Clinical and pathologic aspects of spontaneous canine prostate carcinoma: A retrospective analysis of 76 cases

Pet dogs and men share a vulnerability for the development of prostate carcinoma. The purpose of this study was to further characterize the clinical and pathologic features of spontaneous canine prostate carcinoma.

Preparation of 66Ga- and 68Ga-labeled Ga(III)-deferoxamine-folate as potential folate-receptor-targeted PET radiopharmaceuticals

A folate-receptor-targeting radiopharmaceutical, Ga(III)-deferoxamine-folate (Ga-DF-Folate), was radiolabeled with two positron-emitting isotopes of gallium, cyclotron-produced (66)Ga (9.5 hour half-life) and generator-produced (68)Ga (68 minute half-life). The [(66)Ga]Ga-DF-Folate was administered to athymic mice with folate-receptor-positive human KB cell tumor xenografts to demonstrate that microPET mouse tumor imaging is feasible with (66)Ga, despite the relatively high positron energy of this radionuclide. Using the athymic mouse KB tumor xenograft model, dual-isotope autoradiography was also performed following i.v. co-administration of [(18)F]-FDG, a marker of regional metabolic activity, and folate-receptor-targeted [(111)In]In-DTPA-Folate. The autoradiographic images of 1 mm tumor sections demonstrate the gross heterogeneity of the KB cell tumor xenograft, as well as subtle disparity in the regional accumulation of the two radiotracers.

Preoperative Prediction of Multifocal Prostate Cancer and Application of Focal Therapy: Review 2007

Prostate cancer is a leading malignancy among men. Early prostate cancer is most commonly treated with radical surgery and radiotherapy. In the era of prostate-specific antigen and newly emerging highly specific screening tests, a greater number of men are given a diagnosis earlier in life, and disease is more often confined. Less-invasive treatments, such as focal therapy, are becoming increasingly popular, yielding shorter hospital stays, faster recovery, and fewer complications. Potential drawbacks to focal therapy include the risk of incomplete treatment, which may result from missed cancer foci and inadequate ablation to target tissues. Furthermore, this approach is not universally applicable to all patients--for example, those who have periurethral and extraprostatic extension of the tumor may not benefit from focal treatment. This article reviews the importance of multifocal prostate cancer and the application of focal treatment.

Receptor-mediated targeting of 67Ga-Deferoxamine-Folate to folate-receptor-positive human kb tumor xenografts

The radiochemical synthesis and stability of 67Ga-deferoxamine-folate ([67Ga]Ga-DF-Folate) were examined as a function of DF-Folate concentration. Optimal labeling occurred at DF-Folate concentrations > or =2.5 microg/mL. To define the possible biological significance of variations in product formulation, the biodistribution of [67Ga]Ga-DF-Folate was examined as a function of administered deferoxamine-folate dose in an athymic mouse KB tumor model. The folate-receptor-positive KB tumors were found to concentrate the 67Ga radiolabel in a dose-dependent fashion, consistent with saturable involvement of the folate receptor in mediating tumor accumulation of the radiopharmaceutical.

Group Consensus Reports from the Consensus Conference on Focal Treatment of Prostatic Carcinoma, Celebration, Florida, February 24, 2006

( EPORT OF CONSENSUS GROUP 1: ATHOBIOLOGY OF PROSTATE CANCER: MPLICATIONS FOR FOCAL THERAPY ocal ablative therapy may be reasonable for some atients with prostate cancer; selection factors include variety of clinical and pathologic factors in combiation with informed patient choice. Our group evalated 4 specific pathologic features that may influence his treatment decision. We reviewed the published iterature for applicable studies regarding the natural istory of prostate cancer, multifocality, cancer volme, and accuracy of cancer detection by current ethods. Results were as follows:

Cyclooxygenase inhibitors in urinary bladder cancer: in vitro and in vivo effects

More than 14,000 people die from invasive transitional cell carcinoma (TCC) of the urinary bladder yearly in the United States. Cyclooxygenase (COX)-inhibiting drugs are emerging as potential antitumor agents in TCC. The optimal in vitro or in vivo systems to investigate COX inhibitor antitumor effects have not been defined. The purpose of this study was to determine COX-1 and COX-2 expression and antitumor effects of COX inhibitors in human TCC cell lines (HT1376, RT4, and UMUC3 cells) and xenografts derived from those cell lines. COX-2 expression (Western blot, immunocytochemistry) was high in HT1376, modest in RT4, and absent in UMUC3 cells in vitro. Similarly, COX-2 expression was noted in RT4 but not UMUC3 xenografts. COX-2 expression in HT1376 xenografts was slightly lower than that observed in vitro. None of four COX inhibitors evaluated (celecoxib, piroxicam, valeryl salicylate, and NS398) reduced TCC growth in standard in vitro proliferation assays at concentrations that could be safely achieved in vivo (≤5 μmol/L). Higher celecoxib concentrations (≥50 μmol/L) inhibited proliferation and induced apoptosis in all three cell lines. Celecoxib or piroxicam treatment in athymic mice significantly delayed progression of HT1376 xenografts, which express COX-2, but not UMUC3 xenografts that lack COX-2 expression. In conclusion, standard in vitro assays were not useful in predicting COX inhibitor antitumor effects observed in vivo. Athymic mice bearing TCC xenografts provide a useful in vivo system for COX inhibitor studies. Results of this study provide justification for further evaluation of COX inhibitors as antitumor agents against TCC. [Mol Cancer Ther 2006;5(2):329–36]

Prostatic intraepithelial neoplasia occurs spontaneously in the canine prostate

PURPOSE Prostatic intraepithelial neoplasia (PIN) is the most likely precursor of human prostate cancer. Although the dog is the only non-human species in which spontaneous prostate cancer occurs frequently, the prevalence of PIN in the canine prostate is unknown. A naturally occurring animal model of PIN has not been described. MATERIALS AND METHODS To determine if high grade PIN occurs spontaneously in the canine prostate, we evaluated totally embedded prostates from 35 outbred dogs that had no clinical evidence of prostatic disease. Prostates from three groups of dogs were analyzed: (1) 11 sexually intact dogs 7-17 years old (elderly sexually intact); (2) 13 sexually intact dogs 1-4 years old (young sexually intact); and (3) 11 dogs 7-17 years old that had been castrated (elderly castrated). The prevalence of PIN was determined by systematic evaluation of hematoxylin/eosin and high molecular weight keratin 34 beta-E12 stained tissue sections from formalin-fixed, paraffin embedded prostates that had been serially sectioned at 4 mm intervals. RESULTS Canine high grade PIN showed cytologic features identical to the human counterpart, including cell crowding, loss of polarity, and nuclear and nucleolar enlargement. Foci of high grade PIN were present in the prostates of 6 of 11 (55%) elderly, sexually intact dogs but only 1 of 13 (8%) dogs less than 4 years old. Foci of high grade PIN were detected in 1 of 11 (9%) elderly castrated dogs. In elderly, sexually intact dogs with PIN, foci of high grade PIN were present in 13 of 83 (16%) tissue sections evaluated; one of these dogs had focal adenocarcinoma in addition to PIN. CONCLUSIONS These results indicate that high grade PIN is frequently present in the prostate of elderly, sexually intact dogs. The prevalence of canine PIN, like human PIN, is apparently influenced by age and testicular androgens. The canine prostate may serve as a useful model to determine the factors that regulate the apparent progression from benign epithelium to PIN and invasive carcinoma.

Defining the Optimal Selenium Dose for Prostate Cancer Risk Reduction: Insights from the U-Shaped Relationship between Selenium Status, DNA Damage, and Apoptosis

Our work in dogs has revealed a U-shaped dose response between selenium status and prostatic DNA damage that remarkably parallels the relationship between dietary selenium and prostate cancer risk in men, suggesting that more selenium is not necessarily better. Herein, we extend this canine work to show that the selenium dose that minimizes prostatic DNA damage also maximizes apoptosis—a cancer-suppressing death switch used by prostatic epithelial cells. These provocative findings suggest a new line of thinking about how selenium can reduce cancer risk. Mid-range selenium status (.67–.92 ppm in toenails) favors a process we call “homeostatic housecleaning”—an upregulated apoptosis that preferentially purges damaged prostatic cells. Also, the U-shaped relationship provides valuable insight into stratifying individuals as selenium-responsive or selenium-refractory, based upon the likelihood of reducing their cancer risk by additional selenium. By studying elderly dogs, the only non-human animal model of spontaneous prostate cancer, we have established a robust experimental approach bridging the gap between laboratory and human studies that can help to define the optimal doses of cancer preventives for large-scale human trials. Moreover, our observations bring much needed clarity to the null results of the Selenium and Vitamin E Cancer Prevention Trial (SELECT) and set a new research priority: testing whether men with low, suboptimal selenium levels less than 0.8 ppm in toenails can achieve cancer risk reduction through daily supplementation.